General Navigation Flashcards

Question

Isogonal

Answer 1

A line on surface of the Earth joining points of equal magnetic variation

Answer 2

180 degrees when in between the true and magnetic poles (either North or South)

Answer 3

Line of zero variation 2 of them, together with lines of maximum (180deg) variation between true and magnetic poles, create a full circle around the Earth.

Answer 4

Secular: Long term movement of magnetic poles Annual: Sinusoidal, due to orbit of Earth around the sun Diurnal: Sinusoidal, due to ionosphere height, up to 0.1deg change over day.

Answer 5

Solar activity: Due to 11 year cycles of solar activity. Solar flares are predictable but impact on Earth is not. Has impacted variation by up to 7 degrees. Local anomalies: Due to rock deposits and local magnetic phenomena. Small enough effect to ignore.

Answer 6

The horizontal component of magnetic force which is useful in determining direction of magnetic north.

Answer 7

The angle between horizontal and the magnetic force experienced by compass

Answer 8

Lines on a map joining locations of equal magnetic dip

Answer 9

Isoclinals joining places with zero dip (the point on earth where compass is most accurate, as directive force is strongest and dip is weakest).

Answer 10

The angle between direction indicated by compass needle and the direction of magnetic north (direction defined as from magnetic north to compass north). Direction can be defined W or E, or alternatively - or +.

Answer 11

AKA B-type or E-type 1 of the 2 types of direct reading compass Circular compass card attached directly to magnet assembly, suspended in liquid. This is the typical light aircraft compass.

Answer 12

AKA P-type 1 of the 2 types of direct reading compass. Accurate, but bulky and expensive, has damping wires which give greater periodicity. Can only be measured in S&L flight when grid ring is unclamped.

Answer 13

- Horizontal - Sensitive - Aperiodic

Answer 14

Achieved by being "pendulously suspended", i.e. hung from a higher point so that the weight of the magnet offsets the effect of dip, reducing tilt to about 2 degrees.

Answer 15

Length of magnets is restricted so use 2, 4 or 6 short magnets, or circular magnet made of an alloy with high magnetism. Also reduce friction by using iridium-tipped pivot in jewelled cup, lubricating the pivot with the compass bowl liquid and reducing the magnets effective weight due to the liquid.

Answer 16

Compass needs to be "dead beat". Means that it settles down quickly after disturbance due to turbulence or manoeuvres.

Answer 17

Several short magnets instead of one long one keeps mass central and reduces moment of inertia on turns. Compass liquids primary purpose is as a damping liquid. Grid ring compasses have damping wires.

Answer 18

CS-OPS1: +/- 10deg

Answer 19

1 - Observe deviations 2 - Correct/remove deviation as far as possible 3 - Measure residual deviation

Answer 20

Magnetic force at the compass position due to the aircraft, regardless of heading and not induced by external magnetic fields.

Answer 21

The magnetic force doesn't change with latitude, however the resulting deviation does as the horizontal component of the Earth's magnetic field reduces at higher latitudes. Thus the deviation effect of hard iron magnetism increases at higher altitudes.

Answer 22

Magnetic force induced in the aircraft due to surrounding fields. We focus on vertical soft iron (VSI) magnetism, induced by vertical component of Earths magnetic field. [Note: Zero @ magnetic equator as no vertical component]

Answer 23

At increasing latitudes VSI increases due to effective increase in Z (vertical component) vs H (horizontal component) of earths magnetic force. Thus max deviation = Z / H = tan(dip angle).

Answer 24

This effectively creates a dummy magnet somewhere on the aircraft, which creates a sine wave impact on deviation as heading varies and its position moves relative to the compass and magnetic north.

Answer 25

Coefficient A: Mechanical error due to lubber line positioning, corrected by adjusting compass body position. Coefficient B & C: Corrections due to magnetic deviation forces acting on the compass. B measured on East/West heading, C on North/South heading.

Answer 26

Difference between Total Air Temperature (i.e. measured) and Static Air Temperature (SAT) (i.e. real OAT) due to impact of compressibility, kinetic & adiabatic issues with measured OAT. Roughly (TAS/100)^2 [TAS in kt], but use the blue part of CRP-5.

Answer 27

True OAT (COAT) is less than indicated OAT Use blue scale on CRP-5 to find the difference

Answer 28

AKA Rectified Air Speed (RAS) IAS corrected for: - Pressure (Position) error - Instrument error

Answer 29

CAS corrected for compressibility error. Deals with the fact that air density isn't 1.225kg/m3. Only relevant for TAS over 300kt, if below this figure don't carry out a correction in test.

Answer 30

Set up for CAS conversion to TAS using airspeed window (altitude and temp). If TAS > 300kt, use COMP. CORR. window, calculate TAS/100 - 3 (as indicated) and turn the correct number of divisions in COMP. CORR. Now read off CAS against TAS again.

Answer 31

Line up mach number indicator in air speed window with temperature. Now read mach number off inner ring against TAS in outer ring. NOTE - DOES NOT DEPEND ON ALTITUDE/FLIGHT LEVEL! CALC - TAS = MN x 38.95 x sqrt(K)

Answer 32

Line up temperature and pressure altitude in the ALTITUDE window. Read off indicated altitude in inner window against true altitude in outer window. NOTE: Indicated altitude = QNH, pressure altitude = 1012, use both here.

Answer 33

Can use CRP-5 but not accurate - Line up pressure alt and temp in the AIRSPEED window, read off the density altitude window. Use Density Altitude = Pressure Altitude + (ISA Deviation x 120)

Answer 34

Take 3 estimates of drift @ 60 degrees to each other. Centre the dot on TAS and select each heading, drawing a line along the relevant drift angle (e.g. draw over the 5 port line). The 3 lines should cross together at a point you can measure using the wind section.

Answer 35

This can be done reasonably accurately if estimating drift using VOR tracking (figure out the heading required to maintain VOR radial gives you drift). Don't get a third cut to confirm drift, but shouldn't need it due to better drift estimates.

Answer 36

Plot first wind on grid section, with dot at zero. For next wind, set direction, line the first "x" up with the top line of the grid and count down the grid by appropriate speed. Keep going with all winds. NOTE: Final speed needs to be divided by number of wind vectors (an average speed, not a distance)

Answer 37

Height = Glidepath angle x Distance to go (ft) / 60 [NOTE: If question refers to runway threshold, add 50ft to height]

Answer 38

For a 3 degree glide scope: ROD (feet per minute) = 5 x Ground Speed (kts) Other glide slopes adjusted linearly [Change in speed calculations also just 5 x change in ground speed]

Answer 39

Percentage glidescope x 0.6 = Degrees glidescope

Answer 40

This is the bearing relative to your current heading, e.g. 270 is directly to your left, regardless of which direction you are headed. Look out for this in triangulation problems.

Answer 41

Calculate TAS from mach using CRP-5. Calculate Ground speed using information given. Difference gives you head/tailwind component. Calculate desired new TAS. New True Mach No = Original TMN * (New TAS / Old TAS)

Answer 42

ECTM (if one is constant, the ones to the left are decreasing with alt, to the right are increasing). Except T&M together in isothermal layer, reversed in inversion.

Answer 43

Angle of inclination between two selected meridians, measured at a given latitude. At the equator it is zero as meridians all parallel at equator, at the poles it will be equal to the difference in longitude (imagine looking down on the pole, meridians initially head off at exactly their own longitude).

Answer 44

Convergency = Change in longitude x Sine (Latitude)

Answer 45

Change in heading will be equal to the convergence angle between the two points. As latitude is different between the two points use mid-latitude (this is a simplification, mean latitude is actually different). Change in heading = change in longitude x Sine (mid-latitude)

Answer 46

This is the difference between rhumb line track and great circle track between two points. Rhumb line track never changes and we know the change in great circle track between two points (convergency). Conversion angle is therefore half of convergency. [Conversion angle at each end of the route adds up to make the full expected convergency over the route]

Answer 47

The distance between two meridians along a given latitude. Departure (NM) = change in longitude (in minutes) x cos(latitude)

Answer 48

- 1NM = 6080 ft - 1m = 3.28 ft - 1 inch = 2.54 cm - 1NM = 1.852km

Answer 49

Large scale - lots of detail, high representative fraction, BIG fraction, SMALL divisor (e.g. 1/50,000) Small scale - low level of detail, small representative fraction, SMALL fraction, BIG divisor (e.g. 1/500,000)

Answer 50

The mini version of Earth (globe) reduced in size by a scale factor, which is used to make charts (using projections).

Answer 51

Perspective charts use geometric projections, whilst non-perspective charts use mathematical models. Most used models are non-perspective but can be thought of as projections which are modified matematically.

Answer 52

- Azimuthal/Plane: Simple projection of globe onto paper underneath, works @ poles - Cylindrical: Project from light inside earth onto cylinder wrapped around it (touching at equator) - Conical: Similar to cylindrical but touches at a higher/lower latitude.

Answer 53

- Scale can't be constant and correct - Shapes of large areas can't be represented perfectly However over small enough areas the errors in this can be manageable.

Answer 54

A chart where navigation bearings are correct, i.e. angles on the Earth must be represented correctly on the chart and shapes are shown correctly. Essential for navigation charts, but a chart focussing on land areas may not have this property.

Answer 55

1) Meridians and parallels must be at 90 degrees 2) At any point on a chart, scale should be the same in all directions, or should change at the same rate in all directions

Answer 56

Chart convergency = real world convergency [approximately] The two orthomorphic conditions together achieve this.

Answer 57

Adjusted version of the cylindrical projection which adjusts latitudes so that N-S changes in scale are same as E-W changes in scale. Thus is a mathematically adjusted, non-projection chart. Looks like the map of the world we are used to seeing.

Answer 58

Since meridians of longitude are all parallel, rhumb lines are straight lines, great circles aren't. When plotting (e.g. position from VOR) we use straight lines. VOR information gives us great circle headings so need to convert these to rhumb to allow a straight line plot on mercator.

Answer 59

Meridians are shown as parallel so chart makes departure appear constant. Need to adjust scale at higher latitudes based on true departure. Scale @ latitude = scale @ equator x (1/cos(lat)) [if scale = 1/500,000, do 500,000 x cos(lat)]

Answer 60

This is 1/cos(angle). Used in the mercator scale calculation, so that: Scale @ latitude = scale @ equator x secant(lat)

Answer 61

At 8 degrees from equator, scale is x 1/cos(8) = x 1/0.99 so 1% change in scale. Thus measurements accurate to within 1% up to 8 degrees (c. 500NM) from equator.

Answer 62

Rectangular

Answer 63

Great circles are concave to the equator (convex to the poles). i.e. show the concave side to the equator

Answer 64

This is the parallel of latitude that touches the cone in the projection. Scale expands either side of this latitude. AKA parallel of tangency

Answer 65

Angle of the triangle at the point of the cone. Calculated as 2 x standard parallel latitude. e.g. 60 deg latitude, apex angle is 120, creating a 180 triangle with 30 degrees at the base where cone is tangential with latitude 60

Answer 66

Conical chart is laid out flat by cutting up one median, leaving a circle with a chunk cut out. The arc of the chart (or sector of the chart) is based on the latitude of the chart. Arc of sector = change of longitude x sin(parallel of origin) [for full 360 degree chart just sin(parallel of origin)]

Answer 67

This is the same as the arc of sector (i.e. change in angle of medians over given longitude). Chart convergence = change of longitude x sin(parallel of origin)

Answer 68

Represented by "n", this is the sine of the parallel of origin. Used to determine chart convergence over a given change in longitude.

Answer 69

Brings the cone inside the reduced earth, so parallel of tangency now a parallel of origin (doesn't touch the cone). 2 points where the cone touches earth are the standard parallels. The scale contracts between the standard parallels and expands outside them.

Answer 70

On lambert conical chart, upper standard parallel should be 1/6th from top of chart, lower standard parallel 1/6th of the way from bottom of chart. This way scale is fairly regular over the whole chart.

Answer 71

No impact, the cone is reduced in size (or pushed down), but shape is identical.

Answer 72

- Yes, orthomorphic - Parallels 90deg to meridians - Rhumb lines concave to pole - Concave to the parallel of origin, but only very little, can use straight lines in practice

Answer 73

Conversion angle is based on Earth convergence, so: 0.5 * ch. long. * sin(mid lat) DON'T use half of chart convergence.

Answer 74

A straight line between two points is at an angle to the rhumb line of 1/2 chart convergence. So @ parallel of origin this is equal to earth convergence and great circle is a straight line, but at other latitudes earth convergence is different and great circles are concave to the parallel of origin.

Answer 75

At the mid-meridian point of a route on lambert chart, all types of line between 2 given points (straight line, rhumb line, great circle) will be parallel to each other.

Answer 76

Depends on how far apart the standard parallels are, the further apart, the less the accuracy. UK CAA 1:500,000 chart covers 5 degrees latitude so only has 1% error.

Answer 77

24 degrees total latitude, 16 degrees between the standard parallels.

Answer 78

Plotted straight line headings will correctly follow great circles. However, heading will change along the line (just as in real life along a great circle), so it is critical to plot the line from the same position where heading is measured.

Answer 79

Lambert great circle lines need to be plotted from the point of measuring heading. VOR & VDF headings measured at the stations, so plot from there. ADF & AWR headings measured from aircraft, so plot from there.

Answer 80

Difference will be based on chart convergence between the two points. Draw a diagram of the lines to figure out whether to add or take away. Need to draw a dummy meridian line at the same angle as at the origin point at the new point.

Answer 81

= 90 degrees - latitude

Answer 82

Projection from the pole itself onto a flat piece of paper under the other pole. Creates a circle covering up to the entire hemisphere, with straight line meridians and concentric circles for parallels of latitude.

Answer 83

Correct at the pole it touches. Elsewhere expands at the rate of sec^2(0.5 x co-latitude) [secant squared of half the co-latitude]

Answer 84

@ 78 latitude, scale is a factor of: (1 / cos( (90-78) / 2 ) )^2 = 1/0.989 So around 1% accuracy down to 78 latitude (down to 3% at 70 latitude)

Answer 85

- Yes, orthomorphic - Parallels 90 deg to meridians - Rhumb lines concave to pole - Great circles concave to pole (less so than rhumb lines)

Answer 86

Basically a special case of lambert conical with n = 1 So = change in longitude

Answer 87

Great circle over the pole is a straight line.

Answer 88

Straight line to rhumb line angle is 1/2 chart convergence = 45 degrees. Rhumb line to great circle is conversion angle = 1/2 x change in long x sin(70) = 42.3 degrees This 2.7 degree error is acceptable, so down to 70 latitude can take great circles to be straight lines.

Answer 89

Great circles taken to be straight lines. Draw the circular chart (NH draw meridian from bottom of circle to pole, SH draw meridian from pole to top of circle, that way East is always on the right). Draw in the points and the track between them, use geometry of triangle with the pole to determine angles. REMEMBER: Answer will be TRACK, not the angle in the triangle!

Answer 90

- Real drift: 1/100th of a degree per hour for INS, 1/10th of a degree per hour for DG mode. Small enough to ignore. - Earth rate: Due to gyro syncing to a fixed point in space, error factor is 15 x sin(latitude) / hour - Transport Wander: Essentially convergence

Answer 91

Real drift can be ignored. Transport wander can also be ignored as we want to keep a static version of north in grid navigation. Therefore only need to adjust for earth rate.

Answer 92

Use Greenwich meridian as grid north in both hemispheres. In NH, convergence is negative of longitude. In SH, convergence is equal to longitude.

Answer 93

Fix: Position determined from radio aids Pinpoint: Position found by map reading

Answer 94

Magnetic so they can be easily utilised by pilot in flight

Answer 95

Below 5,000ft - 1,000ft Above 5,000ft - 2,000ft

Answer 96

Anticlockwise Elliptical

Answer 97

Orbit of each planet is an ellipse with the Sun as one of the foci

Answer 98

The line joining the planet to the sun sweeps an equal area in an equal amount of time. Thus the planet has to go faster when it is closest to the Sun.

Answer 99

The square of the time a planet takes to orbit the sun (sidereal period) proportional to the cube of mean distance from the sun. Square of time (ST) Cube of distance (CD)

Answer 100

Perihelion - When sun is closest to the earth (app. 4th Jan) Aphelion - When sun is furthest from the earth (app. 4th July)

Answer 101

approx. Summer Solctice: 21st Jun Autumn Equinox: 21st Sep Winter Solstice: 21st Dec Spring (Vernal) Equinox: 21st Mar

Answer 102

Plane of equinoctial is the plane of the equator. Plane of elliptic is the plane of the Earths path around the sun. These two are at 23.5 degrees to each other AT ALL TIMES. This is called the "obliquity of the elliptic".

Answer 103

The shape in the sky if you plot the midday position of the sun through the year. Roughly a figure of 8 (one loop much bigger than the other). AKA Eliptic

Answer 104

Imaginary sphere around a planet. Can imagine all other celestial bodies as being projected onto points on this sphere.

Answer 105

The point on the celestial sphere directly "above" a point on Earth. Above meaning opposite direction to gravity, opposite direction to the centre of Earth.

Answer 106

Analogous to the latitude at which the Sun appears directly overhead. Follows sine pattern over the year.

Answer 107

Sidereal day is as measured from a distant planet, time taken to see the same point again. Apparent solar day based on when the sun passes overhead and is slightly longer as the planet moves anti-clockwise around the sun so the planet needs to turn a little more to get the sun back overhead.

Answer 108

Because apparent days are affected by the earth going around the sun, length isn't constant and varies through the year: 16 min max difference in November, second peak of 14 min in February [between mean solar day and apparent solar day]

Answer 109

The mean sun is an imaginary sun travelling along the celestial equator at a uniform speed. Related to difference between apparent solar day (when the real sun appears overhead) and our adjusted mean solar day.

Answer 110

Sidereal year: 365 days 6hrs Tropical year: 365 days 5hrs 48.75 mins

Answer 111

To maintain tropical year length have a leap year every 4th year. But for centennials only if the first 2 digits are divisible by 4. e.g. 2000 is leap, 2100 is not.

Answer 112

Measured as # degrees from a given meridian, refers to the angle at which a given object appears overhead. e.g. something at Greenwich hour angle 270 is currently overhead longitude 090E.

Answer 113

1 hour = 15 degrees On calculator use [deg ' "] key to input longitude and divide by 15 to get hrs:min:sec

Answer 114

Universal time kept by nuclear clocks. Gets regularly corrected to line up with GMT so can be considered the same, but isn't exactly.

Answer 115

The exact local time based on longitude adjustment from UTC (Greenwich). Adjusts by minutes and hours, not just hours.

Answer 116

A time period adopted by a given country or land area to allow standard time keeping across it.

Answer 117

Whatever the time is at Greenwich, UTC + 4 means add 4 hours. So midday at Greenwich is 1600 at UTC+4, is 0700 at UTC-5. Paris is UTC+1 as it is later there.

Answer 118

Always add one hour to Local standard time.

Answer 119

Roughly at 180W/180E, the line over which date changes. WESTBOUND => ADD A DAY [DO NOT get confused between "Easterly" and heading to Eastern Hemisphere, they are OPPOSITE!]

Answer 120

Longitude East => Greenwich least Longitude West => Greenwich best [Go through Greenwich (not international date line) to keep things simple!]

Answer 121

The horizon that can be sensed by instruments (e.g. spirit level), i.e. straight line tangent to earth at a given point on the surface.

Answer 122

12hrs 6 mins. Extra 6 mins is due to the last edge of sun dipping below sensible horizon when the centre of the sun is 0 deg 50' below (i.e. 3 mins of time).

Answer 123

When sun (centre of it) is between 0 deg 50' and 6 degrees below the sensible horizon.

Answer 124

Nautical: Sun at 6 to 12 degrees below horizon Astronomical: 12 to 18 degrees

Answer 125

From end of evening civil twilight to beginning of morning civil twilight, or such period between sunset and sunrise prescribed by local authority.

Answer 126

Time it takes sun to move from 0 deg 50' to 6 deg is easily calculated at equator: 5 deg 10' => 21 mins

Answer 127

There is a special case at high latitudes where the sun goes below the equator but not quite below 6 degrees. So there is only one twilight in the middle of the night, between sunrise and sunset. Marked in almanac with //////

Answer 128

At altitude sunrise is earlier and sunset later as you are "looking around" the earth at the sun. Twilight will be shorter as the refractive effect of the atmosphere is reduced.

Answer 129

Water features: Blue Built up areas: Yellow Woods: Green Contours: Brown

Answer 130

Climbing: 2/3 of alt between bottom and top of climb Descending: 1/2 of alt between top and bottom of descent [For WINDSPEED ALSO!]

Answer 131

When snow covers the ground and can't be distinguished from the sky to be able to identify a horizon.

Answer 132

1 degree every 5 years

Answer 133

Heading correction = track angle + closing angle

General Navigation Flashcards

(161 cards)