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flaming_onion
12-11-2006, 05:46 PM
This is probably old hat to a lot of you, but why does the P39 flat-spin so easily? Is it to do with the placement of the engine - I'm guessing that aircraft with conventionally front-mounted engines would be more inclined to stay nose-down in a spin.<div class="ev_tpc_signature">



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flaming_onion
12-11-2006, 05:46 PM
This is probably old hat to a lot of you, but why does the P39 flat-spin so easily? Is it to do with the placement of the engine - I'm guessing that aircraft with conventionally front-mounted engines would be more inclined to stay nose-down in a spin.<div class="ev_tpc_signature">



"Hey Andrei, hold my vodka and watch this!"

VW-IceFire
12-11-2006, 07:16 PM
Right on the money...because the engine is mounted centrally the P-39 has a very unusual and dangerous stall and spin characteristic that was never completely solved on the real life aircraft. This has to do with the center of gravity being placed near the center of the aircraft instead of in the nose. Most of the more stable aircraft are nose heavy.

This does give it one advantage in that its apparently made more maneuverable by having the COG placed in this area as its less stable. Akin to the F-16 or F-22 being unstable designs by nature (without computer control they would be near impossible to fly).<div class="ev_tpc_signature">

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IAF_Phantom
12-13-2006, 01:50 AM
about the stalls/spins, there is a procedure that if you execute it fast enough can minimize the recovery time from the spin.
you can find it here: http://www.airwarfare.com/Sims/FB/fb_p39.htm

Freelancer-1
12-13-2006, 08:11 PM
Once you are in a flat spin you have all kinds of time to try different things. Rate of decent is veeery slow. So try different things, by all means. But in the end you will bail 99% of the time.

Just make sure you bail by 1000 meters, cause it take takes forever to wiggle out of the cockpit and this is faithfully reproduced in game http://forums.ubi.com/images/smilies/16x16_smiley-wink.gif<div class="ev_tpc_signature">

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NonWonderDog
12-13-2006, 10:45 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by VW-IceFire:
Akin to the F-16 or F-22 being unstable designs by nature (without computer control they would be near impossible to fly). </div></BLOCKQUOTE>
It's not just "near impossible." If the F-16's quadruple-redundant flight computers suddenly stopped working at high subsonic speed, the plane would literally fall apart. Any small pitch up would quickly become a 20G+ backflip without superhuman reflexes on the pilot's part, knocking the pilot unconscious and shearing the wings off.

The P-39 isn't comparable. As far as I know it's not any less stable than any other WWII fighter as long as you keep it within normal pitch and yaw limits. If you pull the stick back and let go, the plane still pitches back down (the F-16 would continue pitching up faster and faster without the computers!).

The P-39 does have low moments of inertia about the pitch and yaw axes, however. The low pitch inertia is good; it gives you fast pitch response. The low yaw inertia isn't really helpful, though; it mainly just makes the plane spin more easily. I don't know enough about it to say why it's so impossible to recover from a spin, but I'd guess it has more to do with the aerodynamics than the engine position.

Platypus_1.JaVA
12-14-2006, 09:08 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by flaming_onion:
This is probably old hat to a lot of you, but why does the P39 flat-spin so easily? Is it to do with the placement of the engine - I'm guessing that aircraft with conventionally front-mounted engines would be more inclined to stay nose-down in a spin. </div></BLOCKQUOTE>

Hehe, You think the 4.0X P-39 is bad? You should pick up a copy of the original Il-2 Sturmovik (version 1.0) and give it a try http://forums.ubi.com/images/smilies/winky.gif They have been making this aircraft easier and easier ever since. It is quite enjoyable at the moment to fly. I found the early mustang's spin behaviour a bit of a nasty surprise actually.

But to be serious again, I fully support the P-39 stall and spin recovery tricks that are described in the allread mentioned airwarfae.com link.<div class="ev_tpc_signature">

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IL2-chuter
12-14-2006, 10:33 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">The P-39 does have low moments of inertia about the pitch and yaw axes, however. The low pitch inertia is good; it gives you fast pitch response. The low yaw inertia isn't really helpful, though; it mainly just makes the plane spin more easily. I don't know enough about it to say why it's so impossible to recover from a spin, but I'd guess it has more to do with the aerodynamics than the engine position. </div></BLOCKQUOTE>


That pretty much says it. The CG itself is really no different than other Army planes of the era BUT the polar moment is way low. If you kept the plane from yawing near stall (made more difficult because of the low inertia) you could easily avoid spins in a -39. This game doesn't give any aircraft the possibility of a normal straight ahead (coordinated) stall (you are always struggling against a dropping wing), however, so the 'cobra is a bit at a disadvantage out of the box.

As far as recovery - all game aircraft suffer there. For some reason they all seem to suddenly have a destabilizing aft CG shift at stall (feels like falling on their asses).


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3.JG51_BigBear
12-14-2006, 01:13 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Platypus_1.JaVA:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by flaming_onion:
This is probably old hat to a lot of you, but why does the P39 flat-spin so easily? Is it to do with the placement of the engine - I'm guessing that aircraft with conventionally front-mounted engines would be more inclined to stay nose-down in a spin. </div></BLOCKQUOTE>

Hehe, You think the 4.0X P-39 is bad? You should pick up a copy of the original Il-2 Sturmovik (version 1.0) and give it a try http://forums.ubi.com/images/smilies/winky.gif They have been making this aircraft easier and easier ever since. It is quite enjoyable at the moment to fly. I found the early mustang's spin behaviour a bit of a nasty surprise actually.

But to be serious again, I fully support the P-39 stall and spin recovery tricks that are described in the allread mentioned airwarfae.com link. </div></BLOCKQUOTE>

It was down right treacherous to fly the P-39 in the original Il2. It was all I could do to keep that thing in the air while the original AI flew rings around me and picked me off with incrediably unbelievable snap shots.

I loved the original Il2. http://forums.ubi.com/images/smilies/16x16_smiley-very-happy.gif