What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Expanded Scale for Pitch Trim Indicator

Piper J3

Well Known Member
Dynon and Van’s tell you to set the end points of the trim indicator so full travel trim is indicated at both ends of the scale. I have my trim indicator set to show only the portion of trim that is used in normal flight. This way the scale is expanded, more sensitive, and more useful.

The logic behind this is similar to an analog voltmeter which has selective scaling. Suppose you want to measure a car battery at 12 VDC. You wouldn’t choose a scale with 500-volt end point because it would not show enough resolution to determine measured voltage at the low end of such a large scale. It would be better to choose a scale of say 20 or 50 volts so a more accurate reading could be determined.

So, that’s what I did with my trim indicator. I have the end points set to show slightly more than what is used in normal flight. Cruise is about 1/8” above lower end and approach speed is about 1/8” from upper end. Where this really shows its worth is when slowing down in the pattern. I can be at full cruise speed on downwind leg and be slowed down to a stabilized hands-off approach speed of 63 mph (55 KIAS) before making the turn on to base leg. By knowing exactly where the trim indicator needs to end up I never under / over shoot the trim. You can sneak up on the predetermined trim value every time.




 
Perfect example of the innovators that many experimental aircraft owners are.
I think most pilots are fully adapted to setting trim based on feel though so probably don’t need high resolution in the display.
The only time I ever look at the trim indicator is to set it for take-off and high precision isn’t needed for that since the actual setting needed is slightly different for nearly every takeoff.
 
Last edited:
Back
Top