Universal Vernier-Assist^TM Controls
McFarlane invents a new type of vernier engine control
This new type of control has all the fine adjustment benefits of an old style push-button release vernier control, with the simplicity, responsiveness and jam-proof safety of a friction lock control.

McFarlane’s patented Vernier-Assist™ offers the pilot precision control of the engine, unlike anything else on the market! The Vernier-Assist assembly operates on friction alone by simply turning the knob, with no threads or locking balls/pins. It also allows for normal coarse movement by pushing in or out on the knob. Unlike standard threaded vernier controls, this design cannot be jammed. The friction control provides smoothness and precision when operating the throttle and a friction lock secures the control in position, but it can be easily overridden in the case of an emergency. It is SAFE!

You asked for it and now we have it. Not only do we offer Vernier-Assist for non-certified aircraft and an extended line of FAA-PMA approved controls, the breakthrough design is now approved on throttle controls for Cessna, Piper, Beechcraft, Grumman, and Bellanca.

• Jam-proof safety
• Precision power adjustments
• Smooth friction control
• Light and compact
• Standard Vernier performance without the button!
• Assembly Video

These light weight controls use a patented roller action and do not use a positive lock thread engagement. Coarse adjustments are made by pushing the knob inwards or pulling the knob outwards. Fine adjustments are made by rotating the knob clockwise or counterclockwise. For extreme conduit routing or heavy carburetor load installation, slight inward or outward assist pressure could be required during rotation.

US Patent No. 8,485,057 B1 

MCVA Series Controls: 
Available in a variety of standard lengths or custom fabricated to your unique requirements.  

Installation Instructions:
- Control with threaded end
- Control with wire end