Navigation Flashcards
Meridian of Longitude
Semi-circle joining North pole to South pole, e.g. Prime Meridian, Anti Meridian
Parallel of Latitude
Line parallel to equator going around the globe, shorter as you move N/S from equator
Position in terms of longitude/latitude
Based on which of the lines you are on.
So your longitude is which line of longitude you are on, i.e. how far East/West of Greenwich.
Great circle vs small circle
Examples
A great circle is a circle around Earth with the centre of the Earth at it’s centre.
Any other circle on the planet surface is a small circle.
Equator is a great circle, all other parallels of latitude are small circles.
Relevance of great circles to navigation
The shortest distance between any two points is along a great circle which connects them.
Rhumb line
A curve that crosses all longitudes at the same angle.
May look straight on a chart, but is not the shortest route.
Lambert Projection
- Description
- Useage
Conical projection
Used for mid latitudes
Mercator Projection
- Description
- Useage
Cylindrical projection (vertical)
Used for large regular maps
Transverse Mercator Projection
- Description
- Useage
Cylindrical projection (horizontal)
Used for UK maps with fixed meridians
Apparent time
Based on position of the sun
e.g. Northerly shadow at midday
Mean time
An averaged out version of apparent time to account for changes in day length over the year
Convert time difference to longitude difference
360deg == 24 hours
15deg == 1 hour
1 deg == 4 mins
15’ == 1 min (say 15 mins == 1min)
UTC
- Stands for
- Description
Universal Time Coordinated
Coordinated global time using nuclear clocks rather than astronomy
Features of UTC
Has 24 hours/day, 60 mins/hour.
But 59-60 seconds per min to match solar time (62 seconds in last minute)
International date line
Located around 180deg E/W longitude. Not a straight line.
Different date on each side of the line
Which way does date change when crossing international date line?
West to East -> Lose a day
East to West -> Add a day
[Cumulative effect of it later in the day as you move East]
Definition of sunrise/sunset
When the upper limb of the sun is first/last visible
Definition of civil twilight
When the sun is 6 degrees below either horizon
Isogonal
Line along which compass variation is the same
Agonic line
Isogonal with variation of zero
3 different types of heading
True
Magnetic (adjusted for variation)
Compass (adjusted for variation and deviation)
How is compass dip offset?
Pivot point of compass is adjusted, differently depending on hemisphere.
Errors caused by compass pivot point
Accelerating @ 90/270 degrees will create error.
Turning through 180/360 degrees will create error.
ISA
- Full info
International Standard Atmosphere
1013.25 hPa
15degC @ AMSL
1225 g/m(3) air density
ISA temperature increment
Cap
2 degrees C every 1000ft, up to 36,000ft (-57 degrees C)
Effect on altimeter if temperature is lower than forecast by ISA
Cold air has lower energy, lower pressure, so altimeter thinks you are higher than you are.
Altimeter will over-read, so you fly lower than you think and risk ground strike.
Pressure altitude
Altitude shown with 1013hPa pressure setting
Density altitude
- Calculation
Pressure altitude adjusted for OAT difference to ISA based on 120ft per 1degC.
Calculate expected ISA temp based on pressure altitude (2degC per 1000ft).
Higher temp increases density altitude.
CRP-1
- True altitude from indicated altitude
i) Calculate pressure altitude by adjusting altimeter setting to 1013
ii) Set air temp against pressure altitude in CRP-1 window
iii) Read indicated altitude (not pressure altitude) in inner wheel against true altitude in outer
Semi-circular rule
360-179: Odd
180-359: Even
VFR: +5
Skip 420 for 430 then big gaps
Transition layer minimum size
500ft
CAS/RAS
- Stands for
- Definition
Calibrated/rectified air speed
Adjusted IAS to account for instrument error & position (of pitot) error
Utilise calibration table in pilots operating handbook
CRP-1
- TAS from CAS
Line up pressure altitude and OAT in Air Speed window.
Read off TAS in outer ring from CAS in inner ring.
CRP-1
- Drift calculation (wind-up method)
Blue dot will be the destination.
Mark wind by setting wind direction on wheel and placing blue dot on wind velocity in lower grid - cross at origin.
Now set cross to target of heading, by setting wheel to heading and lining cross up with TAS.
Read off velocity to blue dot and drift to figure out heading.
CRP-1
- Crosswind component calculation
Set wind direction on wheel and blue dot to origin of grid.
Mark off wind velocity with ‘x’.
Set wheel to runway direction and read off crosswind component.
CRP-1
- Speed/distance/time calculation
If given speed, set 60 minutes on inner circle against speed on outer circle. Then # minutes on inner circle lines up with relevant distance on outer circle.
Or set a given distance and time up on outer and inner circles and read off 60 minutes.
Components of fuel requirements (7)
i) Taxi fuel
ii) Trip fuel
iii) Contingency fuel
iv) Alternate fuel (furthest of 2 alts)
v) Final reserve fuel (45mins SEP, 20 mins heli.)
vi) Minimum additional (15 min holding)
vii) Extra fuel (PIC discretion)
Contingency fuel amount
Greater of 20 minutes or:
i) 5% of planned trip (or 5% of remaining if re-calculating in flight);
ii) 3% of planned trip if you have en-route alternate (not allowed for helicopters).
CRP-1
- Fuel per hour calculation
Similar to speed/distance/time but with fuel on outer circle instead of distance
CRP-1
- Conversions
Set km/M/ltr amount on circle to km/M/ltr marker, read off circle against relevant unit marker.
CRP-1
- Conversions with specific gravity
Set litres of fuel on outer circle to km/M/ltr marker. Use cursor to read off from specific gravity (kgs or lbs) to weight on inner circle.
Flight plan form
- Flight rules
- Type of flight
- Cruising speed
- Level
Flight rules: “V” for VFR
Type of flight: “G” for general aviation
Cruising speed: “N0105” for 105kts (nautical miles) (TAS)
Level: “A025” for altitude 2,500ft
2 principal means of visual cross country navigation
- Dead reckoning
- Map reading
Markings for dead reckoning
Start @ ground position, air position is nil wind plot, DR is position adjusted for drift
Methods for getting initial fix
i) Set a heading point c. 4nm from aerodrome in direction of journey
ii) Turn left and fly overhead runway >1,000ft (ATC may not allow)
iii) Estimated initial track
Position Line
A line identified on chart that you could be anywhere along, need another reference to calculate precise position
Action to take if lost
Set transponder to 0030 and contact D&D on 121.5
Assumed error on heading and distance to establish likely area of location
+/- 30 degrees on heading
+/- 10% distance
Overall process for track corrections
i) Establish track error (TE)
ii) Calculate closing angle (CA)
iii) Adjust heading by TE + CA
TMG
- Stands for
- Definition
Track Made Good
This is the ground path you have actually travelled over
1 in 60 rule
Over 60nm, every 1 degree off heading results in missing target by 1nm
Ratio rule
CA based on distance left relative to distance complete:
- Same distance: CA = TE
- Half the distance: CA = 2 x TE
- Twice the distance: CA = 0.5 x TE
Inverse Ratio Rule
To correct at 1/x way point alter heading by CA * x.
Utilising inverse ratio rule
Can draw 5 degree and 10 degree spread headings from the destination towards start point and mark quarters along the intended track.
Then can easily see CA and proportion of track completed.
Drawback to inverse ratio rule
Can only make one correction per leg of the journey, so only suitable for short distances.
Standard Closing Angle Method
Use a pre-prepared chart of 1 minute and 2 minute standard closing angles for different air speeds, that will close 1nm of distance
En-route diversion - 60 degree method
To get around an area (e.g. thunderstorm) en-route, turn 60 degrees then back on heading when you can get past.
Once past it turn 60 degrees again and fly for same time as previous leg.
Then time lost is equal to the time of each of the 60 degree legs.
Chart estimates
Thumb is 10nm on 1:500k, 5nm on 1:250k.
Hand-span is 60nm on 1:500k, 30nm on 1:250k.
ELT frequencies
121.5 and 243 MHz
Personal Locator Beacon frequencies
406 MHz and 121.5 (not monitored)
Radar range
Range in nm = sqrt(1.5 * height in feet)
[+ if appropriate sqrt(1.5 * height of radar station in feet)]
Primary radar drawbacks
Only operates on the beam it is directed at.
Subject to clutter (e.g. from rain, clouds).
Blind spots
Uneven returns from different aircraft.
Altitude type broadcast by Mode C transponder
Pressure altitude
Transponder Mode S Elementary
- Aircraft identity automatically presented to radar controller
- Altitude reporting to 25ft
- Aircraft on ground or in air
- 24 bit data resolution
Transponder Mode S Enhanced
- Altitude in Flight Management System
- Roll & track information
- Groundspeed
- Magnetic heading
- IAS and mach
- ACAS information
ADS-B
- Stands for
- Description
Automatic Dependent Surveillance - Broadcast
Data sent out from GPS unit automatically derived from onboard GPS receivers.
Transponder code 7010
Aerodrome traffic pattern - only select if instructed by ATC
Transponder code 2000
IFR equivalent of code 7000
How many satellites required for 3d or 2d gps fix?
3d: 4 satellites
2d: 3 satellites
2 types of GPS augmentation
- Receiver (RAIM) or Aircraft (ABAS) systems use redundant satellite to correct errors
- Satellite systems (SBAS) provide correction info via satellites themselves
Nature of GPS signals
Line of sight to satellite, so can be shielded by terrain at low levels.
Handheld units in aircraft can be masked by the aircraft structure.
Information on satellite interference
Via NOTAMs
VOR
VHF Omni-directional range
Advantages & disadvantages of VOR
- Not susceptible to interference
- Not susceptible to night effect
- But LOS needed so can be blocked by terrain
VOR range
Range = sqrt(1.5 * height in feet)
How does VOR work?
Transmits two waves:
i) Omnidirectional reference wave
ii) Variable phase rotating uniformly with phase varying over 360 degrees
Receiver compares phase of two waves to determine heading
What direction figure is given by VOR?
QDR - Magnetic bearing from the station to the receiver
What is VOR radial?
A line on which QRM from VOR is constant (125 radial is line drawn at a heading of 125 from the VOR)
General use of VOR indicator
Set course index based on course you want to fly to or from the VOR.
Set heading roughly in right direction and from/to flag should be as you expect.
Dots either side of the centre line show deviation of position (2 degrees per dot) from the set course.
To correct, if indicator is to the right, need to turn to the right (track more right than the set course).
VOR VHF frequencies
108-117.95 MHz
DME
- Stands for
- Frequency type
Distance Measuring Equipment
UHF (962 to 1,213 MHz)
VOR/DME on chart
VOR shown as a compass rose.
DME written if there is also a DME there.
How does DME work?
Uses secondary radar.
Signal from aircraft is bounced back from the DME unit and the time delay used to calculate distance.
What does DME display?
Distance (slant range) but also sometimes closing speed and time to intercept.
DME limitations
100 aircraft per DME unit
NDB
Non-directional beacon
ADF
Automatic direction finder
How does NDB/ADF work?
NDB broadcasts in all directions, ADF detects which direction it is coming from
NDB frequency type
LF/MF range
280 - 535 kHz
NDB disadvantages
Thunderstorms redirect signal
Night effect
Interference from other NDBs
Coastal effect (beams curve around coast)
Turning error: takes time to adjust when turning
ADF aerial system
A loop aerial and sense aerial together figure out direction of signal
ADF setting - ANT/REC
Switches off the sense aerial to maximise audio signal but lose direction ability.
Don’t select when in use or in conjunction with BFO/CW4
ADF setting - BFO/CW
Beat frequency oscillator/carrier wave - special setting to demodulate signal from A0/A1 NDBs for identification (turn off after identified)
ADF setting - Test
Momentarily deflects ADF needle, it will return to previous position if working.
[Alternatively ANT/REC may push direction to 90 degrees if no test button]
Using ADF to steer “to”
Track required is that shown by ADF.
Adjust heading to account for wind then ADF display should remain constant.
If far away correct to regain correct track, if closer consider adjusting to new track.
Using ADF to steer “from”
Need to establish a suitable track away initially and then correct to keep ADF in the right direction
3 types of ADF display
RBI (Relative Bearing Indicator): 360 in line with aircraft, displays relative bearing to NDB
RMI (Relative Magnetic Indicator): Rotating magnetic card, indicator shows magnetic bearing to NDB
Rotatable card ADF: Card can be turned so choose either of the 2 approaches.
VHF direction finding report types
QDM - Magnetic direction to station
QDR - Magnetic direction from station
QTE - True bearing from station
Class of VHF direction finding results
Class A: +/- 2 degrees
Class B: +/- 5 degrees
Class C: +/- 10 degrees
Class D: Worse than class C
VHF direction finding disadvantages
Not subject to night effect, thunderstorms, coastal effect.
Is affected by site and propagation errors
Tilt of earth’s axis from plane of orbit around the sun
66.5 degrees
On 1:250,000 chart, what is maximum altitude of information on chart
FL55 or 5,000ft
