Engines Flashcards
Purpose of engine
Convert potential energy into thrust.
Power vs weight
More weight decreases useful load
More weight up front effects CG
Somewhat of a sacrifice
●Sometimes more weight gives more power.
New technology has allowed the development of lighter engines with higher power outputs
Fuel economy
Specific Fuel Consumption – power created for fuel consumed
●Thrust specific fuel consumption (lbs/hr. divided by thrust)
●Brake specific fuel consumption (lbs/hr. divided by BHP)
●Equivalent specific fuel consumption (lbs/hr. divided by equivalent shaft HP)
At slow speeds and low altitudes, recip. and turboprops are more efficient.
Reliability vs durability
•Reliability - is the engine doing what it’s supposed to do and does it consistently perform as expected?
•Durability – what is the life of the engine?
•Varies based on how the engine is operated and how it is maintained
Compactness
•The smaller the engine, the smaller the engine compartment, the smaller the drag
•Smaller engines can lead to better visibility for the pilot
•Problems with compactness
•Sometimes more costly
•A small cowling can lead to cooling problems
•The more compact the engine and it’s compartment, the harder it is to work on the engine which increases maintenance costs
Prop
RECIP/PROP
–Lower initial cost
–Less expensive to repair
–Better low power
application
–More fuel efficient
–Better propulsive efficiency at slow speed
–Less FOD damage
Jet
JET
-More ultimate power
-Higher thrust to weight ratio
-Fewer moving parts
-Less vibration
-Better high speed/high altitude
-Easier to operate
Cooling types
•Liquid
•“liquid cooled engines” are liquid cools the cylinders which is then placed into a radiator which uses air to cool the liquid before it circulates again.
•Air
•“air cooled engines” are cooled directly by air passing over the cylinders
Liquid cooling advantages
•More even cooling of cylinders
•Less thermal shock
“Shock Cooling”
•Faster heat dissipation
•Required for higher power engines
Air cooling advantages
•Simple
•Lighter Weight
•Suitable for low power engines
•Uses Baffling to direct airflow
In-line cylinder arrangement
Con’s
•Poor cooling
•High weight to HP ratio
Pro’s
•Small frontal area
•Good for streamlining
•Allows short landing gear
•Allows good pilot visibility
Radial cylinder arrangement
Pro’s
Small depth area depending on how many banks of cylinders
Efficient cooling
Rugged and reliable
Con’s
Large frontal area creates considerable drag and visibility problems
Horizontally opposed cylinder arrangement
•Pro’s
•Low weight to power ratio
•Allows for good visibility when mounted horizontally in the nose
•Horizontal mounts work well for wing mounted engines
•Low vibration
•Con’s
•Cooling of rear cylinders on air cooled engines
•When mounted vertically, fluid lock can occur on lower cylinders
2-stroke did advantages
SHORTER POWER STROKE
INCOMPLETE EVACUATION OF EXHAUST GASES
MIXTURE OF INTAKE AND EXHAUST GASES
Archer specific engine
Lycoming IO-360-B4A
180 BHP
Direct drive
Fuel injected
361 cubic inch displacement
Four cylinder
Air cooled, horizontally opposed
