Ground-adjustable propeller
Encyclopedia
A ground-adjustable propeller is a simple type of variable-pitch aircraft propeller
, (aka controllable pitch propeller
), whose blades can be rotated around their long axis to change their pitch
, but in this instance any adjustment can be performed only on the ground. Ground-adjustable propellers are much cheaper than in-flight-adjustable propellers, and are found on light aircraft
and very light aircraft.
Whereas a fixed-pitch propeller is the equivalent to a gearbox with a single gear ratio, a variable-pitch propeller may be compared to a gearbox whose ratios are infinitely variable between its two limits.
Fine pitch ("bottom gear") is selected for take-off, climb and landing, and coarse pitch ("top gear") for cruise speeds. Although a ground-adjustable propeller cannot be adjusted whilst in flight, it still has advantages over a fixed-pitch propeller, in that the pilot may, when on the ground, select between finer and coarser pitches to suit conditions of the proposed flight, as follows:
Aircraft in prime condition, a long runway, hard dry ground, cool dense dry air, a strong headwind, low altitude, & light payload (pilots, passengers, fuel & cargo).
Aircraft in "tired" condition, a short runway, soft wet ground, long or wet grass, still hot thin moist air, high altitude, & heavy payload (pilots, passengers, fuel & cargo).
Propeller
A propeller is a type of fan that transmits power by converting rotational motion into thrust. A pressure difference is produced between the forward and rear surfaces of the airfoil-shaped blade, and a fluid is accelerated behind the blade. Propeller dynamics can be modeled by both Bernoulli's...
, (aka controllable pitch propeller
Controllable pitch propeller
A controllable pitch propeller or variable pitch propeller is a type of propeller with blades that can be rotated around their long axis to change their pitch...
), whose blades can be rotated around their long axis to change their pitch
Blade pitch
Blade pitch or simply pitch refers to turning the angle of attack of the blades of a propeller or helicopter rotor into or out of the wind to control the production or absorption of power. Wind turbines use this to adjust the rotation speed and the generated power...
, but in this instance any adjustment can be performed only on the ground. Ground-adjustable propellers are much cheaper than in-flight-adjustable propellers, and are found on light aircraft
Light aircraft
A light aircraft is an aircraft that has a maximum gross take-off weight of or less.Many aircraft used commercially for freight, sightseeing, photography and scheduled flights are light aircraft.Examples of light aircraft include:...
and very light aircraft.
Whereas a fixed-pitch propeller is the equivalent to a gearbox with a single gear ratio, a variable-pitch propeller may be compared to a gearbox whose ratios are infinitely variable between its two limits.
Fine pitch ("bottom gear") is selected for take-off, climb and landing, and coarse pitch ("top gear") for cruise speeds. Although a ground-adjustable propeller cannot be adjusted whilst in flight, it still has advantages over a fixed-pitch propeller, in that the pilot may, when on the ground, select between finer and coarser pitches to suit conditions of the proposed flight, as follows:
- Conditions where a coarser pitch may be selected:
Aircraft in prime condition, a long runway, hard dry ground, cool dense dry air, a strong headwind, low altitude, & light payload (pilots, passengers, fuel & cargo).
- Conditions where a finer pitch should be selected:
Aircraft in "tired" condition, a short runway, soft wet ground, long or wet grass, still hot thin moist air, high altitude, & heavy payload (pilots, passengers, fuel & cargo).