# Zoom climb



## grampi (Jun 17, 2015)

Considering that zoom climb was a performance characteristic that one would think would have been a very important aspect in the air to air combat environment of WWII, one would also think that this performance aspect would have been measured, charted, and recorded to death. Is there any such data listed for the fighter aircraft of that era? I've never seen any...and which aircraft would you think would be the best at this?


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## Greyman (Jun 17, 2015)

There are a lot of variables when trying to compare this so I imagine there would be difficulty coming up with a standard.

- do you zoom from maximum speed or a standard speed?
- do you zoom from a dive?
- at what speed do you enter the dive?
- how fast do you manoeuvre into the dive?
- what angle of dive?
- how long do you dive?
- what altitude do you pull out?
- what speed do you pull out?
- how hard is the pull out?
- what angle of zoom climb?

Different aircraft are going to compare differently amongst each other depending on how these questions (and other ones I didn't think of) are answered.

Add in different engine settings and different altitudes to all of this and you've got some headaches if you're going to do some precise measurements.


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## Shortround6 (Jun 17, 2015)

In a zoom climb you are basically trading kinetic energy for altitude. AS the kinetic energy bleeds off the plane reverts back to "normal" climb. 

Kinetic energy is a function of speed (squared) and weight. The faster a given plane is going when it starts it's zoom climb the better it will do. 

Fighting the climb are the usual two problems. Gravity and drag. Drag also varies with speed and it also varies with altitude. You roughly have about 2% less drag per 1000ft of altitude. 

You have several variables that make getting actual measurements difficult but general trends are easy. Heavy, fast fighters (low drag) will zoom climb better than light slow fighters. Heavy fighters that are going slow won't zoom climb well. 

Fighter doing 300mph has 2.25 the energy of a fighter doing 200mph. a fighter doing 350hp has 36% more energy than one doing 300mph. This is assuming the planes all weigh the same or if you prefer that is the difference in energy per pound (or KG ) or aircraft weight. One reason for P-40s to stay out of turning fights. If you bleed off your speed you loose the zoom climb option.

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## GregP (Jun 17, 2015)

That being said, and I have to agree with almost all of it, some fighters were known to be particularly good in a zoom climb ... the P-51, Sea Fury, and Tigercat being three of them. It is probably a function of all the variables mentioned above, but this group holds energy very well at medium speeds and above if you climb at relatively high power.

In most airshow acts nobody is flying at WER or even at maximum rated power, but the P-51, Sea Fury, and Tiugercat all seem to have no trouble doing a big 4,000+ foot loop and coming over the top with energy to spare. Some of the other fighters I have seen do a smaller loop (maybe 3,000 - 3,500 feet) and look pretty slow over the top ... but, and here's the rub, that could simply be a function of which pilot is willing to carry more power through the loop.

Your observation about zoom being an important characteristic is correct, but I have never seen a mesurment of it in comparative data versus other fighters of the same era.

It would be nice to get that list, but the owners of warbirds today probably will never agree on how much power is agreeable to them to carry through testing. After all, THEY are paying for the engines and fuel. I know guys who never operate at more than 900 HP for their Merlin and I know guys who will take it out to 1,300 HP on a semi-regular basis.

Here is a classic example of a Bell P-63.


_View: https://www.youtube.com/watch?v=_jSHZPmiSPk_

There is nothing whatsoever wrong with the P-63 and it has PLENTY of power. But the pilot flying this aircraft was very probably carrying less than 40" of manifold pressure the whole time and wasn't going very fast to start with. That according to people who build and fly Allisons. You cn see that the P-63 never even gets over the top of the loop, but rather stalls and enters a spin. Had he been carrying 55" - 57" of MAP, he could have done a loop of twice the diameter and would have gone over the top with plenty of energy to spare.


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## davebender (Jun 17, 2015)

Dive followed by zoom climb was Erich Hartmann's favorite tactic. So I've got to assume Me-109G was good at this particular maneuver.

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## Greyman (Jun 17, 2015)

I don't think it's so much the the 109 is an outstanding zoom-climber, more of the fact that 'boom and zoom' tactics are what you want to employ when you have an interest in surviving 1000+ combat missions.


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## grampi (Jun 17, 2015)

GregP said:


> That being said, and I have to agree with almost all of it, some fighters were known to be particularly good in a zoom climb ... the P-51, Sea Fury, and Tigercat being three of them. It is probably a function of all the variables mentioned above, but this group holds energy very well at medium speeds and above if you climb at relatively high power.
> 
> In most airshow acts nobody is flying at WER or even at maximum rated power, but the P-51, Sea Fury, and Tiugercat all seem to have no trouble doing a big 4,000+ foot loop and coming over the top with energy to spare. Some of the other fighters I have seen do a smaller loop (maybe 3,000 - 3,500 feet) and look pretty slow over the top ... but, and here's the rub, that could simply be a function of which pilot is willing to carry more power through the loop.
> 
> ...




I think a good comparison is a P-51 vs an F8F...the Bearcat will absolutely kill a Mustang in climb race from a dead stop, but in a zoom climb, the Mustang may actually have the advantage...this is evident when watching the two planes perform aerobatics during air shows...like you said, once the Mustang gets its air speed up, it has no problem doing the very large loops...using it's speed, energy, and clean aerodynamics to achieve a very good zoom climb...


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## Mike Williams (Jun 17, 2015)

grampi said:


> Considering that zoom climb was a performance characteristic that one would think would have been a very important aspect in the air to air combat environment of WWII, one would also think that this performance aspect would have been measured, charted, and recorded to death. Is there any such data listed for the fighter aircraft of that era? I've never seen any...and which aircraft would you think would be the best at this?



Zoom Characteristics of P-47N-2 airplane AAF No. 44-87785 Report No. TSCEP5E-1892 comes to mind. Also a lot of AFDU Tactical Trials report on comparative zoom climb of the aircraft tested, for example see Tactical Trials of the Tempest V.


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## GregP (Jun 17, 2015)

Yes Grampi,

The F8F will easily out-climb and out-accelerate the P-51. The advantage in a Zoom climb would probably go to whichever aircraft is going faster at the time. Most of the time the F8F, particularly at airshows, is not flying as fast as the P-51 since it doesn't have to and the climb rate is already so good.

Typically a Bearcat, even in patrol in the WWII timeframe, would be cruising at about 185 mph or so while the P-51 would be cruising about 250 - 280 mph or so. At airshows, most F8F pilots try to have at least best rate of climb aispeed before doing any vertical maneuvers, but are not usually quite as fast as a P-51 doing the same maneuver ... due to fuel burn, not to lack of any ability to be at the same speed. I've seen ONE demosntration when the Bearcat was using some power and he was every bit as fast either P-51 he was chasing.

That was in Arizona some 25 years ago when one of the local pilots had just bought an F8F. We were riding dirt bikes under the airspace he was using and I stopped to watch a 25-minute chase-dogfight. I had my pilot's license at the time and was very interested in warbirds, so you can imagine my delight when an F8F, 2 P-51's, and a Spirfire all showed up in the same airspace and were doing some impromptu dogfighting and general fighter maneuvers.

I believe the Spitfire was Woody Woods out of Cave Creek and one of the P-51's was Bill Hane out of Falcon Field in Mesa. I can't recall the F8F's owner just now, but I was told some time later that it had a laet-model engine and was occasionally flown at full power just for fun. I had never seen the other P-51 but is was a pretty as the rest are. It was probably painted since it looked very good but we didn't get the usual sun-glint we saw from polished Aliuminum planes. There are quite a few of those in Arizona, as you might expect.

There were warbirds all around Arizona. Thunderbird Aviation also operated a couiple of F-104's, three A-3 Skywarriors, and some nicely-painted T-33's from Deer Valley. I got to see the energency checklist in one of the F-104's one day. About 65% or so, give or take a bit, of the energencies ended in ... EJECT. 

Doesn't seem like a good aircraft in which to have an emergency ...


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## Conslaw (Jun 19, 2015)

One of the keys to the success of the P-51 was its fast cruising speed. At altitude it could cruise over 380 MPH, faster than the top speed of most Japanese fighters and close to the top speed of the German fighters without their water injection. At that air speed, the P-51 already had enough energy for a pretty nice zoom climb, so even though on paper the FW-190 and the Bf109 were faster climbers, when starting from lower speeds and/or an altitude disadvantage, the P-51 wasn't necessarily at a climbing disadvantage compared with these German fighters.


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## GregP (Jun 19, 2015)

There is no P-51 that cruises at 380 mph. Any standard P-51 D / K pilot manual will tell you that.

Let's pick a weight of 9,600 to 10,800 pounds with two 75-gallon wing tanks ... typical. Max cruise was 42" and 2,400 rpm, give or take a bit. Let's say we fudge it just a bit and choose to cruise at 43" and 2,450 rpm. TAS is 340 mph.

A MUCH more likely cruise is below 42" and 2,400 rpm.

OK, choose 41" and 2,250 rpm at 69 GPH and, right off the chart, the TAS is 280 mph, right where you'd expect it to be if you were in the cockpit. You weren't going to get anywhere near 380 mph in any cruise condition.

You CAN get there, but only at elevated power levels consisent with combat and dropped tanks.


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## grampi (Jun 22, 2015)

GregP said:


> There is no P-51 that cruises at 380 mph. Any standard P-51 D / K pilot manual will tell you that.
> 
> Let's pick a weight of 9,600 to 10,800 pounds with two 75-gallon wing tanks ... typical. Max cruise was 42" and 2,400 rpm, give or take a bit. Let's say we fudge it just a bit and choose to cruise at 43" and 2,450 rpm. TAS is 340 mph.
> 
> ...



I don't know about that Greg...we had a guy who owned a blue nose P-51 who kept his plane here at the Louis University Airport right next to my office (his first name was Vlad, don't remember his last name), and he said his cruise speed was right around 375-380...he had no reason to lie to me so I assumed this was accurate...


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## Greyman (Jun 22, 2015)

British Data Sheets over at P-51 Mustang Performance give:

*Mustang III (V-1650-3)*
most economical: 253 mph
max weak mixture: 395 mph

*Mustang III (V-1650-7)*
most economical: 253 mph
max weak mixture: 405 mph

*Mustang IV (V-1650-7)*
most economical: 253 mph
max weak mixture: 400 mph


at 20,000.


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## Shortround6 (Jun 22, 2015)

Post war manual for a 51-D says it will do 379mph at 25,000 with a pair of 75 gallon tanks using max continuous power. Any owner using such power settings now is both rich and has a stock of spare parts. Not to mention cruising at 25,000ft may violate FAA rules.
Cruising at that speed cut range and made keeping station with the bombers much harder. It _might_ have been used at times ( near known Luftwaffe air fields?) But not as a general practice. Bomber escort would have been flown at 300-325mph as a compromise between range/endurance and ability to respond/accelerate/climb.


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## grampi (Jun 22, 2015)

Shortround6 said:


> Post war manual for a 51-D says it will do 379mph at 25,000 with a pair of 75 gallon tanks using max continuous power. Any owner using such power settings now is both rich and has a stock of spare parts. Not to mention cruising at 25,000ft may violate FAA rules.
> Cruising at that speed cut range and made keeping station with the bombers much harder. It _might_ have been used at times ( near known Luftwaffe air fields?) But not as a general practice. Bomber escort would have been flown at 300-325mph as a compromise between range/endurance and ability to respond/accelerate/climb.



When you say "a pair of 75 gal tanks" I assume you mean drop tanks, correct? I know this guy (Vlad the P-51 owner/pilot) I talked to doesn't use drop tanks, which would create quite a bit of drag, which may be part of it...the other part of it is he may have some work done to the motor that makes it more powerful than a stock engine, and maybe he's willing to run it a little harder...who knows...all I know is he told me his cruise speed is around 375-380 and he has no reason to lie or BS me...why would I not believe someone who has owned and flown a P-51 for years? Also, why would a post war P-51 be slower than a wartime version? Didn't the wartime version have a top speed of 437 MPH?


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## Shortround6 (Jun 22, 2015)

Yes, that was with drop tanks. 

Zeno's warbirds has a page from a manual without load but with racks installed.







Flying clean there are number of combinations of altitude and rpm/boost that could give 380mph _without_ using max continuous (2700rpm and 46in/6.5-7lbs boost).

I would guess your your friend was also running a bit light, no ammo, probably no guns, Armor? self-sealing tanks? Most planes flying in the last 20 years (if not 60 years) have had the self-sealing taken out as it deteriorates and tends to clog fuel lines. 

never said your friend was lying, he is just operating under different conditions than the war time planes. 

I said post war manual because it is, and what the Air Force allowed/recommended in peace time may NOT be what they allowed in war time, or it may be. Original question was about 380mph cruise over Europe during the war. I would be hesitant to quote a post war manual as gospel as to what they were doing during the war, that's all.

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## pbehn (Jun 22, 2015)

Surely zoom climb is just a function of low drag excess power and generating lift without drag? Boom and zoom requires high dive speed coupled with the aforementioned. 

Discussion of kinetic energy is interesting because the kinetic energy increases with weight but that weight has to be lifted i.e. converted from kinetic to potential energy. The two most important factors to me are power available and drag resistance.


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## GregP (Jun 22, 2015)

We fly stock P-51s almost every week and there aren't any that cruise that fast. 

If someone says they do, that only reveals their lack of knowledge of the aircraft.

I'm not alking about a P-51 with no gind, cleaned up, no armor, and brethed=on engine, and a profiled wing ... I'm takning about a stock P-51D/K with wings rack andf probably drop tanks, running a stock wartime Merlin with a sltock wartime propeller.

Max continuouis is 42"and 2,400 rpm ... and that will NOT gte you to 380 mph, IAS or TAS. If it does, something is VERY MUCH not stock, and I'd vore first for an incorrect power setting for max range.

You can get almost any P-51D/K to 380 mph TAS, but you can't run it that hard from London to Berlin and back. C'mon huys, this ain't a flight sim I'm talking about, it's a real WWII escort mission, flown in formation, tracking the bombers all the way there and back, iwht possibly a few minutes of conbat thrown in. And if you DO get into combat, you still want to get home on that same flight in the same airplane with some of teh same gasoline left in the tanks when you get there.


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## pbehn (Jun 22, 2015)

GregP said:


> You can get almost any P-51D/K to 380 mph TAS, but you can't run it that hard from London to Berlin and back. C'mon huys, this ain't a flight sim I'm talking about, it's a real WWII escort mission, flown in formation, tracking the bombers all the way there and back, iwht possibly a few minutes of conbat thrown in. And if you DO get into combat, you still want to get home on that same flight in the same airplane with some of teh same gasoline left in the tanks when you get there.



I thought the whole thing behind the P51 was an extremely slippery frame with a modern (at the time) supercharged engine. The P51 cold chug chug at its most economical speed for hours then wind up the boost for the short time combat was needed. I know its a simplification because P51s cruised to a rendezvous then escorted/fought then cruised back home.


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## kool kitty89 (Jun 22, 2015)

pbehn said:


> I thought the whole thing behind the P51 was an extremely slippery frame with a modern (at the time) supercharged engine. The P51 cold chug chug at its most economical speed for hours then wind up the boost for the short time combat was needed. I know its a simplification because P51s cruised to a rendezvous then escorted/fought then cruised back home.


Cruising at 380 MPH (even at best altitude for that speed) wouldn't give you the range to make it to Berlin and back, let alone enough reserve for combat and loiter time for landing.

The closest to that you'd probably get would be with aircraft cruising home after dropping tanks (and possibly expending ammunition). That or possible pushing into fast-cruise after dropping tanks while over the target area when most aggressively patrolling for interceptors.

Also remember for any sort of top cover (not roaming fighter sweeps) for slow cruising heavy bombers, you'd need to be weaving and circling over the bomber formation and the faster you cruise, the more fuel you waste flying in circles.


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## BiffF15 (Jun 22, 2015)

Gents,

I asked a friend who flies Mustangs what they use for cruise and this is what he replied: "Cruise power (that we use) is 37" manifold pressure and 2300 engine RPM (prop RPM appx 1/2 of engine). Fuel flow is around 60 GPH. At 10k' Cruise KIAS appx 215".

As for Vlad and Moonbeam McSwine (I think that's his plane), could he get that speed at high cruise. No tanks or racks, no armor, guns, military equipment? 

Cheers,
Biff


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## GregP (Jun 22, 2015)

The P-51 had one of the lowest coefficients of drag of any WWII fighter, true. If I am not listaken, it actually had the lowest drag of ANY WWII piston fighter. But a stock P-51D, in factory-new finish, with a brand-bew Merlin, freshly broken in, and having not sat outside in the weather for days, weeks, or months ... could make a top speed of 437 mph clean (no racks or tanks) at the FTH of somehwere between 17,500 feet and 25,000 feet depending on Merlin dash number. That was at the maximum approved manifold pressure and 3,000 rpm.

Down low, they could hit about 360 mph at sea level.

The 437 mph was the maximum speed and that happened at only ONE altitude ... it was slower everywhere else, no matter what power was being used. The same can be said for any fighter using a 2-stage, supercharged engine. The top speed achieved was acheived at only one altitude.

Most Merlins used on the P-51D/H were approved for 61" of MAP at 3,000 rpm, where they made 1,490 HP at 61" and about 1,710 HP at 67" WER. The so-called "top speed" was at WER that was NOT approved for use excpet in combat for a maximum of 5 minutes or so. Of course, in combat, you do whatever is necessary, power-wise, to survive, but WER was NEVER going to be used for very long or you would be flying a glider soon and if you DID make it back, your crew chief was going to change the engine.

Maximum continuous cruise power was about 42" at 2,400 rpm. A MUCH more usual max cruise was at 40 - 41" at 2,100 - 2,200 rpm, and that didn't give you more than about 310 - 320 mph at ANY altitude and still doesn't today. Civil P-51's today are limited to 250 knots below 10,000 feet, but private owners don't usually cruise faster than about 235 knots because a moment's inattention in pitch will exceed the speed limit. Also, THEY are paying for the very expensive Merlin overhaul when the time comes, not Uncle Sam.

Usual wartime cruise was about 280 - 320 mph when flying fighter missions and 250 - 280 mph when flying escort missions. Naturally, they'd go a slower over the UK for economy and would accelerate to 280 - 300 mph when they got close to where enemy fighters were expected to be encountered. Expecting conbat is one reason to speed up a bit.

None or almost none were going 380 mph if enemy fighters were not in sight and being called out on the radio for all to see and hear. There was no point in pushing your Merlin when you were 500 - 600 miles from home if you weren't in a situation that called for it. Now, wheh combat was imminent, if you pushed over at a decent power level into a shallow or steeper five, you would blast through 380 mph in a blink ... but you also weren't cruising around over the bombers when you did ... you were attacking or maneuvering to set up an attack. 

Otherwise you would not be diving away from escort altltude for kicks unless you were assigned to drop below a could deck and look for enemy fighters. If you WERE assigned that task, you could throttle up a bit, lower the nose, dive and look about, and go back up, using the speed you still had from the dive to trade for altitude back up to cruising altitude. If you did, you would immediately go back to cruise power.

Getting home was a BIG priority and wasting fuel was frowned upon by EVERYONE, especially your flight, squadron, or wing leader, and could get you abused by the wingmen who had to follow you if the extra fuel use wasn't justified in any way. They wanted to get home, too.

It should NOT be taken that this was an ironclad rule ... it was the norm for most pilots who understood engines and airplanes. There were certainly cases of cruising at high speed, but there was also a good reason to do so when it was done. One reason might be to pass by a known flak site with known-good gunners or a known airfield where the "Experten" were based and expected to contest your passing.

Nobody attacked the ground or water from cruise speed. They were all going fast to minimze the time they were in flak range, and they probably weren't flying straight unless they were shooting.

So, yes, they did occasionally go fast and occasionally cruise fast, but it wasn't all that often and tehre was a reason for it.

To put that in perspective, most F4 Phantoms could get to Mach 2.5 if they flew a very specific flight profile with the express intent to get to Mach 2.5. If they DID, the first priority when they slowed down was to hit a tanker, so a LOT of people knew it if you were hot-dogging it becuase they had to support you and fuel was planned before the fight. Many Phantoms were retired with zero or less than 5 total minutes at Mach 2+ on them. That's how rare it was to actually USE top speed. They mostly spent time, even if clean, at between 350 and 600 knots, with occasional forays into Mach 1.5 or so, even in combat areas. That comes from multiple F4 pilots over many years.

If they got into combat, they were up around Mach 1 give or take 0.3 Mach or so. Any faster and they couldn't turn very well and were going to be VERY short of fuel when combat was broken off. If they were too far from a tanker, it could easily turn into nylon letdown time, and DID on occasion. Combat time was directly related to the fuel state. If you got into bingo fuel (5 minutes remaining), and were still in combat, you were in deep kimshi. 

There weren't many tankers located within 5 minutes of a combat engagement at subsonic speeds, and 5 minutes at subsonic speed could turn into 1:30 or less in a heartbeat on afterburner. If the tankers were there, it was a mistake. That's too close to an armed enemy jet fighter for a tanker.

The P-541s were NOT quite that fuel sensitive, but they did NOT load up 7 hours of planned fuel for a 2 hour mission. So fuel was planeed adn your cruise was planeed along with it. I can guarantee that if you were flying from a Pacific island with fuel planned for a 4 hour mission plus 1 hour reserve, you weren't planning on a high-power cruise and you didn't waste fuel needlessly because landing strips in the Pacific are scarce. It was a bit different over Europe once the Allies were driving for Germany because friendly landing strips with fuel were there on the way home if they were needed.

But before D-Day, there were zero friendly strips and no fuel to be had, so it was better than an ocean, but not much. especially in typical bad weather.


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## Shortround6 (Jun 22, 2015)

According to the manual max continuous was 2700rpm. Max cruise was 2400rpm. 
The 1954 manual has 7 different range charts depending on under wing loads, fuel and gross weights. ALL 7 charts have a column (or a split column) for range when flying at 2700rpm and using 46in (or close to it). See chart in above post. 

There are also a number of climb charts for different loads, all using 2700rpm and 46in or as close to 46 in as the supercharger would supply. Depending on the load and weight (pair of 1000lb bombs?) it could take 54 minutes to climb to 25,000ft using that rpm and manifold pressure at a gross weight between 11,000 and 13,000lbs. Plane would cover 214 miles and use 99 gallons of fuel in the climb. 

With Uncle Sam paying for the planes, engines, spare parts (of which there were still a fair number around) and fuel the use of such power levels may have been fairly common. 

Today with a distinct lack of spare parts, knowledgeable mechanics (there are a few) and even 100/130 fuel not at many airports operating at such power levels is certainly bordering on fool hardy. Please look a the chart again, at 10,000ft the difference between 2700rpm/46 in and 2500rpm/42.5in is a whopping 16mph. The lower power level does save 15 gallons an hour to boot. Or drop down to 2200rpm and 40in. save another 12 gallons an hour and you are still doing 325mph. 

If I had a warbird I know what power levels I would be using, I mean can you really tell the difference in the seat of your pants between 325mph and 361mph? especially if you are using 27 gallons an hour less. 

But "stock" Mustangs with war equipment could "cruise" at 380mph at certain altitudes if the pilot wished. What his commander wished might be another story. Under certain, select conditions (like using 30,000ft) the P-51D could even "cruise" at 380mph using 2700rpm and 46in or full throttle while carrying a pair of 75 gallon tanks or a pair of 500lb bombs.

As has been noted by others, the vast majority of operations was done at slower cruise speeds and lower fuel consumption for very good reasons.

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## GregP (Jun 22, 2015)

Don't think so Shortround, but thay's OK. Perhaps the WWII pilots who give talks every month have just forgotten. None of the people I know who oeprate them would even consider it.

There is absolutely NO point in cruising around at 380 mph when the planes you are escorting are doing 180 mph and max coutinuous is defined in several manuals including the original engine and pilot's manuals. You'd never make the trip to Berlin and back at that fuel burn. You might do that for a short mission that was not escort, and was composed of fighters only, but I can't think of another reason unless it was a photo-recon run.


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## pbehn (Jun 23, 2015)

kool kitty89 said:


> Cruising at 380 MPH (even at best altitude for that speed) wouldn't give you the range to make it to Berlin and back, let alone enough reserve for combat and loiter time for landing.
> 
> The closest to that you'd probably get would be with aircraft cruising home after dropping tanks (and possibly expending ammunition). That or possible pushing into fast-cruise after dropping tanks while over the target area when most aggressively patrolling for interceptors.
> 
> Also remember for any sort of top cover (not roaming fighter sweeps) for slow cruising heavy bombers, you'd need to be weaving and circling over the bomber formation and the faster you cruise, the more fuel you waste flying in circles.



I think you miss understood my post. As I understand from reading here on the forum and elsewhere there were many phases on a P51 mission. Take off and climb, cruise to rendezvous while using external and rear tank, escort of bombers and then cruise home. As I understand it the most economical speed for a P51 with or without tanks was higher than the bomber formation which meant zig zag or circling, this is a compromise between economy and safety because the escorts need speed to fight. I always thought the cruise speed was in the region of 200-240MPH, 380MPH is approaching the maximum speed no way is that economical.


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## GregP (Jun 23, 2015)

I probably did misunderstand, pbehn. Mea culpa.

It sort of galls me that some people read the top speed and assume the planes flew that fast most of the time when they really didn't hardly ever get there unless in a dive. Most combat was also not at top speed as any hard turning or climbing would slow you down unless you were headed downhill. And you can only go so far down before dirt and rocks get in the way. Once you level off, you are somehwat quickly again well below top speed unless you are flogging the plane mercilessly.

If you are, you are a good POW candidate anyway. If you had any intelligence, you would fly hard enough to escape or pursue for a limited time, and then get back to the business of getting home or climbing back up to escort and enduring the questions later about why you abandoned your escort mission. Combat was a good excuse. Continued absence had NO excuse after a few times because that was NOT the mission ... escort was.

All bets were off on a fighter sweep because you didn't have to slow down for anyone including your own formation. In that case, maybe they DID fly at 380 mph for some limited time, but it certainly wasn't a 6 - 7 hour mission and you didn't fly that fast for too long without any point to it.


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## Mike Williams (Jun 23, 2015)

According to the P-51D-5 Pilot's Operating Instructions dated April 5, 1944, Max. continuous is 46" M.P. and 2700 RPM while Max. Cruise is 36" M.P. and 2400 RPM.

P-51D 44-15342 obtained 420 mph at 29,400' operating at max. continuous with wing racks and 357 mph with 2 110 gallon wing tanks. 381 mph was obtained at 25,000' operating at 40" M.P. and 2400 rpm with wing racks only.

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## drgondog (Jun 23, 2015)

Shortround6 said:


> Yes, that was with drop tanks.
> 
> Zeno's warbirds has a page from a manual without load but with racks installed.
> 
> ...



Don't understand the debate about the Official Pilot's Operating Manual. They are straight from the Flight Tests to optimize range for P-51D-15 with racks only, fully loaded internally, and also with 110 gallon fuel tanks and also 500 and 250 pound bombs... 11,700 pounds at take off with the 110's, 10,200 with full internal load, clean wing with racks only

From the Flight Tests - also available on Mike Williams' site, at 2700 RPM and 46" MP - a Safe Continuous Power setting for all Merlin Mustangs.

25K Rack only *404mph* TAS [email protected] gallons per hour 
25K 110 Gallon *371mph* [email protected] gallons per hour
25K 500# Bombs 357mph [email protected] gallons per hour
25K 250# Bombs 381mph [email protected] gallons per hour

*Those are not optimal cruise settings*. The optimal settings for maximum Range (normal deep escort profile to say Poland) for 110 gallon tanks at low recommended Lean mixture was for*25K 110 gallon tanks [email protected] gallons per hour for 2250 RPM and 29" MP*. That is the TAS they flew at 25000 feet while they were linked to close escort (i.e. Essing while connected to a specific Box). It was not the speed and settings used to fly to the R/V or Sweep or return home after BE unless the mission profile was Extreme Range requirement such as Posnan with a 1480 mile round trip.. Speed was life and the mission commander set the profile.

At normal Warbird cross country cruise altitudes of say 10,000 feet, without racks and externals, the P-51B/C/D with a 1650-3, 9 or -7 can be safely run at 46" and 2700 RPM all day long but it also burns 90GPH. At lower RPM and leaner mixture 40" with 2200 RPM and it will scoot along at 325mph with a burn of 66 GPM. That is conservative because Warbirds do not carry Guns, ammo or aft fuel tank so the flight is conducted at 900-1000 pounds less than the War TIME recommendations.

ANY of those cruise settings discussed above at 46" is safe for Warbird operations - even without yanking the guns, ammo and fuselage fuel... for 130/150. So for crappy expensive stuff today the settings will change to optimize burn quality without going too Lean. 

from the tests and published operating references 

For 25K altitude - 40" at 2400 RPM for racks only at 9600 pounds buys you 381mph at 77GPM, drop the revs to 2250/32 and you get 370mph at 68gph

The caveat is the peacetime fuel and the balance required to protect the Merlins... but SR's point about whether a P-51D could safely cruise at '380' is Not debatable - just could not fly near as far at that speed at 25K.

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## Conslaw (Jun 23, 2015)

The 380 MPH figure is what I remember from an Air Force Museum publication. If the planes could maintain a safe 380-390 MPH at continuous power settings while in the threat area, it would be very difficult for enemy fighters to pounce them even if taken by surprised, and it would be relatively easy to pounce enemy fighters which might be climbing or maintaining a lower economical cruise speed.


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## Shortround6 (Jun 23, 2015)

Some pictures of Moonbeam McSwine, the warbird in question











Two seater means no rear tank, also means modern avionics. rear armor gone (or most of it) , no gun sight, no bullet proof glass? metal fuel tanks? 
under the wing is interesting. Not only no bomb or drop tank racks but no cartridge ejection slots. No ammo and more than likely no guns (or dummy's or dummy muzzles?). 

Running lighter than military plane should be worth a few mph and running cleaner should be worth a few more. Either a lower power setting to reach 380mph or being able to hit 380mph at a lower altitude than an equipped military plane. 

What it does to overhaul life is certainly subject to question but the plane could do it.

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## drgondog (Jun 23, 2015)

GregP said:


> The P-51 had one of the lowest coefficients of drag of any WWII fighter, true. If I am not listaken, it actually had the lowest drag of ANY WWII piston fighter. But a stock P-51D, in factory-new finish, with a brand-bew Merlin, freshly broken in, and having not sat outside in the weather for days, weeks, or months ... could make a top speed of 437 mph clean (no racks or tanks) at the FTH of somehwere between 17,500 feet and 25,000 feet depending on Merlin dash number. That was at the maximum approved manifold pressure and 3,000 rpm.
> 
> 
> *Greg the flight tests run by Wright Pat w/Don Gentile used to validate the P-51D Flight Operating Instruction T.O. AN60JE-1 dated June 15, 1945 had the following:
> ...



The Group Ops dres up the first draft of mission profile based on the Frag order for that Fighter Group. He used the tables for WU/Take Off, Form up and climb to cruise Altitude. He reversed the R/V time and location using 'SOP' cruise to R/V based on Ramrod or Sweep or Patrol and took into consideration known flak concentrations or weather forecast, etc - to obtain the 'Leg' times/flight profile all the way back to Start Engine Times - then worked with Group or Deputy Group CO and Intelligence Officer and Weather Officer to check the assumptions and refine the Mission Plan. The details would be disseminated to the named squadron CO's and discussed at the Mission Briefing. This is where any changes, if made, to standard Cruise operating procedures would be made and carefully conveyed to flight and squadron CO's - two of which may have an escort assignment and the other an Area Patrol instead of all escort.

So, SOP, often modified but all per the standards defined in the P_51 Flight Operations data tables - as presented above by Shortround or pointed to by Mike Williams and myself in the Flight Test Reports


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## tomo pauk (Jun 23, 2015)

This table might be of interest re. speed of the P-51 - 440+ mph without racks, that took 12 mph for the P-51A/B/C and 4 mph for the P-51D/K.

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## GregP (Jun 23, 2015)

Hi Bill,

I know you like the P-51, but the standard service planes didn’t make the numbers that a brand new factory fresh P-51D did in the fastest test it ever ran. The numbers you state above are for a clean plane , fresh from the factory, with a factory test pilot flying it.

The planes in the ETO were service planes with wing rack, drop tanks, and had been sitting in the weather for months if not longer. The props had erosion from flying off of WWII airfields. They were not on a factory test flight.

I have the books and you do, too. At 10,000 to 10,600 pounds, at full throttle, and 2,350 rpm, the TAS at 15,000 feet is 325 mph. At 2,450 rpm and 43” at 20,000 feet the TAS is 340 mph. At 2,450 rpm and 43” at 25,000 feet the TAS is 365 mph. And that is for a clean aircraft. There WERE no clean aircraft on except missions. They all had drop tanks and most had racks. So that 365 mph rapidly becomes 330 – 340 mph, IF they cruise at 2,450 and 43”. Most pilots from WWII I talk with remember cruising at 2,100 – 2,250 rpm and 40” - 41” or full throttle at low rpm for normal fast cruise, and many times slower. Not everybody cruised fast. Usually only the guys in front. Everyone else was going slower and s-turning over the bomber stream. When the guys in front or whoever saw the enemy first saw the enemy, THEN they went into combat cruise.

If you’re going to make Berlin and back, you will be in column IV for maximum air range. In that column, at 25,000 feet, at 2,100 rpm ,and full throttle, you get 295 mph in a clean aircraft. Nobody was flying a clean aircraft and they weren’t going 380 mph on an escort mission until they HAD to.

If this goes like normal, we won’t convince one another of anything, but the numbers above are from the P-51D / K Pilot’s Operating Handbook, not from out of the blue.

The P-51 was a good plane, but it didn't run close to max speed for a 1,200 mile mission.


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## Shortround6 (Jun 23, 2015)

GregP said:


> The P-51 was a good plane, but it didn't run close to max speed for a 1,200 mile mission.



Is anybody here claiming it did?

Lets go back to Posts #10 and #11 where this got started. 

Post #10 " One of the keys to the success of the P-51 was its fast cruising speed. At altitude it could cruise over 380 MPH, faster than the top speed of most Japanese fighters and close to the top speed of the German fighters without their water injection. At that air speed, the P-51 already had enough energy for a pretty nice zoom climb,........"

Post #11 "There is no P-51 that cruises at 380 mph. Any standard P-51 D / K pilot manual will tell you that....."

I believe, unless you can point out somebody else's post that you are the only person talking about cruising to Berlin and back at 380mph. 

The plane _could_ cruise at 380mph at certain heights and loading's. 

And BTW just about every other US plane that has that type of chart in it has a column giving the range using max continuous power. Perhaps it is there to show the pilots what NOT to do. P-39Q *can* cruise at 2600rpm and 39in and get 300mph or over. It just doesn't go very far, like 1/2 the distance it goes at long range cruise settings. It isn't getting to Berlin no matter what cruise settings are used, does that mean that P-39 pilots in Italy *never* ran at max continuous power for 15-20 minutes while getting to or from a target?

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## GregP (Jun 23, 2015)

Shortround,

You are correct. It was me who said Berlin and back. Let's see, the P-51 was the escort fighter of choice for the ETO and the vast majority of it's missions were escort. I'd guess 75%+. So, yes, you absolutely COULD cruise at 380 mph if your element leader was an idiot. Why else would you be cruising along with 180 - 185 mph bombers at 380 mph?

Most likely you weren't anywhere near there *unless combat was imminent*, which I also said. You could cruise a 437 mph if you were so inclined, but not for very long. I'd say maybe 15 - 20 minutes until you were going to throttle back voluntarily or involuntarily. Some might liklely run longer than that. They did in a post-war USAAF acceptance test.

I also said that if you were on a fighter sweep, with clean airplanes and only fighters along for the ride, you could crusie fast, but you seem to have missed that. No matter.

I stand corrected, there were certain situations in which you could cruise up to 437 mph in a clean P-51D/K if you were so inclined. I am of the opinion that virtually nobody was so inclined, but there might be somone out there who did on a rare occasions when they weren't escorting bombers.

Most of the P-51 missions were escort and they absolutely didn't ... but they did get that fast and even faster in combat on the way down in a steep dive. Steep dives are by nature short missions, so they didn't do it for very long, probably on the order of less than 37,000 feet at a time on a 1,200 mile mission.

It was different in the Pacific. They DID NOT cruise at anywhere NEAR 380 mph over water (maybe they did in the jetsream on the way home if you look at groundspeed or waterspeed as the case may be), escort or no escort, unless they were approachning Japanese airspace and expected combat. Then they would push it up to 320 mph or so until the enemy was sighted. Then it was combat until you were breaking off and cruising back at normal speeds or swimming at really low speeds.

Thanks for telling me about the other planes' POH charts ... you never know where you will learn useful new things.


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## GregP (Jun 24, 2015)

Here's another try at logic ...


Let’s look at this from a planning point of view. Nevermind startup, taxi, takeoff, and forming up, a B-17 normally cruised at about 185 mph. It is 580 air miles from London to Berlin and back, or 1,160 miles round trip with no allowance for turnaround. 1,160 miles divided by 185 mph give a mission of 6.3 hours.

They are to be escorted by P-51Ds flown by you. Nevermind the startup, taxi, takeoff, and forming up, it is still 1,160 air miles, if they took off from London. And they didn’t and had to takeoff, form up ,climb, find the bombers, and escort. If you look at Tactical Planning Characteristics Performance Chart for the P-51D, with ZERO allowance for reserve, there are no entries at all for 6.3 hours at 10,000 feet or 25,000 feet at max continuous power. None.

There are 10 entries in there with ranges that allow 1,160 miles, but you won’t be anywhere NEAR the B-17s since you will be running away from them at all times.

At max cruise power, there are eight entries with 6.3+ hours endurance and the range to do it. All are at 10,000 feet and NONE are at 25,000 feet. This is at weight up to 11,800 pounds at takeoff. At long-range cruise at 10,000 feet there are eleven entries with durations of 6.3 hours or more. One can stay airborne for 12.0 hours! … at 10,000 feet, 11,800 pounds at takeoff, and long range cruise. There are NO entries at 25,000 feet that will make it on max continuous or max cruise.

So, if one group of P-51s wants to escort B-17s to Berlin and back, they cannot be at max continuous or even max cruise power since the bombers are NOT at 10,000 feet. To do the mission they MUST be at long range cruise at 25,000 feet. 

The chart is from Mike Williams archive: http://www.wwiiaircraftperformance.org/mustang/p-51-tactical-chart.jpg and I did not invent the numbers.

Let’s say we decide to load our trusty P-51D to 11,000 pounds with fuel, Ammunition, piddle packs, and the intrepid pilot … and we want to climb to 25,000 feet and cruise at least 7.0 hours and 1,400 miles or more (think London to Berlin and back with reserves). From the chart it will take 44 gallons to get to 25,000 feet.

For planning purposes we have 269 gallon internal and two 75-gallon drop tanks that are full to the brim … so we have 419 gallons aboard to start with. After climb to 25,000 feet we now have 375 gallons. The nearest range that is not less than 1,400 miles is1,470 statute miles and 360 gallons, which is possible with 375 gallons remaining after climb. You will be in column III of the flight planning chart, and your range is 1,470 miles at 2450 rpm and 43” of MAP at 365 mph.

Erueka, we can almost make the 380 mph cruise mentioned above with zero reserves. But … we have a problem. If we DO this, we can get there and back in 4 hours … true … but the bombers can’t. If we want to stay with them, we need at least 6.3 hours of endurance. Remember, we are faster than the bombers and must S-turn above them for the entire ride or at LEAST most of the way or this is all useless. So we are flying WAY more than 1,160 miles. 

If we cruise at 260 mph we can stay aloft for 5.3 hours and maybe someone else can pick them up on the way back. We can do that at 265 mph at 15,000 feet but at 25,000 feet we can’t unless someone relieves us at 4.7 hours of mission time.

To actually GET there and back WITH the bombers … we will be cruising at 220 mph or thereabouts or else we will be relieved by one or more other squadrons at some point. They actually DID relieve the escorts in practice, but they didn’t cruise at 365 mph over a 185 mph bomber stream and wait for timely relief. They cruised right where I said they did, at somewhere around 260 – 300 mph and the relief cruised in at 220 mph or so to extend range, and then took over.

Want to prove it, get a P-51D POH and plan a mission to Berlin and back. Assume you might be relieved as escort *once* and realize the bombers and headquarters were NOT happy if you left the big friends unprotected. I think you will need to take off with 419 gallons of fuel, but hey, you be the planner and see what you get. You have to be airborne for 6.3+ hours or be relieved and you do NOT want to be relieved within 80 miles of Berlin. That would mean escort confusion right where the Messerschmitts and Focke Wulfs are the thickest. So you need to be relieved earlier or later.

Of course, none of these constraints are there on a fighter sweep, and you might well cruise around at 365 mph ... and that still ain't 380 mph. These are, of course, book numbers for a factory fresh, clean P-51D. You might not see those numbers from a tired, dirty war-horse with racks and a rough prop from unpaved runways. Grass is great for tire wear, but not so good for propellers as things get sucked into the prop on takeoff early in the roll since they used bases with many planes stationed there and not pristine grass strips that were just mowed by the owner.

There are many solutions, some of them reasonably fast, if you don't have to stick with the bombers ... except that's why the P-51s were THERE. Ergo, my original post on the 380 mph cruise speed claim.

It just ain't so, at least on an escort mission of long duration. Later in the war when things were closer, sure. But you still had to stay around the bombers with an under 200 mph cruise speed. There were still some Messerschmits and Focke Wulfs around, even if not THAT many.

Then they got surprised by the Me 262s and that's another story.


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## drgondog (Jun 24, 2015)

GregP said:


> Hi Bill,
> 
> I know you like the P-51, but the standard service planes didn’t make the numbers that a brand new factory fresh P-51D did in the fastest test it ever ran. The numbers you state above are for a clean plane , fresh from the factory, with a factory test pilot flying it.
> 
> ...



NOOOOBody suggested that, nor are figures like 360-380 mph 'near max speed' or 'close to max speed'

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## pbehn (Jun 24, 2015)

did someone somewhere confuse 380KPH with 380MPH? just sayin.


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## drgondog (Jun 24, 2015)

GregP said:


> Here's another try at logic ...
> 
> *Oh, dear - please have patience with me as I try to follow you.*
> 
> ...



Back to the point - could a P-51 cruise at 380mph and go a long way? Why yes, Grasshopper it can. Might a P-51 Cruise at 404mph and go a long way? Why, Yes - again. Is a SOP deep penetration to provide close escort an example of applying Max Continuous Power throughout. Why, no - and at no time did Shortround or I postulate such foolishness.

Greg - in the future you need to get a better handle on the typical (SOP) cruise speed in TAS for B-17's 150mph IAS. When you talk to most pilots about their wartime experiences they will relate to IAS in either Ktph or Mph because there is no conversion in those cockpits and they didn't always fly at '10K' or '25K'


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## Conslaw (Jun 24, 2015)

Let's look at this another way: was there any other contemporary fighter that could fly at least 380 MPH at its best altitude longer than the P-51? I only know of two possible contenders: the P-38L and the P-47N. The 8th Air Force was in the process of getting rid of its P-38ths before the L model came out, and the P-47N did not fight in Europe. The merlin-engined P-51 Mustang was speed competitive with the best German piston-engined fighters even though the P-51 did not have water or nitrous injection systems and the Germans did. This allowed the P-51 to maintain a high continuous speed, and carry the energy of that speed into combat, where the energy was converted to climb rate in a zoom climb. The P-51's low CoD, allowed it to build up speed during a dive and retain that energy for the following zoom climb. That's how the P-51 with a moderate climb-rate on the charts was able to stay with fighters which on paper had a much higher climb-rate.


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## Shortround6 (Jun 24, 2015)

Once again from Zeno's. 







The P-38 cannot fly longer than the P-51 at high speed (380mph or so) although it can do it (Fly 380mph) while staying within max continuous power power setting at some point between 25,000 and 30,000ft. Like the Mustang, backing off a bit on the speed adds quite a bit to the range as getting down to where they could switch to the lean mixture meant they were burning 54% of the fuel and still getting 88% of the speed. 

Please note that this is with tank supports only and the P-38 is NOT going to do 380mph with any size under wing fuel tank/s. The late P-38s were a big improvement on the early ones but were not going to match the P-51.


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## pbehn (Jun 24, 2015)

There are enough tales of lancasters returning from Germany to prove that a merlin can cruise at any speed it has fuel for. The idea that it can travel as far at 380MPH as it can at 220MPH defies what I know about engines and drag resistance.


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## Shortround6 (Jun 24, 2015)

Who is saying it can go as far at 380mph as it can at 220mph? 

And again, we have to be very careful about specifying the other conditions at which the plane is "cruising". One chart shows a P-51D with a pair of 75 gallon tanks doing 202mph at sea level using 1600rpm and 32in and burning 42 gallons an hour. It will also cruise at 25,000ft with engine settings of 2100rpm and wide open throttle (engine limited by prop setting?) at 305mph and use 60 gallons an hour. Range is just about the same for planning purposes. The ability to "cruise" at 25,000ft or better where the air is thin can screw up basic drag calculations if comparing to planes that are cruising thousands of feet lower. 

The Mustang could "cruise" at 380mph with a pair of 75 gallon drop tanks (390 gallons available after basic allowance for starting, warm up and take-off). It was also supposed to be hit 370mph at 25,000 using max continuous power with a pair of 110 gallon tanks. (440 gallons total after basic allowance) so we also have to be sure we are comparing the same amount of fuel.


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## GregP (Jun 24, 2015)

Its not me who is missing the point Bill, it is you. This is tiresome, but one more shot at it, futile though it may be.

My dash 5 doesn’t have one single entry in the mission planning charts for 380 mph. The highest you can plan for is 375 mph. If you do plan for that speed, you certainly won’t be escorting anyone and you had better be flying a mission radius of 350 miles or less if you want to have some reserve in case of bad weather when you get home. 

You once took me to task for arguing pointlessly when the facts were against me. You’re there. Go plan an escort flight, London to Berlin, and come back and tell me you’d be cruising at 380 mph. You can’t, and that was my point, and it is true, needling and sarcasm aside.

Perhaps you might want to attend our program in July 4 entitled “Little Friends” where we will have a presentation on escorting bombers with the P-51D in the PTO. If you Google Planes of Fame and the events calendar, you can check it out. We will even have a WWII P-51 crew chief in addition to covering the flying, who will detail it from their perspective.

I will grant you can fly the P-51D pretty fast (365 – 375 mph) for shorter mission where there are only other fighters in the formation, but that didn’t happen a large percentage of the time, and they weren’t going all that far if they did. Several hundred miles. Possible after we had airstrips on the continent. It wasn’t happening in 1943 and most of 1944. DID happen in late 1944 – 1945. By the time April 1945 rolled around, they could probably hit Berlin at WER speeds and still make it back. But that is NOT what won the war in the air.


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## drgondog (Jun 24, 2015)

GregP said:


> Its not me who is missing the point Bill, it is you. This is tiresome, but one more shot at it, futile though it may be.
> 
> My dash 5 doesn’t have one single entry in the mission planning charts for 380 mph. The highest you can plan for is 375 mph. If you do plan for that speed, you certainly won’t be escorting anyone and you had better be flying a mission radius of 350 miles or less if you want to have some reserve in case of bad weather when you get home.
> 
> ...



Bless you Greg - may we conclude that a.) you know that at 2700RPM/46'MAP and 100gph burn rate that a P-51D can cruise (initially - but faster as the weight of the fuel is burned away) at 375mph TAS at 25,000 feet with two 110 gallon external tanks, and b.) that absent tanks and operating at 2700RPM/46" MAP it can cruise initially at 404mph at 100gph - but faster as internal fuel is burned away, and that c.) that is Not a practical 8th AF long range escort Mission Profile


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## l'Omnivore Sobriquet (Jun 24, 2015)

I always thought that the P-51D escorts (ETO) were carried in two waves. 
Each one cruising most of the time at the Mustang's own 'best speed' for long range, that is, much faster than the biggies. Neither of those waves accompanied the Big Friends the whole way.

First 1/3rd of the bombers' path would be covered by short range escort (Spitfires, P47...), then the 1st wave of Mustangs, having departed late, and cruised their own economical 'fast' speed, joined the biggies, loitered with them a bit (doing S) for the 2nd 1/3rd of the path, then upon being relieved by the 2nd wave Mustangs, went on free fighting for a while, away from the bombers, causing havoc.

A small portion of the escort P-51D could be dedicated to accompany the Big Friends the whole way, at close range, but that's just a small portion. The main P-51 force being, most of the time 'fast' either for range economy or of course fight. [and quite away from the bombers.]

I suppose you all know this, or is it simplistic, or a myth ?

I always thought that to achieve long range the P-51D needed to cruise high and fast (best distance covered for the fuel consumed, thanks to very clean airframe and potent altitude engine+compressor package.)

I'm afraid Greg and Drdondog are chasing different cats here... But I 'd sure like to know the real numbers, and this is an interesting read.


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## GregP (Jun 24, 2015)

They did take turns escorting bombers, l'Omnivore Sobriquet. I made a statement about cruise speed when escorting bombers and Bill jumped on it just like that cat you mentioned. Predictable. In WWII, after things got going, one group or more would escort outbound and another group would take over inbound, having cruised there quite efficiently so they'd have the fuel to escort all the way back home. It sort of depended on what targets were on for the day and how much enemy fighter resistance was expected enroute.

Unfortunately, the guys who there there don't support that they flew fast over the bombers they escorted. They cruised to save fuel and only got fast when they got jumped, expect engagement, or saw enemy planes in the distance closing. The idea was to stay with the bombers as long as possible.

If they were alone (just with other fighters) then they had no constraints and were free to plan their flights as they so chose. I never made the claim that all the P-51 mission were escort missions. But, once again, if you aren't escorting bombers, then unless you are just trolling along looking for enemy fighters to shoot down, what are you doing there?

If you are providing ground support, you had a couple of bombs under the wings and weren't cruising at 380 mph. If you DID happen to be on a fighter sweep, then you also weren't that fast until you got to indian country ... anywhere you expected flak or enemy planes be. They didn't usually fly "blind." The unit S-2 could tell them mostly where the flak was and where they could expect enemy fighters. Messerschmitts weren't exactly "long range" planes, so you knew about where they might be from where they were based.

If they were in a fighter-only formation only, I'd expect them to be above 300 mph when they entered that area and to decelerate back to good fuel economy speed when they were in areas where no contact was expected.

Here is one page on the web: P-51 Mustang Specifications - MustangsMustangs.com

You don't see any 380 mph cruise speeds, do you? Look at the range. The P-51B could get to Berlin and back with drop tanks at 290 mph @ 20,000 feet. There is no single entry anywhere for cruise speeds above 300 mph except for the P-51H that didn't ctually fight in combat in WWII, and the 300 mph cruise was the Allison-powered P-51A.

Now we all KNOW the P-51B/C/D/K could easily get to 380 mph and faster, but they didn't cruise there normally. Cruising there would be over the max continuous power setting in all of my pilot manuals for the aircraft, which you could DO ... but there was really no point in doing it unless you had a reason to do so. If they were alone (just fighters), I'd expect them to cruise between 290 and 365 mph TAS at 25,000 feet. Anything faster would be a photo run over a defended target, an attack run-in, or something like that. And that fits in very nicely with what the real WWII veteran pilots said in many presentations at the museum.

As I said above, we're having another one in two weeks about escorting bombers with the P-51D in the PTO ... seemingly a related subject to the discussion at hand. It isn't like we haven't had this subject come up before.


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## pbehn (Jun 24, 2015)

Sorry guys you have lost me. It may be possible to hit 380MPH with whatever external tanks and call that "cruising" at whatever altitude but that isnt cruising. My car is restricted to 155MPH, it does 
45 MPG at any continuous speed between 60 and 110 MPH above that consumption plummets to between 8 and 10MPG at 140 MPH. Being a restricted engine I could hold it with my foot on the floor on a German autobahn without it blowing apart but that isnt "cruising".

Can someone tell me how many gallons per hour a merlin consumes at the maximum because I clearly remember reading about BoB pilots returning to base after short engagements low on fuel and ammunition having flown nowhere but being on maximum power for a comparatively short time climbing and in combat. There is a very real reason that "combat range" includes 15 minutes at maximum, it consumes massive volumes of fuel.


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## GregP (Jun 24, 2015)

For a P-51D, at max continuous power, which is 46" MAP @ 2,700 rpm, it uses 98 GPH at 25,000 feet. At the same altitude and full throttle and 2,100 rpm, it uses 60 GPH, or a gallon a minute.

If you are down at 10,000 feet and cruising at 34" MAP and only 1,650 rpm, you can reduce to 49 GPH. But the government was paying for the overhauls back then. Most people today who fly one plan on 60 GPH and don't try to lean it out quite so far. There is almost nobody today who can run one at full power, much less WER ... because we don't have the fuel to get best performance out of a Merlin. We're stuck with 100LL petrol ... unless you happen to be racing at Reno.

Then they supply good fuel ... most of the time.

I know 3 or 4 people who cruise them square ... that is, 25 - 25, or 25" MAP and 2,500 rpm. Figure a gallon a minute for that after you cut back from takeoff and climb power, and you won't be too far off.


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## Shortround6 (Jun 24, 2015)

A lot depends on altitude. It may also depend on _which_ P-51D we are talking about. 

According to the post war manual A clean P-51D (racks but no stores) needed 20+ gallons for starting, warming up and take-off. It needed 17 minutes to climb to 25,000ft using 2700rpm and 46in. It used 42 gallons for the climb and _could_ cover 66 miles while climbing Page 105) but lets ignore that as part of forming up in small formation. Greg has specified a 350 mile radius for this example. Chart after allowance for take off says 240 gallons available without external tanks, but we used 42 for the climb so 198 gallons left. 
Column III of the "Flight Operation instruction Chart says the plane should do 397mph at 25,000 ft using 2400rpm and 42in (nowhere near max continuous) and 160 gallons should be good for 735 miles. Covers the 350 mile radius with a bit left over like 5 min but then we still have 38 gallons left in the tanks _if_ our plane has not used any higher throttle settings during the flight (combat) and 38 gallons is good for over 50 minutes as most economical at low altitude. BTW, column IV on the chart says 370mph at 25,000ft using 2250rpm and full throttle (whatever boost the engine will give at 25,000ft at 2250 rpm) and at that engine setting 700 miles needs only 140 gallons of gas. Plane could cruise at 380mph using in between settings and use 150 gallons? At 24,000ft , 3000rpm and 61in the fuel use is supposed to be 3.0 gallons a minute. 

No figuring in the above for the decent from 25,000ft to near sea level, count that as part of the reserve.


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## Shortround6 (Jun 24, 2015)

pbehn said:


> Sorry guys you have lost me. It may be possible to hit 380MPH with whatever external tanks and call that "cruising" at whatever altitude but that isnt cruising.
> 
> Can someone tell me how many gallons per hour a merlin consumes at the maximum because I clearly remember reading about BoB pilots returning to base after short engagements low on fuel and ammunition having flown nowhere but being on maximum power for a comparatively short time climbing and in combat. There is a very real reason that "combat range" includes 15 minutes at maximum, it consumes massive volumes of fuel.



A cruise chart was posted back in post # 16. Post war Manual doesn't give fuel consumption for WER but for Military power it was about 3.0 gals a minute. That is 61in or a bit over 15lbs boost. Mustang carries about 2 1/2 times the Fuel of a Spitfire. Take out 45 gallons from above example for 15 minutes at Military setting. But that was for an aircraft without drop tanks.


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## pbehn (Jun 24, 2015)

3 gallons per minute is 180 per hour a six hour mission uses 1080 gallons.................I think my question is answered.


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## Greyman (Jun 24, 2015)

Mustang Pilot's Notes has:
67 boost, 3000 rpm, 137/165 imp/us gallons per hour
61 boost, 3000 rpm, 112/135 imp/us gallons per hour


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## pbehn (Jun 24, 2015)

Greyman said:


> Mustang Pilot's Notes has:
> 67 boost, 3000 rpm, 137/165 imp/us gallons per hour
> 61 boost, 3000 rpm, 112/135 imp/us gallons per hour



I always understood that the chief difference between the P51 and the P47 was 40 to 50 GPH at cruising speed.


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## GregP (Jun 24, 2015)

There aren't any P-51D charts with a 397 mph TAS at the power levels you suggested, Shortround. At least not in 51-127-5 dated 15 Aug 1945, which is a Pilot Flight Operting Instruction.

Google that number and download it. And since you are quoting a clean airplane, and going so fast, you certainly aren't escorting anybody. Maybe you're using AN 01-60JE-1?


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## Mike Williams (Jun 24, 2015)

Hmmm...

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## Shortround6 (Jun 24, 2015)

pbehn said:


> 3 gallons per minute is 180 per hour a six hour mission uses 1080 gallons.................I think my question is answered.



Is it? nobody is claiming the Mustang was cruising at "full throttle" Ie, 3000rpm and 61in (15-16lbs boost).

American max continuous sort of split the difference between British Climb and Max cruise. Americans would _allow_ 2700rpm and 46in (8lbs) as long as the fuel lasted or temperatures remained in limits. 
Two stage Merlins used in Spitfires were _allowed_ a "climb" rating of 2850 rpm and 12lbs (54in?) for 30 minutes and 2650rpm and 7lbs boost (44in) max cruise. I sure wouldn't get too exited about 50rpm and 1lb of boost. you can get that kind of variation between two planes sitting next to each other on the flight line n any given day. 

The Mustangs fuel capacity helped give it a disproportionate range compared to similar fighters ( not comparing P-47 and P-38s here). 
Comparing to Spitfire MK IX they are both going to use up _about_ the same amount of fuel starting up, warming up, taxing and taking off. If you are going to climb to 25,000ft the Mustang sill use a bit more fuel. It is heavier. How much the lower drag helps I don't know. 
So lets assume the Spitfire is staring with 103 US gallons and the Mustang is starting with 180 US gallons. They both US 20 gallons from start up to wheel sup. Mustang uses 42 gallons getting to 25,000ft. Spitfire uses less-30-33 gallons? even less? Lets say 20 gals just for illustrations sake. Mustang has used 62 gallon and has 118 gallons left, Spitfire has used 40 gallons and has 63 gallons left. 15 minutes at 3 gallons a minute each for combat =45 gallons. Mustang has 73 gallons left and the Spitfire has 18 gallons. Now we do want some reserve to help find the home field so 10 gallons should give us around 20 minutes at most economical (give or take). Spitfire has 8 gallons to divide up between cruising out and cruising home. Mustang has 63 gallons. 
Now throw the rear fuselage tank (85 gallons max, but often restricted to less) in the Mustang, start up, warm up and take-off stay the same, climb to 25,000ft stays pretty much the same, combat allowance stays the same, reserve stays the same (or is increased) but basically the the rear fuselage tank could double the operational radius since you had about twice the fuel for "cruising". change in drag is negligible because we haven't changed the outside of the plane. 

The above is simplistic (very) but hopefully gets the point across. we have to be careful that we are comparing apples to apples and just because another aircraft with different drag and vastly different fuel capacity could do something or behaved a certain way does not mean the Mustang is going to have similar restrictions. It may have it's own restrictions/problems though.


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## Shortround6 (Jun 24, 2015)

Mike Williams said:


> Hmmm...



Hmmm...........Indeed


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## grampi (Jun 25, 2015)

pbehn said:


> Sorry guys you have lost me. It may be possible to hit 380MPH with whatever external tanks and call that "cruising" at whatever altitude but that isnt cruising. My car is restricted to 155MPH, it does
> 45 MPG at any continuous speed between 60 and 110 MPH above that consumption plummets to between 8 and 10MPG at 140 MPH. Being a restricted engine I could hold it with my foot on the floor on a German autobahn without it blowing apart but that isnt "cruising".
> 
> Can someone tell me how many gallons per hour a merlin consumes at the maximum because I clearly remember reading about BoB pilots returning to base after short engagements low on fuel and ammunition having flown nowhere but being on maximum power for a comparatively short time climbing and in combat. There is a very real reason that "combat range" includes 15 minutes at maximum, it consumes massive volumes of fuel.



I'd like to know about a car that gets 45 MPG at 110 MPH...I didn't even know such a car existed...


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## pbehn (Jun 25, 2015)

grampi said:


> I'd like to know about a car that gets 45 MPG at 110 MPH...I didn't even know such a car existed...



3 litre turbo diesel Audi, thats what it shows on the instantaneous and average MPG. The problem is in the "continuous" bit. Even on an autobahn with no speed limit the faster you want to travel the more times you have to brake or at least coast, even in a stream of cars doing 110 MPH you are on and off the gas all the time even if you dont touch the brakes. If you slow down to 100 then to get back to 110 sees you doing about 6 to 8MPG for a while. Below 60 it isnt any more economical either as it starts shifting down the gears 50MPH is 1000RPM in 7th. At 110 it is much more economical than my old 2 litre toyota diesel which was thrashing its innards out. That said, I have never ever got near the claimed figures around town and it has 50000 on the clock now and uses about 10% less than when I bought it.


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## Conslaw (Jun 25, 2015)

Friends,

I think we're too hung up on a number. There is nothing magical about 380 MPH. The tactical advantage doesn't come in a number it comes in the status of being "fast enough". My premise is that entering into the combat area fast, before contact with the enemy is a huge tactical advantage. At this stage, you aren't going to be be using any fluid injection, and you are not going to be using a power setting that requires a tear-down at the end of the flight. In other words, you aren't going to uses "war emergency" power. You also aren't going to use a power setting that doesn't give you enough endurance to do what you want to do. You will use the highest power setting that allows you to do what you need to do. You might call that a "fast cruise". You might call it something else. The Mustang, because of its low drag, could go faster per unit of power and fuel consumption than most or all of its peers/adversaries. Going into the battle fast in a Mustang is crucial because the plane is heavy in relation to its power. Not being caught low and slow is crucial to survivability in a P-51. If a P-51 is bounced while in eco-cruise, all of its performance advantages are gone. Conversely, if the P-51 maintains a continuous speed (none dare call it "cruising") in the combat area which is above the maximum continuous speed of its adversary's, the adversary will be at a significant disadvantage unless the adversary has a substantial altitude advantage. It is unlikely the adversary will have a position advantage at the Mustang's 6 because the Mustang already passed that area faster than the adversary could go. If you start with that speed advantage, add in a numerical advantage and the advantage that the P-51's main job is to protect bombers, and the Luftwaffe's main ob was to shoot down bombers, it is easy to see how the P-51 had the second highest score against enemy aircraft for US fighter types. (#1 was the F6F Hellcat which was slower than the Mustang, but was fast enough to do what it had to do.)

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## GregP (Jun 25, 2015)

You're right. Nothing magical about it at all. But it was stated and they didn't do it in the real, actual war.

Capability to do it aside, why the heck would anyone escort someone while flying twice the speed of the escorted planes? You'd be more than doubling your plane's actual flown range, and a 1,200 mile mission is long enough.

Pushing up the speed when you expect combat is reasonable, but cruising there isn't. Might be different if you were escorting B-29s and if they were crusining at 230+ mph, then there would be at least SOME justification for flying faster in the ETO, but we din't use B-29s in the ETO , and there was NO point in going faster in the PTO most of the time becuase the weather was mostly severe clear and you could see your enemies a long way off.

If the weather was bad that's another story since you were better off engaging faster against Japanese fighters. If you fought them slow, the'd likely get you.


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## drgondog (Jun 25, 2015)

Conslaw said:


> it is easy to see how the P-51 had the second highest score against enemy aircraft for US fighter types. (#1 was the F6F Hellcat which was slower than the Mustang, but was fast enough to do what it had to do.)



A common misconception. The F6F was credited with 8 (ETO),0 (MTO), 5160 (PTO) 0 (CBI)Total = 5168

The P-51 was credited with 4239 (ETO) 1862 (MTO),297 (PTO), 345 (CBI).. Total = 5964.



Aircraft Type	ETO - European Theatre of Operations	MTO - Mediterranean Theatre of Operations	PTO - Pacific Theatre of Operations	CBI - China-Burma-India	Total
P-51(Includes F-6 and A-36)	
P-51 4239	1063	297	345	5954
F6F	8	0	5160	0	5168
P-38	497	1431	1700	157	3785
P-47	2685.5	263	696.67	16	3661
P-40	0	592	660.5	973	2225.5
F4U	0	0	2140	0	2140
F4F	0	26	986	0	1012
FM-2	0	0	422	0	422
Spitfire	15	364	0	0	379
P-39 P-400	2.5	25	288	5	320.5
SBD	0	0	138 138
P-61	59	0	63.5	5	127.5
TBF/TBM	0	0	98	0	98
Beaufighter	6	25	0	0	31
F2A	0	0	10	0	10
P-43	0	0	3	3	6
P-36	0	0	3	0	3
P-70	0	0	2	0	2
P-26	0	0	2	0	2
P-35	0	0	1	0	1
Mosquito	0	1	0	0	1

Aircraft Type	ETO - European Theatre of Operations	MTO - Mediterranean Theatre of Operations	PTO - Pacific Theatre of Operations	CBI - China-Burma-India	Total
P-51(Includes F-6 and A-36)	4239	1063	297	345	5954
F6F	8	0	5160	0	5168


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## drgondog (Jun 25, 2015)

GregP said:


> You're right. Nothing magical about it at all. But it was stated and they didn't do it in the real, actual war.
> 
> *Greg - slooooooowly. It was stated that it Could cruise at Max Continuous Power at 380, when in fact with just racks it Could cruise at 404-410 mph TAS.
> 
> ...



Once again, to help you understand escort factors for the P-51, the reason that flight tests were done Before AN 01-60JE-1 were to fully understand optimal cruise settings BELOW maximum continuous power - which at the same time were nearly 70-100 mph faster than the B-17G at 25000 feet at Best settings for 110 gallon tank cruise speeds.

Sloooooooooooowly Greg - the 281mp TAS from Best Cruise setting (way below Max Cruise Power) was close to 200 IAS at 25,000 feet for 4.81 miles per gallon for 11,600 pound P-51D-5-NA. As the fuel burned off, the Gross weight burned away at about 300 pounds per hour giving the P-51D-5-NA even better cruise performance each hour of the escort leg.

Sloooooooooooowly Greg - at 281 to 300 mph for a two hour penetration/target and withdrawal mission before relief - those darn P-51s are still flying 80-100mph FASTER than those slow ass B-17s at 205mph TAS.. BUT Dayum - they are still hanging around those rascally slow B-17s (or the faster B-24s). How Essing or running up and back paralleling the Bomber boxes they were assigned to.


So - Please quit darkly hinting about boneheads that don't understand you - or escort tactics flown by all the folks that lecture at POF. THEY aren't Disagreeing with the scenario I just laid out for you. YOU don't comprehend what they are telling you - and you don't know enough about Mission Profiles and Operational planning/Execution to ask questions when you don't comprehend what you are hearing?

QUIT saying or implying that either Shortround or I are saying that ETO missions were flown ANYWHERE NEAR max Continuous Power. It is irritating that you don't understanf, but even more irritating that you keep repeating yourself.


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## pbehn (Jun 25, 2015)

I was just surprised and curious as to how an aircraft could be said to "cruise" with or without external tanks, full or almost empty internal fuel at almost any speed between stall and maximum as the same in terms of economy and therefore distance. The aerodynamic drag of external tanks and the additional drag of having to provide lift for the extra weight to me means the quoted cruise speed would actually be the maximum or close to it. Drag increases with speed, increasing weight increases drag in the case of internal fuel, increasing fuel by external tanks increases weight and massively increases drag. The idea that in any configuration a P 51 can fly about at any speed and fuel consumption is not a serious consideration is, shall I say new to me.


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## Shortround6 (Jun 25, 2015)

Please look at the charts provided. 

Or this test. P 51D Performance Test

Please note using WER this plane could do 438mph at 25,000ft using 67in and 3000rpm and that was calculated to be 1410hp.
Dropping to Military power the plane could do 428mph at 25,000ft using 61in and 3000rpm and that was calculated to be 1285hp.
Dropping to max continuous the plane could do 404mph at 25,000ft using 46in and 2700rpm and that was calculated to be 1025hp. 

72.7% of the power will give you 92% of the speed so the cruise figures are hardly maximum. Many planes cruise at 70% of max power (OK I cheated a bit, many planes would cruise at 70% of military of take-off power)

However your statement about " almost any speed between stall and maximum as the same in terms of economy and therefore distance" isn't quite right either as the charts show that on the same fuel the Mustang will go 35% further by slowing down to around 335mph from the 390-400mph speed.


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## Ottobon (Jun 25, 2015)

There is a HUGE distinction between how lightweight and high power planes like say Spitfires, mid to latewar Yaks Lavochkins, BF 109s, or even A6Ms can utilize zoom climbs and how heavyweight, high speed, but lower power to weight planes like a P-47, Tempest, or FW 190 can utilize a zoom climb. 

The distinction being that in steep, high G, and high angle zoom climb being a fantastic move in the lighter planes which usually incure less induced drag and feature very high powerloading/climbrate. With heavy planes you have to maintain that speed by not pulling too many Gs (bleeding too much speed) and then letting your power and inertia from the heavy weight or aerodynamics (P-51) sustain your climb and extend away.


The best description of this effect is probably told first hand in a story by Robert Johnson where he had a impromptu mock dogfight with a unknown Spitfire pilot:

_*"I opened the throttle full and the Thunderbolt forged ahead. A moment later exhaust smoke poured from the Spit as the pilot came after me. He couldn't make it; the big Jug had a definite speed advantage. I grinned happily; I'd heard so much about this airplane that I really wanted to show the Thunderbolt to her pilot. The Jug kept pulling away from the Spitfire; suddenly I hauled back on the stick and lifted the nose. The Thunderbolt zoomed upward, soaring into the cloud-flecked sky. I looked out and back; the Spit was straining to match me, and barely able to hold his position.

But my advantage was only the zoom--once in steady climb, he had me. I gaped as smoke poured from the exhausts and the Spitfire shot past me as if I were standing still. Could that plane CLIMB! He tore upward in a climb I couldn't match with the Jug. Now it was his turn; the broad elliptical wings rolled, swung around, and the Spit screamed in, hell-bent on chewing me up.

This was going to be fun. I knew he could turn inside the heavy Thunderbolt; if I attempted to hold a tight turn, the Spitfire would slip right inside me. I knew also, that he could easily outclimb my fighter. I stayed out of those sucker traps. First rule in this kind of fight: don't fight the way your opponent fights best. No sharp turns; don't climb; keep him at your own level.

We were at 5,000 feet, the Spitfire skidding around hard and coming in on my tail. No use turning; he'd whip right inside me as if I were a truck loaded with cement, and snap out in firing position. Well, I had a few tricks too. The P-47 was faster, and I threw the ship into a roll. Right here I had him. The Jug could outroll any plane in the air, bar none. With my speed, roll was my only advantage, and I made full use of the manner in which the Thunderbolt could roll. I kicked the Jug into a wicked left roll, horizon spinning crazily, once, twice, into a third. As he turned to the left to follow, I tramped down on the right rudder, banged the stick over to the right. Around and around we went, left, right, left, right. I could whip through better than two rolls before the Spitfire even completed his first. And this killed his ability to turn inside me. I refused to turn. Every time he tried to follow me in a roll, I flashed away to the opposite side, opening the gap between our planes.

Then I played the trump. The Spitfire was clawing wildly through the air, trying to follow me in a roll, when I dropped the nose. The Thunderbolt howled and ran for earth. Barely had the Spitfire started to follow--and I was a long way ahead of him by now--when I jerked back on the stick and threw the Jug into a zoom climb. In a straight or climbing turn, the British ship had the advantage. But coming out of a dive, there's not a British or German fighter than can come close to a Thunderbolt rushing upward in a zoom. Before the Spit pilot knew what had happened, I was high above him, and the Thunderbolt hammering around. And that was it--in the next few moments the Spitfire flier was amazed to see a less-maneuverable slower-climbing Thunderbolt rushing straight at him, eight guns pointing at his cockpit." *_

(From Fighter Combat, Robert Shaw)


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## GregP (Jun 25, 2015)

Bill,

You and I are gonna' disagree forever on how fast the Mustang cruised. Just a fact. You think anybody in 1943 - 1944 took off at under 10,500 pounds?

In fact, we can disagree and it's fine. I know what the guys I know who own them say and what the veterans who flew them say, and that's good enough for me. If it isn't for you, well then - OK.

Let's say we both think it was a very good fighter, even great, and let the details alone betwen us. I'll continue to think what I do and so will you. Neither one detracts from the combat record or the legacy, so let it go at that. 

I'll allow they cruised fast on fighter sweeps away from bomber escort, but I'll just laugh at the thought 410 mph cruise. Didn't happen as far as I know. But out of completeness, I will ask next weekend when the vets show up again for the "Little Friends" event.

Please quit being condescending. It's all I can do to be civil already. Just say what you're going to say and leave out the barbs and put downs. Things will be much friendlier that way.


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## Conslaw (Jun 25, 2015)

I love this quote from Johnson about his climbing duel with the Spitfire. Later in Thunderbolt, (page 176 according to Google book search) he talks about how the paddle-blade propeller helped the Thunderbolt's performance. He said after he got the paddle-blade propeller he had a climbing dual with a Spitfire 9b - the same model that out-climbed his P-47 earlier, and this time the Thunderbolt was the faster climber.


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## GregP (Jun 25, 2015)

Lots of people forget that the P-47 had two lives ... before paddles and after paddles.


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## Ottobon (Jun 26, 2015)

Happy you enjoyed it, another comment or subject about zoom climbing real quick.

Maybe I'm barking up a tree that has already read these documents, but i always found the F4U vs FW 190 A4 documentation interesting,

http://www.wwiiaircraftperformance.org/fw190/ptr-1107.pdf

Specifically the part where the FW 190 A4 being noted as having much better performance in high speed zoom climbs (although worse at any fairly low/medium speeds.) I'll assume this is mostly down to drag, although more specific aspects of it would be interesting to know. If nothing else the ideal climbspeeds of the F4U and FW 190 alone indicate a FW 190 has low enough drag but also high enough wing loading it just works better at high speed (about 160mph on Corsair vs 180mph on FW 190 iirc. Quite large frontal area of the F4U probably being a factor. 



Anyways i find it interesting because considering both the FW 190 A4 and F4U-1 (with Water Injection apparently) jockied for similar speeds, acceleration, and climbrate at various altitudes i would normally suspect that with built up inertia a F4U due to excess weight it would be close to the FW 190 A4 in a high speed zoom climb, but apparently the aerodynamics are such that the 190 would just pull away in any high speed zoom climb.

Any comments on this subject?


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## GregP (Jun 26, 2015)

Never knew the F4U and the Fw 190 ever fought one another, so never considered it. Will have to think on it. I'd take an F4U-4 any day, but the F4U-1, -1A, and -1D are much closer to the Fw 190 radial aircaft. They are Naval and so have the requisite weight and low-speed handling and ruggedness for carrier operations. They also rolled better than some US fighters but not as well as the Fw 190.

When I get time, I'll look at it. Good comparison to think about.

The Fw has the armament advantage all the way, but the F4U ain't no slouch in a fight.


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## Mike Williams (Jun 26, 2015)

Ottobon said:


> Happy you enjoyed it, another comment or subject about zoom climbing real quick.
> 
> Maybe I'm barking up a tree that has already read these documents, but i always found the F4U vs FW 190 A4 documentation interesting,
> 
> ...



Perhaps you're conflating the results of sustained climbing with zoom climb? Section 3. a. of the report discusses rates of climb at rated powers for indicated airspeeds of 140, 160, 180 and 200 knots at various altitudes, with the FW 190 generally being better the faster the climb.

Section 3. f. of the report discusses manueuverability, noting that "In zooms after dives the Fw-190, f4u-1 and F6f-3 were found to be about equal."


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## drgondog (Jun 26, 2015)

GregP said:


> Bill,
> 
> You and I are gonna' disagree forever on how fast the Mustang cruised. Just a fact. You think anybody in 1943 - 1944 took off at under 10,500 pounds?
> 
> ...



Greg go back to your earlier post (#36) where you opened it up with "lets use Logic here" as if you were talking to a retarded child who didn't understand the depth of your brilliance - to illustrate a point that was not even the topic framed in context. It went downhill from there.

Your opening to the world of debaters on this subject - after you missed what Shortround said and what I said - was:

*Here's another try at logic ...

Let’s look at this from a planning point of view. Nevermind startup, taxi, takeoff, and forming up, a B-17 normally cruised at about 185 mph. It is 580 air miles from London to Berlin and back, or 1,160 miles round trip with no allowance for turnaround. 1,160 miles divided by 185 mph give a mission of 6.3 hours.*

Take this statement and the rest of your post to Bud Anderson if he is there, hand it to him and ask for a comment about your logic from 'a planning point of view'.

Write the comments down, Report back.


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## grampi (Jun 26, 2015)

Conslaw said:


> I love this quote from Johnson about his climbing duel with the Spitfire. Later in Thunderbolt, (page 176 according to Google book search) he talks about how the paddle-blade propeller helped the Thunderbolt's performance. He said after he got the paddle-blade propeller he had a climbing dual with a Spitfire 9b - the same model that out-climbed his P-47 earlier, and this time the Thunderbolt was the faster climber.



I don't see a P-47 outclimbing a Spit regardless of what prop it has on it...the power to weight ratio just doesn't support his claim...


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## drgondog (Jun 26, 2015)

Conslaw said:


> Friends,
> 
> I think we're too hung up on a number. There is nothing magical about 380 MPH.
> 
> ...



Because of the nature of the range requirements for most deep strikes, fuel management was king. The eyes were depended on because the P-51 needed to cruise in the 4-4.8 mile per gallons per hour range of fuel consumption (60-70 gph) while fuel remained in a 75/110 gallon tank. That 'selects' the Cruising speed you think you can afford An 8:05 hour mission is the longest I am aware of in the ETO (admittedly a relatively small sample sixe)- but even that translates to 59+ gph. The Mustang can't go very fast at that average burn rate on any leg of a mission when the rock bottom is around 52gph


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## Shortround6 (Jun 26, 2015)

part of the problem in reconciling cruise speeds and range compared to other fighters is that only about 3 fighters ever took on really long range missions at high altitudes, fighter missions that is. The Spitfire took on long range photo recon missions. 

Here is a graph from Mike Williams site for power required for different speeds and altitudes. 







Please note that using 600hp the speed could vary from just over 260mph at 5,000ft to just over 350mph at 35,000ft. Granted the 35,000ft altitude is pretty useless for missions lasting hours due to oxygen consumption and cockpit heating and other health issues for the pilot. Also the engine will use a bit more fuel to make 600hp at the higher altitudes because it is powering the high gear of the supercharger. But a 23% increase in speed (and thus range) for only a little more fuel burn? At a much more useful altitude 25,000ft the Mustang can be doing 325mph on 600 hp? 

The only fighters that could really cruise that high for long ranges were ones with two stage superchargers. Either turbo or mechanical. Single stage engines had to be pushed a bit more to make a reasonable speed (Cruising at much under 200mph indicated or 270-280mph true probably wasn't a good idea). A P-39Q needed 2600rpm and 26in MAP to do 222mph indicated at 20,000ft and 60 gallons an hour. Trying to fly 5,000 ft higher means pushing the engine harder. For some of the single stage aircraft with small fuel capacities it also came down to using the fuel climbing or for cruising. A P-40 with a drop tank (or bomb) could use 14 gallons of fuel climbing from 20,000ft to 25,000ft and maybe that 14 gallons would be better spent cruising at level altitude for 15-20 minutes. 

For the Americans that pretty much means 5 aircraft and four of them were much bigger, had much more drag and sucked way more fuel per hour than the Mustang. 
The British had pretty much the Spitfire with a two stage supercharger (single engine) and nobosy else had much of anything in production so comparisons become rather difficult.


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## pbehn (Jun 27, 2015)

I had this in mind when I made my previous posts.
German Jet Encounters
The second story does not give the type of detail preferred by members of the forum (it is a story) but it does describe the problem of matching cruising speeds. In this case mosquito bombers with P51 escorts unusually in this case the bombers best cruising speed was faster than the fighter at least at the start of the mission. Anyway all the boys got home so a good job all around.


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## GregP (Jun 27, 2015)

Well we had a slow day at the museum due to the fact that almost everyone was flying at airshows. But Seteven Hinton Jr. was there working on Voodoo and I asked him about WWII P-51 cruising speeds when escorting bombers and otherwise.

He grew up around the WWII aces, was raised in a P-51 or three, and is your current and six-time in a row National Champion in the Unlimied Gold racing class ... in P-51-based racers. His response was classic.

He said bomber escorts in P-51s and pretty much everything else flew around 190 - 220 mph until being bounced, seeing the enemy, or hearing about enemies in the same general area over the radio. So I was a bit optimistic when I said maybe 250 mph. He allowed they might push it up to 280 - 300 mph when alone, not escorting, and expecting combat, but otherise they'd fly 220 - 250 mph even when alone.

I asked about a close to 400 mph cruise at max continuous, which I understood was 42" and 2700 rpm. He said we must have been reading some unofficial manuals. He said max continuous is 42" and 2400 rpm and the stock WWII issue P-51 wasn't going to get aywhere NEAR 400 mph at that power.

This is coming from a guy who knows his way around stock as well as modified P-51s, and grew up with Bud Mahurin and other WWII aces ... who helped him solo and learn to fly P-51s.

Any argument for 400 mph fantasies falls on absolutely deaf ears here but again, in the interests of completeness, I will still ask the veterans yet again next weekend. I already know what they will say, and I suspect most of the forum readers in here already do, too. 

I'll check back in next weekend to post what I hear from direct questions of veterans who were there and flew the escort missions. They've been presenting there for more than 40 years, so the subject is already rather well known.

Sloooowwwwlllyy now Bill, get the 400 mph cruise out of your head.


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## Greyman (Jun 28, 2015)

Correct me if I'm wrong, but 'Cruising' means the engine settings which will allow continuous operation for an indefinite period (of course this can be further categorized up for maximum endurance, maximum range, different speeds, etc.).

For the purposes of comparing various cruise speeds to every other aircraft (which I think is what most of us are generally interested in here), it's unfair to the Mustang to pigeon-hole it and restrict the definition in its case to 'the speed at which it must escort bombers to Berlin and back'.


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## GregP (Jun 28, 2015)

Yes Greyman, Cruise power is NOT maximum continuous power, but COULD be ... it certainly is NOT when you are flying a long escort mission and time in the air is important. On shorter missions, say maybe Oct 1944 onward, the mission were getting shorter ... and thinga could change.

If there were not a war on, and if you weren't constrained by needing to fly a long distance, the P-51 is certainly capable of cruising in the mid-to-upper-mid 300s. That assumes the fuel burn and engine wear are acceptable and, in a war the engine wear is not a factor as the government CAN overhaul engines. The operative factor would be what the mission is. If you need to be ariborne for 7 - 8 hours, you are not flying at 380 - 400 mph in a P-51D with drop tanks on it. If you are escorting bombers you REALLY aren't cruising that fast or else you will never make the range required.

If the mission is 1200 miles and if your fighter flies twice as fast as the bombers ... but has to protect the bombers ... then your mission is 2400 miles while the bombers fly 1200 miles. Simple math, no surprises. The escorts didn't want to be flying 180 mph, but they also wanted to S-turn above the bombers, not fly in long ellipse-type circular paths.

If the P-51s were on a fighter sweep, they could cruise whereever the fuel they had would take them at the acceptable power selected. I they were clean, maybe 365 mph on a short mission. If they had tanks, bombs, both, or a longer mission ... no way. In Europe the weather is usually bad at certian times of the year, ay least for aircraft operations, and capable of being so any time. Nobody wanted to waste fuel he might need when returning due to weather. Fuel was an important factor.

The PLANE could probably do it, but there was no logical reason to go that fast on escort and no reason to court engine failure by cruising at high power levels beyond best-range cruise. Nobody with an ounce of brains wasted gasoline unless he had a reason. If he HAD the reason then yes, push it up as far as you want. Push it too far and join Colonel Hogan and Sargeant Schultz in Stalag 13 just from fuel exhaustion or engine failure. That ruins your day.

I do NOT question the P-51's ability to go fast when going fast was desired; it will and still does. I question the real-world decision to go fast when NOT needed and on the outbound leg of a long mission of any sort. Maybe if you HAVE the gas and are headed home and don't have to stay with the bombers because you picked up a relief squadron, then they might well get pretty fast to get back to the pub.

But if they hadn't seen an enemy fighter, they would not have dropped the tanks unless they were paper tanks. Metal tanks were a commodity you saved when you could. If not, well it WAS a war.

You know, maybe Stevo is mistaken and the veterans will say differently next week. Could be. I have been taken to task in here before for quoting the veterans who were there and will just ignore that going forward. In my opinion, they are the ONLY guys who KNOW, sort of like the Beatles are the ONLY people who know what went on in the back of their limosine. Everyone else is making assumptions that might be valid and might not be, including me.

So I could be off-base here and, if so, I'll admit it when I find out. Everyone makes mistakes including me, Bill (not often in my experience ... unfortunately for me), and anyone else. So, if I step in it, I'll own up to it, in here, and say I was wrong. It happens.

Bill seems to think I somehow have it in for him when I post something he disagrees with and he's mistaken. He is right most of the time and COULD be this time too. If so, the crow served up is mine, not his.

If anyone is interested, I added another couple of pics to the Planes of Fame Update thread. They had another week of polishing the Sabre ... and it shows. Our F-86F and MiG-15 bis are gone for 2 - 3 months on continuous airshow duty, so I can't update the paint and markings pics yet.


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## drgondog (Jun 28, 2015)

GregP said:


> Well we had a slow day at the museum due to the fact that almost everyone was flying at airshows. But Seteven Hinton Jr. was there working on Voodoo and I asked him about WWII P-51 cruising speeds when escorting bombers and otherwise.
> 
> He grew up around the WWII aces, was raised in a P-51 or three, and is your current and six-time in a row National Champion in the Unlimied Gold racing class ... in P-51-based racers. His response was classic.
> 
> ...



See the above - I sent Steve a Facebook PM ad will send Chris Fahey the same note.

Nothing derogatory on you - just what I explained to you multiple times so that he had the context of the questions, the reference and my suggestion that you may not know the difference between IAS and TAS

EDIT - my PM was to Steve Hinton, Sr as well as Chris Fahey another former F-16 driver that flys may shows with Steve Hinton Jr in either the Mig 15, the F-86, the P-51A, the P-51B and the P-38's. For what it is worth, Chris agrees the P-51B and D Operating Manual for Planning Tables as a 'Guide' but each pilot has a tendency to cruise at different altitudes -and RPM/Boost settings - to suit themselves. I haven't gotten a reply from Hinton, Sr but Chris will chat with SteveO when he gets back today from the Idaho air show and the F-86F to see what Steve 'heard'.


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## Shortround6 (Jun 28, 2015)

There seems to be a bit of confusion between _max cruise_ and _max continuous_. 

Max continuous was the _maximum_ amount of power the pilot was _supposed_ to use with an _unrestricted time limit_. The ONLY restrictions being engine temperature, oil temperature and running out of gas or oil. 

Max cruise is a little fuzzier, as in many instances, max cruise was also done at rich settings. It is subject to the same four restrictions as above and will give more range (in some cases, much more range).

Some planes had an "economical maximum" given on their charts which was the max power using _lean mixture_. 

And here we have another source of _possible_ confusion. Late P-51s had a 3 position control for mixture, idle cut-off, normal and rich. Early P-51Bs had 4 position control, idle cut-off, auto lean, auto rich and full rich. When the switch over between controls was made or if there ware one or more intermediate mixture controls. 
Were the pilots "cruising" using _lean_ or _normal_, were they actually the same? Or was the "normal" somewhere between auto lean and auto rich and the later "rich" equal to "full rich" ? 

talking to a veteran who flew a P-51B with the 4 position control on a V-1650-3 engine might give a different answer than a veteran who used the 3 position control on a V=1650-7 engine only a few months later.


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## drgondog (Jun 28, 2015)

Shortround6 said:


> There seems to be a bit of confusion between _max cruise_ and _max continuous_.
> 
> Max continuous was the _maximum_ amount of power the pilot was _supposed_ to use with an _unrestricted time limit_. The ONLY restrictions being engine temperature, oil temperature and running out of gas or oil.
> 
> ...



SR - the Mixture Control could be set at a Auto Rich or Auto Lean but the pilot was looking at the Manifold Pressure to fine tune any position while also adjusting RPM and Throttle - until satisfied - then lock those settings down. Everything within the span of your left paw... so it really didn't matter if there was a Full Rich notch past Auto Rich.

Depending on altitude and mission - the RPM at cruise for example could be from 1600RPM (say low speed, low burn for maximum loiter time) all the way to 2700 RPM and 46" for Normal Power Emergency Cruise.

The reason pilot recollections are all over the place is that they are flying all over the place from one mission to another - and the Pilot is trying to recall one mission long range and flying high cover at 30,000 feet, another is a fast cruise untethered by bomber escort, another is a low level fighter bomber sweep - but ALL will start with the Operating Manual that you posted 'way back' and be GUIDED by the altitude and mission range requirements.


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## Shortround6 (Jun 28, 2015)

Thank you, I didn't know if it made a difference or not.

Somewhere I had down loaded a Manual for a P-51B-1 but the flight charts are a mess. ALL the numbers are in red which usually means the numbers are calculated or estimated while black numbers mean they had been checked with flight tests. There are columns for IAS in MPH and IAS in Knots but they make no sense as the speed in knots is often higher than the speed in MPH. Unless they put the numbers for true air speed in the column labeled IAS Knots. 

For instance in Column II of the chart 2100rpm and 41 in at sea level is "supposed" to give 285mph IAS and 275 Knots IAS but at 3,000ft the same rpm, pressure and IAS on MPH is 285knots IAS (the same rather than 10 low) at 6,000ft the same rpm, pressure and same 285mph IAS is now 295 knots, at 9,000ft the 2100rpm/41in/285mph IAS combo is 310 knots. 12,000ft and 2200rpm/41in/290mph IAS is 330knots, at 15,000ft it gives 2250rpm/41in/295mph IAS for 350knots IAS and at 20,000ft 2500rpm/F.T/ 290mph IAS is 375 knots IAS. 

The rest of the charts are similar. 

This is from T.O. No. 01-60JD-1 and is dated July 1st 1943.


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## drgondog (Jun 28, 2015)

SR - the difference between TAS and IAS is a function of Pressure and Temperature which as you know changes nearly linearly from SL through ~ 37,000 feet (CRS). The density changes, the dynamic pressure changes with altitude. Look at the Charts and IAS = TAS at SL but at 25000 feet IAS on the instrument panel is 30% less that the True Airspeed at 25,000 feet.

On several Flight Tests validating the operations Planning entries in the manual, the actual and calculated and IAS TAS data are often in () to compare against the Charts.

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## jimh (Jul 1, 2015)

At 10,000ft in Betty Jane the following was noted:
36"MP 2,350rpm Normal Cruise IAS was 220kts 64gph auto lean (shadin fuel flow meter)
40"MP 2,500rpm High Cruise IAS was 235kts 72gph auto rich (there isn't much difference between 40" and 42")

I am running 40" 2,500 for doing loops with an entry speed of 270kts @3 1/2 - 4Gs . It is possible to do loops with a normal cruise power setting but it gets slow over the top. At 40" 2,500 it carries a bit more energy over the top with more control authority. On a normal day from 8,000ft it takes around 1,500ft of diving to attain 270kts. Through the backside and out of bottom of the loop at around 250kts you can zoom climb for about 20-30 seconds back up to 8,000 but the speed and energy diminish quickly. We do not run high power settings for acro. Some still do and the added inches of manifold pressure does help maintain momentum a little better than the 40" I use for vertical. We are running right around 7,500lbs so we are considerably lighter than a wartime airframe. hope this helps

jim


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## drgondog (Jul 1, 2015)

Thanks Jim. 

The warbird 'lite' versus the Manual 'heavy' does draw several important contrasts. I suspect that the fuel octane from late WWII also influences the nuances on cruise setting for max loiter, max range and Max Continuous from The P-51D operating Manual and Tables?


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## drgondog (Jul 1, 2015)

The P-51D 'book Tables' for racks only, 9600 pounds medium cruise settings is 2400/36" for 270IAS mph and 290Mph/252kts TAS at 10,000 feet. So reasonably close for to same performance you are flying for 7500 GW


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## GregP (Jul 5, 2015)

I said I’d check back in here when we had our “Little Friends” presentation and we had it today, so I’m back.

I asked the presenters how fast they cruised the P-51s in the Pacific both with and without bombers to escort, and whether or not they knew the same information about missions in the ETO. Not surprisingly, the subject had come up at the last meeting of WWII escort pilots a few weeks earlier.

According to three of our presenters, they cruised the P-51s (mostly P-51D’s) at 220 mph, which turned out to be somewhere around 29” – 30” and 1,700 – 1,900 rpm depending on configuration. Every hour for about 10 minutes, they’d run the engines up to 35” – 40” at 2,400 rpm and auto rich to make sure they didn’t foul the plugs, and then go back to 220 mph or so. They said that the P-51s in the ETO did pretty much the same or slight slower 190 – 210 mph or so, clearing the plugs for 10 minutes every hour before going back to lean cruise.

I asked about 320+ mph cruise and most laughed and said they'd never done that or heard of that. One asked if I was a video game player. I told them it was a question in a WWII aviation forum on the internet. The general consensus was that the only excuse for going over max continuous to clear the plugs was getting bounced or expecting imminent combat, and they’d rapidly go back to low cruise once things cleared away from combat.

So they pretty much said what they’ve said when this subject has come up before in past “Little Friends” presentation made by WWII combat veteran pilots of P-51s. However, this cloud might have a silver lining for both Bill and me. I didn’t specifically ask, so I made an assumption that they guys were talking IAS. Suppose they were flying at 20,000 feet at 220 mph IAS with an OAT correction of 2%. It turns out TAS would be 308 mph under those conditions. So it is possible that both Bill and I are right or wrong.

They almost certainly did NOT cruise at 300 + mph in P-51Ds if we are talking IAS, which I was talking, but they could be cruising in the low 300s TAS. I was talking IAS because that is all the pilot sees on his instrument panel. The 505 mph dive limit is IAS and it gets lower with altitude and the speeds in the handbook for IAS almost never approach the maximum.

So I can understand Bill’s 300 mph claim. But the pilots at our presentation from all theaters for the last 9 years I have been going and hearing the Q A have never supported seeing cruise speeds above about 250 mph and mostly not that fast. I never asked before about altitude, rpm, and MAP, but I’m sure that if they had a short mission, and pushed the cruise up to 260 mph IAS at 25,000 feet, they’d see somewhere around 390 mph TAS at 20,000 – 25,000 feet.

Nobody in the last 9 years had ever said they cruised at 260 mph (IAS), but I'll allow it was possible if you weren't going to escort someone a long way. I'm not sure any ETO bombers warranted cruising that fast, ever. I don't think P-51s escorted Mosquitos very often and the B-17, B-24 and Lancaster would not require cruising that fast even on their best days.

I think we’ve had some harsh words for nothing since I was always talking IAS. I can’t speak for Bill, but It is likely he was using TAS numbers from the charts.

This is as funny as the USAF saying the SR-71 goes Mach 3.0 at high altitude. The SR-71 could get to 2,000 mph TAS and, at high altitude, the speed of sound is 660 mph. 2,000 divided by 660 gives Mach 3.03 when you run the numbers, but the IAS is still about the same as the SR-71 sees at 10,000 feet and max speed since the same IAS generates the same heat or thereabouts. 850 mph IAS at 70,000 feet will give around 2,000 mph TAS or Mach 3.03 and that sounds a lot faster than 850 mph, doesn’t it? It's all about image.

The real WWII pilots never saw 380 mph cruise on the airspeed indicator and laugh when you bring it up. Really. NOBODY cruises at max possible speed on a long range mission. The two are incompatible with one another. Max cruise will NOT get you max range and the Breguet Range equation ain't all that far from wrong.

That's pretty much all I have to say on it. Not too interested any further since the P-51 veterans as well as current P-51 pilots, including some really quite qualified guys, say it didn't happened in service. But unless you're careful with your terminology, you can be both right and wrong when talking speeds.

I never bothered to flight plan TAS when flying a Cessna 172 because everyone at the FAA service center will laugh if you file a C-172 flight plan at Mach 0.17 ... I did it only once with Albuquerque Center and it made their day. They were laughing uproariously and I expected that. When I got to "souls on board," I also filed for "One plus an athiest" and got another round of laughter. But I got willing flight following that day since it broke up the boredom.


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## drgondog (Jul 5, 2015)

GregP said:


> I said I’d check back in here when we had our “Little Friends” presentation and we had it today, so I’m back.
> 
> I asked the presenters how fast they cruised the P-51s in the Pacific both with and without bombers to escort, and whether or not they knew the same information about missions in the ETO. Not surprisingly, the subject had come up at the last meeting of WWII escort pilots a few weeks earlier.
> 
> ...



You are trying way too hard to recover, Greg. If you had simply pulled out the Operating Manual used as the reference for my data and remarks - you might have figured it out earlier.

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## drgondog (Jul 5, 2015)

GregP said:


> Well we had a slow day at the museum due to the fact that almost everyone was flying at airshows. But Seteven Hinton Jr. was there working on Voodoo and I asked him about WWII P-51 cruising speeds when escorting bombers and otherwise.
> 
> He grew up around the WWII aces, was raised in a P-51 or three, and is your current and six-time in a row National Champion in the Unlimied Gold racing class ... in P-51-based racers. His response was classic.
> 
> ...



Can to find a mention of 400mph cruise in the context of a typical escort discussion at either 25000 or 30000 feet? Can you see a differentiation between IAS and TAS terminology? Do you see any such presentation to SteveO so that he understood what we were talking about?


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## GregP (Jul 5, 2015)

I didn;t reasd tyhi thread from Last Sunday until last night, so whatever you posted twp days agao, I didn't read. Considering teh way you say it, I won;t go back and do tyaht either. 

You apparently didn't read my post either, the guys answered for both escort and general flying when no escorting. They didn't even cruise at 260 IAS when alone, there being no point to going faster until necessary. Ad I very cealrly stated what Ia sked ... whichw as, "How fast did you crusie the P-51 when escorting bombers and when not flying escort?"

They all answered about 220 mph with 10 minutes in auto rich each hour to keeep the plugs from fouling.

So while tyhere might be a few people out tehre who did fly fast for a reason, tghey were cruising aorunf at 380 mph or 400 mph or whatever high speed you are touting. They werer cruising to save fuel, save the engines, and get the job done ... exactly as I said many pages back.

They didn't cruise that fast and all the writing in the world won't change tat fact. Go talk with the vets before they are all gone and LISTEN for a change.


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## jimh (Jul 5, 2015)

Yesterday, "zoom" climbing out of a loop back up to 11,500 from 8,000

And the day before I was flying the 24 and noted the cruise settings, you can see for yourself it's pretty slow










At altitude your true airspeed will be higher depending on temperature, air density and winds aloft. The bombers topped out at 200 no matter how you look at it...that's why the fighters flew an S pattern over top of them. A fully loaded mustang with drops would be lucky to get over 200IAS as well...indicated. Certainly no where near even 300TAS. 
Jim


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## drgondog (Jul 5, 2015)

GregP said:


> I didn;t reasd tyhi thread from Last Sunday until last night, so whatever you posted twp days agao, I didn't read. Considering teh way you say it, I won;t go back and do tyaht either.
> 
> You apparently didn't read my post either, the guys answered for both escort and general flying when no escorting. They didn't even cruise at 260 IAS when alone, there being no point to going faster until necessary. Ad I very cealrly stated what Ia sked ... whichw as, "How fast did you crusie the P-51 when escorting bombers and when not flying escort?"
> 
> ...



I don't know how old you are Greg - but I have been talking and listening to my father and his friends - and the friends I have made on my own since at least 1950 - which gives me 65 years of listening, researching, asking questions, researching, asking more questions and forming opinions based on what many of the best fighter pilots remember.

You still have yet to respond with Your versions/variances of the P-51D Operating Manual which departs from what I have stated/referenced, the reference document, the page numbers and the cruise values for the load outs and range conditions as well as altitude. You are non specific and wander between IA and TAS.You remind me a lot of Soren, when confronted. You get on a soapbox and grab a megaphone and recite chapter and verse of anecdotal recollections from people you don't name (except Steve Hinton Jr (SteveO) and then you contradict him with new references.

Settle this - trot out your numbers for a typical long range mission to Berlin with 75 gallon tanks.

When you quote your version, Pick a 1944 manual for P-51D Operations recommendations and state the RPM, IAS, Mixture, Manifold Pressure, Gallon per hour fuel rate and True airspeed for those settings.

Compare those with examples I presented on posts 31, 64, 76, 82, 91 and 92. and show how and where I was wrong and you were right.


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## jimh (Jul 5, 2015)

Never let reality get in the way of a good manual...I've flown quite a few WWII airplanes and they continually fall short of the book numbers. Even lightly loaded I am continually amazed they achieved the results they accomplished. I see and talk to veterans every day, and particularly the bomber crews, say every flight was marginal. Trade bombs for fuel or fuel for bombs. 

Jim

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## drgondog (Jul 5, 2015)

jimh said:


> Never let reality get in the way of a good manual...I've flown quite a few WWII airplanes and they continually fall short of the book numbers. Even lightly loaded I am continually amazed they achieved the results they accomplished. I see and talk to veterans every day, and particularly the bomber crews, say every flight was marginal. Trade bombs for fuel or fuel for bombs.
> 
> Jim



Jim - I know you are right. Having said that, the flight tests were flown to develop an Operating Guide for pilots new to the airframe and served as a Guide for planning purposes. If a particular ship or ships wasn't making a cruise speed by the book, a prudent mission commander adjusted accordingly.

I spent many hours listening and cross examining dad and his friends to 'try' to understand the variables before I got my degrees in Aero - then realized afterwards that it was all about 'It depends' as contrast with a hard throttle/rpm/MP as each airframe and engine was a different beast.

Simple question - when you were new to the 51 was the Operating Guide useful - or outdated because of different constraints imposed by severe financial penalties for running on the edge of the 'Book' recommendations and losing an engine or airframe? or tribal knowledge of the system after 70 years?


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## kool kitty89 (Jul 5, 2015)

Performance figures from tests of export/Lend-lease RAF/Commonwealth aircraft seem to be a bit more realistic for real-world performance compared to standard USAAF/USN test results applied to planning charts. (short of cases of operating out of spec -particularly overboosting, though that seems more common in ammended notes and such rather than actual recorded test figures)


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## drgondog (Jul 6, 2015)

Jim - I just noted your comment on 200IAS not 'being anywhere near 300TAS" - I wonder if you are thinking KTAS? 

at 25,000 feet, 200 mph IAS is 295mph TAS at standard Temp/Pressure. 
At 30K, 195mph IAS is 315mph TAS. 190-220 mph IAS is ~283mph to 323mph TAS 

A B-17 SOP cruise was 150mph IAS at 25,000 - which at STP is about 220mph TAS.

BTW I noticed on your panel that you were indicating about 156Kt - do you know when that airspeed indicator was put in your 51 to replace the standard airspeed gage? 

So, at 10,600 ft the 156KTS on your airspeed indicator, would be about 183kts TAS and about 210mph TAS at that moment in time

the 'Book' which serves only as a planning guides, sez that at 10,000 feet, racks only (I suspect you are totally clean) in the 8000-9000 pound GW state at take Off ( the higher weight with full aft tank and full mains, full ammo)

2400RPM, 270IAS(mph), 36", 73gpm, 315mph with good airframe and good engine. 
Reference P-51D-5 Operating Manual, 4/44 - page 54 for Column III range of 950 miles (intermediate condition )

So, roughly 'the Book' thinks that after getting back to 10K and back to steady level flight at your panel instrument readings of 2400RPM, 38"MP, and then reading ~ 234kts IAS? burning somewhere around 73 gph? for a calculated 317 mph TAS? 

Is that not close for those cruise settings?

Jim - How far off between your 51 and the 'Book'?


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## jimh (Jul 6, 2015)

Betty Jane was restored with a modern panel. At 10,000ft in level flight at 36" to 38" I indicate around 220kts at around 73gph. Next time I'm up I'll take some photos in cruise at various altitudes. It's a fun exercise with customers to show them the different performance curves. I meant 200mph, not knots...I've been flying her in kts for so long I really have to stop and think about which plane I'm in or what I am typing. 

I've found that the "Books" are good for the slower end of the envelope, stall/spin recovery, traffic pattern speeds, short field techniques, and aerobatic speeds. All those numbers are relevant. We run the combat cruise settings and get what we get. They were optimized numbers to prevent plug fouling and greatest endurance. If you fly around at 30" and below you are going foul plugs pretty quickly. 

The radials aren't as sensitive to that but we still run book numbers on the 24. The B-17 we run 40" for takeoff and 25" 1700 for cruise...simple because it is so light and has a great wing. 

The closest I've come to have performance match the book is the AT-6 and the B-25...they both are nearly spot on.

Jim


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## drgondog (Jul 6, 2015)

jimh said:


> Betty Jane was restored with a modern panel. At 10,000ft in level flight at 36" to 38" I indicate around 220kts at around 73gph. Next time I'm up I'll take some photos in cruise at various altitudes. It's a fun exercise with customers to show them the different performance curves. I meant 200mph, not knots...I've been flying her in kts for so long I really have to stop and think about which plane I'm in or what I am typing.
> 
> Thanks, Jim for those that remain confused about KTS, MPH and altitude adjustments
> "220kts Indicated" at 10K for IAS at 2400/38" is about 253mph IAS (on original instrument panel and about 296mph True Airspeed.
> ...



So, your experience in Betty Jane is 220kts IAS versus a table extraction of 234kts IAS at 10,000 feet. a Delta of 14Kts/16mph slower in today's Betty Jane than the 1944 Tables present for 10K, ~ 8500pounds GW at TO, 

270mph IAS (calculated Manual 235kts IAS vs Betty Jane actual = 220kts IAS), 2400RPM vs 2400 RPM, 38"MP vs 36 to 38"MP, 315mph TAS vs Betty Jane PROJECTED 301mph TAS.

Net difference between Manual and today's experiences w/Betty Jane is 14KTs Indicated and 15+mph TAS or about a 5% Delta Lower performance than the Book.

Thanks for taking the time, Jim


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## DerAdlerIstGelandet (Jul 15, 2015)

GregP said:


> They didn't cruise that fast and all the writing in the world won't change tat fact. Go talk with the vets before they are all gone and LISTEN for a change.



Considering Bill's father was a P-51 flyer, I think he has.

I think you are biting off more than you can chew and should take your own advise.

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## DerAdlerIstGelandet (Jul 19, 2015)

Cricket, cricket, cricket...


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## drgondog (Jul 20, 2015)

I think the various Cruise throttle, rpm and manifold pressure settings vs IAS vs TAS for various operational range planning scenarios has worked its course.

Everybody else has been in Oshkosh lately.

Jim H raised an interesting point regarding current Mustangs experiencing about 5% less actual cruise speeds at 10,000 feet than the P-51D manual posts for clean airframe and his airspeed indicator snapshots coupled with the manifold pressure and Tach and RPM confirms it for Betty Jane. As that P-51B is a Collings ship there is no notion that it is not getting world class maintenance.

I'm curious so I have asked a pilot friend at POF to run some comparisons in some of the 51's he flies to compare the 10,000 foot results at same or similar control settings.

So, to summarize:

The P-51D-5 Manual, Flight Operating Instructions, AN 01-60JE-1, dated April 1944, posts a setting that it defines as Maximum Continuous Power, and further states for Emergency Cruise only is:

2700RPM, Auto Rich, 46" MP. The various Ranges are cited for this setting with full internal fuel of 269 gallons, wing racks only (~ 6mph additional drag from clean) - 9600-8000 pounds GW -Page 54

No consideration for warm up, take off at MP, climb to altitude, or on the landing leg of the flight profile.
590 miles at 25000 feet *280mph IAS*, *410mph TAS*, 110 gph consumption 

518 miles at 10000 feet 305mph IAS. 355mph TAS, 108 gph consumption. 

With 75 gallon tanks 419 gallons fuel, GW= 10,700 to 9600.. 
1820 miles at 25000 feet 2200RPM *200mph IAS*, AL, FT,*295mph TAS*, 57mph ----------> Long Range escort 
1700 miles at 10000 feet 1750RPM 200mph IAS, AL, FT, 245mph TAS, 52gph

No tables for 110 gallon tanks as they weren't introduced until May 1944, nor were they flight tested until June to update the future Operating Instructions.


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## DSR T-888 (Jul 25, 2015)

Table V compares the diving performance of the P-51, P-47, F4U and Hellcat. I was actually surprised that the P-47 was able to out dive the P-51, even when starting at lower speeds. Wouldn't an aircraft that dives faster also zoom climb faster? 

http://a.moirier.free.fr/Essais en vol/Flight test comparison.pdf

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## drgondog (Jul 25, 2015)

DSR T-888 said:


> Table V compares the diving performance of the P-51, P-47, F4U and Hellcat. I was actually surprised that the P-47 was able to out dive the P-51, even when starting at lower speeds. Wouldn't an aircraft that dives faster also zoom climb faster?
> 
> http://a.moirier.free.fr/Essais en vol/Flight test comparison.pdf




It depends but in most cases of the initial phase of the recovery and climb - yes. The comparison between these two requires consideration for the differences in weight and drag as the zoom climb continues. The Mustang weighed less and had less drag but the P-47 had more Thrust Horsepower.

I wouldn't bet the farm on the evaluations. The use of 100LL instead of wartime 130 or even 150 octane limits the Mustang the most in these evaluations and I am mystified regarding the discussion of stick forces in the turn and reverse maneuver comparisons. You probably also noted that the dives were all at 30degrees - which would favor the heavier aircraft slightly and in no way pushes the test to Vne - The Mustang and P-47 were very close in terminal dive speeds but the Mustang's entry and recovery from Ncr were more benign.

As to the comments regarding the Mustang's handling characteristics in maneuver and marveling at its combat record despite the high stick forces? Guys like Zemke who flew the P-47, P-38 and P-51 in combat clearly favored the Mustang to fight with - citing its maneuverability, performance and range. He scored victories against the same enemy in all three aircraft.

As an aside, if you wish to explore another documented test comparisons of 125+ fighter and test pilots from Army, USN, USMC, RAF, NACA, and the manufacturers comparing all the top Allied Fighters - day and night both - then read the "Report of Joint Fighter Conference - NAS Patuxent River, MD 16-23 October, 1944". The aircraft tested and compared and ranked for Stability, Controllability, Performance, Armament, Cockpit, Power Plant and Protection. The aircraft included F4U-4C, P-47D-30, P-38L-5, F6F-5, F7F-1, XF8F-1, P-61A, P-51D-15, Mosquito, FG-1A, P-63, FM-2, XF2G-2, Zeke-52, Seafire


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## DSR T-888 (Jul 25, 2015)

drgondog said:


> It depends but in most cases of the initial phase of the recovery and climb - yes. The comparison between these two requires consideration for the differences in weight and drag as the zoom climb continues. The Mustang weighed less and had less drag but the P-47 had more Thrust Horsepower.
> 
> I wouldn't bet the farm on the evaluations. The use of 100LL instead of wartime 130 or even 150 octane limits the Mustang the most in these evaluations and I am mystified regarding the discussion of stick forces in the turn and reverse maneuver comparisons. You probably also noted that the dives were all at 30degrees - which would favor the heavier aircraft slightly and in no way pushes the test to Vne - The Mustang and P-47 were very close in terminal dive speeds but the Mustang's entry and recovery from Ncr were more benign.
> 
> ...



I'm still learning, that's why I made this account.

I do enjoy reading a lot of your comments drgondog.


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## DSR T-888 (Jul 25, 2015)

Here are some Immelmanns and Split S's comparing the P-47D(light blue) and P-47N(Blue) 

http://i.imgur.com/8BUoBWL.png
http://i.imgur.com/PsnNRXD.png
http://i.imgur.com/x2kOs4n.png
http://i.imgur.com/Ghb5NyM.png


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## drgondog (Jul 26, 2015)

DSR T-888 said:


> I'm still learning, that's why I made this account.
> 
> I do enjoy reading a lot of your comments drgondog.



I'm curious of how the 30 degree angle dive would favour the heavier aircraft. Recovery from nearly hitting compressibility? The P-47D-30s and above had dive recover flaps installed. Pulling out is much more physically demanding on the P-51 compared to the P-47 or any other allied fighter. What is Ncr?

*The force of gravity is acting on all aircraft. In level flight the weight of the a/c is equally offset by the Lift, but contributes zero to the longitudinal axis (X)in line with the propeller thrust. As the a/c noses over the Weight force vector in the vertical plane of reference (Z)diminishes as W'COS (dive Angle) and the Weight Force vector increases from Zero along the X axis as SIN (dive angle) As the a/c noses. In a full 90 degree 1g dive (trimmed), there is no effective lift vector and all the Weight contributes to the Thrust vector. The case for climb is just the opposite as in climb the Weight Vector aligned with the thrust axis is working Against the Propeller Thrust.

Net - all things equal (T, D), the heavier ship will tend to out accelerate the lighter ship in a dive and under perform in a climb. * 

What was Zemke's preferred dog fighting style? Just by doing some quick research he did exploit the P-47's strengths of BNZ. Pilots like Erich Hartmann seemed to prefer the style of "Boom 'N' Zoom", He said in an interview that he'd only attack if he had 2000 meters of clearance above the enemy. I can only imagine a plane with lighter stick forces and greater firepower would favour this roll. Possibly a dog-fighting roll would favour the P-51 due to its greater acceleration and turning capabilities. From what I can find on the P-38, obviously depending on the variant of which he flew. The P-38 could turn a slightly tighter radius and could roll faster than the P-51. I'm making the assumption that he probably favoured the P-51 over the P-38 because of its superior visibility.

*I suspect that all pilots that spot an enemy first will first seek a tactical advantage such as altitude and position (out of sun, blind spot, etc) but every fighter pilot that saw a lot of combat and encounters would have to deal with situations not favorable to them. Zemke for example was almost shot down by Krupinski (Not Rall) on May 12, who was attacking Zemke with a 5000 foot altitude advantage in a BnZ manner. He avoided the attacks but both his wingmen were shot down. Zemke then shot down a 109 up north of that location by simply sneaking up from six o'clock. In other words tactics were a combination of a.) planning and b.) desperation.

Every fighter pilot I know or have known over the last 65 of my 70 years knew the strengths and weaknesses of his aircraft and the enemy he fought as well as 'what Not to do' when caught at a disadvantage.

The P-38 when it employed the maneuver flaps of the P-38J-25 and all P-38L's could slightly out turn a Mustang (or a 109 or a FW 190). Correspondingly it lost energy faster because of the major drag penalty of a P-38 compared to P-51. Secondly, the P-38 could out roll a Mustang with the following caveat. Despite the roll rate due to boosted ailerons - it was Not and 'instantaneous' roll response. That was a HUGE fighter with a lot of roll inertia due to the outward locations of the engines.

The Fighter Conference notes on the P-38 spent a lot of time discussing the "Yes, but.." nature of initiating the turn with control yoke... and waiting, waiting - before the Roll was actually occurring.
It would slightly out accelerate and slightly out climb the comparable Mustang series by developing twice as much Hp to overcome the drag (until 130/150 octane was available to increase the 1650-7 boost from 67 to 72/75" in WEP). 

Look also to the same comments recaptured in America's One Hundred Thousand" by Dean.

IMO the P-38 primarily failed to achieve expected results in the ETO for three reasons:
First is was easy to see and identify, giving an opponent with an equally performing aircraft a Major advantage of being able to see it first and plan accordingly. 

Second, the intercooler and Turbocharger design was flawed for high altitude operations in the ETO until the J-15 was introduced in March 1944. Engine and turbo failures abounded.

Last but not least is that a FW 190 and Bf 109 easily out dove it because the P-38 at high cruise at 25000 feet was cruising only 10% under onset compressibility and almost immediately went into critical Mach compressibility when it pushed over. The shock wave developed and changed the Center of Pressure aft causing a nose down pitching moment, and the fully developed boundary layer separation tended to cause major turbulence immersing the elevator - all these factors made it impossible to pull out of a dive until much denser air was reached at lower altitudes.

Mcr is Mach Critical Velocity at which point a fully developed shock wave forms. A classic airfoil design of the period had the maximum T/C at 25% and the Center of Pressure near that point on the wing cord - whereas the Mustang max T/c was at ~45% and the CP near that point. As the velocities increase from leading edge on the 23xxx or similar (for F4U, F6F, FW 190, P-38, P-47) airfoils, there is a steeper velocity gradient from leading edge to peak velocity at 25% chord than the velocity profile for the NAA/NACA 45-001 laminar flow airfoil on the P-51 - causing the Mcr Compressibility shock wave to start at a higher velocity - for equivalent thickness of the wing. The P-47, Bf 109 and Spit had 'thinner' wings which also delays onset compressibility but not as much as the laminar profile achieves. 


The Mcr of the Mustang was closer to .75-.8M and the movement of the CP was not so nearly dramatic as to cause a severe nose down pitching moment. NAA actually designed a Dive flap for the P-51D (similar to P-47D-30) but NACA decided after testing that it was not needed.*


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