Diving - which fighters used it best, and how?

CobberKane · Oct 8, 2012

In most discussions concerning manoeuvrability, rate of turn and roll rules and diving is just something to do when there is a Zero on your tail. The diving ability of the P-47 Thunderbolt was proverbial, yet RAE tests indicated that the P-51 Mustang could dive faster and the highest speed ever attained by a piston engine aircraft was in a Spitfire. So what made a good diver; controllability, acceleration or outright speed? And what WWII fighters used diving most effectively against their opponents, and how?

ShVAK · Oct 8, 2012

Acceleration + firepower, with the ability to easily pull up or roll out.

The P-47 may not have been as fast downhill in terms of absolute speed as the P-51 or Spitfire but from pilots' accounts it seems like it got to Vmax faster. You didn't want to see a Jug bearing down on you hard with all eight .50's blazing. Plus it had a very good roll rate and the structural integrity to easily handle a 420+ mph dive.

wuzak · Oct 8, 2012

Acceleration in the dive is definitely the key.

The P-51B accelerated away from the Spitfire IX, providing one of its advantages in a duel between the pair. But there was much less advantage over a Spitfire XIV.

I think the P-47 worked well in (the initial stages of) the dive because of the same reason it wasn't a very good climber - gravity!

CobberKane · Oct 9, 2012

I think both the above comments are on the ball – acceleration and control at high speed are at least as important as outright speed in diving. I suspect the P-47 excelled in both these areas. The RAE found that both the Fw190 and Bf109 could dive at higher speeds that the Thunderbolt, but I've also read an account from a German pilot who described the 190 as 'inferior beyond all hope in the dive' as compared to the P-47.
One other factor to consider is the inverse of the dive, the zoom climb. The Tempest was apparently excellent in this area and frequently able turn an initial altitude disadvantage into and advantage by drawing the attacking fighter into a dive, then zooming and coming out above the opposing fighter.

MikeGazdik · Oct 9, 2012

I think the reason the P-47, as told by the pilots that flew it and against it in combat, talk about its incredible dive is energy. Though technically when tested by test pilots other planes could go faster, the Thunderbolt because of its own weight kept the energy from the dive and was able to convert it into climb. That and possibly because it had a better feel at those high speeds, giving the average pilot the confidence in his airplane. To a lesser extent, that may also explain the perception about the P-40 versus primarily the Japanese aircraft. It was much heavier and was able to retain its energy from the dive. Kind of like a heavier bullet retaining more energy down range than a lighter bullet.

CobberKane · Oct 9, 2012

MikeGazdik said:
I think the reason the P-47, as told by the pilots that flew it and against it in combat, talk about its incredible dive is energy. Though technically when tested by test pilots other planes could go faster, the Thunderbolt because of its own weight kept the energy from the dive and was able to convert it into climb. That and possibly because it had a better feel at those high speeds, giving the average pilot the confidence in his airplane. To a lesser extent, that may also explain the perception about the P-40 versus primarily the Japanese aircraft. It was much heavier and was able to retain its energy from the dive. Kind of like a heavier bullet retaining more energy down range than a lighter bullet.

The P 47 also had an excellent reputation as a formation flyer. Because of the drag created by its radial engine, any decrease in throttle resulted in immediate de-accelaration, making it much easier to make small adjustments in speed compared to fighters like Spitfires and Mustangs. The sleeker, LC engine fighters tended to coast when the throttle was chopped and took much londer to slow. I guess the drag of the P 47 was a bit like engine braking in a car. I wonder if this characteristic of the P47 was also a help in the dive, enabling the pilot to more easily manouvuer according to what the aircraft he was pursuing did, although it may also have affected the zoom climb negatively compared to LC fighters that also dived well.

drgondog · Oct 9, 2012

Cobber - do you happen to have the RAE report that concluded that the Fw 190 and Bf 109 dove at a higher velocity than the P-47?

meatloaf109 · Oct 9, 2012

And on the other side of the world, Claire Chennault taught his pilots to use the superior diving traits of the P-40 to best the Emperor's air force.

Timppa · Oct 9, 2012

From:
Comparative Performance of Fighter Aircraft

GregP · Oct 9, 2012

The myth that the P-47 wasn't a good climber was initially true when the narrow-chord props were used. Once they put on wide-chord props, the P-47 was still down a bit in low-altitude climb, but handily out-climbed many fighters at medium and especially high altitude. It was probably one of the best at 28,000 to 35,000 feet, right where many of them spent time on escort missions. Couple that with very good roll and you have a formidable escort aircraft.

davebender · Oct 9, 2012

I agree.

You want to accelerate quickly into a high speed diving pass followed by a zoom climb to regain superior altitude. An aircraft with superior climb makes this a lot easier.

Erich Hartmann was master of the of the dive zoom. The Me-109G had great dive, climb, acceleration and firepower. A match made in heaven (from the Luftwaffe perspective).

msxyz · Oct 9, 2012

Macchi c.200 and c.202 were very fast divers and always gained recognition for this.

Some sources say speeds as high as 1000 km/h were obtained in a step dive at altitude, although the airspeed readings of the instruments of the era weren't accurate once they approached the high subsonic region. Even the designer of the c.200/2 had always been suspicious of the figures reported by the test pilots and deduced correctly that the instruments weren't returning accurate readings past certain speeds.

drgondog · Oct 9, 2012

Compressibility starts at ~ .3M, Drag Divergence begins antwhere from .59 to .65 for nearly all well designed airframes and stagnation pressures on pitot tubes well below that become unreliable. No way did Macchi 202 come close to 1000km/hr, and certainly not with wings and eppenage still attached to airframe.

CobberKane · Oct 9, 2012

drgondog said:
Cobber - do you happen to have the RAE report that concluded that the Fw 190 and Bf 109 dove at a higher velocity than the P-47?

From recollection the information comes from Eric Browns book 'Wings on my Sleeve'. Brown said th RAE tested the P38, P47 and P51. I think the figures for critical dive speed for the thee fighters were; P38 and P47, mach .72 and P51 mach .78. That put the P51 on par with contemporary 109s and 190s and the P47 and P38 a bit behind.
I think the highest figure the RAE ever got was mach .82 for a Spitfire, but the plane lost its prop and its wing were bent back in the process, though it still landed. I guess the effective critical dive speed probably would have been no more than the P 51.

wuzak · Oct 9, 2012

GregP said:
The myth that the P-47 wasn't a good climber was initially true when the narrow-chord props were used. Once they put on wide-chord props, the P-47 was still down a bit in low-altitude climb, but handily out-climbed many fighters at medium and especially high altitude. It was probably one of the best at 28,000 to 35,000 feet, right where many of them spent time on escort missions. Couple that with very good roll and you have a formidable escort aircraft.

It depends what you compare it with.

Compared to the earlier versions with standard props the paddle blade prop versions look like stellar climbers, but how do they compare to known good climbers?

The Spitfire XIV has 1000+ ft/min better climb at sea level than the P-47M, which appears to be the best climbing P-47, and still matches the climb at 32,000ft. Can't tell you above that.

CobberKane · Oct 9, 2012

GregP said:
The myth that the P-47 wasn't a good climber was initially true when the narrow-chord props were used. Once they put on wide-chord props, the P-47 was still down a bit in low-altitude climb, but handily out-climbed many fighters at medium and especially high altitude. It was probably one of the best at 28,000 to 35,000 feet, right where many of them spent time on escort missions. Couple that with very good roll and you have a formidable escort aircraft.

The pre-paddlepop prop P 47 (say that fast five times!) certainly had a reputation as a poor climber, at least at low to medium/high altitudes. The D models apparently improved markedly in this respect, although I agree with WuzaK (shock, horror!) that's its questionable whether they matched dedicated climbers like the 109K or Spit XIV at any altitude. But then as an escort fighter they didn't really have to, I guess. The Thunderbolts could fly above the bombers, which was where the German fighters had to go, and intercept by doing what they did best – diving.
One other thing - didn't the later P47 have dive flaps, like the P38L? But the P-51 didn't - was this a reflection of the Mustangs higher critical mach number and therefore contrallbility at higher dive speeds than the other two fighters?

wuzak · Oct 9, 2012

Controlability is different to critical mach number. Though I believe they could be related - part of the issue for P-38s in dives was due to compressibility causing buffeting of the elevator.

Yes, Cobber, this is the second thing in which we are in agreement. The other is that the Wallabies are crap.

wuzak · Oct 9, 2012

CobberKane said:
I think the highest figure the RAE ever got was mach .82 for a Spitfire, but the plane lost its prop and its wing were bent back in the process, though it still landed. I guess the effective critical dive speed probably would have been no more than the P 51.

Beginning in late 1943, high-speed diving trials were undertaken at Farnborough to investigate the handling characteristics of aircraft travelling at speeds near the sound barrier (i.e., the onset of compressibility effects). Because it had the highest limiting Mach number of any aircraft at that time, a Spitfire XI was chosen to take part in these trials. Due to the high altitudes necessary for these dives, a fully feathering Rotol propeller was fitted to prevent overspeeding. It was during these trials that EN409, flown by Squadron Leader J. R. Tobin, reached 606 mph (975 km/h, Mach 0.891) in a 45° dive. In April 1944, the same aircraft suffered engine failure in another dive while being flown by Squadron Leader Anthony F. Martindale, RAFVR, when the propeller and reduction gear broke off. Martindale successfully glided the Spitfire 20 mi (32 km) back to the airfield and landed safely. Martindale was awarded the Air Force Cross for his exploits.

A Spitfire was modified by the RAE for high speed testing of the stabilator (then known as the "flying tail") of the Miles M.52 supersonic research aircraft. RAE test pilot Eric Brown stated that he tested this successfully during October and November 1944, attaining Mach 0.86 in a dive

Supermarine Spitfire - Wikipedia, the free encyclopedia

wuzak · Oct 9, 2012

CobberKane · Oct 9, 2012

wuzak said:
Supermarine Spitfire - Wikipedia, the free encyclopedia

That's a crazy speed for a piston engine aircraft. Brown said the only other fighter of the war to match that dive speed was the ME262, though is did so at a much more shallow angle of course. In any case experience with the P 47 suggests that that outright speed in the dive is secondary to acceleration in defining what makes a fighter a good 'diver' from the combat pilots point of view. I wonder if another big factor is rate of roll. For a fighter to dive it must first roll 180 degrees, and the faster this occurs the less time there will be for a) a target at lower altitude to escape, or b) an attacker to catch you before you dive away. I believe one of the few advantages the Spitfire V had over the Fw190A was an ability to pull away in extended dives, yet a typical escape for the 190 when attacked by the Spitfire was to roll and dive, because its superior roll rate mean it would be esablished on the desired plane and entering the dive while the spitfire was still playing catch up behind it.

Perhaps a 'good diver' is a plane that can:
1. roll quicky
2. accelerate quicly in the dive
3. remain controllable
4. have a good zoom climb.

With outright speed in the dive being secondary to these factors, so long as it was at least competitive

Diving - which fighters used it best, and how?

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