PMU

Question 1

Source of power for PMU

Answer 1

PMA (perm magnetic alternator)

Question 2

PMA power supply

Answer 2

32 VAC, which PMU converts to DC

Question 3

When does the PMU switch to 28 VDC from batt bus?

Answer 3

PMA failure, NP below 40-50%

Question 4

What controls the PMU between flight and gd mode

Answer 4

Main Gr WoW (no engine protection for air start)

Question 5

What does the PMU do to N1 above 10,000 MSL

Answer 5

Raises N1 to maintain greater than 80% Np, reducing stress on prop during spins

Question 6

Relation of PCL Position to pwr with PMU on

Answer 6

Linear

Question 7

When will the PMU auto abort start

Answer 7

• Light off has not occurred within 10s of auto/reset
• ITT above 940C for 2s, 870 for 4, 840 for 19
• N1 acceleration to idle is 50% less than normal

Question 8

Is the auto shutdown feature available in flight mode?

Answer 8

No

Question 9

With IOAT between 96-121C and PMU active…

Answer 9

IOAT and ITT data invalid, EDM FAIL displayed

Question 10

PMU offline above IOAT _

Answer 10

121C

Question 11

With PCL at ST READY and Auto/reset, PMU does what?

Answer 11

Activates starter, boost pump and igniters

Question 12

At what N1 will the PMU deactivate starter, boost pump and igniters? (With 10psi fuel px)

Answer 12

50%

Question 13

How to do a manual abort

Answer 13

-PCL off
- reselect auto/reset

Question 14

What does both PMU STATUS and PMU FAIL indicate

Answer 14

PMU system in manual mode (switch off or faulty)

Question 15

PMU status 1 min after landing

Answer 15

Fault conditions not serious enough to revert to manual encountered during flight (report to maintenance)

Question 16

PMU STATIS during flight

Answer 16

• WoW mismatch (or fault)
• PMU Will not revert to gd after landing
• longer landing roll