Supertrim

Mike Shellim 21 Jan 2022

'Supertrim' is a simplified user interface for adjusting pitch trim on models with crow brakes. While not as flexible as Crow aware trim, Supertrim has the benefit of not requiring a Lua script.

Why Supertrim?

Traditionally, the UI for adjusting pitch trim consists of (a) an elevator trim and (b) a separate adjustment for crow compensation. However, it's error prone since the pilot has to decide which adjuster to use.

With Supertrim, the elevator trim changes function according to the crow brakes:

This way, only one adjuster is used, resulting in a safer, more intuitive user interface.

Requirements

In order to implement Supertrim, the following are required.

The code

Supertrim depends on a neat feature of OpenTX, whereby a trim can be repurposed in real time to update a GVAR.

All that's needed is for the GVAR to be the weight of the compensation mix, and for the trim to be repurposed so that it updates the GV when the brakes are deployed.

In the code below:

Inputs

I2:Ele source=Ele Weight=100% -- elevator input

 

GVARS

GV1 - min=0%, max=40% -- stores compensation

 

CH2:elevator

+= Source=I2:Ele Weight=-100% -- elevator mix
+= Source=Thr Weight=+GV1 Offset=-GV1 CV=Comp -- compensation

 

Logical Switches

L1 Thr < 100 -- true when brakes deployed

 

Special Functions

SF1 L01 - Adjust GV1 Source=TrmE -- if L1, trim updates comp

For more info on the techniques used, see Advanced trims, in particular the section "Using a trim to update a GVAR".

Demo file

A demo can be dowloaded here (X9D profile). If using the Companion sim, dragging the trim handle doesn't work when adjusting compensation. Instead, click on the up/down arrowheads.

Integration in Pro templates

At the time of writing, Supertrim is integrated in the latest DLG, DLG6S and F3F templates. The plan is to include it future versions of the remaining templates, where applicable.