Zoom climb

[grampi]

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?

 

[Greyman]

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.

 

[Shortround6]

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.

 

[GregP]

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.

 

[davebender]

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.

 

[Greyman]

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.

 

[grampi]

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.

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...

 

[Mike Williams]

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.

 

[GregP]

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 ...

 

[Conslaw]

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.

 

[GregP]

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.

 

[grampi]

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.

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...

 

[Greyman]

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.

 

[Shortround6]

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.

 

[grampi]

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?

 

[Shortround6]

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.

 

[pbehn]

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.

 

[GregP]

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.

 

[pbehn]

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.

 

[kool kitty89]

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.