Instruments 2 Flashcards
To what component in a hydraulic pressure indicating system would a pressure transmitter be connected?
The accumulator
Where in a hydraulic pressure indicating system would a pressure switch be located?
Downstream of the hydraulic pump
What is the purpose of a hydraulic pressure indicating system?
- To ensure each system is working properly
- To warn of any problems
What is the purpose of a hydraulic system low pressure warning light?
To give an indication if unsafe hydraulic pressure
What pressure detection/sensing devices may be used in a hydraulic pressure indicating system?
- Bourdon tubes
- Diaphragms
What component, within a hydraulic pressure transmitter, connects the detection device to the synchro transmitter rotor?
A sector gear
List aircraft systems that may utilised hydraulic power for their operation?
- Landing gear
- Brakes
- Flught controls
- Ground steering
- Flaps
- Doors
- Canopies
What are the key components of a hydraulic system?
- Reservoir
- Accumulator
- Hydraulic pump
- Pressure relief valve
- Low pressure sensor
- Hydraulic system temperature sensor / bulb
- Hydraulic system pressure sensor / transmitter
What unit of measure is normally displayed on the dial of a hydraulic pressure indicator?
Pounds per square inch (PSI)
What type of pressure detector / sensor is typically employed in a low pressure warning system?
A diaphragm
What colour is used for a low pressure warning light?
Amber
What components make up a hydraulic temperature indication system?
- Temperature sensor
- Indicator
- Interconnecting wiring
In reference to a hydraulic system temperature indicating system - where is the temperature sensor normally fitted?
Just prior to the oil returning to the reservoir
Why is it important to monitor the temperature of hydraulic oil?
Above certain temperatures, the viscosity of the hydraulic oil changes - this then downgrades the performance of it
Type of temperature sensor used in a hydraulic oil temperature indicating system?
A bulb sensor
What type of quantity indication do the below use:
- Hydraulic oil reservoir
- Engine oil
Sight gauge
DC synchro system
The wiper arm in an engine oil quantity transmitter is connected to what component in the oil tank?
A float and actuator
3 types of fuel flow indicating systems?
- Rotating vane
- Impeller
- Fuel mass flow
What output is provided by a fuel flow transmitter?
Electrical output signal proportional to the flow rate
What type of fuel flow indicating system is used to counter the problem of fuel density varition?
A mass fuel flow indicating system
In a rotating vane type fuel flow transmitter, what opposes the movement of the metering vane?
A calibrated spring
In a rotating vane type fuel flow transmitter, what component (driven by the metering vane) provides a DC voltage proportional to the fuel flow?
A wiper across the potentiometer
In a rotating vane type fuel flow transmitter - what provides a path for the fuel low in case the vane becomes jammed closed?
Bypass valve
In an impeller type fuel flow system - what component converts the transmitters pulsing signal into one that is used to drive the indicator pointer?
The amplifier / signal conditioner
What ‘relationship’ is used by a mass flow fuel indicating system?
Fuel mass and viscosity
What components make up an integrated fuel flowmeter system transmitter?
- Housing
- Motor driven impeller assembly
- Flow metering chamber
- Externally mounted magnetic pick-off assembly
How are the outer drum and impeller assembly in an integrated fuel flowmeter transmitter coupled to each other?
By calibrated spring
What are the 2 components in the integrated fuel flowmeter transmitter, are the magnets fitted to?
- Outer drum
- Impeller
Under which condition are the integrated fuel flowmeter transmitter magnets in alignment?
Under zero fuel flow conditions
3 functions performed by the integrated fuel flowmeter system computer?
- Proved power for various cct of the system
- Detects the number of pulses produced by the transmitter
- Computes and integrates the fuel flow rate and fuel consumed for the display indicator
What 2 pieces of information are displayed on an integrated fuel flowmeter indicator?
- Fuel flow
- Fuel used / remaining
What does the computer in a fuel remaining / fuel used indicating system calculate?
Fuel consumed over a period of time from the flow rate during the period
What is provided on a fuel remaining / fuel used indicator to reset the counters to zero?
Mechanical reset button
What component within an integrated fuel flowmeter indicator provides feedback to the computer if the pointer position does not represent the fuel flow from the transmitter?
Timebase section
What type of transmitter is used in a volumetric fuel quantity indicating system?
Float arm type transmitter
What type of transmitter is used in a mass type fuel quantity indicating system?
Capacitance fuel probes
What 3 types of meter movements may be used in a volumetric fuel quantity indicating system?
- Milliammeter
- Ratiometer
- Desynn and autosynn
What type of cct is used to indicate fuel contents in a capacitance fuel quantity indicating system?
A balanced bridge cct
What elec supply is required to power a mass type fuel quantity indicating system?
AC power
What does a mass type fuel quantity indicating system take into account to indicate the weight of the fuel?
Fuel density (due to temp and pressure changes)
Purpose of the fuel quantity indicating system?
Indicate the amount of fuel remaining int he fuel tank
What is fuel quantity information used to determine?
Remaining aircraft flight time
In what type of fuel tank does a float arm system work best?
Fuel tanks that are regular in shape
In a volumetric fuel quantity indicating system - what happens as the float are rises or falls?
The arm rotates the wiper across the resistance winding, proportionally changing the resistance to correspond to the quantity of fuel remaining in the fuel tank
2 advantages of the volumetric fuel quantity indication system?
- Inexpensive to manufacture
- Simple to maintain
3 disadvantages of a volumetric fuel quantity indication system?
- Foaming of fuel at high altitude cases the float are to ride too high
- Mechanical damages can occur
- Errors are introduced when the volume of the fuel changes doe to temperature variation
4 advantages of a mass fuel indication system?
- Ability to totalise all of the tanks
- No moving parts (except the indicator itself)
- High degree of reliability
- Internal self-test feature
In a mass type indicating system - the capacitance of what 2 substances is measured?
- Air
- Fuel
What is the approx dielectric constant of fuel?
2
In a mass type indicating system - how is fuel quantity indication accuracy ensured when the fuel tank is tilted?
2 or more probes are used
What type of cct is a capacitance fuel quantity indicating system?
Balanced bridge cct
What type of elec power supply is required to operate a capacitance fuel quantity indicating system?
AC power
What is the relationship between mass, volume and density of fuel regardless of temperature?
M = V x D
What is installed at the bottom of the fuel tank and always immersed in fuel, to measure the density of the fuel?
Compensation probe
What affects the dielectric constant of fuel?
Change in temp will cause a change in the fuel density
Aircraft applications for bleed air?
(PNEUMATIC PRESSURE INDICATING SYSTEMS)
- Cabin pressurisation and air con
- Anti-icing systems
- Hydraulic reservoir pressurisation
- Galley functions
- Engine starting
What aircraft pneumatic (bleed air) system parameters require monitoring?
- Pressure
- Temp
- Flow
Purpose of cabin pressurisation system?
- Maintain constant low altitude in the cabin area during flight
In cabin pressurisation systems:
1) what component is used to select the desired cabin pressure and rate of pressure change within the cabin?
2) What component opens and closes to maintain the desired cabin pressure?
1) Pressure controller
2) Outflow valve
Define the term thrust?
Force produced by the engines - to propel the aircraft through the air
What type of pressure measurement is used in a thrust indicator?
Differential pressure
What reference pressure is used by a thrust indicator for a propeller driven aircraft?
Pilot pressure
If a propeller is generating thrust, which probe will feel the highest pressure?
Thrust probe
What reference pressure is used by a thrust indicator for a jet engine?
Static pressure
If a jet engine is generating trust, which port will feel the lowest pressure?
Static port
2 types of torquemeteres?
- Hydraulic
- Torque shaft
Where are hydraulic cylinders in a hydraulic torque indicating system?
Secured to gearbox casing
2 types of engines that use torque indicating systems to indicate engine power?
- Turbo prop
- Turbo shaft
What type of force is being measure for torque indication?
Twisting force applied to the shaft
What may occur if the engines rated torque is exceeded?
It may exceed the designed limit of the airframe and unnecessarily strain the power plant / engine
In a hydraulic torque indication system - the aerodynamic resistance produced by the propeller, transfers a portion of torque to which component?
The stationary ring gear
What is the relationship between the oil pressure in a hydraulic torque indication system and the torque applied?
Oil pressure is proportional to the torque applied
What is used in a hydraulic torque indication system to sense oil pressure?
Bourdon tube
In a torque shaft indication system - what is measures to give an indication of torque?
The amount of deflection between a torque shaft and a reference shaft
How is the reference shaft mounted in a torque shaft indication system?
So that it forms a sleeve around the torque shaft
What is located on the end of both the torque and reference shafts?
Exciter wheels
What is generated as the exciter wheels pass by their respective magnetic pick-up assmblies?
Elec pulses
How does the phase detector generate an output that represents the torque being measured?
By calculating the difference between the 2 magnetic pick up assembly signals
What component makes up an engine pressure ratio (EPR) indication system?
- Inlet pressure sensor
- Number of exhaust pressure sensors
- Pressure ratio transmitter
- An indicator
What type of jet engines use engine ratio indication systems? (EPR)
Axial flow turbojet engines
How does an EPR indication system express the thrust produced?
The ratio of the air pressure at the engine outlet to the air pressure at the engine inlet
What does the resultant of the forces produced by an EPR transmitter set of bellows, move?
What does this movement represent?
The core of an LVDT
The ratio of 2 pressures
- Engine inlet
- Engine outlet
What must be done to the LVDT output singal prior to being transmitted to the indicator?
- Amplify
- The LVDTs signals are small so it must be amplified
How does the pick-up unit of an engine vibration indication system mounted on an engine?
At right angles to the engines spin axis
Components of an engine vibration indicator?
- Test switch
- Warning light
- Rectifier
- Vibration warning light
- Amplifier / filter
- Moving coil micro-ammeter
What is the purpose of an engine vibration indication system?
To monitor engine vibration
Why are engine vibration levels monitored?
A change in vibration may indicate an impending or partial fail
What does the pick up unit in an engine vibration indication system consist of?
- A spring supported permanent magnet
- A sensing coil
What does the magnet in the pick up unit tend to do when the engine vibrated?
Inertia - the magnet tends to remain fixed in space
What is induced by the movement of the sensing coil through the magnetic field from the magnet in the pick up unit?
A voltage proportional to the amount of vibration
Impeller type system - Typical faults and rectification?
Faults:
- US amplifier / signal conditioner
- Transmitter fitted in reverse
Rectification:
- Replacement of faulty item (commonly the transmitter)
Rotating vane system - Typical faults and rectification?
Faults:
- Indicator reading becomes static (if vane in jammed)
Rectification:
- Replacement of the faulty item
Volumetric system - Typical faults and rectification?
Faults:
- Moving parts are susceptible to wear
- Open cct
- Mechanical problems
Rectification:
- Replace transmitter assembly
- Calibration required following replacement
Thrust gauge - Typical faults and rectification?
Faults:
- Leaks in the plumbing
- Indicator failing
Rectification:
- Tighten plumbing connections
- Replace a length of the plumbing if required
- Replace the indicator if US
Torque indicator - Typical faults and rectification?
Faults:
- No common faults / typically very reliable
Rectification if fault found:
- Replacement of US item
Engine pressure ratio indicator (EPR) - Typical faults and rectification?
Faults:
- Transmitter failing / wearing over time
- Leaking plumbing
Rectification:
- Replacement of entire component
- Tighten the plumbing / replace a length of plumbing
Maintenance procedures?
- Must be carried out IAW authorised data / relevant aircraft maintenance PUBs
- Failure to comply - DFDA
- Tasks to be carried our by only authorised / qualified personnel
Ensure standards are maintained and equipment is managed as prescribed by the OEM (original equipment manufacture) and handled / packaged by engineering branch personnel / bodies responsible for the equipment
