DHC-8 Chapter 4
DHC-8 Bleed Air Systems Quiz
Test your knowledge on the DHC-8's bleed air systems with this comprehensive quiz. Covering topics from engine bleed air sources to fuel management, this quiz is designed for aviation enthusiasts and professionals alike.
Key Features:
- 99 Questions in total
- Multiple-choice format
- Focus on the DHC-8's technical specifications and operations
Where do we get bleed air from on the engine?
LP (P2.5) and HP (P3)
Low pressure turbine (P2.5) and High pressure turbine (P3)
Interstage Compressor and High pressure compressor
What is the purpose of the low pressure check valve?
Prevent high pressure bleed air from entering the low pressure compressor
Ensures high enough low pressure bleed air at all times
Keeps the low pressure bleed at 90%
On the -100 series, bleed air is supplied to the air condition packs via?
Pressure regulating shut off valves
Flow regulating shut off valves
Bleed regulating shut off valves
On the -300 series, A/C bleed air overpressure condition is isolated by?
Nacelle shut off valve
PRSOV
Set down limiter
On the -300 series, A/C with battery master on, Bleed selected off. Nacelle shut off valve will be?
Energized closed
Energized open
De-energized closed
On the -200 series, what limits the low pressure bleed flow?
A check valve with built in restrictor
A stand alone restrictor in the duct
A pressure regulating valve
On the -100 series, to reduce the amount of air bleed from the engine, what happens to the Aneroide capsule?
Aneroid expands, venting muscle pressure reducing bleed
Aneroid capsule keeps the pressure at 6 PSI
Aneroid capsule regulates pressure from the pilots static port
Did you do your homework about the set down limiter?
Yes
No
Maybe
Where are the emergency fuel shutoff valves located?
Rear spar outboard of the nacelle
Rear spar R/H centerwing
R/H wall of the wheel well
What controls the opening of the flow control valve?
Refuel/Transfer servo valve opens it hydro-mechanically
Arming valve opens it pneumatically
Master refuel/defuel valve opens it mechanically
R/H main integral fuel tank supplies what?
R/H engine feed and transfer to L/H tank for balancing
R/H engine feed and L/H engine feed in emergency
R/H engine feed and transfer to Aux tank for balancing
What happens when Transfer is selected?
Aux pump in doner tank starts, Refuel/defuel/transfer valves both sides and Refuel/Transfer servo valve in receiving tank opens and transfer commences
Aux pumps turns on, Refuel/Transfer servo valves opens and dump valve is held open
Ejector pumps turns on and moves fuel to receiving tank
What do the valve lights in the cockpit fuel panel indicate?
Open or closed position of the Refuel/defuel/transfer valves
Master refuel/defuel valve position
Refuel/Transfer servo valve positions
What opens the dump valve?
Arming valve is energized and the dump valve is held open by fuel pressure
Arming valve mechanically hold the dump valve open
Refuel/Transfer servo valve opens for fuel to dump valve
When does the flow control valve open?
During transfer and refueling
During transfer, fueling and engine operation
Defueling and fueling
Fuel quantity is measured by?
6 capacitance probes in each tank connected parallel
12 resistance type probes in series
Flow meters in the refueling line
Where does the scavenge ejector pumps get motive flow from?
Engine driven pumps
Aux pumps only
Refuel/defuel master valve
Pre check does what?
Tests the back-up shut off system by the pilot valve, artificially filling the float chamber
Test the fueling shut off closing the dump valve
Pre checks the fuel truck pressure
When will pitch lock occur with the blades in positive pitch?
When oil pressure is lost in the metered section of the propeller actuator
When beta lockout is inhibited
At the point where the propeller is at it's maximum angle
What is the power supply for the Aux feathering pumps?
Left and right secondary busses
Left and right main busses
Left and right battery busses
What does the position of the condition levers determine?
Propeller rpm control through the normal speed governor from 77% to 100%
Propeller position as a function of PLA/OAT
Propeller thrust in forward motion
How is the HP pump driven?
Mechanically by the reduction gearbox
Mechanically by the accessory gearbox
Mechanically by the combining gearbox
When can prop syncrophase be selected on?
When the power lever angles are within 2 degrees of eachother
When propeller RPM are within 2.5% of eachother
Whenever in cruise
How long does the AUX pump operate?
18 seconds
Until Feather/Unfeather is reached
Continuously as long as 10 minutes passes between operation
What is the purpose of the least selector valve?
Discriminator between oil output from speed sensing gov and overspeed gov.
Least selector valve lets the strongest oil pressure from either the overspeed governor or the normal speed sensing governor pass through the valve
Limits the time needed for operation between fine and coarse in the PCU
What is the pressure from the HP pump?
780 PSI
850 PSI
1020 PSI
What can the Aux feathering pump be used for?
Feather / Unfeather
Higher / lower RPM
Higher / lower torque
Where is the low pitch signal indicator switch located?
In the PCU, operated by sleeve of the control piston
Condition lever cam, operated by min RPM selection.
Power lever cam, operated in the beta range
What is the propeller construction?
Aluminium core, polyurethane foam filling, fibreglass skin.
Magnesium core, polyurethane foam filling, fibreglass skin.
Aluminium core, polycarbonate foam filling, carbon skin.
The pressure to the least selector valve, is what in normal operation?
Full pressure from overspeed governor, metered pressure from speed sensitive governor
Higher pressure from speed sensing governor, no pressure from overspeed governor
Changing from overspeed governor and speed sensitive governor denpending on selected RPM
What is the resulting action when no signal is applied to 4 way metering valve?
The propeller pitch is hydraulically locked
The propeller is pushed to feather position
The propeller is moved to reverse
When does the ground range light come on?
Power levers below flight idle, and the low pitch indicator switch closed
When the aircraft is on ground
When Beta lights come on
Where is the NP sensor located?
On top of the reduction gearbox
On top of the accessory gearbox
On the propellor shaft
Spinner attachment bulkhead is made from?
Fibreglass reinforced plastic
Aluminum composite
Aluminum core, fibreglass skin, Polyurithane foam filled
What does the synchrophase torque motor do?
Modify the tension of the speeder spring of the #2 engine governor
Modify the RPM of the #1 or #2 propeller to match
Moves the least selector valve of the #2 engine
When is pressurization initiated?
Before takeoff by switch in Power lever
During takeoff by landing gear WOW
When the pilot select runway elevation on the cabin pressure controller
What happens if compressor overtemp occurs?
Rigtigt = nacelle shut off valve closes
Ifølge prøven = acm is set to fully cold
100 & 200 series distribution of AC air?
70% cabin, 30% cockpit
30% cabin, 70% cockpit
#1 ACM Cabin, #2 ACM 30# cockpit
300 series, Which pack supplies what?
#1 pack supplies cabin #2 supply cockpit and cabin
#1 pack 70% cabin and #2 pack 30% cabin
Rear pack 70% cabin & 30% cockpit forward pack cabin only
Normal and safety outflow valve safety limit pressure?
5.8 PSI
6.0 PSI
5.5 PSI
Ram air fan drive?
Output shaft of the ACM
Driven by the high pressure turbine
Driven by the accessory gearbox
The cabin automatic controller receives commands from?
Cockpit and F/A panel
F/A panel and each Passenger service unit
Cockpit and each PSU
At which cabin pressure altitude does the cabin press warning illuminate?
10.000 ft.
15.000 ft.
8.000 ft.
Cabin press controller is interfaced with the power lever switch why?
Pre pressurization before takeoff
Ensure enough bleed pressure before initialization
Ensure pressurization is initiated by pilots
What power is supplied to the cabin pressure controller?
28 VDC
26VAC
115VAC
What causes relay K1 or K2 in the air-condition system to be energized automatically?
Duct overtemperature
Pack overheat switch
Zone temp sensor fail
What position is the outflow valve in in ground operation?
Fully open
Fully closed
Position is dependent on altitude setting
Where is the cabin temp sensor located?
Passenger service unit rear cabin
Aft galley wall
Forward galley wall
Where does the water nozzle spray the collected water?
Heat exchanger inlet
Directly on the condenser
It is drained outboard
Where is the cockpit temp sensor located?
Above the floor on the bulkhead behind the pilot
Behind the yoke co-pilot side
Behind the co-pilot floor level
Avionics compartment fan power supply?
28VDC
26VAC
115VAC
Recirculation fan power supply?
28VDC
26VAC
115VAC
What is the lowest of the pneumatic pressures in the MFC?
Py
Px
P3
What is the reference of the C-flange?
Connection between Front inlet case and rear inlet case
Connection between rear inlet case and Accessory gearbox
Connection between Reduction gearbox and front inlet case
PWC 120 series engine shaft configuration?
3 shaft
2 shaft
2 shaft + accessory shaft
What loads does the engine mounts react to?
Front = vertical, side and thrust. Rear = vertical and side
Rear = vertical, side and thrust. Front = vertical and side
Mounts all react to vertical, side and thrust loads
What is the main purpose of the HBOV?
To bleed LP compressor air to prevent surging with sudden PL movement
To cool the P3 air before it is used in the environmental system
To Shut off low pressure bleed when high pressure bleed is needed
How is the surrounding area of the nacelle isolated from the exhaust?
Shroud forms and ejector pump, creating a cooling airflow through the gap.
Exhaust shroud is cooled with bleed air from the HBOV
Exhaust pipe is covered with insulation materials
Where does the TQ indicator receive signals from a data bus?
Torque indication from EEC, fault codes from EEC
From the torque sensor mounted over the Power turbine shaft
From the symbol generator
How is the oil from the #1 engine bearing cavity scavenged?
The scavenge is aided by P3 air
The scavenge pump provides the suction
By gravity
What is the purpose of the MFC mounted RVDT
To provide an electrical signal of the power lever angle to the EEC
To provide an electrical signal of the condition lever angle to the EEC
To provide an electrical signal of the fuel metering valve to the EEC
What does the compressor section consist of?
Two independant impellers made of titanium
A centrifugal impeller of titaniun and diffusers in the form of pipes
Two axial compressors made of titanium
Which station on the engine has the highest pressure?
P2.8
P3
P4
Fuel scheduling system on the 100 series aircraft contains?
A mechanical fuel control only
A MFC with a torque motor receiving commands from the EEC
A FADEC with two independant channels
When is the ignition terminated during startup?
On starter cut out, between 55-65% NH
When startup is completed and engine is completely self sustaining
When it is manually selected
What is the purpose of the reduction gearbox integral oil tank?
Emergency engine supply in case of oil sump rupture
Ensures a oil supply to the feathering pump when engine is not running
Aux oil reservoir for prop hub overpressure
Where does the MFC get mechanical input from?
Integral torque stepper motor
Power lever and condition lever
EEC
LP compressor diffuser pipes fun
Decrease velocity and increase pressure
Introduce airstream vortices
Turning the air in the opposite direction
How many main bearings in the engine?
7 Total, 3 ball and 4 roller
7 Total, 3 roller and 4 ball
1 ball type and 2 roller type bearing for each shaft
When does the outlet filter bypass valve open?
50 PSI
18 PSI
40 PSI
What is the purpose of the switching valve when NH reaches 40-45%?
To direct P3 air to areas normally occupied by P2.5
To switch P3 bleed on on the engine
To switch P2.5 bleed on on the engine
How is compensation for shaft stiffness changes with temperature acheived?
Torque sensor temperature probe
Programming plug on the TSCU
Reference shaft has a tension spring
When is condition lever set to start/feather during start up?
Immediately
10% NH
40% NH
How many fuel nozzles installed on the gas generator case?
9 Primary/secondary and 5 Secondary
14 in total
7 primary/secondary and 7 secondary only
How is the linear actuator of the intake bypass door stopped?
Limit switches
Mechanical stops on the structure
Mechanical stops on the shaft
What does the angledriveshaft transmit?
Drive from the HP rotor to accessory gearbox
Drive from the HP rotor to reduction gearbox
Drive from the LP rotor to accessory gearbox
What is the purpose of the 2 stage power turbine?
To extract energy from the hot gasses to drive the Reduction gearbox and propeller
To extract all remaining energy and drive the compressors
To drive the accessorygearbox in the most efficient way
What is the purpose of the differential pressure regulator in the MFC?
Maintain a constant pressure drop of 18 PSI across the metering valve, by passing excess fuel flow back to pump
Maintain a constant pressure drop of 40 PSI across the metering valve, by passing excess fuel flow back to pump
Maintain a constant pressure drop of 50 PSI across the metering valve, by passing excess fuel flow back to pump
Ignition system on the 100 series consist of?
One exciter two igniters
1igniter 2 exciters
2 exciters and 2 igniters
When does the oil begin to bypass the fuel heater?
10 deg.
32 deg.
20 deg.
How long should the ignition system be off before work on it?
One redbull
One Jiu jitsu match
6 min.
What does the exciter supply to the igniter?
High voltage
High amperage
High tension
When is power removed from the ignition?
When start is completed, by a signal from the GCU
When start is done, by a signal from the power lever layshaft potentiometer
When the EEC has completed the start sequence
Where are the igniters loceted?
5 o'clock & 7 o'clock
6 o'clock & 8 o'clock
8 o'clock & 5 o'clock
What does the precooler use as a cooling medium?
P3 trough the HPSOV
P2.5 Through the HBOV
Ram air through the fan drive
Which air is taken to cool the HP turbine vane ring and LP stator vanes
P3
P2.5
Oil cooled through channels in the stator vanes
Power lever layshaft potentiometers are used for?
Give input in proportion to PLA to the Autofeather controllers
They are used for fuel governing through the EEC
They are used for Beta Lockout system in flight
How many sensors does the NH system have?
2, 1 indication and EEC, 1 EEC
1
1 Active, 1 standby
What permits the exhaust movement and compensate for expansion?
Two trunnion bearings
Horsecollers
Elastomeric mounts
Where is the APU start contactor located?
In the nose section beside the DC contactor box
Adjacent to the APU
In the L/H nacelle contactor box
Accessory gearbox has a mounting flange for?
HP Pump
Fuel pump
AC generator
Which statement is correct regarding the APU intake installation
It incorporates a structurally installed intake duct and an APU mounted inlet duct that are connected by a seal assembly
How is the APU compartment ventilated?
By an axial blower fan installed in the vent duct between the oilcooler and the air outlet and the vent exhaust port
By an fuel cooled oil cooler
By a heat exchanger in the duct
What effect will the beta backup have on the blade angle?
Increase blade angle
Decrease blade angle
Decrease fuel supply to minimum fuel governing
When does the beta backup system operate?
PLA forward of flight idle, and the blade angle decreases until the PCU low pitch signal indicator switch is activated
When the system is armed by the switch and the blade angle decrease to the beta range in flight
When the overspeed governor limit is reached
How long must the Aux feather pump rest between duty cycles?
10 min.
6 min.
18 min.
Which statement is correct regarding syncrophase torque motor
Adjust the tension of the spring of the normal speed sensing governor on engine #2
It is operated by the slave EEC by the Master EEC
It is metering the slave motor Py pressure to control the speed
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