Engine Instruments Flashcards
What is the purpose of engine instruments?
Necessary for the flight crew to properly adjust and monitor engine system operations and for troubleshooting
Engine instruments must be mounted in a way that is resistive to what type of vibrations?
High
Amplitude
Low
Frequency
What are transient markings?
A diamond, dot, triangle, or a second red radial line, that indicate the absolute max limit
What does a slippage mark look like?
A white radial line starting on the instrument case and extending to the face of the glass
When is a slippage mark used?
Must be present when range markings are on the glass
What do slippage marks do?
Show if the glass has loosened or moved
What do bourdon tubes measure?
High pressure or Temperature
What are 3 examples of high pressure systems?
Hydraulic
Oil
Oxygen
Pressure is directly affected by what?
Temperature
What are diaphragms used to measure?
Low pressure
Has high sensitivity
What do bellows measure?
Low pressure
Has a greater range of movement
What FAR talks about tachometers being a primary engine instrument?
FAR 91.205(b)(4)
What do tachometers measure on reciprocating engines?
Crankshaft RPM
What do tachometers measure on helicopters and turbines?
Rotor or propeller RPM
For turbine engines, the tachometer will indicate in:
Percent of RPM
What is the most common type of mechanical tachometer?
Magnetic Drag Cup
What is the electric tachometer called that is engine driven and produces a three phase AC current at differing frequencies with different speeds?
Tach Generator
(Higher engine RPM = Higher frequency)
The tach generator produces a three phase variable frequency signal that drives what?
A synchronous motor inside the instrument
What type of electric motor is commonly used in electric tachometers?
Synchronous motor
The indicator of a tachometer system is responsive to changes in?
Frequency
Why do helicopters require a minimum of two synchronous tachometer systems?
One indicates engine RPM and the other for the main rotor RPM
What unit in an electric type tachometer system sends information to the indicator?
The three phase AC tach generator
An electric tachometer uses a synchronous motor which is governed by the tach generator’s:
Frequency
In what units are turbine engine tachometers calibrated?
Percent of engine RPM
Where is the oil temperature probe placed?
In the oil line where the oil enters the engine (after cooling)
((So that it can give an indication of the efficiency of the oil-cooling system))
What circuits are used for electrical oil temperature gauges?
Wheatstone Bridge
Or
Ratiometer Circuit
A thermocouple temperature indicating system is self-contained and requires ___ ______ _____.
No external power
The basic measuring device in the instrument used for measuring temperature with thermocouples is what?
A Galvanometer
What are thermocouples used on reciprocating engines made of?
Iron and Constantan
Or
Copper and Constantan
What is used to indicate the fuel-air ratio being burned inside the cylinders on a recip engine?
The Exhaust-Gas Analyzer
How are the EGT probes on a turbine engine wired?
In parallel
What are thermocouples used on turbine engines made of?
Chromel and Alumel
Where are EGT thermocouples located on a turbine engine?
Immediately after the last turbine stage
What instrument is monitored to determine whether the start is normal or a hot start on a gas turbine engine?
Exhaust Gas Temperature
What is Engine Pressure Ratio (EPR)?
A ratio of the turbine discharge pressure to the compressor inlet pressure
What is the EPR used for?
To determine the amount of thrust being generated by a turbine engine
What is the equation used to determine EPR?
Pt (exhaust)
EPR= ——————
Pt (intake)
Where is the turbine discharge pressure sensor located?
Immediately aft of the last turbine stage
What is the Manifold Pressure Indicator (MAP) calibrated in?
Inches of Mercury
What does the MAP measure?
The pressure in the intake manifold of a reciprocating engine
(Direct measure of engine power output)
If a complete break in the line between the manifold pressure gauge and the induction system should occur:
The manifold pressure gauge will indicate the prevailing atmospheric pressure at all engine speeds
What does FAR 91.205 state?
Manifold Pressure Indicator (MAP) is required on (boosted) turbo and supercharged engines
What are the two types of thermocouples used for Cylinder Head Temperature indicators?
Seal or Gasket
And
Bayonet type
Where are the hot and cold junctions for CHT located?
Hot = at the cylinder head
Cold = at the indicator
Can thermocouples be altered?
NO
NEVER
NADA
What are the 3 basic types of fuel quantity indicators?
Mechanical
Resistance (electric)
Capacitance (electronic)
Large aircraft consume fuel based on what?
Fuel weight not volume
Capacitance quantity indicators measure what?
Measures the weight of fuel in the tanks rather than the volume
Pressure is a direct indication of power output, because…..
Engine power is proportional to fuel consumption and fuel flow is directly proportional to pressure
Fuel pressure gauge can be calibrated in ___ __ _____.
Percent of power
The fuel flow meter used with continuous flow fuel injection systems is a pressure gauge that measures what?
The pressure drop across the injector nozzles
On a twin engine aircraft with fuel injected recips, one fuel flow reads higher than the other in all engine operating configurations. What is the cause?
One or more fuel nozzles are clogged
The fuel flow indication system used with many fuel injected opposed engine airplanes utilizes a measure of:
Fuel pressure
In an aircraft equipped with a pressure drop type fuel flow indicating system, if one of the injector nozzles becomes restricted, this would cause a decrease in fuel flow, with:
An increased fuel flow indication on the gauge
What is the most accurate means to determine fuel consumption of a recip engine?
Fuel Flowmeters
(Shows amount of fuel in gallons or pounds consumed per hour)
What are the 3 synchro units?
Autosyn
Magnasyn
Selsyn
What is the biggest difference between the autosyn unit and selsyn unit?
Autosyn uses AC
Selsyn uses DC
How is motor driven impeller and turbine fuel flow transmitters designed to transmit data?
Using aircraft electrical system power
The fuel flow indicator rotor and needle for a motor impeller and turbine indicating system is driven by?
An electrical signal
The fuel flow indication data sent from motor driven impeller and turbine and motorless type fuel flow transmitters is a measure of?
Mass fuel flow
