P-47D-30 automatic flaps mystery vs Chat GPT

[wrathofatlantis]

I just thought this was too fascinating not to share, and I know there are many fans of the P-47 here.

I was always puzzled by this document:


View: https://i.imgur.com/BgwGkGh.png

And particularly this paragraph at the top of page 5:


View: https://i.imgur.com/JuKiEgN.png

"It should be noted that the flaps on the F-47D-30 are of the blow-up type; that is, the flap deflection varies with decreasing airspeed until they reach a speed where the flaps remain fully down. The variation with airspeed is shown in figure 12."

The figure 12 chart reads 40 degrees at 140 mph ias, 30 degrees at 160 mph ias, and stops at 10 degrees at 180 mph ias:

This chart:


View: https://i.imgur.com/FdHkc9y.png

I already knew that this automatic function appears nowhere (allegedly) in any P-47 flight manuals, so in the interest of verifying if Chat GPT could sort this out, I asked the question, with interesting results...

My question: " I did find an original test document of a P-47D-30 block that stated "the aircraft has blow-up flaps" which I interpret as automatic flaps that come up under wind pressure: This makes sense to me, as the low deployment speed limit and the complex trapeze hinges would make the design subject to abuse or damage: Do you know if the later P-47D-30 block models did indeed have these automatic wind-blown flaps (like those on the Hellcat), as I am having difficulty in confirming the test statement, of which I consider the term "blow-up" very clear-cut and unambiguous..."

Chat GPT: "Your interpretation is actually very plausible, and the wording "blow-up flaps" does appear in period discussions of US Navy aircraft, but for the Republic P-47 Thunderbolt the situation is a bit nuanced.
Short answer:
There is no strong evidence that the P-47 had intentionally designed "blow-up" or wind-relieving flaps like the naval fighters, but the geometry and hydraulic actuation of the P-47's NACA slotted flaps could allow them to be forced upward by aerodynamic loads if oversped. That is likely what the test report you saw was referring to.

3. What "blow-up flaps" probably meant in the test report
In engineering language of the period, "blow-up" often meant:

aerodynamic loads force the flap back toward the retracted position.

This does not necessarily mean a designed automatic feature.
On the P-47 it likely meant:

• if dynamic pressure exceeded the hydraulic holding force
• the flaps could be forced upward by airflow
• preventing structural failure.

In other words, a passive pressure-relief behavior, not a deliberate design."


To this I posted the original pdf document, not being sure if it could read it, and asked:

My question: "The phrase in the the pdf document I pasted here (don't know if you can read it) says on p. 5: "It should be noted that the flaps on the f-47D-30 are of the blow-up type; that is, the flap deflection varies with decreasing airspeed until they reach a speed where the flaps remain fully down. The variation with airspeed is shown in figure 12." The figure 12 chart reads 40 degrees at 140 mph ias, 30 degrees at 160 mph ias, and stops at 10 degrees at 180 mph ias: This is in line with automatic flap behaviour at landing speed, not a safety protection at excessive speed... Isn't this odd given the mention of automatic flaps does not appear in P-47 manuals?"

Chat GPT (who apparently could read the pdf document):

"You're absolutely right to find that wording odd, and your interpretation is actually very close to what the NACA text implies. The key passage says:

"The flaps on the F-47D-30 are of the blow-up type; that is, the flap deflection varies with decreasing airspeed until a speed is reached where the flaps remain full down."
c046fbaa-702e-4fc9-add0-3505793…

And the figure you mentioned indeed shows roughly:

• ≈10° at ~180 mph IAS
• ≈30° at ~160 mph IAS
• ≈40° at ~140 mph IAS

This behavior is exactly what one would expect from an aerodynamic blow-back (or float) system, and importantly it behaves like an automatic landing-flap schedule, not a high-speed protection device.

Your observation that this is not described in the P-47 flight manuals is the real puzzle—and it's a good one."


Chat GPT then goes into a fascinating apparently machine-driven spiel as to why the behaviour might have been incidental, but was not design-intentional... (Probably because it just can't figure out why this is not mentioned in the pilot manual, my theory is the D-30 is pretty late and somehow they did not re-print...):

Why it looks like an automatic system
The behavior you noticed really does resemble:

• automatic landing flaps
• or naval fighter blow-back flaps (e.g., the Grumman F6F Hellcat)

But the important distinction is:
Those aircraft intentionally designed the system to do that.
The P-47 likely did not.
Instead it was probably an incidental aerodynamic equilibrium between:

• hydraulic actuator force
• hinge moment from airflow.

NACA simply reported the resulting equilibrium angle vs speed.
Why manuals probably never mentioned it
There are several reasons the P-47 pilot manuals likely omit this behavior:

1. Pilots were instructed to deploy flaps only below specific speeds.
   Within that regime, the flaps would likely reach full deflection quickly, so the intermediate positions weren't operationally relevant.
2. NACA flight tests explored wider speed ranges.
   Their approach runs often began well above the normal flap extension speed, which exposed the blow-back behavior.
3. The phenomenon was not considered a pilot-controlled feature.
   It was just an aerodynamic property of the system, not something the pilot was meant to use.

Why your observation is actually very insightful.

What you noticed from Figure 12 suggests something interesting:
The P-47's flap system essentially behaved like a passive variable-geometry flap during approach:

IAS	Approx flap angle
~180 mph	~10°
~160 mph	~30°
~140 mph	~40°

That means during a typical landing deceleration the aircraft would naturally gain flap camber as speed dropped, which:

• increases lift coefficient
• keeps the lift curve smoother
• reduces trim changes.

So while probably not intentionally designed, it actually produced very desirable handling characteristics during approach—which is precisely what that section of the report was analyzing."


It was interesting to see that the response was a bit slower this time, but that was probably just from reading the pdf... While the big logical hurdle seems to be that the printing of flight manuals may not have been updated (or updated with an insert that somehow became separated on available copies), Chat GPT did recognize the conundrum, seemingly found it significant and interesting, and provided a response with a logical hole, but not stupid given the circumstances...

I just thought this was too good to not share...

I still don't know why this massively significant feature fails to appear in P-47 flight manuals... To me it clearly is worded as a normal feature of the D-30 block in the document, not something set up for that particular test (or it clearly would have been stated). For those interested, this is the aircraft in question:


View: https://i.imgur.com/jKtTxOm.png?1

 

[Irregualr23]

Relief valve was used on AAF fighters like P-51 and later P-47, and also on later F4U's cowl flaps in order to give overspeed protection, it works in different manner as a blow-up unit than the naval spring-loaded blow-up mechanism used on Grumman fighters.

I think, if we want to dig out the mystery of P-47's flap system, P-51 should be the starting point since Mr. Steppe as the representative of North American first mentioned the existence of this system onboard P-51 during the JFC.

Also, since he had mentioned that the flap system will bring the flap handle up, the system should worked the same way as the F6F, that the flaps were controlled not only by a blow-up unit( can be both spring and relief valve) , but also by an automatic retracting system connected to the airspeed indicator. The "blow-up" system would only decrease the deflection angle of slotted flaps around the hinge axis, and the retracting system is used to finish the retraction, ensuring slots and gaps of the flap been fully closed.

This system was described in British version of Hellcat's flight manual:

The blow-up is a mechanical system that works in all conditions, but the auto-retraction unit only works if the flaps were lowered by electircal switch, which provides full automatic works with no neutral position. The Hellcat also provides a flap lever which is similar to P-47's flap control, that the pilot is able to lower the flap and use neutral position to obtain any intermediate position, at this mode, the flap will only gets blowed up to 15 deg at 160kts ASI, the control unit won't get activated to fully raise the flap when overspeeding.

Provided that P-47 also used NACA slotted type, it should has both unit, but I'm unsure whether the automatic control could be turned off since P-47 only has one flap lever for flap control.( Exclude the emergency hand pump). That would depend whether the flap of P-47 remains a small deflection angle at high speed as a combat flap, or get fully raised.

 

[wrathofatlantis]

Relief valve was used on AAF fighters like P-51 and later P-47, and also on later F4U's cowl flaps in order to give overspeed protection, it works in different manner as a blow-up unit than the naval spring-loaded blow-up mechanism used on Grumman fighters.

I think, if we want to dig out the mystery of P-47's flap system, P-51 should be the starting point since Mr. Steppe as the representative of North American first mentioned the existence of this system onboard P-51 during the JFC.
View attachment 870861

Also, since he had mentioned that the flap system will bring the flap handle up, the system should worked the same way as the F6F, that the flaps were controlled not only by a blow-up unit( can be both spring and relief valve) , but also by an automatic retracting system connected to the airspeed indicator. The "blow-up" system would only decrease the deflection angle of slotted flaps around the hinge axis, and the retracting system is used to finish the retraction, ensuring slots and gaps of the flap been fully closed.

This system was described in British version of Hellcat's flight manual:
View attachment 870862

The blow-up is a mechanical system that works in all conditions, but the auto-retraction unit only works if the flaps were lowered by electircal switch, which provides full automatic works with no neutral position. The Hellcat also provides a flap lever which is similar to P-47's flap control, that the pilot is able to lower the flap and use neutral position to obtain any intermediate position, at this mode, the flap will only gets blowed up to 15 deg at 160kts ASI, the control unit won't get activated to fully raise the flap when overspeeding.

Provided that P-47 also used NACA slotted type, it should has both unit, but I'm unsure whether the automatic control could be turned off since P-47 only has one flap lever for flap control.( Exclude the emergency hand pump). That would depend whether the flap of P-47 remains a small deflection angle at high speed as a combat flap, or get fully raised.

But the system in the P-47 appears to be very different than on the P-51, since the P-47 test statement says "flap angle varies with decreasing speed", while for the P-51 system it is stated in your quote "The flaps come back up and stay there. If the pilots wants them back down, he has got to put them down."

One is clearly an overspeed protection, reflected in the higher speed tolerances of the P-51 flap angles (10 degrees at 400 mph), while the P-47 has clearly a lower speed active flap system, with a 10 degree flap angle tolerance limit of less than half the speed of the P-51 at the same angle: 10 degrees at 180 mph, not 400...

On the P-51, the handle is pushed up by the speed and does not come down to increase the flap angle with decreasing speed, which precludes the flaps from being called "blow up", or automatic.
On the Hellcat, my understanding is that there are two systems, one is an up-down switch, which moves the flaps back horizontally, where at one point, the flaps are then freely lowered by springs according to speed (which is why this console electric switch is only up-down, with no selectable angles), but this electric system also locks the flaps up past 170-180 knots, if it was used first.

Otherwise specific angle control is through a lever near the seat which allows selecting angles within the low spring force landing limits, probably not much more. This is, amazingly, left unclear...

If this seat lever is used first, bypassing the electrical/hydraulic horizontal rearward motion, then the electric system is out of the loop and the flaps will not be locked up past 170-180 knots, unless the seat lever is returned to neutral.

This means that above 180 knots the electrical up/down console switch has only one effect, which is to increase slightly the wing area of the Hellcat with a horizontal backward movement (not explained at all in the British description). Below 180 knots you can choose the flap angle with the seat lever only, but probably not far beyond what the springs are able to push down for you. (Again, left unclear...)

Not clear is how far they will exceed spring settings before they blow up, if you subsequently exceed the speed after setting them at a given angle with the seat lever...

The P-47D-30 (and others blocks?) is obviously closer to the Hellcat than to the P-51, because the flaps are actively pushed down with lowered speed, and in the lower speed range, a huge difference.

I still find it amazing is that this is not explained at all as an automatic flap system in any P-47 pilot manual... The British explanation of the Hellcat system is also very poor and confusing, and makes no mention of the initial horizontal flap motion, or what speed range a manual flap setting will tolerate...

The implications of this in combat are huge: The P-51 flap angles were so crucial in combat that the specific angles were discussed over the radio during actual multiple consecutive 360 circle fights. By contrast, the use of flaps is never mentioned in any P-47 Encounter Reports, even though making circles in combat is virtually all the P-47 ever did (easily the most obsessive extreme low speed circle fighter in the West, with multiple level and even climbing circles right down to 140 mph indicated at 5000 feet).

 

[Irregualr23]

This means that above 180 knots the electrical up/down console switch has only one effect, which is to increase slightly the wing area of the Hellcat with a horizontal backward movement (not explained at all in the British description). Below 180 knots you can choose the flap angle with the seat lever only, but probably not far beyond what the springs are able to push down for you. (Again, left unclear...)

Not clear is how far they will exceed spring settings before they blow up, if you subsequently exceed the speed after setting them at a given angle with the seat lever...

I saw a case in action report where it mentioned the use of flap at 200kts on the Hellcat, not sure whether it was lowered by the lever:

The implications of this in combat are huge: The P-51 flap angles were so crucial in combat that the specific angles were discussed over the radio during actual multiple consecutive 360 circle fights. By contrast, the use of flaps is never mentioned in any P-47 Encounter Reports, even though making circles in combat is virtually all the P-47 ever did (easily the most obsessive extreme low speed circle fighter in the West, with multiple level and even climbing circles right down to 140 mph indicated at 5000 feet).

It is very interesting, because I tried to collect instances where flaps been used in combat on USN fighters.

So far I've found 4 instances where flaps where deployed in turn fights on the Hellcat, from action reports. All of which on the F6F-3, and mostly happened during the earlier stage of its service, except one instances an F6F-3 outturned a Tojo using flaps in late 1944. There were no specific mentioning of using flaps for manuevering on the F6F-5, although some mentioned popping flaps to prevent overrunning the enemy plane.

It is interesting however, some F6F-5 pilots in later interviews mentioned the use of flaps during maneuvering, where in the action report related to that specific dogfight, the same pilot did not mention flaps in the narrative. Examples where F6F-5 dogfighting an Ki-43 from Akeno in March 19 1945 near Matsuyama, and F6F-5 dogfighting Takashi Oshibuchi's N1K2 above the Bongo strait, flaps where used by the Hellcat but not mentioned in the report.

So my theory was that, the flaps were not guranteed by the manufactuer to be used in dogfighting, deploying them during turn fighting may be a sign of violating the regulation, thus the later pilot relectant to mention it in the report. Possibly, the similar happened for the P-47's encounter reports. Structurally, extensible slotted flaps on the F6F and P-47 may be weak in construction than P-51's simple flaps, despite generating significantly greater lift. The extensive use of slotted flaps, or using it under excessive loads, may cause wear and tear to the system, reducing its lifespan, performance and even leads to a failure.

Still, this theory is contradicted, as I still found the case of the use of flap in dogfight on the FM-2 Wildcat, where its flap system was even more ackward to be used in combat. And yet I found 0 case where flaps where used in combat on the F4U Corsair according to the action report, despite the flap system on the F4U specifically provided a 20deg option to be used in maneuvering.

So the reason whether a pilot decides to share his experience of using flap in the report is still unclear. My own observation was that, towards the end of the war, pilots decided not to share their experience with combat flaps in the report. Possbily some P-47 did used flaps for manuevering, but they were relectant to mention the experience in the report, also, the releative small sample space of P-47's encounter reports provided on the wwiiaircraftperformance site can also be a reason.

 

[wrathofatlantis]

I saw a case in action report where it mentioned the use of flap at 200kts on the Hellcat, not sure whether it was lowered by the lever:
View attachment 871003


It is very interesting, because I tried to collect instances where flaps been used in combat on USN fighters.

So far I've found 4 instances where flaps where deployed in turn fights on the Hellcat, from action reports. All of which on the F6F-3, and mostly happened during the earlier stage of its service, except one instances an F6F-3 outturned a Tojo using flaps in late 1944. There were no specific mentioning of using flaps for manuevering on the F6F-5, although some mentioned popping flaps to prevent overrunning the enemy plane.

It is interesting however, some F6F-5 pilots in later interviews mentioned the use of flaps during maneuvering, where in the action report related to that specific dogfight, the same pilot did not mention flaps in the narrative. Examples where F6F-5 dogfighting an Ki-43 from Akeno in March 19 1945 near Matsuyama, and F6F-5 dogfighting Takashi Oshibuchi's N1K2 above the Bongo strait, flaps where used by the Hellcat but not mentioned in the report.

So my theory was that, the flaps were not guranteed by the manufactuer to be used in dogfighting, deploying them during turn fighting may be a sign of violating the regulation, thus the later pilot relectant to mention it in the report. Possibly, the similar happened for the P-47's encounter reports. Structurally, extensible slotted flaps on the F6F and P-47 may be weak in construction than P-51's simple flaps, despite generating significantly greater lift. The extensive use of slotted flaps, or using it under excessive loads, may cause wear and tear to the system, reducing its lifespan, performance and even leads to a failure.

Still, this theory is contradicted, as I still found the case of the use of flap in dogfight on the FM-2 Wildcat, where its flap system was even more ackward to be used in combat. And yet I found 0 case where flaps where used in combat on the F4U Corsair according to the action report, despite the flap system on the F4U specifically provided a 20deg option to be used in maneuvering.

So the reason whether a pilot decides to share his experience of using flap in the report is still unclear. My own observation was that, towards the end of the war, pilots decided not to share their experience with combat flaps in the report. Possbily some P-47 did used flaps for manuevering, but they were relectant to mention the experience in the report, also, the releative small sample space of P-47's encounter reports provided on the wwiiaircraftperformance site can also be a reason.

Excellent post that I much appreciate, especially the insight that the -3 Hellcat could match turn (likely mostly with the later A6M5), which is something I always suspected (the f6f had the largest single engine fighter wings of WWII, 31 square metres, P-47N 28, Ta-152H's 23 square metres). Zero pilots have stated about the Hellcat: "Of the late War US fighters, only the Hellcat would accept turning combat. The P-38 was comparatively fragile, and with only a few hits it would lose a wing."

There is also a well-known account of the last fm-2 Wildcat to take off from the St-Lo (before it was destroyed), where the pilot describes out-turning an A6M5 Zero by a significant margin at medium speed, but only over one circle or less (the Wildcat had 24 square metres, still a larger wing than the Ta-152H!).

I wonder if the Hellcat accounts, that make mention of the flap use, specify if the electric console switch was used, which would only push back the flaps horizontally, which has no implied fragility?

Do they mention using the seat lever to set angles? If this flap use disappears on the -5 Hellcat, it may indicate that the seat lever flap angles were "hard", with no slip off, and induced flap damage as you say...

The "WWII Aircraft Performance" site has had some issues lately (it seems you can only access flight tests directly from the front page now) but it did contain over 800-900 P-47 Encounter Reports, so that would not be what I would call a "relatively small" P-47 sample... About 900 for the P-51 as well. I've read them all, saving the most significant ones. (It really opens your eyes as to how common circle fighting was: Close to the majority of cases, certainly over 30-40%, with near zero examples of dives followed by a zoom. Sneaking up from a lower altitude under the tail is probably the next most common, but still much rarer in prevalence than circles.)...

 

[Irregualr23]

Excellent post that I much appreciate, especially the insight that the -3 Hellcat could match turn (likely mostly with the later A6M5), which is something I always suspected (the f6f had the largest single engine fighter wings of WWII, 31 square metres, P-47N 28, Ta-152H's 23 square metres). Zero pilots have stated about the Hellcat: "Of the late War US fighters, only the Hellcat would accept turning combat. The P-38 was comparatively fragile, and with only a few hits it would lose a wing."

There is also a well-known account of the last fm-2 Wildcat to take off from the St-Lo (before it was destroyed), where the pilot describes out-turning an A6M5 Zero by a significant margin at medium speed, but only over one circle or less (the Wildcat had 24 square metres, still a larger wing than the Ta-152H!).

I wonder if the Hellcat accounts, that make mention of the flap use, specify if the electric console switch was used, which would only push back the flaps horizontally, which has no implied fragility?

Do they mention using the seat lever to set angles? If this flap use disappears on the -5 Hellcat, it may indicate that the seat lever flap angles were "hard", with no slip off, and induced flap damage as you say...

The "WWII Aircraft Performance" site has had some issues lately (it seems you can only access flight tests directly from the front page now) but it did contain over 800-900 P-47 Encounter Reports, so that would not be what I would call a "relatively small" P-47 sample... About 900 for the P-51 as well. I've read them all, saving the most significant ones. (It really opens your eyes as to how common circle fighting was: Close to the majority of cases, certainly over 30-40%, with near zero examples of dives followed by a zoom. Sneaking up from a lower altitude under the tail is probably the next most common, but still much rarer in prevalence than circles.)...

Hi, regarding to set specific flap positions, so far I've only saw Brits mentioned it, and quite often.

The AAE tests on intermediate positions of the Hellcat:

Eric Brown, stated in his article that the Hellcat should use 20deg postion for take-off:

As for combat usage, I provide some below:
An F6F-3 singlehandedly turned with 3 Zeros by using his flaps, and shot one down, despite his commander insist that he shouldn't turn fight the Zero:

This one actually came from an F6F-5:

As for the FM-2 I also saw records where it used flaps to follow A6M5 in the turn, and the Zero was not able to pull out from the tight turn and crashed into the water, while the FM-2 successfully pulled out with his flaps down.

I heard the wing flap system on the A6M was connected with the hydralic system that also works for the gear, which means the plane could not lower the flap independently without lowering its gear at the same time, which made the use of flap during dogfights impossible. Which was also a reason A7M reppu was tested to be able to outturn the A6M3 with former's combat flap in operation, despite that the A7M had much higher wing-loading.

 

[Irregualr23]

Excellent post that I much appreciate, especially the insight that the -3 Hellcat could match turn (likely mostly with the later A6M5), which is something I always suspected (the f6f had the largest single engine fighter wings of WWII, 31 square metres, P-47N 28, Ta-152H's 23 square metres). Zero pilots have stated about the Hellcat: "Of the late War US fighters, only the Hellcat would accept turning combat. The P-38 was comparatively fragile, and with only a few hits it would lose a wing."

There is also a well-known account of the last fm-2 Wildcat to take off from the St-Lo (before it was destroyed), where the pilot describes out-turning an A6M5 Zero by a significant margin at medium speed, but only over one circle or less (the Wildcat had 24 square metres, still a larger wing than the Ta-152H!).

I wonder if the Hellcat accounts, that make mention of the flap use, specify if the electric console switch was used, which would only push back the flaps horizontally, which has no implied fragility?

Do they mention using the seat lever to set angles? If this flap use disappears on the -5 Hellcat, it may indicate that the seat lever flap angles were "hard", with no slip off, and induced flap damage as you say...

The "WWII Aircraft Performance" site has had some issues lately (it seems you can only access flight tests directly from the front page now) but it did contain over 800-900 P-47 Encounter Reports, so that would not be what I would call a "relatively small" P-47 sample... About 900 for the P-51 as well. I've read them all, saving the most significant ones. (It really opens your eyes as to how common circle fighting was: Close to the majority of cases, certainly over 30-40%, with near zero examples of dives followed by a zoom. Sneaking up from a lower altitude under the tail is probably the next most common, but still much rarer in prevalence than circles.)...

Also, both the F6F and the P-47 had relatively large wing area but smaller aspect ratio (lower than 6), which gives them larger than average mean-aerodynamic chord, which would make the flight reynolds' number of both airplane larger than most single engine fighters under similar condition. This is very beneficial for the aircraft's maximum lift coefficient, and both airplanes were using NACA230 airfoil, which is the best conventional airfoil with high maximum lift, low drag and very low pitchming moment that further boost the trimmed CL in-flight. (Although Seversky S-3 airfoil on the P-47 may be slightly modified and comes with lower lift)

In comparison, the Japanese used older NACA 4 -digit airfoils NACA23 and 33 on the A6M, with 2 deg washout and forward CG position, which make the airplane probably mediocre in terms of CLmax, and the maneverability of the Zero mostly came from its low wing loading and good energy retention thanks to its aspect ratio. The Japanese viewed tha stall characterstics very high, thus exclusively used wash-out on wings that would harm the maximum lift, and relectant to use NACA 230 on fighters ( Ki-45 was an outlier) due to the bad stall type of the airfoil (the Brits also relectant to use it).

The USN fighters F2A,F4F, F6F, F8F and F4U all came with no wing wash-out, so that the wing generate the maximum amount of lift during a stall, while making the stall more tricky. Grummans provided F6F with a fair to good stall characterstic, by increasing its lateral stability to delay a stall roll-off from happening, while in turn sacrificed some roll-rate. The blow-up flaps were also designed to increase the lateral stability, especially during a wave-off.

Further explanation could also be made on the Fw-190, which is also an airplane used NACA 230 series, where I believe the aircraft may be somewhat mediocre in terms of CLmax at near stall speed, due to its relatively small Reynolds' number and weak laterall stability intentionally sacrificed for high roll-rate.The aircraft may get a good Reynold's number effect at higher airspeed and high pitch-rate of the aircraft. Which would partially explain the British accounts that Fw190 been able to stay on Spitfire's turn in some cases.

 

[wrathofatlantis]

Also, both the F6F and the P-47 had relatively large wing area but smaller aspect ratio (lower than 6), which gives them larger than average mean-aerodynamic chord, which would make the flight reynolds' number of both airplane larger than most single engine fighters under similar condition. This is very beneficial for the aircraft's maximum lift coefficient, and both airplanes were using NACA230 airfoil, which is the best conventional airfoil with high maximum lift, low drag and very low pitchming moment that further boost the trimmed CL in-flight. (Although Seversky S-3 airfoil on the P-47 may be slightly modified and comes with lower lift)

In comparison, the Japanese used older NACA 4 -digit airfoils NACA23 and 33 on the A6M, with 2 deg washout and forward CG position, which make the airplane probably mediocre in terms of CLmax, and the maneverability of the Zero mostly came from its low wing loading and good energy retention thanks to its aspect ratio. The Japanese viewed tha stall characterstics very high, thus exclusively used wash-out on wings that would harm the maximum lift, and relectant to use NACA 230 on fighters ( Ki-45 was an outlier) due to the bad stall type of the airfoil (the Brits also relectant to use it).

The USN fighters F2A,F4F, F6F, F8F and F4U all came with no wing wash-out, so that the wing generate the maximum amount of lift during a stall, while making the stall more tricky. Grummans provided F6F with a fair to good stall characterstic, by increasing its lateral stability to delay a stall roll-off from happening, while in turn sacrificed some roll-rate. The blow-up flaps were also designed to increase the lateral stability, especially during a wave-off.

Further explanation could also be made on the Fw-190, which is also an airplane used NACA 230 series, where I believe the aircraft may be somewhat mediocre in terms of CLmax at near stall speed, due to its relatively small Reynolds' number and weak laterall stability intentionally sacrificed for high roll-rate.The aircraft may get a good Reynold's number effect at higher airspeed and high pitch-rate of the aircraft. Which would partially explain the British accounts that Fw190 been able to stay on Spitfire's turn in some cases.

No, the FW-190A turned well exclusively at low speeds, below 220 mph ias, and its high speed elevator handling was the most spectacularly poor of all fighters in the War, because it generated high Gs by mushing nose up at 45 degrees AoA, and decelerated nose-up while in the turn or pull-out, without actually turning or pulling up proportionately to the large Gs generated on the pilot(!!), so it crushed you under deceleration Gs while maneuvering very little, an absolutely incredible combination...

Many people have trouble understanding this, because if the aircraft is "barely curving" how can it crush you?

It still crushes you because, throughout the loose curve an attitude of 45 or 50 degrees to the airflow, which is nearly the same as being sideways to the airflow, the whole airframe is acting as a giant brake while still only curving slightly. It IS curving a little, but nowhere near what justifies the immense decelerating loads it places on you. That is how Kurt Tank noted he generated one extra G of force for each 2 pounds of added backward stick force at 400 mph, 14 pounds for 7Gs, which is obviously abnormally light.... Ideal is considered to be 6-7 pounds, or 42 to 50 pounds. Heavy would be up to 100 pounds. fw-190A elevators are considered a bit heavy when it is flying normally....

This nose-up sinking behaviour is well-known, other types have less extreme variants of it like the P-47, but in the case of the fw-190A this high speed pilot-crushing "mushing" behaviour is so extreme that if you do not understand it you have really nothing to say about the handling of the fw-190A.

I'll provide some examples here:

Tactical and Technical trends no 37 (translated Russian summary of 1 year of combat): "After a dive of 1400 m at 40 degrees, the fw-190A falls an extra 220m (after nose up)..."

Eric Brown: "Care must be taken to not kill speed by sinking, or the fw-190 will be very vulnerable on pull-out."

Tactical and Technical trends no 37: "When going into the climb after a dive, there is a moment when the fw-190 "hangs": It is then convenient to fire."

P-47D-4 vs fw-190G-3 test: "The P-47 has a decidedly better angle of pull-out. [YET....] The fw-190 has a tendency to black-out the pilot..."

P-51D vs fw-190A dogfight: "He then made this very loose downward loop. On coming out of it the pilot must have been blacked-out, because he did not react to approaching tracers."


On the other hand, the fw-190A's massive preference for low speed turning is overwhelming, and it is getting tiresome to trot out the ever increasing evidence which never seems to get through (in the total absence of the Spitfire EVER winning low speed circles against it, not one single example found in 30 years of research):


On November 11th, 1942, Lt. (later Capt.) James E. Reed of the 33rd Fighter Group was piloting one of the 77 P-40Fs that was catapulted off the carrier 'Chenango,' a converted Great Lakes oil tanker, for a landing at an airport at Port Lyautey, 90 miles north of Casablanca, as part of Operation Torch:
"Regarding performance against the Me-109 and FW-190. The 190 was tough to out-turn. I could out-turn the 109, but it was hard to do. I, at times, had to drop a few degrees of flaps and slow down to out-turn it. On one mission dropping the flaps was not enough so I had to drop my landing gear to slow down enough to out-turn the Me-109 and get away from his fire. I think dropping the flaps and landing gear probably saved my life. I never had a one-on-one with the FW-190 so am not sure what I could do with it. I understand that it was harder to get away from than the Me-109."


Johnny Johnson "My duel with the Focke-Wulf": "With wide-open throttles I held the Spitfire [V] in the tightest of vertical turns [Period slang for vertical bank]. I was greying out. Where was this German, who should, according to my reckoning, be filling my gunsight? I could not see him, and little wonder, for he was gaining on me: In another couple of turns he would have me in his sights.---I asked the Spitfire for all she had in the turn, but the enemy pilot hung behind like a leech.-It could only be a question of time..."

And:

RCAF John Weir interview for Veterans Affairs (Spitfire Mk V vs FW-190A-4 period): "A Spit was a higher wing loading... The Hurricane was more manoeuvrable than the Spit and, and the Spit was probably, we (Hurricane pilots) could turn one way tighter than the Germans could on a Messerschmitt, but the Focke Wulf could turn the same as we could, and they kept on catching up, you know."

And:

"Red Fleet", a Russian journal, from Tactical and Technical Trends, No. 37, November 4, 1943. (based on one year of front line observations):
"-Being very stable and having a large range of speeds, the FW-190 will inevitably offer turning battle at a minimum speed."




View: https://youtu.be/c2zdA9TcIYo?si=-X5bCZ-y5qPOtYGY

at 12:44 :

Translation: "So there are legends on the Spitfire... Aaaah the legends... Legends are hard to kill... One of those legends is that the Spitfire turned better than the Messerschmitt 109, or the FW-190. Well that is a good joke... In fact all those who found themselves with a 109 turning inside them, at low speeds, well those in general did not come back to complain about the legend... Why? Above 280 to 300 knots, the Spitfire turned better than the Me-109. But, first and foremost, in a turning battle, the speed goes down and down and down and down, and at one point there comes a time, when the speed has gone down below 200 knots, that the Me-109 turns inside the Spitfire."

 

[Irregualr23]

No, the FW-190A turned well exclusively at low speeds, below 220 mph ias, and its high speed elevator handling was the most spectacularly poor of all fighters in the War, because it generated high Gs by mushing nose up at 45 degrees AoA, and decelerated nose-up while in the turn or pull-out, without actually turning or pulling up proportionately to the large Gs generated on the pilot(!!), so it crushed you under deceleration Gs while maneuvering very little, an absolutely incredible combination...

Many people have trouble understanding this, because if the aircraft is "barely curving" how can it crush you?

It still crushes you because, throughout the loose curve an attitude of 45 or 50 degrees to the airflow, which is nearly the same as being sideways to the airflow, the whole airframe is acting as a giant brake while still only curving slightly. It IS curving a little, but nowhere near what justifies the immense decelerating loads it places on you. That is how Kurt Tank noted he generated one extra G of force for each 2 pounds of added backward stick force at 400 mph, 14 pounds for 7Gs, which is obviously abnormally light.... Ideal is considered to be 6-7 pounds, or 42 to 50 pounds. Heavy would be up to 100 pounds. fw-190A elevators are considered a bit heavy when it is flying normally....

This nose-up sinking behaviour is well-known, other types have less extreme variants of it like the P-47, but in the case of the fw-190A this high speed pilot-crushing "mushing" behaviour is so extreme that if you do not understand it you have really nothing to say about the handling of the fw-190A.

I'll provide some examples here:

Tactical and Technical trends no 37 (translated Russian summary of 1 year of combat): "After a dive of 1400 m at 40 degrees, the fw-190A falls an extra 220m (after nose up)..."

Eric Brown: "Care must be taken to not kill speed by sinking, or the fw-190 will be very vulnerable on pull-out."

Tactical and Technical trends no 37: "When going into the climb after a dive, there is a moment when the fw-190 "hangs": It is then convenient to fire."

P-47D-4 vs fw-190G-3 test: "The P-47 has a decidedly better angle of pull-out. [YET....] The fw-190 has a tendency to black-out the pilot..."

P-51D vs fw-190A dogfight: "He then made this very loose downward loop. On coming out of it the pilot must have been blacked-out, because he did not react to approaching tracers."


On the other hand, the fw-190A's massive preference for low speed turning is overwhelming, and it is getting tiresome to trot out the ever increasing evidence which never seems to get through (in the total absence of the Spitfire EVER winning low speed circles against it, not one single example found in 30 years of research):


On November 11th, 1942, Lt. (later Capt.) James E. Reed of the 33rd Fighter Group was piloting one of the 77 P-40Fs that was catapulted off the carrier 'Chenango,' a converted Great Lakes oil tanker, for a landing at an airport at Port Lyautey, 90 miles north of Casablanca, as part of Operation Torch:
"Regarding performance against the Me-109 and FW-190. The 190 was tough to out-turn. I could out-turn the 109, but it was hard to do. I, at times, had to drop a few degrees of flaps and slow down to out-turn it. On one mission dropping the flaps was not enough so I had to drop my landing gear to slow down enough to out-turn the Me-109 and get away from his fire. I think dropping the flaps and landing gear probably saved my life. I never had a one-on-one with the FW-190 so am not sure what I could do with it. I understand that it was harder to get away from than the Me-109."


Johnny Johnson "My duel with the Focke-Wulf": "With wide-open throttles I held the Spitfire [V] in the tightest of vertical turns [Period slang for vertical bank]. I was greying out. Where was this German, who should, according to my reckoning, be filling my gunsight? I could not see him, and little wonder, for he was gaining on me: In another couple of turns he would have me in his sights.---I asked the Spitfire for all she had in the turn, but the enemy pilot hung behind like a leech.-It could only be a question of time..."

And:

RCAF John Weir interview for Veterans Affairs (Spitfire Mk V vs FW-190A-4 period): "A Spit was a higher wing loading... The Hurricane was more manoeuvrable than the Spit and, and the Spit was probably, we (Hurricane pilots) could turn one way tighter than the Germans could on a Messerschmitt, but the Focke Wulf could turn the same as we could, and they kept on catching up, you know."

And:

"Red Fleet", a Russian journal, from Tactical and Technical Trends, No. 37, November 4, 1943. (based on one year of front line observations):
"-Being very stable and having a large range of speeds, the FW-190 will inevitably offer turning battle at a minimum speed."




View: https://youtu.be/c2zdA9TcIYo?si=-X5bCZ-y5qPOtYGY

at 12:44 :

Translation: "So there are legends on the Spitfire... Aaaah the legends... Legends are hard to kill... One of those legends is that the Spitfire turned better than the Messerschmitt 109, or the FW-190. Well that is a good joke... In fact all those who found themselves with a 109 turning inside them, at low speeds, well those in general did not come back to complain about the legend... Why? Above 280 to 300 knots, the Spitfire turned better than the Me-109. But, first and foremost, in a turning battle, the speed goes down and down and down and down, and at one point there comes a time, when the speed has gone down below 200 knots, that the Me-109 turns inside the Spitfire."

After several discussions with my friends and yes there were many more accounts that mentioned the "sinking" property of the Fw190, and its ability to perform some wild "snap" manuevers. There was an account in which, a Tempest outturned a Fw190D in 3 turns, and only to be find out that the Dora did a strange snap over in the middle of his turn, and suddenly forced a head-on, and that Dora was able to perform the same manuever 4 times, all of which below 3000ft.

This property is very surprising. As commonly believed that Fw190 is relatively bad at turning, and with a tendency to roll off during an accelerated stall. Yet comments on Fw190's capability diverges so wildely that I haven't found a proper explanation for this, as the wind tunnel test record from the Fw190 was avaliable, this aircraft should behave normally as tapered wing NACA230 fighter. Technically there should be no ww2 era fighter to be able to perform a controllable post-stall maneuver. The only reasons behind may be Reynolds' number effect and different trim setting.

 

[wrathofatlantis]

Very interesting this account of the FW-190D-9 being able to snap stall/turn to compensate its lesser turn rate and radius....

It is widely reported that the D-9 did not sustain low speed turns as well as the A.

-1946 US evaluation of FW-190D-9: "1-The FW-190D-9, although well armored and
equipped to carry heavy armament, appears to be much less desirable from a handling
standpoint than other models of the FW-190 using the BMW 14 cylinder radial engine."

-"The JG 26 War Diary Volume Two 1943-1945"; (pages 388 – 399): "The pilot's opinions of
the "long-nosed Dora", were mixed. The new airplane lacked the high turn rate and
incredible rate of roll of its close-coupled radial-engined predecessor."

-Audio from the past [E16], Pierre Clostermann: "The D-9 was of magnificent beauty.
However, in its case, it did not turn as well as the "normal" 190, because of its longer nose."

Yet.... Clostermann also said (to my long-standing confusion): "It did not turn as well, but the pilot seemed to be able to get it to do what he wanted."

Which, in light of the account you provided, suddenly lifts the veil on that particular contradiction... Which I consider a major breakthrough in my understanding of the D-9....


Of note about the regular 190A wing drop, a direct account from a pilot through his relative (which pilot unfortunately did not want to give his name because he described shooting down Allied aircrafts) describes turns on the 190A as being performed with the following steps:

1-Seriously reduce power before the merge (of course... What else is new?).

2-Set flaps to take off position (about 20 degrees).

3-Engage exclusively in low speed turn fighting, facing head to head into each attack if the attacker refuses to follow the turn (which often happened with the P-51)...

4-He could choose between 3 different chord of ailerons (about a 1 inch difference each at the trailing edge, visible in period photos outboard of the trim tab), and always chose the widest one because it had the best "bite" at low speed.

This is the crucial part: During a turn, once he sensed the wing dropping, he would deflect the ailerons to "catch" the stall, then ride his low powered turn on deflected ailerons...

Another crucial thing to consider is that at low speed Eric Brown describes the short-nose A-4 as "self-tightening" the turn below 220 knots ias, meaning he had to PUSH on the stick to maintain turning. This means that on an A-4, possibly even the 6 inch longer-nose A-8, he not only rode the turn with the stick to the side to catch the wing drop, but also slightly forward...

And keep in mind that most FW-190As, although much quieter in the cockpit than in-lines (like most radials), often had a slight vibration in the control stick that killed the hand's sense of touch... So all this meant that you could be at low altitude in a turn, power reduced, with 20 degrees of flaps, stick forward and sideways, and to compound all this you might, at some rpms, have only your arm/wrist muscle feel, not your sense of touch, to keep all of it balanced... I'm sure one could get used to it, but it did require a cool head.

It is not surprising some P-51 pilots describe 190A pilots as "being afraid to reef it in". Because they were pushing!... (This actually depended on the fuel tank selection valve: Neutral or forward selection made the 190A nose light, while selecting rear tank consumption tended to minimise this low speed "self-building nose rise", the two tanks being essentially front-to-back under the pilot.)

Of note is that while hard right turns at high speed were extremely poor on the 190A (the resulting wing drop stall being actually an escape "trick"), at low speeds it was the P-51 that turned much worse to the right in sustained low speed turns, to the point the more "low-speed symmetrical" 190A is described as reversing a tail position P-51D in 3 X 360s, in low speed right turns only, which is incredibly fast.

The stick vibration appeared only at some rpms, so maybe it left the control stick alone at some of the settings... Still, all these aspects illustrate why not every pilot was able to get the best out of the 190A, while the slower turning D-9 had no serious stick vibration and appeared to reward a less gradual and more intuitive "trashing about" fighting style...

 

[Bolingbroke10070]

What do the M and N manuals say? Note it calls it an F-47D-30RE which means post war. Lots of mods probably made on these by then.

The DC-9 family of airliners have the blow back feature. It is there to prevent unintended damage and would never be relied on. No, it does not move the handle or anything like that. Its operation would be transparent to you unless you were closely looking at the flap position indicator. I imagine that in my 12000 hours of flying that family of aircraft the feature never used itself once.

Good topic on my favorite single engine type.

 

[Mfezi]

No, the FW-190A turned well exclusively at low speeds, below 220 mph ias, and its high speed elevator handling was the most spectacularly poor of all fighters in the War, because it generated high Gs by mushing nose up at 45 degrees AoA, and decelerated nose-up while in the turn or pull-out, without actually turning or pulling up proportionately to the large Gs generated on the pilot(!!), so it crushed you under deceleration Gs while maneuvering very little, an absolutely incredible combination...

I know I am going to regret asking this after our previous discussion on the Spitfire control stick (that happened to be similar to the Hurricane, Typhoon, Tempest, Hunter and others), but where did you get the 45 degrees AoA in a pull-out from? An aircraft like a Fw-190 would stall somewhere between 18 and 20 degrees AoA (that is flaps up - usually a bit lower flaps down). The higher dynamic pressure of propeller flow over a wing can sometimes increase the stall angle of attack slightly, but it wouldn't get you even to 25 degrees - nowhere near the 40's - at least not in an aircraft with the Fw-190's wing geometry. Similarly, in a dynamic pitching maneuver a wing can sometimes exceed its 1G stall AoA momentarily before it departs, but this wouldn't bring the Fw-190 anywhere near 45 deg AoA - not even half of that.

We also know that we are not talking about departed flight here: Some of the later discussion in this thread deals with departures, but not when talking about a steady turn or steady pull-out from a dive, which by definition only involves controlled flight.

I went through everything that you wrote subsequently to try and find where you could possibly have gotten the "45 degrees AoA" number from, and all I could come up with was this quote:

Tactical and Technical trends no 37 (translated Russian summary of 1 year of combat): "After a dive of 1400 m at 40 degrees, the fw-190A falls an extra 220m (after nose up)..."

But the above quote clearly doesn't suggest a 45 degrees AoA. The pilot describes a pull-up from a dive angle that was 40 degrees prior to initiating the pull-up. The moment he starts pulling, the dive angle would also start to decrease. Like any aircraft, the pitch angle will lead the dive angle and the difference is the instantaneous angle of attack (assuming the wings are level, which they would be for a symmetrical pull-up maneuver). What the pilot above describes - in your version at least - is that, after the Fw-190's nose pitched through the horizon, it continued to lose another 220m before the descent bottomed out. At the particular moment where the nose pitched through the horizon, assuming the pilot was approaching the maximum angle of attack of the aircraft, the dive angle would already have decreased to around 15 to 18 degrees. The pilot would then have maintained that high AoA until the aircraft started to climb, after which he would have released the back pressure on the stick gradually. Therefore, when he hit the bottom of the descent, the nose would have been pitched up by around 15+ degrees which would certainly look like mushing, but all of course perfectly controlled.

By the way, here is the actual quote from the translation: "At times it happens that the FW, after diving, does not gain altitude, but attempts to drop out of the battle altogether in low flight. However, the FW-190 is never able to come out of a dive below 300 or 250 meters (930 ft or 795 ft). Coming out of a dive, made from 1,500 meters (4,650 ft) and at an angle of 40 to 45 degrees, the FW-190 falls an extra 200 meters (620 ft)." It was you that added the "after nose up", there was no such suggestion in the original version. In reality, it is probably measured from the moment the pull-out was initiated. Again, nothing to suggest anything about extreme angles of attack.

I have a lot of experience testing delta-winged fighter jets (as a flight dynamics and handling engineer, not flying it myself). If you think this mushing in the pull-out on a Fw-190 was bad, you should see what it looks like on heavily loaded delta.

Just something else that jumped out at me:

so it crushed you under deceleration Gs

Deceleration G's throw you forward in the cockpit. Normal acceleration (from turns and pull-ups) push you down in the seat. Acceleration G's push you back in the seat. Deceleration at high angles of attack would still pull you forward and a small component would push you down in the seat (it is proportional to the sine of the angle of attack), but nowhere near to what you experience when turning at high G or the normal acceleration that you would experience in a pull-out. How can deceleration G's "crush you" in the case that you describe? Did you try to work out the numbers? I suspect both the deceleration (in m/s^2) and the angle of attack (in deg) that goes into the equation are much smaller than you seem to think they are.

 

[wrathofatlantis]

I went through everything that you wrote subsequently to try and find where you could possibly have gotten the "45 degrees AoA" number from, and all I could come up with was this quote:

But the above quote clearly doesn't suggest a 45 degrees AoA. The pilot describes a pull-up from a dive angle that was 40 degrees prior to initiating the pull-up. The moment he starts pulling, the dive angle would also start to decrease. Like any aircraft, the pitch angle will lead the dive angle and the difference is the instantaneous angle of attack (assuming the wings are level, which they would be for a symmetrical pull-up maneuver). What the pilot above describes - in your version at least - is that, after the Fw-190's nose pitched through the horizon, it continued to lose another 220m before the descent bottomed out. At the particular moment where the nose pitched through the horizon, assuming the pilot was approaching the maximum angle of attack of the aircraft, the dive angle would already have decreased to around 15 to 18 degrees. The pilot would then have maintained that high AoA until the aircraft started to climb, after which he would have released the back pressure on the stick gradually. Therefore, when he hit the bottom of the descent, the nose would have been pitched up by around 15+ degrees which would certainly look like mushing, but all of course perfectly controlled.

By the way, here is the actual quote from the translation: "At times it happens that the FW, after diving, does not gain altitude, but attempts to drop out of the battle altogether in low flight. However, the FW-190 is never able to come out of a dive below 300 or 250 meters (930 ft or 795 ft). Coming out of a dive, made from 1,500 meters (4,650 ft) and at an angle of 40 to 45 degrees, the FW-190 falls an extra 200 meters (620 ft)." It was you that added the "after nose up", there was no such suggestion in the original version. In reality, it is probably measured from the moment the pull-out was initiated. Again, nothing to suggest anything about extreme angles of attack.

This is how I typed it:

"After a dive of 1400 m at 40 degrees, the fw-190A falls an extra 220m (after nose up)..."

I had added parenthesis, which is a fair suggestion that it was added by me. And it is all the more fair in that it is true... There is no other interpretation that makes sense.

Read the preceding sentence: The Fw-190A is NEVER able to come out of a dive below 900 to 800 feet: No angle is low enough, no speed is low enough.

You simply do not grasp the incredible scale of the 190A's sinking... I have read US 8th AF pilots say that if the FW-190A does not begin his observable pull-out at 8000 feet, it will "pancake" itself on the ground.

Sure, maybe the 8000 foot dive was a bit faster, but do you really grasp the scale of the problem when you say that a dive of 1500 m, four thousand five hundred feet(!), at 40-45 degrees no less, was resolved in 660 feet from the moment of visually observable initiation? (They are strictly talking combat-observed behaviour in this document...)

400 mph is 178 m/s, at 45 degrees that means nearly 90 m/s of vertical velocity, so by your count this (extremely conservative) dive, which was probably much faster, was reduced to a level trajectory in 220 metres, or 2.5 seconds?

In a document that implies that other aircrafts are better at it?

In a document that makes it a point to describe how poorly it pulls out of dives, but also at the start of climbs?:

"A shortcoming of the FW-190 is its poor climbing ability. When climbing in order to get an altitude advantage over the enemy, there is a moment when the FW-190 "hangs" in the air. It is then convenient to fire."

Getting back to the 8th AF pilots and their claim that an 8000 feet initiation was the minimum to not "pancake".

"Pancaking" means hitting the ground in a level attitude at best, 7000 foot after the visible observation of the initial dive recovery action.. It also implies strongly no skidding and relatively little forward motion.

Now if you start arguing that "pancaking" still implies a lot of forward motion, which justified replacing "crashing" or "skidding" with the word "pancake", then I am going to start thinking you are willing to see things that just aren't there. Pancakes are not known for their forward speed....

This is a failure to level off after 7000 feet, and you say it succeeded in 660 feet by changing the intended meaning? Do you see how far off reality you have to go to make your interpretation hold up?

"Falls an EXTRA 220 metres" is extra to what should have been zero. Otherwise it would say "It took 220 metres from the observed initiation to level off."

Granted, this is a 1940s translation, but it does not strike me as low quality nonsense.

Extra just means extra, and also note the combination with the word "falls": An aircraft that is nose down can be said to fall, but the "fall" in that case cannot be considered "extra"...

I have a lot of experience testing delta-winged fighter jets (as a flight dynamics and handling engineer, not flying it myself). If you think this mushing in the pull-out on a Fw-190 was bad, you should see what it looks like on heavily loaded delta.

Just something else that jumped out at me:

Deceleration G's throw you forward in the cockpit. Normal acceleration (from turns and pull-ups) push you down in the seat. Acceleration G's push you back in the seat. Deceleration at high angles of attack would still pull you forward and a small component would push you down in the seat (it is proportional to the sine of the angle of attack), but nowhere near to what you experience when turning at high G or the normal acceleration that you would experience in a pull-out. How can deceleration G's "crush you" in the case that you describe? Did you try to work out the numbers? I suspect both the deceleration (in m/s^2) and the angle of attack (in deg) that goes into the equation are much smaller than you seem to think they are.

Could it be instead that it is the opposite way? That the FW-190A is in fact way nose up and still going down at a 70 to 80 degrees AoA?

Also, consider that the FW-190A seat was considerably tilted back, by around 10 degrees, which means that a 60 AoA was in reality 70 degrees on the pilot.

My interpretation is that the FW-190A at high speeds easily reared up to 70 degrees, and this easily placed an 80 degree deceleration on the pilot, although not necessarily all the way down.

Note the wording of the P-47D-10 vs FW-190G-3 test:

Stability and control committee, "S.C. 1718", 24 April 1944:



"The FW-190 vibrated excessively and had a tendency to black out its pilot."

Yet this did not apply to the P-47, despite the following:

"The P-47 had a much greater speed and a decidedly better angle of pull out ."(after 3000 ft. in a 65 degree dive)."

So the P-47 makes a tighter pull-out, but does not have a tendency to black out the pilot?




What is your interpretation of that?




If you selected the switch to "neutral" tank consumption rather than "rear" -on the short-nosed A-4s at least- (two tanks pumping together, front to back under the pilot), you had to make turns below 220 knots ias by pushing on the stick... 6 inch longer nose A-8s gained an extra fuel tank behind the pilot which cannot have helped this behaviour... (Unlike the 109, that tank was never used for extra boost, just fuel: 1.58 ATA boost only existed operationally on the A-8 as a trick in the throttle linkage.)

At high speed that thing was just on a knife edge to go "rear down" massively if you pulled too hard, and that does match "A tendency to black-out the pilot".

And just because the wing is at 60 or 80 degrees of AoA does not mean it physically disappears... How do you think the FW-190D-9 achieved the Battlestar Galactica 180 degrees instant "Viper" turns described earlier this thread? (These were after 3 circles, so not very high speed) I doubt it was all from the rudder...

The reality is that jets are a poor approximation of what these things were like.

 

[ThomasP]

re

The reality is that jets are a poor approximation of what these things were like.

Physics is physics, and aerodynamics (which is a specialized field of physics) is aerodynamics. The laws of physics apply to modern jet aircraft in the same way that they do to modern prop jobs, and in the same way they did to WWII jets and to WWII prop jobs.

Mfezi is correct in his post.

 

[Mfezi]

You simply do not grasp the incredible scale of the 190A's sinking... I have read US 8th AF pilots say that if the FW-190A does not begin his observable pull-out at 8000 feet, it will "pancake" itself on the ground.

Do you mind providing a cite for that claim? It seems very unlikely - 8000 feet? Under what conditions, a vertical dive approaching or exceeding VNE? Without context this claim really doesn't add anything.

Sure, maybe the 8000 foot dive was a bit faster, but do you really grasp the scale of the problem when you say that a dive of 1500 m, four thousand five hundred feet(!), at 40-45 degrees no less, was resolved in 660 feet from the moment of visually observable initiation? (They are strictly talking combat-observed behaviour in this document...)

I am happy to continue then with your version, namely that the measurement was taken from the point when the nose pitched through the horizon, which is exactly what I responded to in the first paragraph. So, I retract my "probably" in the short paragraph that started with "by the way" and we can stay with what I wrote in the paragraph before that.

400 mph is 178 m/s, at 45 degrees that means nearly 90 m/s of vertical velocity...

178 x sin (45) = 125.9 m/s vertical velocity component. In a 30 deg dive it would have been 89 m/s. Best to check your math before you post. But it doesn't affect the rest of the discussion: As I said, my main argument was already based on your assumption that the measurement starts when the nose pitches through the horizon.

"A shortcoming of the FW-190 is its poor climbing ability. When climbing in order to get an altitude advantage over the enemy, there is a moment when the FW-190 "hangs" in the air. It is then convenient to fire."

This does not suggest a 45 deg AoA in any way. From the perspective of a high speed pursuer, the high AoA pull-out (15 to 18 degrees, not 45 degrees) of the Fw-190 in front of him presents him with an excellent target and it is going to be especially vulnerable at that moment when it transitions from the pull-out to the climb, still at high AoA. Remember, during that first part of the climb the AoA may only be 15 to 18 degrees, but his flight path is now upwards - so his pitch angle relative to the horizon is much higher than his angle of attack. For the pursuer who is in a slight dive at that moment with a healthy overtake velocity, it will present an excellent planform to shoot at.

"Pancaking" means hitting the ground in a level attitude at best, 7000 foot after the visible observation of the initial dive recovery action.. It also implies strongly no skidding and relatively little forward motion.

That is one definition...

Now if you start arguing that "pancaking" still implies a lot of forward motion, which justified replacing "crashing" or "skidding" with the word "pancake", then I am going to start thinking you are willing to see things that just aren't there. Pancakes are not known for their forward speed....

"Pancake" is not a formal aeronautical term, but it is very commonly used to describe an aircraft impacting the ground in a nose-high attitude combined with a high rate of descent. It doesn't imply low speed or high speed. An aircraft hitting the ground in a nose-high attitude from a deep stall with almost no forward speed can be said to have "pancaked". An aircraft hitting the ground in an almost flat attitude with no forward speed in a flat spin will also sometimes be described as having "pancaked". Those two situations imply low forward speed. But an aircraft hitting the ground at high speed at the bottom of a misjudged loop with the nose already above the horizon would also be described as having "pancaked" - and I have lots of accident reports in my possession that describe it thus. It is used to describe the aircraft's attitude/flight path combination at the moment of impact, not its speed. And what it certainly does not do is put a number to its angle of attack.

Could it be instead that it is the opposite way? That the FW-190A is in fact way nose up and still going down at a 70 to 80 degrees AoA?

I think you are now deliberately trolling. The 45 degrees claim is already ridiculous enough.

Also, consider that the FW-190A seat was considerably tilted back, by around 10 degrees, which means that a 60 AoA was in reality 70 degrees on the pilot.

Are you really going to stick with 60 and 70 degrees AoA now, in a controlled pull-up?

My interpretation is that the FW-190A at high speeds easily reared up to 70 degrees, and this easily placed an 80 degree deceleration on the pilot, although not necessarily all the way down.

The only time when that kind of angle of attack can possibly be experienced with a conventional propeller driven aircraft, is when you allow the speed to drop to near zero at the top of a vertical climb, let it pitch forward in the recovery and it will briefly pass through extreme angles of attack and near zero airspeed before the nose falls through and the speed starts to build up again.

There are situations where that type of AoA can be achieved on modern aircraft in a controlled or at least semi-controlled fashion: With thrust vectoring aircraft like the F-22 or Su-57, or with aircraft that have a natural tendency to pitch forward out of extreme angles of attack such as the MiG-29, Su-27 and, to a lesser extent, the F-18. However, the cobra maneuver implied in these cases don't occur at the bottom of each pull-out from a dive. It is a deeply stalled condition and requires the pilot to pitch forward out of the stall and apply power before a climb can commence, and the only reason a climb is even possible after those maneuvers is that all these aircraft have ridiculous thrust-to-weight ratios to climb from almost zero airspeed, unlike the Fw-190.

What you describe is literally not physically possible. In almost 30 years in aircraft development and being involved in one way or another with the flight testing of everything from unmanned aircraft, a wide range of fighter and trainer jets, various guided weapon systems, two different turboprop trainers, a turboprop light attack aircraft, and several civilian aircraft including high performance aerobatic aircraft, here is a complete list of all the times when I saw behaviour that defied our current understanding of the physics involved:

Start of list...
...End of list

Let's just say I find it unlikely that your reading of a few pilot reports suddenly revealed some new physics that we were not aware off. Physics where you can pitch into a deep stall during a symmetrical pull-out from a dive with a WW2 fighter, and as you pass through maximum lift coefficient at high speed, the wing doesn't fail structurally. Then you maintain control throughout this high speed deep stall, wings perfectly level and, once you reach the bottom of the pull-out, still in a high speed deep stall condition, there is somehow sufficient airspeed, control and thrust available to transition to a climb. And again, we are not talking about a thrust-vectored F-22, this supposedly happened regularly on a propeller driven WW2 fighter plane.

"The FW-190 vibrated excessively and had a tendency to black out its pilot."

Blacking out of a human happens when the blood drains into the lower extremities so that the brain cannot get sufficient oxygen. It happens with manoevres that specifically generate large positive normal acceleration. There are many factors that affect it, the pilot's seating angle being one of them. But it is also affected by pilot fitness and health, repeated high G manoeuvres in close succession, rate of G-onset, pilot's use of anti-G straining (which can be affected by the ergonomics in the seat) and various other factors. Without a deep analysis of why the FW-190 supposedly had a unique tendency to "black out its pilot", it is impossible to draw any conclusion at all. Unless you can point me to such a detailed analysis, this comment is nothing more than an anecdote.

So the P-47 makes a tighter pull-out, but does not have a tendency to black out the pilot?

See above. Lacking a detailed analysis, these are just anecdotes. Your explanation that involves Star Wars physics is probably the least likely explanation for any difference that these two aircraft may or may not have in causing their pilots to black out.

And just because the wing is at 60 or 80 degrees of AoA does not mean it physically disappears... How do you think the FW-190D-9 achieved the Battlestar Galactica 180 degrees instant "Viper" turns described earlier this thread? (These were after 3 circles, so not very high speed) I doubt it was all from the rudder...

Who said anything "physically disappears"? I used the word "depart" which, unlike "pancake", is actually standard aeronautical terminology which you will often encounter in formal reports. And yes, I don't buy the Battlestar Galactica physics anymore than any other Hollywood physics presented here by you.

The reality is that jets are a poor approximation of what these things were like.

Indeed, unlike WW2 fighters like the Fw-190 with straight wings and medium to high aspect ratios, fighter jets like the deltas that I mentioned before are actually able to achieve very high angles of attack in controlled, undeparted flight. But those "high angles of attack" are in the 20 to 30 degrees range, sometimes a little higher, and it is made possible by aerodynamic characteristics that are absent on the Fw-190 like leading edge vortices coming off the root of delta wings at high AoA that keep the flow on the wing attached and similar characteristics due to the leading edge extensions on aircraft like the F-18. As stated earlier, some jets can also achieve even higher angles of attack in departed flight with sufficient control and power to recover from these conditions quickly. You throw angle of attack numbers around as if the jump from 20 to 30 degrees is no big deal, and from there on to 45 and on now even to 80.

 

[Irregualr23]

Adding more records for combat flap usage on F6F-5, it seems my theory was wrong, pilot did share the experience of using flaps during a turn fight till late war:

F6F-5N used flaps to turn with Ki-43:

F6F-5 used flaps to turn with Ki-84:

 

[wrathofatlantis]

Adding more records for combat flap usage on F6F-5, it seems my theory was wrong, pilot did share the experience of using flaps during a turn fight till late war:

F6F-5N used flaps to turn with Ki-43:

View attachment 877993

F6F-5 used flaps to turn with Ki-84:
View attachment 877994

I wonder if "dropping" in this case might have been applied to just extending them horizontally? Just horizontal extension on the Hellcat, without any angle, was definitely an option. What were the angle with speed deployment limits of the Hellcat at 10 or 20 degrees? Pretty spectacular that it turned inside an Oscar with all that added stuff... "turning inside" is not circles though.

 

[Irregualr23]

I wonder if "dropping" in this case might have been applied to just extending them horizontally? Just horizontal extension on the Hellcat, without any angle, was definitely an option. What were the angle with speed deployment limits of the Hellcat at 10 or 20 degrees? Pretty spectacular that it turned inside an Oscar with all that added stuff... "turning inside" is not circles though.

I've only saw the case that NACA's fowler flap was allowed for horizontal extension only and was tested in a theoritical calculation as a candidate of the combat flap based on data obtained for an F4F:

As for different flap mode that allows pilot to select different "gap" of a slotted flap, I've quoted the case of combat flap on N1K and A7M as the case in the following link to the thread:

The N1K2-J Shiden Kai vs Its US Counterpart

The Nakajima's butterfly flap is of classical fowler flap, which the flap was a part of lower part of flap with the trailing edge of the wing not moving. The flap on N1K and A7M are of slotted type and I just have another look on it and discovered an unusal feature --- they have two different...

ww2aircraft.net

 

[Sabrejet]

in the interest of verifying if Chat GPT could sort this out,

Worrying. If in doubt, ALWAYS consult Primary Sources first. In the event of non-availability of Primary Sources, consult Secondary Sources (books, magazines), but accept with caution. Chat GPT, Wikipedia etc are the realm of (at best) 'information' of dubious value and of often unknown derivation.