Engine Part 2

Question 1

What supplies fuel directly to the main fuel control system?

Answer 1

The main fuel pump (engine driven)

Question 2

What are the two major systems of the main fuel control system?

Answer 2

The computer section and the fuel emtering seciton

Question 3

Describe the main fuel control system’s computer section:

Answer 3

The computer section senses engine inlet air temperature (T2), compressor discharge temperature (P3), engine speed and throttle position to determine the metering valves position and then schedules the correct fuel flow through the entire range of engin operaiton

Question 4

Describe the fuel metering section of the main fuel control system:

Answer 4

It delievers the computer fuel flow to the engine

Question 5

What is an auxiliary function of the main fuel control system?

Answer 5

To schedule the variable geometry system (VGS).

Question 6

How does the main fuel control system schedule the VGS?

Answer 6

Main fuel pump pressure as computed by the main fuel contol computer is diverted to the VGS actuator to operate the variable inlet guide vanes and the bleed air valves.

Question 7

How does the overspeed governor work in the fuel system?

Answer 7

It mechanically monitors engine speed, in the event that an engine exceeds the maximum RPM, the overspeed governor will descrease fuel flow to the engine mainifold to reduce engine speed.

Question 8

What two conditions must be met for the afterburner system to operate?

Answer 8

1. Throttle must be in the MAX range

2. RPM must be stabilized at MIL

Question 9

After afterburner initiation, when does fuel flow to the main afterburner spraybars?

Answer 9

Only when the nozzles are opening, a nozzle feedback cable provides this signal to the afterburner fuel control

Question 10

What is the principle source for fuel after afterburner?

Answer 10

The 16 main afterburner spraybars.

Question 11

By how much does the afterburner augment engine thrust?

Answer 11

By 5 to 40 percent greater than MIL power

Question 12

What portion of the afterburner spraybar system is designed to initiate afterburning and prevent afterburner blowout?

Answer 12

The 4 pilot burner spraybars

Question 13

What does the T38 airstart envelope depend on?

Answer 13

Airspeed, altitude, and air density

Question 14

If you have one engine operating and are attempting an airstart, how many airstart attempts are you limited to?

Answer 14

You are not limited

Question 15

If a dual engine flameout occurs, what engine should you start first? Why?

Answer 15

The right engine. To take advantage of the static inverter powering the right engine autosyn instruments

Question 16

If you start the left engine first (or the right one fails to start) in a dual flameout airstart, what is the only indication of a sucessful start?

Answer 16

Rising RPM and EGT until…

The left generator begins to cut in at the 43 to 48% to view the AC instrument power indications

Question 17

What 4 things should you remember to aid in a succesful airstart?

Answer 17

1. Descend below 25,000 ft. If the engine does not start at an altitude of 25,000, it may start with additional attempts at lower altitudes (10,000 feet or lower)
2. Maintain an airspeed that will produce a minimum of 12% RPM (18-20% is the heart of the airstart envelope at all altitudes)
3. Consider the electrical ignition source avaiable and do not rush the start - allow the full 30-second cycle
4. If at extremely low altitude or a critical need for thrust exists, use the Alternate Airstart/Loss of Thrust (Low Altitude) procedure

Question 18

How long should you leave the throttles in IDLE before aborting an airstart attempt?

What can you check during this wait time?

Answer 18

30 seconds

Recheck the battery switch on

Question 19

What does the T2 sensor do?

Answer 19

Provides an input to the main fuel control and limits fuel flow as a function of inlet temperature

Question 20

What does the fuel flow transmitter measure?

Answer 20

Only main engine flow, not afterburner fuel flow

Question 21

How does the oil cooler work?

Answer 21

When fuel leaves the fuel flow transmitter, it passes through a honeycomb passageway. The hot engine oil passes through adjoining passage ways, allows a heat exchange to occur, cooling down the oil and heating up the fuel.

Question 22

What is the purpose of the pressurization and drain (P&D) valve?

Answer 22

The main fuel P&D valve prevents fow to the fuel manifold until the remainder of the fuel system is up to pressure. During engine shutdown, the P&D opens and dumps unburned fuel from the fuel manifold

Question 23

How does the T38 control fuel flow for afterburner operation?

Answer 23

It is done so by the afterburner fuel control (AFC) unit. The AFC schedules fuel flow to the afterburner main and pilot spray bars as a function of power lever angle and compressor discharge pressure. When the T5 system overrides the hydromechancial control of the variable exahust nozzle, it opens the nozzle. This action causes the AFC computer section to send a signal to the metering section to change the position of the lockout valve, controling fuel flow

Question 24

What is the relationship between the oil pump, tachometer generator, and the T5 alternator?

Answer 24

They all share the same drive shaft

Question 25

What are some common indications of a T5 failure?

Answer 25

High EGT (above 650) and a closed nozzle at or above approx 97% RPM.

Question 26

Will the afterburner light with a T5 system failure?

Answer 26

No

Question 27

If your nozzle is stuck open, what usually results?

Answer 27

Low EGT
High RPM
Reduce amount of available thrust

Question 28

If your nozzle is stuck closed, what usually results?

Answer 28

High EGT
High RPM
Possible of an engine overtemp, especially during rollout after landing

Question 29

At full MAX, what is the approximate fuel flow for each engine?

Answer 29

7300 PPH