MC565-549-021 - McFarlane FAA-PMA 17 In Throttle Control Cable Vernier Assembly

MC565-549-021 – McFarlane FAA-PMA 17-Inch Vernier Throttle Control

Available now through the AirParts Aero marketplace.

Overview Section

The McFarlane MC565-549-021 is a high-precision Vernier Throttle Control Cable designed for general aviation aircraft. This FAA-PMA approved assembly allows pilots to make large power adjustments by pushing or pulling the knob, while also providing the ability to "fine-tune" engine RPM by rotating the knob (Vernier action).

McFarlane is renowned for engineering controls that exceed OEM standards, utilizing a patented roller action that eliminates the "clamping" or binding often found in older screw-type designs. The 17-inch length is a specific short-run configuration typically used in center-pedestal or sub-panel installations where the throttle body is located in close proximity to the cockpit.

Key Features Section

• Patented Roller-Action Vernier: Provides smooth, micro-adjustment capabilities without the friction or sticking associated with legacy spring-lock controls.

• Emergency Push-To-Relieve: Features a center button that, when depressed, bypasses the Vernier threads for immediate, full-travel throttle movements.

• High-Temperature Teflon Liner: The inner wire travels through a low-friction Teflon conduit, ensuring consistent performance even in high-heat engine compartments.

• Corrosion-Resistant Materials: Constructed with stainless steel inner wire and high-strength aluminum/steel fittings to resist environmental degradation and "seizing."

• Optimized 17-Inch Length: Designed for precision routing in tight cockpits, reducing the risk of excess cable loops that can cause "spongy" throttle response.

• FAA-PMA Certified: Fully approved for installation on a wide variety of certified aircraft as a superior alternative to original factory parts.

Technical Specifications Section

Aircraft Compatibility Section

The MC565-549-021 is primarily used in light single-engine aircraft where a short, direct throttle path is required:

• Cessna 120 / 140 / 150: Often used in upgraded panels or specialized engine conversions.

• Piper PA-18 Super Cub: Utilized in custom bush-pilot panels where the throttle is moved to a non-standard location.

• Experimental Aircraft (RV-series, Glastar): A favorite for homebuilders requiring a high-quality, short-throw vernier for fuel-injected engines.

• Custom Engine Swaps: Ideal for aircraft retrofitted with Continental or Lycoming engines that place the throttle arm near the firewall.

Technical Applications & Safety

The throttle cable is the primary link between the pilot and the engine's power.4 A failure here is a critical safety event.

Safety Warning: Proper Bend Radius is Critical. During installation, ensure the cable does not have any bends tighter than a 5-inch radius. Tight bends will cause the inner wire to wear through the Teflon liner, leading to a "stuck throttle" condition. Additionally, always use a new cotter pin or safety wire on the engine-side linkage. If the 10-32 rod end nut vibrates loose, you will lose all throttle control, usually resulting in the engine remaining at its last power setting or falling to idle.

Technical Engineering Insight

The engineering value of the MC565-549-021 lies in its Lost Motion Reduction. Traditional cables often have "slop" or "backlash" where the knob moves but the engine arm does not. McFarlane's specialized manufacturing process minimizes the gap between the inner wire and the outer conduit. This is particularly vital in a short 17-inch cable, where every millimeter of travel corresponds directly to engine performance. The Vernier rotation allows for precise "leaning" or "power-setting" (e.g., setting exactly 2450 RPM) without the "over-shooting" common in standard push-pull friction locks.6

Installation & Maintenance Addendum

1. Anti-Chafe Protection: Use adel clamps (cushioned loops) to secure the cable every 12-15 inches. This prevents engine vibration from turning the cable into a "saw" that could cut through aluminum structures or electrical wiring.

2. Rigging: When rigging the throttle, ensure you have "cushion" at both ends. When the cockpit knob is fully forward, the engine throttle arm should hit its mechanical stop just before the knob hits the panel. This ensures you can reach full power.

3. No Lubrication: Do not spray WD-40 or silicone into the cable. McFarlane cables are designed to run dry on their Teflon liners; adding oil will attract dust and grit, eventually turning into a grinding paste that destroys the cable.