EAA Sport Aviation

Controls for Your Engine
Choosing your type

BY DICK KOEHLER

SOMETIMES PILOTS ARE REFERRED to as “stick and throttle jockeys” because there are two distinctly different control systems on the plane. Stick, of course, refers to the aircraft’s primary flight controls, usually for the elevator, ailerons, and rudder. These are critical for flight, and most people build them with the best materials. Throttle refers to the engine controls, and in my experience, many builders tend to skimp a bit here. I have seen everything from engine controls taken off certificated aircraft to parts that were shaky on lawn mowers being used. So, let’s look at the options that are available for the homebuilder to ensure proper—and safe—control of the engine. This will be a two-part column; I’ll cover the cockpit side in this issue and the engine connection side next month.

Basic engine controls are usually of the push/pull type, made by
moving a solid or multi-strand inner wire within a solid-wire, spiral-
wound outer sleeve. In the simplest designs there is no inner or
outer material to help reduce friction or keep out contaminants.
Better units have polyethylene liners, and the best have Teflon
casing liners for smooth operation, even in
high-heat engine areas. Better units will also
have a polyolefin outer protective cover.
This outer cover will usually add about
$1.50 per foot to the cost of the control (an
extra $10 on average) but will add to the life
of the control. Standard controls have an
outside diameter of either 3/16 inch or 1/4
inch and are held in place with AN742-D3 or
-D4 clamps. Controls with the outer cover
seem to lock in place better in the clamp and
resist slipping.