TECHNICAL SUPPORT
Published 2026-04-09
When an aircraft wing uses two separateservos to control the ailerons—one for the left aileron and one for the right—proper handling is critical for safe and predictable flight. This guide provides a complete, actionable approach to setting up, synchronizing, and troubleshooting dual aileronservos. You will learn how to identify common problems, correctservodirection mismatches, balance travel distances, and verify correct operation before flight. Every recommendation is based on standard remote control aviation practices, verified by field experience.
The two servos must move in opposite directions when you give an aileron stick command. For a right roll command: left aileron goes down, right aileron goes up. Any deviation—one servo lagging, moving too far, or moving in the wrong direction—causes dangerous roll instability.
Common real‑world case:A modeler installs two identical servos, plugs them into channels 1 (aileron) and 5 (aux1) on the receiver, but finds that both ailerons move up together when he applies right stick. This is a direction mismatch, the most frequent dual‑servo issue.
Action:On your transmitter, set up a dual‑aileron wing type (often labeled “Flaperon” or “Dual Aileron”). This automatically assigns one servo to channel 1 and the other to channel 6 (or an available channel).
Check direction:Move the aileron stick to the right.
Left aileron must godown.
Right aileron must goup.
If wrong:Reverse only the servo that moves incorrectly. Donotreverse both. Use the servo reverse function on the transmitter for that channel.
Critical verification:After reversing, test again with slow stick movements. Both surfaces should start and stop together. Any hesitation indicates a different problem (see step 3).
Even with correct electronic direction, mechanical errors cause asymmetry.
Servo arm position:With the transmitter sticks centered and trims at zero, remove the servo arms. Power on the system. Reinstall arms as close to 90° relative to the servo case as possible. Use the “sub‑trim” function (only a few clicks) to achieve perfect perpendicularity.
Pushrod length: Adjust clevises so that both ailerons are exactly neutral (flush with the wing’s trailing edge profile) when the servos are centered.
Common mistake: Using sub‑trim more than ±20 points. Large sub‑trim reduces total travel and causes unequal throw in each direction. If you need large sub‑trim,reposition the servo arm physically.
Even with identical servos, manufacturing tolerances create different total travels.
Method – using a throw meter or ruler:
Measure up travel of right aileron (in mm or degrees).
Measure down travel of left aileron (they should match the right’s up travel for balanced roll).
Adjust the “endpoint” or “travel adjust” for each channel independently until both surfaces achieve the same maximum deflection (e.g., 12mm up and 12mm down on each side).
If your transmitter supports “balance” or “curve” mixing: Use it to linearize the movement throughout the entire stick range, not just endpoints.
Real‑world example: A pilot notices the aircraft rolls faster to the right than to the left. Measurement reveals right aileron travels 15mm up, left aileron only 12mm down. After reducing right aileron endpoint to match 12mm, roll rates become equal.
Binding: Move the aileron stick fully and watch the pushrods. If any linkage binds (hits the servo case or wing structure), adjust the control horn position or use a different hole on the servo arm. Binding burns out servos and causes erratic movement.
Slop: Gently wiggle each aileron with your finger. If you feel free play before servo resistance, check for loose screws, worn clevises, or undersized pushrod holes. Replace any worn parts. Slop degrades precision and can cause flutter.
Power on the system. Have an assistant hold the aircraft.
Move the aileron stick slowly from left to right. Observe both ailerons: they should be mirror images.
Rapidly move the stick back and forth. Both servos must keep pace – no lag, no buzzing when centered.
Release the stick to neutral. Both ailerons must return to exactly the same neutral position every time. If one returns slightly off, re‑check sub‑trim and linkage friction.
Critical safety note: Never fly with mismatched dual aileron servos. Even a small difference (2mm of travel or 0.5° of neutral offset) causes unwanted roll coupling and makes the aircraft difficult to trim.
Core principle: A dual aileron servo system works correctly only when the two servos move in exact opposite directions with equal travel and simultaneous response. No brand‑specific “auto‑tune” feature replaces proper mechanical and radio setup.
Your immediate action plan:
1. Verify wing type is set to “dual aileron” on your transmitter.
2. Physically check that left aileron goes down when you command right roll. Reverse one servo if needed.
3. Center servos mechanically using arm position, not excessive sub‑trim.
4. Measure and match total up/down travel for both ailerons using endpoints.
5. Perform the mirror test and listen for binding or buzzing.
6. Before every flying session, repeat the quick check: move stick left/right and visually confirm both ailerons move symmetrically.
If you follow these six steps exactly, your dual aileron servos will provide reliable, coordinated roll control. For persistent asymmetry after this guide, inspect the servos themselves (swap them left‑right to isolate a faulty unit) or consult a local RC club instructor for hands‑on help.
Update Time：2026-04-09
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