Author Topic: Couple of Early P-38 FM Observations  (Read 1402 times)

Offline Vermillion

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Couple of Early P-38 FM Observations
« on: March 01, 2000, 10:57:00 AM »
1.) Dive Speed limitations: Last night in my testing the P-38 has the same divespeed limitations as the P-51. It starts creaking and groaning at 500 IAS. According to AHT the divespeed limitations for the J/L were 440mph IAS at 1g (p.605), and my P-38 Pilots manual confirms this.

2.) Compression: I realize its not in yet, but couple that with #1 and this bird will be much different. Even with Dive Flaps/Brakes, its noted that the P-38 shouldn't exceed the dive limitations (440) by more than 20mph, because extreme nose tuck will occur.

3.) Induced Drag: The P38 FM makes the old "pre-gelded" Pony (the one everyone complained about no E loss in vertical manuvers)look horrible in comparison. I was amazed how I could pull into turns and manuevers and lose very little E. In the vertical its simply amazing. Last night I was at 30-31k, auto-leveled at WEP waited till my speed stabilized and turned on auto-climb. I zoomed up over 4,000ft !! Try that in any other fighter. This issue is very hard to quantify, but it seems like it is not in the similar range as the other planes currently in the game, especially given the size/weight and other design characteristics of the P-38.

4.) Roll Inertia: To me this is the area that the FM seemed the weakest. Now I don't doubt, given Pyro's meticulous attention to detail, that the sustained roll numbers are pretty close. But the initial roll rate is just as quick, and it reverses with very little to no feel of inertia. Something that should be pronounced given the engines outside the centerline of roll. Here is how the P-38 is described in AHT, and I have read similar descriptions in other sources.

 
Quote
The P-38 was a large heavy fighter not suited for quick "snap" or "slam-bang" manuevers, and had a particularly slow initial response in roll due to a high lateral inertia characteristic.  The problem was a slow start into a roll and thus an inability to switch quickly from one attitude to another, as in reversing from a turn in one direction to one in another.  As one pilot said "It was disconcerting to have a fighter barreling in on you, crank the wheel over hard, and just have the P-38 sit there. Then after it slowly rolled the first five to ten degrees of bank it would turn quickly.  The hesitation was sweat-producing. Many combat losses, particularly in North Africa, were attributed to this creaky initial rate of roll. Another pilot noted "The first ten degree's of bank came very slow."

Now, Im sure someone will jump in here and claim that because the L had hydraulic boosted ailerons, that is correct. Well.. that person would be wrong  

 
Quote
Power boosted ailerons, introduced the same time as dive recovery flaps, gave the P-38 pilot a lot more "muscle" to improve roll characteristics at high speeds, but did nothing to improve them at low to moderate speeds where maximum roll performance was dependent on full aileron deflection, instead of pilot effort

I personally talked to a WWII P-38 pilot on this issue when I toured the NASM Garber Facility in Washington DC.  He had flown the F, early J, and the L model. When asked how much the boosted ailerons helped, his exact words were with a chuckle "Not much".

Now in AH, the P-38 has very little feel of inertia and in my opinon actually has a quicker roll than some other planes like the N1K2.

Couple that with the low induced drag, and this bird will do an amazing series of flat scissors on the deck. It should be horrible at this.

The only weakness I could find in the P-38 last night was its large size, and that it had inheirited the infamous "glass tail" of the WB's P-38.

To be honest, this plane right now literally scares me more than any other plane in the game. Moderately fast, good climber, turns forever, accelerates quickly, and it has good guns with alot of ammo. I can't find a weak point with its performance.

MUCH more deadly than the F4U-1C ever was.

Will do some more hard testing on climb & speed later.

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Offline ra

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Couple of Early P-38 FM Observations
« Reply #1 on: March 01, 2000, 12:02:00 PM »
Good post Verm.  I hope HTC revisits this FM before too many people get hooked like in the old WB days.  

My first fight in a P-38 was against another P-38, merging at about 15K.  We kept doing vertical scissors all the way down to the ground, and even though I was nearing blackout on most turns, I never got below 220 mph.  We finally HO'd at ground level, he got my port engine then augered into a hill.  Even with 1 engine dead and fresh from a turnfight I was at 210mph at the moment he augered.  

The most striking thing during the scissors was that we would end up D1.2 apart at the outer point of the turns before zooming back in toward each other.  It really seemed more like 2 F-86's fighting.  A well flown P-38 will be untouchable, like in old WB.  

It needs some roll inertia and some more E bleed, as you say.

--ra--

[This message has been edited by ra (edited 03-01-2000).]

[This message has been edited by ra (edited 03-01-2000).]

Offline Westy

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Couple of Early P-38 FM Observations
« Reply #2 on: March 01, 2000, 12:09:00 PM »
 I was only able to fly for about 30 minutes last night but one thing I was amazed at when flying the P-38 was the lack of the stall sound going off in maneuvers.
 I know thats not much to go by. Untill you take inot account I suck as a combat pilot.  

 -Westy

Offline Hangtime

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Couple of Early P-38 FM Observations
« Reply #3 on: March 01, 2000, 12:12:00 PM »
LOL.. yah I saw some amazing stuff happinin last night w/ the p38's..  truly amazing.  

Brings back fond memories.  

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Offline wells

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Couple of Early P-38 FM Observations
« Reply #4 on: March 01, 2000, 12:21:00 PM »
The E retention is a bit too good right now.  Check the stall speed, 125 mph!  It currently has a better turn rate than anything else, although the radius is pretty large, second only to the 190!  

With regards to zoom ability.  The P-38 should excel at high altitudes where the TAS is highest.  A zoom from 400-200 TAS at that height = 4000'.  

If you watch Jeff Ethel's P-38 video, he starts centering the ailerons about 180 degrees before the roll ends, albeit slowly.

I did a moment of roll inertia calc based on the data in AHT.  Maybe Pyro could compare to his figure?

MoIroll (final value is metric):

Wing (52' x 6.3'; 1860 lbs):  18000
Booms (8' from centerline, 9000 lbs): 24300
Total (neglecting fuel in wings):  42300

Offline SnakeEyes

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Couple of Early P-38 FM Observations
« Reply #5 on: March 01, 2000, 11:16:00 PM »
Prefacing this by saying that I don't play AH since it moved out of Beta, all I can say it what I've felt about AH all along... it's WB 1.11 all over again.

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Offline Toad

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Couple of Early P-38 FM Observations
« Reply #6 on: March 02, 2000, 12:30:00 AM »
Snake,

...and did WB 1.1 develop into your favorite game?

 
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Offline Jochen

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Couple of Early P-38 FM Observations
« Reply #7 on: March 02, 2000, 01:36:00 AM »
 
Quote
Snake,

...and did WB 1.1 develop into your favorite game?

Touche!


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Offline Duckwing6

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Couple of Early P-38 FM Observations
« Reply #8 on: March 02, 2000, 02:39:00 AM »
WellS:

in regards of Zoom or Climb capablity TAS doesn't help ya any .. CAS (Indicated air speed corrected for installation errors) is the main factor .. because your wing will stall at always the same CAS even thou your TAS will be much higher at high altitude.
I see that you have the least drag at high altitude and therfore the highest TAS but you'll stall out before you can use those extra knots.

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Citabr

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Couple of Early P-38 FM Observations
« Reply #9 on: March 02, 2000, 02:39:00 AM »
heh

turn it into the sims worst flying aircraft is what it sounds like we need here  

I will still fly it even if that does happen.

Offline leonid

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Couple of Early P-38 FM Observations
« Reply #10 on: March 02, 2000, 04:37:00 AM »
Ol' SnakeEyes,

What you fishing for now?  I do believe you might want to try another 'lake', since the fish here are actually well fed

 


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funked

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Couple of Early P-38 FM Observations
« Reply #11 on: March 02, 2000, 11:01:00 AM »
Duckwing - Actually TAS does help you because it determines the amount of kinetic energy that you can use to zoom.  I think what Wells means is that the P-38L is the king of power-loading at higher altitudes, so it should zoom better than the others up in the nether regions.

Vermillion - About the transient roll response, remember that the roll acceleration (degrees/sec^2) is proportional to the rolling moment from the ailerons divided by the roll inertia.  Due to the hydraulic assist, at high speeds the P-38L rolling moments are enormous as are the damping moments which slow down the roll rate once the ailerons are neutralized.  

So P-38L roll acceleration and decceleration should be more rapid than many planes at high speeds.  But at low speeds it should perform poorly in this regard.

Offline wells

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Couple of Early P-38 FM Observations
« Reply #12 on: March 02, 2000, 12:22:00 PM »
300 mph example:

Wing Area occupied by each aileron: 3.7 sqm
Change in lift coefficient with full aileron deflection:  ~0.5
Distance from centerline: ~6.0m'
Roll torque @ 300 mph IAS: 245000 N.m

//divide by Moment of Inertia to get acceleration//

a = 5.8 rad/sec/sec (initial)
a(average) ~ 2.9 rad/sec/sec

Maximum roll rate @ 300 mph ~ 1.4 rad/sec

Therefore, it would take about 0.48s to reach maximum roll rate, in which the plane would roll through about 19 degrees.  Upon centering the ailerons, roll would stop in about 1/2 the time.

Comparison to 100 and 200 mph speeds

100 mph:  t~1.5s / 19 degrees
200 mph:  t~0.72s / 19 degrees

Notice that the plane will roll through the same number of degrees in order to get into and out of maximum roll rate.  It just takes different amounts of time to do so at different speeds.  

You could test it in AH at say 200 mph (the slower the better).  Time one roll from a standing start.  Then do a complete roll before timing the second one at max roll rate.  Try to keep speed as close to what you started at as possible throughout the maneuver.  You should get about 5% difference in times.  I'll do some testing and see what happens.  Where's Popeye?  

Offline MiG Eater

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Couple of Early P-38 FM Observations
« Reply #13 on: March 02, 2000, 04:31:00 PM »
Flew the -38 for the first time in combat last night.  I have a few observations:

This airplane appears to have very low induced drag, helping its amazing E-retaining abilities.  Its deceleration in sustained high rate turns is quite low (both vertical and horizontal).  In one fight, I lost an engine and was still able to maintain a 190 mph horizontal scissors on the deck with another -38 that had two engines turning.  (One snapshot to his port boom was all it took to end the fight.) At first I thought it was all the air blowing over the wings from the two engines but single engine operation afforded only slightly reduced acceleration capabilities and possibly a smaller turn radius.  

Glide ratio with engines out and 25% fuel, no stores in clean config is just about 10:1 at 12k improving to 11:1 at 2k.  No problems reaching any base if you have 10,000 feet over friendly territory with no fuel or dead engines.

Rudder affects the P-38 much different than any other airplane.  There is less overall yaw and far less drag from this three boomed twin ruddered airplane than any of the single rudder, one fuselage fighters.  The P-38 seems to actually sidestep/skid more than other airplanes especially with opposite aileron to keep it level.  The airplane will actually climb AND accelerate with full rudder deflection and opposite aileron!  It does not decelerate at idle in a glide with these surfaces deflected the way other airplanes will.  

With two props, we should see twice as much prop drag when at idle and it doesn't feel like this is happening. Not sure if its modeled into any of the FM's yet, however.

This airplane is the king of STOL!  A clean light config will allow no flap/no wep liftoffs before the first runway intersection.  Fully loaded with 2000lbs of bombs and 10 rockets, its possible to lift off with no flaps/no wep before the second runway intersection.

The guns have a definate vertical convergence  with the 20mm shells dropping down rapidly below the .50's once past the convergence point.

The centerline pack of four .50's offers the ability to routinely obtain 800yard+ concentrated hits since there is no horizontal convergence.  Received a tail shot and damage (engine out) at d1.1 from a -38 that fired an 15+ second spray and pray volley.  (Don't these sim guns melt?   ) Head on shots are a breeze even at max range.  

Questions that I have for Pyro/Nate/HiTech:

Does a disabled engine automatically feather the prop?

Is it possible to make the prop spinners rounder to prevent their incessant blinking?

How is damage to the exposed turbo-superchargers modeled?  Being on the top of the booms, they seem very susceptable to damage from all but underside shots.

MiG

Offline Westy

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Couple of Early P-38 FM Observations
« Reply #14 on: March 02, 2000, 06:07:00 PM »
"Is it possible to make the prop spinners rounder to prevent their incessant blinking?"

 I'm glad someone mentioned that.    The other stuff too - for the most part already had been mentioned in other posts. But this one item bugged me to no end looking out of the cockpit last night.

-Westy