Jet Aircraft Glossary Terms Flashcards
Buffet Threshold
For a given set of conditions, the point at which buffet (either low or high speed) is first felt.
Buffet Boundary
For a given set of conditions, the line of speed and altitude combinations at which buffet will occur
Compressibility Effect
The effect of shockwaves on the aircraft at the critical mach number
Free Stream
The air conditions close to, but uninfluenced by, the aircraft
Incidence
The angle between the wing’s chordline and the free air stream
Lift
CL1/2RhoV2S
Stagnation Point
That point on the leading edge of an aerofoil surface where the upper and lower air streams last separate and where the airstream is locally brought to rest.
THP
Thrust horsepower; the power equivalent of the thrust exerted on the aircraft by the propulsive device.
Bleed Air
Air which has been compressed in the main engine compressor and utilised for cabin pressurisation and the driving of various services.
Bypass Ratio
The ratio of the total air mass flow through the fan stage of a by-pass engine to the air mass flow which passes through the turbine section. Typical value for a CFM-56 is 6.0
EPR
Engine pressure ratio; a ratio of pressures, usually the maximum cycle pressure (compressor delivery pressure) to air intake pressure or ambient pressure (depending on specific applications) which is an important turbine engine parameter and can be displayed to the pilot.
HP (and LP)
High (and low) pressure rotating systems.
N1 (and N2)
The rotational speed of the low (and high) pressure compressor of a two- spool engine expressed either as rpm or a percentage of the maximum value.
SFC
Specific fuel consumption; the quantity of fuel consumed in pounds per hour divided by the thrust of the engine in pounds.
Surge
A condition of aerodynamic instability in the compressor which can cause cyclic reversal of the airflow. It may be caused by disturbance of the air intake flow or by a fault condition and may lead to overheating and serious mechanical damage.
TGT
Turbine gas temperature; a temperature which may be used for engine control purposes, measured between the turbine stages of a multistage turbine engine: sometimes loosely employed for EGT.
EGT
Exhaust gas temperature; also known as JPT (jet pipe temperature). The temperature used for control purposes in many engines but less satisfactory than TGT in certain applications.
Thrust Line
The line along which the thrust acts. In a turbine engine the thrust line will be the centreline of the total exhaust flow, including the exhaust from the fan stage where applicable. The thrust line may not always coincide with the engine centreline since the exhaust ducts may be angled.
Compressibility Error
The error in flight instrument readings due to Mach number effect.
Position Error
The error in flight instrument readings due to the position and system limitations of the static and dynamic pressure sensing sources.
Gross Performance
The measured performance of a test aeroplane adjusted so as to be representative of the type and reflecting either a fleet mean or minimum guaranteed engine power.
Net Performance
The gross performance adjusted downwards to account for reasonable errors in operational variables and flying techniques.
Net Flight Path
The engine out climb after take-off providing adequate obstacle clearance under adverse circumstances. It covers the segment from screen height at V2 to the beginning of the en-route climb and specified powers, airspeeds and flap retraction details.
WAT (limiting conditions)
Conditions of aeroplane weight which, when combined with the aerodrome altitude and temperature, reduce the performance level to the airworthiness minima.
Gradient of Climb
Climb performance expressed as a gradient = the vertical height gained expressed as a percentage of the horizontal distance travelled.
IAS
Indicated airspeed; corrected only for instrument error.
EAS
Equivalent airspeed; IAS corrected for position error and compressibility error.
TAS
True airspeed; the true speed of the aeroplane relative to undisturbed air: EAS/ σ = TAS.