Aces High Bulletin Board
General Forums => Aircraft and Vehicles => Topic started by: Kazaa on December 24, 2009, 02:33:40 AM
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Did WW2 planes really have them?
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The spit was reputedly prone to over wing noise as stall approached. Some folk replace the stall sound wave file with a buffet sound
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Did WW2 planes really have them?
For what it's worth, I have WWII Training Videos of both the P-47 Razorback (I think it's a C) and the F4U-1(A?) and when both videos discuss stall charactersitics, neither of them mentions a stall horn, even when listing warning signs before a stall. Also, when the aircraft is filmed during a stall, I believe an in-cockpit clip is shown, and no stall horn is heard, though engine noise can account for that. However, from this, no I do not believe the average aircraft had a stall horn.
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No. Nor did they have G-Meters. But they DID have hands on actual sticks mechanically connected to actual controls surfaces giving tactile sensations, and actual butts in actual seats. So something must be done to compensate. ;) Remember, even with compensations, sims are still harder to fly than airplanes.
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Kazaa in a real plane when the stall starts at the wing root you can "Feel" the airflow breaking up, becoming turbulent.
Both in the stick, and in the seat of your pants.
AH as a sim has all too few clues as to our planes behavior as it is.
So I totally agree with what BnZs said. With no real world feedback, compensations have to be made.
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Most airplanes exhibit some buffet that is felt by the pilot. This is caused by the start of air flow separation over the wing root hitting the tail surfaces. Here is a video showing the buffet on a Mustang. (http://www.dalefalk.com/Movies/Mustang/7506324_6taqB#484642764_suoh2) In the Mustang it starts as a light buzz of the stick and gets more pronounced as you get closer to the stall. In the B-17 it shakes...I'm talking knock your false teeth out shake. :D
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Did WW2 planes really have them?
Some aircraft dating to WWII, usually transports, were fitted with "stall shakers". Stall shakers are little more than vibrators installed to shake the yoke. These were switched on using simple paddle airflow switch mounted on the wing's upper surface, close to the leading edge. When the angle of attack reaches the point where airflow to the switch is disturbed or significantly reduced, there is insufficient aero loading on the switch paddle to keep the contacts open. When the contacts close, power is supplied to the vibrator. C-54s were fitted with a stall shaker system as were some Grumman amphibians.
My regards,
Widewing
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Thanks guys.
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;) Remember, even with compensations, sims are still harder to fly than airplanes.
Chuckle.
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There were no stall warning horns on any WW2 aircraft, only 'undercarriage not down' audible warnings. The Spitfire and Hurricane's operated when the throttle was closed to less than 1/3 open with the mainwheels still up, which drove the pilots nuts whenever they chopped the throttle to descend or slow down, so they disabled the device, leading to the loss of quite a number of aircraft when their drivers forgot to both reactivate the warning horn and select 'undercarriage down', hoho.
:cool:
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Hello Kazaa
Like some of the fellaz mentioned the planes would give a sign that it was about to stall.From what I have read and as Tilt mentioned the Spitfire was good for giving warning signs that it was about to stall.This enabled the pilots to push it to the edge with a certain amount of safety.On the other hand I have read of some planes that would give little or no warning and would just stall out when pushed over the limit.Those guys obviously had to be more careful how hard they pushed theyre aircraft especially when they were at very low altitude.The stall horn in AH is one of the substitutes for those warnings.
Pipz
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Well , that's good to know ...
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In the movie "Battle of Britain" there is a scene where the pilot forgets to put the UC down. He got warned with a flare.
This actually happened to a pilot I knew. Same there, fire the Very-gun ;)
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Re gear not down. Lavochkins had a red pin that was pushed out (proud of) the wing when the gear was down. It was activated by a cam off the gear hinge point. The pilot had to look out across each wing to see if that gear was fully down or not. Cockpit indicators merely stated whether the gear down activators (hydraulics) were under pressure or not.
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Re gear not down. Lavochkins had a red pin that was pushed out (proud of) the wing when the gear was down. It was activated by a cam off the gear hinge point. The pilot had to look out across each wing to see if that gear was fully down or not. Cockpit indicators merely stated whether the gear down activators (hydraulics) were under pressure or not.
That's cool--I love simple solutions to complicated problems
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Re gear not down. Lavochkins had a red pin that was pushed out (proud of) the wing when the gear was down. It was activated by a cam off the gear hinge point. The pilot had to look out across each wing to see if that gear was fully down or not. Cockpit indicators merely stated whether the gear down activators (hydraulics) were under pressure or not.
IIRC the early mig jets used this same system.
:salute
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the Japanese used a similar pin system in their planes too - I believe the design was originally American, with the right sold to the Japanese Empire in the mid 30s but I can't be arsed to check now.
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P-51 Mustangs would experience elevator buffet as they approached a stall with a faster speed at stall meaning a more violent buffet. The Mustang also has an audible horn (as well as the warning lights) when the gear is up and the throttle is reduced to minimum and this can be cleared with a cut-out switch but anytime the throttle is moved forward again the horn is also reset.
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just curious but as stated earlier, since the wing root stalls first before the tips and ailerons. once stall speed is reached would not this result in the mushy or violent nose down effect instead of the roll which occurs some times... it was even said that a p-51 would stall so violently nose down at a stall that the pilot would bang there head on the canopy (not sure where i saw this). however it seems a barrel roll to inversion with slight nose down effect afterward will generally be the outcome of a stall here... curious
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According to the manual:
A stall in the P-51 is comparatively mild. The airplane does not whip at the stall but rolls rather slowly and has very little tendency to drop into a spin. When a complete stall is reached a wing drops. After that if you continue to pull back on the stick the airplane falls off into a steep spiral.
When you release the stick and rudder the nose drops sharply and the airplane recovers from the stall almost instantly.
There is more but thats the basics... HTC is about as spot on as anyone could get.
By the way your supposition is incorrect about the root stalling first. It is true of wingforms like the Spitfire that the tip stalls very early which is why it has washout. In the case of the P-51 the tips stall first with the rest of the wing quickly following but in cases where the wing is even more rectangular you can get root stalls.
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just curious but as stated earlier, since the wing root stalls first before the tips and ailerons. once stall speed is reached would not this result in the mushy or violent nose down effect instead of the roll which occurs some times... it was even said that a p-51 would stall so violently nose down at a stall that the pilot would bang there head on the canopy. however it seems a barrel roll to inversion with slight nose down effect afterward will generally be the outcome of a stall here...curious
My guess as to the roll is the way the wing stalls matched with the torque. The way the aircraft reacts, i.e. roll vs drop is plane specific. IIRC, the F4U was known to have a NASTY snaproll when stalling (Based on what I can recall of the F4U training video I have) where one wing just drops, whereas the P-47 just drops straight down without any tendency to roll (based on a similar P-47 training film).
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Re gear not down. Lavochkins had a red pin that was pushed out (proud of) the wing when the gear was down. It was activated by a cam off the gear hinge point. The pilot had to look out across each wing to see if that gear was fully down or not. Cockpit indicators merely stated whether the gear down activators (hydraulics) were under pressure or not.
are they modelled on our LAs like they are on our spits? iirc all our spits have these pins, although I'm pretty sure anything with a C or E wing shouldnt have them. not sure about the flap indicators.
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By the way your supposition is incorrect about the root stalling first. It is true of wingforms like the Spitfire that the tip stalls very early which is why it has washout. In the case of the P-51 the tips stall first with the rest of the wing quickly following but in cases where the wing is even more rectangular you can get root stalls.
If the tips stalled first the airplane would be very wicked at the stall. Designers always want the root to stall first. There is more than wing planform that effects how the wing stalls. Washout (the twist in the wing putting the tip at a lower angle of incidence than the root) prevents/delays wingtip stall.
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According to the manual:
A stall in the P-51 is comparatively mild. The airplane does not whip at the stall but rolls rather slowly and has very little tendency to drop into a spin. When a complete stall is reached a wing drops. After that if you continue to pull back on the stick the airplane falls off into a steep spiral.
When you release the stick and rudder the nose drops sharply and the airplane recovers from the stall almost instantly.
Here is what is looks like. (http://www.dalefalk.com/Movies/Mustang/7506324_6taqB#484642764_suoh2-A-LB)
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If the tips stalled first the airplane would be very wicked at the stall. Designers always want the root to stall first. There is more than wing planform that effects how the wing stalls. Washout (the twist in the wing putting the tip at a lower angle of incidence than the root) prevents/delays wingtip stall.
You speak in great generalities and in this case 'wicked' would be correct if the pilot doesnt realize what is happening. All WWII fighters can be wicked if handled poorly. Washout is designed into aircraft to alleviate tip stalls in elliptical wings and in wings that have a tapered leading edge like the Me262.
The reason the P-51 experiences buffeting of the tail during stall is not because of the root stalling first (which doesnt happen anyway) but because the downwash of the wing causes an increase in induced drag. If you were to picture the induced drag of nearly every plane in WWII you could see it as slight turbulent flow above the wing behind about the 60% point on the chord (actual percentage varies by airfoil obviously). In the case of the P-51 you would not be incorrect by picturing that as occuring behind the wing altogether.
This is why when the RAE went looking for a combat aircraft to fight the Luftwaffe above 30k they found all allied aircraft wanting except the P-51. While the luftwaffe was fielding aircraft that could fight at mach 0.75 the P-38 was only capable of fighting up to mach 0.68 and the P-47 at mach 0.71 while the Spitfire itself was too fragile to handle combat at high speeds. But the Mustang saved the day because it could fight at mach 0.78 and because of its design (laminar flow and very low induced drag) it could manoeuvre at high speeds at high altitude very successfully.
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You speak in great generalities and in this case 'wicked' would be correct if the pilot doesnt realize what is happening. All WWII fighters can be wicked if handled poorly. Washout is designed into aircraft to alleviate tip stalls in elliptical wings and in wings that have a tapered leading edge like the Me262.
Even the lowly Cessna 150 has washout built into the wing.
I really doubt your statement about the mustang not stalling root first, do you have anything to back it up? I doubt that any airplane that reached any level of production had a stall that started at the wing tip.
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Airfoil stall progression is from trailing edge forward in all cases. Now if you accept that as true (and it is taught this way universally) than you should be able to reason that a rectangular airfoil planform will stall simultaneously from root to tip except that most designs (and particularly in trainers) have a washout/washin design to cause the stall to move from root to tip. In the case of tapered wings however the stall is from tip to root because as the chord decreases (and it does near the tip) the distance also decreases between center of pressure (CP) and the higher pressure at the trailing edge. Because there is a shorter distance there is an increase in the adverse pressure gradient. In a perfect world the washout of the wing would make up for the difference in distance and the entire trailing edge would stall simultaneously. It seldom happens that way and particularly in combat the pilot will have his vectors crossed up (control input) and one wingtip will always (99.99%) stall first.
Laminar flow designs sacrifice low speed handling for high speed performance and so when a laminar design stalls its all stalled at once as in other designs. Just like tapered wing designs 99.99% of the time it is not the entire wing at once but a tip followed by the rest but it is almost certainly never (as close as never could be) the root.
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Post supporting documentation about the Spitfire being too fragile to fight at high speeds, please. I've never seen anything suggesting that was a concern.
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The quote was from Capt Eric Brown at RAE Farnborough in his conversation with General Doolittle. In whole what he said was that the Spitfire was too fragile to carry enough fuel to escort bomber groups deep into Germany and fight at the same time. If it was stiffened for the extra weight of fuel it would be too heavy to fight and so it must be relegated to interceptor roles.
The question was concerning what was going wrong with escort duties at the time (December 1943) and why it was the P-38s and P-47s were such a disaster in Germany while the P-38 was doing such a 'marvelous job' in the Pacific? Capt Browns answer was: 'Against German fighters at high altitudes you need Mustangs.'
I am sure there is also an official report out there somewhere to the same effect.
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might be a dumb question but why is it better for the stall to start at the root rather than the wingtip?
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So the ailerons still have effect (mostly for beginning pilots).
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So the ailerons still have effect (mostly for beginning pilots).
QFT.
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ok that makes sense :aok
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So the ailerons still have effect (mostly for beginning pilots).
Debatable (the part about for beginning pilots). Actually, the whole argument about stalls beginning at the trailing edge is immaterial to the pilot, what is important to the pilot is maintaining control, adequate stall warning so he can maximize performance without inordinate fear of stall/departure, and an easily recoverable stall. A wing is a three-dimensional surface and designers do design aircraft (even now) so that an inner wing surface will stall before the tip does. That is one of the points to washout (whether generated by twist or differences in the airfoil section) and stall strips (which are specifically designed to trigger localized stall on an inboard section of a wing. It is not something done only for beginning pilots and trainers although trainers are likely to have a more pronounced washout and stall warning. Even now with advanced fly-by-wire control systems and automatic maneuvering flaps/slats in modern fighters washout is still used.
The idea that in a "perfect world" the entire wing would stall at the same time is theoretically correct as the wing's maximum potential lift would be generated because the entire wing is at it's CLmax just prior to stall, however, once you go past critical AoA the entire wing will stall, sometimes abruptly. This is not a good thing in the real world. First, stalling at the wingtips destroys aileron effectiveness and therefore control. Second, there would be little margin for error when operating near critical AoA, and third, the stall would tend to be abrupt. The designers chore is to arrive at a good balance of warning, control and performance. Pilots need to be able to ride the edge of stall for maximum turn performance while maintaining control (while doing some fairly abrupt control movements) and designing a wing so that the inboard sections begin to stall first enhances his ability to do this.
The P51 stall video is nice but is only one condition; a wings level, unaccelerated stall and therefore mostly irrelevant to the discussion of ACM where accelerated stalls are the problem. The film is of a benign slow speed, wings level stall while the problems of abrupt and violent stall/departure occurs during accelerated stalls. You have to carefully note under what circumstances a test or discussion is related to before jumping to conclusions. Many aircraft can have a benign approach configuration stall yet still have an abrupt and violent accelerated stall.
Also, the argument that buffet on the P51's tail is caused by "induced drag" is incorrect. It is related only in that induced drag increases with increasing lift but the source of induced drag isn't separated airflow but wingtip vortices's and the inclination of the lift vector relative to the flightpath. A burble is created when the airflow begins to separate from the wing surface, i.e., at the beginning of a stall which is convenient since separation of airflow is the definition of stall. The fact that induced drag occurs at the same time is irrelevant. It is the burble from the stalled section of wing impacting the tail surfaces which causes the stick to tremble.
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Also: Not sure where the info is about buffeting in the p51, I can defiantly say after many stalls, some approach some accelerated I could not feel any buffet or stick tickle pre stall. The pilot said he could hear a slight growl from the air scoop and that is how he judge the edge, I could never hear it. Approach low power stalls were non dramatic, I.E. nose lowers just about like a Cessna, Accelerated stalls during fighting always produced at least a 90 deg snap before I would recover with slam of rudder and snap stick forward (no idea how coordinated I was) , would then instantly hook back up. These were at a 5 or 6 g speeds.
HiTech
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About how I would describe the P-51 in AH2....
:aok
Strip
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All information I posted on the traits of the P-51 come straight from the 'North American P-51 Mustang Pilots Flight Operating Instructions' Technical Order No. IF-51D-1 and very nearly all other information on stalls straight out of Embry Riddle notes which are in direct conflict with what Mace said about root first stalls.
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The quote was from Capt Eric Brown at RAE Farnborough in his conversation with General Doolittle. In whole what he said was that the Spitfire was too fragile to carry enough fuel to escort bomber groups deep into Germany and fight at the same time. If it was stiffened for the extra weight of fuel it would be too heavy to fight and so it must be relegated to interceptor roles.
The question was concerning what was going wrong with escort duties at the time (December 1943) and why it was the P-38s and P-47s were such a disaster in Germany while the P-38 was doing such a 'marvelous job' in the Pacific? Capt Browns answer was: 'Against German fighters at high altitudes you need Mustangs.'
I am sure there is also an official report out there somewhere to the same effect.
That doesn't support your prior claim that the Spitfire was too fragile to fight at high speeds. The fact that the Spitfire Mk XIV was put into service is pretty solid evidence that the Spitfire was quite capable of fighting at high speeds and high altitudes.
As to the fuel, the US and UK both modified a Spitfire to carry more fuel, but the shocks were fully compressed on the ground and dogfighting in it would have been banned until the rear tank was mostly drained, just like the P-51D. In the actual event, long range Spitfires were never needed thanks to the existence of the Mustang so neither project was developed further.
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Sorry Karnak no I was talking about flying escorts to high altitudes against German fighters and did not make myself clear. I would have thought the revelation of where the conversation came from would have made things clear for you though.
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Right, it was your original comment about the Spitfire that confused me. Your post stating where you got it had a different claim, about the Spitfire being too fragile to carry enough fuel rather than having problems with combat at high speed or altitude.
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Oh well anyone that knows the spit at all knows its fast enough and I think it even has a higher combat mach than the P-51 even though RAE didnt mention it in the Doolittle report (probably because they were discussing primarily American fighters). Either way... was the Spitfire up to long range escort in 1943? Was it fighting above 30k?
RAE also states that the 109K4 had the WEP purposely removed because of engine durability issues. If thats true than perhaps the K4 needs a re-looking after?
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All information I posted on the traits of the P-51 come straight from the 'North American P-51 Mustang Pilots Flight Operating Instructions' Technical Order No. IF-51D-1 and very nearly all other information on stalls straight out of Embry Riddle notes which are in direct conflict with what Mace said about root first stalls.
The pilot's manual would be pretty interesting reading! If you would can you check the conditions that it uses with regards to stall? I suspect that it's either in the PA (powered approach) condition with landing flaps and gear extended or a wings level deceleration vice a high-G accelerated stall. Typically flight manuals cover basic stuff like how to start the engine and operational flight characteristics during takeoff and landing separately from tactical characteristics. Even if you do find it, manuals can be wrong (and are wrong more often than pilots would like to know). For instance, it was claimed early on that the F14 was "stall proof" and the A4 NATOPS claimed it had a 720 deg/sec roll rate.....ahhhh.....both WRONG! Now days maneuvering performance is usually covered in a separate TACMAN but they may not have even bothered with this back in WWII and assumed it would be covered in squadron-level training. As a side note, I'm also quite jealous that HiTech had the opportunity to get stick time in a Mustang. I was supposed to fly a Hawker Sea Fury at TPS way back in '87 but came down with the flu the day before :-(
I googled the article you mention (the one by Dave Esser?) and think that you may have misread a couple of parts and the confusion is the argument that stall doesn't begin at the root but at the trailing edge. This is only partially correct. First off, the description of stall progressing from the trailing edge forward is absolutely correct but Esser is really talking about local stall, i.e., stall along a particular cord line. The wing is three dimensional and can (and is) designed with the overall progression of stall not just from the trailing edge forward but across the span, what Esser is calling the stall progression pattern. This pattern is what the WWII aircraft designer is controlling by wash-out, stall strips, leading edge slats, etc., and he must do this so as to maximize wing performance without losing stall warning and creating violent stall/departures. The success of the overall design is what is most important to pilots.
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Mace,
Here's the page I have from the "Pilot's Flight Operating Instructions for the the Army Model P-51-D-5" dated April 5, 1944 (AN 01-60JE-1)
Click on the image to make sure it's as large as possible.
(http://332nd.org/dogs/baumer/BBS%20Stuff/P51pg24.jpg)