What device that is sensitive to changes in ambient air pressure is used for sensing pressure inputs such as Pt2, or Pb?
Partially evacuated bellows
What valve prevents fuel flow until proper pressure is attained?
P&D Valve
Where would the P&D valve be located?
6 o'clock position
What valve fills and pressurized the fuel system downstream of the metering valve to assure proper starts?
Primer Valve
How would the FCU likely respond to a decrease in compressor Inlet pressure (Pt2)?
Metered fuel flow decreases (Pt2)
How would the FCU likely respond to an increase in compressor Inlet temperature (Tt2)?
Metered fuel flow decreases (Tt2)
What type of fuel management system would likely be found in a modern transport aircraft?
FADEC
What function does the governor flyweight system perform?
Provides RPM control
The shroud around the end of the fuel nozzle helps to retard accumulation of carbon deposits. What other function does it perform?
Aids atomization of fuel
Keeps tip cool
Prevents carbon deposits
What substance would the CIT probe could be filled with?
Alcohol
What 2 main adjustments (called trimming) are performed by the A&P on a hydromechanical Fuel Control? What other adjustments may be necessary?
Idle, max power
Fuel specific gravity settings
What 2 functions are performed by a "P&D" valves?
Pressurize & Drain (dump)
What are two basic types of fuel nozzles?
Simplex & Duplex
What is used as a hydraulic medium on VSVs & VBV actuators?
Servo fuel
What does FADEC stand for?
Full Authority Digital Engine Control
At what ranges is the primary fuel circuit the only circuit supplying fuel on duplex fuel nozzles?
Starting & Acceleration
What is the backup to a Supervisory EEC?
Hydromechanical FCU
What pressures position the bypass valve on an FCU?
Differential pressure between metered & unmetered
On a FADEC system, what would happen if a failure occurred on the primary computer?
Revert to secondary
What are the most common types of fuel controls?
Hydromechanical & electrical
For what reasons are we concerned with the idle RPM setting?
Ensure proper bleed air output at idle
Correct acceleration
Correct electrical generator output
What FCU adjustment would be considered most critical?
Max power
What is the output of the boost pumps?
High volume, Low pressure
Why do we need fuel heaters?
Prevent ice from clogging filters
How can you tell if a fuel filter has been bypassed? (2)
Visual pop out, cockpit indication
What is used while trimming Pratt & Whitney engines to facilitate adjustments at a lower than maximum power setting, thereby saving fuel and keeping engine temps at a safer range?
Part Power Stop
How will the FCU likely compensate for an increase in Pb?
Metered fuel flow will increase
Where would the flow divider be located on a system that uses duplex nozzles with a single fuel line?
In the nozzle
Where would the flow divider be on a system that uses two fuel lines per duplex nozzle?
In the P&D Valve
What is done with fuel drained from the manifold upon shutdown?
Returned to inlet side of the pump
Draining the manifold on shutdown keeps deposits from forming in the fuel lines. What other reason would we want to drain the fuel manifold?
Prevent post-shutdown fires
Can a fuel control be adjusted to operate properly on various types of fuels?
Yes (fuel specific gravity setting)
How does a FADEC work?
Receives and develops commands to various actuators to control engine parameters
What valve in the fuel control or fuel pump would establish maximum pressure?
Pressure Relief Valve
What unit of measure is used when referring to fuel or airflow through the engine?
Pounds
What are some advantages of FADEC over hydromechanical FCUs?
Better control of hot section temperatures
No trimming
Improved starting
Fuel efficient
Better engine limit protection
Fully modulates the ACC
more repeatable engine transients
Compensated for atmospheric changes & bleed air requirements
(ASA) What factor is not used in the operation of an aircraft gas turbine engine fuel control unit?
(ASA) mixture control position
(ASA) in order to stabilize cams, springs, and linkages within the fuel control, manufacturers generally recommend that all the final turbine engine trim adjustments be made in what direction?
(ASA) increase direction
(ASA) when trimming a turbine engine, the fuel control is adjusted to what?
(ASA) Set idle RPM & maximum speed or EPR
(ASA) a supervisory electronic engine control (EEC) is a system that receives engine operating information and ...?
(ASA) Adjusts a standard hydromechanical fuel control unit to obtain the most effective engine operation
(ASA) a full authority electronic engine control (EEC) is a system that receives all the necessary data for engine operation and...?
(ASA)develops commands to various actuators to control engine parameters
(ASA)in a supervisory EEC system, any fault in the EEC that adversely affects engine operation..?
(ASA) Causes an immediate reversion to control by the hydromechanical fuel control unit
(ASA) The active clearance control (ACC) portion of an EEC system aids turbine engine efficiency by..?
(ASA) ensuring turbine blade to engine case clearances are kept to a minimum by controlling case temperatures
(ASA) What should be checked/changes to ensure the validity of a turbine engine performance check if an alternate fuel is to be used?
(ASA) Fuel Specific Gravity setting
(ASA)the generally acceptable way to obtain accurate on-site temperature prior to performing engine trimming is to..?
(ASA) hang a thermometer in the shade of the nose wheel-well until the temperature reading stabalizes
(ASA) An aircraft should be facing into the wind when trimming an engine. However if the velocity of the wind blowing into the intake is excessive, it will likely cause what?
(ASA) false high compression and turbine discharge pressure, and a subsequent low trim
(ASA) generally, the practice when trimming an engine is to what?
(ASA) Turn all accessory bleed air off
(ASA) For what primary purpose is a turbine engine fuel control trimmed?
(ASA) To obtain maximum thrust output when desired
(ASA) Which type of fuel control is used on most of today's turbine engines?
(ASA) hydromechanical or electronic
(ASA) Under what condition will trimming of a turbine engine be most accurate?
(ASA) no wind & Low Moisture
(ASA) A mixture ratio of 11:1 normally refers to
(ASA) 1 part fuel to 11 parts air.
(ASA) in turbine engines that utilize a pressurization and dump valve, the dump portion of the valve does what?
(ASA) Drains the engine manifold lines to prevent fuel boiling and subsequent deposits in the lines as a result of residual engine heat ( at engine shutdown)
(ASA) what effect does a high atmospheric humidity have on the operation of a jet engine?
(ASA) little to no effect
(ASA)what are the positions of the P&D Valve in a jet engine fuel system when the engine is shut down?
(ASA)
Pressurization valve closed
Dump valve open
(ASA)what is not an input parameter for a turbine engine fuel control unit?
(ASA) ambient humidity
(ASA) during what period does the fuel pump bypass open and remain open?
(ASA) when boost pump pressure is greater than fuel pump pressure
(ASA) boost pumps in a fuel system do what?
(ASA) provide a positive flow of fuel to the engine pump
(ASA)what is the purpose of an engine driven fuel pump bypass valve?
(ASA) to prevent a damaged or inoperative pump from blocking the fuel flow of another pump in series with it
(ASA) the fuel pump relief valve directs excess fuel to what?
(ASA) Inlet side of the pump
(ASA) The fuel systems of aircraft certified in the standard classification must include what?
(ASA) a positive means of shutting off the fuel to all engines.
(ASA) where should the main fuel strainer be located in the aircraft fuel system?
(ASA) At the lowest point in the fuel system
(ASA) What is a characteristic of a centrifugal type fuel boost pump?
(ASA) it separates air and vapor from the fuel
(ASA) Fuel Pressure produced by the engine driven fuel pump is adjusted by what?
(ASA)relief valve adjusting screw
(ASA)what are the principle advantages of the duplex fuel nozzle used in many turbine engines?
(ASA) Provides better atomization and uniform fuel pattern
(ASA) Why is it necessary to control acceleration and deceleration rates in turbine engines?
(ASA) Prevent blowout or die out
(ASA) which turbine fuel filters has the greatest filtering action of any present day filter type?
(ASA) Micron filter
(ASA)what is the purpose of the flow divider in a turbine engine duplex fuel nozzle?
(ASA) Creates the primary and secondary fuel supplies
(ASA) what causes the fuel divider valve to open in a turbine duplex fuel nozzle?
(ASA) Fuel Pressure
Classiefied as a non-positive displacement pump (high volume, low pressure), the boost pump does not require what?
Bypass or pressure release
Why is a pressure relief valve necessary?
Pumps are constantly supplying more fuel than the engine can use.
What are the FCU inputs?
Compressor RPM
CIP
CIT
Burner can or diffuser pressure
TDT
throttle position
Free turbine RPM