Engines

Question 1

Describe the engines

Answer 1

• Two CFM56-7, dual rotor, axial-flow turbofan.
• N1 rotor consists of a fa, a low pressure compressor and a low pressure turbine
• N2 rotor consists of a high pressure compressor and a high pressure turbine
• N1 and N2 are mechanically independent
• A bleed air powered starter motor is connected to the N2 rotor

Question 2

What regulates each engine ?

Answer 2

Dual-channel EEC

Question 3

What are primary engine indications ?

Answer 3

N1 and EGT

Question 4

What are secondary engine indications and when do they display ?

Answer 4

N2, fuel flow, oil pressure, oil temp, oil quantity and engine vibration.

automatically displayed when:

• the displays initially receive electrical power
• in flight when a engine start level is moved to cutoff
• in flight when the engine N2 RPM is below idle
• a secondary engine parameter is exceeded

Question 5

How does the EEC in normal mode calculate N1 setting?

Answer 5

sensed flight conditions and bleed air demand to calculate N1 thrust setting

Question 6

How many EEC alternate modes?

Answer 6

2: Hard and Soft

Question 7

EEC’s have how many different types of idle?

Answer 7

Ground minimum idle (for ground operations),

flight minimum idle (most phases of flight)

approach minimum idle (if flaps are in landing config or engine anti ice is on)

Question 8

How is fuel heated?

Answer 8

two fuel / oil heat exchangers where IDG oil and main engine oil heat the fuel

Question 9

How does fuel get to the engine?

Answer 9

Fuel Spar Shutoff valve > first stage engine fuel pump > two fuel / oil heat exchangers > fuel filter > second stage fuel pump > hydro mechanical unit (HMU) > Engine fuel shutoff valve

Question 10

How is the oil system pressurized?

Answer 10

Engine driven oil pump

Question 11

How is oil returned to the oil tank?

Answer 11

Scavenge pumps > scavenge filter > main engine oil cooler = oil tank

Question 12

Engine start system requires what?

Answer 12

Pressurized air and electrical power

Question 13

In the GRD position what does the engine use to close the engine bleed air valve and open the start value for pressure to rotate the motor?

Answer 13

Battery power

Question 14

What is the recommend N2 value for engine start?

Answer 14

25%

Question 15

What does the EEC detect during a ground start?

Answer 15

Hot starts, engine stalls, EGT start limit exceedances and wet starts

Question 16

How many ignitors does each engine have ?

Answer 16

2: the left and right ignitors are powered by their respective AC transfer bus

Question 17

What is Auto-relight capability?

Answer 17

whenever the EEC detects an engine flameout both ignitors are activated. a flameout is detected by when an uncommanded rapid decrease in N2 occurs or N2 is below idle RPM

Question 18

What are the two methods of inflight starting ?

Answer 18

Windmill and crossbleed. None on the ground start protections are available in flight

Question 19

Thrust reverser’s are (blank) operated ?

Answer 19

hydraulically operated

Question 20

What system does the hydraulic power for thrust reverse come from

Answer 20

A and B respective from each side. If either A or B fails the standby hydraulic provides operation for the respective side (slower deployment).

Question 21

What keeps the reverses stowed during an uncommanded movement?

Answer 21

The auto-restow circuit opens the isolation value and commands the control valve to the stow position directing hydraulic pressure to stow the reverser.

Question 22

Engine starter cutout speed (400) and (800)

Answer 22

(400) = 46% N2

(800) = 56% N2