PMU system & associated malfunctinos/emergencies

Question 1

The PMU & PIU automatically control the propeller ________(pitch) & propeller ________ (Np)

Answer 1

blade angle; speed

Question 2

True/False: The PMU controls the propeller RPM by varying the propeller blade angle with oil pressure through the PIU

Answer 2

True

Question 3

With the PMU functioning, the mechanical overspeed governor modulates oil pressure to the propeller pitch change piston to limit Np below _____, while the electronic governor will maintain Np at ¬¬¬______.

Answer 3

106%; 100%

Question 4

If PMU function is lost/deactivated, the mechanical flyweight overspeed governor modulates oil pressure to the propeller pitch change piston to maintain Np at or below___.

Answer 4

100±2%

Question 5

Feathering the prop…when the engine is shutdown, the PMU sends a signal to the ________valve to drain propeller oil pressure.

Answer 5

prop servo valve

Question 6

If the rate of change of propeller RPM occurs and exceeds the PMU sensor validity check limit, what will happen?

Answer 6

It will switch to manual mode

Question 7

Does the PMU energize & de-energize the igniters when the ignition switch is positioned accordingly?

Answer 7

Yes

Question 8

The PMU converts the 32 VAC from the PMA to ______.

Answer 8

DC

Question 9

True/False: The PMU automatically switches to the 28 VDC battery bus when propeller RPM drops below 40-50% Np, or when the PMA fails.

Answer 9

True

Question 10

PMU ground mode vs. flight mode

Answer 10

ground= 60-61%; Flight=67% (minimum)

Question 11

Above ______, the PMU raises N1 to maintain Np above 80% to avoid stress on the propeller during spins.

Answer 11

10,000’ft PA

Question 12

The PMU will auto abort an impending hot/hung start if ITT exceeds 940°C for _____, 870°C for _____, or 840°C for ______.

Answer 12

2 seconds, 4 seconds, 19 seconds

Question 13

True/False: The PMU automatic shutdown feature is enabled for airstarts.

Answer 13

False, the auto feature is disabled

Question 14

For engine starts, the PMU receives inputs from the ______ sensor located in the engine inlet plenum.

Answer 14

IOAT

Question 15

If IOAT is greater than 96°C, but less than 121°C, the PMU will default to ______°C for all PMU functions

Answer 15

121°C

Question 16

A dedicated ___________, mounted on the reduction gearbox, powers the PMU

Answer 16

Permanent magnet alternator (PMA)

Question 17

If the IOAT exceeds 121°C, what happens to the PMU?

Answer 17

It goes offline & will not reset until below 121°C

Question 18

If the ST READY light extinguishes during engine start, does the PMU auto abort function still work?

Answer 18

No, the start must be manually aborted

Question 19

Illumination of both PMU ____ & PMU ______ annunciators indicates the system is in manual mode.

Answer 19

FAIL, STATUS

Question 20

Why would the PMU STATUS light illuminate 1 minute after landing?

Answer 20

There were fault conditions not serious enough in-flight

Question 21

Why would the PMU STATUS light illuminate during flight?

Answer 21

Mismatch between the weight on wheels switch & notifies pilot the PMU will not revert to ground mode upon landing

Question 22

With the PMU off, the _______ will not automatically activate & must be selected manually for a PMU OFF AIRSTART.

Answer 22

Igniters

Question 23

True/False: PMU FAILURE-before resetting PMU or switching to OFF, set power at lowest practical to minimize power shift.

Answer 23

True

Question 24

Can you reset a PMU STATUS light in-flight?

Answer 24

No, the PMU detected a discrepancy w/the weight on wheels switch