PMU 1-24

Question 1

What powers the PMU?

Answer 1

The 32 VAC permanent magnet alternator (PMA)

Question 2

The PMU automatically switches to the ________ bus when propeller
RPM drops below __________ or when ______.

Answer 2

28 VDC battery; 40-50% NP; the PMU fails

Question 3

The PMU operates in either _____or ______mode

Answer 3

flight; ground

Question 4

Where is the aircraft weight-on-wheels switches located?

Answer 4

on the main gear struts

Question 5

In ground mode, idle is _________, and in flight mode, idle is _______.

Answer 5

60-61% N1; 67% N1 (min).

Question 6

Above _________, the

PMU raises N1 to maintain NP above _____ to avoid the stress on the propeller during spins

Answer 6

10,000 feet PA; 80%

Question 7

The autostart feature will automatically terminate the ground start sequence if light-off has not occurred within _______ of selecting AUTO/RESET with the STARTER switch (no
start) or if the PMU projects an impending hung or hot start.

Answer 7

10 seconds

Question 8

The PMU will abort an auto start attempt to avoid a hung or hot start in what three cases?

Answer 8

if ITT exceeds:
940 °C for 2 seconds,
870 °C for 4 seconds,
840 °C for 19 seconds

Question 9

An auto abort will occur if N1 acceleration rate to idle is less than _______

Answer 9

50% of normal

Question 10

If IOAT is greater than ______ but less than ______ , the PMU will default to ______ for all PMU functions (including IOAT display).

Answer 10

96°C; 121 °C; 121 °C

Question 11

If IOAT does not exceed ______, the PMU will use the displayed value

Answer 11

96 °C

Question 12

If IOAT exceeds 121 °C, the PMU will do what?

Answer 12

go offline

Question 13

The PMU will reset with IOAT above 121°C.

Answer 13

False.

Question 14

Following the illumination of the ST READY annunciator,
it will remain illuminated for _________, even if the PCL is
moved out of the auto start position.

Answer 14

3 seconds

Question 15

To prevent initiation of
an engine start without auto start protection, ensure the _______ annunciator remains illuminated for more than _______ prior to selecting AUTO/RESET

Answer 15

ST READY; 3 seconds

Question 16

During a start the PMU activates what?

Answer 16

the starter, boost pump, and igniters, and adds fuel at the proper N1

Question 17

At approximately________, the starter and igniters are deenergized and the boost pump is deactivated if fuel pressure is above _______.

Answer 17

50% N1; 10 PSI

Question 18

The PCL may be advanced to IDLE any time N1

is ______

Answer 18

at or above 60%

Question 19

If the ST READY annunciator
extinguishes for any reason during the start sequence, the
PMU will still provide automatic protection

Answer 19

False. It will not

Question 20

If the PCL has been advanced
past the auto start position, the PMU will not cut off fuel to
terminate a start.

Answer 20

True

Question 21

How do you abort a start if the PCL is moved out of ST READY position?

Answer 21

Manually by moving the PCL back to OFF, or if the PCL has not been moved past the IDLE gate, by reselecting the STARTER switch to AUTO/RESET.

Question 22

How to terminate a start if the PCL has been moved past the

IDLE gate?

Answer 22

the PCL must be moved to OFF to abort the start.

Question 23

The PMU also provides engine protection during an airstart.

Answer 23

False.
During an airstart, automatic N1, ITT, and torque limit protection is unavailable, therefore, the pilot must monitor all parameters and abort the start manually if necessary.

Question 24

How to identify that the PMU is in manual mode?

Answer 24

Illumination of both the PMU FAIL and PMU STATUS annunciators indicates the system is in manual
mode.

Question 25

In PMU manual mode the maximum increase in power is ________, and the maximum decrease in power is ______.

Answer 25

280 shp, 550 shp

Question 26

With the PMU in manual mode there will be a step change in NP.

Answer 26

False. No step change in NP will occur since the overspeed governor is automatically reset to 100%

Question 27

In manual mode, the PCL schedules fuel directly to
the engine through the FMU and the pilot must exercise care to ensure N1, temperature, and torque limits are not
exceeded.

Answer 27

True

Question 28

The PMU STATUS light will illuminate 1 minute after landing if?

Answer 28

if fault conditions that are
not serious enough to revert the system to manual are
encountered in flight

Question 29

What does PMU STATUS in flight indicate?

Answer 29

PMU STATUS light illumination in flight indicates a fault in either of, or a mismatch between the
weight-on-wheels switches, and serves to notify the pilot
that the PMU will not revert to ground mode upon landing.

Question 30

With PMU STATUS in flight idle N1 will still shift from flight idle to ground idle upon landing,

Answer 30

False.