C90 Powerplant / Props

Question 1

What model of Engines?

Answer 1

Pratt Whitney
PT-6
135A

Question 2

Rated Power

Answer 2

550 SHP

Question 3

Engine Design

Answer 3

Free spinning - not physically connected
Compressor = 3 axial stage + 1 centrifugal stage
Single Power Turbine

Question 4

Combustion Chamber

Answer 4

25% Air burnt, other 75% used to centre flame - cooling
14 nozzles, (StartUp 10 only, other 4 open passsing 40% N1)

Question 5

Oil Pressure moves Props to Fine or Coarse Pitch

Answer 5

FINE

Question 6

Which is Critical Engine

Answer 6

LEFT

Question 7

Engine Start
Hung Or Hot Start

Answer 7

Keep Condition lever out of indent
If ITT approachs 2nd red line start should be aborted, before it passes 2nd red line
Condition Lever ICO
Starter ONLY for the remainder of 40 sec cycle

Question 8

Engine Start Time / Limits

Answer 8

40 Secs On / 60 secs OFF
40 Secs On / 60 secs OFF
40 Secs On / 30 mins OFF

Question 9

What is N1 ?
Limits

Answer 9

Turbine Speed
101.5 %
Transient - 102.6% (
Max Reverse - 88 % (1 min)

Question 10

What is N2 / Np
Limits

Answer 10

Prop Speed
NOT BELOW - 1100, unless feathered
1900 RPM -
1938 RPM - 7 min
1825 RPM - Reverse
2070 - Transient (

Question 11

What is ITT ?
Limits

Answer 11

Interstage Turbine Temp
Station 5 - T5
805
Low Idle - 685 - Only when N1 below 70 %
Start Up - 1090 (2 secs)
Transient - 800 (2 secs)

Question 12

What is P-3

Answer 12

Pressurised Air at Station 3
Bleed Air

Between axial compression and combustion chamber

Question 13

Reduction Gearbox

Answer 13

15:1
37,500 - 1900
High RPM /Low Tq - Low RMP/High Tq

Question 14

Engine Auto Ign

Answer 14

When armed, If Tq drops below 400’/lbs
Ignitors energise - Annunciator

Question 15

Accessory Gear Box - Rear

Answer 15

Starter Gen
Fuel Pump/
Fuel control unit
Oil Scavenger pumps
Optional accessory drives

7 stations with differnet gear ratio’s

Question 16

Accessory Gear Box - Front

Answer 16

Prop Governors
Prop Tach Generator
Overspeed Governor

Question 17

Oil Capacity

Answer 17

3.55 USG
(13.4 Ltrs)

Max Consumption - 1 USG every 10 hrs

Question 18

Oil-Heater Exchange Unit

Answer 18

Use hot oil to heat fuel

Question 19

Oil Temp Range

Answer 19

0 - 99 Deg C
Start - (-40 Deg C)
104 10 min Transient (10 mins)

60-70 Deg C Normal

Question 20

Oil Pressure range

Answer 20

85 Psi - 105 Psi

Question 21

Magnetic Chip Detector

Answer 21

Yellow Annunciator
Monitor engine parameters
Unusual Indications - Shutdown and secure the affected engine
Follow Checklist

Question 22

Fuel Control Unit
FCU

Answer 22

Meters fuel flow
Fuel flow managed using P3 pressure
Higher P3 - Higher fuel flow
Failure of P3 would result in min fuel flow (48%N1) -
Power and condition levers would have no effect on engine speed

Question 23

Prop Levers

Answer 23

Sets desired Propeller RPM
Maintained by adjusting prop pitch

Question 24

Power Levers

Answer 24

Adjusts N1 governor,
Engine Tq
When advanced - N1 - FCU - fuel flow increased
3 Control ranges - Flight / BETA / Reverse separated by lifting over gates

Question 25

Condition Levers

Answer 25

3 control Positions
Cut Off
Low Idle - min 58% N1
High Idle - min 70% N1
(High Idle req’d for Reverse)

Question 26

Propeller - Loss of Oil Pressure

Answer 26

Will cause the propeller to feather (full course Pitch)
Increase in oil Px - Fine/low pitch and reverse

Question 27

Propeller - Governors

Answer 27

2 Governors
Primary Governor &
Overspeed Governor - limit props to 1,976 RPM should the primary governor fail
* See fuel topping governor

Question 28

Propellers -
Fuel Topping Governor

Answer 28

Fuel Topping Governor will usually limit by reducing engine power if RMP exceeds 6% of RPM set bby primary governor
Will reset Prop RPM limit to 95 % for BETA (Grd Fine) & Reverse

Question 29

Low Pitch Stop -
BETA Vslve

Answer 29

Mechanically actuated hydraulic stop