P-38 kill ratio...out of whack.

[BnZs]

A few things for those who do not know to consider.

The P-38 had a rather thick wing, called a high aspect ratio wing.

Aspect ratio actually defined the square of the wingspan divided by the area of the wing...for us country boys, that means long narrow wings like on a glider have a high aspect ratio and short stubby ones are low aspect ratio. But you are right, the P-38 *does* have relatively high aspect ratio and this is a positive for it in turns and climbs.

[thorsim]

so changing the AOA and the constant skid that results (airframe not in line with it's direction in the pitch axis) does not result in a loss of speed?

are you really trying to make that argument?

tell me are the dive flaps stated as inconsequential to top speed in level flight in the POH? or do they suggest you might go faster with them up?  

The dive-flaps we were speaking of don't do anything except help the nose pitch up at high speeds.

We were not discussing the maneuvering flaps, who do cause drag in game.

[BnZs]

so changing the AOA and the constant skid that results (airframe not in line with it's direction in the pitch axis) does not result in a loss of speed?

are you really trying to make that argument?

tell me are stated as inconsequential to top speed in level flight in the POH?   

Are you *sure* you've grokked the fact that the dive flaps on the 38 and the maneuvering flaps are two different things???

What it amounts to is that in game that the dive flaps don't even offer the 38L an advantage in deceleration. The only thing they offer the 38L pilot is increased ability to pull out of compressability dives. They have nothing to do with maneuverability, decleration, or anything else that could conceivably be an advantage in combat or an ACM "trick".

[Captain Virgil Hilts]

I did see a film of their purpose on Great Planes I believe. The dive 'brakes' according to the program [And the supporting war time film, possibly a pilot training film] did not and were not designed to slow the plane down to non-compressible speeds. Instead they changed the shape of main wing's airfoil which caused the turbulent flow to exit the wing at much lower point restoring laminar flow to the evelator at the tail section. This restored elevator operation and allowed the plane to pull out of the dive. I believe this was developed in leu of forcing the plane to slow down.  It is relavant to notice that the elevators of the Lightning are almost in the same plane as the main wing. I think this is why the plane suffered from compression effects more than other planes.

Vinkman, you are wrong. The relationship between the positions of the wings and the elevator has nothing to do with compression, or how it effects the P-38. Ignore "Great Planes" and the rest of the television crap. They are wrong, very wrong. To get the truth, you have to read.

Compression on the P-38 was strictly a function of the profile of the wing of the P-38. There was no such thing as elevator flutter on the P-38 either. Some general had those little counterweights added to the elevator on the P-38. They did nothing at all, as not only was there no elevator flutter, but Kelly Johnson had already not only put counterweights on the inside the elevator, but he also had the skin made thicker and the internal bracing increased, in order to make the elevator heavier and more stable. Kelly Johnson, in referring to those external counterweights, was quoted as saying "they were useless, they didn't do a damned thing, other than maybe kill some pilots who had to bail out".

Again, the two things that increased the speed at which compression began, and reduced the effects of compression, were the increase in the radius of the fillet joint where the wing attached to the center nacelle (along with improved fit) and the dive flaps. Nothing that was done to the elevator after the original design helped.

When the P-38 (or any plane, as the P-47 suffered from compression as well) entered into compression, the elevator didn't matter at all, as no deflection of the elevator could overcome the amount of force that the wing, suffering under compression, was pushing down on the nose with. In fact, if it had been possible to get the elevator on the P-38 to deflect enough to force the nose up, the tail would snap off under the load. In fact, Lockheed test pilot Ralph Virden was likely killed when the spring tab apparently broke on the elevator in a dive, allowing the elevator to reach full deflection. The entire tail section snapped off, and Virden was killed in the resulting crash.

[Ack-Ack]

so then they help you in a climb, and do not hinder your top level speed ???

they slow you down, can gravity and thrust compensate? sure.

do they do other things like change AOA? sure.

however that does not change the fact that they slow you down, at least in the real world.

just like Fowler flaps slow you down ...

in the real world.

++S++

t

Sticking your arm outside of your car window at 55mph, sure you introduce drag but does it slow you down enough that sticking your arm out results in a braking motion?  No, and the same for the dive flaps on the P-38.  Yes, they did introduce drag and but was the drag sufficient enough to bleed energy as though you applied an air brake?  No.

Just looking at the design of the dive flaps, one can clearly see that the function was not to slow the plane down but affect the center of pressure distribution so that the wing would not lose its lift.  They did not bleed energy like the Fowler and normal flaps when deployed.

Dive Flaps


[click on image for larger picture]
 

P-38 hybrid flap system (Fowler + conventional hinged flap)



As you can see, it's easy to spot which one has a significant impact on the P-38's energy when deployed.

ack-ack

[CAP1]

so then they help you in a climb, and do not hinder your top level speed ???

they slow you down, can gravity and thrust compensate? sure.

do they do other things like change AOA? sure.

however that does not change the fact that they slow you down, at least in the real world.

just like Fowler flaps slow you down ...

in the real world.

++S++

t

read this.

http://www.kazoku.org/xp-38n/articles/p38info.htm

saying that dive flaps slow you down, but gravity and thrust compensate, is like saying global warming causes cooler temps.

http://books.google.com/books?id=qhEkkjp1bnMC&pg=PA36&lpg=PA36&dq=p-38+dive+recovery+flaps&source=bl&ots=O9FVVBMGeJ&sig=L5jvEKo-DnZJuAphnFgtl_kZ6gI&hl=en&ei=mxe-Sof-LMeg8AbH842hAQ&sa=X&oi=book_result&ct=result&resnum=2#v=onepage&q=&f=false

the dive recovery flaps change the lift of the wing. THIS causes a pitch up in the nose. the pitch up eventually causes you to slow down a little.

 maneuvering flaps are used for...well.....maneuvering. ponys have them too. in fact, i think ponys can deploy 10 degrees at over 400 mph, but i'll let a pony driver fill us in on that.

 what you need to do, is to fly the bird. fly it here. you'll see all of what we're all trying to tell you.


 sometimes, you seem as if you are a pretty sensible guy. would common sense not suggest that if everyone else is saying one thing, and you're saying another, that maybe...just maybe, you might not be right?

 i snipped the film down...i'll post it soon as i eat something.

[thorsim]

so how is that an argument for correctness?

Are you *sure* you've grokked the fact that the dive flaps on the 38 and the maneuvering flaps are two different things???

What it amounts to is that in game that the dive flaps don't even offer the 38L an advantage in deceleration. The only thing they offer the 38L pilot is increased ability to pull out of compressability dives. They have nothing to do with maneuverability, decleration, or anything else that could conceivably be an advantage in combat or an ACM "trick".

[CAP1]

The problem is that you have failed to find a single instance where the P-38's flight performance ingame is unrealistic. You keep harping on flaps, acting as if they are modeled incorrectly in AHII. In r/l flaps increase both lift and drag...in AHII they increase both lift and drag...and deploying too much flaps in AHII brings about diminishing returns too.

when will HTC himself pop in here?

does this guy know that ht has real time in a pony? and owns and flys his own aerobatic airplane?

[Shuffler]

Reading would help answer so many questions.

[Ack-Ack]

when will HTC himself pop in here?

does this guy know that ht has real time in a pony? and owns and flys his own aerobatic airplane?

Considering how HiTech was basically conversing with a brick wall in Thorsim's last thread, I don't think HiTech is willing to go through it all again.

ack-ack

[CAP1]

so changing the AOA and the constant skid that results (airframe not in line with it's direction in the pitch axis) does not result in a loss of speed?

are you really trying to make that argument?

tell me are the dive flaps stated as inconsequential to top speed in level flight in the POH? or do they suggest you might go faster with them up?  

actually, when the nose pitches up, the direction of travel changes accordingly.

[BnZs]

Thorsim:
You are very hard to pin down aren't you? You started by alleging that the dive flaps and maneuvering flaps allow unrealistic ACM tricks. It has been shown that the dive flaps don't do anything useful to ACM and that the maneuvering flaps don't do anything they are not supposed to do, yet you continue to harp. Yes I imagine leaving the dive flaps hanging out in the breeze would cost you a few MPH in top speed, but so what? No one flies around the arenas when the things hanging out, they offer nothing except for when you want to pull out of a dive.

[Chalenge]

Vinkman, you are wrong. The relationship between the positions of the wings and the elevator has nothing to do with compression, or how it effects the P-38. Ignore "Great Planes" and the rest of the television crap. They are wrong, very wrong. To get the truth, you have to read....

COUGH!

Actually.... no. (not meant at you Hicks)

Downwash and aeroelastic bending of the tail boom was the P-38s problem. You can read all about it and the design of the P-38 'brakes' in the book 'Mechanics of Flight' by Warren F. Phillips (chapter 6). Dont bother reading this book if you dont understand calculus and physics (and I mean understand).

"Compressibility effects at high subsonic airspeeds can amplify the tendency for an airplane to tuck under in a dive as a result of aeroelastic bending."

The full description of the problem with the P-38 and the phenomenon are included and the relationship of wing (airflow) and tail position are all important but in the case of high subsonic airspeeds the placement is redundant since there is no good place to be.

In the case of the P-38 in particular (because of tail boom flexibility) continued flight at high subsonic airspeed should permanently affect the aircrafts ability to manoeuvre but it is also true of every airplane in the game.

[thorsim]

guys i believe the stand i took issue with is that "the dive brakes did not slow the plane down".

that statement is false "."

you can introduce all the design intent and situational exceptions you wish ...

but it does not change the fact that the above statement is false, even if AH does not model it that way.

my problem with the flaps is that they are distributed subjectively, and that the liabilities seem underrepresented to such an extent that the envelopes of the set are now very suspect.  

if you do not believe me please investigate what the F4U-POH says about flap deployments over 20deg and how that contradicts the situation in the game, and explain the p-40 flap deployment speeds relative to its POH.

BTW i am still waiting to hear any accounts of combat with flap deflections anywhere near the kinds used in the game that some people are finding success with.

it is a video game, don't try and justify the way you play it with real world examples, you can't.

it is just a game.

++S++

t

[Captain Virgil Hilts]

so changing the AOA and the constant skid that results (airframe not in line with it's direction in the pitch axis) does not result in a loss of speed?

are you really trying to make that argument?

tell me are the dive flaps stated as inconsequential to top speed in level flight in the POH? or do they suggest you might go faster with them up?   

The dive flaps on the P-38 do not change the angle of attack of anything. They do not result in a constant skid.

At top speed in level flight, a P-38 cannot reach compression. The only P-38 that could come close was the P-38K, and it did not do it either. So the dive flaps are irrelevant to top speed in level flight. They were not designed to be deployed there, and would not work there for their intended purpose. At speeds below 0.65 Mach, the air flow over the wing was not disrupted by compression, and therefor was not the same as the air flow at speeds over 0.65 Mach. Meaning what the dive flaps did below 0.65 Mach had absolutely no bearing on what the dive flaps did above 0.65 Mach.

The only thing the dive flaps do is change the shape of the wing to reduce the effects of compression, which is caused by the speed of the air over the wing going just sub sonic and super sonic in places.

I have no idea where you are getting the idea that the dive flap, deployed when the plane is in compression, changes the angle of attack. All it does, according to the Lockheed engineers that design it, is change the shape of the wing and redirect airflow over it so that the wing does not lose lift and cause the nose to tuck.

As a side note, compression would not cause the P-38 to break up, and even without the dive flaps, you could pull out of a dive if you stayed with the plane and continued to fly it. Colonel Cass Hough, P-38 test pilot and USAAF officer, dove from over 38,000 feet at an angle of 45 degrees, through 20,000 feet, recovering well before he came close to hitting the ground at over 7,000 feet. All of this in an early P-38 without dive flaps. And Tony Levier, a civilian Lockheed test pilot, who was the test pilot assigned with the comprehensive dive flap test program, reported speeds of 0.72 Mach and safe pull outs of 7.5G.