Elevator trim: Difference between revisions

Revision as of 07:29, 22 May 2024

Electric Trim

The Bearhawk uses a cable-operated trim system that actuates full-servoing trim tabs on each elevator. In my experience, the system is overly sensitive and awkward to use. I will never understand why the designer didn't opt for a flying tail type trim like a Skywagon or Super Cub.

In coordination with a fellow builder, I've opted to change to an electric trim that actuates the same trim tabs, but non-servoing. This changes to feel to something more like a standard 172. It adds an electric trim servo to each elevator.

A simple bracket to which to mount the electric trim servo on the underside of the elevator. Composite blister style fairing will cover the recessed servo. A push rod will emerge through a slot in the fairing and attach to the control horn on the trim tab.

ECU for trim

Per @akschu, using the Rugged MEGA-ET. This is an extended temp range model with better more rugged specs than the Arduino equivalent.

Bristol SG servo integrated position sensor can be read by its I/O pins.

For driving the servo motors with the MEGA, a motor driver sub board is required: https://www.pololu.com/product/2519

Notes for handling input

https://www.arduino.cc/en/pmwiki.php?n=Tutorial/AnalogInput

@@ Line 1: / Line 1: @@
-Addition of a simple bracket to which to mount the electric trim servo on the underside of the elevator. Composite blister style fairing will cover the recessed servo. A push rod will emerge through a slot in the fairing and attach to the control horn on the trim tab.
+== Electric Trim ==
+The Bearhawk uses a cable-operated trim system that actuates full-servoing trim tabs on each elevator. In my experience, the system is overly sensitive and awkward to use. I will never understand why the designer didn't opt for a flying tail type trim like a Skywagon or Super Cub.
+In coordination with a fellow builder, I've opted to change to an electric trim that actuates the same trim tabs, but non-servoing. This changes to feel to something more like a standard 172. It adds an electric trim servo to each elevator.
+A simple bracket to which to mount the electric trim servo on the underside of the elevator. Composite blister style fairing will cover the recessed servo. A push rod will emerge through a slot in the fairing and attach to the control horn on the trim tab.
 [[File:Servo mount.jpg|1280px|frameless]]