Engines

Question 1

Engines

What are the primary engine indications ?

Answer 1

N1

EGT

Question 2

Engines

Engine vibration indication :
What is the meaning of “BB” as vibration source ?

Answer 2

BB ➝ Broad Band

The source is unknown and average vibration is displayed.

Question 3

Engines

What is the controlling parameter used by the EECs (Electronic Engine Control) ?

Answer 3

N1 RPM

Question 4

Engines

What normally powers the EECs (Electronic Engine Control) ?

Answer 4

A Permanent Magnet Alternator (PMA) driven by the engine gearbox. (2 in total : 1 per engine)
During engine start or if the PMA is unavailable, EEC power is supplied by the airplane (115 VAC power).

Question 5

Engines

In normal mode, the EECs (Electronic Engine Control) continuously compute maximum N1.
What is Maximum N1 ?

Answer 5

Maximum rated thrust available from the engine based on air temperature and pressure altitude.

Question 6

Engines

In alternate mode, how do the EECs (Electronic Engine Control) schedule N1 ?

Answer 6

As a function of thrust lever position.
Therefore, in alternate mode, advancing the thrust levers full forward may result in overboost.
IN ALTERNATE MODE THRUST LEVERS SHOULD NEVER BE FULL FORWARD EXCEPT IN AN EMERGENCY WHERE TERRAIN CONTACT IS IMMINENT.

Question 7

Engines

Which alternate modes do the EECs (Electronic Engine Control) have ?

Answer 7

• Soft ➝ automatic switch by the EECs

* Hard ➝ manual switch by the crew on the EEC overhead panel.

Question 8

Engines

What is TAP ?

Answer 8

TAP ➝ Thrust Asymmetry Protection

It’s an automatic feature that provides protection against asymmetric thrust during takeoff or go-around by limiting thrust on the higher thrust engine.

Question 9

Engines

Does TAP (Thrust Asymmetry Protection) affect certified takeoff performance ?

Answer 9

NO
For airspeeds where TAP does limit thrust, climb gradient is higher than it would be without it.
This is because additional thrust asymmetry creates more drag then the thrust that it ads.

Question 10

Engines

Is TAP (Thrust Asymmetry Protection) available in all EEC modes ?

Answer 10

YES (EECs in NORMAL or ALTN mode), but the Flight Controls need to be in normal mode.

Question 11

Engines

How do the EECs increase engine stall margin during engine acceleration ?

Answer 11

By commanding fuel operated Transient Bleed Valves (TBVs) to open, based on N2 rotor speed.

Question 12

Engines

What consequence does a failure of the TBV in the open position have on the reverser ?

Answer 12

To protect the structural integrity of the reversers from hot gases :
• if the TBV fails open PRIOR to thrust reverser deployment, the associated thrust reverser is inhibited.
• if the failure occurs while the thrust reverser is deployed, it is limited to IDLE.

Question 13

Engines

When do the EECs command Approach Idle ?

Answer 13

• Flaps are commanded 25° or greater or,

* Landing gear is down.

Question 14

Engines

When do the EECs command Icing Idle ?

Answer 14

When Engine Anti-ice is on.

Question 15

Engines

Is there a limit to the number of starts the EEC will attempt per start sequence ?

Answer 15

On the ground ➝ YES : 3 start attempts.
In flight ➝ No limit.

Therefore, Autostart WILL NOT abort a start in flight.

Question 16

Engines

Is there an operating limitation for the engine oil quantity ?

Answer 16

NO, therefore, there are no flight crew procedures based solely on a response to low oil quantity.

Question 17

Engines

Is there a certified vibration limit ?

Answer 17

NO, therefore, there are no specific flight crew actions based solely on vibration indication.

Question 18

Engines

What is the Amber line on the N1 indication ?

Answer 18

The maximum N1.

Question 19

Engines

What alternate source of power can be used to start the right engine if the APU is inoperative ?

Answer 19

FWD external power.
Some load sheds will occur (as always during engine start).
If all 3 GPUs are connected, starting the R engine first will reduce load shed (but it will not speed up the start).

Question 20

Engines

What does the Amber REV indicate ?

Answer 20

The thrust reverser is in-transit.

Question 21

Engines

Do Auto-throttles remain connected in the SOFT or HARD alternate EEC modes ?

Answer 21

YES

Question 22

Engines

How is thrust scheduled in the HARD alternate EEC mode ?

Answer 22

As a function of Thrust Lever Position, according to a preprogrammed thrust schedule.
Therefore, there might be an immediate change of thrust depending on TLP when ALTN is manually selected on the overhead panel (but never a decrease).

Question 23

Engines

If the APU is not available, which power source is needed for Engine Start ?

Answer 23

At least the 2 FWD GPUs.
Some load sheds will occur (as always during engine start).
If all 3 GPUs are connected, starting the R engine first will reduce load shed (but not engine start time).

Question 24

Engines

On the ground with no APU, how many Starter/Generators are used for the first engine start ?

Answer 24

Only one.
Some load sheds will occur (as always during engine start).
If all 3 GPUs are connected, starting the R engine first will reduce load shed.

Question 25

Engines

What is the primary means of cooling engine oil ?

Answer 25

Fuel/Oil Heat exchanger.

Question 26

Engines

What powers REV extension ?

Answer 26

Hydraulics:
L for left REVERSER
R for right REVERSER

Question 27

Engines

What would cause the autostart system to abort the start of an engine ?

Answer 27

• Loss of both starters,
• No N1 rotation,
• No oil pressure rise.

Question 28

Engines

When is X-START displayed in magenta under N2 on the EICAS ?

Answer 28

When current altitude and/or airspeed are outside the windmilling start envelope.
Starter assist is recommended for an in-flight start.

Question 29

Engines

How long is the RUNNING message displayed on EICAS for at the end of engine start ?

Answer 29

30 seconds.

Question 30

Engines

Is simultaneous engine start always allowed on the ground?

Answer 30

No, only when the APU is running and both APU starter/generators are operational.

Question 31

Engines

What thrust do the GE engines deliver ?

Answer 31

74 500 lbs / 33,8 T each