Oral Prep - Engine Control

Question 1

What is APR? What arms APR? Once armed how long does it remain armed? What triggers APR to operate and what does it do? How do you know it activated? Does APR arm during a go around situation? How is APR tested? Can you test APR during single engine taxi?

Answer 1

The APR system is armed for takeoff when the engines enter the N1 control range (N1>79%), with the APR switch armed and both ENG SPEED switches ON. Once 14 armed, APR remains active for five minutes, monitoring engine RPM. If a significant loss of RPM is detected at either engine (N1<67.6%), the system automatically commands both engines to increase RPM by 2% minimum (roughly 500 lbs. of thrust). Only the engine operating above 79% N1 will increase thrust. The APR system is not armed during go around situations. The go around thrust values in the FMS and QRH are predicated upon either one or two engines during go around. APR arming is indicated by an advisory APR ARM message. When the APR system is activated, the advisory message will be replaced by a green APR icon in the N1 gauge of the good engine. The activation of APR does not affect thrust lever position. The APR TEST switch allows the system to be ground tested. The two-channel test must be performed with BOTH engines operating. TEST 1 initiates a DCU 1 APR test, and TEST 2 initiates a DCU 2 APR test. The activation of APR power and subsequent increase in N1, although adequate for takeoff performance calculations, does not necessarily equate to full APR power, especially if reduced (FLX) power is used. If necessary, the thrust lever can be advanced to obtain full APR power.

Question 2

What does APR provide?

Answer 2

An automatic power increase on the operating engine in the event of an engine failure, while the APR system is armed.

Question 3

What conditions must be met for the APR system to arm?

Answer 3

APR switch ON, both N1 above 79%.

Question 4

If APR is deferred, how would you know the Takeoff Performance was calculated with APR Inoperative?

Answer 4

It would be listed in the RMKS section below the runway data.

Question 5

What is the function of the Engine Speed switches?

Answer 5

Enables the N1 speed control system and the APR system

Question 6

Engine N1 control (Speed Control) becomes effective when?

Answer 6

With the engine speed switches ON, and the N1 above 79% N1.

Question 7

When is N2 controlling engine speed?

Answer 7

At low power settings (<79% N1), the Fuel control unit controls engine speed mechanically by fuel regulation to achieve the N2 speed.