NATOPS CH2.4 Fuel System

Question 1

How can the Helo be refueled?

What are some of the fuel systems capabilities?

Answer 1

Capable of pressure refueling, gravity refueling, and Helicopter In Flight Refueling (HIFR)

It has provisions to prime the engines, dump fuel, indicate quantity, and display low fuel levels

Question 2

How is fuel supplied to the engines

Answer 2

Fuel is drawn up by the engine driven fuel boost pump, then pumped through the engine fuel filter to the HMU, which will route fuel through the oil/fuel heat exchanger to the ODV and finally the engine

Question 3

What can cause the fuel press light to appear?

Answer 3

It could indicate a malfunction of the engine driven boost pump, or an air leak in the system

Question 4

What is a fault of the fuel filters?

Answer 4

The fuel filters are not sensitive to water contamination. Water in the fuel could cause fluctuations/surges in one or both of the engines without any associated fuel filter press or bypass lights

Question 5

Which positions do the fuel selector leavers have and what do they mean?

Answer 5

OFF, DIR, XFD

The valves are closed

Fuel is coming from the respective cell

Fuel is coming from the opposite cell

Question 6

How do you work the fuel priming system?

Answer 6

Placing the switch to FUEL PRIME, will open both engine shut off valves and allow individual engine priming with the PCL in lockout

Placing the FUEL PUMP switch to APU BOOST will open the APU fuel shut off valve and activate the prime boost pump

(There is a Checklist in the PCL)

Question 7

Whats the Main fuel tank Capacity?

Where is the internconnect?

Answer 7

The tanks can hold 590gal (usable) or 4012lbs if fueled with JP-5

The tanks main cell interconnect level is approximately 270-600lbs per side

Question 8

What components does the left tank have?

The right tank?

Answer 8

Left Tank

Single point refuel/defuel, gravity refuel, HIFR, 2 high level shut-off floats, a check valve, a sump drain, and a vent

Right Tank

Two check valves, a sump drain, a vent, an APU fuel line, and the fuel dump system

Question 9

Describe the Auxiliary tanks

What is thier capacity?

Answer 9

External fuel tanks may be installed on the two inboard pylons. They are crashworthy, ballistically hardened tanks with self sealing break away valves to prevent fuel spillage

They are either 120 or 113 gal capacities

Question 10

How fuel quantity measured in the aux tanks?

Answer 10

The fuel level of each aux tank is internally monitored by a single gauge probe. A Low level Thermistor sensor is exposed when the tank is empty

Question 11

How is fuel transfered from the Aux tanks to the main?

Answer 11

A dual transfer/dump pump and dual shutoff valves help transfer fuel to the main tank. The two pumps alternate every time the system is activated.

If one pump of shutoff valve fails, the remaining pump will still be able to transfer fuel

Question 12

What controls the fuel transfer system?

How does it do so and when will it start to transfer fuel?

Answer 12

The Fuel Management Control Panel (FMCP) will control when fuel is transferred to the main tank or when fuel is routed to the aux tank for refueling.

Selecting TRANSFER/MANUAL OVRD will allow the pilot to manually transfer fuel to the main tank. When set to AUTO, fuel will automatically transfer to the main tank at 2640lbs of fuel

Question 13

What hppens if the right tank fills faster than the left?

Answer 13

Because the shut off floats are in the left tank, if the vent if clogged and air is unable to escape the right tank will continue to fill and will not automatically stop refueling. This will lead to the right tank bursting.

If one tank fills faster than the other closely monitor the fuel quantity gauges and stop transferring fuel before the right cell is full (~1700lbs)

Question 14

When can you do unmonitored fuel transfers?

Answer 14

Do not initiate unmonitored fuel transfers from the aux to the main, until the main tank is below 3,200lbs

Question 15

When should you execute the manual fuel transfer check?

Answer 15

When the main fuel tank capacity has decreased approximately 300lbs, check manual fuel transfer to ensure proper transfer

Question 16

How can you jettison the Aux tanks?

Whats the note associated?

Answer 16

External tanks can be jettisoned individually or simultaneously via either all stores jettison or selective jettison

Aux tank jettison is inhibited when there is less than 40gal of fuel (~272lbs) in the aux tanks. Because the fuel gauge for the aux tank reads in 50lb increments, if you are jettisoning the tank and it indicates below 300lbs, selective jettison should be used.

Question 17

When does the FMCP automatically begin to move fuel from the aux to the main?

Answer 17

When the main tank depletes to 2640 lbs

Question 18

In what sequence do the main tanks refuel/defuel?

Answer 18

The main tank is filled first, then the right external, then the left external

Fuel will be taken first from the main tank, then the left external then the right external (opposite)

Question 19

What do the Precheck valves do?

What if the the FMCP is malfunctioning and activating them?

What if the valves are malfunctioning?

Answer 19

The precheck switches and valves allow you test the auto fuel flow securing logic. The valves can be tested inside of the cockpit or outside at the refuleing station.

If the FMCP is causing activation of the precheck valves you will be unable to pressure refuel, however pulling the FUEL MGMT Circuit breaker will allow you to continue.

If one precheck valve fails you are still able to safely take on fuel. If both valves fail, then fuel flow will not automatically stop, the pilot will need to closely monitor fuel level to ensure there is no damage done to the tanks.

Question 20

How is the main tank fuel quantity measured?

Answer 20

Each fuel cell has a capacitance type fuel probe, which uses fuel as a dielectric in order to measure the weight of the fuel and display it in the cockpit.

Two separate and independent fuel low level sensor will illuminate the FUEL LOW caution when fuel in each cell reaches 300lbs. the caution may illuminate and extinguish as fuel washes on and off the sensors.

Question 21

Whats the fuel dump rate?

Answer 21

Minimum of 800lbs per min

Question 22

How do you initiate fuel dumping?

What happens?

What if you are on the ground?

Answer 22

(THERE IS A CHECKLIST FOR THIS) Fuel dumping is activated by the FUEL DUMP switch on the lower console. When activated both transfer/dump pumps are energized and fuel is dumped overboard until the low level sensor is activated (approximately 300lbs each side)

With the FMCP set to TRANSFER/MANUAL OVRD will allow dumping from the external tanks as well

Fuel dump is NOT protected by the Weight-On-Wheels Switch

Question 23

Describe the refueling system

Answer 23

A pressure port is supplied for standard 55psi refueling on the ground with or without electrical power.

It will refuel the main tank first, then the right external, then the left external

Question 24

What makes up the HIFR system and how does it work?

What is it good for besides in flight refueling?

Answer 24

There is a wiggins quick disconnect, a pressure refueling fitting, a precheck switch and a 5 element GO/NO-GO cannister.

The GO/NO-GO cannister will only allow acceptale fuel to pass (so it will filter particulate AND water)