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How to Choose an Airplane Propeller

Different degrees of pitch in a fixed pitch propeller can drastically change the flight characteristics of an aircraft. This changes the flight envelope to the degree that flight planning takes on different parameters. A low-pitch propeller raises the engine RPM, lowers the manifold pressure and gives the best rate of climb with the slowest cruise and highest fuel consumption. The low-pitch prop will also allow the shortest takeoff and climb of a 50-foot obstacle. On the other hand, a high-pitch prop will offer lower RPM, higher cruise speed and less fuel consumption. It will have the longest takeoff distance, lowest rate of climb and the highest manifold pressure.

Things You'll Need

Aircraft operator's manual

Instructions

- 1
  Determine the recommended pitches for the particular aircraft and engine as detailed in the operator's manual.
- 2
  Write down all flight parameters experienced in daily operations. These parameters include the heaviest takeoff weight of the aircraft, horsepower of the engine, average barometric pressure in the region, altitude of the base of operations and the length of the shortest runway included in the operations.
- 3
  Check the flight characteristics of each of the different available pitches. The most important considerations are the RPMs the engine will achieve with a certain pitch at full throttle so as not to stress the engine, the speed at 85 percent cruise and the rate of climb under all atmospheric conditions. The way to consider this aspect is to plan a takeoff from the highest altitude airport of operations at max takeoff, calm wind, lowest barometer, highest temperature and the highest humidity.
- 4
  Take all this information into consideration, and if most of the locations have plenty of runway--over 1,000 feet more than needed--chose a higher pitch prop, keeping in mind one rule of thumb: always run with a prop that will give 500 feet per minute climb under the worst conditions.

Aviation