How is the engine cooled?
Engine bearings and gears are lubricated and cooled by circulation of pressurized oil.
Capacity of the Engine oil system
1.68 US gal
When is the oil cooled?
- When the bimetallic strip of Thermal Switch detects 77C in the oil tank, the contact closes and the relay energizes the motor-driven fan.
- When the oil temp drops below 68C, the thermal contact opens and the fan motor stops.
How does the thermostat valve work?
< 74C - The valve is full open by spring. Oil is drawn to the tank since the pressure is less in that direction
74 - 86C - The valve stem expands when the temp increases so it slowly closes the valve
At 86C - Valve is fully closed, oil is directed to the cooler
Type of oil system
Variable pressure, full flow, dry sump, synthetic oil
Max temp
115C
How is sealing accomplished
3 Gas generator bearings and 2 power turbine bearings are sealed by pressurized labyrinths
When is the thermostatic bypass valve open/closed?
Open below 74C
Begins to close at 74C
Fully closed at 86C
Where is the thermostatic bypass valve located?
Transmission deck on the right side
Silver module with 4 black oil tubes
Where is the Thermal Switch located?
Transmission deck on the right side
Connected to the module aft of the oil tank
Circular and silver, inboard
How is oil temp info delivered to the cockpit? Where is the sensor located?
- Oil temp (for the purpose of cockpit use) is taken from a Temperature probe
- Temperature is read after flowing through the engine and before returning to the tank
- It is an upright silver probe aft of the oil tank, on the right side of the transmission deck
Location of the Oil Tank Reservoir
- Mounted to the transmission deck on the right side
- Teal colored tank with filler port and sight glass.
Where is the engine oil pump located?
Mounted on the left side of the engine
Black cylinder with orange oil line going to it
Where is the engine oil filter located?
Mounted on the upper left side of the engine
Silver with an LRB in the top center
How do we get oil pressure information?
- Low pressure red light (ENG P) is read from an low oil pressure switch, after it goes through the filter
- Cockpit VEMD oil pressure is read by a pressure transmitter, also after it goes through the filter
How is the oil cooled?
- Forward flight, ram air flowing over oil cooler
- Hover, cooling airflow is generated by the motor-driven fan
How many chip detectors in the system and where are they?
1 Chip detector
Mounted at the outlet of the oil scavenge pumps
How many oil pumps are there?
1 Pressure pump - draws oil from the tank to the engine
3 scavenge pumps - draws oil from the engine to the thermostat valve (to the cooler or the tank)
Passage of oil through the system
- Oil in the tank gets pulled by the pressure pump towards the engine
- Passes the Thermal Switch (for the cooler fan motor) If 77C, sends signal to start the fan cooler motor
- Passes the Temp probe (for the VEMD temp gauge)
- Goes through the pressure pump
- Goes through the filter
- Passes the low oil pressure switch (for the ENG P red light)
- Passes the pressure transmitter (for the VEMD pressure gauge)
- Lubricates the engine
- Drawn from the engine by the scavenge pumps
- Passes the chip detector
- Passes the thermostat valve
- <74C goes back to the tank
- At 86C goes to the cooler
Temps at which the cooling fan turns on and off
On at 77C
Off at 68C
