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What are 3 types of instruments?
What are the 4 colors that are used on engine gauges?
- blue arc
- yellow arc
What does the Green identify in engine gauge markings?
Define what the Blue Arc
on a engine instrument gauge
- Blue arc-range of operations under unique circumstances
- Yellow Arc- Precautionary range of time limited operations
- Red- Min or Max allowed (transient limites)
What is the purpose of the white mark on the glass and case for?
What is it called?
Witness mark-so you know if the glass has shifted
What are some of the common gauges used on recip engines?
- Carb air temp
- fuel pressure
- fuel flow indicator
- mainfold pressure
- oil temp/pressure
- TachSuction gauge for vaccume pressure
Name some common Turbine gauges?
- EGT-ITT, TIT, TOT
- RPM %
- oil, fuel pressure
What does PSIG, PSIA and PSID stand for?
- G-reads in atsmospheric
- A-absolute pressure, gauge pressure + absolute pressure
- D-difference between 2 pressures
What is a Burdon tube used for?
oil pressure gauge-when the tube is under pressure it wants to straighten out
Define a Diaphragm type of gauge?
used for fuel pressure, MAP and torque-movement of the diaphram converts in and out motion to mechanical movement
How do Bellows gauges work?
Spring loaded against pressure
What type of application would you used a differential pressure gauge?
used on filters
What type of gauge works on a diaphram and pressure?
What is a D'Arsonval type meter?
Gauge-perminate magnet with spring and neddle attached
What type of gauge is used in AC circuits
Name 5 different methods of measuring temp ?
- Wheatstone bride
- Vapour Pressure
- bi-sexuals (metallaic)
What is the basic concept behind measuring voltage with a Wheatstone bridge?
What's the disadvantage?
- Potential difference between A&B
- AC normally doesn't have consistent voltage
How does a Ratiometer operate?
As variable resistor moves, changes voltage, there is a voltage difference between
How does Vapor Pressure cause the Bourden tube to expand?
liquid or gas expands bourden tube because of heat
Explain the therory behind bi-metallic strips?
under temp change brass and steel expand at different rates
How does current flow in a thermal couple?
current flows at the temp rises
What is the theory behind thermocouples?
Voltage generated in a thermocouple system is proportional to the temp difference between the 2 ends
In a thermocouple, what does the green and white colors means?
- green-Alumel (magnetic)
- white-Chromel (non-magnetic)
Why do some engines have thermocouples in parallel?
- heat is different at diferent spots in engine, take an average
- prevents them from all buring out if one burns out
How in the FUCK do you check a Thermocouple?
- Heat response test (with a Barfield tester)
- you check for a rise when heat is applied
- also check resistence and insulation test
What is the effect of shortening a thermocouple harness?
Cannot be shortened or repaired, system operates on very specific total resistence (2 or 8 ohms)
What is the effect if you have a bad connection on your thermocouple harness?
gauge will read low
What would you use a EGT compensation Box for?
Trim temp so it reads accuratly
Name the 5 types of tach's that are used?
- Magnetic drag cup
- Tach generator
- electric tach
- magnetic pickup
In a mechanical tach, what two forces are causing the steel cable to move?
flyweights and spring
How does a magnetic drag cup work?
- Cup spring loaded to zero, magnet spins, pulls cup to give RPM indication
- Cup rotation is proportional and calibrated to engine speed
What type of electricty does a tach generator produce?
What type of a/c is it used on?
- large a/c
- similar to Mag drag cup, cable is replaced with AC electrical
How does a electric tach pick up the engine RPM?
Extra set of points in the magneto, pilse taken off P-lead, counts how many times the mag turns
What is the purpose of a dual tach?
shows left and right engines or rotor and engine speed
What does a triple tach read and how is it driven?
reads as a percent, driven by the N2, both engines and rotor RPM have needles
What is a turbine tach reading?
fan speed, engine speed or N1 N2
What are the 4 ways to measure torque?
which two are the most common?
- Foot Pounds
- PSI, % (most common)
How is the resistence varyied in a Pressure Transducer for DC?
what supplies the pressure to move the potentiometer?
- Uses Potentiometer to vary resistence
- bourden tube, bellows diaphram
In a linear var differential transformer, how is the probe moved?
uses inductance-probe moved by bourden tube
Why is a dead weight test done?
check/confirm accuracy of torque
What are two ways you can adjust a compensating transducer?
What is it compensating for?
- index dial
- comps for system inaccuracy (adj small amounts)
Why is calibration needed?
Takes out inaccuracies in system cause not all engines are the same
What type of gauge would be used on gears to measure torque?
Stress gauge-goes under compression and tension, measures the change in resistence on a bridge circuit
How does does a shaft using mag pickups measure torque?
shaft within a shaft- measures the twist of the shaft to get torque
Ina EPR gauge, how is the signal sent to the cockpit?
Differential Pressure Bellows to Auto-sin, moves the needle in the cockpit
What is the name of the 3 remote position systems? and what type of electricty do they work with?
Where does the Magnesyn recieve power from?
permanant magnet and Bus or inverter supply power
What is the function and location of chip detectors ?
- located in scavenge lines
- can determine excessive engine wear
How do chip detectors detect chips in the system
debris will bridge chip detector and close circuit
How do Pulsed Chip detectors work?
discharges capactors to burn off small flakes or chips, if its to big a light will be turned on in the cockpit
How does a piezoelectric sensor generate electricty?
How is it to be mounted?
- when compressed it generates a electric current
- mount at the centre of rotation
What causes a indication on a differential pressure switch?
When the pressure difference between P1 and P2 gets to low, sends signal to indicate that the filter has been bypassed
What is the name of the electrical meter system used to check and calibrate and check the integerity of the ITT systenm?
What is used to allow the removal of a chip detector without oil spilling out?
How can a differential pressure switch be used to indicate fuel filter is bypassed?
Difference in pressure, closes switch, turns light on in c/p
How is fuel flow measured in a piston engine?
- piston-measures fuel as pressure
- turbine-fuel flow measured by mass-swirl vanes
Why would you preform a power check? what is the power check based on?
- to determine if the engine can operate to spec
- based on manufactures specs
What does EICAS stand for?
what are the 4 levels?
- Engine indicator and crew alert system
- Level A-Warning-Red
- Level B-Caution-Amber
- Level C-Advisories-Amber of light blue
- Level D-Memos-White
What does ECAM stand for?
Electronic Centralized Aircraft Monitor
If you have a thremocouple harness with 8 probes and one burns out, what would the temp reading in the cockpit read?
It would read slightly less after the probe burned out to an increase in resistence
What type of fuel flow meter gives the highest accuracy ?
What are 3 systems that are used on a turboshaft to measure torque?
- helical gear
- strain gear
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