Building, testing and operating an experimental aircraft

Fuel Injector Servo and Throttle

23 Dec 2014

Van’s ships an Avstar fuel injection servo with their firewall forward kit. I don’t know anything about that outfit, but it certainly seems to be a well-engineered piece of equipment.

Tweaking the Throttle Attachment Tweaking the Throttle Attachment

The fuel servo mounted easily enough on the forward induction port of our IO-360-M1B, but getting the mixture and throttle brackets installed and adjusted correctly took a bit of time.

IO-360 DWG OP-22 IO-360 DWG OP-22

All instructions for installing the mixture bellcrank and throttle bracket are printed on Van’s DWG OP-22, which is in an 8.5x17” format and can be a bit tricky to interpret initially. We definitely had to use a few web resources and photos to supplement this document.

Installing the Mixture Bellcrank Installing the Mixture Bellcrank

The mixture bellcrank on the IO-360 mounts to a pair of oil sump bolts and translates the push-pull motion of the mixture cable to the mixture arm on the fuel injector servo.

Throttle Cable Mount Throttle Cable Mount

The throttle cable runs underneath the engine and attaches to a bracket on the underside of the oil sump. The cable is then sheathed in firesleeve to protect it from the heat of the nearby exhaust pipe (installed later).

Setting Throttle Travel Limits Setting Throttle Travel Limits

Lastly, one must adjust both control cables and actuator arms on both the mixture and throttle to ensure that full forward/aft travel on the cockpit levers translates to the full stop travel limits on the fuel servo. This took several hours of trial and error.

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