NCAA CPL Aircraft General Knowledge flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Four-stroke cycle

Sequence of intake, compression, power, and exhaust strokes in a reciprocating engine. The crankshaft turns twice per complete cycle, so each cylinder fires once every two revolutions.

Compression ratio

Ratio of cylinder volume with the piston at bottom dead center to volume at top dead center. Higher ratios improve thermal efficiency but require higher-octane fuel to avoid detonation.

Stoichiometric mixture

Fuel-to-air mass ratio at which all fuel and oxygen are consumed, about 15:1 for gasoline. Richer mixtures near 12.5:1 give best power; leaner mixtures give best economy.

Detonation

Explosive, uncontrolled combustion of the remaining fuel charge after normal ignition, producing high pressures and temperatures. Causes include high manifold pressure, high intake temperature, and over-lean mixtures.

Pre-ignition

Ignition of the fuel/air charge before the spark plug fires, typically caused by a glowing deposit, overheated plug, or hot exhaust valve. It can destroy an engine within seconds.

Carburetor icing

Ice forming in the venturi or at the throttle plate as fuel vaporization and pressure drop cool the airflow. Risk is greatest at ambient temperatures between about -7 °C and +21 °C with high humidity.

Mixture control

Cockpit control that adjusts fuel flow to match decreasing air density with altitude. Leaning restores power and economy aloft but must be enriched before descent or high-power operation.

Magneto

Self-contained ignition device that generates its own high-voltage current by electromagnetic induction, independent of the aircraft battery. Two magnetos firing separate plugs provide redundancy.

Density altitude

Pressure altitude corrected for nonstandard temperature. It represents the altitude the aircraft performance feels, so high temperature and low pressure raise density altitude and degrade takeoff and climb.

Manifold pressure

Absolute pressure in the engine intake manifold, read in inches of mercury. It indicates power available on a constant-speed engine; high values at low RPM increase detonation risk.

Fixed-pitch propeller

Propeller whose blade angle cannot be changed in flight. A climb propeller uses low blade angle for high RPM and thrust; a cruise propeller uses higher blade angle for speed.

Constant-speed propeller

Propeller whose blade angle is adjusted by a governor to hold a selected RPM as airspeed and power change. The cockpit control sets RPM, while throttle sets manifold pressure.

Propeller slip

Difference between the theoretical distance a propeller would advance in one revolution and the actual distance advanced. Slip reflects the thrust-producing work done on the air.

Load factor

Ratio of total lift to aircraft weight. In a level turn, load factor equals 1 divided by the cosine of the bank angle, so a 60-degree bank doubles the load.

Stall speed and load factor

Stall speed increases with the square root of load factor. Doubling load factor raises stall speed by about 41 percent, which is why steep turns and abrupt pull-ups raise stall margins.

Angle of attack

Angle between the wing chord line and the relative wind. Lift increases with angle of attack up to the critical angle, beyond which the wing stalls regardless of airspeed.

Induced drag

Drag created as a byproduct of lift, strongest at high angle of attack and low airspeed. It decreases with speed while parasite drag increases, so total drag is lowest at L/D maximum.

Parasite drag

Drag from form, skin friction, and interference that increases with the square of airspeed. It dominates at high speed, whereas induced drag dominates at low speed.

V speeds

Certificated operating speeds: Vne never exceed, Vno maximum structural cruise, Va design maneuvering, Vfe flap extended, Vso stall in landing configuration, and Vx or Vy best angle or rate of climb.

Va maneuvering speed

Maximum speed at which full control deflection will not overstress the structure. It decreases with weight, so a lighter aircraft has a lower maneuvering speed.

Center of gravity

Point where aircraft weight is considered concentrated. Forward limits raise stall speed and pitch force; aft limits reduce stability and can make stall recovery difficult.

Static stability

Tendency of an aircraft to return to its original attitude after a disturbance. Positive static stability requires the center of gravity ahead of the aerodynamic center.

Dihedral effect

Upward wing angle that produces more lift on the lower wing in a sideslip, creating a rolling moment that opposes the bank. It contributes lateral stability and Dutch roll tendency.

Adverse yaw

Yaw away from the direction of turn caused by increased induced drag on the downgoing aileron wing. Coordinated rudder pressure counters it and keeps the turn balanced.

P-factor

Asymmetric thrust at high angle of attack, where the descending blade takes a larger bite of air. It yaws the aircraft left in a climb for a clockwise-turning propeller.

Gyroscopic precession

A force applied to a spinning object acts 90 degrees later in the direction of rotation. In a tailwheel aircraft it contributes to yaw when the tail is raised.

Service ceiling

Altitude at which an aircraft's maximum rate of climb falls to 100 feet per minute. Absolute ceiling is where climb rate reaches zero and level flight is no longer possible.

Hydraulic system

System using pressurized fluid to actuate landing gear, brakes, or flaps. A reservoir, pump, pressure relief valve, and selector valves maintain and direct pressure safely.

Electrical bus

Common distribution point connecting the battery, alternator, and loads. An avionics master switch isolates sensitive equipment from voltage spikes during engine start and shutdown.

Vacuum system

Engine-driven pump system that spins gyroscopic instruments such as the attitude indicator and heading indicator. A suction gauge shows whether pressure is within limits.

Pitot-static system

System supplying ram and static pressure to the airspeed indicator, altimeter, and vertical speed indicator. Blocked pitot tubes cause airspeed errors, so the heater is used in icing conditions.

Fuel octane rating

Measure of fuel resistance to detonation. Using a grade below the engine's requirement can cause detonation and engine damage, especially at high power and lean mixtures.