ACFT 2 Flashcards
(16 cards)
What are the advantages of a Piston engine?
-Easy to access and maintain
-Quick power changes
-Cheaper to manufacture
-Low costs, good for training
-Smaller which allows for a smaller plane (a/c can land at smaller airfields
-Short landing/T.O. distance
What are the disadvantages of a Piston engine?
-Less economical as power is only produced through part of the process
-Increased wear & tear due to lots of moving parts
-Limited service ceiling without compressed air
-Poor long haul performance
-Loud
Describe the characteristics of a prop
-Twisted to change AoA across leading edge allowing for same lift produced
-Blades accelerate air backwards to create thrust
-Optimum AoA of 2-4 degrees
How can you improve efficiency of a prop?
-Increase number of blades
-Increase blade diameter
-Increase blade width
Describe a fixed-pitch prop
Pitch is either set to fine for good T.O/climb performance which is good for trainers or to fine for improved cruise efficiency. Compromise of performance
Describe a variable-pitch prop
-AoA of blades can be changed from fine to coarse depending on stage of flight for efficiency at all times.
-A “reverse” angle can be used to reduce landing distance
-Can be “feathered” to angle of nearly 90degrees in cases of engine failure to reduce drag
What are the advantages of a Jet engine?
-Low vibration/cabin noise
-High ceiling
-More power
-Cheaper fuel
-Less engine parts=relatively lighter
What are the disadvantages of a Jet engine?
-High initial cost
-Delay in engine take-up (spool time)
-Longer T.O/landing time
-Slower speed changes
-More training required
Describe a Turbo prop
Exhaust gas turns turbine, which spins a drive shaft connected to a gearbox. This drives the prop. Additional exhaust gases give extra thrust
Describe a Turbojet
Air is ingested and compressed, mixed with fuel. Exhaust gases drive a turbine (which is connected to the compressor). Remaining exhaust gases are used as thrust. More efficient at supersonic speeds
Describe a Turbofan
Air ingested by compressor, mixed with fuel and exhausted through a turbine which drives the 2 stage compressors (low and high pressure). Additional “bypass” air is fed around the compression chamber and exhausted out the back along with exhaust gases to create additional thrust. Bypass air makes the engine comparatively quiet for the power produced
Describe a Ramjet
Air is fed into combustion chamber at high speed and mixed with fuel. Exhaust gases are forced through nozzle increasing thrust.
Must be started at high speed. No moving parts. Works best at Mach 2+
Describe a Turboshaft
Works the same as a Turboprop, however, gear box is attached to rotor or something other than a prop.
What are the advantages of a Turboprop?
-Power is independent of speed giving increased take off performance
-Slipstream produced behind prop gives improved elevator/rudder control at low speeds
-Economical at low speeds/altitudes
-Short T.O
-Less prone to intake damage
-Interconnected engine/prop controls give rapid power control
What are the disadvantages of a Turboprop?
-Lower cruise due to weather
-Expensive to make
-More drag on frontal area
-Loud and increased vibrations in cabin
What are the 6 types of aviation fuel?
-AVGAS 82UL
-AVGAS 100
-AVAS 100LL
-JET A
-JET A-1
-JET B
