13.8 Instruments Flashcards

Question

Absolute pressure Gauge pressure Differential pressure

Answer 1

Absolute pressure is the measure of the barometric pressure + gauge pressure Gauge pressure reads the relative pressure above the ambient atmospheric pressure Pabs = Pg + Pabs Diff pressure is the difference between internal cabin pressure and external pressure for aircraft

Answer 2

Is the pressure of a gas when the gas is stationary (Altitude)

Answer 3

Is the component of fluid pressure that represents fluid kinetic energy

Answer 4

Combines dynamic pressure and static pressure (Air speed)

Answer 5

Reduces with altitude Density = mass/volume Grams or kg per cubic metre Pounds per cubic feet

Answer 6

Is dependant on air temperature Higher the air temp the higher the speed of sound Standard sea level speed of sound 340m/s 661K

Answer 7

Is the ratio of the speed of aircraft to the local sound speed and expressed as a Mach number Mach number = aircraft speed/sound speed

Answer 8

For a given airspeed will depend on altitude. As altitude increases the Mach number also increases because of the lowering of the local sound speed

Answer 9

Used in aerodynamics Is the lowest mach number at which the airflow over some point of the aircraft reaches the speed of sound but does not exceed its Mcrit is a fixed value for any given aircraft design and configuration and is always less than 1.

Answer 10

Pressure at MSA - 1013.25HPA Temperature at MSA - 15c (288K) Density at MSA - 1.225kg/m3 Temp lapse rate (tropopause) 1.98c per 1000ft Temperature lower stratosphere -56.5c (216.7k) Sound speed at MSA - 340m/s (661k) Gravity 9.81m/s

Answer 11

Parameter controls the resistance when it changes so does the resistance output

Answer 12

120 degree separation between phases Voltage in the stator coils depends on the angles between the rotor coil and each stator coil. When we turn the rotor the magnetic field in the stator also turns and the voltages in the stator coils change Voltage reference relates to angular position

Answer 13

Change linear position information into electrical signals Flight control surface position

Answer 14

Two stators @ 90 degree to each other Produce a sine and cosine as the rotor is turned Can give a angular position Eg throttle lever position

Answer 15

Magnetic unit that is used as a error detector in systems in which the load is not required to move through large angles

Answer 16

Change angular position into electrical signals

Answer 17

Anytime there is a difference between the two signals the motor drives the load and feedback until both signals are equal Polarity of difference signal decides the direction of rotation

Answer 18

More torque use AC motor A chopper circuit makes AC from a DC signal, to drive the AC motor with this signal we need an extra amplifier. System then runs like a DC system

Answer 19

The AC two phase induction motor servo motor may be very small but powerful Stator has two fields they are represented symbolically by two coils drawn at right angles to each other Counter clockwise rotation - variable field angle 0 degree 400hz and other field at 90 degrees Clockwise rotation - variable signal reversed Braked - disconnect either the variable or fixed field

Answer 20

Aneroid capsule Air pressure increases capsule thickness decreases Air pressure decreases the capsule expands

Answer 21

Is measured from a existing barometric pressure and is the pressure that has been added to a fluid over and above atmospheric pressure

Answer 22

Flattens curved Bronze tube sealed at one end and connected to a gear at the other, as the pressure increases the tube straightens which turns the gear and pointer Used for high pressure systems like oil pressure

Answer 23

Lower pressures such as instrument air pressure are measured with a bellows mechanism. Similar to a aneroid capsule but opposite Air pressure increase the bellows expands Air pressure decreases bellows contracts Sector gear drives a pointer

Answer 24

Uses a differential bellows Takes two pressures and indicates the difference

Answer 25

Resistance changes as force is applied Piezo resistive

Answer 26

As a parameter increases or des read so does the frequency output

Answer 27

Bimetallic strip - 2 strips welded together then as heated one expands and moves the pointer Gas expansion of a bourden tubes

Answer 28

NTC - resistance decreases with increase in temp PTC - resistance increases with increase in temp Temp sensing bulb - resistance increases with increase in temp

Answer 29

Chromel alumel Compares reference junction to hot junction Uses voltage produced from the thermocouple to determine the temp diff between the hot and cold junction

Answer 30

Reed switches Magnetic floats Variable resistor Tank unit Current measure Ratio meter to minimise error

Answer 31

Uses a probe which uses the fluid level for the dielectric More fluid equals higher capacitance

Answer 32

Uses ultrasonic pulses to send receive signals using time taken to reflect for measurement, also needs to know density Water can effect the system Works similar to capacitance

Answer 33

Leading edge of wing detector penetrates are flow, when lift stagnates and stalls it allows the switch to make causing the stall warning alert

Answer 34

Alerts the crew to a imminent stall by setting the shakers off and also the alerting annunciation and aurals Some aircraft also have stick pushers

Answer 35

Sends Aircraft attitude and AOA data to the stall warning computer Vane moves a internal synchro for the position signal Can indicate on the EFIS Heated Lightning strike inspection to make sure they are still free moving and not arc welded together

Answer 36

Air speed Altitude Compass

Answer 37

Airspeed Altitude (adjustable) Compass Attitude indicator Directional gyro Rate of turn Clock VSI

Answer 38

Pressure decreases with altitude Nonlinear 1Hpa per 28ft

Answer 39

Pitot goes straight to the airspeed indicator Two flush static ports and sometimes takes internal cockpit pressure on a unpressurised fuselage

Answer 40

More complex system Uses CAPT, FO and Aux ports Air data modules used

Answer 41

Ram air pressure Electrically heated

Answer 42

Uses static air for sensing Positioned so that the airflow is not disturbed around the port Position error is compensated by fitting ports to both sides of the aircraft to statically balance In event of yaw side slip etc

Answer 43

Temperature of the Undisturbed air around the aircraft. TAT temp + M number to calculate Used to calculate true airspeed

Answer 44

Used for engine power settings Compressed air temperature Difference between SAT and TAT is the ram rise Ram rise is negligible below M.2 Over Mach .2 air speed increase the temp is higher than still air temperature due to kinetic heating and adiabatic heating

Answer 45

Uses the principle of a barometer with gears and pointers attached Indicates in feet Aneroid barometer reads altitudes using static air pressure Some have adjustable Barosettings to adjust for local pressure altitudes QNH local air pressure at mean sea level QFE height aviver ground at the airfield

Answer 46

Uses a stack of bellows to drive the pointers

Answer 47

Uses a minimum of two aneroid capsules to increase accuracy

Answer 48

Takes mean sea level pressure 29.92” or 1013 mb usually set at 10,000ft for aircraft separation

Answer 49

Indicates 0 on the altimeter whilst on the ground at the airfield

Answer 50

corrected pressure for sea level

Answer 51

Large needle 1000ft Small fat needle 10,000ft Fitted with a vibrator to reduce lag and sticking

Answer 52

Sends altitude data to the transponder for reporting

Answer 53

Approaching selected altitude 900ft to go alt light on the altimeters comes on Deviating 200ft from selected altitude sets off the alert

Answer 54

FL 290-410 Allows 1000ft separation +/- 25ft at 5000ft +/- 125ft at 50,000ft Minimum equipment Two primary altitude measurement systems One auto altitude control system One altitude alerting device Transponder system

Answer 55

Baro set standard and must be within limits

Answer 56

Is essentially a lagging of the indication caused by the deflection of the metal in the diaphragm not keeping up with the pressure changes

Answer 57

Error shows up by the altimeter not returning to its original reading after the hysteresis test

Answer 58

Non servo altimeters test how much friction is needed to keep the instrument reading accurately

Answer 59

Performed at 18,000ft pressure to be sure it does not leak more than 100ft in one minute

Answer 60

Test determines that the movement of the barometric scale has the proper effect on the pointers

Answer 61

It is vented to the inside of the case through a diffuser which is a calibrated leak. (Altimeter sealed or evacuated) Aircraft climbs pressure inside the capsule begins to decrease to a value below the inside of the case and the capsule compresses causing the gears and pointers to indicate

Answer 62

Principle of operation formula PT= 1/2pV2 + PS

Answer 63

Is a differential pressure gauge that measures the difference between the pitot and static pressure. In a airtight case in which a thin metal capsule is mounted PT taken into the capsule and internal case uses PS The capsule expands in proportion to the difference between PT & PS which then drives gears and pointers

Answer 64

Diff pressure varies with the square of speed Uses a tuning spring to compensation

Answer 65

1.15 miles 1.8km

Answer 66

Is the indicated pitot static airspeed without any compensation or error correction

Answer 67

Is indicated airspeed corrected for instrument errors position error and installation error

Answer 68

The speed at sea level

Answer 69

True airspeed differs from equivalent air speed because it hr air speed indicators are calibrated at seal level ISA conditions Corrected for density

Answer 70

Ground speed is the true airspeed corrected with wind speed and represents the speed of an aircraft relative to the ground

Answer 71

TAS / local speed of sound Which changes with altitude

Answer 72

Uses Vmo and MMO for over speed warning

Answer 73

Used in place of direct reading indicators (EFIS) Pitot static computers Gyroscopes Accelerometers TAT Air data modules take in analogue raw data then convert it to arinc and send it to relèvent sources

Answer 74

Spins and has two characteristics Rigidity (position) Directional/horizon/ position gyros Provides stable reference for direction and attitude measurement Precision (rate) Turn and slip / turn coordinators Force applied is effected at 90 degrees to the force The amount of precision is equal to the amount of force applied

Answer 75

Vertical gyro 2degrees of freedom Angular displacement from vertical direction Artificial horizon / attitude reference / weather radar Directional gyro 2D of freedom Sensing angular displacement of horizontal direction azimuth heading Compass / heading Rate gyro 1d of freedom Senses Aircraft angular rate of all 3 axis Turn & slip / turn coordination Rate integrating gyro 1d of freedom Platform stabilisation for INS Sensing the Integral of aircraft angular rate

Answer 76

Air Electric motors Spinning balls

Answer 77

Directional gyro must be set to agree with the magnetic compass and it too must be checked periodically At least every 15 mins to make sure it hasn’t drifted our agreement with the compass

Answer 78

Heading indicator combined with VOR/ILS DISPLAY Usually under the artificial horizon VOR indicator left/right to from indicators

Answer 79

Any deviation of the gyro spin axis from its set direction is known as gyro wander (drift)

Answer 80

Any physical deviation of the gyro spin axis Assy metrical bearing friction, unpredictable or able to compensate for

Answer 81

Gyro spin axis does not physically wander away from its preset direction but to an observer it will appear to change direction Because the gyro maintains its direction with respect to a fixed point in space 360 d a day 15 degrees an hour

Answer 82

Directional gyro drift Earth rate apparent drift 15d an hour x sin latitude Vertical gyro drift Earth rate apparent drift 15d an hour x cos latitude

Answer 83

Mounted in a double gimbal and has freedom about 2 axis

Answer 84

Single gimbal freedom about one axis

Answer 85

Replaces mechanical gyros With sensors on the 3 axis and linked to the EFIS Must be connected to a magnetometer Can be combined with air data ADAHRS

Answer 86

2 minute 3 degree second 4 minute 1.5 degree second 2 min turn standard for light aircraft 4 min turn standard for heavy aircraft

Answer 87

Similar to a turn and slip but gimbal axis is tilted 30 degree so it will read when the aircraft rolls and yaws

Answer 88

Some aircraft you pneumatic gyro systems Electrical or Venturi systems

Answer 89

Uses oil in the air system via a metered pump and is discharged with the air Low altitude Steel vanes in a steel housing

Answer 90

Carbon vanes remove the friction of steel on steel High altitude

Answer 91

Speed is between 6000 and 20,000 rpm

Answer 92

Cheap Easy to maintain Operate without power Higher rigidity is possible Operating RPM is more consistant Performance is not affected by altitude I formation transmitted to other systems More freedom about the axis Instrument case completely sealed

Answer 93

Requires being at operating speed for full rigidity Rotor speed depends on mass flow Ingested dirt or moisture will create corrosion and bearing wear Requires a air tight system to operate

Answer 94

To compensate for inclination (tilting) the compass float is weighted on the side nearest the equator Variation is the difference from a geographical pole to the magnetic poles they are compensated for on aeronautical maps Deviation caused by the magnetic influences of the compass mounted on the aircraft. A compass swing is performed to minimise deviation and residual deviation is compensated for by use of a deviation card Soft (earths mag field acting on a material) and hard (permanent) magnetism Total deviation = A + B sin heading + C cos heading

Answer 95

Deviation card must be near the instrument and show deviation of mag heading no more than 45 d increments Compass after compensation must not greater than 10 degree deviation Distance between the compass and any interference shall be so that it doesn’t cause more than 1degres of deviation Any flight control or undercarriage movement will not cause more than 1degree movement The effect of the aircraft permanent and induced magnetism as given by coefficients B & C together with any associated soft iron components shall not exceed A) after correction the greatest deviation on any heading shall be 3D for direct reading compasses and 1D for remote indicating compasses B) emergency standby compasses and non mandatory compasses need not fully comply with EASA regs but evidence of satisfactory installation is required

Answer 96

On aircraft acceptance New compass fitted Periodically every 3 months Major inspection Following a change in magnetic material of the jet If aircraft is moved to a new airfield Following a lightning strike or heavy static If stood on the same heading for more than 4 weeks When carrying ferrous freight Iaw MPD When compass deviation is suspected

Answer 97

Mechanical Electrical

Answer 98

Uses a flux valve in the wing tip or tail which uses earths flux lines to give readings With a directional gyro Manual synchronising knob

Answer 99

Required with MTOW greater than 5700kg and 9 pax Must retain at least the last 25 hours 10 hours is MTOW is less than 5700kg Records: Altitude Airspeed Heading Attitude pitch and roll Acceleration Thrust/power settings Config of lift drag devices Radio transmission keying Use of AFCS AOA Air temperature Aircraft MTOW greater than 27,000kg also has to record Primary flight control positions Pitch trim Primary nav info as per EFaiS to crew Flight deck warnings Landing gear position Radio altitude Must be recording when the aircraft is capable of moving under its own power Engine start to 5 mins after shutdown 27000kg 32 channels Less than 5700kg 15 channels Preflight test switch Bite Under water locator beacon 37Khz lasts 30 days Parameter input formats Analogue Digital Discrete Positioned in a place that will minimise as much as possible Damage Fire Heat Shock Powered by hot battery bus usually

Answer 100

PFD MFD EIS On light aircraft sometimes the EIS is combined into the MFD

Answer 101

Two options Autopilot built in Autopilot separate Two SD slots Top NDB & software loading Bottom terrain databases MEMS technology solid state sensors to provide attitude and heading references Magnetometer digital compass Transponder minimum mode C

Answer 102

Engine indicating crew alerting system Will give cautions warnings memos status Electronic centralised aircraft monitoring will give a fault and resolution and serves primary systems

Answer 103

Level 1-3 failure Level 1 - failure to system that degrades it (amber light) Level 2 - system failure but no direct consequence to flight safety (amber light single chime) Level 3 - over speed, fire, stall (red warning repetitive chime) Data displayed in schematic checklist format

Answer 104

Class B - 4 functions Foward looking terrain avoidance looks forward and down Premature decent alert Attention alerts Class A - 5 functions Terrain awareness display

Answer 105

Mode 1 - excessive decent rate 2450 ra and below Mode 2 - terrain rising rapidly Mode 3 - sink rate TOGA Mode 4 - landing configuration for landing terrain closure Mode 5 - ILS glideslope Mode 6 - alerts minimums, DH, bank angle Mode 7 - (optional) wind shear

Answer 106

Solid red - warning terrain approx 30s to collision Solid yellow - caution terrain approx 60s to impact 50% red dots - more than 2000ft above ref altitude 50% yellow dots - 1-2000ft above ref altitude 25% yellow dots - 500-1000feet above ref altitude 25% green dots - 500-1000ft below ref altitude 12.5% green dots - 1000-2000 feet below ref altitude Black - no close terrain Magenta - unknown terrain

Answer 107

Modifies terrain database for recognised airfields to cancel nuisance warnings

Answer 108

Traffic information service - using ADS-B to transmit the traffic position information from a ground facility to the aircraft which displays it on the PFD and MFD Traffic advisory system - this is an indépendant airborne system utilising directional antennas and a suitable mode S transponder

Answer 109

Fitted to all aircraft MTOW greater than 5700kg and carrying more than 19 pax Directional antennas Transponder mode s

Answer 110

ASI Attitude indicator Altimeter Heading indicator