Comms Questions Flashcards
111.1Mhz is a
ILS frequency
What is the time period for intial transmisision of a 406Mhz ELT?
.25s
Aircraft takes off from a 500ft elevated run way to 9500ft what is the approx max range of VHF reception
120 nautical miles
VHF Altitude range
1.23*(sure root of altitude in feet)
RNAV uses what arinc specification
Arinc 583
ILS marker lamp colours are
Outer blue, middle amber, inner white
A loop aerial has
2 null
RVR minimum for a cat 1 approach is
800m
A series tuned circuit is referred to as an ace prior circuit because
Current is maximum at resonance
I’m a class c amplifier, the transistor conducts for
Part of the time
For VHF communications freq range is
118 to 136 MHz with 25Khz spacing
Attenuation along a Hf installation co-axial feeder is due to
Skin effect
The effect of position feedback in an autopilot system ensures that the
Control surface returns to the beaut RAL position when the disturbance is corrected
Single side Andes transmission is achieved by using
Balanced modulator and mechanical filters
Glide slope transmitter operates on
UHF band
BJF and UHF makes use of the
Space wave
Audio sources for the CVR are
Captain, F/O, observer/ flight engineer and flight deck
In an aircraft equipped with mode s the sqwak code is entered
By the control panel
With radar range resolution the only possible way to discriminate separate echos is by
The difference in their delays is greater than the pulse width
111.2Mhz is
VOR
The function of the hi-Lo marker switch is to
Control the sensitivity of the receiver
The signals on a aircraft loop aerial are reproduced in the adf rx by a device known as a
Goniometer
Q-factor is a measure of
Voltage magnification in a series circuit
VOR over station sensor is activated by
Radio rate
I’m an amplifier the term stage gain means the
Gain of one stage only
The accelerometer output in a INS is
Interested twice to give distance
Typical output power of a VHF communication TX is
Between 25 & 40 watts
Decision height is the height at which a. Go around is initiatedif
Visual reference has not been established
As a transmitted frequency is reduced ionospheric penetration is
Reduced
A squelch circuit in a receiver operates the
Audio stage
When carrying out a VSWR check on a communication transmission system a satisfactory reading would be
2:1
Cockpit voice recorder provided a continuous recording of the last
30 minutes
A radars system is transmitted pulses are rated by
Average power
121.5 MHz is a
VHF frequency
112.1Mhz is
A VOR frequency
GPWS mode 2 needs
RA, rate of decent and aircraft configuration
Present position can be entered by the
FMS CDU
The azimuth angle found on the MLS system is
40 degrees
The vertical profile for MLS extends to
30 degrees
With the aircraft coupled to the flight director only when tracking of a VOR beacon
Radio deviation would be the only input
The glide path frequency is
Paired with the localiser frequency
Ok the glide path centreline the received signal is an efficient carrier modulated equally by each tone to a depth of
40%
Decca operates in the frequency range between
70-130khz
In an FD system using fixed angle capture the signal inputs are
Course error and radio deviation
In a FD system with a vertical gyro the signal from the VG
Opposes the heading error signal
If a transistor amplifier is biased to operate in class B conditions it is biased
At cut off
In ADF installations quadrantal error is maximum at
45 degrees
The VOR reference signal is
Frequency modulated
The rad alt signal is primarily used
Ok the final stages of approach down to touch down
I’m a low pass filter the attenuation band is at
Frequencies above the cut off frequency
The Jf band used for long distance communication has a
Wave length between 10 & 100 metres
The space wave
Pénétrâtes thé ionosphère and is lost into space
The phase of a modulator signal corresponds to the
Polarity of a DC input signal
If the I bar of an E and I pick off is out of datum position the
Direction of displacement gives the output phase sense.
A basic INS platform has
2 accelerometers and 3 gyros
The battery in an INS will provide emergency power for
15 minutes
The reference and variable signals of a VOR are compared for
Phase
The localiser output signals from the navigation receiver are
Polarity sensitive DC
If the input power to a 40 dB attenuator is 10 watt, the output power is
100mW
Bonding of aerials is
Normally carried out via the attachment bolts
Selcal may be used with
Both HF and VHF
The sensitivity of a radio receiver is
Normally expressed in microvolts or in decibels below 1V
The aircraft Selcal code is
Allocated by ARINC
Absorption of radio waves due to the ionosphere is the greatest in the
Day
The reflecting layers of the atmosphere rise to a high level during the
Night
A VHF receiver received signals by a
Space wave
If the length of a 1/2 wave dipole is decreased the resonant frequency is
Increased
Cat 2 RVR limits are,
800-400 metres
When flying through a VOR cone of confusion the signals used by the AFCS are
Course select error and drift angle
During an ILS landing the aircraft usually captures
The localiser before the glide slope
When would full scale deflection occur on the course pointer in a VOR
10 degrees of the beam
Precipitation static on a aircraft is due to
Flying through rain snow ice and dust
The carbon microphone
Requires an external voltage for its operation
To receive CW transmission which of the following is required
A beat frequency oscillator
The wheel height at which a go around must be initiated unless it has been visually assessed that is is satisfactory to continue the approach and landing in safety is known as the
Decision height
The runway visual range is obtained by
Multiple set of instruments at the side of the runway
The ICAO weather category 3A is
Operation down to and along the surface of the runway with RVR minima of 200m
A Dual FD system has
2 vertical gyros 2VHF receivers 2 compasses
When testing a FD in heading mode the signals needed are
Heading error and roll
To operate in RHO RHO navigation mode an installation must have
Two DME transponders
A one for deviation on the HSI is equivalent to a
75mV signal
A 1/4 section of transmission line terminated in a short circuit behaves as a
High impedance, reflector circuit
Typical impedance figuiers for a coaxial feeder are
45-75 ohms
The input impedance of a dipole is approximately
73 ohms if centre fed
The input impedance of a folded dipole is
292 ohms
I’m the glide slope mod (FD system) the signals used are
Pitch and glide slope deviation
The glide slope indication on the HSI and ADI has a typical value of
.35 degrees/dot
FD modes maybe
APPR, IAS and V/S
A marker beacon operates on a frequency of
75MHz
Radar range resolution is increased
Only with a increased PRF
ATC system transmissions are
Single channel simplex
The gain of a weather radar system is
Automatically set when altering the range selection
GNSS is made up of a network of satellites arranged
With 4 satellites in 6 orbital planes at 60 degrees
What is a negative outcome of using larger bandwidth or increased range resolution
Pulse energy is reduced
Radar receiver noise is proportional to its
Bandwidth
What factors determine the duty cycle of a radar system
Pulse width x PRF
The time taken for the return pulse of a radio altimeter is
The aircraft height and the time taken to transmit and receive plus the delay from the antenna cable length including any transceiver delay
The carrier frequency of an ILS marker transmitter is
75 MHz
A VOR RMI shows an aircraft on a heading of 030 degrees and the selected VOR radial to be 145 degrees. The relative bearing of the station is
115 degrees
When the INS is first switched on the following two actions must take place
Accelerometers levelled platform orientated to true north
When an aircraft overflies the localiser transmitter the signals received will be
In the same sense
Modulation is a process whereby
Intelligence is impressed in the carrier wave
HIRF protected areas are
Given special additional inspections to the normal airframe inspection program
If an antenna is horizontally polarised it’s plane of polarisation is
The same as it’s electrostatic field
A squelch circuit
Keeps the receiver audio off until an RF signal appears at the receiver input
The glide slope signal above the glide slope is
90 Hz amplitude modulated
The gain of an antenna is
A measure of its directional properties
To erase the tape of a CVR the following conditions must apply
Aircraft on the ground parking brake set
A IRS system consists of
No gimbals
A buffer amp on a transmitter is between
Local oscillator and modulator
A better radar range resolution is provided by
Short pulse duration
The fundamental decca frequency is approx
14.2 kHz
An aircraft in the localiser centreline received a signal equally modulated by each tone to a depth of
30%
The raw output of a the auto VOR is
Magnetic bearing information
A minimum distance over which communication at a given frequency can be established by means of the sky wave is known as
Skip distance
The ins system is Schuler tuned to prevent errors due to
Oscillations if the platform due to aircraft accelerations
The external inputs to an ins are
TAS and altitude
The radiation pattern of a VOR station will transmit bearings that are
Magnetic
The characteristic impedance of a transmission line is
Independent of length
To meet the requirements of HIRF protection gold film windscreens need
No additional protection measures
HF wire aerials should not be made of stainless steel because it has
High RF resistance
An aircraft transmitter has an output impedance of 50 ohms the correct matching for this transmitter would be
Feeder 50 ohms
Aerial 50 ohms
The ideal standing wave ratio in an antenna is
1:1
After VOR capture on a ground check, aileron movement will depend upon
Course select error, radio deviation and bank angle
The outputs from a balanced modulator are
LSB AND USB
FM systems are less affected by noise than AM systems because noise modulates the carrier in
Amplitude
The facility performance ILS intersect height is where the
Localiser and glide slope signals cross
Crosswind compensation in an FD system may be achieved using
An integrator
After go around in an FD system the following mode may be selected
HDG
The bandwidth of an antenna
Can be increased by using a matching sub
An interrupted carrier wave is referred to as
A1
A DME system gives
Slant distance
Radio altitude is annunciated by voice
Below 500ft
ATC mode c uses
Gilliam Gray code
The three transmitted omega frequencies are
10.2 kHz, 11.33 kHz and 13.6 kHz
An aircraft is due south of a VOR beacon and has 000 degrees set in the omni- bearing selector if the aircraft is heading 090 the time from indicator will show
To
The INS battery is used to
Start the system and run it in an emergency
The usable range of the ILs beam is
About 15 miles greater than the glide slope
Side tone can be derived from the transmitter
Power amplifier
A single side and transmitter is transmitting in the upper sideband the carrier frequency is 10Mhz the modulating frequency is 10 kHz the transmission will consist of
A single frequency of 10.010Mhz
The ground run monitor present information of
distance to go and ground speed
An aircraft at 40,000ft using vhf can communicate upto a distance of
260NM
A VOR ground station is referenced to
Magnetic north
A dipole for operation T 300 MHz would have a length of
500cm
When the heading knob is rotated ok the FD system it moves the rotor of a
Control transformer synchro
A class 3 fault reporting failure
Has no consequences on aircraft safety
How many gps satellites required to locate the aircraft’s position in 3 dimensions
4
With a magnetic indication of 000 easterly deviation would
Be added to the heading as easterly deviation is positive
A cvr installed on a helicopter first certified after 1st august 1999 with two engines with a max certified MtOW 3175KG must begin recording
As early as possible during the cockpit checks prior to engine start
A CVR is found to be unserviceable
Flights must not continue after 72 hours
A defective radôme would cause
Excessive ground clutter
A DGPS system installed on a aircraft requires
One ground station and 4 satellites
A DME system indicates aircraft
Slant range to the beacon
A DME is in auto standby when
The DME receives 300-400 pulses a second
A DME receives a ground transponder reply after 2472 micro seconds the slant range to the transponder is approximately
196nm
A Doppler radar antenna is moved
Automatically to track
A Doppler a VOR stations transmissions
Can be received and processed with a conventional VOR receiver
A flat plate antenna is a
Series of slots and wave guides
A force rebalance accelerometer in an in system has the acceleration force balanced by a
Linear force
A GNS satellite system transmissions are
Right hand circular
A GPS system is formed from
Space control user
A hyperbolic system is
LORAN C
A laser dither mechanism ensures that
Optical back scatter does not cause the contra rotating beams to lock together
A laser gyro output is
Directionally proportional to angular turning rate
A LORAN C transmission consists of
8 pulses each 270 microseconds long
A magnetron can be used as an
Oscillator or an amplifier
A mode S transponder utilises a
Logarithmic amplifier
A mode C transponder
Can be used by TCAS
A mode C transponder gives the following information
Altitude
A mode S equipped aircraft has its RA area breached by a mode A only equipped aircraft what warning does the mode S aircraft get
TA visual and aural traffic traffic
A mode S transponder makes a mode A/C only call, what is the length of the P2 pulse
.8us
A moving coil microphone needs
No power supply
A padder capacitor has most efficiency at
The lowest frequency of the L O
A poor oscillator in a receiver would cause
Poo channel selectively
A pulse repetition frequency of 1000 transmits for 2 microseconds the peak power is 1 kW the average power is
2 watts
À quartz crystal has the characteristics of a
High Q resonant circuit
A rad alt trip signal is
Switched DC
A rad alt in track mode is effective to
2500ft
A radar antenna is facing left on ground test if you move the vertical gyro to simulate a right bank the antenna
Will move down
A radar response takes 329 microseconds how far away is the target
25 miles
A radar pulse takes 308 microseconds to return wheat is the target distance
Approx 25 miles
A radio frequency of 16 MHz would be used for
HF comms
A radio signals chance of penetration of the ionosphere
Increase with frequency
A rain fall of 5mm/he is indicated on the WXR by a
Yellow colour
A received acars message is
Via the on vhf receiver
A receiver having an IF of 465 kHz is tuned to 1300KHz which of the following signals could interact with the LO second harmonics to produce a receiver output if no RF amplifier was used
3995KHz
A receiver in which selected signals of any frequency are converted to a single frequency is called a
Superhet receiver
A receiver with a high IF will successfully reject
The 2nd channel / image frequency
A receiver with a large bandwidth will have
Poor signal to noise ratio
A resistance-capacitor low pass filter will have
The output taken across the capacitor
A Schuler pendulum has a period of oscillation of
84.4 minutes
A secondary radar system receives reply signals from
Another transmitter
A SSR interrogation operates on
A frequency of 1030MHz and pulse spacing depending on mode of interrogation
A Selcal signal transmits
Two pair of tones one pair after another
A signal at 120 MHz frequency will normally propagate by means of
Space waves
A single side and transmission is equal to
Low level modulation
A strap down INS has
A solid state accelerometer system
A TCAS blade antenna is
Part of the atc transponder system
A transponder that is compatible for use with a TCAS system would be
Mode S
A triple rad alt installation isolation is carried out by
Differentiating the frequencies
A valid interrogation will
Disable the RX, enable the encoder and disable the DME
A VHF comm blade aerial has a length of
A quatre wave length
A TCAS blade antenna is
An L-Band omnidirectionnel array
A whip antenna uses
1/4 wave
Above the glide slope the ILS glide slope signal modulation is
90Hz
ACARs is
A way of reporting defects to maintenance base in flight
ACARs is primarily used for communicating with
Maintenance base
ACARs is used to transmit
Both in flight and on the ground
ACARs sends information from base to the aircraft via
The printer
ACARs system operates in the frequency range of
131.550MHz
ACARs transmits it’s data using
Binary code
Accuracy if a GPS system used in aircraft navigation systems is
16 metres or less
Adding 6ft of cable to both TC and RX aerials on a rad alt would give you
18ft error
ADF is
Theta
(Angle only)
ADF operates within which frequencies
200 - 1000KHz
ADF operation range is at
MF band
ADF system sense aerial is
Null cardiod
ADF works by using
Both loop and sense aerial
Aerial masts maybe be damaged by
Skydrol hydraulic fluids
Aerials provide optimum output at one particular frequency when it’s load is purely
Resistive
After flying through the cone of confusion
Signal alters and the instrument indicates from
After passing the cone of confusion of a VOR
The phase difference reverses
Aircraft is 9000ft when is out of VHF range?
120NM
Aircraft north of VOR beacon on a course of 090 RMI the pointer points to?
180
Alert and decision height differ in that
The alert height is based on ILS equipment and decision height is based on the RVR
Alert height is
Where a decision of whether to land is made based on aircraft characteristics and it’s fail operational landing system
Align light flashes during alignment of an INS
It is attracting the operators attention
An o ring in a wave guide is used to
Stop moisture entering the wave guide
An accelerometer has
High inertia, restrained
An accelerometer in an ONS must be able to detect accelerations down to
10-6 g
An ADF system includes
Both a sense and loop antenna
An adjustment of the laser beam inside a laser gyro IRU
Can be done by adjusting the servo mirror
An aerial can be broadbanded by
Using a stub
An aircraft equipped with Mode A transponder only, enter airspace of a TCaS 2 aircraft. What indication does the pilot of the TCAS 2 aircraft get
TA after ranging
An aircraft flying on a heading of 030 receives an ADF signal 030 relative to the aircraft what is the ADF pointer indicating
060
An aircraft is on course on an IlS localiser what is the difference in depth of modulation (DDM)
Zero
An aircraft receives response from a DME station, 1236 microseconds after transmitting the interrogation. What is the slant range to the station
96 nm
R=(T-50)/12.359
An aircraft with 8.33kHz separation vhf communication system communicates using
Single channel simplex
An autoland can operate without an autothrottle if
The control of the speed does not create excessive pilot workload
An electromagnetic microphone requires which type of input
None
An FM signal would have its side and signals
No sideband present
An hf coupling is used to match the
Aerial
An I F amplifier unit consists of four amplifiers the amplifiers are normally coupled by
Transformer coupling
An ILS back bean approach uses
No glide slope
An IN system requires data from the
Air data computer
A IN unit uses pin programming for
Location
An IRS alignment
Takes 10 minutes and present position can be entered anytime during the alignment
An IRS cannot calculate
Local longitude
An isotropic radiator
Has a perfectly spherical radiation pattern
An over station sensor OSS detects
The rapid rate of the VOR signal over the cone of confusion
An OSS is triggered by
Rate of change of radio deviation
An RMI in VOR mode, it’s pointer is showing a course 000, if the course knob is adjusted to 010 what happens to the pointer
It will not move
Anti cross-talk network for unwanted signals use
Attenuation first the amplification
ARINC 629 operates at what speed
2000Kb/s
At its resonant frequency a parallel tuned circuit
Has maximum circulating currents
At its resonance frequency a parallel tuned circuit has
Maximum impedance
At resonance in a series tuned circuit the impedance is
Low
ATC altitude read out is
Series transmitted with binary encoding
ATC transponder uses what frequency band?
UHF
ATCRBS reply pulses are
0.45us wide
Attenuation in a coaxial cable
Increases with frequency increase
Attenuation of ground waves
Increases with frequency
Audio frequency range is
20-20,000Hz
Audio select panel voice switch
Allows Nav and ADF through
Back bean is captured
By manually selecting the back beam mode
In MLS the 12 but preamble consists of
5 bits time function and carrier and 7 bits function
Bandwidth of HF transmission is
3kHz
Before processing an AM USB signal, what needs to be done
Carrier added
Before the aeroplane is moved from the loading pier, the pilot must
Insert the latitude and longitude of the pier into the INS
Before the SSB is demodulated
The carrier wave is reinserted
Carbon microphones require
DC supply
Centripetal error compensation is achieved by
An additional signal is added to the N/S accelerometer to cancel the centripetal error
Channel 3 on a CVR records
Flight deck
Coaxial transmission line of impedance 80 ohms is connected to a dipole of 120 ohms. While checking with an ohmmeter the reading will be
More than 20 megaohms
Communication between the aircraft earth station and the satellite is on
L band
Confirmation of the correct operation of an ATC transponder ident function is verified by
Use of a ramp test set
CDU selection of TKE displays
Difference in degrés that the aircraft track is to the right or left of the desired track
Coriolis effect is corrected for by
Adding a correction term to the accelerometer outputs
Crystals operate reliably at fundamental frequencies up to
30MHz
CVR is unserviceable
The aircraft can fly for 72 hours since unserviceability
Data communication between the aircraft and the operational control centre is possible through
ACARs system
Decca navigation usés
LF
Delayed automatic gain control is inop, the sensitively of the receiver will
Increase for the high voltage signals
DFDR arinc 573 data bud has how many subframes
4
Differential GPS requires
4 satellites and 1 ground based transmitter
Direction property is exhibited by
The loop antenna
DME compares what for measurement of slant distance
Pulse transmission and return echo
