Engine Oil System

Question 1

How is the engine cooled?

Answer 1

Engine bearings and gears are lubricated and cooled by circulation of pressurized oil.

Question 2

Capacity of the Engine oil system

Answer 2

1.68 US gal

Question 3

When is the oil cooled?

Answer 3

• 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.

Question 4

How does the thermostat valve work?

Answer 4

< 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

Question 5

Type of oil system

Answer 5

Variable pressure, full flow, dry sump, synthetic oil

Question 6

Max temp

Answer 6

115C

Question 7

How is sealing accomplished

Answer 7

3 Gas generator bearings and 2 power turbine bearings are sealed by pressurized labyrinths

Question 8

When is the thermostatic bypass valve open/closed?

Answer 8

Open below 74C
Begins to close at 74C
Fully closed at 86C

Question 9

Where is the thermostatic bypass valve located?

Answer 9

Transmission deck on the right side
Silver module with 4 black oil tubes

Question 10

Where is the Thermal Switch located?

Answer 10

Transmission deck on the right side
Connected to the module aft of the oil tank
Circular and silver, inboard

Question 11

How is oil temp info delivered to the cockpit? Where is the sensor located?

Answer 11

• 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

Question 12

Location of the Oil Tank Reservoir

Answer 12

• Mounted to the transmission deck on the right side
• Teal colored tank with filler port and sight glass.

Question 13

Where is the engine oil pump located?

Answer 13

Mounted on the left side of the engine
Black cylinder with orange oil line going to it

Question 14

Where is the engine oil filter located?

Answer 14

Mounted on the upper left side of the engine
Silver with an LRB in the top center

Question 15

How do we get oil pressure information?

Answer 15

• 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

Question 16

How is the oil cooled?

Answer 16

• Forward flight, ram air flowing over oil cooler
• Hover, cooling airflow is generated by the motor-driven fan

Question 17

How many chip detectors in the system and where are they?

Answer 17

1 Chip detector
Mounted at the outlet of the oil scavenge pumps

Question 18

How many oil pumps are there?

Answer 18

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)

Question 19

Passage of oil through the system

Answer 19

1. Oil in the tank gets pulled by the pressure pump towards the engine
2. Passes the Thermal Switch (for the cooler fan motor) If 77C, sends signal to start the fan cooler motor
3. Passes the Temp probe (for the VEMD temp gauge)
4. Goes through the pressure pump
5. Goes through the filter
6. Passes the low oil pressure switch (for the ENG P red light)
7. Passes the pressure transmitter (for the VEMD pressure gauge)
8. Lubricates the engine
9. Drawn from the engine by the scavenge pumps
10. Passes the chip detector
11. Passes the thermostat valve
12. <74C goes back to the tank
13. At 86C goes to the cooler

Question 20

Temps at which the cooling fan turns on and off

Answer 20

On at 77C
Off at 68C