Feathering and thrust reversal

In addition to its use as a kind of gearing, the variable pitch mechanism can be used to reduce drag if one engine has stopped. This is done by feathering the propeller blades; turning them edge-on to the wind so that they stop rotating, as seen in Fig. 6.6.

Feathering may be automatic on some multi-engined aircraft to prevent adverse handling problems if one engine fails.

After touch-down, the variable pitch mechanism can be used to set the pitch to a negative angle, so that negative thrust or drag is produced. This reversed thrust feature can shorten the landing run considerably, and is almost invari­ably used on propeller-driven transport aircraft. It also conveniently enables the aircraft to be backed in or out of parking spaces.