Exam revision Flashcards
What is a sine wave?
Electromagnetic wave shape
What is a wave length?
Length of a single wave
What is the frequency of the radio?
Number of cycles passing a given point in a second
What is amplitude?
Displacement of wave peaks of troughs from the middle value
What is amplitude used for?
Measure the strength of signal
greater the amplitude, the greater the strength
What are sidebands?
Additional frequencies which occur whenever a carrier is modulated by frequency lower than itself. In modulation, the sidebands carry the intelligence
What is a ground wave?
Part of energy from non directional antenna radio frequency that travels along earth surface
What path does ground wave follow?
Roughly parallel to earth surface
What can ground waves be broken into?
Direct (follow line from transmitter to receiver)
Surface (follow contour and curvature of earth)
Sky (refracted and reflected by ionosphere
How is the range of surface waves determined?
Rate at which signal is absorbed and weakened by surface over which it is travelling (aka attenuation)
What is the THEORETIC RANGE of VHF Signals?
Square root of (1.5 x receiver altitude in feet)
Is water a good transmission surface for ground waves?
Yes
Why do night time rated coverage of NDBs drop?
Increased sky wave interference with higher ionosphere
What is skip distance?
Distance from transmitter to point where signal returns to earth after reflecting off ionosphere
What does build up of static electricity do to radio signal?
Affects negatively
What frequency does VOR operate in?
112.00 to 118.00 VHF band
What does a VOR station produce?
30Hz reference and 30 Hz variable phase
How does VOR work with aircraft?
- VOR produces radial pattern signals
- Nav receiver compares phase of signals to figure what radial its on
- Compares computer radial to radial pilot selects with OBS and deflects CDI to indicate variation between desired and actual
How is the phase orientated with VOR?
Magnetic north
What are the errors for VOR? What are the degree of difference?
Airborne equipment error (+/- 2 degrees)
Vertical polarisation error (when VOR antenna is banked out of horizon plane)
Ground station error (transmission equipment (+/- 2 degrees)
Aggregate error (total of all errors (+/- 5 degrees)
Site/terrain error (bending or scalloping of signals due to obstacles close to site (+/- 2 degrees)
What is a doppler VOR?
Transmits FM instead of AM to almost eliminate site error effects
What does NDB do?
Transmits non directional carrier signal with audio id for morse code
What range is NDB?
MF
What instrument is in the aircraft for NDB and how does it work?
ADF
Combines signal received from two antenna and gives relative bearing to/from station OR may be overlayed on RMI to give magnetic track to/from
What errors are in NDB?
M - Mountain effect (reflects signal from mountain)
I - Interferrence (from other NDB esp at night)
N - Night effect (skywave interference)
T - Terrain effect (sand/rocky country attenuating signal)
C - Coastal refraction (signals bend towards land as cross coast)
H - Height (reduced range at low altitude )
A - Aircraft ( quadrant error, bending due to aircraft)
T - Thunderstorms (thunder storms attract ADF needle)
What frequency is DME?
UHF
What does DME do?
Provide readout of actual distance (slant range) from ground station
What will aircraft read directly overhead DME?
Height above beacon in NM
What does Mode A SSR send?
ID Code
What does Mode C send?
Altitude info
What is Mode S for?
TCAS
What are the components for ILS
Localiser (LLZ)
Glideslope (GS)
Marker Beacons
What does One dot on the cockpit represent for ILS?
Half a degree of course deviation
What does the blue marker light mean for ILS?
Outer marker
What does Amber light mean for ILS?
Middle marker
VOR operates under the principle of what?
Phase differential
VOR radials are calibrated for magnetic variation that exists where?
At the station
What does aircraft bonding do?
Ensure even electrical potential between different parts on plane
What is an advantage of the Secondary Radar over primary radar with regards to return signal?
Eliminates unwanted return signals (clutter)
What does the ADF loop antena do?
Identifies null position
In ILS, full deflection of glide path needle is?
0.7 degrees above or below
As an aircraft approaches DME over head, what happens to DME readout?
DME readout reduces at decreasing rate to read altitude in nm overhead then increase at increasing rate after passage
For the most accurate readout, where are pitot and static systems mounted?
Area of minimum air stream disturbance
Parallel to longitudinal axis of aircraft
What will a blocked pitot cause?
Blocked pitot causes under read on descent
What will a blocked static cause?
Underread on climb
What will a leak in the pitot cause?
ASI to underead
What will a leak in the static cause?
ASI to overread when outside pressure is lower than static
ASI to underread when outside air is higher than static
When are turning errors going to occur?
Maximum turning through north and south. Minimum east and west.
(Overshoot north, undershoot south)
When are acceleration errors going to occur?
Max on east and west headings, minimum on north and south (south accelerate, north decelerate)
Compass errors are minimum where?
At magnetic equator
What effect does latitude have on compass errors
As latitude increases, error increases
What are the advantages of gyrostablised remote indicating compass over direct reading magnetic compass?
Reduced turning and acceleration errors
Reduced deviation and slaveable outputs
Where is Flux Valve for RMI located?
Wingtip or tail
With RMI, constant oscillation of annunciator indicates?
System operating normally and gyro is hunting for mean position
When using a weather radar, the most turbulent areas are?
Closest contours near the avoid zone
What happens to horizontal axis gyro at the pole?
No topple, maximum drift
What happens to horizontal axis gyro at the equator?
No drift, no topple (axis north to south)
No drift, max topple (axis east to west)
What happens to vertical axis gyro at the pole?
No drift, no topple
What happens to vertical axis gyro at the equator?
No drift, max topple
How many satellites are needed for 2D nav?
3
How many satellites are needed for 3d nav?
4
What is RAIM required by?
TSO C129
How many satellites are needed for RAIM to operate without satellite failure?
5
How many satellites are needed for RAIM to continue to follow the detection and deselection of faulty satellite?
6
In the vertical axis, what happens to the gyroscope at the south pole?
Drift and topple will be zero due to earth rate rotation
In the horizontal axis, what happens to the gyroscope at the south pole?
Drift will be maximum
Topple will be zero
For accurate altitude measures, how many channels does a GPS receiver need?
4
What is the minimum number of satellites to eliminate GPS receiver clock error?
4
The most significant GPS error is caused by what?
Ionosphere
What is the minimum number of satellites needed for accurate 3D GPS fix?
4
What does the pseudo random code allow for?
Each satellite to transmit on the same frequency
What is GDOP or PDOP caused by?
Small distance between satellites
What is a rhumb line?
Curved line on earth surface which cuts meridians at same angle.
Shortest distance between two points unless at the equator.
What will an aircraft following a rhumb line be doing?
On a constant track
When are rhumb lines also great circles?
Meridian and equator
What are great circles?
Circle on the surface of a sphere whose centre and radius are those of the earth itself
Track between two points is the shortest distance between two
What is the convergence factor formula (n)?
Bearing change divided by longitudinal change
On a polar stereographic chart what do meridians appear as?
Straight lines
On Lamberts conformal conical projection, a great circle track away from a parallel of origin appears as what?
Concave to parallel of origin
On Mercators projection, what is a straight line?
Rhumb line
On a Polar Stereographic projection, rhumb lines are what?
Curved concave to the pole
On a Polar Stereographic projection, great circles are what?
Represented by straight lines at pole, becoming concave to the pole at low altitude
In the northern hemisphere, the great circle bearing decreases when flying what direction?
West
On a Lambert’s conformal conic projection, what is the formula for rhumb line track?
Average of great circle track at either end
What is the formula for CP?
Total distance x GS home from CP / GS Home from CP + GS ON from CP
An NDB is what directional beam?
Omni directional
At the south pole, what happens to vertical axis gyroscope?
No drift or topple
At the south pole, what happens to horizontal axis gyroscope?
No topple, max drift
In INS, compensation for Earth rotation must be applied according to what?
Specific latitude
In INS, compensation for transport rate must be applied according to what?
Aircraft speed over ground
In INS, the platform of accelerometers are mounted must be aligned with what?
True north
A machmeter is subject to what errors?
Pressure and instrument
What is the formula for time to PNR?
Safe endurance x GS(H) / GS(H) + GS(O)
What is the formula for distance to PNS?
Time to PNR * GS(O) / 60
What is the formula for CP?
(Distance / TAS) x Wind speed
What error does Machmeter suffer from?
Instrument and Pressure
What does the temperature of air do to ASI
Cold air over read
What does QNH below 1013) do to transition layer?
Thiner layer
What does QNH above 1013 do to transition layer?
Thicker layer
What does bending or scalloping occur in?
VOR
What does the ADF loop antena identfy?
Null position
What do HF radio waves propagate by/
Single and multi hop sky waves
What is attenuation?
Weakening of radar transmissions and returns
