Avionics Flashcards
1
Q
What is an Ion?
A
-A positive or negative charged atom
- Unequal number of electrons and protons
2
Q
Why are atoms electrically neutral?
A
Equal number of electrons and protons
3
Q
Explain the term electric current. When does it occur? Name the unit of measurement.
A
-Charge/time = current
- Ampere
I = Q / t
4
Q
Explain the term electric voltage. Name the unit of measurement
A
-Potential difference
- Volt
Two points with different electric potential
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
6
Q
What is electric work? Name the unit of measurement
A
- Power*time = work
- Watt hour
W = P * t = U * I * t
7
Q
What is an insulator or electric nonconductor? Give two examples
A
- No free electrons = no current possible
- Rubber, air
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
9
Q
What is an electric conductor? Give two examples
A
- Material with few electrons in outer shell
- Copper, aluminium
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
11
Q
Every conductor has an ohmic resistance. It depends on:
A
Conductor length
Material
Temperature
Cross section
12
Q
What is a galvanic element?
A
two metals, base and nobel, in an electrolyte connected by a conductor
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)
14
Q
Two identical batteries are connected in parallel. What happens?
A
The total voltage equals the voltage of one battery
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)
16
Q
What may happen to a battery, if the charging current is too high?
A
- Battery warms up = kaBOOOM
- Electrolyte escapes
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)
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
19
Q
What is the nominal voltage of a battery commonly used in a helicopter?
A
24V (the generator = 28V)
20
Q
Two identical batteries are connected in series. What happens?
A
The total voltage is twice of the battery voltage
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
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
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)
24
Q
Name three different types for the design of voltage regulators
A
- Vibrating
- Carbon pile
- Transistorized
25
State two functions of a circuit breaker
Interrupts current - during overloads or short circuits to protect the circuit.
Resets easily - to restore power after a fault is cleared
26
Circuit breakers...
Are switches, which are combined with a bimetal and/or solenoid
27
Why are two main generators connected in a parallel circuit in an aircraft?
- If one fail, the other can take over.
- One generator for start up and power supply, one for power supply only
28
What are the tasks of an external power unit?
- Supply electrical power for startup
29
What is the advantage of splitting the load into different busses (DC power distribution)?
- 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
30
Which devices are used for monitoring the electrical system of the aircraft? State which parameters are used to monitor an electrical system.
- Voltmeter: 24V/28V indicates if the generators are active
- Amperemeter: Indicates the total load of the electrical system
31
What is the purpose of an inverter in an electrical system powered by DC generators?
Invert DC voltage to AC voltage
32
Name two types of inverters
- Rotating inverter
- Static inverter
33
What are the nominal voltage and frequencies of an AC system used in helicopters?
- 115V 400Hz
- 26V 400Hz
34
Which different color marking are painted on instruments? What is their meaning?(5)
- 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
35
What is static pressure, dynamic pressure and total pressure?
- Static pressure: pressure from all sides
- Dynamic pressure: generated by speed
- Total pressure: Both pressures added
36
Name three pressure units
- hPa
- Bar
- mmHg
37
Which pressure is measured by the Pitot-tube?
Total pressure
38
Why is a heater for the Pitot-tube necessary?
Icing in clouds or moist cold air. To burn away insects and other solids.
39
Describe the design and operating principle of the barometric altimeter (important components, sensed pressure)
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.
40
Some barometric altimeters are equipped with an altimeter encoder. What is the task of the altimeter encoder?
To give the digital system altitude information
41
What is the task of an electrical vibrator located in an altimeter with encoder?
higher accuracy
42
What happens if the power supply of the altimeter fails?
- No encoding = transponder can't send altitude information
- No vibration = less accuracy
43
What is the ratio between the units "feet" and meter"?
1 m : 0,3048 = 3,28 feet
44
What is the difference between CALIBRATED ALTITUDE and INDICATED ALTITUDE?
Calibrated altitude is the indicated altitude corrected by the instrument and installation errors.
45
Name both values needed to calculate the TRUE ALTITUDE from the CALIBRATED ALTITUDE
- Outside air temperature (OAT)
- Pressure altitude (Density)
46
How can you measure the OAT and the PA in the aircraft?
- OAT : ambient air thermometer
- Pressure altitude : set kolsmann windows 1013,25 = indicated altitude
47
Explain why the TRUE ALTITUDE differs from the CALIBRATED ALTITUDE
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
What is QNH?
Height above MSL
Pressure on airfield corrected by ISA (international standard atmosphere) to MSL (Mean sea level)
Gives you an altitude
49
What is QFE?
Pressure on airfield (field elevation)
Gives you a height
50
What is QNE?
Equals pressure altitude (PA) = 1013,25hPa
51
What happens to the altitude indications if the static ports are blocked?
Freezes
52
Describe the design and operating principle of the differential capsule vertical speed indicator. Which pressure is required for the indication?
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
Name the unit for vertical speed in aviation.
Feet/minute
54
Describe the design and operating principle of the airspeed indicator (important components, used pressure)?
Diaphragm connected to the pitot tube measuring total pressure.
Casing connected to the static port measuring static pressure
55
Name the unit for horizontal speed in aviation
Knots
56
State the relationship between the horizontal speed in aviation and km/h
1 knot = 1,852 km/h
57
What is CALIBRATED AIRSPEED?
Indicated airspeed corrected by instrument and installation errors
58
What is TRUE AIRSPEED
Calibrated airspeed corrected by OAT and PA. The actual speed you are moving through the air.
59
What is the meaning of VNE
Velocity never exceed
60
Name three reasons for incorrect indications of the airspeed indicator
- Rotor downwash if speed less than 25 KIAS
- blocking of static ports or pitot tubes
61
Complete the table. What is shown by the indicators?
Look at the giant table in your papers
62
Name the inputs needed by the AIR DATA COMPUTER and the outputs which are calculated by the ADC?
Inputs:
Static pressure
Total pressure
QNH
(OAT)
Outputs:
Calibrated altitude
IAS, CAS, (TAS)
(OAT)
Values for the autopilot
63
Describe the design and operating principle of the radar altimeter
- 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
When is the red warning flag in the radar altimeter displayed?
- Radar receiver receives no signal
- Turned off
- Failure (no power supply, ...)
65
What is the gyroscopic property of a semi rigidly mounted gyro? How many degrees of freedom does it have?
Gyroscopic precession
2 degrees of freedom.
66
What is the gyroscopic property of a universally mounted gyro? How many degrees of freedom does it have?
Rigidity in space
3 degrees of freedom.
67
Name 3 gyroscopic instruments operated by fully gimbaled gyros
- Artificial horizon
- Vertical gyro
- Directional gyro
68
What is the attitude of the spin axis and the degree of freedom of a Gyromagnetic compass? Artificial horizon? Turn indicator? Vertical gyro?
Gyromagnetic compass; Horizontal plane/ 3
Artificial horizon; Vertical /3
Turn indicator; Lateral /2
Vertical gyro; Vertical /3
69
What is measured and indicated by the artificial horizon?
Pitch and bank
Measured in degrees
70
Explain what can be set using the cage knob located at the housing of the artificial horizon
The spinning axis can be set up in vertical direction
71
What could be the reasons for using the pitch offset knob at the artificial horizon?
- Forward or aft loading
- For comfort under long cruising flights/making life easier during instrument flying
72
What is the difference between the vertical gyro and the artificial horizon? (NOT IN EXAM)
Vertical gyro digitalizes its data for electrical systems and can be mounted somewhere else
73
What is a standard rate turn?
3 degrees / sec
= 2min for 360 degrees
74
What is shown by the ball of the slip indicator?
The ball shows if you are flying coordinated (the needle shows angular speed)
Slip or skid
75
On which pedal should be stepped when the ball is on the left hand side?
Left pedal (step on the ball!)
76
Describe the operating principle of a laser gyro (rough description)
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
What are the advantages of a laser gyro compared to a mechanical gyro?
No moving parts, higher accuracy, lighter and less maintenance
78
How can torque be measured by the use of inductive sensors?
Inductive sensors measure torque by detecting magnetic field changes as the shaft twists.
79
Name two other (other than inductive sensors) possible ways of measuring torque in a helicopter
- Hydraulic sensors
- Piezzoelectric pressure sensors
80
Explain the operating principle of a mast moment measuring system
A mast moment measuring system uses strain gages to detect mast bending, converting it into signals to monitor and prevent overstress.
81
What kinds of rpm's are measured in a helicopter? What is the reason for this?
- Rotor RPM; Rotor monitoring, autorotation
- N1 RPM = Engine compressor RPM = Gas producer
- N2 RPM = Engine turbine RPM
82
Explain the design and operating principle of a three phase RPM indicator(tachogenerator)
Alternator(tachogenerator) connected via electric lines to syncro motor, eddy current bell, spring, pointer with scale.
83
What is the difference between a three phase RPM indicator and a short distance RPM indicator?
Short distance: no electric lines
84
Explain the design and operating principle of a RPM indicator working with an inductive sensor
Phonic wheel connected to solenoid, signal pulses, frequency indication for RPM
(Like a speed sensor on a bike)
85
What kinds of pressures are measured in an aircraft besides air pressure?
- Oil: Transmission, engine
- Fuel pressure
- Hydraulic pressure
86
Name two mechanical and two electrical pressure sensors (without air data sensors)
Mechanical:
- Bourdon tube
- Mechanical linked resistor
Electrical:
- Strain gauges
- Piezo electric
87
Explain the operating principle of a piezzo-electric pressure sensor
- 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
Why could it be necessary to measure vibrations in some aircrafts?
To detect engine damage before failure
89
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?
The total resistance increases
The total electric current flowing decreases
90
What causes static charge of an A/C in flight?
Friction with the air/wind
91
Name three negative effects of static charge of an A/C
Hoist operations
Air refueling
Landing
92
Calculate Rtot, U, P and W for 10 hours
________[R1=4 ohm]________
| | |
( V ) = ( A )
| | |-[R2=3 ohm]-| |
————— |-|
|-[R3= 6 ohm]-|
I=24 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=R*I=6*24=144 volt
P=U*I=144v *24A= 3456 W =3,456 kW
W=p*time=3,456 kW*10 hours=34,56 kWh
93
How does “voltage control” act on the generator in order to keep the output voltage constant
Voltage control adjusts the generator’s magnetic field to keep output voltage steady.
94
When does reverse current flow from battery to generator occur?
When battery power is higher than generator power due to an electrical failure
95
Explain why reverse current flow from the battery to the generator must be prevented
The battery might be drained
96
Name two devices for preventing reverse current flow
Relay and diode
97
What are the tasks of a starter /generator in an A/C
Starter: start the engine
Generator: generates power to the electrical system
98
Define the term variation
Different between magnetic and true north
99
Define inclination
Angle between flux lines and the surface of the earth
100
What is an isoclinic line
Lines with the same inclination
101
What are the two main components of a gyro magnetic system
Directional gyro and magnetic flux valve
102
What is the purpose of a magnetic flux valve
To detect the flux lines and to make the directional gyro More precise
103
Explain the operating principle of the temperature sensors! Name the temperature range (low, med, high) and give an example!
Thermocouples:
Thermistors:
Bimetals:
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
Name the two types of fuel quantity gauges
Floater
Capacitive fuel sensor
