Zoom climb

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

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.

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.

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.

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.

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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.

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.

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.

Shortround6 said:

Yes, that was with drop tanks.

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

View attachment 295404

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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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 cruise@100 gallons per hour
25K 110 Gallon 371mph cruise@89 gallons per hour
25K 500# Bombs 357mph cruise@100 gallons per hour
25K 250# Bombs 381mph cruise@92 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 for25K 110 gallon tanks 303mph@57 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.

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.

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.

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:
67" 375TAS at SL, 438 at 25,000 and 442 at 26,000. For 61" 363mph at SL, 428mph at 25,000 and 438mph at 28,000. All flights fully loaded except fuselage tank at 9760 pounds GTOW, with racks - before installing 110 gallon, 500 pound and 250 pound bombs.

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.

True but they were greater than you thought, and in one case the Military Power 61" achieved 438mph at 28,000 feet.

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.

True also except Military Power at 61"/3000 RPM was nearly as fast in the 20,000+ feet ranges as WEP

Maximum continuous cruise power was about 42" at 2,400 rpm.

Normal Rated Power in the P51D during WWII for -3,-7 and -9 was at 46" 2700 RPM. But it is not stated which fuel type was used in US for these tests.

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.

The Warbird experiences and practices do not equate to WWII combat operations, nor do the relevant fuel types but your comments do reflect both the $$$ issues and the FAA regulatory stranglehold on Warbird operations

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.

Actually just the opposite. The worst sin was being late for R/V and finding the bombers undefended and under attack. The cruise to the target was one slightly above optimal Miles per gallon but still getting there at 220-230 IAS at 25K which translated to 310-330 mph TAS with 110 gallon tanks. That was achieved at 2400RPM/39" for 331mph and 4.49 miles/gallon - then slow down to 2250RPM/32" for 281mph TAS at 4,01 miles per gallon - for conventional multi box escort practice. For Sweeps at intermediate ranges like Brunswick/Friedrichshafen/Schweinfurt they might do 2700RPM/46" for 357mph and 3.58 miles per gallon. That would permit warm up, Take off, climb at Normal Rated Power to 25,000 feet then a run of 500+ miles before punching the tanks... and burn off 30 gallons of the fuselage tank for more or as a reserve for loitering.

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.

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.

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.

SOP was always full internal fuel - no matter what the Intended mission - simply because many missions were conducted by Beachy Head or Type 16 Controllers helping you look for business and they vectored you until you waved off and turned for home. This true for Patrols and particularly true for Normandy Campaign and Bulge over the near continent.

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.

Click to expand...

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

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.

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.

GregP said:

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

Click to expand...

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?

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.

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.

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.

Didn't say they did - you were the one that set the table by stating that the P-51D's top speed was 437mph. I pointed out that this was not true by flight test and pointed out the Test Report for the data, including achieving 438 at 61" Military Power.

As to the cruise data? the speed figures and throttle settings and RPM were 'book' SOP. The mile per gallon figures might not be achieved for an older airframe that was not taken care of, or an engine that wasn't running to specs. But crew chiefs were not as sloppy or stupid as you seem to think - that they would let THEIR pilot fly in a substandard airframe/engine combination if parts and engines were available. Since a lot of the discussion has been about the ETO, the parts WERE available to keep the engines at or close to spec. Having said that - some airframes were better than others, ditto the engines. Neither condition detracts from the SOP and the general performances which Should be expected for combat operational P-51D's. Something you may or may not know is that when the rare airframe exceeded 700 hours, it was often declared WW and didn't fly missions. How is That compared to Warbirds? Would you propose that the Warbird today receives better maintenance (except for polishing the airframe)than an operational Mustang which has free parts, factory new, free engines rebuilt to spec or brand new and maintained by a professional with great pride at keeping his pilot alive?

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.

Greg - older and less subject to weather than the P-51D-15 (tested with racks) named in the Flight test for June 15, 1945? The one that rolled off the NAA line in late August 1944 ten months earlier? That 'factory test Mustang' that was flown continuously for at least 9 months? It may have escaped your attention how many fighters (use my father's as an example) had names like Jane, Jane II, Jane III, Jane IV, Jane V, Jane VI, Jane VII in 10 months? Has it occurred to you that new fighters replaced 'old' fighters in weeks in many cases because of battle damage or loss - or that test aircraft lingered for the entire wartime service at Wright Pat or Eglin without replacement - such as the XP-51's at Wright Pat and NACA?

Your thesis of 'old, run down, junk heaps' is silly, Greg. Those, if they survived that long became WW or hanger queens.

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. (The data presented in the OM and the Test report are with racks - and the data (obviously for 110 gallon tanks are with 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.

Personal anecdotes are irrelevant to the discussion Greg. How you ask the questions and how you probe the differences from the recollections will give you hidden jewels of insight. Have you, for example set the table with " The Operating Manual sez This for best cruise range - is that what you did, and if not what did you do and why?

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.

BTW 'getting to Berlin and back' was a long but not That long. Most of dad's missions to Berlin and Magdeburg were ~ 5 hours compared to Kiev at 7:45. Munich/Ruhland averaged 6 hours when the Group picked up the bombers about 2/3 of the way, but a slightly shorter distance sweep to Halle/Merseburg/Leipzig was a little over 4. These are not 'anecdotal' data. BTW do the math on Leipzig - nearly 1200 miles in four hours including warm up, take off, forming up and climbing to altitude- approximately 45 minutes between 200 and 160mph.

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 numbers I presented were testing the Manual, Greg - did you miss that point?

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

Click to expand...

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

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

GregP said:

Here's another try at logic ...

Oh, dear - please have patience with me as I try to follow you.

Let's look at this from a planning point of view. Nevermind startup, taxi, takeoff, and forming up,That little exercise uses nearly 10% of your internal fuel before switching to externals a B-17 normally cruised at about 185 mph See, you already left me. The SOP for 25000 feet was 150IAS and about 205mph TAS.. 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.

you have to correct your TAS in this example but your 'logic' will approximate the flight time in formation at altitude

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.

The data to plan such a mission - such as recon - is available however, and presented for you below for a mission of 4.89 hours an 1835 mile averaging 375mph using your assumptions but not escorting bombers

So - you are the only one talking about flying escort missions at Max Continuous Power. What I presented were the table data which shows a variety of airspeeds and fuel consumption - and settling on the min fuel consumption to illustrate the difference between 370mph cruise at 100 gph for 3.58 mpg and the 'normal' 281mph at 57 gph for 4.91 mpg (from memory) for a very long mission. The Operation choices were made by the Group Leader based on the mission for 110 gallon externals.

By the way Greg, Range performance estimation is standard fare for multiple mission profiles is standard fare in undergrad school - I can recommend some books if you wish, particularly in the AIAA series on Design

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.

Silly statement Greg. Essing was the common practice for close escort. It enabled the much higher cruise speed (anywhere from 280 to 310 mph - depending on the drain down of the external fuel in 110 gallon externals

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.

And your point is? See above and Shortround's comments to illustrate our confusion. The question, Greg, is COULD a P-51 cruise Continuously at 380 mph? And the answer (follow the logic) is YES. When you place a MISSION REQUIREMENT of 380 mph (Minimum) AND a Combat Radius of 500 miles - it won't work Greg. Neither I nor SR need to look at the tables to KNOW that. Having said that - use your own logic path. Start at altitude and start with full 489 gallons of fuel.

Cruise at 357mph with 110 gallon externals at Max Continuous Power 2700RPM, 46" MP @100gph = 2.2 hours x357 miles = 785 miles before dropping tanks ----------> 269 gallons remaining (your logical approach to simplify the problem - let us pretend it is a long range recon - go deep, go fast and return.)

Turn around and cruise at 404 mph with external racks but no tanks at MCP 46"/2700RPM @100 gph = 404x 2.69 hours = 1050miles the other way. Without burning up the engine....

Ridiculous profile with no reserve for WU, TO, form up, climb - fight - return, loiter and land, but here you are.

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.

True - so you cruise faster for the same burn rate at 25000 than you do at 10000..

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.

That would be an escort mission (with RV perhaps short of Berlin - then to target and R/V with another Mustang Group west of Berlin) to Stettin or Brux and back, but continue

Well, using your crisp logic as outlined above for a NON escort mission - the mission would fly 1835 miles in 4.89 hours before zero fuelfor 46" MP and 2700 RPM

at 357mph for 2.2 hours and 404mph (TAS) for 2.69 hours.. couldn't take off, couldn't escort, couldn't fight but it could go a LOOOOOOONG way on 469 gallons, Max Continuous Power, and average 375mph - not very far away from the posed thesis, is it?

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.

Well, about 50% of what you just wrote about a typical escort scenario is data based fact. About 50% of the facts you hypothesized are wrong making a rebuttal a long windy waste of time.

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.

Greg - I can, and have done the mission profile perhaps 50 times over the years - directed at you in debates like F6F or F4U and Spitfire - to illustrate why they couldn't do any better than the P-47 in ETO. Your narrative is offensive but incorrect. I'll take the last comment about where the relief occurs. By historical Fact, relief/RV point (inbound and outbound) was anywhere from Holland to Berlin, all the way to Gardelegen just east of Berlin, or Augsburg just north of Munich depending on the variables - (i.e. are P-51s relieving P-38s or P-47s or P-51s? If the 190s and 109s are attacking, at the R/V point then they are idiots or unlucky because the defending force size is twice what it would have been earlier or later.

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.

Greg, you are so dramatic when you are on a soapbox

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

Click to expand...

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'

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.