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I have my M20K Encore at the shop for a GFC500 install with pitch trim and yaw damper. Sounds like they've run into a hiccough regarding the yaw damper. This Encore came from the factory with an S-TEC yaw damper (see original W&B sheet below). I found a reference from AOPA mentioning “Except for the addition of an S-Tec yaw damper/rudder trim system — greatly appreciated in those long climbs to the flight levels, the Encore's flight control system is pretty much unchanged from the 252.” The avionics shop mentioned: Mooney with electric rudder trim with third party YD are to typically work as independent systems together in the flight regime. Your plane however was rigged somehow when the STEC was installed they removed the factory rudder trim motor and rigged the STEC YD trim pot to the rudder indicator assuming to replace the rudder trim system factory installed. STEC has no provision for this and you are now missing the original factory rudder trim motor and rocker switch. GFC500 goes into these Mooneys with rudder trim no problem and they remain separated systems that is why there are no special instructions in the installation for doing anything with the Mooney rudder trim. The issue still arises that the Garmin YD does not operate in this way and will not act as your rudder trim and your YD. We can discuss more tomorrow at the office but options right now are no electric trim or add the Mooney rudder trim motor and switch to the aircraft. Are there any Encore pilots out there with the GFC500 and yaw damper? How did you address this? Is it accurate that I'd need to reinstall a Mooney rudder trim motor in order to install the GFC500? Currently I have a rotary knob for rudder trim L/R and below that a 3 position switch for On/Auto/Off for yaw damper. Verified on old pictures, came from the factory with same. Thanks, Marc.

Avionics for sale: KFC150 autopilot $4995, Yaw Damper $1395, Shadin MiniFlow-L $795, KI256 AI $$795, Davtron 800 clock $145

I had an occasion to fly at 9500' yesterday to compare speed pre-yaw damper vs post-yaw damper. Pre-yaw damper, cruising just barely LOP at 9500' I would see 157 KTAS. If I remember right, fuel flow was about 9.0 to 9.3 GPH. That speed was calculated using our TAS indicator by aligning the OAT with altitude and reading the value. Yesterday I did the same thing. Fuel flow yesterday was 9.1 GPH. Using the airspeed indicator I got 160 KTAS. Using the TAS calculator utility on the GTN650 I got 161 KTAS. So it appears that the yaw damper is about a 3 - 4 knot speed mod.