woensdag 11 mei 2011

Trim your RC aircraft

To begin with an overview of the available airplane control surfaces that need to be trimmed to get a proper level flight without any stick input:

If you trim make sure to get several mistakes high and trim for a normal level flight with for instance 50% throttle to begin with. If you have a programmable radio you can trim other scenario's also like slow speed etc. But changing throttle will absolutely change effect of all controls so it's important to keep that steady.

Another tip for beginners is to make sure that all controls are centered on both the radio (check trim buttons!) and the model before you fly.

This is a clear list on how to trim your airplane.

Control CenteringFly general circles and random 
Try for hands off, straight 
and level flight.
Readjust linkages so Tx 
trims are centered.
Control ThrowsRandom maneuvers.A. Too sensitive. 
B. Insufficient control.
A. Change linkage to 
reduce throws. 
B. Change linkage to 
increase throws.
Engine Thrust Angle1. From fast straight flight, cut throttle. 
2. With throttle on, pull to vertical flight.
1A. Aircraft continues straight flight for a short distance. 
1B. Plane pitches nose up. 
1C. Plane pitches nose down.
2A. Plane tends to yaw right
2B. Plane tends to yaw left
1A. Thrust angle is OK. 
1B. Decrease downthrust. 
1C. Increase downthrust.
2A. Add leftthrust.
2B. Add rightthrust.
Center of Gravity 
Longitudinal Balance
From level flight at low throttle and in trim, push the nose to 45 dive and neutralize controls.A. Plane continues in dive for  a short distance, and gradually pulls out. 
B. Nose pitches up abruptly. 
C. Nose pitches down more (tucks under). 
A. CG is good. 
B. Add nose weight.
C. Remove nose weight.
Split Elevators 
Yaw and CG
Into wind, Pull open loops using only elevator. Repeat test with outside loops to inverted entry.A. Wings are level throughout. 
B. Plane tends to left when right side up, and to right when inverted. 
C. Planes tends toward right when right side up and left when inverted. 
D. Plane goes left, right side up and inverted. 
E. Plane goes right, right side up and inverted. 
A. Trim is fine. 
B. Add right rudder, or weight to right wing. 
C. Add left rudder, or weight to left wing. 
D. Raise right half of elevator, or lower left half of elevator. 
E. Raise left half of elevator, or lower right half of elevator.
Yaw2Into wind, do open loops, using only elevator. Repeat tests using 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 inside and outside loops. 
D. Yaws to  right on inside loops, and left on outside loops. 
E. Yaws to left on inside loops, and right on outside loops.
A. Trim is correct. 
B. Add left rudder trim. 
C. Add right rudder trim. 
D. Add left aileron trim. 
E. Add right aileron trim.
Lateral BalanceInto wind, do tight inside loops, or pull to straight up flight into hammerheads. Repeat test from inverted entry.A. Wings stay level and plane falls randomly in each direction from hammerheads. 
B. Falls off to left from both inside and outside loops. 
C. Falls off to right in both inside and outside loops. 
D. Falls off in opposite directions on inside and outside loops.
A. Trim is correct. 
B. Add weight to right wing. 
C. Add weight to left wing. 
D. Change Aileron trim.
Aileron Rigging.With wings level, pull to vertical  climb , and neutralize controls.A. Climb continues same path.
B. Nose tends to go to inside loop.
C. Nose tends to go to outside loop.
A. Trim is correct.
B. Raise both ailerons slightly.
C. Lower both ailerons slightly.
Wing IncidenceKnife edge flight.A. Plane tends to nose up position (as if up elevator is applied).
B. Plane tends to nose down position (as if down elevator is applied). 
A. Reduce wing incidence.
B. Increase wing incidence.
Aileron Differential.With wings level, roll repeatedly left or right.A. Model stays on heading.
B. Model yaws in direction of roll (barrel roll).
C. Model yaws opposite the direction of roll.
A. Aileron Differential is correct.
B. Too little differential (reduce down throw).
C. Too much differential (increase down throw).

source: http://www.scootworks.com/rdrc/trim.html

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