DONE 3I Airplane Systems - Propeller Flashcards
- AIRPLANE ONLY*
2. Discuss fixed-pitch propellers. (FAA-H-8083-25)
The pitch of this propeller is fixed by the manufacturer and cannot be changed by the pilot. Two types of fixed-pitch propellers are:
Climb propeller—has a lower pitch, therefore less drag. Results in higher rpm and more horsepower being developed by the engine; increases performance during takeoffs and climbs, but decreases performance during cruising flight.
Cruise propeller—has a higher pitch, therefore more drag. Results in lower rpm and less horsepower capability; decreases performance during takeoffs and climbs, but increases efficiency during cruising flight.
- AIRPLANE ONLY*
1. What type of propeller does this aircraft have?
The airplane propeller may be described as
a. All-metal,
b. Two-bladed,
c. Constant-speed, and
d. Governor-regulated.
- AIRPLANE ONLY*
3. Discuss variable-pitch propellers (constant speed). (FAA-H-8083-25)
An airplane equipped with a constant-speed propeller is capable of continuously adjusting the propeller blade angle to maintain a constant engine speed. For example, if engine rpm increases as a result of a decreased load on the engine (descent), the system automatically increases the propeller blade angle (increasing air load) until the rpm has returned to the preset speed. The propeller governor can be regulated by the pilot with a control in the cockpit, so that any desired blade angle setting (within its limits) and engine operating rpm can be obtained, thereby increasing the airplane’s efficiency in various flight conditions.
- AIRPLANE ONLY*
4. What does the propeller control do? (FAA-H-8083-25)
The propeller control regulates propeller pitch and engine rpm as desired for a given flight condition. The propeller control adjusts a propeller governor which establishes and maintains the propeller speed, which in turn maintains the engine speed.
- AIRPLANE ONLY*
5. What would the desired propeller setting be for maximum performance situations such as takeoff? (FAA-H-8083-25)
A low pitch, high rpm setting produces maximum power and thrust. The low blade angle keeps the angle of attack small and efficient with respect to the relative wind. At the same time, it allows the propeller to handle a smaller mass of air per revolution. This light load allows the engine to turn at high rpm and to convert the maximum amount of fuel into heat energy in a given time. The high rpm also creates maximum thrust because the mass of air handled per revolution is small, the number of revolutions per minute is many, the slipstream velocity is high, and the airplane speed is low.
- AIRPLANE ONLY*
6. What is a propeller governor? (FAA-H-8083-32)
The propeller governor, with the assistance of a governor pump, controls the flow of engine oil to or from a piston in the propeller hub. When the engine oil, under high pressure from the governor pump, pushes the piston forward, the propeller blades are twisted toward a high pitch/low rpm condition. When the engine oil is released from the cylinder, centrifugal force, with the assistance of an internal spring, twists the blades towards a low pitch/high rpm condition.
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AIRPLANE ONLY*
7. When operating an airplane with a constant-speed propeller, which condition induces the most stress on the engine? (FAA-H-8083-3)
Excessive manifold pressure raises the cylinder compression pressure, resulting in high stresses within the engine. Excessive pressure also produces high engine temperatures. A combination of high manifold pressure and low rpm can induce damaging detonation; however, it is a fallacy that (in non-turbocharged engines) the manifold pressure in inches of mercury (inches Hg) should never exceed rpm in hundreds for cruise power settings. The cruise power charts in the AFM/POH should be consulted when selecting cruise power settings. Whatever the combinations of rpm and manifold pressure listed in these charts—they have been flight tested and approved by the airframe and powerplant engineers for the respective airframe and engine manufacturer.
