Engine Theory Flashcards
What is the ‘powerplant’ in a helicopter?
The engine that drives the main rotor, tail rotor, and accessories like the alternator and squirrel cage fan.
What engine powers the R22 Beta II?
Lycoming O-360-J2A.
What do the designations ‘O’ and ‘360’ mean?
‘O’: Horizontally opposed cylinders.
‘360’: 360 cubic inches of displacement.
What are the R22 engine’s horsepower ratings?
Originally 160 then:
145 HP at 2700 RPM (Lycoming derating).
131 HP for 5 minutes TO (Robinson derating).
124 HP maximum continuous power (Robinson derating).
Why is the engine derated?
Ensures compatibility with the airframe and drivetrain.
Increases engine lifespan to meet the 2200-hour overhaul mark.
What cools the R22’s engine?
The squirrel cage blower pushes air around fins on engine and oil cooler
What does the carburetor do?
Mixes air and fuel in precise ratios for combustion.
What are the key components of the carburetor?
Venturi: Increases airspeed and lowers pressure to draw in fuel.
Float mechanism: Regulates fuel level within bowl for steady delivery.
Throttle butterfly valve: Adjusts airflow into the engine.
Mixture control: Adjusts the air-fuel ratio.
What is the purpose of the air filter?
Prevents debris from entering the carburetor and engine.
What are induction tubes?
Channels air-fuel mixture from the carburetor to the cylinders.
What causes carburetor icing?
Cooling from fuel evaporation and pressure drops in the carburetor.
What are the effects of carb ice?
Airflow restriction, power reduction, and possible engine stoppage.
When should carb heat be used?
-When temps between -4 and 30C and DP spread less than 15, use carb heat as follows:
-use full carb heat during warm-up to preheat induction system
-during takeoff, climb, and cruise as required to kee CAT gauge out of yellow
-during descent and autos / power settings below 18” because the CAT gauge does not indicate correct carb temp below 18” of MAP
What operational impacts does carb heat have?
Reduces engine power, requiring an additional ~1.5 in Hg manifold pressure for maximum power.
Lowers hover ceilings by up to 2000 feet (610 meters).
How does the governor mask carb ice?
The governor will automatically increase throttle and maintain constant MAP and rpm as ice forms until it becomes too congested, then loss or power / rmp may occur
How does carb heat assist work?
The carb heat assist correlates carb heat changes with the collective setting. Lowering the collective mechanically adds heat and raising collective mechanically reduces heat.
Where does the heated air for carb heat come from?
The carburetor heat system directs air warmed by the engine’s exhaust shroud into the carburetor. When activated, a valve switches from cold intake air to this warm air source, helping prevent carburetor icing by raising the air temperature entering the carburetor.
What are magnetos?
Independent generators that produce high-voltage electricity (~20,000 volts) for spark plugs.
What is the purpose of dual magnetos?
Powers two spark plugs per cylinder for redundancy and smoother combustion.
What is the purpose of the shower of sparks system, and how does it assist during start-up?
The shower of sparks system is an ignition aid that sends a rapid series of electrical sparks to the left magneto during engine start-up.
This ensures reliable ignition by providing multiple opportunities for the air-fuel mixture to ignite, compensating for the magneto’s reduced efficiency at low engine RPM.
What is the starter vibrator (shower of sparks), and how does it function?
The starter vibrator is a component of the shower of sparks system.
It uses electrical power from the battery to create a pulsing current that generates multiple sparks in the left magneto during the cranking phase.
These rapid sparks help ignite the air-fuel mixture when the engine is spinning too slowly for the magneto to generate sufficient power on its own.
What is the impulse coupling, and what role does it play during engine start-up?
The impulse coupling is a spring-loaded device in the left magneto.
It delays and amplifies the spark at low engine RPM by storing rotational energy and releasing it suddenly.
This ‘snap’ creates a hotter and well-timed spark to ignite the air-fuel mixture more effectively during start-up, compensating for the slow cranking speed of the engine.
What connects the crankshaft to the camshaft?
A timing chain, belt, or gear system.
What does the camshaft do?
Lobes push pushrods, which actuate rocker arms to open and close intake and exhaust valves.
What is the role of pushrods and rocker arms?
Pushrods: Transfer motion from camshaft lobes to rocker arms.
Rocker arms: Convert pushrod motion into valve movement.
What are the intake and exhaust valves?
Intake valve: Opens to allow air-fuel mixture into the cylinder.
Exhaust valve: Opens to expel combustion gases.
What happens during the intake stroke?
Intake valve opens; piston moves downward, drawing in the air-fuel mixture.
What happens during the compression stroke?
Both valves close; piston moves upward, compressing the mixture.
What happens during the power stroke?
Spark plugs ignite the mixture, forcing the piston downward.
What happens during the exhaust stroke?
Exhaust valve opens; piston moves upward, expelling gases.
What does the manifold pressure gauge measure?
Absolute pressure (in Hg) in the intake manifold, indicating engine power output.
What does manifold pressure indicate with the engine off at sea level?
Ambient atmospheric pressure (29.92 in Hg at sea level on a standard day).
How is engine RPM displayed?
On the tachometer, as a percentage of maximum RPM (104% = 2652 RPM).
What does higher manifold pressure indicate?
Greater power output.
What does the oil system do?
Lubricates and cools engine components.
What are its components?
Oil cooler for temperature regulation and oil filter for debris removal.
What is the acceptable oil range for the R22?
Between 4 and 6 quarts, using 15W50 or 20W50 oil.
