Engines And Propellers

Question 1

What type of engines are fitted on the DHC8? What is the HP?

Answer 1

P and W 123D

1950HP But can Uptrim to 2150HP following an EF of the opposite side engine.

Question 2

Which compressor is the accessory gearbox connected to?

Answer 2

The high pressure compressor (NH)

Question 3

What drives the compressors?

Answer 3

Each compressor is driven independently by its own single stage axial turbine.

Question 4

How many fuel nozzles and igniters does the annual reverse flow combustion chamber contain?

Answer 4

14 two stage fuel nozzles and 2 igniters.

Question 5

What do the free power turbines provide power to?

Answer 5

The propeller and propeller Reduction gear box

Question 6

What does the high pressure turbine drive?

Answer 6

The NH compressor which drives the Accessory gear box (Inc DC GEN), engine driven oil pump and engine driven fuel pump.

Question 7

What is the normal (green arc) oil pressure?

What is the min allowable oil pressure?

Answer 7

55 to 65psi

min 40psi

Question 8

What do the power levers control in the constant speed and BETA range?

Answer 8

Engine speed in constant speed range

Engine speed and propeller blade angle in the BETA range.

Question 9

What are the power levers connected to that allows control of the engine speed?

Answer 9

Their MFC mechanical fuel control unit and the PCU

Question 10

How are prop blade angle and RPM controlled when power lever is in the constant speed range?

Answer 10

By the condition levers

Question 11

What normally schedules fuel flow to the engines? If this fails or is off, what schedules fuel? How is this represented to the pilots?

Answer 11

ECU normally (Electronic control unit) acting through the MFC 
MFC Mechanical fuel control without the ECU computer. Represented by MANUAL illuminating on ECU panel.

Question 12

What RPM are props when the power lever is set between flight idle and disc? What occurs when you pull the power levers below disc?

Answer 12

785 between flight idle and disc.

Below disc into reverse, the ECU increases engine power increasing Np and props go from 1.5 degree to -11.

Question 13

What is the propeller restricted range? What prevents the prop from entering this range when the power lever is between flight idle and disc?

Answer 13

Between 500 and 780RPM where continued operation of the propeller is prohibited. The ECU schedules just enough fuel to prevent the props from entering the Restricted range (underspeed governing). There is no protection in the manual mode.

Question 14

What conditions does the engine intake heater require to operate?

Answer 14

Engine running, AC power and OAT 15 Celsius or less.

Question 15

What are the propellers made from? What is the prop diameter and ground clearance?

Answer 15

Aluminium spar, polyurethane foam with fibreglass encasing.
Diameter 4m
Clearance 94cm

Question 16

If metered oil pressure supply is less than the constant oil pressure supply, will the prop be driven to coarse or fine?

Answer 16

Coarse (toward feather)

Question 17

Does a higher metered oil pressure compared to the constant oil pressure drive the prop to coarse/feather or fine/reverse?

Answer 17

Fine/reverse

Question 18

Do aerodynamic loads on prop blades drive it to a high or low blade angle? What system prevents this from occurring should the PCU fail or oil pressure be lost?

Answer 18

Low blade angle (reverse)

The mechanical pitch lock engages to contain blade angle to within 1 degree and speed within 2%.

Question 19

Above what RPM is prop overspeed considered? What occurs if the prop reaches 1250 or 1308RPM? In any case what recalls should be complete

Answer 19

Above 1212
At 1250 metered oil pressure is dumped causing prop to go forward feather. This may result in prop cycling.
Above 1308 a signal is sent to the MFC to reduce fuel flow to reduce engine speed and prop RPM.
Prop overspeed recalls.

Question 20

What is the beta backup system designed to protect the props from doing? What cockpit indication does the pilot get if the beta backup system has engaged?

Answer 20

Designed to prevent props from entering the ground Beta range while the power levers are in the flight range. Flashing on and off of the prop ground range light will indicate this.

Question 21

How does the Beta backup system drive the prop out of the ground range should it occur with power levers in the flight range?

Answer 21

A low blade angle switch sends a signal to the feather valve to dump metered oil pressure which brings the prop towards feather.

Question 22

If the beta lockout system is activated, what system changes occur?

Answer 22

Warning horn sounds
Reversion to Manual mode on the ECU
Np trigger activated above 1000RPM
Engine ignition automatically activated to prevent flame out.

Question 23

What does the Alternate feathering system consist of?

Answer 23

An auxiliary feather pump and a 1.7 quarts auxiliary oil reservoir

Question 24

How does the autofeather system work?

Answer 24

The failed engines SCU (Torque signal condition unit) sends a power Uptrim signal to the ECU of the working engine and the power Uptrim light illuminates. After a 3 second delay the SCU initiates autofeathering of the failed engine by opening the feathering solenoid valve and dumping metered oil pressure.