Author Topic: Jumpin on the P-38 bandwagon (Read 7166 times)

Tac · « **Reply #30 on:** November 28, 2001, 04:40:00 PM »

Read above sundog. AH dive flaps only do half of what they should do.

The dive flaps had TWO distinct effects depending at what point they are deployed.

If the dive flaps were deployed before the dive or before the plane reached a high speed (above 350?) it would prevent the "tuck under" effect and allow the pilot to pull the nose up, albeit slowly. This the AH dive flaps do (although trimming elevator up pulls nose twice as fast... odd).

If the dive flaps were deployed after the plane compressed it would pull the nose up all by itself, at about 3 to 4 g's. Test pilots even said that if left alone, with no input from the pilot, they would pull a neat loop by itself. In combat, the 38 using the dive flaps after compression was able to recover from a high speed dive and pull out VERY quickly... something the german fighters couldn't follow...and many augered.

This last effect, the most important effect, is not present in AH.

This is part of the 5-meg info I sent Pyro some time ago. Its a page from Hangar Flying, a magazine issued to P-38 pilots during the war, written by the test pilots back in the states to inform deployed pilots of the capabilities of the plane and the what-nots. This page says part of the info on the dive flaps, specifically on the part that's absent in AH.

[ 11-28-2001: Message edited by: Tac ]

funkedup · « **Reply #31 on:** November 28, 2001, 04:48:00 PM »

Tac if the plane has the dive flaps down with a given altitude, airspeed, attitude, angle of attack, and power setting, it shouldn't make a bit of difference whether the flaps were deployed before or after the dive was started. To make a plane that behaves like you say, HTC would have to violate the laws of physics that govern the flight model.

The only explanation is that in the first of the two cases you describe, the pilots had trimmed the plane for the dive.

[ 11-28-2001: Message edited by: funkedup ]

Tac · « **Reply #32 on:** November 28, 2001, 04:57:00 PM »

Im no aeronatical enginerdeer funked, but I think the airflow change caused by the flaps being deployed at the speeds, along with the change of center of gravity cause that. Again, this is just my guess. All I know is that it happened.

See the pic above. I cant resize it without becoming illegible.

Swager · « **Reply #33 on:** November 28, 2001, 04:58:00 PM »

The 38 is fine the way it is. If it does get so-called "fixed", what are ya gona complain about then?

The guns are bad!

Dosen't turn good!

Wheels don't go around fast enough!

Canopy gets stuck!

Turbo-chargers dont activate at the right alt!

The wing tips are too fragile!!

The airspeed indicator is off .32% at 560mph!

I got a complaint! Pyro, yesterday my little 109F4 received a 6 second burst from a Mossie and my wing fell off! WTF! I thought the wing was more sturdy than that! Could you fix it??

Have a Nice Day!

Tac · « **Reply #34 on:** November 28, 2001, 05:01:00 PM »

And the hellfire tastes like saltwater! Damn these brit breweries!!!!!

funkedup · « **Reply #35 on:** November 28, 2001, 05:05:00 PM »

Thx for the pic Tac. It's quite legible for me. Nice job on research.

I still think it must have been trim. If you started with the flaps deployed you would probably trim the plane into the dive in that condition, and it would not pitch up as noticeably. If you started with flaps up and trimmed the plane into the dive in that condition, then you would notice a bigger change when you changed the configuration by popping the flaps out.

I'll try to test fly tonight, to see if what I say can be duplicated in AH.

[ 11-28-2001: Message edited by: funkedup ]

gripen · « **Reply #36 on:** November 28, 2001, 05:09:00 PM »

Tac,
Well, just take your P-38 manual and look compressebility table, at 30k the P-38 was limited to bit over 3g at any speed. The P-38 turned about as well as the P-47 at high altitude (above 20k) and the P-51 could out turn them both. At low altitude (below 10k) and at low speed (around 140mph IAS) the P-38 could out turn the P-51 with combat flaps.

Your dive flap information is also somewhat incomplete. The dive flaps gave about 3g automatic pull out at 10k but at 30k they gave just 1g.

gripen

Tac · « **Reply #37 on:** November 28, 2001, 05:28:00 PM »

Gripen, the 38 out-turns both when its fowlers are deployed. At what speed was your info taken?

"Well, just take your P-38 manual and look compressebility table, at 30k the P-38 was limited to bit over 3g at any speed"

compressibility and how many g's it can pull on level flight.. what's the relationship? I think that info may be incorrect. Wish Widewing was here.

"Your dive flap information is also somewhat incomplete. The dive flaps gave about 3g automatic pull out at 10k but at 30k they gave just 1g."

Again, at what speed? Where are you getting this info? If its true, then LW planes couldnt pull a single G at that alt when they followed a 38 on high speed dives. That mustve been nice, not blacking out when attacking bomber formations.. that sounds kinda odd dont you think?

[ 11-28-2001: Message edited by: Tac ]

gripen · « **Reply #38 on:** November 28, 2001, 05:48:00 PM »

Tac,
The compressebility table of the P-38 is actually the flight envelopes of the p-38, you can find similar stuff for the P-47 from Nikla's documents and the manual of the F4U-5 contains similar data for the F4U. There exists USAF test data about this, the P-51 out turned the P-38 at high altitude. And the reason for this was simply the better compressebility characters of the P-51, actually at high speeds the P-51 could even out turn the Spitfire at high altitude for this same reason.

About dive flaps I have test flight data, at 10k and at mach 0,67 the dive flaps gave about 3g and at 30k and mach 0,67 they gave 1,2g (centre of gravity was at aft limit).

gripen

funkedup · « **Reply #39 on:** November 28, 2001, 05:53:00 PM »

Gripen can you scan that flight test data? G vs. altitude at constant Mach would be interesting. I assume they fixed the yoke in the same position and used the same pitch trim setting for all tests? Or did they trim for 1g flight at each Mach/altitude combination? If that information is included then HTC would be able to quite accurately figure out the pitching moment coefficient for the dive flaps.

[ 11-28-2001: Message edited by: funkedup ]

Tac · « **Reply #40 on:** November 28, 2001, 06:05:00 PM »

Well, I find it odd. The 38 was only outperformed by the p51 at high speeds..at lower speed the 38 beat the crap outta the pony. Same for the jug.

Dunno. Just sounds odd to me.

gripen · « **Reply #41 on:** November 28, 2001, 06:07:00 PM »

funkedup,
I have no scanner but you can find this same data from the PRO (RAE TN Aero 1702) there is also some NACA documents in PDF format in their server which explain well how these devices worked (can't remember numbers now) IIRC I have claimed those documents in the usenet discussions with CC/Widewing (try coogle). IIRC there was an article in the Niklas's documents page which shows how effectivenes of the dive brakes decreased when altitude raised.

gripen

gripen · « **Reply #42 on:** November 28, 2001, 06:19:00 PM »

Tac,
Well, don't believe me. There exists a lot USAF, RAF, NACA and RAE test data about the P-38 around and if you put some effort on searching you can check all this yourself.

gripen

batdog · « **Reply #43 on:** November 29, 2001, 06:06:00 AM »

Quote

Originally posted by Pyro:
I've made some durability changes to the P-38 for the next patch.

WOOOOOOOOT WOOOOOOOOOOT WOOOOOOOOOOOT! Hell I thought the last patch changed it making it a tougher ride. Cool beans.

xBAT

bolillo_loco · « **Reply #44 on:** December 01, 2001, 10:10:00 PM »

I have no problem believing the P-51D out turned most planes (especially a P-38J/L) at airspeeds over 300+ mph IAS at any altitude, however considering the P-51D's power to weight ratio, especially at higher altitudes, it had to bleed speed quickly not? I could be wrong and I only offer questions and there seem to be some very knowledgable people and I enjoy the reading.

turning ability and climbing ablility at altitudes over 20,000ft. the P-38J/L had a lot better power to weight ratio at these altitudes than did the P-51D, isnt that important for bleeding speed? also what was the condition of the P-51D? The few tests I have seen where the P-51D/B are used always use a specially conditioned air frame and the rear tank empty and or removed from the P-51B/D making it light at take off while the other planes take off at full weight. So the tests that I have seen (and I have not seen them all) usually favor the P-51 series. Thanks guys and just curious I enjoy the reading like I said earlier.

[ 12-01-2001: Message edited by: bolillo_loco ]