ENGINE AND INLET ANTI-ICE SYS / DE-ICE EQUIP Flashcards
What are the three ways to anti-ice the engine?
- vent bleed air into the engine swirl vanes and inlet guide vanes by the engine anti-ice / start bleed valve
- vent bleed air into the airframe engine inlet by the engine inlet anti-ice valve
- continuously pump engine oil through the scroll vanes
What type of valves are used for anti-ice operation?
solenoid-operated air valves
they are held closed electrically. de-energized the valves are opened
What does the engine anti-ice / start bleed valve do?
provides 5th stage bleed air to the engine swirl vanes and inlet guide vanes with anti-ice selected ON and opens during engine starts
When does the engine anti-ice / start bleed valve open during starts? When does it close?
the valve remains open below 80.5% Ng to prevent compressor instability during starts
above 96.5% Ng, the valve closes, unless anti-ice is selected on, or the aircraft experiences a loss of electrical power
the range of acceptable Ng speeds at which the valve opens and closes is depended on OAT
Name the three indications of a malfunctioning anti-ice start / bleed valve.
- Appearance or disappearance of the ENG ANTI-ICE ON advisory when outside of the range specified in the chart in Chapter 22.
- No illumination of [ENG ANTI-ICE ON] advisory when ENG ANTI-ICE switch is ON.
- No rise in TGT when ENG ANTI-ICE switch is selected ON.
What is the indication of a malfunctioning engine inlet anti-ice valve?
[INLET ANTI-ICE ON] advisory when OAT > 13C
the resultant loss of torque could be a maximum of 49% when the anti-ice valves are open.
What is the difference between main and tail rotor de-icing?
the main rotor blades are de-iced in cycles and the rotor blades are de-iced simultaneously
main rotor blades are de-iced in cycles to reduce power requirements, to de-ice in cycles the main rotor blades have a blade de-ice distributor
Describe the operation of the Freon bellows.
- <4C, valve open [INTEL ANTI-ICE ON] appears when inlet temp = 93C
- 4-13C, valve is variably open based on OAT
- > 13C, valve closed [INTEL ANTI-ICE ON] extinguishes when inlet cowling temp <93C
Where is the inlet anti-ice valve located?
the engine inlet cowling
Where is the engine anti-ice start/bleed valve located?
mounted to the bottom of the compressor section
If the DE-ICE MASTER switch is ON, what controls the engine anti-ice/start bleed and inlet anti-ice valve?
the ice detector
The DE-ICE MASTER switch position controls what function?
ON = the automatic functionality of the ENG ANTI-ICE, WINDSHIELD ANTI-ICE, and BLADE DE-ICE POWER systems when ice accumulation sensed by ice detector
OFF = automatic function disabled
ON + ENG ANTI-ICE, WINDSHIELD ANTI-ICE, and/or BLADE DE-ICE POWER = auto function disabled and appropriate system will operate continuously
How does the ice detector sense ice accumulation? How can you determine the severity of icing?
ice detector, mounted on No.2 engine cowling, senses ice accumulation on a vibrating probe by measuring the change in probe frequency.
simultaneously, an aspirator heater on the probe is turned on to heat the probe, and shed the accumulated ice, resetting it for another cycle.
the severity of icing environment is proportional to the rate at which the probe heater is cycled.
When should the Blade De-Ice MANUAL (T, L, M) mode be used?
when [ICE DETECT FAIL] illuminates or when there is no indication of failure but one of the three following conditions exist:
- the pilot has determined by judgement of icing intensity that the ice rate system is inaccurate
- torque required has increased to an unacceptable level
- helicopter vibration has increased to an unacceptable level
When is pitot heat required?
pitot heat shall be turned on when OAT is 5*C and below or when visible moisture is present.
WARNING: Failure to turn on pitot heat in icing conditions may cause erroneous airspeed indications, which can lead to erratic and/or downward programming of the stabilator and loss of control of the aircraft.
