PERF Flashcards
Describe how thrust is produced by a turbine (jet) engine
Turbine engines produce thrust in four stages.
1. Intake
2. Compression
3. Combustion
4. Exhaust
Air is compressed, therefore temperature increases, fuel is injected which burns the air, creating a high pressure in the combustion chamber. The high pressure air rushes to low pressure atmosphere via the exhaust section.
EPR
Engine Pressure Ratio (EPR) is the ratio of high pressure within the combustion chamber of a turbine engine to the ambient atmospheric pressure and is a measure of thrust.
The higher the EPR number, the higher the ratio, or difference between internal and external pressure, therefore the higher the thrust.
Define V1
Takeoff Decision Speed is the maximum speed during a takeoff roll at which the pilot may begin to reject a takeoff and the minimum speed during a takeoff roll in which the aircraft can reach the required height (35’) above the takeoff surface in the event of a takeoff.
Define VR
Rotation speed is the minimum speed during the takeoff roll at which the pilot may begin the rotation process.
Define V2
Takeoff Safety Speed is the speed at which the required one engine inoperative climb performance can be achieved for obstacle clearance purposes in the event of an engine failure during takeoff
Define VS
Stall speed
Define VSO
Stall speed in the landing configuration
Define VS1
Stall speed in a specified (by manufacturer) configuration
Define VC
Design cruising speed
Define VMO/MMO
Maximum operating limit speed
V=KIAS
M=Mach number
Define VREF
Reference landing speed also known as approach speed
Describe the four segments of climb and significance
Four segments of climb refer to the profile to be flown in the event of an engine failure during takeoff. Takeoff weight limited by one engine inop climb requirement based on these specs.
1.Liftoff to gear up,
2.Gear up to 400’ AGL (2.4% min climb gradient required)
3.400’ AGL, level to flaps up
4.Flaps up to 1,500’ AGL (1.4% min climb gradient required)
Define takeoff distance
Takeoff distance is the manufacturer horizontal distance along from the start of the takeoff to the point at which the airplane is 35 feet above the takeoff surface.
§25.113 Takeoff distance
Define accelerate-stop distance
Accelerate-stop distance is the distance necessary to accelerate an airplane from a standing start with all engines operating to the highest speed reached during a rejected takeoff, the pilot takes the first action to reject the takeoff at V1 for takeoff and come to a full stop.
§25.109 Accelerate-stop distance.
Define takeoff run available (TORA)
** TORA** is the total length of runway available for an aircraft to accelerate from brake release to liftoff and half the horizontal distance to climb to 35 ft.
It is effectively, the actual length of a runway that an aircraft can use for a takeoff roll.
Define takeoff distance available (TODA)
TODA is the distance available to accelerate from brake release, past lift-off, to the start of the takeoff climb.
TODA represents the entire distance that can be utilized for takeoff, including both runway and any clearway beyond the runway.
Define accelerate-stop distance available (ASDA)
Accelerated-Stop Distance Available (TORA) is the total length of runway available (which may include a stopway) to accelerate from brake release to V1 plus the distance required to safely decelerate to a stop following a rejected takeoff.
Define clearway
A clearway is an area beyond the runway free of permanent obstacles like buildings, trees, or terrain features.
Define stopway
A stopway is an area beyond the runway specifically prepared to provide extra stopping distance for aircraft that cannot stop in the standard runway length due to a rejected takeoff or landing due to factors like a wet or contaminated surface on the runway, brake failure, or landing gear failure.
Key features of a stopway include:
-At least as wide as the runway
-Positioned on extended runway center line
-Able to support aircraft without causing structural damage
How does runway slope affect takeoff and landing distance?
Uphill slope increases takeoff distance and decreases landing distance.
Downhill slope decreases takeoff distance and increases landing distance.
Define driftdown method one and method two
Driftdown
Loss of altitude after an engine fails in flight.
Driftdown altitude
Manufacturer-published altitude at which the airplane can maintain after an engine fails in flight.
Determining maximum takeoff weight relative to driftdown:
Method one: weight which will result in driftdown altitude that complies with 1,000’ (2,000’ in mountainous area) obstacle clearance throughout flight.
Method two: flight is broken down into segments with specified alternates if an engine fails, which permits a higher takeoff weight than Method one.
Define effective runway length (ERL)
Full published runway length minus displaced threshold (if any).
How does use of anti icing bleed or pressurization bleed air affect turbine engine performance and allowable takeoff weight?
The use of bleed air will reduce engine thrust, and therefore, may reduce allowable takeoff weight.
Is a jet more or less fuel efficient at high altitudes? Why?
More fuel efficient at high altitudes due to lower air density, which reduces airframe drag (assuming higher altitude doesn’t result in a higher headwind, which can reduce the efficiency by reducing ground speed, thereby increasing flight time.
Define landing distance
Landing distance is manufacturer-published horizontal distance necessary to land and to come to a complete stop from a point 50 feet above the landing surface.
§25.125 Landing.
Define landing distance available (LDA)
LDA is the available distance from the threshold to complete the approach, touchdown, and decelerate to a stop.
Define displaced threshold
A displaced threshold is a threshold located at a point on the runway other than the designated beginning of the runway.
Displacement of a threshold reduces the length of runway available for landing.
Describe the effect on turbine engine performance at a high elevation airport, high ambient temperature, and high relative humidity
Thrust will be reduced under any of these conditions due to lower air density. Lower air density means there are fewer air molecules available for compression and combustion. Lower air density may cause lower allowable takeoff weight as a result of lower thrust output.
Define VX
Speed for best angle of climb
Achieves greatest altitude over distance
FT/NM (feet per nautical mile)
Define VY
Speed for best rate of climb.
Achieves greatest altitude over time
FPM (feet per minute)
Define Maximum Takeoff Weight (MTOW)
The maximum takeoff weight for any given takeoff is the lowest of the following weight limits:
Maximum structural takeoff weight
Maximum structural landing weight
Maximum runway limited takeoff weight
Maximum runway limited landing weight
Maximum second segment limited weight
Maximum driftdown limited weight
Maximum takeoff or landing weight due to aircraft condition (CDL)
Four segments of climb (engine inop)
