7. Powerplant

Question 1

What engine is on the B200?

Answer 1

PT6A-42

Question 2

What is the function of the compressor bleed valves?

Answer 2

To prevent compressor stalls and surges in the low N1 range.

Question 3

What would happen to ITT and torque for a constant N1 if a compressor bleed valve stuck open?

Answer 3

ITT would increase and torque would decrease

Question 4

Where are chip detectors located?

Answer 4

At the bottom of each reduction gearbox

Question 5

Where is oil pressure sensed?

Answer 5

By a transmitter in the pressure pump outlet line

Question 6

How are oil pressure and temperature systems powered?

Answer 6

DC power

Question 7

Where do pressure switches sense fuel pressure for annunciators?

Answer 7

Outlet pressure at the engine driven boost (Low pressure) pumps. (10 +/-1 psi)

Question 8

What pressure is supplied to the fuel side of the FCU by the high pressure pump?

Answer 8

800psi

Question 9

What is the function of the spill valve in the FCU?

Answer 9

Referenced to atmospheric pressure, it adjusts fuel flow for cooler high altitude starts

Question 10

How does the FCU purge valve work?

Answer 10

When ignition or start system is energised, purge valve is electrically opened to clear FCU of vapour/bubbles. Excess fuel flows back to nacelle

Question 11

What is the function of the minimum pressurising valve and what does it cause if high pressure pump fails?

Answer 11

It cuts off fuel until fuel pressure builds enough to maintain proper spray pattern (about 70psi).

If pump fails, the valve would close and engine would flame out

Question 12

How is the fuel cutoff valve opened for start?

Answer 12

By the condition lever manually

Question 13

How do igniters behave with switches AUTO IGNITION switch in ARM?

Answer 13

The circuit is connected to an engine torque switch that is normally open when engine is more than 400ft-lb.
If torque drops to 400 or below when armed, ignition will energise to prevent flameout

Question 14

How does the pilot know if the igniters are receiving power?

Answer 14

Green IGNITION annunciators

Question 15

What is the governing range of the primary governor?

Answer 15

1600-2000 RPM

Question 16

What is the overspeed governor set to in normal operation and test?

Answer 16

Normal 2120 RPM

Test 1830-1910 RPM (1870+/-40)

Question 17

What 3 things happen when full reverse is selected?

Answer 17

1. Spool compressor to 83% +/-5 N1
2. Decrease blade angle to min (-9 or -10 deg)
3. Reset FTG to 95% selected RPM

Question 18

What are the low and high idle RPMs?

Answer 18

Low 61% (BB-1444 onwards) or 56% before

High 70%

Question 19

In the reverse range the power lever has three functions:

Answer 19

1. Select blade angle proportionate to aft travel of lever.
2. Select a fuel flow that will sustain selected reverse power.
3. Reset FTG to 95% selected

Question 20

How does the torque limiter work and and at what torque?

Answer 20

At 2368 to 2447ft-lb it will bleed of pneumatic pressure in FCU this reducing metered fuel flow and gas gen power.
Will not prevent pilot from exceeded max certified 2230ft-lb

Question 21

What direction will synchroscope rotate to aid in manual prop synchronisation?

Answer 21

In the direction of the higher RPM engine

Question 22

How is prop feathered when lever is moved to feather?

Answer 22

This mechanically raises governor pilot valve and dumps oil from propellor cylinder.
Counterweights and feather springs move it to feather

Question 23

When is autofeather armed and how is this indicated?

Answer 23

1. System armed.
2. Power levers approx 90% N1.
3. Power in excess of 400ft-lb

L and R AUTOFEATHER lights will illuminate

Question 24

How does autofeather work during an engine failure?

Answer 24

At 400ft-lb the live engine AUTOFEATHER light will extinguish (system disarmed) and at 200ft-lb the failed engine will feather. (And autofeather light will extinguish)

Question 25

How does Autofeather test function work?

Answer 25

With both engines set to 500ft-lb move switch to test. Slowly reduce power on one engine and opposite engine AF light should extinguish at 400ft-lb. Reducing engine AF light should extinguish at 200ft-lb, then begin flashing as feather/unfeather cycle begins. Will not completely feather since engine is producing torque.

Note: In TEST position 90% N1 switches are bypassed.