Trim your model

14th August 2015 | by Geoff White

TRIM FEATURE

MANOEUVERS

OBSERVATIONS

CORRECTIONS

CONTROL CENTRING

Fly general circles and random manoeuvers

Try for hands off straight and level flight.

Readjust linkages so that Tx trims are centred

CONTROL THROWS

Random manoeuvers

A: Too sensitive, jerky controls.

B: Not sufficient control.

If A; change linkages to reduce throws.

If B; increase throws.

ENGINE THRUST ANGLE

From straight flight, chop throttle quickly.

A: Aircraft continues level path for a short distance.

B: Plane pitches nose up.

C: Plane pitches nose down.

If A; trim is OK.

If B; decrease downthrust.

If C; increase downthrust.

CENTRE OF GRAVITY LONGITUDINAL BALANCE

From level flight roll to 45 degree bank and neutralise controls.

A: Continues in bank for moderate distance.

B: Nose pitches up.

C: Nose drops.

If A; trim is good.

If B; add nose weight.

If C; reduce nose weight.

YAW

Into wind, do open loops, using only  elevator.

Repeat tests doing outside loops from inverted entry.

A: Wings are level throughout.

B: Yaws to right in both inside and outside loops.

C: Yaws to left in both.

D: Yaws right on inside and left on outside.

E: Yaws left on inside and right on outsides.

If A; trim is correct.

If B; add left rudder trim.

If C; add right rudder trim.

If D; add left aileron trim.

If  E; add right aileron trim.

LATERAL BALANCE

Into wind do tight inside loops.

A: Wings are level and plane falls to either side randomly.

B: Falls off to left in loops, worsens as loops tighten.

C: Falls off to right in loops, worsens as loops tighten.

If A; trim is correct.

If B; add weight to right wingtip.

If C; add weight to left wingtip.

AILERON RIGGING

With wings level, pull to vertical climb and neutralise controls.

A: Climb continues along same path.

B: Nose tends to go to inside loop.

C: Nose tends to got to outside loop.

If A; trim is correct.

If B; raise both ailerons very slightly.

If C; lower both ailerons very slightly.

1. Engine thrust angle and C.G. interact. Check both.

2. Yaw and lateral balance produce similar symptoms. Note that fin may be crooked.

3. Right and left references are from the planes vantage point.

 

 

Trim your model
 
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