posted 07-20- 06:13 AM               

change of trim:

undercarriage down - Nose down
flaps down - initially nose up, finally no change
flaps up - strongly nose down

Why were we trying to get it to go nose down when flaps were lowered? I forget.

TS

posted 07-20- 07:10 AM               

But, in my Citabria, I have a kind of Fowler flap and the plane pitch up (able to make a loop without elevator input!!!)

Closterman http://www.ckm9.com/moustic

posted 07-20- 02:26 PM               

My R/C spit pitch down with flap down,
but for the real Spit I don't know.

Anyone know a real Spitfire pilot???

posted 07-20- 02:35 PM               

Just my .02.

posted 07-20- 02:35 PM               

On top of the new camber line, you have a bunch of drag hanging down below the airfoil, but there again, it depends on the type of flap used.

My guess on the Spit would be that there's a bunch of built-in pitch damping, and the wash-in of the tips would help.

Incidentally, since this isn't modelled quite right, we don't get much adverse yaw, either.

(this opinion subject to change without notice.)

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Pang 33rd~GS
33rd Strike Group

posted 07-21- 01:46 AM               

If a plane were to be prone to pitching up when flaps were extended, that could be VERY dangerous on a slow, critical AoA approach for landing.

posted 07-21- 04:25 PM            

I was flying the Lancaster last night (havnt flown it much btw) and was decending full speed for landing. When I dropped the flaps the nose pitched up real hard and in fact I could not bring it down, even with full forward stick until speed dropped off dramaticlly. I ended up over shooting the runway on the initial approach.

I know this has nothing to do with your question, but thought I would mention it.

posted 07-21- 08:40 PM               

Here's a quote from my favorite aeronautical reference page, "See how it flys" which explains this much better than I did.

quote:

---

Now let's consider the effect of flaps. As discussed in section 2.4 and section 12.7.1, there are four fundamental effects:

1.
Extending the flaps gives the wing section a shape that is more resistant to stalling. It can fly at a higher angle of attack9 without stalling. It can produce a higher coefficient of lift, perhaps as high as 2.5, whereas the same wing without flaps would stall before its coefficient of lift got higher than 1.3 or thereabouts.
2.
Extending the flaps increases the wing section's angle of incidence. You have, in effect, rotated the wing by a few degrees. Its leading edge is in the same place, but its trailing edge is lower, relative to the rest of the plane.
3.
Extending the flaps effectively increases the washout, since on most planes the inboard sections have flaps while the outboard sections do not.
4.
Extending the flaps increases drag. This is helpful during landing, but unhelpful during climb and cruise. It is not relevant to the subject of this chapter.
It turns out that the second effect is in some sense larger than the first effect. This has important and rather surprising consequences. Consider the typical situation where flaps are installed only on part of each wing. When flaps are extended, the affected part of the wing is flying at a higher angle of incidence, and therefore a higher angle of attack, compared to the unflapped part of the wing. Therefore the flapped section will stall sooner!

I know this sounds paradoxical, but it is 100% true: even though the flapped section has a shape that is intrinsically more stall resistant, it will stall before the unflapped section does.

This stalling behavior is actually quite useful. Remember that to get good low-speed handling, we want the wing-roots to stall first, to ensure we don't run out of roll damping before we run out of vertical damping. Therefore designers typically install flaps only on the inboard part of the wings.

Another useful side-effect is this: If you extend the flaps (increasing the angle of incidence), to maintain the same angle of attack requires a lower pitch attitude. This improves your ability to see over the nose.

Of course, the primary effect of the flaps remains: the wing section with flaps produces much more lift than it could without flaps.

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This is why I can't understand why the Spit would pitch nose-up, but then again, the Spit was not a general aviation type plane, so I'm not being dogmatic about it. Still interested to get to the bottom of this with the Spit, but I'm relatively comfortable sticking with my earlier assertion that the planes should nose down with flaps out.

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Pang 33rd~GS
33rd Strike Group