PPL Aircraft General Knowledge flashcards
PPL Aircraft General Knowledge · Build recall with a focused review session.
33 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Semi-monocoque structure
- Construction in which the stressed skin carries shear and bending, stringers and frames prevent skin buckling, and a few heavy members take concentrated loads.
- Fail-safe versus safe-life
- Fail-safe structure tolerates a detectable crack until inspection finds it; safe-life parts are retired at a fixed calculated life before failure is expected.
- Mass balance of controls
- Weights or internal balances place the control surface centre of gravity ahead of the hinge line, preventing flutter and reducing hinge moments.
- Galvanic corrosion
- Corrosion caused by an electrolyte bridging two dissimilar metals, where the more anodic metal gives up material and the cathodic metal is protected.
- Four-stroke cycle
- Intake, compression, power and exhaust strokes, completed in two crankshaft revolutions, giving one power stroke per cylinder per two revolutions.
- Stoichiometric mixture
- The chemically ideal air-to-fuel mass ratio of about 15:1, at which all fuel and oxygen are consumed; best power needs a richer mixture.
- Detonation
- Explosive uncontrolled combustion of the remaining charge after normal ignition, caused by excessive pressure and temperature, lean mixture or low octane fuel.
- Carburettor icing
- Ice forming in the venturi and throttle area from fuel vaporisation and pressure drop, possible at ambient temperatures well above freezing in humid air.
- Constant-speed propeller
- A propeller whose blade angle is adjusted by a governor to absorb engine power at the selected rpm, keeping efficiency high across the speed range.
- Hydraulic force multiplication
- Pressure is force divided by area, so a large piston produces greater force and a small piston greater travel, with pressure set by the relief valve.
- Moment and CG
- Moment equals mass multiplied by arm from the datum; total moment divided by total mass gives the centre of gravity position.
- CG shift formula
- The centre of gravity moves by the added mass times its distance from the old CG, divided by the new total mass, in the direction of the added mass.
- Maximum zero-fuel mass
- The mass limit of the aircraft without usable fuel, protecting the wing root bending and landing gear loads from excessive payload plus fuel combinations.
- Forward CG effects
- A nose-heavy aircraft needs more tail-down force, giving higher stall speed, longer take-off run, heavier controls and better spin recovery.
- Aft CG effects
- A tail-heavy aircraft gains speed and shorter take-off but loses longitudinal stability, flares poorly and is more prone to enter a spin.
- Floor loading limit
- The maximum mass permitted per unit area or running metre of cabin or cargo floor, checked separately from total mass and centre of gravity.
- Density altitude
- Pressure altitude corrected for temperature and humidity; higher density altitude reduces engine power, thrust and lift, lengthening take-off and reducing climb.
- V1 decision speed
- The speed by which an engine failure must be recognised so the take-off can be continued or stopped within the available runway distance.
- Climb gradient formula
- Gradient in percent equals one hundred times height gained divided by horizontal distance, approximated from rate of climb and groundspeed in knots.
- Stall speed and load factor
- Stall speed rises with the square root of load factor: sixty degrees of bank gives a load factor of two and about forty-one percent higher stall speed.
- Contaminated runway
- A runway covered by standing water, slush, snow or ice, which reduces braking friction and increases take-off and landing distances substantially.
- Final reserve fuel
- Fuel that must remain at destination, typically thirty minutes holding at 1500 feet above the alternate for commercial operations, never planned for use.
- Specific range
- Distance flown per unit of fuel, highest at the speed for best lift-to-drag ratio rather than at maximum speed or maximum endurance speed.
- Equal-time point
- The point on track where the time to continue to destination equals the time to return to base, allowing for wind on each leg.
- ISA sea-level values
- Standard atmosphere at sea level is fifteen degrees Celsius and 1013.25 hectopascals, with a lapse rate of 1.98 degrees per thousand feet.
- True altitude correction
- True altitude differs from pressure altitude by roughly four feet per thousand feet for each degree Celsius of deviation from ISA temperature.
- Blocked static source
- With static pressure trapped, the airspeed indicator, altimeter and vertical speed indicator freeze at their values when the blockage occurred.
- Calibrated versus true airspeed
- Calibrated airspeed corrects indicated airspeed for position and instrument error; true airspeed further corrects for air density at altitude.
- Rigidity in space
- A spinning gyroscope maintains its axis direction in inertial space, which gives the attitude and heading indicators their stable reference.
- Magnetic compass turning error
- Acceleration and turning errors caused by magnetic dip, largest on northerly and southerly headings, where the compass leads or lags the turn.
- Ohm's law and power
- Voltage equals current times resistance, and power equals voltage times current, so doubling voltage for a fixed resistance quadruples the power.
- Ammeter versus loadmeter
- The ammeter shows current into or out of the battery, while the loadmeter shows the total current produced by the alternator or generator.
- Live magneto hazard
- A magneto is independent of the electrical system; if its grounding P-lead breaks, the engine can fire with the ignition switch selected off.