These tests assume that the plane has been built perfectly aligned, wings square to fuse, stab in line with wings, vertical fin is exactly 90 deg. to horizontal stab. Rudder is perfectly aligned with fin chord-line. Wings are not warped (checked with an incidence meter) or bowed, ailerons are perfectly aligned with the chord line of the wing airfoil and elevator halves are aligned with the stab chord line. Both ailerons and both elevators have identical travels and "track" (matched movement throughout their entire travel range) when measured. Engine thrust, wing and stab incidence, and balance (CG) is set per the designer/ manufacturer's recommendations.
FLIGHT tests should be done in near calm conditions, as ANY wind can dramatically effect various observations. Double check each of the following tests before making any changes. (If you have a capable helper, have him perform the SAME tests, before you change anything!)
There is not a more critical component of aircraft trim setup than PROPER Center-of-Gravity!!!! It MUST be correct, and is ONLY correct on a given wing/model design for a particular weight.
These tests are listed in the recommended order for best results.
|
|
Procedure |
Results |
Adjustments |
| Control Neutrals | Response to centering each control stick | Adjust trims for straight & level flight | Adjust clevises to center transmitter trims |
| Control Throws | Apply YOUR preferred stick deflection to each control | Check for response of each to suit YOUR desired rate | Change control horns, ATV, and Dual Rates as needed |
| Center of Gravity | Roll into nearly-vertical banked turn (at least 60 deg.) | A. Nose Drops
B. Tail Drops |
A. Add tail weight
B. Add Nose weight |
| Up/ Down Thrust, #1 | Straight & Level [90 deg to any wind] at NORMAL cruise speed then
cut throttle.
NOTE: EITHER change B or C requires retest of Decalage and Verticals |
A. Model continues level flight with a gradual drop
B. Model abruptly dives C. Model abruptly climbs |
A. No Change
B. Remove UP thrust (or add DOWN)
C. Add UP thrust (or remove DOWN) |
| Up/Down Thrust, #2 | Straight & level, then pull up [90 deg to any wind] sharply at
NORMAL cruise speed to vertical; neutralize elevator
NOTE: EITHER change B or C requires retest of Decalage and Verticals |
A. Model continues straight up
B. Model goes to canopy C. Model goes to belly |
A. No Adjustment
B. Add down thrust C. Reduce down thrust |
| Decalage, Angle of Incidence | Power off vertical dive [90 deg to any wind] from high altitude (NEUTRALIZE elevator); see NOTE: at bottom. |
A. Model continues straight down B. Model goes to canopy C. Model goes to belly |
A. No change needed B. INCREASE wing incidence C. REDUCE wing incidence |
| Knife Edge Pitch | Normal Cruise speed pass; roll to knife edge, left and right, use
rudder to hold model level.
NOTE: EITHER change in B or C requires retest of Decalage and Verticals |
A. Model does not change pitch
B. Model pitches to canopy C. Model pitches to belly |
A. No adjustment needed
B. Either move CG aft; or increase wing incidence; or mix down elevator with rudder C. Reverse of "B" |
| Tip Weight - Test1 | Straight & level, normal cruise speed, roll inverted, release aileron stick | A. Model does not drop a wing
B. Left wing drops C. Right wing drops |
A. No adjustment
B. Add weight to right tip C. Add weight to left tip |
| Tip Weight - Test 2 | Fly model directly into any wind toward you or away from you; Pull tight inside loop, repeat with outside loop (be certain rudder trim is correct, and that NO aileron stick is inputted!) | A. Model comes out with wings level
B.Model comes out with right wing low C. Model comes out with left wing low |
A. No adjustment
B. Add weight to left tip
C. Add weight to right tip |
| Side Thrust | Fly model away from you INTO any wind; Pull to straight vertical
at normal cruise speed. DO NOT use rudder.
NOTE: Rudder trim offset (if any) will cause IMMEDIATE yaw after radius. Thrust problems will be obvious later in the line...and are usually more subtle. |
A. Model continues straight up
B. Model yaws left AFTER line established C. Model yaws right AFTER line established |
A. No Adjustment
B. Add right thrust C. Reduce Right thrust |
| Aileron Differential | Fly model toward you; pull to vertical; neutralize controls,
half roll.
NO ELEVATOR/RUDDER during the ROLL!!!. |
A. No Heading Changes
B. Heading change opposite to roll command C. Heading change in direction of roll command |
A. Differential settings OK
B. Increase differential C. Decrease differential |
| Dihedral | Normal cruise pass, roll to knife edge, left and right, use rudder to hold model level | A. Model does not roll
B. Model rolls indirection of rudder C. Model rolls opposite to rudder |
A. Dihedral OK
B. Reduce dihedral C. Increase dihedral |
|
NOTE - This portion of the trimming chart may be unclear for the following reason: In order to maintain UPRIGHT level flight, the wing of a plane with a symmetrical airfoil wing needs to have a positive Angle of Attack (AOA) usually less than 1 degree. This positive angle provides the lift required to cause the plane to fly level. This angle is established by the shape of the airfoil, and the weight it must lift. A plane balanced slightly nose heavy (for pitch stability) will require slight up elevator trim for level flight. A plane trimmed in this manner will have a tendency to pull to the canopy on a straight, controls neutral, down line because the elevator is controlling the AOA of the wing. This positive AOA may ALSO be achieved by positive incidence change which requires down elevator trim to achieve level flight. Thus, a power-off down line should fall straight down with the controls neutralized. There are significant interactions between wing incidence changes and CG, therefore, it is most important that the CG of the airplane be established first. A zero/zero/zero, wing/elevator/thrust angle (decalage) will need MORE up elevator trim for level flight. This will exaggerate the canopy pitch on down vertical lines. Flight trimming an airplane is YOUR "personal preference" after the basic essential items are set. |
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