ALT HOLD causes climb

[n4646r]

We've installed a Digiflight II (the original base-level version, not the G or VS model) in a newly-built RV-8, and when you engage the ALT HOLD, the plane starts climbing briskly after about a 3 or 4 second delay.

The wiring harness was provided by Stein Air, so I'm presuming it is wired correctly based on their reputation.

I'm pretty sure the pitot and static line connections to the unit are connected properly and not reversed. Looking at the back of the autopilot unit, the pitot is on the left and the static is on the right.. correct?

The pitot and static plumbing are the usual 1/4" green and white plastic lines and SafeAir1 plug-in fittings and T-connectors that everyone uses on their RV's. A Dynon D100 is also plumbed in, and it indicates airspeed and altitude in-flight accurately.

The Digiflight-II was purchased new a few years ago when the RV project was first begun, and has sat unused until now that the plane is finally flying.

--Neal

[TrutrakTech]

Check the servo direction. You'll most likely find it's running backwards. Engage the alt hold on the ground and lift the tail of the aircraft. The elevator should move up with the tail. If it moves down, the servo is backwards. The installation manual has an explanation in the wiring diagram on how to reverse the direction. You simply add or cut a jumper between pins 1 and 2 on the back of the controller. Thanks!

[n4646r]

Thank's Lucas, I read your response over on the VAF forums a couple hours ago.

Since we've got the Stein Air wiring harness, I'll try clipping the yellow wire loop that sticks out of the back of the DB-25 connector for pitch reversal and see how it goes.