Propeller Controls, I

Fixed pitch propellers are operated by changing the throttle only, thereby changing thrust and RPM at the same time. Constant speed propellers are more complicated because the pitch can be set separately from the throttle and has a range from full fine to coarse during flight and into feather and reverse for certain operations as emergency and ground maneuvers.

A full understanding of operating propellers is required of the pilot as overspeeding the engine or setting reverse in flight or on finals would be nothing less than a real problem.

This page focuses on preflight checks applicable for any propeller and the in flight checks for constant speed propellers as the fixed pitch types usually have no controls in the cockpit to manipulate them during flight.

Propeller Operation

As there are a number of variable pitch propellers in use today on aircraft, it is important that the pilot is very familiar with the operation of the propeller in normal and emergency situations. Even the type of engine (gasoline, diesel or turboprop) could change operating procedures for the propeller. Limitations on certain combinations of RPM and manifold pressures are not uncommon due to frequency resonations in the engine propeller combination.

Preflight checks

Check the propeller blades for damage, nicks and any oil leaks under the spinner. This would indicate an unserviceable aircraft as engine oil is used to change the pitch of the blades. For optimum propeller performance do clean the blades after every flight, giving you the chance to check the blades properly.

Engine startup

Set the propeller control in the forward (full fine) position for piston engines. Free turbine turboprop aircraft usually leave the propeller feathered until the engine is fired up.

Pre-takeoff checks

During the runup, hydraulic operated propellers are are checked by changing the control from full fine to coarse (or a set RPM drop) two or three times. This makes sure that any cold oil left in the propeller is run through the engine for warmup so that propeller operation will not be sluggish.

Cruise checks

During cruise operate the engine RPM and manifold pressure according to the aircraft flight manual (read it thoroughly). Avoid overboosting by more than the recommended values. Any change in power settings should be done per procedure described below.

To increase power at a higher RPM:

To decrease power for a lower RPM:

Oversquare

It is perfectly fine to operate the engine in a so called oversquare condition where the RPM divided by 100 is lower than MAP, for example: 2300 RPM and 25" MAP, read here about running oversquare and in the aircraft/engine manuals. This will lower fuel consumption and increase the range of the aircraft.

Emergencies

In case of engine failure place the constant speed propeller in the full coarse pitch (blue lever fully backward) as to reduce the drag from it and increase glide range.

Pre-landing checks

During landing and go-around the propeller should be in the full fine position to assure the maximum power available should this be needed. Short final is the place where this check can be done together with setting carb heat cold.