WACE Aviation flashcards

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

Angle of attack

The angle between the wing chord line and the relative airflow. Lift increases with angle of attack until the critical angle, beyond which the wing stalls.

Induced drag

Drag caused by lift generation, produced by wingtip vortices. It is greatest at low airspeed and high angle of attack, and decreases as airspeed increases.

Load factor

The ratio of total lift to aircraft weight. In a level turn it equals 1 divided by the cosine of the bank angle, so 60 degrees of bank doubles it.

Stall speed in a turn

Stall speed rises with the square root of load factor. At 60 degrees bank the load factor is 2, so stall speed increases by about 41 percent.

Best glide speed

The airspeed giving maximum lift-to-drag ratio, where induced and parasite drag are equal. It yields the greatest gliding range in still air.

Static stability

Positive static stability means a disturbance produces a restoring force returning the aircraft toward equilibrium. The horizontal tail behind the centre of gravity provides pitch stability.

Bernoulli's theorem

In steady incompressible flow, an increase in fluid velocity along a streamline is accompanied by a decrease in pressure and a change in height.

Pitot-static blockage

A blocked static port traps ambient pressure, so the airspeed indicator over-reads in a climb and under-reads in a descent while the altimeter freezes.

Four-stroke engine cycle

Induction, compression, power and exhaust. Each cylinder completes one power stroke every two crankshaft revolutions, which is why multi-cylinder engines smooth the output.

Bypass ratio

The mass flow of air through the fan bypass duct divided by the mass flow through the engine core. Higher ratios generally improve propulsive efficiency.

Unusable fuel

Fuel that cannot be delivered to the engine in all certified flight attitudes. It is excluded from usable fuel when computing endurance and range.

Tricycle landing gear

A nosewheel layout with main wheels behind the centre of gravity. Braking creates a nose-down moment, and the design resists ground looping.

Hydraulic relief valve

A valve that limits system pressure by returning excess fluid to the reservoir, protecting pumps, seals, lines and actuators from overpressure damage.

1 in 60 rule

A one degree tracking error displaces an aircraft about one nautical mile from track after 60 nautical miles. It is used for quick drift corrections.

Great circle

The shortest path between two points on a sphere, formed by a plane through the sphere's centre. It plots as a curve on a Mercator chart.

Magnetic variation

The angular difference between true north and magnetic north at a location. Variation east is subtracted from true heading to obtain magnetic heading.

VOR radial

A magnetic bearing measured from a VOR station outward. An aircraft tracking outbound on the 090 radial flies magnetic heading 090 away from the station.

Track and heading

Track is the actual path over the ground; heading is the direction the nose points. Drift equals track minus heading, positive when drifting right.

ISA conditions

International Standard Atmosphere sea level values: 15 degrees Celsius, 1013.25 hPa and a lapse rate of about 1.98 degrees Celsius per 1000 feet to the tropopause.

Density altitude

Pressure altitude corrected for temperature deviation from ISA. High temperature, high humidity and low pressure raise it and degrade aircraft and engine performance.

QNH and QFE

QNH set on the altimeter subscale gives altitude above mean sea level. QFE gives height above the aerodrome reference point.

METAR and TAF

METAR is a routine aerodrome weather observation. TAF is an aerodrome forecast for a stated validity period. SPECI reports significant unforecast changes.

Cold front passage

A cold front produces rapid lifting, a narrow band of heavy showers or thunderstorms, a sharp wind shift and a temperature drop after passage.

Final reserve fuel

Fuel that must remain at destination, commonly 30 minutes holding for light aircraft. It is planned separately from trip, contingency and alternate fuel.

Swiss cheese model

An accident model in which multiple failed defences, each like a hole in a slice of cheese, must align before an accident occurs.

Threat and Error Management

A framework that identifies threats and errors and applies countermeasures to avoid, trap or mitigate them before an undesired aircraft state develops.

Safety management system

A formal system built on four pillars: safety policy, safety risk management, safety assurance and safety promotion, used to manage risk proactively.

Just culture

A reporting culture that treats unintended human error non-punitively while holding reckless or intentional unsafe behaviour accountable.

Hypoxia

Inadequate oxygen supply to body tissues, causing euphoria, impaired judgement, headache and cyanosis. Time of useful consciousness falls rapidly above 25,000 feet.

IM SAFE checklist

A pre-flight fitness check covering Illness, Medication, Stress, Alcohol, Fatigue and Eating, used to decide whether the pilot is fit to fly.

Spatial disorientation

A conflict between vestibular sensations and actual aircraft attitude, often in cloud or at night. The remedy is to rely on instruments and maintain a scan.

Airspace Class G

Uncontrolled airspace in which no separation service is provided. Pilots are responsible for their own separation, and VFR and IFR may mix.