J430 1st flight imbalance
Topic starter 14/08/2020 11:17 pm
I have just achieved the first test flight of my J430 and the test pilot reports some control issues which I’m seeking advice on.
Pilot reports as follows;
Significant right aileron and right rudder required to fly straight and level, also significant down elevator and full down trim required to hold pitch attitude.
Worst in full power climb @ 80 kts., less in cruise @2600rpm, 100 kts. and least in landing approach low power, full flap 70 kts.
The aircraft weight was 510 kg. approx. (empty weight 391 kg. + pilot 86 kg. + 46 litres fuel ) and cg position 131.3mm aft. of datum. i.e light with fairly fwd cg.
Careful measurement of the aircraft showed:
Stbd. wing average at a number of stations spanwise + 0.35o approx. incidence relative to port wing.
Thrustline 1.2o nose up relative to fuselage datum.
Some nose down twist in stbd. tailplane root to tip of approx. 2o.
I understand that I can correct the wing incidence problem by using eccentric bushes where necessary in the starboard root joint. There is one already fitted in the port aft joint but I think the setting of it currently does not give much scope for solving the problem. I have some spares of the bushes, 5/8’’ UNC (11tpi) external thread, drilled 1/4’’, 0.1’’ offset, 10mm thick.
Speaking to the Jabiru UK agent Skycraft, they inform me that thrustline adjustment can be made by removing the thick countersunk washers (part no. 4214934) on the aft side of the lower engine mount rubber doughnuts. Is it possible also to reposition the washers on the upper mounts to the rear of the doughnuts?
I can’t do anything about the tailplane twist except the small reduction achieved in longitudinal dihedral by reducing stbd wing incidence.
What is the standard wing setting angle, say lower surface tangent to fuselage horizontal datum? Also what is the standard tailplane chord setting angle to fuse datum?
Any advice gratefully received.