Aces High Bulletin Board
General Forums => Aircraft and Vehicles => Topic started by: Anaxogoras on March 30, 2009, 03:01:53 PM
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A few years ago, the Society of Experimental Test Pilots ran a flight test
comparison of the F6F-5, FG-1D (Goodyear F4U), P-47D-40 and P-51D. Chief
test pilot was John Ellis of Kal-Aero. Other pilots also participated.
The three radial jobs had versions of the R-2800 that produced appx. 2,000
hp, so differences in performance can be reasonably attributed to the
airframe (and prop). The P-51 had a V-1650-9 Merlin rated at appx. 1,500
hp.
The P-47 had a Curtiss Electric constant-speed four-blade prop.
The FG-1 and F6F both had Hamilton Standard three-bladed constant speed
props (so only the airframe made the difference between these two).
The P-51 had a Hamilton Standard Hydromatic four-bladed constant speed
prop.
Because of the age of the aircraft, structural loads were kept to 6g max.
Engines were fueled with 100LL, which limited MP by four inches on the
radials. Power was limited to maximum continuous settings (except for
take-off & climb to 10,000 ft., when military power was used),
superchargers were limited to low range. Altitude did not exceed 10,000
ft (so bomber escort altitudes were not reached).
Some of the findings:
CLIMB brake release to 10,000 ft.
Hellcat quickest at 4min 15 seconds, followed by the FG-1 at 4min 44 sec.
However, the F6F required 100 lbs of continuous right rudder making it
very tiring to operate. The P-47 trailed the FG-1 by a few seconds. The
P-51 came in last.
LEVEL ACCELERATION at 10,000 ft. using METO to max attainable speed
P-51 accelerated from 110 KIAS to 242 KIAS in 133 seconds.
P-47 accelerated from 105 KIAS to 223 KIAS in 130 seconds.
F6F accelerated from 100 KIAS to 220 KIAS in 115 seconds.
FG-1 accelerated from 100 KIAS to 230 KIAS in 162 seconds.
STALL normal (straight and level decelerating at 1 kt/sec.) and
accelerated (constant 3g turn decelerating at 1 kt/sec.)
Aerodynamic warning:
Best--P-47, with buffet 5 kt above stall.
Worst--P-51, no buffet or other warning.
FG-1 and F6F buffeted 2 kts above stall.
Decreasing aileron effectiveness and increasing longitudinal stick forces
were noticeable in all except the FG-1.
Height loss, accelerated stall:
Best--P-47, 100 ft.
Worst--P-51, 500 ft.
FG-1 and F6F both 150 ft.
Behavior during accelrated stall:
Most predictable and controllable: P-47 and F6F. Both could be flown at
will into the pre-stall buffet, which at no time was heavy enough to
present problems with tracking, and held at maximum usable lift
coefficient with ease. Sideslip became noticeable as wing heaviness
correctible with rudder. There was little tendency to depart controlled
flight.
The FG-1 suffered severe airframe buffet shortly before the stall, but at
the stall there was a strong g-break and rapid right wing drop--no matter
which direction the turn. Careful left rudder could prevent wing drop,
but then at the stall the aircraft became very unpredictable, bucking and
porpoising, with a tendency to a sudden departure.
The P-51 gave no warning whatsoever of an accelerated stall. At the
stall, the aircraft departed with complete loss of control, achieving
270-degree of roll before recovery. Departure was accompanied by violent
aileron snatch strong enough to rip the control stick from the hand.
In short, the P-51 suffered from a Part I deficiency.
SUSTAINED TURN PERFORMANCE at METO at 10,000 ft.
The F6F out-turned the other three by a conclusive margin (1g). The other
three were all about the same.
Corner speeds of all were very close to the maximum level flight speed,
implying very rapid energy loss when turning at the structural limit.
The F6F was in light airframe buffet at 6g at Vmax; the P-47 experienced
light buffet at 4.8g. The FG-1 and P-51 were buffet-free up to 6g.
MANEUVERING STABILITY stick forces/g at Vmax
FG-1--5 lbs/g (too light)
P-47--7.5 lbs/g (ideal)
F6F--12.5 lbs/g (barely acceptable)
P-51--over 20 lbs/g (excessive)
STATIC LATERAL DIRECTION STABILITY steady heading sideslips
All aircraft except the P-47 exhibited moderate or greater adverse aileron
yaw. Worst was the F6F, followed by the FG-1 and the P-51.
ROLL PERFORMANCE
1g 360-degree right (left slower--F6F worst, P-51 best)
FG-1--81 deg./sec.
F6F--78 deg./sec.
P-51--75 deg./sec.
P-47--74 deg./sec.
3g 180 degree right (left slower--P-51 and F6F best, FG-1 worst)
P-47--66 deg./sec.
FG-1--58 deg./sec.
P-51--55 deg./sec.
F6F--48 deg./sec.
DIVING ACCELERATION 30 deg. dive from 10,000 ft., 5,000 ft. begin pull-up,
level off at 4,000 ft.
Aircraft P-51 P-47 FG-1 F6F
Start Speed 110 kts 100 kts 100 kts 120 kts
Max Speed 350 kts 348 kts 315 kts 350 kts
Time 23 secs 32 secs 28 secs 25 secs
All aircraft except the P-47 needed retrimming during the dive.
AGILITY
g capture of 3g target, held for 5 seconds.
G capture and hold was easiest in the P-47, predictable and accurate. F6F
overshot the target by 0.2g. P-51 and FG-1 both overshot by 0.5g
Heading Change Time (180 deg at METO, 220 KIAS at 10,000 ft.)
FG-1--8.5 sec P-47--9.7 sec F6F--9.9 sec P-51--10.0 sec
AIR-TO-AIR TRACKING 210 KIAS at 10,000 ft. (straight & level into a 3g
turn to the left building to 4g followed by a hard reversal into a 4g
right turn.)
FG-1 best, followed by P-47, F6F and, trailing badly, the P-51. Lateral
corrections in the P-51 were difficult thanks to the very high stick
forces. During one run-thru, an effort at a longitudinal tracking
correction that put 4.5g on the plane led to a sudden departure and spin.
Poor forward visibility in all aircraft (P-47 wost, FG-1 best) made
air-to-air tracking difficult. Depressed sight-line aiming difficult to
impossible.
AIR-TO-GROUND TRACKING (90-degree roll into a 30-degree dive from 200 KIAS
at 5,000 ft. into a 3.5g right rolling pullout to a 90-degree heading
change initiated at 2,500 ft.)
The P-47 was far and away the best, accelerating 125 kts in the dive, no
retrimming required, with crisp control response. Accurate target
tracking very easy. FG-1 next best. 100 kt. acceleration. Agressive
lateral corrections required. P-51 similar to FG-1 in acceleration and
control response, but with heavier stick forces. F6F also accelerated 100
kts., but stick forces increased 20 lbs and rudder forces became so high
they interfered with accurate target tracking.
THROTTLE & PROPELLER RESPONSE
MP response instantaneous. Hamilton Standard propeller response quick and
positive. Curtiss electric prop (on P-47) sluggish in response, delaying
RPM change by 3 seconds in a change from 2,000 rpm (cruise) and 2,550 rpm
(METO).
Radial engines required pilot to manage cowl and cooler flap settings.
Merlin engine had automatic control of oil and coolant radiator flaps.
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Where'd you find this? Pretty good read...
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Now, someone interpret it for me.
Interesting (I think)
wrongway
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I believe one of our friends here has a copy of the actual report http://bbs.hitechcreations.com/smf/index.php/topic,26001.msg268287.html#msg268287
That's a repost of a repost of a repost, lol. That text, or effectively the same was posted quite awhile ago somewhere on a forum or newsgroup, but I bet Gav snagged it from a recent repost over at ubi.
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The only things I find surprising:
The P-51's climb as compared to the Jug and Hog. However, apparently there were power limitations (1500 vs. 1795) and it was kind of an odd test to boot...release of brake and time to 10K as compared to finding ROC for a given alt.
The P-51 sustained turn being "about the same" as the Hog's. I'm going to assume the Hog was not using its maneuvering flaps setting.
Well, another interesting thing: Laminar flow airfoils are known for stalling all at once, so the P-51 stall does not surprise me. However, I've had people who have actual P-51 stick time tell me the onset of the stall is quite apparent. Curious.
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However, I've had people who have actual P-51 stick time tell me the onset of the stall is quite apparent. Curious.
Ahh, you have to love the wonderfully subjective world of test flight reports... :)
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Yup, murdr, repost of a repost. Just thought I'd share because I knew someone would enjoy it. ;)
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The 2000hp and 1500 hp ratings were max ratings. That means WEP.
However WEP was never used. Max continuous was used except for climb, where military was used. So basically the tests are done on cruise settings. Not exactly competitive stats at those reduced settings. Wartime testing pushed the planes more because thousands were available. Newer tests don't dare risk the multi-million-dollar assets that are almost irreplacable in this day and age.
Interesting, but not as valuable as WW2 era tests.
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The V-1650-7 in the P-51D was rated for 1,720 horsepower at WEP.
IIRC, R-2800-59 was used in the P-47D-40. It was rated at 2,500 horsepower at WEP.
The 2000hp and 1500 hp ratings were max ratings. That means WEP.
However WEP was never used. Max continuous was used except for climb, where military was used. So basically the tests are done on cruise settings. Not exactly competitive stats at those reduced settings. Wartime testing pushed the planes more because thousands were available. Newer tests don't dare risk the multi-million-dollar assets that are almost irreplacable in this day and age.
Interesting, but not as valuable as WW2 era tests.
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That makes a bit more sense, but still not exactly up to WW2 testing levels.
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Newer tests don't dare risk the multi-million-dollar assets that are almost irreplacable in this day and age.
Don't be naive. Anytime you start testing stalls in these WW2 aircraft below 10k you risk the airframe. That's a fact.
The Corsair is one of the worst for departure into a spin which can be all but unrecoverable.
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A government military with tens of thousands of suplus planes and thousands of surplus pilots is more likely to risk it in the name of science than a private individual with a single plane and a single pilot.
I'd personally like to see an AH flight model that refelects the unstable aspects of the f4u (and p51 and other planes) stalls/spins, but I don't know if that'll happen any time soon.
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A government military with tens of thousands of suplus planes and thousands of surplus pilots is more likely to risk it in the name of science than a private individual with a single plane and a single pilot.
Indeed, they DO tend to use limited power settings with the old engines. Huge expense to maintain and repair. The dearth of high-octane avgas has something to do with it as well.
I'd personally like to see an AH flight model that refelects the unstable aspects of the f4u (and p51 and other planes) stalls/spins, but I don't know if that'll happen any time soon.
Well, according to the report, if you pull an accelerated stall in the P-51D, you get a snap-roll.
In Il2, if you honk back the stick in the P-51, you get a snap-roll.
In AHII, if you honk back the stick in the P-51, you get a snap-roll.
So things seem okay to me. It does seem pretty darn hard to get a rotation/flat spin in AHII. But the departure traits in AHII are bad enough to make stalling a no-no, so you can still rope people and etc., just fine.
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snap stalls aren't the only issue.
Used to be a definite stability boost in the 51B over the 51D in tight turns, the D would spin inward much more easily. Then since AH2 that's gone. No benefit to having a razorback anymore (a hole/flaw in the game IMO).
Several planes have these issues I'd like to see remedied, and it's not simply snap-stalling.
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No benefit to having a razorback anymore...
The difference in directional stability of the P-51B and D is extremely noticeable--I can discern a huge difference. Try flying with combat trim off and note how differently they behave.
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Well, another interesting thing: Laminar flow airfoils are known for stalling all at once, so the P-51 stall does not surprise me. However, I've had people who have actual P-51 stick time tell me the onset of the stall is quite apparent. Curious.
Ditto. I had a professor back in college who was a pony driver during the war. He said the P-51's stall could be downright treacherous with little to no warning at all. I recall him describing the CL- alpha curve as a straight line with a slight wobble at the top followed by a vertical nose dive.
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From other comments I've read, the P-51 was intended to have laminar flow, but didn't really come close to it. It was a good wing, just not laminar flow. Might explain why the supposed laminar flow didn't stall like a laminar flow should (because it wasn't).
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The difference in directional stability of the P-51B and D is extremely noticeable--I can discern a huge difference. Try flying with combat trim off and note how differently they behave.
I do, and I notice no difference. You can yank and bank pretty easily. Back before AH2 came out even with CT on you spun out in a 51D a lot easier. Pull too hard and you spin into your inner wing. No longer happens. Might dip a wing here or there, sure it snap stalls, but the model is incomplete, it seems.
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I recall him describing the CL- alpha curve as a straight line with a slight wobble at the top followed by a vertical nose dive.
That's pretty typical for a NACA 6-series airfoil. If you've ever flown a plane with an airfoil like this, one minute you're flying, the next minute, you're not. Basically the way NACA computed the coordinates, they unintentionally decambered the leading edge of the airfoil shapes, meaning a very sharp loss of lift at the stall. Several of the laminar airfoils developed since have solved this.
There's still a warning, its just very, very quick--and not the same type of burble warning you get with a turbulent airfoil. If you're riding the edge of the stall, you can feel it, but the transition is so abrupt that if you ham-fist the stall like you would on a plane with a turbulent airfoil, you go abruptly from flight to stalled.
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From other comments I've read, the P-51 was intended to have laminar flow, but didn't really come close to it. It was a good wing, just not laminar flow. Might explain why the supposed laminar flow didn't stall like a laminar flow should (because it wasn't).
I'm inclined to think the simplest solution to the discrepancy is variation in the ability of pilots to detect the subtle warning of the stall.
And from what I understand, every plane is harder to stall/spin since AHII came out.
(I notice you are not very vocal in demanding more vicious 190 departure behavior or that HTC change the modeling so that asymmetrical slat deployment becomes possible in the 109s there Krusty) :devil
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I do, and I notice no difference. You can yank and bank pretty easily. Back before AH2 came out even with CT on you spun out in a 51D a lot easier.
Directional stability is a matter of yaw stability. The D-Pony's nose wanders all over the place in game, whereas the B-Pony is conspicuously more stable. I'm not talking about its tendency to spin when stalled.
but the model is incomplete, it seems.
Or fixed.
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Just curious - during the tests were the planes loaded to their typical WWII operational weights? (Guns, ammo, armor, self-sealing tanks, old heavy radios - would add weight.)
Regards.
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Don't be naive. Anytime you start testing stalls in these WW2 aircraft below 10k you risk the airframe. That's a fact.
Oh BS! Geez, I've done stalls in a Mustang as a 500 hour Cessna pilot. We were never higher than 7500', plenty of warning, no drama.
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D or H model?
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The P47 really comes out as a pleasant ride in this test.
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I'm assuming pilots that flew the P-51 a lot knew right about where it was going to stall based on feel, and therefor felt that it had plenty of warning (as apposed to this tester who probably didn't fly it every day like the WWII pilots did). When you use a machine often enough, being "one with the machine" quite literally does happen. You can even notice it while driving a car, you can tell without any obvious audio or visual warning that a car's tires are at their limits when in turn, stopping, accelerating, etc.
I actually believe that is why the P-51 is so hard to get kills in as a new player, it really is just one of those planes you have to get to know before you become effective in it.
I really would like to know what the load-out of these aircraft were at the time of the test because the P-47's results really doesn't seem to fit how it flies in-game.
Asymmetrical slat deployment would be an nice addition to the game, would be interesting to see how it changes the characteristics of the aircraft that have them and if it gives any insight to how the aircraft really reacted in real life.
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Asymmetrical slat deployment would be an nice addition to the game, would be interesting to see how it changes the characteristics of the aircraft that have them and if it gives any insight to how the aircraft really reacted in real life.
I guess you don't fly aircraft with leading edge slats.
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Asymmetrical slat deployment would be an nice addition to the game, would be interesting to see how it changes the characteristics of the aircraft that have them and if it gives any insight to how the aircraft really reacted in real life.
We have that now. The slats on each wing operate independent of one another however due to the nature of their design they'll operate nearly simultaneously when the required angle of attack for them to deploy is reached on each wing.
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We have that now. The slats on each wing operate independent of one another however due to the nature of their design they'll operate nearly simultaneously when the required angle of attack for them to deploy is reached on each wing.
I have been unable to cause an asymmetrical deployment, and I've tried hard. Got film of one occuring?
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BnZs, how often do you fly the 109?
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BnZs, how often do you fly the 109?
Not too often, but I have tried to cause asymmetrical deployment with that and other slat planes and have never been able to do it, no matter how much I stomp the rudder and off-center the ball, etc. If anyone knows how to make an AHII plane deploy slats asymmetrically, I would like to see the film and know how.
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Not too often, but I have tried to cause asymmetrical deployment with that and other slat planes and have never been able to do it, no matter how much I stomp the rudder and off-center the ball, etc. If anyone knows how to make an AHII plane deploy slats asymmetrically, I would like to see the film and know how.
It doesn't show in the film viewer. I'd like you to teach me how not to deploy the slats asymmetrically. Just fly the 109 or La-5/7 around for a while and you will hear the slats come out one after the other.
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You can't really make it happen, it just happens... usually at very inopportune times.
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It doesn't show in the film viewer. I'd like you to teach me how not to deploy the slats asymmetrically. Just fly the 109 or La-5/7 around for a while and you will hear the slats come out one after the other.
I have flown both airplanes some, and I just fooled around with the 109 F-4 for about 15 minutes trying to make the slats deploy asymmetrically. I tried it with combat trim off, combat trim on, with the ball centered and every variation of rudder/aileron input skewing the ball. I did not see the slats deploying asymmetrically once, did not get any auditory indication of this happening, and did not experience any un-commanded rolling that would indicate asymmetrical flap deployment. I tried pulling smoothly and deploying the slats, and pulling harsly into the stall. Is it possible you are mistaking the wing drop in an accelerated stall for uneven slat deployment? But I didn't find the stall unusual either. So I must say this is abit curious.
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Oh BS! Geez, I've done stalls in a Mustang as a 500 hour Cessna pilot. We were never higher than 7500', plenty of warning, no drama.
Are you talking about power-off stalls, or deliberate accelerated stalls? I'm certain that no P-51 owner will let a back seater fly very far into a stall before he tells them to release back pressure on the stick.
I've never heard anything good about the P-51's stall behavior, especially when the pilot lets the stall fully develop. Power-on spins were prohibited as they were and still are considered very high risk. Recovery could take as much as 10,000 feet. More than a few pilots have managed to kill themselves spinning P-51s.
My regards,
Widewing
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Try the 109k, it is the most squirly 109.
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Try the 109k, it is the most squirly 109.
Just tried it, same variations in the testing, and could get no visual evidence or evidence of flight effects from asymmetrical deployment no matter how hard I tried. The airplane tends to drop a wing to whichever side when you whip into an accelerated stall in uncoordinated flight (except when you have the engine at WEP, then the airplane *really* does not want to roll right under any circumstances), but there is nothing even resembling the sort of un-commanded roll effect I would expect from uneven slat deployment when not stalled.
A time or two when I was visually inspecting the aircraft in external views the sound effect *sounded* like one was slamming closed after the other, but as the visual picture and flight effects did not agree with this conclusion, I assume its a sound thing and not related to flight modeling.
I also note that the slats are not found on the damage list for the 109 (Or any other aircraft IIRC) and thus presumably cannot be shot away or jammed.
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A time or two when I was visually inspecting the aircraft in external views the sound effect *sounded* like one was slamming closed after the other, but as the visual picture and flight effects did not agree with this conclusion, I assume its a sound thing and not related to flight modeling.
I can feel the effects of asymmetrical slat deployment, and I'm surprised that you claim you don't. It is in the flight model.
Why would you expect it to cause "un-commanded roll?" What does happen is a wingtip-snatch, and you have to let the plane right itself.
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Why would you expect it to cause "un-commanded roll?" What does happen is a wingtip-snatch, and you have to let the plane right itself.
I would expect some unusual, harsh roll-yaw-something-if a lift increasing device was deployed on one wing and not the other. I did not experience any unusual roll or yaw effects when trying to deploy them asymmetrically. The only difference I even *think*I might detect between the slatted planes and non slatted planes is abit more bouncy in pitch when handled less than smoothly. A sudden too-hard pull into an accelerated stall, such as one might accidentally do in a dogfight, even flying as un-coordinated as possible deliberately, fails to produce any effects which are unusual for a high-torque single-engine airplane.
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I would expect some unusual, harsh roll-yaw-something-if a lift increasing device was deployed on one wing and not the other.
Slots and slats don't add lift, not much anyway. They allow high angle of attack without stalling.
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Oh BS! Geez, I've done stalls in a Mustang as a 500 hour Cessna pilot. We were never higher than 7500', plenty of warning, no drama.
Voss?
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Slots and slats don't add lift, not much anyway. They allow high angle of attack without stalling.
Correct, but, but I was riding the edge and jerking it into the buffet, and still no sign of anything to indicate one slat open and one slat closed. The 109 seems fairly stable in turns right up until you pull it into the stall. The only thing it seems to do is the nose "bounces" down fairly abruptly if you suddenly let go the back pressure and the slats close. So I've got to say slat asymmetry seems to be a non-issue for the AHII. Kind of like how the AHII pilot gets a great loud buffet and shaking to warn him of stall, even in the P-51.
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Why do you think one slat would remain open while the other would remain closed? It sounds like you're saying this is what should happen, but I've never read anything about the 109 that indicated such a problem. Instead, what could be troublesome is that one would open or close a half second before the other: this happens frequently in Aces High.
Really, this time I think you're coming at it with an a priori idea of how things should work, and then criticizing the flight model when it doesn't mach your expectation.
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Why do you think one slat would remain open while the other would remain closed? I've never read anything about the 109 to indicate that this happened. Instead, what could be troublesome is that one would open or close a half second before the other: this happens frequently in Aces High.
Really, this time I think you're coming at it with an a priori idea of how things should work, and then criticizing the flight model when it doesn't mach your expectation.
I'm not campaigning to have the modeling changed on this particular point, I was more pointing out (in response to Krusty :devil) that there are ALOT of nasty flight quirks that could be added to AHII besides the P-51s treacherous stall, IF we got HTC to go on a "make the airplanes more difficult to fly."
If the deployment is asymmetrical, the period of asymmetry is so brief I can't pick it up visually looking at the plane in F3 view nor can I detect any deleterious flight effects. The 109 seems to remain a fairly stable platform right up until you actually stall it. None of the sort of thing you run into with the Ta-152 for example.
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I'm not campaigning to have the modeling changed on this particular point, I was more pointing out (in response to Krusty :devil) that there are ALOT of nasty flight quirks that could be added to AHII besides the P-51s treacherous stall, IF we got HTC to go on a "make the airplanes more difficult to fly."
If the deployment is asymmetrical, the period of asymmetry is so brief I can't pick it up visually looking at the plane in F3 view nor can I detect any deleterious flight effects. The 109 seems to remain a fairly stable platform right up until you actually stall it. None of the sort of thing you run into with the Ta-152 for example.
Ah, yes, I do agree that the nastier traits of these aircraft are sanitized for us. In many cases, I've read that merely taking off required full-rudder told hold straight down the runway, whereas in AH you only need moderate rudder input to hold even the most tricky fighters straight.
edit:
I figured out how to get one slat to open and the other remain closed. 109k, 50% fuel, at about 200mph do a lazy barrel roll with a bit of back pressure on the stick and rudder in the direction of the roll. Do it right, and the outside wing slat will open while the inside wing slat remains closed. Still, this doesn't happen much during combat.
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Are you talking about power-off stalls, or deliberate accelerated stalls? I'm certain that no P-51 owner will let a back seater fly very far into a stall before he tells them to release back pressure on the stick.
I've never heard anything good about the P-51's stall behavior, especially when the pilot lets the stall fully develop. Power-on spins were prohibited as they were and still are considered very high risk. Recovery could take as much as 10,000 feet. More than a few pilots have managed to kill themselves spinning P-51s.
Normal, straight ahead stall, low cruise power setting. There is no doubt that the Mustang is nasty post-stall (Hoover said he wouldn't do any snaproll/stall stuff because of the Mustangs post stall behavior), my reply was to the statement that "Anytime you start testing stalls in these WW2 aircraft below 10k you risk the airframe. That's a fact. " Now if he was meaning actual flight test of stall behavior perhaps, but stalls aren't a huge deal when done properly. That being said there is certainly nothing wrong with getting some extra altitude, altitude = insurance. The problem comes up if you pooch the stall recovery and allow a spin to develop. Any airplane, even the lowly Cessna 150, will bite if you don't fly it properly.
I'd have no problem doing stalls in a Mustang but I would never intentionally stall a B-24...it's stall makes the Mustang look like a trainer. <G>
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Tried that awhile and FINALLY got enough gap in the deployment times to see it happening. Still didn't skew the plane to any noticeable extent when it did happen. Considering how hard it was even get the effect, I don't think asymmetrical deployment constitutes much of a handling problem for the 109 in AH. :salute
I figured out how to get one slat to open and the other remain closed. 109k, 50% fuel, at about 200mph do a lazy barrel roll with a bit of back pressure on the stick and rudder in the direction of the roll. Do it right, and the outside wing slat will open while the inside wing slat remains closed. Still, this doesn't happen much during combat.
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I've run into it numerous times in the eXtreme Racing League. The worst that sticks in my mind was the Me-262 in various turns at very low altitudes. It is exciting to be in a steep bank coming around a turn marker only to have one slat deploy wanting to throw you over on your back when you're not expecting it. We spend a lot of time riding the edge of slat deployment and trying to hang on to every last bit of energy on race nights which gets us familiar with the edges of the flight envelopes of many of the airplanes.
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Oh BS! Geez, I've done stalls in a Mustang as a 500 hour Cessna pilot. We were never higher than 7500', plenty of warning, no drama.
You have no idea what you are talking about if you don't believe testing on the edge of any flight envelope does not cause inherent risk to the airframe and pilot.
BTW, sitting in the back seat while the aircraft is doing stalls hardly qualifies you as having "done stalls in a Mustang." Further, power on and off stalls are a part of training for all Warbird pilots as they teach the recognition of the buffet (if any) and subsequent recovery to prevent departure.
Last thing, being proud that you are doing stalls in a Mustang "never above 7500' " does not endear you to anyone here, it just shows recklessness and lack of understanding of the departure characteristics of the Mustang and the true danger risked being that low trying to get out of a spin.
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From Air and Space magazine, http://www.airspacemag.com/flight-today/mustang.html (http://www.airspacemag.com/flight-today/mustang.html):
One of the grave dangers posed by the Mustang is its behavior during an accelerated stall--a loss of lift caused by disturbed airflow over the wing in a high-G maneuver like a tight turn. The Mustang can react violently, snapping into a roll and sometimes flipping over on its back. "It virtually gives you no warning," says Saether.
wrongway
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BTW, sitting in the back seat while the aircraft is doing stalls hardly qualifies you as having "done stalls in a Mustang." Further, power on and off stalls are a part of training for all Warbird pilots as they teach the recognition of the buffet (if any) and subsequent recovery to prevent departure.
Last thing, being proud that you are doing stalls in a Mustang "never above 7500' " does not endear you to anyone here, it just shows recklessness and lack of understanding of the departure characteristics of the Mustang and the true danger risked being that low trying to get out of a spin.
And I stated that doing flight test stall stuff is risky. The post I replied to just made a blanket statement that doing stalls below 10K was risking the airframe...that's a BS statement.
I wasn't "sitting in the back seat", I was flying the Mustang. I was doing as instructed by Lee Lauderbach..he happens to be the highest time Mustang pilot in the world and is considered by the Warbird community as one of the best so tell him how reckless it was...I can assure you he knows a heck of a lot more about it than you do. <G>
How much high performance aircraft time do you have? What do you base your opinion on?
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And I stated that doing flight test stall stuff is risky. The post I replied to just made a blanket statement that doing stalls below 10K was risking the airframe...that's a BS statement.
I wasn't "sitting in the back seat", I was flying the Mustang. I was doing as instructed by Lee Lauderbach..he happens to be the highest time Mustang pilot in the world and is considered by the Warbird community as one of the best so tell him how reckless it was...I can assure you he knows a heck of a lot more about it than you do. <G>
How much high performance aircraft time do you have? What do you base your opinion on?
Of course, stalls and accelerated stalled are completely different.
I practiced stalls in a Grumman C-1A back in the 70s. Nose up a bit, pull off power until the stall shaker begins to raise hell. Then, ease the yoke forward and gently feed in some throttle. The C-1A had an airflow sensor on the upper side of the left wing's leading edge. Stall onset was sudden and there was almost no buffet to warn the pilot. Thus, the stall shaker was employed on the yoke itself. Recovery wasn't difficult and altitude loss wasn't great. Nonetheless, since the parent aircraft (S2F) performed its mission at low level, a fully developed stall could find one running out of altitude before recovery was completed. Thus, the stall shaker carried over to the C-1A. These aircraft were also equipped with a G Limiting valve that gradually added resistance to the yoke as G increased.
By the way, Bodhi restores Warbirds for a living.
My regards,
Widewing
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Tried that awhile and FINALLY got enough gap in the deployment times to see it happening. Still didn't skew the plane to any noticeable extent when it did happen. Considering how hard it was even get the effect, I don't think asymmetrical deployment constitutes much of a handling problem for the 109 in AH. :salute
The 109E suffered from aileron snatching during asymmetrical slat deployment. The airflow over the wing was momentarily disrupted, resulting in reduced pressure on the top of the aileron pulling it swiftly upward. The aileron snatch problem was fixed with the F version. Asymmetrical, or even symmetrical slat deployment in the F/G/K series 109 would still make a loud bang and might throw the pilot off his aim at a critical moment, but nothing more.
A lot of severe quirks and handling problems are not modelled in AH; Spitfire aileron reversals (due to wing flexing) at high speed for example. Such extreme and very individual effects are perhaps beyond the scope of a game like AH.
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The 109E suffered from aileron snatching during asymmetrical slat deployment. The airflow over the wing was momentarily disrupted, resulting in reduced pressure on the top of the aileron pulling it swiftly upward. The aileron snatch problem was fixed with the F version. Asymmetrical, or even symmetrical slat deployment in the F/G/K series 109 would still make a loud bang and might throw the pilot off his aim at a critical moment, but nothing more.
A lot of severe quirks and handling problems are not modelled in AH; Spitfire aileron reversals (due to wing flexing) at high speed for example. Such extreme and very individual effects are perhaps beyond the scope of a game like AH.
I'd love to see aileron reversal in the game just to hear all the WTF's :huh on VOX :D. I believe the Jug had an aileron reversal problem as well. Maybe Widewing can set me straight.
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We also have perfectly still air in the game. No fluctuations whatsoever.
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The 109E suffered from aileron snatching during asymmetrical slat deployment. The airflow over the wing was momentarily disrupted, resulting in reduced pressure on the top of the aileron pulling it swiftly upward. The aileron snatch problem was fixed with the F version. Asymmetrical, or even symmetrical slat deployment in the F/G/K series 109 would still make a loud bang and might throw the pilot off his aim at a critical moment, but nothing more.
A lot of severe quirks and handling problems are not modelled in AH; Spitfire aileron reversals (due to wing flexing) at high speed for example. Such extreme and very individual effects are perhaps beyond the scope of a game like AH.
Yeah, CFSIII is the only sim I've ever seen that modeled the Spitfire reversal effect :D. I don't feel any particular need for these effects to be modeled...the whole issue came up kind of in response to Krusty's idea that one of the most mediocre planes in the game also needs to be singular in having all of its warts accurately modeled. :D
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That's not how I see it. The P-51 had a lot of vices that are not modelled, not only bad departure characteristics. The P-51's heavy elevator forces at high speeds are particularly under modelled. In my opinion the P-51 and Fw 190 should have bad stall characteristics and the P-51 and 109 should have bad elevator response at high speed. A little known nugget of information is that the 109's were actually known to be able to pull out of dives earlier than Mustangs. If the fuselage tank is full on the D-Pony and the pilot stalls it nose-high, the plane should enter a nose-high spin like the Ta 152 does due to CG issues. But that's it; modelling anything worse is going too far for a game like AH.
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That's not how I see it. The P-51 had a lot of vices that are not modelled, not only bad departure characteristics. The P-51's heavy elevator forces at high speeds are particularly under modelled. In my opinion the P-51 and Fw 190 should have bad stall characteristics and the P-51 and 109 should have bad elevator response at high speed. A little known nugget of information is that the 109's were actually known to be able to pull out of dives earlier than Mustangs. If the fuselage tank is full on the D-Pony and the pilot stalls it nose-high, the plane should enter a nose-high spin like the Ta 152 does due to CG issues. But that's it; modelling anything worse is going too far for a game like AH.
Everything, and I mean everything, in this game arguably has under-modeled control forces. Both Zekes are still *somewhat* rolling and turning at 350mph IAS!
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...A little known nugget of information is that the 109's were actually known to be able to pull out of dives earlier than Mustangs...If the fuselage tank is full on the D-Pony and the pilot stalls it nose-high, the plane should enter a nose-high spin like the Ta 152 does due to CG issues.
:noid
I'd like to see references that describe the exact conditions you mention here.
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:noid
I'd like to see references that describe the exact conditions you mention here.
Read the P-51 pilot manual where it says not to use trim to pull out of a dive. The 109 could use its elevator trim to pull out of the dive.
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Haven't heard of the elevator authority issue, but I have heard of P-51s swapping ends trying to maneuver with the aft tank full. I think I read or heard Yeager discussing it in an interview.
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A select few pilots have flown both the P-51 and 109. All of them (that I have read/listened to) say that the two aircraft have similar stick forces; if anything they usually praise the 109 more for its better slow-medium speed control lightness and harmonization. The Merlin powered P-51 had a lot of teething problems, but, for some reason, they are largely overlooked. It had problems with the canopy frosting over, with jamming guns, with the engine cooling system and the engine itself, and with shedding the tail. In fact, the plane had so many problems initially that Col. Don Blakeslee, CO of the 4FG, called it "an experimental aircraft" and expressed doubts that it could be successful.
The P-38 had gone through its teething troubles the previous fall and with the introduction into ETO combat of the J model well-pleased its pilots. FGs getting the P-51 were unhappy and pilots grumbled that they would rather have the Lockheed. It was not uncommon to have almost 30 percent of P-51 sorties aborted for mechanical reasons during the winter and spring of 1944 (typical abort rate for all causes for all USAAF aircraft was 8 percent). When the D model became available in quantity in the summer, cases of the aircraft losing its tail surfaces in flight began to be reported. Flight restrictions were placed on the aircraft and the tail surfaces were beefed up.
Wing failures were also reported due to control stick force reversal in high-speed dives. The bobweight was added to the elevator control system to fix this problem. But for the aircraft to be even marginally stable, the fuselage fuel tank had to be less than half full. The Mustang still had problems a year later when the 7AF began B-29 escort missions to Japan. Incidences were reported of tail surface failures in dogfights. In one instance in April, 1945, a P-51D got into a dogfight with a Mitsubishi Raiden. During the violent manoeuvring, the Mustang first shed its tail control surfaces and then its wings were torn off. The pilot, 2Lt. James Beattie, did not survive. The Raiden apparently suffered no damage from the severe loads placed on it during the dogfight.
Should all of these vices be modelled in AH? No. Should some of them? Yes.
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:noid
I'd like to see references that describe the exact conditions you mention here.
In addition to what others have provided so far I'll give you these quotes:
Robert C.Curtis, American P-51 pilot:
"My flight chased 12 109s south of Vienna. They climbed and we followed, unable to close on them. At 38,000 feet I fired a long burst at one of them from at least a 1000 yards, and saw some strikes. It rolled over and dived and I followed but soon reached compressibility with severe buffeting of the tail and loss of elevator control. I slowed my plane and regained control, but the 109 got away.
On two other occasions ME 109s got away from me because the P 51d could not stay with them in a high-speed dive. At 525-550 mph the plane would start to porpoise uncontrollably and had to be slowed to regain control. The P 51 was redlined at 505 mph, meaning that this speed should not be exceeded. But when chasing 109s or 190s in a dive from 25-26,000 it often was exceeded, if you wanted to keep up with those enemy planes. The P 51b, and c, could stay with those planes in a dive. The P 51d had a thicker wing and a bubble canopy which changed the airflow and brought on compressibility at lower speeds."
Thomas L. Hayes, Jr., American P-51 ace, 357th Fighter Group, 8 1/2 victories:
"Thomas L. Hayes, Jr. recalled diving after a fleeing Me-109G until both aircraft neared the sound barrier and their controls locked. Both pilots took measures to slow down, but to Hayes' astonishment, the Me-109 was the first to pull out of its dive. As he belatedly regained control of his Mustang, Hayes was grateful that the German pilot chose to quit while he was ahead and fly home instead of taking advantage of Hayes' momentary helplessness. Hayes also stated that while he saw several Fw-190s stall and even crash during dogfights, he never saw an Me-109 go out of control."
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Nothing like some good old annecdotes to stoke the flames of an argument eh?
Mr. Curtis, with respect to his service and memory, is wrong about the wing thickness issue.
Surely there are some technical references?
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Surely there are some technical references?
MiloMorai mentioned the P-51's handbook. If you're looking for an official P-51 vs. 109 "suicide dive" test, I don't think you'll find one. I said: "A little known nugget of information is that the 109's were actually known to be able to pull out of dives earlier than Mustangs." And I've now documented that. The technical evidence is that the 109's "flying-tail" elevator trim configuration allowed it to trim out of compressibility dives. The P-51's trim tabs did not, and trying to could destroy the Pony when the elevators regained effect at lower altitudes.
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Robert C.Curtis, American P-51 pilot:
"My flight chased 12 109s south of Vienna. They climbed and we followed, unable to close on them. At 38,000 feet I fired a long burst at one of them from at least a 1000 yards, and saw some strikes. It rolled over and dived and I followed but soon reached compressibility with severe buffeting of the tail and loss of elevator control. I slowed my plane and regained control, but the 109 got away.
On two other occasions ME 109s got away from me because the P 51d could not stay with them in a high-speed dive. At 525-550 mph the plane would start to porpoise uncontrollably and had to be slowed to regain control. The P 51 was redlined at 505 mph, meaning that this speed should not be exceeded. But when chasing 109s or 190s in a dive from 25-26,000 it often was exceeded, if you wanted to keep up with those enemy planes. The P 51b, and c, could stay with those planes in a dive. The P 51d had a thicker wing and a bubble canopy which changed the airflow and brought on compressibility at lower speeds."
The P-51D had a wider wing in the area of the leading edge extension at the root.
NAA/NACA 45-100 was used on models up to the H. If a thicker wing was used on the P-51D then the plan form of the wing would give a much greater wing area. That is the chord and wingspan would have to increase.
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I'm not saying Robert C. Curtis is right with regard to the P-51D's wing thickness, only that I believe him when he says he couldn't catch 109's in fast dives.
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The P-51D had a wider wing in the area of the leading edge extension at the root.
Just for clarity:
IIRC the extension at the leading edge of the wing root you're talking about was not done for aerodynamic reasons, it was done to accomodate the wheels needed to handle the larger diameter brakes needed on the earlier model ponies. Subsequent improvements in brake performance allowed smaller diameter brakes => smaller diameter wheels and tires => no need for LE root extension on P-51H's. :salute
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I'm not saying Robert C. Curtis is right with regard to the P-51D's wing thickness, only that I believe him when he says he couldn't catch 109's in fast dives.
Oh, I know Die Hard but it is one of those myths that won't die. ;)
Yes Cthulhu.
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The technical evidence is that the 109's "flying-tail" elevator trim configuration allowed it to trim out of compressibility dives. The P-51's trim tabs did not...
There's no doubt that the Mustang POH states to not use elevator trim to pull out of dives. Obviously the 109 could do so. What has not been established is any technical reference that supports your statement that a 109 could pull out of dive faster than a P-51 because of excess stick force in the P-51. There's an anecdote from a pilot that on an occasion had a 109 outdive him. My statement regarding Mr. Curtis's statement was not to impune his credibility as a Mustang pilot, but rather to call into question his aerodynamic expertise with respect to the reason why the 109 out dove him.
A trim tab may be a helpful assist to the 109 pilot, but may not even be necessary for the P-51. I'm not a Pony fanboi, just trying to provoke some actual tactile evidence to back up your claims. Especially when you say that a P-51 with a full fuselage tank should suffer a deep stall and spin when stalled. From what evidence do you make that claim? Everyone knows that the full fuselage tank was a destabilizing influence on the plane, but to say it creates conditions from which the Pony departs controlled flight is something else. For example, if the Pony stalls but maintains coordinated flight, it cannot spin--no aircraft can. Aft CG conditions do not make aircraft more prone to spin. They can create instability in the pitch axis and make the aircraft difficult to trim. They can make the aircraft more difficult to recover from spins, but in and of themselves create no spin bias whatsoever.
Stories are helpful for context and I enjoy a good tale as much as any other, but they should always be considered as offered--rememberances and not hard truths necessarily.
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NAA/NACA 45-100 was used on models up to the H. If a thicker wing was used on the P-51D then the plan form of the wing would give a much greater wing area. That is the chord and wingspan would have to increase.
The wing chord was greater at the root as you say, although the profile of the root fillet wasn't a NACA 45-100. It created a negligible increase (1 or 2%?) in wing area. The P-51/A/D all shared the same planform, whereas the B/C didn't have the root fillet. However, with respect to conpressibility, the profile thickness for the wing did not change. Therefore, the wing's compressibility properties would have remained the same. And, I think you got your terminology mixed up about the wingspan increasing.
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Aft CG conditions do not make aircraft more prone to spin. They can create instability in the pitch axis and make the aircraft difficult to trim. They can make the aircraft more difficult to recover from spins, but in and of themselves create no spin bias whatsoever.
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I am not sure this is true. When you move the CG, you change all the moment acting on the plane in all axes - the arms length is different. In the yaw, this would make the stabilizing arms (tail) shorter and others (asymmetrical wing drag, uncoordinated flight on the fusalage, prop etc...) longer or shorter. Remember our old mosquito FM with the aft CG? it would start swinging the tail whenever speeds got slow and the tail became less effective in damping them.
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"If the CG is too far aft, it will be too near the center of lift and the airplane will be unstable, and difficult to recover from a stall. [Figure 1-2] If the unstable airplane should ever enter a spin, the spin could become flat and recovery would be difficult or impossible."
Page 1-3 http://www.faa.gov/library/manuals/aircraft/media/FAA-H-8083-1A.pdf
"By maintaining directional control and not allowing the nose to yaw toward the low wing, before stall recovery is initiated, a spin will be averted. If the nose is allowed to yaw during the stall, the airplane will begin to slip in the direction of the lowered wing, and will enter a spin. An airplane must be stalled in order to enter a spin..."
Page 4-13 http://www.faa.gov/library/manuals/aircraft/airplane_handbook/media/faa-h-8083-3a-3of7.pdf
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"If the CG is too far aft, it will be too near the center of lift and the airplane will be unstable, and difficult to recover from a stall. [Figure 1-2] If the unstable airplane should ever enter a spin, the spin could become flat and recovery would be difficult or impossible."
Page 1-3 http://www.faa.gov/library/manuals/aircraft/media/FAA-H-8083-1A.pdf
"By maintaining directional control and not allowing the nose to yaw toward the low wing, before stall recovery is initiated, a spin will be averted. If the nose is allowed to yaw during the stall, the airplane will begin to slip in the direction of the lowered wing, and will enter a spin. An airplane must be stalled in order to enter a spin..."
Page 4-13 http://www.faa.gov/library/manuals/aircraft/airplane_handbook/media/faa-h-8083-3a-3of7.pdf
Yep :aok , what that guy said.
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What has not been established is any technical reference that supports your statement that a 109 could pull out of dive faster than a P-51 because of excess stick force in the P-51.
No, that has not been established, and I don't see why it needs to be since I've never made that claim. If you go back and read my post again you'll see that I think the 109 and P-51 should both have limited elevator control at high speed, not that the P-51 should be worse. The nugget about 109's pulling out earlier is only due to the flying-tail trim system, not to any superior elevator control on the 109.
The fact remains that the 109 and P-51 both suffered from heavy stick forces at high speed. Pilots of both planes attest to having to use both hands to control their aircraft at high speed. This comes as no surprise with regard to the 109; it is commonly known to have high stick forces, but it may come as a surprise to many that the P-51 suffered from the same ailment. Like I said earlier, for some reason the P-51's many vices seems to have been overlooked in popular postwar publications.
"The P-51 Mustang has always been the machine of dreams for pilots-gorgeous, fast and with a Merlin engine. Certainly anything that looks that good must fly most wonderfully, but pilots who have owned them often say that they fly like a Peterbilt with wings, that it takes both hands on the stick to pull through a loop and the most fun of flying one is taxiing out in front of your friends with the canopy open.
Now comes scientific proof. A 1991 study by John M. Ellis and Christopher A. Wheal published by the Society of Experimental Test Pilots compared four leading U.S. World War II fighters-the P-51D Mustang, P-47D Thunderbolt, F6F-5 Hellcat and FG-1D Corsair-concludes that the P-51 was the best of them, overall, but that it had such a high stick forces that it often required two hands and that it would snap and spin absolutely unpredictably, often so violently that it would jerk the stick from the pilot's hands.
Said the report, "[The P-51] scored high in performance, was well-suited to long-range escort missions and would do well intercepting non-maneuvering targets. However, its extraordinarily high stick forces, totally inadequate stall warning and vicious departures make it quite unsuited to the air combat maneuvering environment. It is a tribute to the adapability of the pilots who flew them that Mustangs scored so many kills against the opposition.""
"Like the P-51B, the P-51D was difficult to handle with a full fuselage tank, and it had high stick forces under combat maneuvers. Worst of all, under such maneuvers it gave no warning of stall and could fly abruptly and wildly out of control. It was also difficult to bail out of, since air pressure tended to trap the pilot in his seat, and Mustang pilots had to learn the Luftwaffe trick of simply turning the aircraft over and falling out. However, the aircraft's virtues were such that these vices were forgiveable, though not forgettable."
"The allison Mustangs were noted for their lack of need for trimming changes, the Merlin Mustangs found more directional trim changes with speed and power changes. It is noted some pilots trimmed their P-51s "almost continuously" to wash out high stick or pedal forces in combat."
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Like I said earlier, for some reason the P-51's many vices seems to have been overlooked in popular postwar publications.
Like there's some sort of conspiracy?
...concludes that the P-51 was the best of them, overall...
Its ironic to me that anyone that reads through what Gavagai posted originally (from the same report I assume) could ever make that conclusion about the P-51. From the results of their testing, especially from their review of its handling characteristics, its seems to me the P-51 is the worst. Can you link the source from this review?
"Like the P-51B, the P-51D was difficult to handle with a full fuselage tank, and it had high stick forces under combat maneuvers. Worst of all, under such maneuvers it gave no warning of stall and could fly abruptly and wildly out of control. It was also difficult to bail out of, since air pressure tended to trap the pilot in his seat, and Mustang pilots had to learn the Luftwaffe trick of simply turning the aircraft over and falling out. However, the aircraft's virtues were such that these vices were forgiveable, though not forgettable."
Can you link this one as well, or is it more of the same article?
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Like there's some sort of conspiracy?
No, just that the P-51's glory as the "plane that won the war" might outshine its many vices, giving people the impression that it was better than it actually was.
Its ironic to me that anyone that reads through what Gavagai posted originally (from the same report I assume) could ever make that conclusion about the P-51. From the results of their testing, especially from their review of its handling characteristics, its seems to me the P-51 is the worst. Can you link the source from this review?
The P-51 was better in performance than the other three aircraft tested, but had some serious handling vices. What's so ironic about that conclusion? We both know that the P-51 (or 109 for that matter) was a successful combat aircraft, so obviously these handling vices were not so severe that the aircraft was not flyable in combat.
http://www.seqair.com/Other/Sawdust/Sawdust1996.html
Can you link this one as well, or is it more of the same article?
http://www.faqs.org/docs/air/avp512.html
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What's so ironic about that conclusion?
[The P-51]...would do well intercepting non-maneuvering targets. However, its extraordinarily high stick forces, totally inadequate stall warning and vicious departures make it quite unsuited to the air combat maneuvering environment...[the report] concludes that the P-51 was the best of them...
The irony is that the "best of them" is a plane that was characterized as "unsuited to the air combat maneuvering environment". Pretty damning description for an aircraft that was a fighter, don't you think?
Also, I found this last paragraph of the first link interesting. It was conspicuous by its absence in your quote from it...
On the other hand, we read portions of this report to Parke Smith, who once flew Spitfires, Hurricanes and P-51s with the RAF. He said the report was the "biggest bunch of crap I've ever heard"... "complete garbage", etc. He agreed that the Mustang was not nearly as delightful and light on the controls as the Spitfire, but he thought it was as easy and maneuverable to fly as a CAP-10, which he flew for years.
The next quote, from your second link is, in my opinion, a great example of poetic license taken by an author either trying to spice up his writing or purposefully exaggerating something due to an agenda:
With a full fuel load, getting the fighter off the runway was downright dangerous, and the aircraft was only marginally controllable for the first hour or so that it took to drain the tank.
Compared to this quote from the P-51 POH:
the weight of this fuel moves the center of gravity back so the airplane is unstable for anything other than straight and level flight... page 67.
My point is that saying things like "downright dangerous" and "marginally controllable" is inflammatory and not objective. Making a statement like "the P-51 fuselage tank was a considerable destabilizing force on the plane, but one that most Mustang pilots learned to control effectively..." would be more responsible on the author's part.
How many U.S. pilots would think that the 109 was extremely difficult to fly because it lacked rudder trim? Probably all of them since they were accustomed to being able to trim away yaw forces on the pedals. German pilots that were accustomed to it probably paid it no mind.
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The objectivity of various authors aside, the issue was the stick forces of the P-51 at high speed. And in that test of those four US fighters the result was:
MANEUVERING STABILITY stick forces/g at Vmax
FG-1--5 lbs/g (too light)
P-47--7.5 lbs/g (ideal)
F6F--12.5 lbs/g (barely acceptable)
P-51--over 20 lbs/g (excessive)
With that test data and numerous anecdotal evidence it is clear the P-51 suffered from high stick forces at high speed, just like the 109, and I think the AH flight model should reflect this. Don't you?
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The objectivity of various authors aside, the issue was the stick forces of the P-51 at high speed. And in that test of those four US fighters the result was:
MANEUVERING STABILITY stick forces/g at Vmax
FG-1--5 lbs/g (too light)
P-47--7.5 lbs/g (ideal)
F6F--12.5 lbs/g (barely acceptable)
P-51--over 20 lbs/g (excessive)
With that test data and numerous anecdotal evidence it is clear the P-51 suffered from high stick forces at high speed, just like the 109, and I think the AH flight model should reflect this. Don't you?
Yes, in that test, the P-51 displayed higher stick forces than the other 3. I'm not convinced by this one test, and certainly not by any annecdotal evidence I've seen, mostly because I've seen just as much, if not more, technical and annecdotal evidence that contradicts it. Perhaps HTC can tell us why they didn't hit the Pony with the nerf bat like they did the 109? Unless you truly feel that Dale has an agenda, there has to be some sort of aerodynamic reason behind the disparity. Knowing how accurate an approximation the flight model is in Aces High, I'd say its the latter. Heck, I think Dale has even gotten some stick time in a P-51, so he'd be able to give a first hand account.
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I'm not convinced by this one test, and certainly not by any annecdotal evidence I've seen, mostly because I've seen just as much, if not more, technical and annecdotal evidence that contradicts it.
Could you please post some of this technical and anecdotal evidence that the P-51 had light controls at high speed?
Unless you truly feel that Dale has an agenda, there has to be some sort of aerodynamic reason behind the disparity. Knowing how accurate an approximation the flight model is in Aces High, I'd say its the latter.
I don't think the HTC staff has any agenda for or against certain aircraft; we all know that the AH flight model of some aircraft is spotty at best, unless you think the Zekes should be able to dive and manoeuvre at high speed like they do?
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Could you please post some of this technical and anecdotal evidence that the P-51 had light controls at high speed?
Is that compared to other fighters?
On Jan 1 1945, the 487FS took off with full tanks at Asch and immediately engage the LW fighters that were attacking the airfield.
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Is that compared to other fighters?
On Jan 1 1945, the 487FS took off with full tanks at Asch and immediately engage the LW fighters that were attacking the airfield.
What does that say about the P-51's stick forces at high speed?
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Yes, in that test, the P-51 displayed higher stick forces than the other 3. I'm not convinced by this one test, and certainly not by any annecdotal evidence I've seen, mostly because I've seen just as much, if not more, technical and annecdotal evidence that contradicts it. Perhaps HTC can tell us why they didn't hit the Pony with the nerf bat like they did the 109? Unless you truly feel that Dale has an agenda, there has to be some sort of aerodynamic reason behind the disparity. Knowing how accurate an approximation the flight model is in Aces High, I'd say its the latter. Heck, I think Dale has even gotten some stick time in a P-51, so he'd be able to give a first hand account.
If we look at the report of the Joint Fighter Conference, we see a cross section of pilots with a variety of opinions. Since I have a copy, let's review their test reports on the P-51D, those elements related to control forces. There were two alternative grading systems a pilot could choose from. Good/Fair/Poor or High/Moderate/Light. Here's the grading for the P-51D in terms of control/stick forces.
Elevators: 5 said good. 2 said fair. 1 said poor. 1 said high. 2 said moderate. 16 said light.
Ailerons: 7 said good. 5 said fair. 0 said poor. 1 said high. 3 said moderate. 13 said light.
Rudder: 5 said good. 7 said fair. 0 said poor. 9 said high. 3 said moderate. 3 said light.
Stick force during high speed dive: 5 said good. 0 said fair. 0 said poor. 0 said high. 1 said moderate. 10 said light.
In summation, this large majority of this group thought that the P-51D had light to moderate control forces at high speed. Rudder force was deemed somewhat high, but easily trimmed out.
So, it seems to me that what this mixed group of combat veterans and test pilots concluded should be considered reasonably valid.
No one knows how the P-51 was rigged in that published test of warbirds. I am fairly confident that none of the pilots associated with that test ever flew a fighter in combat, much less a WWII fighter. The group at the Joint Fighter Conference included some well know combat pilots, the Chief Test Pilots of all major fighter manufacturers as well as senior Test Pilots from the AAF and Navy.
My regards,
Widewing
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Widewing, was the stick forces of the P-51 actually measured? Like in the 1991 test where they claim 20 lbs per G at Vmax for the P-51. Do you have any other stick force measurements of the P-51 at high speed?
The Society of Experimental Test Pilots sounds like a very competent group of people...
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Widewing, was the stick forces of the P-51 actually measured? Like in the 1991 test where they claim 20 lbs per G at Vmax for the P-51. Do you have any other stick force measurements of the P-51 at high speed?
They didn't measure forces. It was strictly personal preference. I may have some data on measured stick forces, but I have no idea where it may be off hand. I have several terabytes of backup drive space to search... Could take a while when I have some time to look.
The Society of Experimental Test Pilots is a very respected group, and I personally know the one of the group's founders, Dudley Henriques. However, Dudley will disagree with their findings on stick force and he has several thousand hours in P-51s.
<edit> I'll shoot Dudley an email to get his thoughts...
My regards,
Widewing
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Yes, that's why I'm interested in the measured data; it is without bias or personal preferance. A stick force of 20 lbs per G is a stick force of 20 lbs per G no matter who tests it and writes the report. That number can then be compared to other aircraft, just like the Society of Experimental Test Pilots did in their test.
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Could you please post some of this technical and anecdotal evidence that the P-51 had light controls at high speed?
Just to reinforce what WW posted, and forgive the lack of organization here...
In the dive recovery, the elevator force is very light and caution must be observed not to attempt too fast a recovery as over acceleration will result.
Quoted from http://www.wwiiaircraftperformance.org/mustang/P-51B-Spin-Tests.pdf Paragraph 3.A.a. describing spin recovery procedures
Recovery in any case must be gradual and executed with extreme caution since relatively light elevator stick forces or rapid application of trim may very easily result in the application of excessive load factors...In no case is elevator trim necessary to aid recovery...
Quoted from http://www.wwiiaircraftperformance.org/mustang/p-51d-dive-27-feb-45.pdf Paragraph C.2.f. describing compressibility dive recovery procedures
As far as anecdotal goes, I personally feel I would fail to articulate anything better than the aforementioned Mr. Clarke who most eloquently stated:
He said the report was the "biggest bunch of crap I've ever heard"
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Here is my question to Dudley:
There was a test performed by some members of the Society of Experimental Test Pilots in 1991. They tested a P-51D, F4U-1D, F6F-5 and a P-47D. In this test, they rated the control forces of the P-51D as being excessively high when dived to Vmax air speed. In contrast to this, the many test pilots who participated in the Joint Fighter Conference or October 1944 concluded that control forces were light to moderate in a high-speed dive. Since these results are at opposite ends of the spectrum, I thought that I would seek the opinion of someone who has a vast amount of P-51 time. What are your impressions?
Dudley's reply:
"About the Mustang; my experience is limited to the late model D. Our airplane had the metal elevator with the decreased incidence and was fairly stable in high speed dives. I never had it all the way out to Vmax which was .75 or 505mph whichever occurred first, but I did several high speed dives in the airplane with no issues except an increasing amount of stick pressure required to counter nose tuck above about .65 if I didn't retrim.
If I had to fault anything control wise about the Mustang it would be the ailerons above 300mph.
My impression was that the stick forces increased for bank above that airspeed. I should note that this was fairly normal for all prop fighters of the era more or less. My impression is that ailerons peaked at about 300."
My regards,
Widewing
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Thanks Widewing, that was very nice of you to do. Unfortunately it still leaves unanswered question, and brings up new ones. Are there other measured tests done on the P-51's stick forces at or near Vmax? When was the metal elevator with the decreased incidence in service, and how did the earlier fabric covered elevators perform? Do you have more friends in "high places" that might shed some light on this issue? ;)
Thanks again!
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Diehard/Stoney,
I have an orginal copy of this report (I have the entire Symposium) from the Society of Experimental test pilots.
They did not select the P-51 as being the best, they selected the FG-1. I can post the rest of the report when I get a chance. The quote was something like "The weapon of choice was"... the FG-1.
One other point about these test that is over looked is the precondition of the test, the F6F was underweight during the test and none were full however some were under "combat weight".
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Cool! Do you have a digital version that you can share with us? Or is it copyrighted?
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What does that say about the P-51's stick forces at high speed?
Guess you didn't make the connection between the comments about the instability of the P-51 loaded with fuel and my comment.
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Yes, but the point of contention was the stick forces. In any case your comment didn't say anything at all about the instability; only that the P-51's engaged in combat, not what limitations the pilots had to adhere to. They also had help from P-47's of the 390th FS which had already engaged JG11 when the 487th took off; both Sprecht and von Fassong (the old hands of the JG11 raid) were downed by the 390th FS' Jugs, not the Ponies, and the rest of JG 11 were mostly greenhorns.
From the Memoirs of 1st Lt. Alden P. Rigby on that day:
"I kicked the tires, and climbed aboard at 9:00. The plane had been warmed up, and the tanks -topped off. The cock-pit was warm, and I was ready for a comfortable ride, as I rolled into position behind the Col. The P-47s had taken off a few minutes earlier, and headed straight for the front lines below the clouds. We had just gotten the green light from the makeshift tower, when we noticed bursts of flak just East of the field. Surprise, and even shock would be an understatement. We next saw what looked like at least 50 German fighter aircraft about to make their first pass on our field. We could not have been in a worse position, unless loaded with external fuel (or bombs). We were sitting ducks, and our chances were slim and none. It was not a difficult decision to take off, since that was the slim chance. The next 30 minutes were filled with action and anxiety, that perhaps had not been seen, or felt before or since. I had turned on my gun heater switch earlier, and now had the presence of mind (and prompting) to turn the main switch on.
The take-off roll was very close, rapid, and somewhat organized. We did not wait for help from the tower, or our own departure Control Officer. We just went. I am certain there were a few short prayers to just get off the ground. I had my own sort of set prayer, consisting of 6 words that had been used many times. Being caught on the ground was simply a fighter pilot's nightmare. We had made the situation even worse by having our fuselage tanks filled. This would make a big difference in our maneuverability, until about 50 gallons could be burned off. This would be my first take-off ever with the gun sight illuminated on the windshield. Things were happening too fast to even be afraid, that could come later. There was no training to cover such a situation, instinct simply had to take over, and it would have to be an individual effort."
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When was the metal elevator with the decreased incidence in service, and how did the earlier fabric covered elevators perform?
Those two reports I posted were created with P-51s with fabric elevators. What does decreasing the tail incidence have to do with elevator control force levels? That's merely a longitudinal stability issue.
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What does decreasing the tail incidence have to do with elevator control force levels?
I don't know, that's why I asked.
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Diehard,
I have a copy of the entire Symposium that was performed in 1989. It contains about 350 pages on flight test done by many test pilots on everything from the B-58 Hustler to the AD-1 Skyraider. The WW2 Fighter piece is actually rather small part of the symposium. I don't know that I would be violating any copyright laws by scanning and posting the report as they did not even charge me to receive a copy I requested.
It may take me a few days to get to this but I promise I will get it scanned. I have seen incomplete versions posted around but never the entire report. Like most reports it raises as many questions as it answers.
The abbreviated version posted in this thread after reading it I have to say is really paraphrased and leaves out much critical information. Having said that it is a great piece of test data and worth mulling through again and again.
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Thank you! Looking forward to it.
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You can purchase this paper from the society of experimental test pilots.
http://www.setp.org/ (http://www.setp.org/)
Do a non-member search and look for paper No. 1735, it will cost you $10.00 to get it.
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The 2000hp and 1500 hp ratings were max ratings. That means WEP.
However WEP was never used. Max continuous was used except for climb, where military was used. So basically the tests are done on cruise settings. Not exactly competitive stats at those reduced settings. Wartime testing pushed the planes more because thousands were available. Newer tests don't dare risk the multi-million-dollar assets that are almost irreplacable in this day and age.
Interesting, but not as valuable as WW2 era tests.
Your point is valid as the max potential of a 51D with a 1650-9 depended on 150 grade fuel and 100L would not yield anywhere close to Low Blower max at 10,000 feet. 1900Bhp vs 1500Bhp is huge in climb and acceleration and would help in turn. Having said this all WWII P-51D had 1650-7 which had max 75" hg vs 90" for max 1650-9.
The part of the report that I read several posts earlier stated 1650-9 which had max TO power of 1390 Bhp with 61" and 1500Hp at 61" at critical altitude for Low Blower. @10K the BHp ~= 1460
WEP in Low Blower at critical altitude @10,100 ft = 1930 BHp @3000 rpm, 80" (wet) but needed at least 130 grade and probably 150 to get 80"
The 1650-9 was finicky w/Bendix Stromberg Carb and often had trouble getting full potential horsepower.
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Thanks Widewing, that was very nice of you to do. Unfortunately it still leaves unanswered question, and brings up new ones. Are there other measured tests done on the P-51's stick forces at or near Vmax? When was the metal elevator with the decreased incidence in service, and how did the earlier fabric covered elevators perform? Do you have more friends in "high places" that might shed some light on this issue? ;)
Thanks again!
I know from the 355th FG Histories in the Engineering section that the P-51D-20s (and K-10s) all arrived with metal elevators and the Service groups received their field mod kits which came faster than the -20s to ETO. IIRC the metal elevators were retrofitted to all B/C/D/K starting in Aug-Sep-1944, along with reverse rudder boost. The increased negative incidence of the horizontal stabilizer accompanied the -20 and later rero fitted to all earlier models.
The incidencs changed from 2 degrees to 1/2 degree w/metal elevators. That should have had the effect of more 'down force' per degree AoA, thereby reducing the stick forces required to pull out of a dive - but also require slightly more nose down trim throughout the flight profile for level flight.
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Now let me guess.
You're new here.
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Loving this post...
But most of these facts reported are personal experiences from a singular pilot.
I'm told my Ford sucks and I should buy a Dodge as well based from my friends experiences...Most of these stories are opinions as a result.
We include more performance data than IMHO was likely used by a pilot in combat.
We are ignoring tactics and training of each pilot.
Even reputable pilot's accounts, only tell the story of that individual, and how he decided to fly a particular model airplane. (assuming that individual was not involved in the design and testing of said aircraft)
I would make a wild guess here ;) That the pilots were trained specifically to use their airplanes strenghts in combat, and mitigate their weaknesses versus their opponents.
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Now let me guess.
You're new here.
You are correct. I am a pilot, an aero engineer by education, structures guy for some time before moving into Information Services, have some time in a 51D that my father bought in 59, have written Angels, Bulldogs and Dragons - history of the 355th FG during WWII and know a lot about ETO and the Mustang.
I have a hard time keeping my mouth shut, can answer a lot of questions I have seen posted and easily persuaded to move on if my presence is not welcome. I am retired but continue to consult to augment my fetishes.
Hello.
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You are correct. I am a pilot, an aero engineer by education, structures guy for some time before moving into Information Services, have some time in a 51D that my father bought in 59, have written Angels, Bulldogs and Dragons - history of the 355th FG during WWII and know a lot about ETO and the Mustang.
I have a hard time keeping my mouth shut, can answer a lot of questions I have seen posted and easily persuaded to move on if my presence is not welcome. I am retired but continue to consult to augment my fetishes.
Hello.
Welcome to the community. Your experience and expertise will be welcome here. We can always use more aerodynamics and history experten... :salute
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Thank you Stoney.. BTW your avatar is one of my most admired persons in our history..
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In addition to what others have provided so far I'll give you these quotes:
Robert C.Curtis, American P-51 pilot:
On two other occasions ME 109s got away from me because the P 51d could not stay with them in a high-speed dive. At 525-550 mph the plane would start to porpoise uncontrollably and had to be slowed to regain control. The P 51 was redlined at 505 mph, meaning that this speed should not be exceeded. But when chasing 109s or 190s in a dive from 25-26,000 it often was exceeded, if you wanted to keep up with those enemy planes. The P 51b, and c, could stay with those planes in a dive. The P 51d had a thicker wing and a bubble canopy which changed the airflow and brought on compressibility at lower speeds."
The Naca 45-100 wing was on the XP51, the P51-1, the P51A/B/C and P-51D/K - All the same wing with one difference when the D/K was developed - namely a longer root chord to accomodate the new main gear and door. Gene lednicer did a very nice VSAero simulation on the B/D and there is virtiually no difference in the drag, but the D canopy was BETTER than the B w/birdcage and Malcolm hood. The wing on the P-51H was the Naca 66-(1.8) 15.5 so it was thicker than the 14.8% 45-100
Thomas L. Hayes, Jr., American P-51 ace, 357th Fighter Group, 8 1/2 victories:
"Thomas L. Hayes, Jr. recalled diving after a fleeing Me-109G until both aircraft neared the sound barrier and their controls locked. Both pilots took measures to slow down, but to Hayes' astonishment, the Me-109 was the first to pull out of its dive. As he belatedly regained control of his Mustang, Hayes was grateful that the German pilot chose to quit while he was ahead and fly home instead of taking advantage of Hayes' momentary helplessness. Hayes also stated that while he saw several Fw-190s stall and even crash during dogfights, he never saw an Me-109 go out of control."
My farther Bert Marshall, Jr.and his wingmand Chuck Hauver 354FS/355FG saw on go out of control in a steep dive near Mulhausen on July 28th for my father's fourth acore. He was also shooting at it so the result remains somewhat inconclusive.[/b]
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Welcome to AH, Drgondog.
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Thank you Brooke - I will 'spell check' my posts a little more carefully next time.
Regards, Bill
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Thank you Brooke - I will 'spell check' my posts a little more carefully next time.
Regards, Bill
Nah, don't worry about anything like that. AH has a spectrum of folks from quite knowledgeable folks to folks who will argue with you until the end of days and won't be convinced even if they are misunderstanding some aspect of aerodynamics and a spectrum of folks from polite to cranky and belligerant.
Just keep in mind that there are many people here who appreciate contributions from folks like you and hope that you enjoy and participate in AH.
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thank you brooke - i sent an email about a subject I have found little to shed theoretical light upon..
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interesting thread :aok
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Now, someone interpret it for me.
Jug > *