Learjet 35 PTM Chapter 5 (Fuel System)

Question 1

How many fuel probes are there per wing? Per tip tank?

Answer 1

3 per wing / 1 per tip tank

Question 2

Unusable fuel is included in the _______ _________ ________ and is not reflected in any fuel quantity indication.

Answer 2

basic empty weight

Question 3

Total usable fuel capacity?

Answer 3

6,238 lbs

Question 4

Tip tank capacity (w or w/o recog light)?

Answer 4

W/O - 1215 lbs
With - 1175 lbs

Question 5

What is the maximum amount of fuel that can be in the tip tank for landing?

Answer 5

925 lbs

Question 6

How much fuel does each wing hold?

Answer 6

1254 lbs

Question 7

What are the purpose of flapper valves?

Answer 7

They allow fuel to flow freely inboard, but limit outboard flow. Hmm… why would that be important?

Question 8

What is the minimum required fuel in the wings for T/O or intentional go-around?

Answer 8

600 lbs

Question 9

What is the maximum fuel imbalance when autopilot is engaged? (FC - 530)

Answer 9

200 lbs

Question 10

The fuselage tank is a rubber bladder and can hold _______ lbs of usable fuel.

Answer 10

1340 lbs

Question 11

Let’s say the pressure builds in the wings and tip tank. What is in the tip tank that will allow fuel to drain overboard?

Answer 11

Two pressure relief valves. One set at 1.0 psi and the other is set at 1.5 psi in case the first valve fails.

Question 12

How many fuel probes are there?

Answer 12

9
(3 per wing, 1 per tip, and 1 in the fuselage tank)

Question 13

Which probe contains a temperature compensator that adjust quantity readings for all switch selections for fuel density change due to temperature?

Answer 13

The inboard probe in the left wing.

Question 14

At how many pounds of fuel will the LOW FUEL annunciator illuminate?

Answer 14

400-500 lbs

Question 15

If you are filling the fuselage, and the LOW FUEL light comes on, will the pumps turn off?

Answer 15

No. There is no protection here. It is the pilots responsibility to make sure this situation never happens.

Question 16

Where is fuel flow taken in the fuel system?

Answer 16

Just before the spray nozzles

Question 17

During engine start, at what % N2 does the wing standby pump deenergize?

Answer 17

45% - 50%

Question 18

Where do the jet pumps in the tip tank take fuel?

Answer 18

They deliver it directly to the inboard baffles where the standby pumps and jet pumps are located in the wing.

Question 19

What do the jet pump switches move?

Answer 19

The motive flow valve.

Question 20

What is the maximum demonstrated fuel imbalance for landing?

Answer 20

600 lbs

Question 21

How do we know if the jet pump in the tip tank has failed?

Answer 21

The only indication is that the wing tank fuel level will start to go down while the tip tank is indicating 600 lbs. (Always make sure to check that the fuel is going down in the tip tank when it gets close to 600 lbs)

Question 22

It is recommended that trapped tip tank fuel be ___________ prior to landing.

Answer 22

jettisoned

Question 23

If DC power is lost, what position will be fuel system valves fail to?

Answer 23

They will remain in their last position when the power is lost.

Question 24

The fuel pressure needs to drop below ______ PSI for the L or R FUEL PRESS to illuminate. The light will extinguish when the pressure increases above _____ PSI.

Answer 24

0.25 PSI, 1.0 PSI

Question 25

The engine driven fuel pump is capable of suction feeding enough fuel to sustain engine operation with both STBY pump and Jet pump inoperative…. However, you need to be at or below __________ ft.

Answer 25

25,000 ft

Question 26

A ___ PSI relief valve is Installed in each main fuel line on the engine side of the main shut off valve.

Answer 26

75 PSI. The valves vent fuel overboard to relieve pressure buildup caused by thermal expansion of trapped fuel when the engines are shut down.

Question 27

Which fuel sumping point must be sumped before every flight?

Answer 27

FUEL VENT DRAIN If you do not sump the fuel vent drain, it is possible to have a blockage of the fuselage ram-air vent line. This would cause a vacuum to build in the fuselage tank and we would not be able to pump that fuel forward.

Question 28

When does the amber FUEL XFLO annunciator illuminate?

Answer 28

Whenever the cross flow valve is fully open.

Question 29

If there is a red FUEL PRESS light illuminated, do not crossflow fuel unless you are below 25,000 feet! What can you do if you are above 25,000 ft to balance fuel?

Answer 29

Asymmetric power settings.

Question 30

What is the fuel transfer rate of the standby pump when cross flowing?

Answer 30

50 lbs per minute

Question 31

How many pounds of fuel will remain in the fuselage tank when gravity feeding?

Answer 31

162 lbs

Question 32

When filling the fuselage tank, a float switch activates when the tank is full. What does the switch cause to happen?

Answer 32

1. Illuminates the green FULL light on the fuel control panel. 2. Deenergizes the standby pumps. 3. Closes the transfer and fuselage valves simultaneously, then closes the crossflow valve.

Question 33

When the XFER-FILL switch is in XFER, and the white empty light comes on, it can indicate one of two things...

Answer 33

1. The tank is empty 2. The fuselage transfer pump has failed.

Question 34

What prevents the transfer pump from over-pressurizing the wings?

Answer 34

A wing fuel pressure switch deenergizes the fuselage transfer pump when the wing fuel pressure reaches 5 PSI. The switch resets and energizes the pump again when the pressure drops below 2.5 PSI.

Question 35

There are two one-way pressure relief valves which separates the left and the right wing fuel tanks. Each valve opens at _____ PSID to equalize fuel pressure between the wing tanks when crossflowing or transferring fuel

Answer 35

1.0 PSID

Question 36

Fuel transfer should begin only after tip fuel is _____ lbs or less.

Answer 36

760 lbs

Question 37

How long does it take for our fuel to be jettisoned from the tip tank?

Answer 37

Approximately 5 minutes

Question 38

If you move the fuel jettison switch to “ON” accidentally, can you move it back to off and stop the dumping of fuel?

Answer 38

Yes

Question 39

What are the 3 limitations when using AVgas?

Answer 39

1. Altitude restricted to 15,000 ft 2. Both Jet pumps and STBY pumps stay on the entire time 3. No more than 500 gallons per 100 hours BONUS: (No taking off with fuel temps below -54 C)

Question 40

What is the maximum fuel imbalance during refueling? And what would you tell the line guy?

Answer 40

125 Gallons. “Fill one side up 125 Gallons, then fill the other wing 250, then 250, then 250, etc…”