Twin Otter Dhc6-300

Front 1

<pic DHC6.jpg>

Back 1

This work is in progress, check frequently for updates.

Please email me<color blue> [e-mail] </color>if you see errors, have questions or comments…

Pierre V. Dehaye

Front 2

Vmo
(Kias)

Back 2

Wheels:
166 Kts (Sea Level)
156 Kts (10000')

Floats:
158 Kts (Sea Level)
148 Kts (10000')

Hint 2

Max Operating Speed

Front 3

Va
(Kias)

Back 3

Wheels: 132 Kts

Floats: 135 Kts

Hint 3

Maneuvering Speed

Front 4

Vfe
Flaps 10°
(Kias)

Back 4

Wheels: 103 Kts

Floats: 102 Kts

Hint 4

Max Flaps Extension Speed

Front 5

Vfe
Flaps 10°-37.5°
(Kias)

Back 5

Wheels: 93 Kts

Floats: 95 Kts

Hint 5

Max Flaps Extension Speed

Front 6

Vx
(Kias)

Back 6

Wheels: 87 Kts

Floats: 82 Kts

Hint 6

Best Angle of Climb Speed

Front 7

Vy
(Kias)

Back 7

Wheels: 100 Kts

Floats: 90 Kts

Hint 7

Best Rate of Climb

Front 8

Vyse
Flaps 10°
(Kias)

Back 8

Wheels: 80 Kts

Floats: 86 Kts

Hint 8

Single Engine Best Rate of Climb

Front 9

Vmc
Flaps 10°
(Kias)

Back 9

Wheels: 64 Kts

Floats: 70 Kts

note: with autofeather operational

Hint 9

Minimum Control Speed

Front 10

Vs1
(Kias)

Back 10

Wheels: 66 Kts

Floats: 70 Kts

Hint 10

Stall Speed Takeoff Configuration

Front 11

Vso
(Kias)

Back 11

Wheels: 56 Kts

Floats: 53 Kts

Hint 11

Stall Speed Landing Configuration

Front 12

Vs
(Kias)

Back 12

Wheels: 73 Kts

Floats: ??? Kts

Hint 12

Stall Speed Clean

Front 13

Max Demonstrated
Xwind Component

Back 13

Wheels:
20 kts @ 6 feet
27 kts @ 50 feet

Float:
17 kts

Front 14

Torque
Take-off Max Cont

Back 14

50 PSI

Front 15

Torque
Max Climb Max Cruise

Back 15

50 PSI

Front 16

Torque
Acceleration

Back 16

68.7 PSI
2 Second Max

Front 17

Torque
Max Reverse

Back 17

50 PSI
1 Minute Max

Front 18

Max T5
Take-off Max Cont

Back 18

725 °C

Front 19

Max T5
Max Climb Max Cruise

Back 19

695 °C

Front 20

Max T5
Idle

Back 20

660 °C

at 51% Ng minimum, increase Ng as required to stay below idle temps limit

Front 21

Max T5
Starting

Back 21

1090 °C
2 Seconds Max

Front 22

Max T5
Acceleration

Back 22

825 °C
2 Seconds Max

Front 23

Max T5
Max Reverse

Back 23

725 °C

Front 24

Max T5
Engine Shutdown

Back 24

585 °C

Hint 24

if above 585 °C, advance power levers briefly and retard to increase air flow

Front 25

Ng
Max Take-off Max Cont

Back 25

101.5%

Front 26

Ng
Max Climb Max Cruise

Back 26

102.6%

Front 27

Ng
Max Reverse

Back 27

101.5%

Front 28

Np
Max Take-off Max Cont

Back 28

96%

Front 29

Np
Max Climb Max Cruise

Back 29

96%

Front 30

Np
Acceleration

Back 30

110%

Front 31

Np
Max Reverse

Back 31

91% +/- 1

Front 32

Oil Pressure
Max Take-off Max Cont

Back 32

80 to 100 PSI

Front 33

Oil Pressure
Max Climb Max Cruise

Back 33

81 to 100 PSI

Front 34

Oil Pressure
Idle

Back 34

40 PSI Minimum

Front 35

Oil Pressure
Max Reverse

Back 35

80 to 100 PSI

Front 36

Oil Temperature
Max Take-off Max Cont

Back 36

10 to 99°C

Front 37

Oil Temperature
Max Climb Max Cruise

Back 37

0 to 99°C

Front 38

Oil Temperature
Idle

Back 38

minus 40 to 99°C

Front 39

Oil Temperature
Starting

Back 39

minus 40°C

Front 40

Oil Temperature
Acceleration

Back 40

0 to 99°C

Front 41

Oil Temperature
Max Reverse

Back 41

0 to 99°C

Front 42

Engine Limitations

Back 42

<pic engine limits.jpg>

Hint 42

<pic engine limitations.jpg>

Front 43

T5 Limits

Back 43

Max Take-off/SE: 725°C
Max Climb/Cruise: 695°C
Idle: 660°C
Starting: 1090°C (max 2 Seconds)
Acceleration: 825°C (max 2 seconds)
Max Reverse: 725°C

Hint 43

<pic T5.jpg>
Self-powered by 8 thermocouple probes

Front 44

Torque Limits & Gauge Power

Back 44

Max Take-off/SE: 50 PSI
Max Climb/Cruise: 50 PSI
Acceleration: 68.7 PSI(max 2 seconds)
Max Reverse: 50 PSI (max 1 minute)

Hint 44

<pic torque.jpg>
26 VAC, Spring Loaded to 0

Front 45

Oil Temp Limits & Gauge Power

Back 45

Max Take-off/SE: 10° to 99°C|Max Climb/Cruise: 0° to 99°C|Idle: -40° to 99°C|Starting: -40°C Mini Acceleration: 0° to 99°C°C|Max Reverse: 0° to 99°C

Hint 45

<pic oil Temp.jpg>
28 VDC

Front 46

Oil Pressure Limits & Gauge Power

Back 46

Max Take-off/SE: 80 to 100 PSI
Max Climb/Cruise: 80 to 100 PSI
Acceleration: 40 PSI Mini
Max Reverse: 80 to 100 PSI

Oil Press below 40 PSI is unsafe and requires engine shutdown

Hint 46

<pic oil Press.jpg>
26 VAC
Transmitter on accessory gearbox

Front 47

Oil Pressure Caution Light

Back 47

Labeled “L/R ENGINE OIL PRESS”
Uses separate transmitter
Illuminates between 40 and 42 PSI
Extinguish when oil press reaches 44 to 46 PSI
Powered from Left and Right DC bus
Engine must be shut down below 40 PSI

Front 48

Np Limits & Gauge Power

Back 48

Max Take-off/SE: 96%
Max Climb/Cruise: 96%
Acceleration: 110%
Max Reverse: 91% ±1

100% = 2200 RPM

Hint 48

<pic Np.jpg>
Self-Powered (Tach Generator)

Front 49

Ng Limits & Gauge Power

Back 49

Max Take-off/SE: 101.5%
Max Climb/Cruise: Chart
Acceleration: 102.6%
Max Reverse: 101.5%

Hint 49

<pic Ng.jpg>
Self-Powered (Tach Generator)

Front 50

Fuel Flow Gauge Power

Back 50

<pic Fuel Flow.jpg>
26 VAC

Front 51

Fuel Gauge & Probes Power

Back 51

<pic Fuel Quant.jpg>
115 VAC

Front 52

Engine Gauges

Back 52

<pic engine gauges1.jpg>

Front 53

Aircraft Dimensions

Back 53

Wing Span: 65 Ft
Length: 51 ft 9 in
Height: 18 ft 7 in
Tail Span: 20 ft 8 in
Prop Ø: 8 ft 6 in
Prop grd clearance: 60 in
Distance between floats: 13 ft 4 in

Hint 53

<pic seaplane dimentions.jpg>

Front 54

Aircraft Weights

Back 54

Wheel-Plane

Maximum Ramp Weight: 12,500 lbs
Maximum Takeoff Weight: 12,500 lbs
Maximum Landing Weight: 12,300 lbs

Hint 54

Sea-Plane

Maximum Ramp Weight: 12,585 lbs
Maximum Takeoff Weight: 12,500 lbs
Maximum Landing Weight: 12,500 lbs

Front 55

FWD Baggage Weight

Back 55

280 lbs
(18lbs WX Radar)

Front 56

AFT Baggage Weight

Back 56

408 lbs
(92 lbs AC unit)

Front 57

Main Cabin Floor Loading Limits

Back 57

200 lbs/Ft²

Front 58

AFT & FWD Baggage
Floor Loading Limits

Back 58

100 lbs/Ft²

Front 59

Main Cabin Door Size

Back 59

50 x 56 inches

Front 60

CG Range

Back 60

Land Plane: 20% to 36%

Seaplane: 25% to 32%

Front 61

Land Plane
CG Limit & Caution Zone

Back 61

Limit: FWD 20.0 AFT 36.0
Caution: FWD 22.0 AFT 34.0

Front 62

Seaplane
CG Limit & Caution Zone

Back 62

Limit: FWD 25.0 AFT 32.0
Caution: FWD 27.0 AFT 30.0

Front 63

FWD Caution Zone
Land Plane

Back 63

All Empty Seats Must Be Forward

Hint 63

In the case of a loaded aircraft forward caution zone condition, the proviso is: “All Empty Seats Must Be Forward”. This means that any unoccupied seats must be in the most forward section, in this case Section “A”, and that all other cabin seats must be occupied.

Front 64

FWD Caution Zone
Seaplane

Back 64

<color red>PROHIBITED</color>

All Empty Seats Must Be Forward cannot be met as the rearmost seats (row 7) are not installed

Hint 64

Proviso for seaplanes with 17 passenger seating configuration: In the case of a loaded seaplane with a forward caution zone condition, the proviso: “All Empty Seats Must Be Forward”, cannot be met as the rearmost seats (row 7) are not installed. This means that the airplane cannot be operated in the forward caution zone with any seats occupied in Section “A”, (row 1). If a projected aircraft loading results in a forward caution zone condition, the aircraft load must be redistributed to bring the center of gravity aft of the forward caution zone.

Front 65

AFT Caution Zone
Land Plane

Back 65

All EmptySeats Must Be Aft

Hint 65

In the case of a loaded aircraft aft caution zone condition, the proviso is: “All Empty Seats Must Be Aft”. This means that any unoccupied seats must be in the most rearward section, in this case, Section “D”, and that all other cabin seats must be occupied.

Front 66

AFT Caution Zone
Seaplane

Back 66

All Empty Seats Must Be Aft

Hint 66

In the case of a seaplane with a 17 passenger seating configuration and an aft caution zone loading condition, the proviso: “All Empty Seats Must Be Aft” is met as the rearmost seats (row 7) are not installed, however, all seats located forward of Section “D” (row 6) must be occupied.

Front 67

Flight Controls

Back 67

<pic Flight Controls.JPG>

Front 68

Ailerons

Back 68

. Attached to outboard fore Flap.
. Geared servo tab on each side, move in opposite direction to provide aerodynamic assistance.
. Electric trim tab on left side.
. Wing fence enhance aileron control at low airspeed.
. Ailerons travel increases as flaps comes down.

Front 69

Aileron Trim

Back 69

. On Left Aileron.
. Powered from<color red> L 28VDC Bus.</color>
. C/B labeled "AIL TRIM ACT"

Front 70

Flaps

Back 70

<color red>
. Outboard Fore Flap: 0° to 26°
. Inboard Fore Flap: 0° to 40°
. Inboard Trailing Flap: 0° to 60°

. Overall Flap Operation: 0° to 37.5°</color>

Hint 70

If loss of Hydraulic Pressure, flaps position will remain as long selector is not moved.

Front 71

Elevators

Back 71

. Not equipped with Servo Tab.
. Wiper Seals at leading edge of elevator to enhance control at low airspeed.
. Trim Tab on left side.
. Flap-Elevator interconnect tab on right side.

Front 72

Flap-Elevator Interconnect Tab

Back 72

<color red>
. On the right side of elevator.
. Minimize pitch change during flap operation.
. Up and Down 12°.
. Automatic, can not be controlled by pilot.</color>

Front 73

Rudder

Back 73

. Trim Tab on top.
. Servo Tab on Bottom

Front 74

Vortex Generators

Back 74

. No go Item if one is missing
. 16 on top, 15 on bottom

Front 75

Tire Pressure

Back 75

. Main Gear: 38 psi
. Nose Gear: 32 psi

Front 76

Main Gear

Back 76

. Shock Absortion is provided by Urethane Blocks
. Cleveland Brakes

Hint 76

<pic main gear.jpg>

Front 77

Nose Gear

Back 77

. Nosewheel steers 60° either side
. NW Steer lever is connected to steering actuator via cables
. Nose gear is centered in flight by notch when nose gear leg is fully extended after take off
. Check nosewheel centered after T/O and after landing.
. If nosewheel is not centered after T/O, it may drift to a full deflection during flight

Hint 77

<pic nose gear.jpg>

Front 78

Steering System

Back 78

<pic nose steering.jpg>

Hint 78

<pic nose gear1.jpg>

Front 79

Brake System

Back 79

<pic brake sys.jpg>

Front 80

Electrical System

Back 80

. Primarily a 28VDC system.
. AC power is used for some avionics, engine instruments and the fuel quantity indication.
. 28 VDC is Single wire (Except the fire detection system).
. Primary DC power comes from the starter generators.
. There is a battery (starts and backup).
. 2 static inverters provide 115VAC and 26VAC .
. 7 electrical buses.

Front 81

Buses

Back 81

7 Buses
<color red>
1.L 28VDC Bus
2.R 28VDC Bus
3.Aux Bat Bus
4.Bat/Ext Pwr Bus
5.Hot Bat Bus
6. 26VAC Bus</color>

Hint 81

<pic Electrical sys.jpg>

Front 82

Left 28 VDC Bus

Back 82

1. DC Voltmeter
2. Hydraulic Oil Pump
3. Prop Auto FX
4. Fire Detect/Ext L+R
5. Boost Pump FWD & AFT #1
6. R Gen Fail Caution Light

Hint 82

<pic Buses.jpg>

Front 83

Right 28 VDC Bus

Back 83

1. Prop Overspeed Gov
2. Xfeed Fuel Valve
3. Beta System
4. Boost Pump FWD + AFT #2
5. L Gen Fail Caution Light

Hint 83

<pic Buses.jpg>

Front 84

Hot Bat Bus

Back 84

1. Entrance Light
2. Baggage Light

Hint 84

<pic Buses.jpg>

Front 85

26 VAC Bus

Back 85

1. Torque Gauges
2. Fuel Flow Indicator
3. Oil Pressure Indicator
4. Gyros

Hint 85

<pic Buses.jpg>

Front 86

115 VAC Bus

Back 86

<color red>
1. Fuel Quant Gauges
2. Capacitance gauging probes
3. Attitude Indicator
4. Directional Gyro</color>

Hint 86

<pic Buses.jpg>

Front 87

Battery

Back 87

<color red>
. 24 Volts
. 36 Amp/Hour </color>
. Acid Lead

Hint 87

<color red>
BAT power provided to L28VDC bus when MBR is energized.</color>
Battery located under aft baggage compartment.
Venting system below battery.
Connected directly to L28VDC bus.

Front 88

Bat/Ext Switch

Back 88

<color red>Energize MBR or EPR</color>

Front 89

Starter Generator

Back 89

<color red>
. 28.5 VDC 200 Amps</color>
. Functions as both starter and DC Generator
. One S/G can supply aircraft

Hint 89

Most PWR Consumption:
. Air Conditioning
. W/S Heater
. Prop Deice
. Pitot Tube

Front 90

Generator Operations

Back 90

<color red>
. Idle + 15%Ng (65Ng)
. Back to idle only when load is below 0.5</color>

Hint 90

FCU will attempt to maintain speed (T5)

Generator must be selected off before shutdown for lower T5

Front 91

Generator Switches

Back 91

<color red>
1. Provides control voltage to close RCR
2. Excites shunt field to increase Gen. output</color>

Front 92

Generator Reset Limits

Back 92

2 Attempts Max

Front 93

Generator Load Sharing

Back 93

<color red>
Must be within 10% or 20 Amps
(.1 on Load Meter)</color>

Hint 93

*open bus tie to prevent overloading of one generator

Front 94

Generator Limitations

Back 94

0 - 0.5 _ Idle Ng _ All Temps _ T5
0.5 - 1.0 _ Idle Ng + 15% _ All Temps _ T5
0.8 _ Ground from 45 to 125°F _ Generator Cooling
1.0 _ Ground up to 45°F _ Generator Cooling
1.0 _ Flight up to 125°F _ Generator Cooling

Hint 94

<pic Generator Limitaions.jpg>

Front 95

Generator Caution Lights

Back 95

<color red>
. Indicates that the RCR is open
. Lights powered form opposite bus
(“L GENERATOR” powered from R28VDC bus)
(“R GENERATOR” powered from L28VDC bus)
</color>

Front 96

DC Loadmeter

Back 96

. Indication selector switch (L GEN, BAT, R GEN)
. Indicates -1.0 to +1.0
<color red>. 1.0 = 100 Amps when in BAT
. 1.0 = 200 Amps when in GEN</color>
. Measures current to or from BAT (BAT selected)
. Measures Generator loads on (GEN selected)

Hint 96

<pic Volts Amps meter.jpg>

Front 97

DC Voltmeter

Back 97

. Indicates form 0 to 30 volts
. Connected directly to <color red>L28VDC bus</color>
. C/B labeled VA on main C/B panel

Hint 97

<pic Volts Amps meter.jpg>

Front 98

Reverse Current relays (RCR)
Purposes

Back 98

<color red>
1. Connect the Battery or External Power to the Starter Generator during Engine Starting

2. Connect the Starter generators to the DC buses when brought online</color>

Front 99

RCR
4 Conditions to Close

Back 99

<color red>
1. Generator output greater than 22 Volts
2. Generator voltage must be .5V higher than the battery
3. Must be a positive Current
4. Flow of current must be from the Generators to the Battery</color>

Hint 99

Located in the cabin roof in the Generator Control Box

Front 100

RCR
Open

Back 100

If a generator fails to maintain the required voltage, The RCR will sense the current has begun to flow in a reverse direction and open to prevent the generator to function as a starter

Hint 100

<color red>
The Generator Caution Light indicates that the RCR has open
</color>

Front 101

Starter Limitations

Back 101

. 25 Sec On 1 Minute Off
. 25 Sec On 1 Minute Off
. 25 Sec On 30 Minute Off

Hint 101

<pic Starter limitations.jpg>

Front 102

Starting Engines

Back 102

. 15% Ng minimum (16% to 18% with good Battery, 20% or more with GPU).

. Battery must be recharged to 0.4 on the Loadmeter before starting 2nd engine.

. Starts with external power preferred.

Hint 102

<pic Engine Start Procedures.jpg>

Front 103

Cross Generator Starting

Back 103

Prohibited

Front 104

Power Distribution C/B

Back 104

. Distributes power to Left and Right DC busses.
. Stops loss of bus if one line has fault.
<color red>. 6/50 amp 12/30amp.</color>
. C/B at both ends of line.
. If one pops, reduce the loads due to less available amps.
<color red>. IF ONE POPS DO NOT RESET.</color>
. Indicates a serious problem with line.

Front 105

RCCB
Reverse Current Circuit Breaker

Back 105

. Protects BAT from overheat during charging.
<color red>. 450amp C/B.</color>
. Generators will remain online.
. If Tripped, Loadmeter reads 0.
. Can be missed by pilot.
. Also opens MBR.
. Can be reset in flight.

Front 106

Current limiters

Back 106

. Current limiters provide same function as RCCB.
. Consists of SIX, 75 amp slow blow fuses (450 amp total).
. 3 located in the control box, 3 in the battery area.
. If an excess of 450 amps exist for a prolonged time current limiters will melt.

Front 107

AC System

Back 107

. 2 static inverters provide AC power to aircraft.
. Each inverter can provide both 115VAC and 26VAC.
#1 inverter receives input power from L28VDC bus.
#2 inverter receives input power from R28VDC bus.
. Alternate use daily.

. The inverters provide power to:<color red>
1. Fuel flow indication
2. Oil pressure Indication
3. Fuel Quantity
4. Torque pressure (spring loaded to 0)
5. May also power DG, AI, FD, HIS</color>

. AC gauges will stick in position if power is lost
. Pilot must be aware of which inverter is selected

Front 108

400 Cycle Caution Light

Back 108

. Operated by 400 CYCLE FAIL RELAY.
. Fuse located on A/C fuse panel.
<color red>. Fuel quantity test can also be used to test 115VAC.</color>
. Llight Powered from L28DC bus

Front 109

Fuel Tanks

Back 109

<color red>
.FWD tank right engine
.AFT tank left engine</color>
.4 cells per tank
.Filler ports in cell #1 & #7
.Collector cells are #4 & #5

Hint 109

<pic fuelsys.jpg>

Front 110

Collector Cells

Back 110

Collector Cells contains:

. 2 Boost Pumps
. 1 Low Level Float Switch
. 1 Fuel Capacity Probe (All Cells)
. 1 Flapper Valve (All Cells Except cell #1 & #7)
. 1 Fuel Drain
. 2 Vents (all Cells)

Hint 110

<pic fuelsyscol.jpg>

Front 111

Advantage of Collector Cells

Back 111

. Minimize CG shift as Collector Cells is located in center of aircraft

. Collector Cell is always full so Boost Pump is always covered

Front 112

Motive Flow

Back 112

. Boost pump outflow and Pressure exceed engine needs. (450 lbs @ 22 psi, engine fuel pump needs 5 psi)
Excess outflow and pressure is used to transfer fuel to the collector cell thru the ejector pump. One way flapper valves in collector cell prevents fuel from returning to other cells. When collector cell is full, fuel flow is blocked by a float level control valve at top of input stand pipe

Hint 112

<pic fuelsys1.jpg>

Front 113

Motive Flow Failure

Back 113

. If ejector pump becomes blocked or level-control float becomes stuck in closed position, the fuel level will be equal in all cells. This will cause the <color yellow>FUEL LOW LEVEL</color> Caution light to illuminate with Aprox 330 lbs of fuel left in the Tank. Avoid large pitch attitudes. try to switch boost pump off and on to unclogged jet pump.

Hint 113

<pic fuelsys2.jpg>

Front 114

<color yellow>FUEL LOW LEVEL</color>
Caution Light

Back 114

<color red>
. 75 lbs remains in FWD Tank
. 110 lbs remains in AFT Tank</color>

Front 115

Fuel Tank Vents

Back 115

. Each fuel cells have 2 Vents on top left and right side.

. The vent is designed to maintain a slight positive pressure in each cells to prevent collapse of flexible tank

Front 116

Fuel Quantity Gages

Back 116

. Powered from 400 cycle, 115 VAC Bus. If AC power is lost, the fuel gauge will remain at quantity (AC lies, DC dies), Note time of failure and calculate fuel endurance based on fuel flow

. When TEST button is pressed, fuel Quant should fall to Zero and come back to correct fuel Quant when depressed

Front 117

Fuel Flow Indicator

Back 117

. Powered from 400 cycle, 26 VAC Bus

Front 118

Boost Pumps

Back 118

<color red>
. #1 FWD & AFT Boost Pumps are powered from L 28VDC Bus
. #2 FWD & AFT Boost Pumps are powered from R 28VDC Bus</color>

Front 119

Boost Pumps Operation

Back 119

. When boost pump switch is on, #1 pump operates and #2 pump remains off
. Boost pump #2 will operate automatically thru an automatic changeover if pump # 1 pressure falls below 2 psi, #1 boost pump caution light will illuminate.

Front 120

Boost Pump Caution Lights

Back 120

. Energized by pressure switch in each boost pump when pressure is below 2 psi
. Powered from L and R DC Bus
. All 4 caution lights should be illuminated when switches are off and fuel selector on NORM. (only way to check pressure switch)
.

Front 121

Boost Pump Testing

Back 121

. When boost pump switch is press down in the test position, it simulates a failure of the #1 pump.
. #1 boost pump caution light should illuminate and #2 pump should automatically start operating
. Listen for running pump and #2 pump caution light should be extinguished

Front 122

Failure of #1 Boost Pump

Back 122

. #1 Boost pump caution light will illuminate
. #2 Boost pump caution light will illuminate momentarily then extinguish when pressure rises
. Automatic change over will turn on the #2 pump to maintain pressure
. Do no select Stanby Pump Switch (see story next page)
. Use abnormal checklist

Hint 122

<pic story.jpg>

Front 123

Simultaneaous Failure of #1 Boost Pump
& Changeover System

Back 123

. #1 boost pump caution light will illuminate
. #2 Boost pump caution light will illuminate also
. Use apropriate Standby Pump Switch (Use abnormal checklist)

Front 124

Simultaneaous Failure of #1 Boost Pump
& Pressure Switch

Back 124

. No Caution Light will Illuminate
. If above 8000 feet with high power stetting, flameoute is posible
. This double failure could be detected after completion of the engine shutdown checklist as the boost pump caution lights will not illuminate (after boost pump switch is moved to off).
. It would be possible to restart the engine by selecting the stanby pump switch.

Front 125

Fuel Shutoff Valve

Back 125

. Located behind engine nacelle at firewall
. Only use in emergency situations
. DC Power must be available for valve to function

Front 126

Fuel Crossfeed

Back 126

. Supply both engine from on tank (Both on FWD, Both on AFT)
. Not possible to transfer fuel from one tank to another
<color red>. Powered from the R DC Bus</color>
. When testing Fuel Crossfeed, listen to make sure the valve comes back to close position.

Front 127

Fuel Tank Capacity

Back 127

. FWD: 1235 lbs (181 US Gal)

. AFT: 1341 lbs (197 US Gal)

Front 128

Power Plant

Back 128

<color red>PT6A-27</color>

. PT= Propeller turbine
. 6= Engine family
. A= Two stage reduction gearbox
. 27= Specific model

Hint 128

. 330 lbs W/O prop and acc.
. Reverse flow, free turbine
. Engines are identical
. Three stage axial compressor
. Single stage centrifugal compressor

Front 129

Main Station Numbers

Back 129

<color red>
. 1 Air inlet
. 2 Entry to compressor
. 2.5 Between axial and centrifugal
. 3 Compressor exit
. 5 Between turbine wheels</color>

Hint 129

<pic Main Staitions.jpg>

Front 130

Advantages of free turbine

Back 130

. Starting
. Propeller speed
. Hot section inspections
. Prop strike

Hint 130

<pic free turbine.jpg>

Front 131

Advantages of reverse flow engine

Back 131

FOD protection
Shorter and lighter

Hint 131

<pic reverse flow.jpg>

Front 132

FLAT-RATING

Back 132

. PT6A-27 engine rated at 680 SHP (715 ESHP)
. Flat-rated to <color red>620 SHP</color>
. Flat-rated for structural and aerodynamic reasons
. No “hard stop” (Torque limited to 50 by pilot)
. Advantages of flat-rating
<color red>. Maintain 620 SHP at ISA+18ºC</color>
. More T5 margin at T/O power

Front 133

ENGINE SECTIONS

Back 133

1. Air inlet
2. Compressor
3. Combustor
4. Turbine
5. Exhaust
6. Reduction gearbox
7. Accessory gearbox

Hint 133

<pic Main Staitions.jpg>

Front 134

AIR INLET

Back 134

. Located at rear of engine (reverse flow)
. Mesh screen for FOD protection
. 2 size screens (fine used for desert operations)
. 180º change causes centrifugal separation

Front 135

COMPRESSOR

Back 135

. Progressively increases air pressure
. Supplies air for:<color red>
Combustion
Bearing seal pressurization
Engine cooling
Airframe pneumatics</color>
.First stage blades are titanium (FOD)
. 100% Ng is equal to 37,500 rpm, Idle is 19,500 rpm
. Two third of HP is used to run the compressor section, one third to run the propeller

Hint 135

<pic compressor.jpg>

Front 136

BLEED AIR

Back 136

. Bleed air taken from station 3 of the engine
. 103 psi @ 280ºC at T/O power

. Bleed air is used for:<color red>
Airframe deice
Cabin heat
Intake deflectors</color>

. The FCU, WF governor, and compressor bleed valve also use P3 air Controlled by two switches labeled BLEED AIR

Hint 136

<pic bleed air1.jpg>

Front 137

COMPRESSOR BLEED VALVE

Back 137

. Do not confuse with Bleed air valve
<color red>Necessary because axial is more efficient at low GG speeds</color>
. Automatic
. Compares P2.5 (axial) and P3
. Closes at approximately 85% GG
. Can malfunction open or closed
<pic Compressor efficiency.jpg>

Hint 137

<pic bleed valve.jpg>

Front 138

COMBUSTION CHAMBER

Back 138

. Supported by fuel nozzles and igniters
. 2 flow reversals prior to chamber
. only 25% of compressed air is burned
. Most air isused for cooling

Hint 138

<pic Combustion.jpg>

Front 139

TURBINES

Back 139

. Two turbines, CT and PT (Compressor and Power)
. Guide vanes smooth flow
. Turbines rotate opposite to each other (Torque)
. Free turbine

Front 140

EXHAUST

Back 140

DH provided exhaust not Pratt & Whitney
Recovers “Jet thrust” equal to 38 SHP

Front 141

REDUCTION GEARBOX

Back 141

. 2 planetary reduction gears
. Converts high RPM/Low torque to Low/High
<color red>. 15:1 </color>reduction ratio
<color red>. 100% NP = 2,200 RPM</color> (96%=2,112)(76%=1,675)
. Indication form tachometer or “Tach Generator”

Hint 141

<pic gear box.jpg>

Front 142

TORQUEMETER

Back 142

. Provides primary engine power indication
.Uses engine oil pressure to measure Power
. Installed on gear box assembly
. Sending unit transmits info to cockpit

Hint 142

<pic torquemeter.jpg>

Front 143

Calculate SHP

Back 143

SHP = (Np x Tq)/172.17

eg: (2112 x 50) / 172.17 = 613.34

Front 144

ACCESSORY GEARBOX

Back 144

The accessory gearbox drives:<color red>
Starter generator
Oil pressure pump
Oil scavenge pumps
Engine fuel pump
Fuel Control Unit
Ng tach Generator</color>
Twin Otter has two empty pads

Hint 144

<pic accessory pads.jpg>

Front 145

Oil is used for?

Back 145

<color red>
. Cooling
. Lubricating engine bearings
. Fuel Heating
. Prop Control
. Torquemeter</color>

Front 146

Oil System

Back 146

Dry-sump system
oil is constantly scavenge back to the oil tank.

Hint 146

<pic oil system.jpg>

Front 147

Oil Quantity & Type

Back 147

. Total oil tank capacity is <color red>2.3 US Gal</color> of which 1.5 Gal. is usable. The difference (.7 Gal) is used for expansion.

. Maximum allowable oil consumption is one quart per 10 hours.
. Oil Level should be checked 10 min after shutdown.

. Engine uses synthetic turbine oil.

Front 148

Flight in Volcanic ash

Back 148

Oil & Filter Change

Front 149

Oil Pressure caution light illuminates @?

Back 149

Between 40 and 42 PSI

Extinguish when rise back between 44 and 46 PSI

Front 150

High-Pressure Fuel Pump

Back 150

. Located on accessory gear box, gear type pump.
. Output pressure is directly proportional to Ng speed:<color red>
. At 12% Ng, pressure is Aprox 75 PSI.
. At T/O power(101.5% Ng) pressure is aprox 850 PSI</color>

Hint 150

. Needs at least 5 psi from the boost pumps to avoid cavitations.
<color red>. If supply pressure is below 5 PSI for more than 10 hours, overhaul of the high pressure pump is required.</color>

Front 151

FCU
(Fuel Control Unit)

Back 151

. The FCU is mounted on and driven by High-pressure fuel pump.
. FCU is divided in 3 sections:<color red>
. Governing
. Computing
. Metering</color>

Hint 151

<pic FCU.jpg>

Front 152

FCU
Governing

Back 152

. Governing section controls the gas generator rpm (Ng)
. Power levers provides mechanical input to the Ng Gov.

Front 153

FCU
Computing

Back 153

. Computing section provides a pneumatic signal to the governing section.
. It receive input from P3 and Pa, these signals are modified into Py and Px and transmitted to Ng Gov and Np Gov.
. Any imbalance will affect metered fuel to the combustion chamber.

Front 154

FCU
metering

Back 154

. Changes in Pneumatic signal will increase or decrease fuel metering to accelerate or decelerate the gas generator or maintain steady state.

Front 155

FUEL CONTROL UNIT (FCU)

Back 155

. FCU mounted on HP fuel pump
. Power levers provides <b>mechanical</b> input
. Gas generator provides RPM input

. 3 section of FCU:<color red>
-Governing
-Computing
-Metering</color>

. Governing controls Ng speed
. Computing section converts mechanical inputs into <b>pneumatic</b> signals
. Pneumatic signal controls fuel metering to engine
. Computing section also receive P3 and Pa
. FCU adjusted to provide 52% Ng Idle at ISA

Front 156

FCU
Minimum Idle

Back 156

. At ISA condition, the minimum fuel flow will only provide an idle speed of 48% Ng, the Governing section of the FCU provides additional fuel to maintain an Ng of 52%

* at pressure altitude of 3000', the minimum fuel will provide 52% Ng

Hint 156

<pic FCU1.jpg>

Front 157

Fuel is used for?

Back 157

<color red>
. Starting
. Acceleration
. Deceleration
. Steady State</color>

Hint 157

Automatic compensation is provided for Altitude, Temperature and Aircraft speed

Front 158

Fuel Cut-Off Valve

Back 158

. Fuel cut-off valve is controlled by fuel levers.
. It receives fuel from FCU and allows fuel to flow to Combustion Camber

Front 159

Fuel Nozzles

Back 159

<color red>
. 14 nozzles
. 10 primary, 4 secondary (reduces T5 during start)</color>
. 2 pressure cracking valves
. Primary opens at 12% NG
. Secondary opens at 38% NG

Hint 159

<pic Fuel sys.jpg>

Front 160

Reduction Gear Box

Back 160

. Converts high rpm/low torque into high torque/low rpm.
<color red>. 15:1</color> reduction ratio, 2 planetary reduction gear.
. @ 76% Np, power turbine is turning at 25,080 rpm and prop at 1,672 rpm

Front 161

Engine Instalations

Back 161

<pic Engine Instalation1.jpg>

Hint 161

<pic Engine Instalation2.jpg>

Front 162

Prop Blade Angle

Back 162

<pic blade angles1.jpg>

Hint 162

<pic blade angles.jpg>

Front 163

Prop Blade Angle
FX

Back 163

87°

Hint 163

Mechanical stop in prop dome
Can be adjusted

Front 164

Prop Blade Angle
Constant Range Speed

Back 164

75° to 96°

Hint 164

Prop speed is controlled by CSU

Front 165

Prop
Contact Angle

Back 165

21°

Hint 165

Point at witch low pitch nut contacts and move feedback ring

Front 166

Prop
Prime Blade Angle

Back 166

17°

Hint 166

Feedback ring moves beta valve.
Oil flow to CSU is restricted
(Unlimited Hydraulic Low Pitch Stop)

Front 167

Prop
Idle Blade Angle

Back 167

11°

Hint 167

Blade angle when beta valve when power levers at Idle

Front 168

Prop Blade Angle
Beta Backup activation

Back 168

9°

Hint 168

Beta Backup Solenoid activated
(Microswitch)

Front 169

Prop Blade Angle
Beta Range - Idle Power
(Idle Null)

Back 169

11° to minus 2°

Hint 169

Blade angle changes with no change in Ng (51%)

Front 170

Prop Blade Angle
Reverse

Back 170

0° to minus 15°

Hint 170

Beta valve

Front 171

Prop Blade Angle
Max Reverse

Back 171

minus 15°

Hint 171

Mechanical stop in prop dome
Can not be adjusted
Fuel to FCU is limited by Nf Gov due to reset arm (91%±1)

Front 172

Propeller Oil Supply

Back 172

. CSU oil pump increase oil pressure from 85 psi to <color red>385 psi</color> to overcome forces of propeller counterweights

Front 173

Oil path in Prop System

Back 173

1.Gov pump (385 psi)
2.Pressure relief valve
3.Beta backup Valve
4.Beta Valve
5.CSU (pilot valve)
6. T to Overspeed Gov and AutoFX
7.To the Prop (thru transfer sleeve)

Hint 173

<pic on Speed.jpg>

Front 174

CSU
Constant Speed Unit

Back 174

. Three ranges:
Under speed
Overspeed
On Speed

Between 75% and 96% Np.

Hint 174

<pic GOV.jpg>

Front 175

Slight Overspeed
Overspeed

Back 175

Slight Overspeed
<pic slight overspeed.jpg>

Hint 175

Overspeed
<pic over speed.jpg>

Front 176

On Speed
Reverse

Back 176

On Speed
<pic on Speed.jpg>

Hint 176

Reverse
<pic reverse.jpg>

Front 177

Constant Speed Range
(Np Gov or Prop Gov)

Back 177

. Prop RPM is controlled by the prop governor.
. Prop Governor is controlled by prop levers.
. CSU adjust blade angle as needed to achieve selected RPM.

Front 178

Beta Range

Back 178

. Prop Blade Angle is controlled by Beta Valve.
. Beta Valve is controlled by Power Levers.
. Pilot can directly select prop blade angle with power levers.
. Prop is in beta range when ever the RPM is less than selected on prop levers

Front 179

Idle Null

Back 179

. Aprox the 1st inch behind the gate on Power levers.
. Blade angle between 11° and minus 2° with gas Generator at Idle(51%)
. Rearwards movement of power levers will cause the beta valve to supply more oil to . Prop, decreasing the blade angle from 11° to minus 2°, which is equal to 0 thrust

Front 180

BETA BACKUP SYSTEM

Back 180

. Electrical valve, only operated during abnormality
. System includes:<color red>
-Valve
-Feedback ring Microswitch
-Power lever Microswitch (test)</color>
-Power supplied from <color red>R 28VDC</color>
-Operates between<color red>11 and 9º</color> blade angle

<color red>. "Beta Sys" C/B located on main C/B panel, 2nd row 2nd one down</color>

Hint 180

<pic Beta sys CB.jpg>

Front 181

Beta Valves Differences

Back 181

<pic beta vavles differences.JPG>

Front 182

Beta Disarm Light

Back 182

.A blocking relay disarm the beta backup system briefly when the power lever are brought back to idle (microswitch) and the propeller blades are finer than 9°. This prevents unwanted cycling of the beta backup solenoid and give time to the prop blade to "catch-up" with the power levers.

Hint 182

<pic beta disarm AutoFX beta light.jpg>

Front 183

Overspeed Governor

Back 183

. In hydraulic series with CSU
<color red>. Preset at 101.5% NP</color>
. Limits prop RPM if CSU fails

. OVERSPEED GOV. TEST momentarily resets governor to 70%

Hint 183

Perform it's function by dumping oil in the sump, allowing the counterweights and feathering spring to coarsen the blade angle.

Front 184

Fuel Topping Governor
(Nf Gov)

Back 184

. Integral part of the CSU
. Sends pneumatic signal to the FCU

. Two Functions:

<color red> -In Forward flight, Nf Gov protects against overspeed situation by dumping Py from the FCU.</color> It causes the FCU to limit fuel supply to the engine if prop rpm speed is greater than 6% Np selected on prop levers.

<color red> -In Reverse, Nf Gov ensures that the prop never reaches 96% Np</color> and the Np Gov is always under speed so it does not interfere with the oil supply sent to the prop by the beta valve.

.When power levers move aft of the gate, the Nf Gov is mechanically reset to 5% below the selected prop gov rpm. (Nf Gov Reset Arm)

Front 185

AutoFX

Back 185

. Automatically feathers propeller of failing engine
. System includes 6 main component
<color red>
1. Power lever microswitches
2. Torque pressure switches
3. Solenoid valves
4. Isolation relay
5. Indication lights
6. Cockpit toggle switch</color>

Hint 185

AutoFX Test
<pic autofx2.jpg>

Front 186

Conditions for AutoFX
to Arm

Back 186

3 conditions to ARM system
<color red>
1. System must be selected On
2. Torque must rise to 20-30 psi
3. Power levers must be forward (88% NG)</color>

Hint 186

AutoFX Armed
<pic autofx1.jpg>

Front 187

Conditions to AutoFX
a Prop

Back 187

2 conditions to Autofeather
<color red>
1. System must be ARMED
2. Torque must fall below 11 psi (2 sec)</color>

Hint 187

AutoFX Engine Failure
<pic autofx3.jpg>

Front 188

Micro-Switches

Back 188

Reset Prop:
Right Pwr Lever(1), Left Prop Lever(1).

Auto FX:
Both Pwr Levers(2)

Beta Backup Disable:
Twist Grip(1)

Starter:
Fuel Levers(2)
(Low RPM, High Torque to High RPM, Low Torque)

Front 189

Micro-Switched in Twist Grip

Back 189

Disable Beta backup system micro-switch @ the prop to allow prop to go into reverse

Front 190

Fuel Levers

Back 190

.2 positions ON or OFF.
.Preloaded to require deliberate action.
.Mechanically connected to Cutoff valve.

Hint 190

Generators:
<color red>2 Microswitches
Low RPM, High Torque to High RPM, Low Torque</color>

Front 191

Prop Levers

Back 191

.Labeled INCREASE and FEATHER<color red>
.Governs between 75% and 96%
.Mechanically connected to CSU
.Mechanical reverse interlock </color>
.Pilot must push up and aft for Feather

Hint 191

Reset Props:<color red>
1 Microswitch in Left Prop Lever
(less than 71%)</color>

Front 192

Power Levers

Back 192

Labeled “THROTTLE”
Anti-reverse stop (twist)
Prop interlock

Mechanically connected to:<color red>
Cam
FCU
NF Governor
Beta reverse valve
Feedback ring</color>

In forward range only affects FCU
In reverse affects FCU, NF, AND Beta valve

Hint 192

Reset Props<color red>
1 Microswitch in Right Power Lever
(less than 91%)</color>

Auto FX:<color red>
2 Microswitches, one in each power lever
(above 88% Ng)</color>

Beta Backup Disarm:<color red>
1 Microswitch controlled by twist grip</color>

Front 193

Engine Controls

Back 193

<pic commands.jpg>

Hint 193

<pic levers.jpg>

Front 194

PWR LEV
TEST

Back 194

Push-to-test green switchlight,
twist twist-grip, green light should come on.
<color red>Testing integrity beta disarm microswitch. </color>

Hint 194

<pic Tests.jpg>

Front 195

Fire Detecting Test

Back 195

Spring loaded switch labeled “TEST”

Testing completes the circuit of one thermal detecting probe in each nacelle.

T handles should illuminate and bell should ring.

Hint 195

<pic T Handles.jpg>

Front 196

Prop Gov Test

Back 196

Prop Gov Test switch hydraulically reset the overspeed governor to<color red> 70% instead of 101.5%</color>

At Idle, hold switch up.
Advance power levers slowly.
Observe props govern at 70%

(should govern 70% @ 20 psi torque on standard day)
<color red>(Overspeed Gov can not be MELed)</color>

Hint 196

<pic overspeed gov.jpg>

Front 197

Beta Range Test

Back 197

Beta Range Test switch bypass micro switch in twist grip and power is maintained to beta backup valve, even if twist-grip is twisted.

Therefore, the beta backup system activates to prevent the blades going less than 9°

Hint 197

<pic Tests.jpg>

Front 198

Auto FX Test

Back 198

1. Prop Auto FX On, SEL light illuminated.
2. Power levers, advance to 20 psi torque.
3. Lift Auto FX test switch, ARM light illuminated.
4. Retard one power lever until ARM light goes out and prop FX.
5. Release switch, prop will unFX.
6. Repeat other prop

Hint 198

Test mode maintains power lever Microswitches closed
regardless of power lever position

Front 199

Hydraulic Fluid

Back 199

<color red>. Reservoir holds 2/3 US gallon</color>
. MIL-H-5606 Red


. Prior checking Fluid Level, flaps must be retracted and gauges on flight deck must read Zero.

Front 200

Hydraulic System

Back 200

. Provides Hydraulic power for Flaps, Brakes and Steering.
. Gear type pump operated by a<color red> 28 VDC motor (Left Bus)</color>.
. 35 Amp C/B labeled "HYD OIL PUMP" on main panel.
. C/B warning light on panel.
. Double Acting Hand pump, Handle stowed behind co-pilot seat.

Hint 200

<pic Hydraulic sys.jpg>

Front 201

Hydraulic System
Damping accumulators

Back 201

<color red>. 2 Accumulators, 1 for brakes, 1 for the rest.</color>
. Act as pressure bank (reserve) and shock damper.
. Recharged with nitrogen at <color red>750 PSI.</color>

Front 202

Hydraulic System
Working Pressure

Back 202

<color red>. 1225 PSI to 1625 PSI.
. Pressure relief valve opens at 1750 PSI.</color>

Front 203

Fire Protection System

Back 203

. Provides fire detection in each nacelle.<color red>
. System operates off the L 28VDC.</color>
. Uses Freon or Halon extinguishing agent.
. Overheat in nacelle will illuminate FIRE PULL handle.
. Pulling handle will discharge bottle into the accessory gearbox area.
. Cannot be crossfed.

Hint 203

<pic fire bottle.jpg>

Front 204

Fire Detection Probes

Back 204

. Consists of 4 thermal detectors in each nacelle.
. Detectors contain bimetallic strips.
. Strips will complete the circuit when heated.<color red>
. 2 forward detectors close at 450º F.
. 2 rear detectors close at 300º F.</color>

Hint 204

<pic Fire Detection.jpg>

Front 205

Fire Detection TEST

Back 205

. Spring loaded switch labeled “TEST”
. Testing completes the circuit of one thermal detecting probe in each nacelle.
. T handles should illuminate and bell should ring.

Hint 205

<pic T Handles.jpg>

Front 206

Fire Detection
Electrical Design

Back 206

<color red>
. Powered from the L28VDC Bus.
. Fire detection system uses a dual wire circuit (not airframe for -)
. System provides redundancy in the event of a ground fault.
. If a short circuit exists the “FIRE DET FAULT IND” C/B will pop.
. If C/B pops, the positive side of the circuit will become negative and the negative side will now be positive.</color>

Hint 206

<pic Fire electric sys.jpg>

Front 207

Fire Detection C/B

Back 207

. 6 Magnetic C/B
. If the “FIRE DET FAULT IND” C/B is found popped, test the system:

If the system tests OK:
a ground fault exists and should be repaired ASAP, but fire detection will be available.


If the system does not test OK;
reset C/B and attempt the test again, If the system still will not test fire detection capability is lost.

Hint 207

<pic fire cb1.jpg>

Front 208

Fire Bottle
Indicating Disk

Back 208

<color red>RED</color> = Thermal Relief Valve
<color yellow>YELLOW</color> = Fire Handle has being pulled

Hint 208

RED disk can be MELed
Check bottle charge befor 1st flight of the day

Front 209

Bleed Air

Back 209

. Bleed air is taken from station 3 of the engine
. 103 psi @ 280ºC at T/O power

. Bleed air is used for:<color red>
Airframe deice
Cabin heat
Intake deflectors</color>
Auto Pilot (old System and very rare)

. The FCU, WF governor, and compressor bleed valve also use P3 air Controlled by two switches labeled BLEED AIR

Hint 209

<pic bleed air1.jpg>

Front 210

Bleed Air Uses

Back 210

. Auto Pilot (Old System and very rare)
. Cabin Heat
. Airframe Deicing
. Intake Deflectors

Hint 210

<pic bleed air2.jpg>

Front 211

Intake Deflectors

Back 211

. Bleed air pickup is upstream from the the bleed air valve, bleed switches
does not have to be on the on position to operate intake deflectors
. Extended pneumatically, Held in place mechanically, Retracted electromechanically
. One switch, EXTEND, OFF, RETRACT, spring loaded to center OFF.
. Indication next to torque gauge will show EXT when extended
. Ng must be above 80% before extending deflectors
. Small door at the rear of the engine nacelle opens and allow snow, ice, particles to exit.
. Torque will drop about 1 or 2 lbs when deflectors are extended

Front 212

Intake Deflectors Operation

Back 212

. EXTEND: Switch must be held in EXTEND position, it takes about 3 sec for EXT indication.
The switch should be held an extra 3 to 5 seconds after EXT indication.

. RETRACT: Switch is moved to the RETRACT position, it may be released when EXT indication disappears

Front 213

Seaplane Differences

Back 213

1. Placards with new operating limitations.
2. Prop Blade Latches.
3. Stall warning vanes lowered.
4. Stall stripe extra (right wing).
5. Elevator downspring to increase longitunal static stability.
6. Aux vertical sea fins to increase directional stability.
7. Left rudder travel reduced to 14°.
8. Rudder gear servo tab modified to 3°-9° instead of 5.5°-10°.
9. Structural modification are added to fuselage for float load.
10. PT6 Seaplane cams on FCU.
11. Blue line VMO change.