P38 Roll Delay Revisited

[Bullethead]

Gruppen-

Some months ago, somebody brought up a theory that P38s had a delay of a couple of seconds between pulling the stick over and the plane starting to roll.  I'd never heard of this but could see perhaps a reason that it could happen.  Still, I wanted to ask some old P38 pilots I know if that really was the case.

Well, I've finally tracked the old guys down and gotten their answers.  According to them, there was no delay at all between stick movement and the start of the roll.  In fact, they said the P38 was very responsive to all controls, but it was just that it's roll rate was lower than most of the competition.

NOTE:  these guys flew the older models without the powered ailerons.

[mos]

I've never noticed a delay unless I'm compressing, at which point I can only roll after the stick is pushed to the extremes and I'm in a denser air layer.  Under "normal" flight conditions, the p38 has a great roll rate, especially at high speeds.

[Manedew]

did you find out weather they had the advantage of the later model- power airleions ... p-38 was only WWII fighter with such airleions i think....  maybe the earlier models had this delay but was fixed by the J and L models ....  

not entirely sure, but think the J was the first to have it along with dive flaps?  But something you may want to consider

[Ack-Ack]

Originally posted by Manedew
did you find out weather they had the advantage of the later model- power airleions ... p-38 was only WWII fighter with such airleions i think....  maybe the earlier models had this delay but was fixed by the J and L models ....  

not entirely sure, but think the J was the first to have it along with dive flaps?  But something you may want to consider

I think the J models equipped with dive flaps and hydraulic boosted ailerons (models J-25 through M) came out around the same time as the L model, since the late J series were retrofitted with the improvements incorporated in the L model.  Widewing or Savage can probably give a better time line.

I asked Earl (ex-WW2 P-38G, P-47 and P-39 pilot) a similiar question awhile back and to the best of his recollections, he stated that he didn't notice a lag between moving the controls and the plane starting to roll unless it was at very speed but he did mention that at low speeds it was very slow on the roll and needed quite a bit of rudder input.  But that the normal speeds he flew it, the controls were crisp and the plane extremely responsive.

Watching the old WW2 P-38 flight training film on Zeno's site, even they mention the crisp and responsive flight controls and also in Jeff Ethel's article and video on flying the P-38, he mentions the same thing.


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[popeye]

In _America's Hundred Thousand_, author Howard Dean writes, "The P-38 was a large heavy fighter not suited for quick 'snap' or 'slam-bang' maneuvers, and had a particularly slow initial resonse in roll due to a high lateral inertia characteristic.  The problem was a slow start into a roll and thus an inability to switch quickly from one attitude to another, as in reversing from a turn in one direction to one in the other.  As one pilot said, 'It was disconcerting to have a fighter barreling in on you, crank the wheel over hard, and just have the P-38 sit there.  Then after it slowly rolled the first five or ten degrees of bank it would turn quickly, but the hesitation was sweat-producing.'  Many combat losses, particularly in North Africa, were attributed to this creaky initial rate of roll.  Another pilot noted, 'The first ten degrees of bank came slowly'.  (pg. 160)

Apparently, there were some pilots who felt the initial roll was slow compared to other fighters.

[Ack-Ack]

I wonder if those were older P-38 models they were talking about.  The roll rates were significantly improved with the J25-LO series and P-38L.

Captain Stan Richardson comments on the slow initial roll rate of the early P-38H and J models deployed with the 8th Air Force.

"The P-38 was a large fighter with much mass. 52' wingspan and long, wide-chord ailerons contributed to slow response along the longitudinal axis of the early airplanes. The higher the indicated airspeed, the slower the response. At very high IAS it took plenty of muscle to roll the airplane. I don't believe that a joystick would have improved matters over the wheel. The Luftwaffe soon recognized the slow roll rate of the "H" and early "J" model Lightnings and used it to their advantage. It also learned of the dive restrictions caused by "compressibility" and used that advantage also.

Sometime in the development of the P-38, the design engineers must have realized that P-38's didn't have great roll capability. When Tony Levier, Lockheed test pilot, visited the 55th FG, he heard a common thread of complaints from the pilots. Cold cockpit, poor "flick" roll rate, and inability to dive after the Bf-109's and FW-190's from high altitude.

The complaints were relayed to the Lockheed factory, and design changes were incorporated in the P-38L. Prior to the arrival of the "L's" at Wormingford, many modification kits were shipped to Langford Lodge, North Ireland, for field modifications of the "J" model Lightning then arriving in the theater. Unfortunately, an early shipment aboard a DC-4 was lost at sea when the Brits shot the cargo plane from the sky. It took several months to replace the lost modification kits. Early P-38J-5-LO's were modified at Langford Lodge by the addition of the replacement kits. The kits added dive recovery flaps under the wings, outboard of the engines, and a 3000psi hydraulically boosted aileron system. The P-38L's were now coming down the production line with the aileron boost and "speed boards" installed.

P-38's from the J-25's onward were what we should have had when we went operational in October 1943. The compressibility problem of the P-38 was also experienced by P-47 Thunderbolts, and was not a mystery to aeronautical design engineers.

The P-38J25-LO and P-38L's were terrific. Roll Rate? Ha! Nothing would roll faster. The dive recovery flaps ameliorated the "compressibility" (Mach limitation) of earlier Lightnings. An added benefit of the dive recovery flaps was their ability to pitch the nose 10-20 degrees "up" momentarily when trying to out turn the Luftwaffe's best, even when using the flap combat position on the selector. Of course the nose "pitch-up" resulted in increased aerodynamic drag, and must be used cautiously. High speed is generally preferred over low speed in combat situations. Properly flown, the Fowler flaps of the P-38 allowed very tight turning radius."

Der Gabelschwanz Teufel Part II by Carlo Kopp

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[Ack-Ack]

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[GScholz]

Yes AKAK, but that chart describes continous max roll rate, not how long it took to achieve that roll rate.

[Ack-Ack]

The chart just provides further proof to Capt. Stan Richardson's reasons why early P-38's had a slow initial roll rate.

The P-38 was a large fighter with much mass. 52' wingspan and long, wide-chord ailerons contributed to slow response along the longitudinal axis of the early airplanes. The higher the indicated airspeed, the slower the response. At very high IAS it took plenty of muscle to roll the airplane.

So the delay that BH was talking about was only seen on the P-38s without the hydraulic boosted ailerons.



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[MANDOBLE]

Originally posted by GScholz
Yes AKAK, but that chart describes continous max roll rate, not how long it took to achieve that roll rate.

That is the point. Bullethead talk about roll acceleration, not roll rate.

Think also that roll rate alone is marginally important when in most cases you are not rolling more than 180 degrees, and usually 90.

What would be the time to 90 degrees from a 0 dps in a P38J?

[Bullethead]

Just to make sure everybody understands what I said originally (seeing a few misinterpretations in this thread already )...

1.  The guys I talked to did NOT fly P38s with powered ailerons.

2.  These guys said there was NO delay between moving the stick and the plane starting to roll.  IOW, the plane was very responsive to control input.

3.  That said, these guys also said that the roll rate was not awe-inspiring compared to single-engine planes.

So at the bottom line, it seems that the plane moved as soon as you moved the stick.  However, in the roll axis at least, it didn't move as fast as most of the competition.  But still, you moved the stick and you moved the plane.  And again, this is WITHOUT powered ailerons.

[ccvi]

There's a difference between "starting to roll" and "rolling at maximum rolling speed".


Anyway, those planes are all outdated. Modern acrobatics aircraft can do more than 360deg/second.