Nav 01 Flashcards
What is UTC?
Universal Time Coordinated.
The longitudinal datum that assumes that the sun passes over at 1200 with a 24 hour clock.
What shape is the earth?
An oblate spheroid
Define a great circle.
A circle drawn on the surface of the earth whose radius and centre are the same as the earths. If used as a route will be the shortest route from a to b.
Define a small circle.
A circle drawn on the surface of the earth whose radius and centre are not the same as the earths.
What is the definition of the equator?
A great circle whose plane is perpendicular to the earths axis of rotation and which divides the earth into two equal hemispheres.
What is a meridian?
A semi great circle joining the poles.
What is a rhumb line?
A regularly curved line on the surface of the earth that cuts all meridians at the same angle. Appears curved on a Spherical representation of the earth (lamberts conic and globes) and straight on a flat one (mercator projection).
What is a nautical mile?
The length of arc of a great circle that sub tends an angle of one minute at the centre of the earth. 60nm in one degree as these are made out of minutes. 1nm= 1min.
40°x60 would equal 2400nm
40°and 20 minutes x60 would equal 2420nm
How far is a NM in KM?
=1.852km (happens to be the length of the runway condition that decides how wide the ATZ is)
What is the definition of night?
SERA
The period between the end of evening civil twilight and beginning of morning civil twilight. Civil twilight ends in the evening when the centre of the sun’s disc is 6 degrees below the horizon and begins in the morning when the centre of the sun’s disc is 6 degrees below the horizon.
What is are the datum reference points for lines of longitude and latitude?
The UTC prime meridian is the datum for longitude to 180west and east The equator is the datum for latitude up to 90 degrees either side at the poles
What are the figures for latitude and longitude?
Longitude is a seven digit number xxx degrees (60 mins) xx minutes (60 secs) xx seconds. E.g. 002 02 22. Latitude is a six digit number xx degrees (60 mins) xx minutes (60 secs) xx seconds. E.g. 51 02 22.
What are the cardinal and quadrantal points?
Cardinal = north, east, south and west
Quadrantal Points= NW, SE, SW, NE
Define grid north.
Grid north the direction of a grid line which is parallel to the central meridian.
Magnetic north
The direction indicated by a magnetic compass.
Define true north.
The direction of a meridian longitude which converges on the North Pole.
What is variation?
The angular difference between true north and magnetic north as measured by a magnetic compass at a particular location of the earth.
What is deviation?
The error induced in a compass by local magnetic fields.
How to convert from the different types of north.
West is best (+), east is least (-). True +/- variation = magnetic, +/- deviation = compass
I think of it as the north moving clockwise or anti-clockwise with the actual direction staying where it is.
TvMdC
With regards to charts what does conformal mean?
The preservation of angles required for navigation. ie How accurately is portrays the thing it is representing.
So conformal means;
- All angles and bearings on the earth are accurately represented
- Scale distortion at any point must be the same in all directions
- Each parallel must cross every meridian at right angles
What is a Mercator projection?
A cylindrical projection around the earth (can touch at the equator or any other point, transverse Mercator is one done horizontally). Most accurate at the point where it actually touches the earth, as you head away from this point the information becomes stretched and distorted.
On a Mercator; Rhumb lines are straight, Great circle routes are curved
They are conformal
What is a lambert conformal conic?
Refers to any projection in which meridians are mapped to equally spaced lines radiating out from the apex. Lines of latitude appear as arcs. Only accurate at the parallel of origin (point where it touches). This is the cone shaped one.
On a lambert conformal conic;
Rhumb lines appear as curved lines
Great circle routes are straight lines as the meridians are radiating out.
Is conformal, is nearly constant.
How is relief portrayed on a map?
Using contour lines and elevations (marking highest points), also achieved by hill shading (using colours to denote elevations).
Contour lines= Lines joining areas of equal elevation
What is the heading of an aircrafts?
The direction, relative to north in which the aircraft is facing.
What is a KM?
Kilometer
1/10,000th of the average distance between the equator and either pole.
How far is a NM in ft?
6,080ft
How far is a statue mile in ft?
5,280ft
How far is 1 KM in ft?
3,280ft
What is the conversion factor from ft to m?
x0.3048
What is the conversion factor from m to ft?
x 3.2808
What is the conversion factor from NM to KM?
x 1.852
What is the conversion factor from KM to NM?
x 0.5396
What is the conversion factor from NM to statute miles?
x 1.15
What is mean solar time?
Time based on the motion of an imaginary sun travelling at an even rate throughout the year. This will pass over every 24hours but will not pass over at exactly the same point each day as even the imaginary one still varies day to day (the variation is just averaged out).
What degree of longitude does each timezone cover on average?
15°
so each 15° of longitude would be worth an hours time.
What is the international date line?
The line which dissects two different days, it is in the Pacific and west of the line is 1 day later, east is 1 day earlier.
Travelling east becomes yesterday, west tomorrow.
What is an Isogonal?
A line on a map or chart that joins points of equal magnetic variation. (like an isobar does with pressure)
What is a marginal diagram?
Shows true north and magnetic north and the angle between them.
What methods are there of detailing magnetic variation on a chart or map?
Isogonals
Compass roses
Marginal Diagram.
What is inclination?
The magnetic dip or inclination of the compass needle caused by the earths magnetic field not running parallel to the surface.
What is a graticule?
A section of the earths surface used to indicate position, these cover the globe. Outlined by lines of parallels and meridians
What is latitude?
the angular distance from the equator to a point measured northwards or southwards along the meridian through that point.
Expressed as degrees north or south of the equator up to a max of 90°
Up to six digits
eg. 32° 48’ 12” N= 324812N
What is longitude?
The shorter angular distance along the equator between the prime meridian and the meridian through that point.
Expressed as degrees east or west of UTC up to 180°
Up to seven numbers
eg. 139° 12’ 31” W= 1391231W
How are Lat and Long expressed in aviation?
Seconds are displayed as a decimal of the minutes
- Lat= 6 figures
eg. 19° 27’ 45” S= S1927.75 - Long= 7 figures
eg. 029° 52’ 27” E= E02952.45
What other methods of establishing positions are there?
- Using the names of established waypoints, eg. EBOTO or ADNAM
- Use of approved abbreviations of beacons, eg CPT for compton or SAM for southampton.
What do the letters in an aerodromes ICAO designator mean?
EGLL
- The continent eg. E= Europe
- The country eg. G= UK
- Area in that country/ major aerodrome. eg LL= Heathrow
What are the Ordinance Survey Map references?
4 figures= accurate up to 1000m
6 figures= accurate up to 100m
8 figures= accurate up to 10m
10 figures= accurate up to 1m
What are the OS maps used for?
- Civil and military SAR over land
- Airfield Crash maps (these will be made available to police, ambulance and fire).
What does an airfield crash map allow a controller to do?
Give a precise location of an incident at the aerodrome.
How do pilots get their position?
Either by-
- Pinpoint- visual identification of the ground directly below
- Fix- use of bearings and position lines.
What is the true bearing of an object?
The horizontal direction measured in degrees clockwise from the direction of North at the pilots position of an object.
What is an ADF?
Automatic Direction Finder
This indicates the relative bearing of an NDB from the nose of an aircraft.
What is the relative bearing of an object?
The direction given clockwise in degrees from the aircrafts nose, combined with true heading this will give the true bearing of the object.
What is a position line?
A line drawn on a chart along which an aircraft is known to have been at a certain time. Two types;
- Single position line- to or from the object eg a radial from a VOR
- Circular Position line- In a circle around the object giving you range, eg a DME.
How can you gain single position information?
Bearing information via a
- VDF
- VOR
- ADF
How can you gain Circular Position Line?
Range info via
DME
What is a fix?
The intersection of two or more position lines obtained simultaneously. This will also give the ground position.
What is WGS84?
World Geoditic Survey
- Relates a position above the centre of the earth, rather than in relation to the surface, becomes very accurate when the two are combined though.
- Its what GPS uses
- Geocentric
- Globally consistent to within 1m
What do we use for plotting positions?
Charts
What do we use for reference and for topographical data?
Maps
What is the scale of a chart?
The ratio between the chart distance and the earth distance that is represents.
scale= Chart distance/earth distance
The larger the scale denominator the greater the distance shown so the lower the detail eg 1/500,000
The smaller the scale denominator the smaller the distance shown and the greater the detail. eg 1/1
What is an azimuthal stereographic projection?
Azimuthal (projections onto a plane)
- Used to produce topographical charts for specialist areas like the poles
- It is a conformal projection.
What is a transverse mercator projection?
The same as a normal mercator except that the cyclinder is arranged horizontally across the world
Is usually used for countries that have great extent north to south in comparison to west to east, like the UK.
What are the conformal projection types?
- Mercator
- Lamberts conformal conic
- azimuthal stereographic.
What is a contour?
Are continuous lines drawn on maps of equal elevation.
Spaces between the contour lines depends on;
- The scale of the map
- The range of elevations displayed on the map
- The units of measurement being used
The gradient is assessed by the proximity of the contour lines- the closer they are to each other, the steeper the slope.
What is a spot elevation?
The dot position indicator with the elevation alongside it of the highest point.
What are form lines?
Contour lines are replaced with form lines if an accurate survey of the terrain has not been carried out. They are shown as broken lines and indicate approximate elevations.
What is tinting?
The visual indication of vertical relief produced by contour lines may be enhanced by tinting the intervening layers.
What Hachures?
Short lines that radiate away from high ground.
What is Hill shading?
The simulation of a low sun angle casting shadows of high ground.
What scale is used for topographical charts?
1:250,000 as they want greater detail so a smaller scale is required.
What is RAS?
Rectified Airspeed
IAS corrected for pressure and instrument errors
What is MACH speed?
The speed of an a/c in relation to the local speed of sound.
Expressed as a decimalised percentage of that speed, eg MACH0.84= 84% the local speed of sound.
Subsonic= Less than speed of sound
Transonic= when one part of the a/c is travelling supersonic but not the whole airframe
Supersonic= more than speed of sound. Not permitted over land unless emergency.
What is the critical MACH number of an a/c?
The MACH speed at which point the shockwaves caused by supersonic flight attach themselves to the airframe causing a loss of lift generation and control.
What type of north is used to express wind direction in ATC?
Magnetic
What is a VRP?
Visual Reference Point
In the UK, these are used as guidance for pilots flying visually. Aircraft can hold above these, unless outside of CAS, in which case they should not be instructed to do so due to the use of the points for visual turning points. (MATS 1 details)
What is a Pitot tube?
A rigid tube that projects from an aircraft so that it can sample undisturbed air. The pressure of this air is Pitot Pressure.
What is Static Pressure?
The natural pressure exhibited by the atmosphere.
What is the dynamic pressure?
The pressure generated by the aircrafts movement. This pressure is displayed on the ASI as the Indicated airspeed.
How do you find the dynamic pressure of an aircraft?
Pitot pressure-static pressure= Dynamic Pressure.
How does an ASI work?
Airspeed indicator.
It takes a reading of the dynamic pressure from the Pitot tube and this is then converted into knots which are displayed on the ASI.
What errors are inherent in a Pitot Tube?
- Instrument error- Maufacturing imperfections and poor calibration
- Pressure Error- Can be caused by poor positioning of Pitot tube (position error) or manoeuvres meaning that the pitot tube is no longer pointing into the air flow (manoeuvre error)
- Density error- error caused by change in air density as you go higher as ASI’s are calibrated to ISA.
- Compressibility error- Air is compressed and halted upon entry into the Pitot tube above 300kts causing a false reading.
What is IAS?
Indicated airspeed
The speed read directly from the ASI
Is used for ATC speed control.
What is TAS?
True Airspeed
The RAS after being corrected for Density error
What does transonic mean?
When some (but not all) of the aircraft is travelling above Mach 1
M0.8-M1.2
What does Subsonic mean?
When mach no. is less than 1
less than M0.8
What does Supersonic mean?
When the whole airframe is above Mach 1
M1.2-M5
Above what speed is an aircraft considered Hypersonic?
M5.0
Where would the pilot be able to read his Mach no.?
From the Mach meter
Where must all Supersonic flights be made in the EU?
Over the sea, for those heading out they must be at least 10nm out and tracking at least 20° from the coastline
When pointing towards land must be at least 35nm away from the coast.
What will happen to an Aircraft’s Ground speed as it climbs?
It will increase due to decreasing density of air with aircraft peforming same TAS.
What is Groundspeed?
The speed of the aircraft over the ground, TAS corrected for wind velocity.
From what reference point can wind direction be given?
Normally True but on an anemometer it will be magnetic.
What is wind velocity?
Speed combined with direction.
On a vector triangle how many arrows does the heading and TAS have?
1
On a vector triangle how many arrows are there on the line for Track and groundspeed?
2
On a vector triangle how many arrows represent wind velocity?
3
What is the Drift Angle?
The angle between heading and track when there is wind, expressed as degrees either port or starboard.
What is track made good?
The track that the aircraft actually traces over the ground.
What is a required track?
The track that the aircraft has planned to follow, needs to account for the wind velocity.
What is the angle between the required track and the Track made good known as?
Track Error
What crosswind component is experienced at 0-15° off the runway heading?
Zero
What crosswind component is experienced at 15-30° off the runway heading?
1/4 of wind strength
What crosswind component is experienced at 30-45° off the runway heading?
1/2 of wind strength
What crosswind component is experienced at 45-60° off the runway heading?
3/4 of wind strength
What crosswind component is experienced at more than 60° off the runway heading?
Full wind strength
What is the 1 in sixty rule?
An angle of 1° will subtend to a distance of 1nm over a range of 60nm. Eg if you were 5° off track over 120nm you would be 10nm away from where you expected to be.
Reliable up to 20°
Who is responsible for the safety of an aircraft?
The pilot.
What else must a pilot consider when planning route and altitude?
- Safety
- Legality
- Feaseability
- Costs
What is an approach terrain chart?
The one that is used only for planning.
When is a compass most effective?
Midpoint between the equator and the magnetic poles.
What is the speed of sound at sea level?
660kts
When can day and night be of equal duration?
When the observer is standing at the equator with the sun directly overhead
What is the angle of tilt of the earths axis that causes the seasons?
23.5°
What does 1 degree of longitude equal at 60° latitude?
30nm
