Question 54-1 : A millivoltmeter measuring the electromotive force between the 'hot junction' and the 'cold junction' of a thermocouple can be directly graduated in temperature values provided that the temperature of the ? [ Concept airport ]

Question 54-2 : The gauge indicating the quantity of fuel measured by a capacity gauging system can be graduated directly in weight units because the dielectric constant of fuel is ?

Twice that of air and varies directly with density.

The dielectric constant or permittivity of fuel is determined by establishing the ratio of the electrical capacitance of a tank filled with fuel as compared with the electrical capacitance of the tank when filled with air measurements of the dielectric constant of a fuel at various temperatures show that the dielectric constant is a linear function of temperature decreasing with increasing temperature and varying with the applied frequencydielectric of air at 70°f = 085dielectric of jet fuel at 70°f = 17

Question 54-3 : When compared with the volumetric fuel flowmeter the mass fuel flowmeter takes into account the fuel ?

Density.

The mass fuel flow meter allows the measurement of the mass consumption of fuel the mass fuel flowmeter takes into account the fuel density

Question 54-4 : The electronic tachometer sensor is composed of ?

A notched wheel rotating in front of an electro magnet.

Question 54-5 : The advantages of a dc generator tachometer are 1 easy transmission of the information 2 independence of the information relative to the airborne electrical power supply3 freedom from any spurious current due to the commutatorthe combination regrouping all the correct statements is ?

1 2.

Dc generator tachometer consists of a small armature which is coupled to the machine whose speed is to be measured this armature revolves in the field of a permanent magnet the electro magnetic force emf generated is proportational to the product of flux and speed since the flux of the permanent magnet is constant the voltage generated is proportational to speedthe polarity of output voltage indicates the direction of rotation this electro magnetic force emf is measured with the help of moving coil voltmeter having a uniform scale and calibrated directly in terms of speedbut dc generator tachometer has a dc commutator ring which causes spurious signals

Question 54-6 : The advantages of single phase ac generator tachometer are 1 the suppression of spurious signals due to a dc generator commutator2 the importance of line resistance on the information value3 the independence of the information in relation to the airborne electrical power supply4 the ease of ?

1 3.

The single phase ac generator tachometer doesn't have a dc commutator ring thus no spurious signalsthe measurement is independent of aircraft power supply

Question 54-7 : The disadvantages of a single phase ac generator tachometer are 1 the presence of spurious signals due to a dc generator commutator 2 the importance of line resistance on the information value 3 the influence of temperature on the tachometer information the combination regrouping all the correct ?

2.

The single phase ac generator tachometer is brushless thus no spurious signalsthe measurement is independent of aircraft power supply but one disadvantage of a single phase ac generator is the possibility of the values transmitted being affected by line resistance

Question 54-8 : Torque can be determined by measuring the ?

Question 54-9 : The engine instrument utilising an aneroid pressure diaphragm is the ?

Manifold pressure gauge.

Question 54-10 : To permit turbine exit temperatures to be measured gas turbines are equipped with thermometers which work on the following principle ?

Question 54-11 : A bourdon tube is used in ?

Pressure sensors.

Question 54-12 : If an epr is set at a constant barometric pressure with an increasing oat the thrust ?

Remains constant.

Thrust is the force generated by the enginesthrust is the acceleration of a mass of air thrust = mass x accelerationmass = density x volumetherefore a decrease in density due to an increasing oat would result in less mass being accelerated and therefore a decrease in thrust but the engine management system does trim fuel automatically to maintain selected thrust settings for changes in oat

Question 54-13 : In a compensated capacitance type quantity indicating system the contents gauge of a half full fuel tank indicates a fuel mass of 8000 kg if a temperature rise increased the volume of fuel by 5% the indicated fuel mass would ?

Remain the same.

The capacity of a capacitor depends on the nature of the dielectric in which it is immersed fuel has twice the capacitance of air so a full tank has twice the capacitive reactance as en empty oneif a temperature rise increases the fuel volume the fuel weight remains the same

Question 54-14 : On an multi engine aircraft a synchroscope is used to 1 reduce structural vibration and noise2 have symmetrical thrust and fuel consumption ?

1 is correct 2 is incorrect.

Cqb15 august 2012the purpose of a synchroscope is to reduce structural vibration and noise the synchronizing system ensures that the propeller speeds are all the same this is achieved by an electrical system that compares speed signals from engine mounted generators out of balance signals using one engine as a master signal are automatically corrected by electrically trimming the engine speeds until all signals are equal

Question 54-15 : The basic principle of a capacitance fuel gauge system is that the ?

Capacity of a capacitor depends on the nature of the dielectric in which it is immersed.

A capacitance type fuel gauge system consists of a variable capacitor located in the fuel tank an amplifier and an indicator the complete circuit forms an electrical bridge which is continuously being rebalanced as a result of the differences between the capacitances of the tank capacitor and a reference capacitor the signal produced due to the differences in the signals is amplified to operate a motor the motor then drives the pointer to indicate the capacitance change of the tank capacitor and thus change in the fuel quantity is indicatedwe have seen the basic construction of this system now let us discuss how the electrical capacitance principle is utilized for the capacitance type fuel gauge system in aircraft the capacitors which are to be installed in the fuel tanks for the fuel quantity measurement must be different in construction from those normally employed in electrical equipment the plates of the capacitors take the form of two tubes mounted concentrically with a narrow air space between them these plates extend the full depth of a fuel tankcapacitance depends on some factors which are area of the plates distance between the two plates and the dielectric constant of the material between the two plates of the capacitorsnow in this capacitance type fuel gauge system the two factors plate area and distance between plates are fixed and the dielectric here is the fuel in the tank of the aircraft the flow of a momentary current into a capacitor establishes a potential difference across its plates the dielectric ie fuel in the aircraft's fuel tanks contains no free electrons so the current cannot flow through it but it should be remembered that potential difference sets up a state of stress in the atoms comprising it

Question 54-16 : Assuming that the cas remains constant if the total pressure probe is blocked the ias ?

Remains constant during level flight increases during a climb and decreases during a descent.

With a blocked pitot the pressure in the capsule is fixed like an altimeter when the aircraft climbs and the static in the case decreases the capsule expands and the reading on the instrument increases like an altimeter to hold the ias constant in the climb ie not allow the capsule to expand the actual airspeed will have to decrease remember that with a blocked pitot the asi over reads in the climb and under reads in the descent with constant ias and blocked pitot the real ias and therefore tas will decrease until the aircraft stalls

Question 54-17 : Gas turbine engine rotational speed rpm is usually sensed using either ?

A 3 phase ac tachometer generator or an ac phonic wheel system.

Question 54-18 : The output from an engine vibration transducer is ?

Always filtered to remove unwanted frequencies.

Virations are picked up by accelerometers so you measure accelerations piezzo electric or capacity type pickups giving after conversion displacement square seconda first integration will give displacement speed displacement per second a second integration will give displacementeach integration may introduce or amplify measurement errors but the initial acceleration signal is not practical for use depending on the engine type and the bearing location the displacement speed usually noted in inch per second ips is usedthe vibration frequency is filtered for the cockpit indication to indicate only vibration in a frequency band corresponding to the spool speed n1 n2 n3 that's why engines can have vibrations which are not related to spools rotating speed not being indicated in the cockpit

Question 54-19 : The sensor s feeding the epr indicator is are ?

Pressure probes one located upstream from the compressor inlet and the other downstream from the turbine outlet.

Question 54-20 : The rpm indicator or tachometer of a piston engine can include a small red arc within the arc normally used green arc in the rpm range corresponding to this small red arc the ?

Propeller generates vibration continuous rating is forbidden.

Question 54-21 : A three phase electrical tachometer consists of ?

A three phase generator a synchronous motor and a magnetic tachometer.

Question 54-22 : Cas can be obtained from the following data ?

Eas and pressure altitude.

To get from cas via eas to tas we use pressure altitude and temperature to go back from tas via eas to cas we would again use pressure altitude and temperatureeas is cas corrected for compressibiliy and compressibility is related to pressure altitude

Question 54-23 : The properties of a single phase electrical tachometer are 1 indication depending on the line resistance2 independance from the aircraft airborne power supply3 simple designthe combination that regroups all of the correct statements is ?

Question 54-24 : Concerning a fuel gauge system a pilot is more interested by the ?

Mass of the fuel than the volume of the fuel.

Question 54-25 : A float type fuel gauge 1 gives a mass information 2 gives information independent of aircraft's manoeuvres and attitude changes 3 gives information all the more accurate as the tank is full 4 is typically a dc powered system the combination that regroups all of the correct statements is ?

4.

Question 54-26 : A magnetic tachometer consists of ?

A permanent magnet turning inside a non magnetic drag cup.

Magnetic tachometer the magnetic tachometer consists of rotary bell shaped permanent magnet 1 and core 2 between which there is a narrow gaparranged in this gap is hollow aluminum cylinder 3 held against rotation by coil spring 4 the rotating magnetic field induces currents in cylinder 3 which tend to rotate the cylinder with a force whose torque is proportional to the speed of rotation of magnet 1 a scale with uniform divisions is engraved on the outside circumference of cylinder 3 it indicates the speed rpm of magnet 1 and of the shaft whose speed is to be measured in opening 5

Question 54-27 : Given the following parameters in a capacitance fuel gauge the correct formula is a = area of platesd = distance between platese = dielectric permittivity ?

Capacitance = e x a d.

Question 54-28 : A three phase electrical tachometer utilises a generator feeding ?

A synchronous motor turning a drag cup.

The electrical generator system utilises a small three phase tachometer generator driven by the engine the output of this generator is then taken to an indicator which consists of a synchronous motor turning a drag cup assembly which moves a pointer over a scale as in the mechanical system three phase electrical tachometer

Question 54-29 : The operating principle of an inductive probe tachometer is to measure the ?

Frequency of the electric impulse created by a notched wheel rotating in a magnetic field.

Question 54-30 : The unit used to measure the capacitance of a capacitor is the ?

Farad.

The farad symbol 'f' is the si derived unit of capacitance the unit is named after the english physicist michael faradaya farad is the charge in coulombs which a capacitor will accept for the potential across it to change 1 volt a coulomb is 1 ampere secondexample a capacitor with capacitance of 47 nf will increase by 1 volt per second with a 47 na input current

Question 54-31 : Any vibration displayed on an engine vibration monitoring system for a turbojet ?

Indicates rotor imbalance.

The engine vibration monitoring on a turbojet engine indicates any vibration resulting from an imbalance on the rotation parts of the engine engine vibration may occur due to fan bladespinner icing resulting in a rotor imbalance

Question 54-32 : 6000 psi is approximately equivalent to ?

400 bar.

1 psi pound per square inch = 007 bar1 bar = 15 psi

Question 54-33 : 1 bar equals how many pascals ?

100000 pa.

1 bar = 100000 pa pascal = 1000 hpa hectopascal

Question 54-34 : What is the relation between c and k c celsius° k kelvin ?

C=k 27315.

Fahrenheit = 18 x c + 32kelvin = c + 27315

Question 54-35 : Which of these statements about temperature units are correct or incorrect 1 +20° celsius = 68° fahrenheit2 0° celsius = 27315° kelvin ?

I is correct ii is correct.

Fahrenheit = 18 x c + 32kelvin = c + 27315

Question 54-36 : Which of these statements are correct or incorrect 1 +15° celsius = 27315° kelvin2 +15° celsius = 59° fahrenheit ?

I is incorrect ii is correct.

Fahrenheit = 18 x c + 32kelvin = c + 27315

Question 54-37 : Which statement is correct regarding relation between kelvin k fahrenheit f and celcius c temperatures 1 k = c 273152 f = 18 x c + 32 ?

I is incorrect ii is correct.

Fahrenheit = 18 x c + 32kelvin = c + 27315

Question 54-38 : Which of these statements are correct or incorrect 1 +15° celsius = 28815° kelvin2 +15° celsius = 59° fahrenheit ?

I is correct ii is correct.

Fahrenheit = 18 x c + 32kelvin = c + 27315

Question 54-39 : The correct relation is ?

045 kg = 1 lb.

Cqb15 february 20121 kg = 22 lbs045 kg = 1 lb

Question 54-40 : A pressure of 101325 hpa is corresponding to ?

145 psi et 2992 inhg.

A pressure of 101325 hpa is corresponding exactly to 1469596432068 psi and 2992 inches of mercury