LX A-10 - trim issue

Yes Ralph, by reducing the incidence, I mean increase the negative. i.e. lower the LE or raise the TE. I'd do it in small steps, though, say half a degree at a time.

Given your description of the longitudinal stability, I would say that the contradictory characteristics I've described above may be due to: downwash of the wing over the tail, lift from the cockpit canopy, downwash effects from the engine nacelles and/or airflow induced by the fans over the tail (or the wing). Either way, it does sound as if you have a stable aircraft.

If you want to check for positive longitudinal stability before doing anything try the following:

- Speed up and slow down from trimmed level flight without touching the pitch control. If the model pitches up as you go faster and pitches down as you slow up, it's stable.

- Go into a turn from trimmed level flight with gradually increasing pitch (use roll to stop it ballooning). It the elevator up deflection is progressive, i.e. the aircraft doesn't pitch up on it's own, then it's stable.

- Disturb the aircraft from trimmed level flight with a sharp pitch input, then centralise the pitch control. If the aircraft returns to steady flight, it's stable.

If it does the opposite to what is described above, then it's unstable. Provided that the model describes stable characteristics, it should give you the confidence to proceed slowly with changes in either C of G and/or tailplane incidence. It's prudent to make only one change at a time!

Good luck and please keep us posted with what happens. The A10 is a model I've looked at very closely for FF ducted fan.... Watch this space for progress, but don't hold your breath....

I have made all the adjustments and test flown her. The best incidence turned out to be -5.5^o was -3^o. No other changes were made, CoG remains as previous.

She now flies hands off (probably better than with hands on!! :lol: ) with elevator inline with tailplane chord, i.e. neutral. No pitch change with and without power. 45^o climb out inverted needs a slight touch of down. Take off requires minimal up elevator she just lifts off perfectly no need to pull her off.

Superb! Thanks for the help I owe you all a beer. So happy.

Glad to hear it all work out Ralph, thanks for the report!
Happy Landings,
Andy

Seems like a case of "Ask and it will be given unto you " Ralph :woohoo: :woohoo:

We may not have the quantity of members, but we sure do have the quality . Well done folks

Garry