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Tyskland NOTES > Avionics > Flashcards

Avionics Flashcards

1
Q

What is an Ion?

A

-A positive or negative charged atom
- Unequal number of electrons and protons

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2
Q

Why are atoms electrically neutral?

A

Equal number of electrons and protons

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3
Q

Explain the term electric current. When does it occur? Name the unit of measurement.

A

-Charge/time = current
- Ampere

I = Q / t

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4
Q

Explain the term electric voltage. Name the unit of measurement

A

-Potential difference
- Volt

Two points with different electric potential

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5
Q

What is electric power? Name the unit of measurement

A
  • product of voltage and current
  • Watt

P = U * I
Product of you U and I

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6
Q

What is electric work? Name the unit of measurement

A
  • Power*time = work
  • Watt hour

W = P * t = U * I * t

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7
Q

What is an insulator or electric nonconductor? Give two examples

A
  • No free electrons = no current possible
  • Rubber, air
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8
Q

What is the special characteristic of an electric semiconductor? Give an example of device which use semiconductors.

A

A semiconductor conducts electricity only under certain conditions.
Example of material: silicon

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9
Q

What is an electric conductor? Give two examples

A
  • Material with few electrons in outer shell
  • Copper, aluminium
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10
Q

Describe the single-pole conductor configuration. What are the advantages of this configuration for aircraft design?

A
  • Less weight and negative power supply via cable
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11
Q

Every conductor has an ohmic resistance. It depends on:

A

Conductor length
Material
Temperature
Cross section

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12
Q

What is a galvanic element?

A

two metals, base and nobel, in an electrolyte connected by a conductor

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13
Q

Name two types of galvanic elements

A

Noble, base
E.g. Zinc and copper

Primary cells
- Galvanic elements which will be destroyed upon discharge

Secondary cells
- Galvanic elements whose chemical change can be reversed (Recharging)

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14
Q

Two identical batteries are connected in parallel. What happens?

A

The total voltage equals the voltage of one battery

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15
Q

What are the tasks of a rechargeable battery in an aircraft?

A
  • Supply the electrical system with power, without generators running (before startup, failure of generators)
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16
Q

What may happen to a battery, if the charging current is too high?

A
  • Battery warms up = kaBOOOM
  • Electrolyte escapes
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17
Q

Define the term “capacity of batteries” and state the unit of measurement used?

A
  • How long a battery can supply power with a given voltage and current.
  • Ampere hour (Ah)
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18
Q

How long can a battery supply a system with a load of 30A, if the capacity is 40Ah?

A

40/30 * 60 = 80min = 1h 20min

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19
Q

What is the nominal voltage of a battery commonly used in a helicopter?

A

24V (the generator = 28V)

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20
Q

Two identical batteries are connected in series. What happens?

A

The total voltage is twice of the battery voltage

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21
Q

Describe the working principle of a simple DC generator and name its main components.

A

A conductor loop is rotating in a magnetic field perpendicular to the magnetic flux lines and a voltage is induced and picked up by a commutator.

Commutator, loops, electromagnet (+exciting current)/permanent magnet

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22
Q

What is the purpose of a DC generator in an aircraft electrical system?

A

Supply electrical system with power and charges the battery during flight

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23
Q

Name three different types of DC generator excitation and their subgroups, if there are some.

A
  • Separately excited
  • Directly excited
  • Self excited (series; shunt; compound)
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24
Q

Name three different types for the design of voltage regulators

A
  • Vibrating
  • Carbon pile
  • Transistorized
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25
Q

State two functions of a circuit breaker

A

Interrupts current - during overloads or short circuits to protect the circuit.

Resets easily - to restore power after a fault is cleared

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26
Q

Circuit breakers…

A

Are switches, which are combined with a bimetal and/or solenoid

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27
Q

Why are two main generators connected in a parallel circuit in an aircraft?

A
  • If one fail, the other can take over.
  • One generator for start up and power supply, one for power supply only
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28
Q

What are the tasks of an external power unit?

A
  • Supply electrical power for startup
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29
Q

What is the advantage of splitting the load into different busses (DC power distribution)?

A
  • In case of failure of the generators, necessary electrical subsystems can be supplied with power and non necessary parts can be shut down
  • Failure in one bus doesn’t harm the whole electrical distribution
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30
Q

Which devices are used for monitoring the electrical system of the aircraft? State which parameters are used to monitor an electrical system.

A
  • Voltmeter: 24V/28V indicates if the generators are active
  • Amperemeter: Indicates the total load of the electrical system
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31
Q

What is the purpose of an inverter in an electrical system powered by DC generators?

A

Invert DC voltage to AC voltage

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32
Q

Name two types of inverters

A
  • Rotating inverter
  • Static inverter
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33
Q

What are the nominal voltage and frequencies of an AC system used in helicopters?

A
  • 115V 400Hz
  • 26V 400Hz
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34
Q

Which different color marking are painted on instruments? What is their meaning?(5)

A
  • Green: Normal operating range, proper operation is assured
  • Yellow: Caution range, unsafe operating conditions, time limited, monitored constantly, unreliable Reading
  • Red: Warning range, danger, outside permissible limits, requires immediate corrective action, (transient limit)
  • White: slippage marking, joint between instrument case and cover glass
  • Barbershop (White red): Max autorotation speed
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35
Q

What is static pressure, dynamic pressure and total pressure?

A
  • Static pressure: pressure from all sides
  • Dynamic pressure: generated by speed
  • Total pressure: Both pressures added
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36
Q

Name three pressure units

A
  • hPa
  • Bar
  • mmHg
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37
Q

Which pressure is measured by the Pitot-tube?

A

Total pressure

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38
Q

Why is a heater for the Pitot-tube necessary?

A

Icing in clouds or moist cold air. To burn away insects and other solids.

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39
Q

Describe the design and operating principle of the barometric altimeter (important components, sensed pressure)

A

Aneroid vafer with fixed pressure.
Housing is connected to the static ports
The Vafer is connected to a pointer via mechanical linkage.
You set the chosen QNH in the kollsman window.

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40
Q

Some barometric altimeters are equipped with an altimeter encoder. What is the task of the altimeter encoder?

A

To give the digital system altitude information

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41
Q

What is the task of an electrical vibrator located in an altimeter with encoder?

A

higher accuracy

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42
Q

What happens if the power supply of the altimeter fails?

A
  • No encoding = transponder can’t send altitude information
  • No vibration = less accuracy
43
Q

What is the ratio between the units “feet” and meter”?

A

1 m : 0,3048 = 3,28 feet

44
Q

What is the difference between CALIBRATED ALTITUDE and INDICATED ALTITUDE?

A

Calibrated altitude is the indicated altitude corrected by the instrument and installation errors.

45
Q

Name both values needed to calculate the TRUE ALTITUDE from the CALIBRATED ALTITUDE

A
  • Outside air temperature (OAT)
  • Pressure altitude (Density)
46
Q

How can you measure the OAT and the PA in the aircraft?

A
  • OAT : ambient air thermometer
  • Pressure altitude : set kolsmann windows 1013,25 = indicated altitude
47
Q

Explain why the TRUE ALTITUDE differs from the CALIBRATED ALTITUDE

A

Instruments are calibrated for ISA standard atmosphere. 15 degrees C; 1013,25 hPa. Real weather differs. So in short; because of shitty german weather.

48
Q

What is QNH?

A

Height above MSL

Pressure on airfield corrected by ISA (international standard atmosphere) to MSL (Mean sea level)

Gives you an altitude

49
Q

What is QFE?

A

Pressure on airfield (field elevation)

Gives you a height

50
Q

What is QNE?

A

Equals pressure altitude (PA) = 1013,25hPa

51
Q

What happens to the altitude indications if the static ports are blocked?

A

Freezes

52
Q

Describe the design and operating principle of the differential capsule vertical speed indicator. Which pressure is required for the indication?

A

Diaphragm connected to the static port.
Casing with a calibrated leak.
Mechanical linkage and a pointer

Lag between pressure change in diaphragm and casing
Can be minimized with an accelerometer

53
Q

Name the unit for vertical speed in aviation.

A

Feet/minute

54
Q

Describe the design and operating principle of the airspeed indicator (important components, used pressure)?

A

Diaphragm connected to the pitot tube measuring total pressure.
Casing connected to the static port measuring static pressure

55
Q

Name the unit for horizontal speed in aviation

A

Knots

56
Q

State the relationship between the horizontal speed in aviation and km/h

A

1 knot = 1,852 km/h

57
Q

What is CALIBRATED AIRSPEED?

A

Indicated airspeed corrected by instrument and installation errors

58
Q

What is TRUE AIRSPEED

A

Calibrated airspeed corrected by OAT and PA. The actual speed you are moving through the air.

59
Q

What is the meaning of VNE

A

Velocity never exceed

60
Q

Name three reasons for incorrect indications of the airspeed indicator

A
  • Rotor downwash if speed less than 25 KIAS
  • blocking of static ports or pitot tubes
61
Q

Complete the table. What is shown by the indicators?

A

Look at the giant table in your papers

62
Q

Name the inputs needed by the AIR DATA COMPUTER and the outputs which are calculated by the ADC?

A

Inputs:
Static pressure
Total pressure
QNH
(OAT)

Outputs:
Calibrated altitude
IAS, CAS, (TAS)
(OAT)
Values for the autopilot

63
Q

Describe the design and operating principle of the radar altimeter

A
  • The transmitter sends a radar signal via an antenna in a cone to the ground. The signal is reflected by the ground and received via an antenna and guided to a receiver. The receiver measures the time and converts the fastest signal to distance via the value for speed of light. This is the indicated distance.
64
Q

When is the red warning flag in the radar altimeter displayed?

A
  • Radar receiver receives no signal
  • Turned off
  • Failure (no power supply, …)
65
Q

What is the gyroscopic property of a semi rigidly mounted gyro? How many degrees of freedom does it have?

A

Gyroscopic precession
2 degrees of freedom.

66
Q

What is the gyroscopic property of a universally mounted gyro? How many degrees of freedom does it have?

A

Rigidity in space
3 degrees of freedom.

67
Q

Name 3 gyroscopic instruments operated by fully gimbaled gyros

A
  • Artificial horizon
  • Vertical gyro
  • Directional gyro
68
Q

What is the attitude of the spin axis and the degree of freedom of a Gyromagnetic compass? Artificial horizon? Turn indicator? Vertical gyro?

A

Gyromagnetic compass; Horizontal plane/ 3
Artificial horizon; Vertical /3
Turn indicator; Lateral /2
Vertical gyro; Vertical /3

69
Q

What is measured and indicated by the artificial horizon?

A

Pitch and bank
Measured in degrees

70
Q

Explain what can be set using the cage knob located at the housing of the artificial horizon

A

The spinning axis can be set up in vertical direction

71
Q

What could be the reasons for using the pitch offset knob at the artificial horizon?

A
  • Forward or aft loading
  • For comfort under long cruising flights/making life easier during instrument flying
72
Q

What is the difference between the vertical gyro and the artificial horizon? (NOT IN EXAM)

A

Vertical gyro digitalizes its data for electrical systems and can be mounted somewhere else

73
Q

What is a standard rate turn?

A

3 degrees / sec
= 2min for 360 degrees

74
Q

What is shown by the ball of the slip indicator?

A

The ball shows if you are flying coordinated (the needle shows angular speed)
Slip or skid

75
Q

On which pedal should be stepped when the ball is on the left hand side?

A

Left pedal (step on the ball!)

76
Q

Describe the operating principle of a laser gyro (rough description)

A

Light is emitted and separated in both ways of the circuit and the intensity is the value for the rate turn. (His. Exact. Words.)

77
Q

What are the advantages of a laser gyro compared to a mechanical gyro?

A

No moving parts, higher accuracy, lighter and less maintenance

78
Q

How can torque be measured by the use of inductive sensors?

A

Inductive sensors measure torque by detecting magnetic field changes as the shaft twists.

79
Q

Name two other (other than inductive sensors) possible ways of measuring torque in a helicopter

A
  • Hydraulic sensors
  • Piezzoelectric pressure sensors
80
Q

Explain the operating principle of a mast moment measuring system

A

A mast moment measuring system uses strain gages to detect mast bending, converting it into signals to monitor and prevent overstress.

81
Q

What kinds of rpm’s are measured in a helicopter? What is the reason for this?

A
  • Rotor RPM; Rotor monitoring, autorotation
  • N1 RPM = Engine compressor RPM = Gas producer
  • N2 RPM = Engine turbine RPM
82
Q

Explain the design and operating principle of a three phase RPM indicator(tachogenerator)

A

Alternator(tachogenerator) connected via electric lines to syncro motor, eddy current bell, spring, pointer with scale.

83
Q

What is the difference between a three phase RPM indicator and a short distance RPM indicator?

A

Short distance: no electric lines

84
Q

Explain the design and operating principle of a RPM indicator working with an inductive sensor

A

Phonic wheel connected to solenoid, signal pulses, frequency indication for RPM
(Like a speed sensor on a bike)

85
Q

What kinds of pressures are measured in an aircraft besides air pressure?

A
  • Oil: Transmission, engine
  • Fuel pressure
  • Hydraulic pressure
86
Q

Name two mechanical and two electrical pressure sensors (without air data sensors)

A

Mechanical:
- Bourdon tube
- Mechanical linked resistor

Electrical:
- Strain gauges
- Piezo electric

87
Q

Explain the operating principle of a piezzo-electric pressure sensor

A
  • Pressure acts on crystal = deformation = electrons are shifted within the crystal
  • Voltage can be measured on the surface of each side of the crystal
  • With constant pressure and thereby constant deformation there is no voltage
88
Q

Why could it be necessary to measure vibrations in some aircrafts?

A

To detect engine damage before failure

89
Q

An A/C DC system with 28 VDC has one consumer load. A second one shall be connected in series. What does that mean for the total ohmic resistance and the total electric current flowing?

A

The total resistance increases
The total electric current flowing decreases

90
Q

What causes static charge of an A/C in flight?

A

Friction with the air/wind

91
Q

Name three negative effects of static charge of an A/C

A

Hoist operations
Air refueling
Landing

92
Q

Calculate Rtot, U, P and W for 10 hours

________[R1=4 ohm]________
| | |
( V ) = ( A )
| | |-[R2=3 ohm]-| |
————— |-|
|-[R3= 6 ohm]-|

I=24 A

A

Rtot=
1/(R1+2)=1/3 +1/6 = 2/6 + 1/6 = 3/6
R1+R2= 6/3=2

Rtot =2+4=6 ohm

U=RI=624=144 volt

P=U*I=144v *24A= 3456 W =3,456 kW

W=ptime=3,456 kW10 hours=34,56 kWh

93
Q

How does “voltage control” act on the generator in order to keep the output voltage constant

A

Voltage control adjusts the generator’s magnetic field to keep output voltage steady.

94
Q

When does reverse current flow from battery to generator occur?

A

When battery power is higher than generator power due to an electrical failure

95
Q

Explain why reverse current flow from the battery to the generator must be prevented

A

The battery might be drained

96
Q

Name two devices for preventing reverse current flow

A

Relay and diode

97
Q

What are the tasks of a starter /generator in an A/C

A

Starter: start the engine
Generator: generates power to the electrical system

98
Q

Define the term variation

A

Different between magnetic and true north

99
Q

Define inclination

A

Angle between flux lines and the surface of the earth

100
Q

What is an isoclinic line

A

Lines with the same inclination

101
Q

What are the two main components of a gyro magnetic system

A

Directional gyro and magnetic flux valve

102
Q

What is the purpose of a magnetic flux valve

A

To detect the flux lines and to make the directional gyro More precise

103
Q

Explain the operating principle of the temperature sensors! Name the temperature range (low, med, high) and give an example!

Thermocouples:

Thermistors:

Bimetals:

A

Thermocouples:
Difference in potential
High temp
Engine/turbine

Thermistors:
Change in resistance due to temperature changes
Medium temp
Oil

Bimetals:
2 different metals together. 1 expands more than the other and will therefore bend.
Low temperature
OAT

104
Q

Name the two types of fuel quantity gauges

A

Floater
Capacitive fuel sensor

Tyskland NOTES (24 decks)

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