Uncommaned Pwr Changes/Loss of Power/ Uncommanded Prop Feather/Prop Sleeve Touchdown Flashcards

1
Q

What is the most apparent indications of an engine rollback?

A

A reduction in power/thrust

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2
Q

What 4 conditions may normally cause a uncommanded pwr change/loss of power/uncommanded prop feather/ prop sleeve touchdown?

A
  1. Engine rollback due to PMU scheduling
  2. Oil/fuel/engine system contamination
  3. Loss of oil pressure to prop dump solenoid valve
  4. Momentary contact between prop shaft and oil transfer sleeve
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3
Q

What is the cause of an uncommanded prop feather if opening the PROP SYS circuit breaker alleviates the problem?

A

An errant electrical signal to the prop dump solenoid valve

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4
Q

When re-setting the PROP SYS circuit breaker, how long does it take for the prop to become unfeathered?

A

15-20 seconds

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5
Q

What are the normal indications for a uncommanded prop feather?

A

Excessively high torque

Low Np

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6
Q

What are the normal indications for a prop sleeve touchdown?

A

Np fluctuations

Torque fluctuations

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7
Q

How long do the fluctuations normally last after a prop sleeve touchdown?

A

Usually less than 20 seconds

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8
Q

What is one reason the PMU will show only dashed lines for the Np value when experiencing one of the 4 conditions above?

A

If the prop feathers extremely rapidly, the rate of change may exceed the PMU sensor validity and cause the PMU to assume there is a sensor failure, thus providing dashed lined for the Np value.

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9
Q

At what ITT temperature should you use caution around when turning the PMU switch off?

A

> /= 820C

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10
Q

When landing with the PMU switch off, what should you use caution about?

A

Landing distances will be increased due to ground idle not being available when the PMU switch is off. The prop will stay idle at 67%

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11
Q

How long must the Np be below 40% for to be considered stable?

A

3 seconds

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12
Q

If you do not have enough power to complete a PEL, why should you reset the PROP SYS circuit breaker (if pulled)

A

With the PMU off and the PROP SYS circuit breaker pulled, the prop will feather at a slower rate as oil pressure decreases and the feathering spring takes over.
This increased time to feather will cause an increased descent rate and may cause you to be unable to be on profile for the FL.

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13
Q

With the PMU off, does the oil pressure and volume output to the prop pitch control mechanism increase or decrease?

A

It increases

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