P-38J-L questions.

[juzz]

Hasn't HTC already said that the incorrect stall behaviour is just an unfortunate limitation of the AH flight modelling?

On the plus side, it gives the P-38L some very nice snap roll abilities which no other plane has...  

[Maverick]

All,

I got curious and dug out a book I have covering a number of WW2 American Aces. The title is "Fighter Tactics of the Aces" Published by World War Two Publications.

I was looking for a reference to Tommy McGuire who was in contention with Dick Bong for top ace status. I recall reading that Tommy died after going after a kill low and got slow. His plane (P38L) spun and he wasn't able to recover in time. I also recall he attacked with his drop tanks still on and violated a rule he stressed with others which was to never get slow with a tank in an attack as the 38 would spin. He was killed doing just that. The account I recall was that he did stop the spin but mushed into the trees and was killed in the impact.

I couldn't find that excerpt so consider it suspect.

I did come across something else however. Another 38 ace, Cpt. Elliot Summer (610 combat hours & 10 kills in Pacific) was asked for a letter about tactics to use against the "nips". It's about 3 pages long but he did have one section about the 38L and the use of a "G" suit in actual combat. I will quote that section.

"c. Tactics probable with P-38L and "G" suit.

1. This combination makes possible many new tactics both offensively and defensively.

2. The "G" suit, aileron boost, and dive brakes allow for very high speed dives, tight turns, abrupt pull-outs, and a high rate of roll. I found it impossible for me to black out although I indicated 575 MPH, dropped dive flaps and reefed in as tight as possible. The pullout was so severe as to buckle the wings.

3. There is a possiblity that at speeds of around 300 MPH the combination of "G" suit and P-38L would allow for turning with the nip.

4. One thing is certain; rolls and tight turns when done at indicated airspeeds of 300 MPH and over cannot be followed by any Jap plane thus far encountered in this theater."

I am assuming all speeds were in indicated MPH as no one is going to take time to convert to TAS in a dogfight.

For this reason and information it is my belief that the 38L is "undermodeled" and Citabria might just be right.

As to the notion that a twin engined plane won't spin if both engines are turning equally, that is false. Given a sufficient reduction in speed any conventional plane will stall. A stall in anything but a wings level attitude can lead to a spin. Quite a few twin engine planes complete with counter rotating props have spun when slow particularly in the traffic pattern. Having twin engines doesn't guarantee that one wing won't drop lift before the other. If it does then the plane will spin. Many newer twin aircraft have proven this out as inexperienced pilots get them too slow in the pattern.

A spin is a planes way of telling you that one wing can't provide as much lift as the other. The "flying" wing will lift up and the plane will curve around the "dead" wing. The curve around the "dead" wing will maintain the spin as it doesn't get back to flying speed unless corrective action is taken to stop the spin.

Mav

[Jigster]

Well spinning the P-38 was difficult however, due to neutral forces(other then pilot input) on the roll axis in a stall situation. In AH the nose doesn't even drop if you hold it level...it snap rolls to the right or left, which is kind of annoying  

The biggest problem is that aileron lock up at compression though.

[Zigrat]

aileron lockup at onset of compression is correct

well mabye not lockup but severe degredation in ability better word

[bolillo_loco]

adios mio...estoy tratando

stalls and spins. mc guires plane didnt spin when it stalled. he performed a high bank turn at low altitude with two 165 gallon drop tanks. even if he didnt stall any plane banked high will drop altitude and it is something you didnt want to perform in any plane at low altitude.

I do not understand why people insist the 38 spun when it was stalled in anything but a wings level flight attitude. too many books point out that you could stall a 38 in a high speed turn and it would just mush out on you or the turn would slacken up, all you had to do to recover was to ease up on the stick.

also as somebody else pointed out even when you have the wings level the 38 will snap into a spin in aces high.

as far as the flight model being limited to not being able to correct the 38s glaring errors thats too bad. it isnt worth the 30 bucks a month. I have 3 other ww2 games I can fly for free that also have incorrect flight models.

I must go check out my joystick. I flew the mustang and it seemed to roll ok, but I am serious I couldnt roll the 38 at any speed.

[This message has been edited by bolillo_loco (edited 12-10-2000).]

[bolillo_loco]

also with this theory that some seem to have here that any plane when you stalled will spin is true in part, but some of them you had to force them to spin.

the 38s wing stalled from the wing roots out. this meant that not only did it give you alot of warning it kept the plane very controllable.

also since the wing stalled from the roots out the wing lost its ability to hold the airplane in the air and thus it would just nose out or mush out if you will.

the reason it wouldnt spin were two fold as I see it, no propeller torque nor slip stream effects on the fuselage due to counter rotating props and also even though the wing lost its lift it didnt loose it on the outer 1/3rd of the wing, to cause one wing to lift that much more than the other.


since wingspeed at the tips seems to be critical when compaired to wing speed at the roots lets look further at this. the wing outboard the engines still had lift where one wing tip would have more airspeed than the other. inboard of the engine nacells it isnt as critical since both those sections of the wings have very similar air speeds.

I am not talking about a mustang, spitfire, or fw 190 wing that when it stalled the whole wing stalled at once, these are they types that gave you nasty stall habbits. not the 38s.

once again pilots manuals and a cazillion books state "in either high speed or low speed stalls the P-38 would not spin. if flaps and wheels were dropped it had a slight tendency to drop a wing, but once the controlls were eased off the plane would right itself naturly and the wing would pick back up"

do you understand now?

[This message has been edited by bolillo_loco (edited 12-10-2000).]

[Citabria]

p-38L is pretty neutered. it has always been an easy target in AH but now its even easier. its flaps dont give it a great increase in turn ability so it cant hang with any other aircraft at any speed in AH.

it snap rolls hard if it gets anywhere near a stall.

i wish the 1.03 p-38 stall model was put back on it. at least that one was a little better.

[Vermillion]

Put the P-38L against its historic PAC opponents in a historic setting (ie no arena style combat) and you will see results similar to what the books describe.

Put it in an arena against much faster opponents, tougher opponents(compared to Japanese aircraft), and much more heavily armed opponents, then things will be much different.

You just can't compare historical results to arena combat.

------------------
Vermillion
**MOL**, Men of Leisure

[Jigster]

Can you explain to me why being up against more heavily armed and faster planes would effect how the 38 stalls, spins, and how much the fowler flaps contributed to lift?  

[wells]

Jigster,

The Fowler flaps increased wing area with the first notch, so you get a 13% increase in lift, a 13% increase in drag and a 13% decrease in turn radius.  Sustained turning speed will decrease slightly, but not as much as the radius decreased, so the turn rate will increase by about 6%.

Had the flaps not been of fowler type, you would get a 28% increase in drag for your 13% increase in lift.

It is my understanding that the so called butterfly flaps on the Japanese planes work similarly to a fowler flap except they don't extend backwards, they extend downwards becoming individual flying surfaces, rather than an extention of the wing itself, but they still increase the overall lifting area.

[niklas]

wells, what do you think:

when the P38 increases the wing area with a fowler flap, doen´t this also reduce the aspect ratio? And do you really think a fowler flap is as good as a clean wing with more area (13% area > 13% more drag)?

niklas

[bolillo_loco]

hey thats interesting on the japanese type flaps. I have always wondered what they mean by butterfly type flaps.

I am not debating turing ability here. w/o the flaps a 38 should have only a slight edge on a 47 and with the maneouvering flaps it should now have an advantage over the mustang.

now low speed all out turn radius when you use half flaps or more thats a different story a 38 should have a very good edge over almost all the single engined aircraft.

what I am debating is why does the 38 spin when it is stalled? I keep hearing quite a few say that it should spin when it shouldnt spin at all provided both engines are running.

I have read thru the older threads and I feel that the 38 was constantly modeled with worse and worse performance due to a majority seeming to dislike this aircraft. I will not make claims which exaggerate this planes performance, but I have noticed quite a few negative posts about this plane which just were not true or if they are they can be traced to pre P-38J models.

[bolillo_loco]

sorry I forgot to pose another question for wells.

since the 38 used fowler type flaps which not only had less drag for the same degrees of deflection, but they also provided more wing area and also they increased the wings lift coefficient greatly vs the mustang using the same degree of maneuvering flap use.

since both the 51 and 38 had these flaps lets look at turing performance of these two planes. w/o flaps the mustang should have an edge over the 38. with the flaps the 38 should now have the edge over the mustang enough that after a few turns it should get onto the 51s tail.

use of more flaps only makes it worse for the 51 and the slower it gets the worse it is for the mustang because stall habbits now become an issue.

one more point on the figures that people caculate. the wing root fillets seemed to help the airflow remain laminar to the wing. it is said this lowered the 38s stall speed. are you guys figuring this wing root fillet into your mathmatical work?

[wells]

Niklas,

That's a tough one since the engine nacelles increase the effective aspect ratio, preventing spanwise flow.  It would be debatable if the effective aspect ratio wouldn't be greater than the geometric 8.25, even considering tip losses, of which the P-38 has very little with it's very high taper ratio and rounded tips.

The clean stall speed of a P-38J/L is around 115 mph (CAS) at 17500 lbs, which is the same as a P-47D.  The P-38 had weak directional stability and high yaw inertia, which is
part of why it was less likely to spin, it just slipped if a wing dropped, without the tail following.  The resultant slip, combined with dihedral effect would right the wing again, kindof like a dutch roll effect instead of an incipient spin.  Unfortunately, it would seem that gunnery suffered as a result and guys like Bong, preferred to be close before shooting.

Another interesting note is that the power on stall speed was higher than the power off stall speed.  This was probably due to the direction of the engine rotation.  The angle of attack would be increased on the inner wing portions from propwash, causing them to stall sooner than they would in freestream air.

[Jigster]

I was kinda being sarcastic but the aerodynamic information is more then welcome