Aileron reverse speed and roll rate of boosted ailerons

re "But the Mike Williams chart giving over 180°/s...It's superhuman. How come?"

The P-38J roll chart is kind of deceptive in the way it is presented. The curve is actually a representation of the radial acceleration, ie how long does it take to go from 0° to 90° at an acceleration of a.

The rolling velocity at the end of 1 sec is ~100°/s but the aircraft has not yet had enough time to roll more than 90° after .45 seconds.

100°/s is approximately 5°/s more than what the P-38L-1-LO graph shows. Do we know if the J model used for the chart was fitted with the leading edge fuel tanks. If not, that might account for the difference. It also may take more than 1 second for the P-38J/L with booster to reach its maximum roll rate, although it could not be much longer, and the roll rate not too much higher.

ThomasP said:

re "But the Mike Williams chart giving over 180°/s...It's superhuman. How come?"

The P-38J roll chart is kind of deceptive in the way it is presented. The curve is actually a representation of the radial acceleration, ie how long does it take to go from 0° to 90° at an acceleration of a.

The rolling velocity at the end of 1 sec is 100°/s but the aircraft has not yet had enough time to roll more than 90°.

100°/s is approximately 5°/s more than what the P-38L-1-LO graph shows. Do we know if the J model used for the chart was fitted with the leading edge fuel tanks. If not, that might account for the difference.

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Rolling at such a speed without marked wing bending or aileron-reversal, the torsional stiffness of the P-38 wing must have a reinforcement in form of it being a twin-boom design.

spicmart said:

Rolling at such a speed without marked wing bending or aileron-reversal, the torsional stiffness of the P-38 wing must have a reinforcement in form of it being a twin-boom design.

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Why "must" and not "could"?

Edited my post#21 above to include "It also may take more than 1 second for the P-38J/L with booster to reach its maximum roll rate, although it could not be much longer, and the roll rate not too much higher." and "after .45 seconds.".

pbehn said:

Why "must" and not "could"?

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"had arguably". Hope that is better.

T ThomasP , thanks for the explanation.
Did the P-38 have larger ailerons?
A twin-boom design should have a higher mass moment of inertia than a plane conventional configuration.
I guess equipping other fighters with boosted ailerons should take that advantage readily away.

I wonder if there were ever boosted elevators or rudders installed in fighters.
The Fw 190s and Me 109s suffered from excessive forces of and rather ineffective elevators in a dive.

Well, considering we went from manual controls to hydraulic in a VERY short time after WWII, I think the answer could easily be "yes, they COULD have fitted boosted controls to a WWII single-engine piston fighter." Historically, they didn't do so. The P-38 was arguably the only twin-engine fighter that could reasonably dogfight with a first-tier single-engine fighter, Mosquito notwithstanding. I'm guessing they saw the boosted ailerons on the P-38 as required to gain fighter performance, but the single-engine fighters were already AT fighter performance levels and nobody ever thought to do that to the single-engine fighters.

As mentioned above, the Bf 109 likely could have used boosted controls from the beginning, especially considering the complete lack of rudder trim throughout the series. There were MANY WWII fighters with controls that were VERY stiff at over 400 mph. They ALL could have used boosted controls. But boosted controls would have not worked for anything beyond the critical mach number, so they could have added maneuverability at high speeds ... only up to critical mach. After that, they'd have been as ineffective ad the existing controls were.

It might have made the dogfights more interesting, or at least turned them into higher g-level fights. Perhaps all that might accomplish would have been to lose altitude even more quickly, and so more would have wound up at ground level in horizontal turning fights.

I could not remember where I had seen the 120°/s roll rate number for the P-38J with boosted ailerons, but I found it again at:

"http://www.wwiiaircraftperformance.org/mustang/Performance_Data_on_Fighter_Aircraft.pdf"

Note that in the text on the first page it mentions that the roll rates for the P-47B (63°/s) and P-51B (78°/s) were at 50 lbs stick force, but at 80 lbs wheel force for the P-38J (39°/s) with out boost. It then explains that the 120°/s for the P-38J with boost is estimated.

The information was requested on 22 June 1944, and the report was classified(?) on 26 July 1944. The P-38J-25-LO was the first production batch that included the boosted ailerons. Apparently none of the -25 model (or the in-field modification kits for earlier J models) reached operational combat units until July 1944 (or later?). Does anyone know for sure when the -25 model reached combat units?

Thomas P

It appears that the J-25 model arrived in combat units in August of 1944. The 479th FG appears to have received 2 in August (Source: Mighty Eighth War Manual and the website Littlefriends.co.uk). On page 37 of the book An Escort of P-38s, also lists August of 1944 as the time the 1st Fighter Group received the first J-25. Remember, only 210 J-25's were built, and half of them were converted to F-5E-3 photo ships.

Eagledad

GregP
I forgot to mention that the Fw 190D-13 and Ta 152C and H did feature hydraulically boosted ailerons.
The Mosquito, thoguh there were fighter-bomber variants, was never agile enough to be dedicated fighter vs. fighter planes.
Such were, along with the P-38, the DH 103 Hornet, the Grumman F7F Tigercat and the Mitsubishi Ki-83.

Hey spicmart,

Did the F7F ever get boosted ailerons? I thought it was just a boosted rudder, although I may be being overly picky as it is still a boosted control surface.

Hi Spicemart,

Why would you say the Ta 152 had hydraulic ailerons? After looking at WWII airplanes for more than 50 years, none of the Fw 190 family AFAIK had hydraulic controls, and generally had rapid roll rates at low-to-medium speeds. But, I never saw hydraulic ailerons included in the description anywhere before.

The rest of your list above were good airplanes, though not WWII combat airplanes. While the Tigercat got into the war, it never encountered an enemy aircraft in action ... but it DID make a WWII appearance. The Ki-83 population was 4 and none saw service in combat. The Hornet, while it flew in WWII (1944), wasn't introduced into service until 1946.

Great list of airplanes, though. It would have been interesting to see what the I.Ae 30 Nancu might have done, too. Cheers!



I.Ae 30 Nancu above. Merlin 600s. Unfortunately, the population was 1 and it flew in 1948. It was post-war in first flight, but was firmly rooted in WWII design.

GregP said:

Hi Spicemart,

Why would you say the Ta 152 had hydraulic ailerons? After looking at WWII airplanes for more than 50 years, none of the Fw 190 family AFAIK had hydraulic controls, and generally had rapid roll rates at low-to-medium speeds. But, I never saw hydraulic ailerons included in the description anywhere before.

The rest of your list above were good airplanes, though not WWII combat airplanes. While the Tigercat got into the war, it never encountered an enemy aircraft in action ... but it DID make a WWII appearance. The Ki-83 population was 4 and none saw service in combat. The Hornet, while it flew in WWII (1944), wasn't introduced into service until 1946.

Great list of airplanes, though. It would have been interesting to see what the I.Ae 30 Nancu might have done, too. Cheers!

View attachment 596572

I.Ae 30 Nancu above. Merlin 600s. Unfortunately, the population was 1 and it flew in 1948.

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Greg,

I was under the impression that the Ta-152s with increased wingspan had the hydraulically boosted ailerons. I must have read it in the same place.

Cheers,
Biff

I have a book on it (in storage) and it is not mentioned as I recall. Doesn't mean it didn't have it, but it wasn't mentioned. I could be mistaken and it might have hydraulic controls, but that certainly doesn't show up in a casual look into Ta 152 design features online. If DID have hydraulic flaps and landing gear, but there is no mention of powered ailerons.

I don't really care either way, but it might help explain why the Ta 152 wasn't maligned for being a slow roller, particularly down low (where it actually got used in wartime) when the aspect ratio went so much higher. I shall investigate further, just out of curiosity, nothing more at this point.

Hey eagledad,

Thanks for the info.

Edited my post#5: added the P-38L-1-LO roll rate curve, converted to IAS, to the NACA 868 chart.

T ThomasP .
I don't know about the F7F Tigercat but it is interesting that it had boosted rudder.

GregP
The Fw 190D-13 from the Flying Heritage Collection at some point had its wings mixed up with the D-9's from the National Museum in Dayton Ohio.
When this was noted they were swapped and it was found out that the D-13 had hydraulically boosted ailerons.
Dietmar Hermann who is specialized in Focke Wulf planes and writes books and articles,, stated the Ta 152H did have boost..
Both the D-13 and the 152 were very late models.

Another point is that it's how sturdy the Ta 152 wings must have been built, despite their slender glider-like appearence, in order to take the increased loads of boost-aided roll.
The early Ta 152C and H wings were similarly structured like the 190 wings.
Later subversions, however, had a shortened main spar wide enough to hold the undercarriage. From there to the wingtips was a construction consisting of multiple lateral tubes (don't know how to call it, see image).
The shortening the spars gave space for wing tanks for increased range.
Which meant even higher loads.
Interesting that this construction method seems to do the requirement for taking even higher loads .justice.
Any engineer here who can say something about this compared to the standard spar construction?
View attachment 596667
The standard Fw 190 was probably to get such a wing structure as well. At least I saw such a drawing in a publication.

About the iAe 30., It looked indeed very Hornet-like. The Fw 187 might have been up there, too.

The airplane from the Flying Heritage Collection came from the Doug Champlin Fighter Museum in Mesa, Arizona, former home of the American Fighter Aces Association. When the two airplanes (including the one from the Dayton Museum) were restored, it was with the help of Kurt Tank. They found the wings were swapped some years later, but they sat that way for 20+ years until Doug sold his museum's assets. Then they were swapped back. When I was there with Curtis Earl (owned a MiG-15 bis displayed at the Champlin Fighter Museum), Doug Champlin mentioned the wing swap.

He didn't mention the hydraulic ailerons and they aren't mentioned anywhere else I can find. The D-13 was VERY late in production near when production stopped. If they, indeed, ARE hydraulically assisted, then I am assuming it was only a very late airframe or few. In fact, they only made 17 Fw 190 D-13s and only 2 of them saw service. When I got to sit in that airplane, my overriding impression was the narrow cockpit canopy. I didn't have a flight helmet on and could barely turn my head sideways. When I was there, I didn't look at the aileron control mechanisms, and cannot say one way or the other.

I'm not sure I believe the ailerons were hydraulically-operated, though I know the landing gear and flaps were, so it had a hydraulic system ... which none of the rest of the Fw 190 family had. Perhaps the fact that it had a hydraulic system for the flaps and gear made someone assume it had hydraulic ailerons. With it's high roll rate, there was no need for assist. Once, at an art gathering at the Champlin Museum around 1987 or so, I got to hear them start it. At the time, they had the Fw 190 D and a P-40 that only had a total of 40 flight hours on it (went from production line to storage). They had them side by side and started them one by one. The Fw 190 D could only run at idle at the time, and is probably still that way. It was missing some fuel circuits for off-idle operation.

I am open to the hydraulic ailerons, but am not convinced the D-13 had them. Hydraulic ailerons on the Ta 152 H make sense to me due to the long span (ta 152 H anyway) and the need for crisp handling. But the Fw 190 D-13 didn't HAVE long wings and didn't need the assist. Maybe it was development for the Ta 152 H, I don't know. I have checked all my references not in storage, and they mention the hydraulic system for the landing gear and flaps for both the D-13 and the Ta 152 H, but none mention the ailerons as boosted as yet. Still, it could be the case.

I'm open to it if I can find any evidence of same. They are unlikely to let me look at it again like I got to when Doug Champlin owned it since I don't know anyone there personally like I did at the Champlin Museum.

The entire Ta 152 family together only had somewhere between 6 and 10 WWII victory credits (depending on who you believe) , likely due to the deteriorating war situation. Sending out 2 or 3 Ta 152s against 600 P-51Ds wasn't a situation ripe for turning the tide of the war, and the air resistance collapsed around the end of March 1945. If you go look at the USAAF Statistical Digest of WWII, Table 166, we average 616 enemy aircraft destroyed in the ETO from Oct 44 - Mar 45. Then, in April 1945, the number rose to 4,367. Rather clear evidence of the Luftwaffe collapse. In May the number fell to 28 and there were no more enemy aircraft destroyed for the rest of the ETO war. So, for me anyway, the Ta 152 was just about to show it's worth as a fighter in April 1945 when the Luftwaffe and the German Riech collapsed around it.

Perhaps the small total of victories awarded to the Ta 152 were due much more to being the hunted few in a crowded sky rather than lack of individual capability.

And the wing construction in the Fw 190 is unlike any other wing I have ever seen. Very strange, but effective.

Eric Brown doesn't mention any hydraulic boosting of the ailerons on his Ta 152 H-1

"On the descent from altitude to Brize Norton, I had time to make quick checks on the stability and control of the German fighter. I found a noticeable reduction in roll rate and an increase in the stick force per g by comparison with its BMW 801-powered predecessors, some of the more attractive qualities of the original fighter having been sacrificed in order to achieve the best possible performance at extreme altitudes. I therefore expected the stability to be improved over that of the Fw 190, as indeed it was, but it was not so good that a protracted flight at 45,000 ft (13 715 m) would not have been a fatiguing experience, a fact evidently recognised by the provision of an autopilot."

Perhaps Dietman Harmann saw the hydraulic system and assumed powered ailerons.

The Bf 109 has a hydraulic pump, too, but it only runs the landing gear. We are in the closing stages of restoring our Ha-1112 and, while the engine was being overhauled, we started working on "other systems" mainly because we had nothing else to do. We moved the hydraulic pump from the engine compartment to behind the pilot and moved the battery forward to compensate. Now, the only hydraulic oil in it comes nowhere NEAR the only real source of heat in the aircraft, and the possibility of hydraulic oil fire is all but eliminated.

The "we"above is the regular Bf 109 restoration crew, consisting of Bert Bruckman and George Orff with some semi-regular participation by others including me on occasion. I was on the original Bf 109 crew, but moved on when we got about 5 - 6 years into it.

I mention that only because the Bf 109 is an existing earlier design with both a hydraulic system and non-boosted controls.