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<pic DHC6.jpg>
This work is in progress, check frequently for updates.

Please email me<color blue> pvjd71@gmail.com </color>if you see errors, have questions or comments…

Pierre V. Dehaye
Vmo
(Kias)
Wheels:
166 Kts (Sea Level)
156 Kts (10000')

Floats:
158 Kts (Sea Level)
148 Kts (10000')
Max Operating Speed
Va
(Kias)
Wheels: 132 Kts

Floats: 135 Kts
Maneuvering Speed
Vfe
Flaps 10°
(Kias)
Wheels: 103 Kts

Floats: 102 Kts
Max Flaps Extension Speed
Vfe
Flaps 10°-37.5°
(Kias)
Wheels: 93 Kts

Floats: 95 Kts
Max Flaps Extension Speed
Vx
(Kias)
Wheels: 87 Kts

Floats: 82 Kts
Best Angle of Climb Speed
Vy
(Kias)
Wheels: 100 Kts

Floats: 90 Kts
Best Rate of Climb
Vyse
Flaps 10°
(Kias)
Wheels: 80 Kts

Floats: 86 Kts
Single Engine Best Rate of Climb
Vmc
Flaps 10°
(Kias)
Wheels: 64 Kts

Floats: 70 Kts

note: with autofeather operational
Minimum Control Speed
Vs1
(Kias)
Wheels: 66 Kts

Floats: 70 Kts
Stall Speed Takeoff Configuration
Vso
(Kias)
Wheels: 56 Kts

Floats: 53 Kts
Stall Speed Landing Configuration
Vs
(Kias)
Wheels: 73 Kts

Floats: ??? Kts
Stall Speed Clean
Max Demonstrated
Xwind Component
Wheels:
20 kts @ 6 feet
27 kts @ 50 feet

Float:
17 kts
Torque
Take-off Max Cont
50 PSI
Torque
Max Climb Max Cruise
50 PSI
Torque
Acceleration
68.7 PSI
2 Second Max
Torque
Max Reverse
50 PSI
1 Minute Max
Max T5
Take-off Max Cont
725 °C
Max T5
Max Climb Max Cruise
695 °C
Max T5
Idle
660 °C

at 51% Ng minimum, increase Ng as required to stay below idle temps limit
Max T5
Starting
1090 °C
2 Seconds Max
Max T5
Acceleration
825 °C
2 Seconds Max
Max T5
Max Reverse
725 °C
Max T5
Engine Shutdown
585 °C
if above 585 °C, advance power levers briefly and retard to increase air flow
Ng
Max Take-off Max Cont
101.5%
Ng
Max Climb Max Cruise
102.6%
Ng
Max Reverse
101.5%
Np
Max Take-off Max Cont
96%
Np
Max Climb Max Cruise
96%
Np
Acceleration
110%
Np
Max Reverse
91% +/- 1
Oil Pressure
Max Take-off Max Cont
80 to 100 PSI
Oil Pressure
Max Climb Max Cruise
81 to 100 PSI
Oil Pressure
Idle
40 PSI Minimum
Oil Pressure
Max Reverse
80 to 100 PSI
Oil Temperature
Max Take-off Max Cont
10 to 99°C
Oil Temperature
Max Climb Max Cruise
0 to 99°C
Oil Temperature
Idle
minus 40 to 99°C
Oil Temperature
Starting
minus 40°C
Oil Temperature
Acceleration
0 to 99°C
Oil Temperature
Max Reverse
0 to 99°C
Engine Limitations
<pic engine limits.jpg>
<pic engine limitations.jpg>
T5 Limits
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
<pic T5.jpg>
Self-powered by 8 thermocouple probes
Torque Limits & Gauge Power
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)
<pic torque.jpg>
26 VAC, Spring Loaded to 0
Oil Temp Limits & Gauge Power
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
<pic oil Temp.jpg>
28 VDC
Oil Pressure Limits & Gauge Power
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
<pic oil Press.jpg>
26 VAC
Transmitter on accessory gearbox
Oil Pressure Caution Light
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
Np Limits & Gauge Power
Max Take-off/SE: 96%
Max Climb/Cruise: 96%
Acceleration: 110%
Max Reverse: 91% ±1

100% = 2200 RPM
<pic Np.jpg>
Self-Powered (Tach Generator)
Ng Limits & Gauge Power
Max Take-off/SE: 101.5%
Max Climb/Cruise: Chart
Acceleration: 102.6%
Max Reverse: 101.5%
<pic Ng.jpg>
Self-Powered (Tach Generator)
Fuel Flow Gauge Power
<pic Fuel Flow.jpg>
26 VAC
Fuel Gauge & Probes Power
<pic Fuel Quant.jpg>
115 VAC
Engine Gauges
<pic engine gauges1.jpg>
Aircraft Dimensions
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
<pic seaplane dimentions.jpg>
Aircraft Weights
Wheel-Plane

Maximum Ramp Weight: 12,500 lbs
Maximum Takeoff Weight: 12,500 lbs
Maximum Landing Weight: 12,300 lbs
Sea-Plane

Maximum Ramp Weight: 12,585 lbs
Maximum Takeoff Weight: 12,500 lbs
Maximum Landing Weight: 12,500 lbs
FWD Baggage Weight
280 lbs
(18lbs WX Radar)
AFT Baggage Weight
408 lbs
(92 lbs AC unit)
Main Cabin Floor Loading Limits
200 lbs/Ft²
AFT & FWD Baggage
Floor Loading Limits
100 lbs/Ft²
Main Cabin Door Size
50 x 56 inches
CG Range
Land Plane: 20% to 36%

Seaplane: 25% to 32%
Land Plane
CG Limit & Caution Zone
Limit: FWD 20.0 AFT 36.0
Caution: FWD 22.0 AFT 34.0
Seaplane
CG Limit & Caution Zone
Limit: FWD 25.0 AFT 32.0
Caution: FWD 27.0 AFT 30.0
FWD Caution Zone
Land Plane
All Empty Seats Must Be Forward
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.
FWD Caution Zone
Seaplane
<color red>PROHIBITED</color>

All Empty Seats Must Be Forward cannot be met as the rearmost seats (row 7) are not installed
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.
AFT Caution Zone
Land Plane
All EmptySeats Must Be Aft
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.
AFT Caution Zone
Seaplane
All Empty Seats Must Be Aft
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.
Flight Controls
<pic Flight Controls.JPG>
Ailerons
. 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.
Aileron Trim
. On Left Aileron.
. Powered from<color red> L 28VDC Bus.</color>
. C/B labeled "AIL TRIM ACT"
Flaps
<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>
If loss of Hydraulic Pressure, flaps position will remain as long selector is not moved.
Elevators
. 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.
Flap-Elevator Interconnect Tab
<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>
Rudder
. Trim Tab on top.
. Servo Tab on Bottom
Vortex Generators
. No go Item if one is missing
. 16 on top, 15 on bottom
Tire Pressure
. Main Gear: 38 psi
. Nose Gear: 32 psi
Main Gear
. Shock Absortion is provided by Urethane Blocks
. Cleveland Brakes
<pic main gear.jpg>
Nose Gear
. 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
<pic nose gear.jpg>
Steering System
<pic nose steering.jpg>
<pic nose gear1.jpg>
Brake System
<pic brake sys.jpg>
Electrical System
. 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.
Buses
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>
<pic Electrical sys.jpg>
Left 28 VDC Bus
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
<pic Buses.jpg>
Right 28 VDC Bus
1. Prop Overspeed Gov
2. Xfeed Fuel Valve
3. Beta System
4. Boost Pump FWD + AFT #2
5. L Gen Fail Caution Light
<pic Buses.jpg>
Hot Bat Bus
1. Entrance Light
2. Baggage Light
<pic Buses.jpg>
26 VAC Bus
1. Torque Gauges
2. Fuel Flow Indicator
3. Oil Pressure Indicator
4. Gyros
<pic Buses.jpg>
115 VAC Bus
<color red>
1. Fuel Quant Gauges
2. Capacitance gauging probes
3. Attitude Indicator
4. Directional Gyro</color>
<pic Buses.jpg>
Battery
<color red>
. 24 Volts
. 36 Amp/Hour </color>
. Acid Lead
<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.
Bat/Ext Switch
<color red>Energize MBR or EPR</color>
Starter Generator
<color red>
. 28.5 VDC 200 Amps</color>
. Functions as both starter and DC Generator
. One S/G can supply aircraft
Most PWR Consumption:
. Air Conditioning
. W/S Heater
. Prop Deice
. Pitot Tube
Generator Operations
<color red>
. Idle + 15%Ng (65Ng)
. Back to idle only when load is below 0.5</color>
FCU will attempt to maintain speed (T5)

Generator must be selected off before shutdown for lower T5
Generator Switches
<color red>
1. Provides control voltage to close RCR
2. Excites shunt field to increase Gen. output</color>
Generator Reset Limits
2 Attempts Max
Generator Load Sharing
<color red>
Must be within 10% or 20 Amps
(.1 on Load Meter)</color>
*open bus tie to prevent overloading of one generator
Generator Limitations
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
<pic Generator Limitaions.jpg>
Generator Caution Lights
<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>
DC Loadmeter
. 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)
<pic Volts Amps meter.jpg>
DC Voltmeter
. Indicates form 0 to 30 volts
. Connected directly to <color red>L28VDC bus</color>
. C/B labeled VA on main C/B panel
<pic Volts Amps meter.jpg>
Reverse Current relays (RCR)
Purposes
<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>
RCR
4 Conditions to Close
<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>
Located in the cabin roof in the Generator Control Box
RCR
Open
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
<color red>
The Generator Caution Light indicates that the RCR has open
</color>
Starter Limitations
. 25 Sec On 1 Minute Off
. 25 Sec On 1 Minute Off
. 25 Sec On 30 Minute Off
<pic Starter limitations.jpg>
Starting Engines
. 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.
<pic Engine Start Procedures.jpg>
Cross Generator Starting
Prohibited
Power Distribution C/B
. 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.
RCCB
Reverse Current Circuit Breaker
. 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.
Current limiters
. 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.
AC System
. 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
400 Cycle Caution Light
. 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
Fuel Tanks
<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
<pic fuelsys.jpg>
Collector Cells
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)
<pic fuelsyscol.jpg>
Advantage of Collector Cells
. Minimize CG shift as Collector Cells is located in center of aircraft

. Collector Cell is always full so Boost Pump is always covered
Motive Flow
. 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
<pic fuelsys1.jpg>
Motive Flow Failure
. 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.
<pic fuelsys2.jpg>
<color yellow>FUEL LOW LEVEL</color>
Caution Light
<color red>
. 75 lbs remains in FWD Tank
. 110 lbs remains in AFT Tank</color>
Fuel Tank Vents
. 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
Fuel Quantity Gages
. 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
Fuel Flow Indicator
. Powered from 400 cycle, 26 VAC Bus
Boost Pumps
<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>
Boost Pumps Operation
. 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.
Boost Pump Caution Lights
. 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)
.
Boost Pump Testing
. 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
Failure of #1 Boost Pump
. #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
<pic story.jpg>
Simultaneaous Failure of #1 Boost Pump
& Changeover System
. #1 boost pump caution light will illuminate
. #2 Boost pump caution light will illuminate also
. Use apropriate Standby Pump Switch (Use abnormal checklist)
Simultaneaous Failure of #1 Boost Pump
& Pressure Switch
. 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.
Fuel Shutoff Valve
. Located behind engine nacelle at firewall
. Only use in emergency situations
. DC Power must be available for valve to function
Fuel Crossfeed
. 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.
Fuel Tank Capacity
. FWD: 1235 lbs (181 US Gal)

. AFT: 1341 lbs (197 US Gal)
Power Plant
<color red>PT6A-27</color>

. PT= Propeller turbine
. 6= Engine family
. A= Two stage reduction gearbox
. 27= Specific model
. 330 lbs W/O prop and acc.
. Reverse flow, free turbine
. Engines are identical
. Three stage axial compressor
. Single stage centrifugal compressor
Main Station Numbers
<color red>
. 1 Air inlet
. 2 Entry to compressor
. 2.5 Between axial and centrifugal
. 3 Compressor exit
. 5 Between turbine wheels</color>
<pic Main Staitions.jpg>
Advantages of free turbine
. Starting
. Propeller speed
. Hot section inspections
. Prop strike
<pic free turbine.jpg>
Advantages of reverse flow engine
FOD protection
Shorter and lighter
<pic reverse flow.jpg>
FLAT-RATING
. 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
ENGINE SECTIONS
1. Air inlet
2. Compressor
3. Combustor
4. Turbine
5. Exhaust
6. Reduction gearbox
7. Accessory gearbox
<pic Main Staitions.jpg>
AIR INLET
. 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
COMPRESSOR
. 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
<pic compressor.jpg>
BLEED AIR
. 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
<pic bleed air1.jpg>
COMPRESSOR BLEED VALVE
. 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>
<pic bleed valve.jpg>
COMBUSTION CHAMBER
. Supported by fuel nozzles and igniters
. 2 flow reversals prior to chamber
. only 25% of compressed air is burned
. Most air isused for cooling
<pic Combustion.jpg>
TURBINES
. Two turbines, CT and PT (Compressor and Power)
. Guide vanes smooth flow
. Turbines rotate opposite to each other (Torque)
. Free turbine
EXHAUST
DH provided exhaust not Pratt & Whitney
Recovers “Jet thrust” equal to 38 SHP
REDUCTION GEARBOX
. 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”
<pic gear box.jpg>
TORQUEMETER
. Provides primary engine power indication
.Uses engine oil pressure to measure Power
. Installed on gear box assembly
. Sending unit transmits info to cockpit
<pic torquemeter.jpg>
Calculate SHP
SHP = (Np x Tq)/172.17

eg: (2112 x 50) / 172.17 = 613.34
ACCESSORY GEARBOX
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
<pic accessory pads.jpg>
Oil is used for?
<color red>
. Cooling
. Lubricating engine bearings
. Fuel Heating
. Prop Control
. Torquemeter</color>
Oil System
Dry-sump system
oil is constantly scavenge back to the oil tank.
<pic oil system.jpg>
Oil Quantity & Type
. 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.
Flight in Volcanic ash
Oil & Filter Change
Oil Pressure caution light illuminates @?
Between 40 and 42 PSI

Extinguish when rise back between 44 and 46 PSI
High-Pressure Fuel Pump
. 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>
. 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>
FCU
(Fuel Control Unit)
. The FCU is mounted on and driven by High-pressure fuel pump.
. FCU is divided in 3 sections:<color red>
. Governing
. Computing
. Metering</color>
<pic FCU.jpg>
FCU
Governing
. Governing section controls the gas generator rpm (Ng)
. Power levers provides mechanical input to the Ng Gov.
FCU
Computing
. 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.
FCU
metering
. Changes in Pneumatic signal will increase or decrease fuel metering to accelerate or decelerate the gas generator or maintain steady state.
FUEL CONTROL UNIT (FCU)
. 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
FCU
Minimum Idle
. 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
<pic FCU1.jpg>
Fuel is used for?
<color red>
. Starting
. Acceleration
. Deceleration
. Steady State</color>
Automatic compensation is provided for Altitude, Temperature and Aircraft speed
Fuel Cut-Off Valve
. Fuel cut-off valve is controlled by fuel levers.
. It receives fuel from FCU and allows fuel to flow to Combustion Camber
Fuel Nozzles
<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
<pic Fuel sys.jpg>
Reduction Gear Box
. 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
Engine Instalations
<pic Engine Instalation1.jpg>
<pic Engine Instalation2.jpg>
Prop Blade Angle
<pic blade angles1.jpg>
<pic blade angles.jpg>
Prop Blade Angle
FX
87°
Mechanical stop in prop dome
Can be adjusted
Prop Blade Angle
Constant Range Speed
75° to 96°
Prop speed is controlled by CSU
Prop
Contact Angle
21°
Point at witch low pitch nut contacts and move feedback ring
Prop
Prime Blade Angle
17°
Feedback ring moves beta valve.
Oil flow to CSU is restricted
(Unlimited Hydraulic Low Pitch Stop)
Prop
Idle Blade Angle
11°
Blade angle when beta valve when power levers at Idle
Prop Blade Angle
Beta Backup activation
Beta Backup Solenoid activated
(Microswitch)
Prop Blade Angle
Beta Range - Idle Power
(Idle Null)
11° to minus 2°
Blade angle changes with no change in Ng (51%)
Prop Blade Angle
Reverse
0° to minus 15°
Beta valve
Prop Blade Angle
Max Reverse
minus 15°
Mechanical stop in prop dome
Can not be adjusted
Fuel to FCU is limited by Nf Gov due to reset arm (91%±1)
Propeller Oil Supply
. CSU oil pump increase oil pressure from 85 psi to <color red>385 psi</color> to overcome forces of propeller counterweights
Oil path in Prop System
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)
<pic on Speed.jpg>
CSU
Constant Speed Unit
. Three ranges:
Under speed
Overspeed
On Speed

Between 75% and 96% Np.
<pic GOV.jpg>
Slight Overspeed
Overspeed
Slight Overspeed
<pic slight overspeed.jpg>
Overspeed
<pic over speed.jpg>
On Speed
Reverse
On Speed
<pic on Speed.jpg>
Reverse
<pic reverse.jpg>
Constant Speed Range
(Np Gov or Prop Gov)
. 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.
Beta Range
. 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
Idle Null
. 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
BETA BACKUP SYSTEM
. 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>
<pic Beta sys CB.jpg>
Beta Valves Differences
<pic beta vavles differences.JPG>
Beta Disarm Light
.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.
<pic beta disarm AutoFX beta light.jpg>
Overspeed Governor
. 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%
Perform it's function by dumping oil in the sump, allowing the counterweights and feathering spring to coarsen the blade angle.
Fuel Topping Governor
(Nf Gov)
. 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)
AutoFX
. 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>
AutoFX Test
<pic autofx2.jpg>
Conditions for AutoFX
to Arm
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>
AutoFX Armed
<pic autofx1.jpg>
Conditions to AutoFX
a Prop
2 conditions to Autofeather
<color red>
1. System must be ARMED
2. Torque must fall below 11 psi (2 sec)</color>
AutoFX Engine Failure
<pic autofx3.jpg>
Micro-Switches
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)
Micro-Switched in Twist Grip
Disable Beta backup system micro-switch @ the prop to allow prop to go into reverse
Fuel Levers
.2 positions ON or OFF.
.Preloaded to require deliberate action.
.Mechanically connected to Cutoff valve.
Generators:
<color red>2 Microswitches
Low RPM, High Torque to High RPM, Low Torque</color>
Prop Levers
.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
Reset Props:<color red>
1 Microswitch in Left Prop Lever
(less than 71%)</color>
Power Levers
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
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>
Engine Controls
<pic commands.jpg>
<pic levers.jpg>
PWR LEV
TEST
Push-to-test green switchlight,
twist twist-grip, green light should come on.
<color red>Testing integrity beta disarm microswitch. </color>
<pic Tests.jpg>
Fire Detecting Test
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.
<pic T Handles.jpg>
Prop Gov Test
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>
<pic overspeed gov.jpg>
Beta Range Test
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°
<pic Tests.jpg>
Auto FX Test
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
Test mode maintains power lever Microswitches closed
regardless of power lever position
Hydraulic Fluid
<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.
Hydraulic System
. 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.
<pic Hydraulic sys.jpg>
Hydraulic System
Damping accumulators
<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>
Hydraulic System
Working Pressure
<color red>. 1225 PSI to 1625 PSI.
. Pressure relief valve opens at 1750 PSI.</color>
Fire Protection System
. 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.
<pic fire bottle.jpg>
Fire Detection Probes
. 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>
<pic Fire Detection.jpg>
Fire Detection TEST
. 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.
<pic T Handles.jpg>
Fire Detection
Electrical Design
<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>
<pic Fire electric sys.jpg>
Fire Detection C/B
. 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.
<pic fire cb1.jpg>
Fire Bottle
Indicating Disk
<color red>RED</color> = Thermal Relief Valve
<color yellow>YELLOW</color> = Fire Handle has being pulled
RED disk can be MELed
Check bottle charge befor 1st flight of the day
Bleed Air
. 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
<pic bleed air1.jpg>
Bleed Air Uses
. Auto Pilot (Old System and very rare)
. Cabin Heat
. Airframe Deicing
. Intake Deflectors
<pic bleed air2.jpg>
Intake Deflectors
. 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
Intake Deflectors Operation
. 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
Seaplane Differences
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.