I'm going to make an assumption, since I don't have any sources immediately available.

I will assume that the upper half acts as a dive brake/spoiler only - (activated with the / key)

I will assume that the lower half is both flap and spoiler (acts with F7-F8, and with / keys).

In that case, your problem is not with the upper flap, but with the lower.

Copy/paste the lower flap.  Name it "spoiler" (or as appropriate), tag it as a hierarchy part (no geometry created).  Make this lower "spoiler" part the parent of the lower flap part.

Your lower part will now work with the flap or spoiler keys.

(for goodness sake - do NOT operate both spoiler and flap keys unless you can add a preprocess to the flap part so that it doesn't operate when spoilers are on..)

Thanks very much Felix.  I got it to work according to your instructions.

The flap now has to be a key_flap, and the only problem I have is that when you apply the parent part, the flap runs away to some corner of the screen  --  but I am slowly getting used to it with undercarriage animation when the undercarriage is raked forward.

So? 

Make the lower spoiler part a child of your outer wing.  After all, you also have to make the ailerons children of the outer wing part....

Your hierarchy outline would be like:

- outer_wing
     -  lower spoiler
        -  A.1.1 flap
     -  aileron

So you lower spoiler and aileron are children of the outer wing, and the flap is a child of the lower spoiler.

Quote:



If you think that's complicated - wait until you start making your damage model and there's a split in the family. ...does the flap go with the aileron or will the spoiler slap the flap and go with the gear?