Airframe Flashcards
Power Plant
Rolls-Royce
Model: 250-C20B
Mounted at 47° angle and supported by 3 engine mounts
4 Sections: Compressor Section, Combustion Section, Turbine Section, Accessory Gearbox
420 SHP
375 SHP at 103% N2 Rpm at Take Off
350 SHP MCP
FCU and Governor on engine
FCU on right side
Governor on left side
(When looking from aft of engine to the front of heli)
Overrunning Clutch
Mounted on Accessory Drive Gearbox and acts as a freewheel unit in the event of an engine failure.
Tail rotor drive shaft
Transmits power from main rotor transmission to the tail rotor transmission.
A single aluminum tube with Bendix or Kamatics couplings which operate without intermediate supports.
Excessive oscillation of the drive shaft during acceleration and deceleration is suppressed by drive shaft damper at rear of boom fairing.
Tail rotor transmission
At the end of the tail boom.
Changes direction of drive 90° and increases shaft speed from 2140 to 2933 RPM.
Splash lubricated gears and bearing.
0.5 pint of oil.
Chip detector installed.
Main rotor assembly
5 Bladed Fully Articulated
Blades balanced span wise to a master weight and individually interchangeable.
Lead-lag movements dampened by elastomeric dampers.
Centrifugal forces, flapping and feathering allowed by the 5 strap packs.
Strap Configuration allows centrifugal load exerted by one blade to be countered by force exerted by 2 opposite blades.
Torque Events (TE)
Transition to a hover from forward flight.
Any external lift operation.
All autorotations including power recoveries.
For all external lift operators, an external lift is recorded as 2 TE’s (pick-up and drop-off).
Hover taxi with no external load will result in no TE’s.
Tail Rotor
2 bladed semi-rigid
A bonded in-place metal airfoil with a spar formed from honeycomb material.
A strap pack counteracts blade centrifugal forces.
Fuel system
System is a suction type.
Consists of two interconnected fuel cells made of synthetic rubber and vented.
An engine driven fuel pump.
A start pump and drain valve in left fuel cell.
Total capacity of 64 gallons, 435 lbs
1.9 gal unusable (12.92 lbs)
LOW FUEL light on at approx 35 lbs fuel. (22 lbs usable), approx 5 gallons
27-29 gal/hr (±190 lbs/hr)
Has an aftermarket anti-ice filter.
Anti-Ice Airframe Fuel Filter
Mounted in series between the fuel system and the engine fuel system.
Electrical and mechanical equipment sense the build-up of ice in the filter unit and automatically illuminates a caution light in the cockpit and turns on the start pump.
Has a filter bypass should the filter become completely clogged.
Ground Temp prior to flight above 5° C limits operations to below 14,000’ PA.
Ground Temp prior to flight less than 5° C limits operations to below 12,000’ PA.
Do not drain from filter unless start pump is on.
Operation check:
Circuit breaker IN.
Dimming switch in BRT position.
If FUEL FILTER light is illuminated press to reset.
Depress red press-to-test button on top of the filter unit; hold for 5 seconds. Fuel filter and start pump lights should come on.
Release press-to-test button, Lights above should remain on.
Depress FUEL FILTER light on panel; both lights should go out. Caution system is reset.
Engine oil system
A circulating dry sump type (stores oil in separate tank) with an airframe mounted external oil tank and oil cooler.
Oil Pump and filter:
A spur gear type oil pump, consisting of one pressure element and 4 scavenge elements, mounted within the accessory gearbox. An assembly consisting of an oil filter, filter bypass valve, and pressure regulating valve located in the upper left hand side of the accessory gearbox. A check valve is located in the oil filter outlet.
Distribution:
Oil from tank is delivered to the pressure pump which pumps oil through the filter then to various points of lubrication. Check valve is open when engine is running and closed when not.
Oil cooler is belt driven of the main rotor shaft.
Oil level should be checked within 15 minutes of engine shutting down.
Strap Packs
Strap configuration allows centrifugal force exerted by one blade to be countered by the force exerted by two opposite blades. This very light centrifugal loads are sensed by the hub.
V-legs of the strap pack rotate as driving members to turn the blades.
Strap packs are configured to allow feathering and flapping.
It is acceptable to operate having a strap pack with up to two failed laminates in any one leg of the strap assembly.
Main rotor diameter
26.41’
Length rotor tip to tail
30.44’
Height from ground to stinger
1.58’
