Author Topic: P40C flaps do not create lift anymore...  (Read 1052 times)

Offline -aper-

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P40C flaps do not create lift anymore...
« on: January 18, 2012, 05:32:43 AM »
Well trimmed P40 goes nose down after deploying flaps while all the other planes go nose up and gain alt in this situation. Is something wrong with P40s flaps modeling ?

Offline wells

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Re: P40C flaps do not create lift anymore...
« Reply #1 on: January 18, 2012, 06:47:16 AM »
That doesn't necessarily mean that they don't add lift.  They are just pitching the nose down, like changing the elevator trim.  Whether the nose goes up or down depends on many things.  Normally, the flaps by themselves will pitch the nose down, if the CG isn't too far aft of the 1/4 chord.  Then, the increased downwash behind the wing will tend to pitch the nose up, when it hits the stabilizer.  The two things work against one another.  If the stabilizer is of small area or aspect ratio and/or the flaps are large, the nose will likely go down.  If the opposite is true, the nose will go up.  In each case, the flaps are still adding lift.  You should be able to fly slower before stalling.

Offline FLS

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Re: P40C flaps do not create lift anymore...
« Reply #2 on: January 18, 2012, 06:48:40 AM »
I don't recall offhand what the P-40 is supposed to do but it's normal for flap extension to pitch the nose up or down depending on the aircraft and the degree of extension. AH aircraft generally pitch up so this may be a step forward in the flight modeling.

Offline SmokinLoon

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Re: P40C flaps do not create lift anymore...
« Reply #3 on: January 18, 2012, 08:38:53 AM »
I don't recall offhand what the P-40 is supposed to do but it's normal for flap extension to pitch the nose up or down depending on the aircraft and the degree of extension. AH aircraft generally pitch up so this may be a step forward in the flight modeling.

I was thinking the same thing.  With "up" pressure on the under-side back of the wing isnt that going to push the nose down?  I've not really paid much attention to it, I'll go test it out for myself.
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Offline hitech

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Re: P40C flaps do not create lift anymore...
« Reply #4 on: January 19, 2012, 11:53:24 AM »
You also have a drag moment arm pitching the aircraft.

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Offline Krusty

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Re: P40C flaps do not create lift anymore...
« Reply #5 on: January 19, 2012, 02:25:53 PM »
The question is: Should it be the same for all P-40 models? Or does the unique nose and aerodynamics of the early "C" model set it apart from its later brothers? Maybe it's just the nature of this plane vs its later models.

Offline Tupac

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Re: P40C flaps do not create lift anymore...
« Reply #6 on: January 19, 2012, 02:51:27 PM »
I'd imagine it would also depend on how fast you are going. Dropping flaps at 120 you are alot less likely to ballon than if you dropped them at 200
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Offline Pyro

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Re: P40C flaps do not create lift anymore...
« Reply #7 on: January 19, 2012, 03:27:30 PM »
It's something that got fixed in the remodel of the P-40s.  The P-40 pilot's manual states that there is no appreciable change in pitch trim when the flaps are lowered.  I see only the slightest downward change in trim on the P-40C.  It definitely should not be giving you the strong nose up pitch trim that it used to do.  That doesn't mean they aren't doing anything.

Offline colmbo

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Re: P40C flaps do not create lift anymore...
« Reply #8 on: January 19, 2012, 05:15:41 PM »
I'd imagine it would also depend on how fast you are going.

Speed makes a huge difference.
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Offline hitech

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Re: P40C flaps do not create lift anymore...
« Reply #9 on: January 20, 2012, 02:09:44 PM »
The question is: Should it be the same for all P-40 models? Or does the unique nose and aerodynamics of the early "C" model set it apart from its later brothers? Maybe it's just the nature of this plane vs its later models.

There should not be any appreciable difference between the p-40's the numbers are the same, but weight and power settings could create a small difference between them.

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