Daniel Phillips's Air Navigation course notes



Daniel Phillips's Air Navigation course notes


Covers earth magnetism, maps (scales, showing relief, projections, used by the RAF), reciprocal bearings, methods of reporting position, magnetic compasses, air speed indicators, time scale, altimeter, meteorology, computor [sic], fixes by position lines, course for reciprocal track, rhumb [sic] line track + distance and W/T bearings.





48 double lined page handwritten notebook with cover


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1653229 PHILLIPS

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[underlined] AIR NAVIGATION [/underlined]

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[underlined] FORM OF THE EARTH [/underlined]

[underlined] Shape: [/underlined]
Oblate Spheroid.
The difference between the length of the equatorial diameter and the North-South diameter is 27 miles.

[underlined] Axis: [/underlined]
That diameter about which the earth revolves.

[underlined] Poles: [/underlined]
Extremities of axis of rotation.

[underlined] Great Circle: [/underlined]
Circle on the surface of a sphere, the plane of which passes through the centre of the sphere. The shortest distance between two points on the surface of a sphere is the minor arc of the great circle passing through the two points.

[underlined] Small Circle: [/underlined]
Circle on the surface of a sphere, the plane of which does not pass

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through the centre of the sphere.

[underlined] Equator: [/underlined]
A Great Circle whose plane is at right angles to the axis of the earth.

[underlined] Parallel of Latitude: [/underlined]
A Small Circle parallel to the Equator.

[underlined] Meridian: [/underlined]
A Semi-great Circle joining the Poles. (Direction of True North is not the same at Edinburgh and Glasgow)

[underlined and centred] LATITUDE [/underlined and centred]
Latitude is defined as:
The Arc of meridian between equator and place in question – named North or South.

[diagram] N – North S – South O – Centre of Earth. [/diagram]
Lat. P = arc PQ

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[underlined and centred] LONGITUDE [/underlined and centred]
Longitude is defined as:
the smaller arc of the equator intercepted between the Prime Meridian (0[degree symbol]) and the meridian of the place in question – named East or West.

[diagram] G – Greenwich
Long. P = arc RT

[underlined] Graticule: [/underlined]
Network formed on a map or chart by meridians and parallels of latitude.

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[underlined and centred] VARIATIONS [/underlined and centred]
[underlined] VARIATIONS [/underlined]
In general, a freely suspended compass needle does not point to [underlined] True North, [/underlined] but, if not influenced by any iron or steel in the neighbourhood, it points to [underlined] Magnetic North. [/underlined]

The angle between True North and Magnetic North is called the [underlined] Angle of Variation [/underlined] (Var.)

When Magnetic North is to the [underlined] West [/underlined] of True North, the Variation is [underlined] Westerly. [/underlined] (Negative)

When Magnetic North is to the [underlined] East [/underlined] of True North, the Variation is [underlined] Easterly (Positive) [/underlined]
[diagram] Var. is West, or Negative Co(M) – x = Co(T)

[diagram] Var. is East, or Positive Co(M) + x = Co(T)

[underlined] N.B: [/underlined] Towards the true, the signs are there.

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[underlined] Magnetic Variation is not Constant [/underlined]
All statements of Magnetic Variation must bear the place, date, & amount of annual change. e.g. Var. Swansea (1942) 12°w Annual decrease 11’

[underlined and centred] METHODS OF SHOWING VARIATION ON MAPS [/underlined and centred]
1. Isogonals, with values given.
2. Marginal Diagram.
3. Statement in Words, e.g. Mag. Var. 12w (1942)
4. Double Compass Rose[?]

[underlined] Isogonal: [/underlined] a line joining points of [underlined] equal Variation [/underlined] at a particular time.
[underlined] Agonic Line: [/underlined] a line passing through points of [underlined] Zero Magnetic Variation [/underlined] at a particular time.

[underlined and centred] APPLICATION OF VARIATION [/underlined and centred]
1. [underlined] For flights: [/underlined] Apply Variation for mid-point of track.
2. [underlined] For bearings: [/underlined] Apply Variation for the point where the observer’s compass is situated.

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[underlined and centred] DEVIATION [/underlined and centred]
Due to the magnetic field of the aircraft, a compass needle does not, in general, point towards Magnetic North, but towards [underlined] “Compass North”. [/underlined]

This Compass North is not the same for all headings of the aircraft. It is pre-determined for the Cardinal and Quadrantle headings of the aircraft, and a [underlined] Deviation [indecipherable word] (FORM 316) [/underlined] is made for the particular aircraft.

[Diagram] Dev. Is West or Negative Co(c) – x = Co(m)
[Diagram] Dev. Is East or Positive Co(c) + x = Co(m)

[underlined] N.B. [/underlined] Towards [underlined] the true, the signs [/underlined] are true. Deviation for bearing depends only on the heading of the aircraft.

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[underlined and centred] USE OF CORRECTORS [/underlined]
Deviation can be largely removed by counter-balancing local magnetism with fields from magnets of suitable strength and position.

Such magnets are called [underlined] Correctors. [/underlined]

[underlined and centred] SEQUENCE OF OPERATIONS [/underlined and centred]
1. Navigator works out Co(T) from chart.
2. Navigator applies Var. to Co(T) to obtain Co(M)
3. Navigator applies Dev. To Co(M) to obtain Co(c)
4. Navigator passes Co(c) to pilot.
5. Pilot sets Co(c) on compass.

[underlined and centred] METHODS OF GIVING SCALE. [/underlined and centred]
1. [underlined] By Representative Fraction (R.F.) [/underlined]
e.g. 1:500,000 Topographical map of Europe.

[underlined] Exercise [/underlined] To find R.F. for ¼” Ordnance Survey of G.B.
R.F. = ¼ [over]1760 x 12 x 3 = 1 [over] 253440.

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2. [underlined] By a Graduated Scale line [/underlined]
e.g. 1:500,000 topographical map.
3. [underlined] By a statement in words [/underlined]
¼“ O.S. map of G.B. has scale of ¼“ to 1 mile.

[underlined and centred] METHODS OF SHOWING RELIEF [/underlined and centred]
1. [underlined] Contours and form lines [/underlined]
[underlined] Form lines [/underlined] are only approximately correct.
[underlined] Vertical Internal [/underlined] (V.1) is the difference in altitude shown by adjacent contours.
Horizontal Equivalent is the distance between adjacent contours.

V.1 [over] H.E = GRADIENT [diagram]

2. [underlined] Layer Tinting [/underlined]
3. [underlined] Spot Heights [/underlined]
4. [underlined] [indecipherable word] [/underlined] [diagram] Lines are closer together where hills are steepest.
5. [underlined] Hill Shading [/underlined] Pictorial method – shadow of hills when illuminated from right-angles.
[diagram of hill and shading on map]

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[underlined] MERCATOR’S PROJECTION [/underlined]
The earth is spherical in shape. It is obviously impossible to represent perfectly the topography of the earth on a flat surface.

When a map is constructed, there is a certain aim in mind e.g. [underlined] Rhumb lines [/underlined] to be straight lines. This sim determines the projection that is used.

[underlined] Mercator’s Projection [/underlined] is used when it is desired to have [underlined] straight lines [/underlined] representing [underlined] Rhumb lines, [/underlined] and [underlined] directions on the earth properly represented [/underlined] on the chart.

Consequent on the Rhumb lines being straight lines, [underlined] Meridians [/underlined] must be parallel straight lines.

Obviously, a result of making the non-parallel meridians of the earth’s surface parallel on Mercator’s Projection, is expansion of E-W distances at all points away from the equator.

[two diagrams] AB is less than A’B’

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Unless there is a corresponding expansion in N-S direction, directions will not be properly represented.

[diagram] QR and TV are meridians on the earth’s surface. TV is represented by T’V on Mercator’s projection. B must be carried to X, not to B’ in order that direction AB shall be properly represented.

Hence the scale of [underlined] latitude [/underlined] and [underlined] distance [/underlined] is [underlined] not constant. [/underlined]

Areas and shapes are further not faithfully represented.

For the N. Hemisphere, [underlined] Rhumb lines & Great Circles [/underlined] are as follows on the globe:- [diagram]

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On Mercators Projection, the [underlined] Great Circle [/underlined] and [underlined] Rhumb Line [/underlined] appear as follows:- [diagram]

[underlined and centred] PROPERTIES OF MERCATOR’S PROJECTION. [/underlined]
1. [underlined] Rhumb lines [/underlined] are straight.
2. [underlined] Great Circles [/underlined] are curves convex to nearer pole.
3. [underlined] Directions [/underlined] are truly shown.
4. [underlined] Scale of Latitude and Distance [/underlined] is not constant.
5. [underlined] Shapes and areas [/underlined] are distorted.
6. [underlined] Scale of Longitude [/underlined] cannot be used for measuring distances.

[underlined] Mercator’s Projection is Orthomorphic [/underlined]
i.e. the scale is the same in all directions at one point or over a small area.

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[inserted] International Modified Polyconic [/inserted]
[underlined] PROPERTIES OF CONIC PROJECTIONS [/underlined]
1. [underlined] Meridians [/underlined] are straight lines converging towards the Poles
2. [underlined] Parallels of Latitude [/underlined] are curves [deleted word] [underlined] concave [/underlined] to the nearer pole.
3. [underlined] Great Circles [/underlined] are approximately straight lines.
4. [underlined] Rhumb Lines [/underlined] are curves concave to the nearer pole.
5. [underlined] Scale [/underlined] is approximately constant for whole map.
6. [underlined] Shapes and Areas [/underlined] are faithfully represented.
7. [underlined] Angle of track [/underlined] is measured at mid-meridian of track.

[underlined and centred] PROPERTIES OF CASSINI’S PROJECTION [/underlined and centred]
1. [underlined] Meridians [/underlined] are curves converging towards nearer pole, with the exception of the central meridian, which is a [underlined] straight line. [/underlined]
2-7. Exactly as for [underlined] Conic Projections [/underlined]

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[underlined and centred] GNOMONIC CHARTS [/underlined and centred]
1. [underlined] Great circles [/underlined] are exactly straight lines
2. [underlined] Directions, [/underlined] except at point of tangency, are not properly given.
3. [underlined] Shapes and areas [/underlined] are not faithfully represented.
4. [underlined] Scale [/underlined] is not constant for whole chart.
5. [underlined] Used [/underlined] (a) for finding the lat. & long. Of intermediate points of the Great Circle between two widely separated places. These points are plotted on a [underlined] Mercator’s Projection, [/underlined] and the track followed is the series of [underlined] Rhumb lines [/underlined] between them.
(b) for obtaining Great Circle bearings.

[underlined and centred] MAPS IN USE BY R.A.F. [/underlined and centred]
1. [underlined] 1/1,000,000 Plotting Series G.S.B.S. 4080. [/underlined]
(a) Used for Plotting.
(b) Mercator’s Projection.
(c) Black outline, with important towns and rivers marked, and high ground shown by [underlined] Hachuring. [/underlined]
(d) Variation shown by [underlined] Isogonals. [/underlined]

[underlined] 1/500,000 Topographical Map of G.B. and Europe. [/underlined]
(a) Used for map-reading at heights above 3,000’
(b) Conic Projection.
(c) Relief shown by contours, spot heights, & layer tinting.
(d) Variation shown by Isogonals, Marginal Diagram, & Statement in Words [N.B.
Isogonals only for map of Brest area]

3. [underlined] 1/250,000 Topographical Map of Europe. [/underlined]
(a) Used for locating a particular objective when 1/500,000 map gives insufficient detail.
(b) Conic Projection.
(c) Relief shown by contours, spot heights, & layer tinting, except for maps covering areas that are plentifully wooded, when hill shading is used instead of layer tinting.
(d) Variation is shown by Isogonals [In the older maps, marginal diagrams & statements in words are also used].

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4. [underlined] Target Maps [/underlined]
(a) Large Scale
(b) Usually Photographs
(c) Secret.

5. [underlined] ¼” O.S. of G.B. [/underlined]
(a) Used for map reading at low altitudes.
(b) Cassini’s Projection.
(c) Relief shown by contours, spot heights, & layer tinting.
(d) Variation shown by Marginal Diagram, Statement in Words, Double Compass
(e) Rose.

6. [underlined] Admiralty Charts. [/underlined]
(a) Of little use in wartime.
(b) For list of Marine Light Signs see below:-
[underlined] Systems of Lights. [/underlined]
Lights may be divided into two classes:-
(a) Those which do not change colour during a system of changes;
(b) Those which change colour during a system of changes.

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F = fixed – a continuous steady light.
FL = flashing – duration of flash always less than that of darkness.
GP.FL = Group flashing – a group of two or more flashes showing at regular intervals.
Occ = Occulting – a steady light with, at definite intervals, a sudden and total eclipse - duration of darkness equal to, or less then, duration of light.
GP.Occ = Group Occulting – a steady light with, at definite intervals, a group of two or more sudden eclipses.
F.FL. = fixed & flashing – a fixed light varied at intervals by a group of two or more flashes of relatively greater brilliance.
REV. = revolving – light gradually increasing to full brilliance, then decreasing to eclipse.

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ALT. = Alternating – changing colour.
- Interval between commencements of the same phase.
(U) = Unwatched – cannot be relied upon.
VIS. = Visible – height of eye 15’

e.g. LT. ALT. FLWR. Or[?] 30 sec(U) Vis 11m.
Such a light would show every 30 secs. one white & one red flash; visible 11 naut. miles; unwatched.

[underlined and centred] RECIPROCAL BEARINGS [/underlined and centred]
[diagram] To find Recip., add 180°.
[diagram] To find Recip., subtract 180°.
[underlined] RULE: [/underlined] To find reciprocal, subtract 180° if given angle is over 180°; if not, add 180° to given angle.

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[underlined and centred] METHODS OF REPORTING POSITIONS [/underlined and centred]
1. [underlined] By Place names [/underlined] (in CAPITAL letters) e.g. NEWTON ABBOTT
2. [underlined] By Lat. & Long. [/underlined]
3. [underlined] By Graticule Reference System [/underlined] (Lettered co-ordinate system) [underlined] [R.A.F. Method] [/underlined]
[diagram] Parallel of Lat [underlined] below [/underlined] point, and Meridian to [underlined] left [/underlined] of point is taken whether in lat E. or W. Number of minutes put in after letters.
P is given as NO CD 2045.

4. [underlined] Bearing & distance from a Prominent position [/underlined]
[diagram] Bearing is taken from [underlined] landmark, [/underlined] not from aircraft position.
Bearing & distance of A from X lighthouse: A is 125 XLat. 12 n.mls.

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5. [underlined] By Graticule Reference System [/underlined] (Lettered Co-ordinate system) [underlined] [R.N. Method] [/underlined]
Bearing of P is taken from a convenient intersection of Parallel of Latitude & Meridian. P is given as 050[degree symbol] MNCD 40 nmls.

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[underlined] MAGNETIC COMPASS [/underlined]
The function is to indicate North (Magnetic) so that we can refer to this for measuring courses or bearings.

1. [underlined] Grid Ring: [/underlined]
A ring capable of rotation [underlined] in azimuth. [/underlined] It is graduated clockwise from North through 360°. On it the [underlined] Cardinal [/underlined] points are marked with luminous letters, and each [underlined] Quadrantal [/underlined] point with a luminous dash. It can be clamped in any desirable position to the top of the compass.

2. [underlined] Grid Wires. [/underlined]
Two luminous wires parallel to the N-S line of the Grid Ring.
Used for ease of steering. Pilot steers course by keeping the grid wires parallel to the compass needle, [underlined] Red on Red. [/underlined]

3. [underlined] Compass Bowl: [/underlined]
A cylindrical container mounted to prevent vibration; it contains the Magnet System, and is completely filled with the

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[underlined] compass liquid, [/underlined] which consists of 80% alcohol and 20% distilled water.

4. [underlined] Lubber Line: [/underlined]
A short luminous line inside the compass bowl which indicates the heading of the aircraft.

5. [underlined] Magnet System: [/underlined]
Fitted with [underlined] damping wires [/underlined] which, if the compass needle is displaced from North, set up a resistance by their motion through the Compass liquid so that the compass needle comes slowly back to, and stops on, North i.e. an [underlined] aperiodic [/underlined] or [underlined] dead-beat motion. [/underlined]
In order to cut out the effect of [underlined] Magnetic Dip, [/underlined] the magnet system is designed so that its Centre of Gravity is [underlined] below [/underlined] the point of suspension; this reduces the effect of dip to only a few degrees, but as a result of it the magnet system is [underlined] Pendulous. [/underlined]

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[underlined To set a Course: [/underlined]
1. Apply Variation to Co(T) – done by navigator.
2. Apply Deviation to Co(M) to obtain Co(C) – done by navigator.
3. Set Co(C) against [underlined] Lubber line [/underlined] by releasing and turning [underlined] grid ring [/underlined]
4. Clamp grid ring.
5. Turn aircraft until [underlined] N [/underlined] end of grid wires is over [underlined] N [/underlined] end of needle (putting [underlined] Red on Red [/underlined])
[underlined] To Read a Course: [/underlined]
1. Unclamp grid ring.
2. Turn grid ring until [underlined] N [/underlined] end of grid wires is over [underlined] N [/underlined] end of needle [underlined] (red on red) [/underlined]
3. Clamp grid ring.
4. Read Co(C) against Lubber Line.

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[underlined and centred] TURNING ERRORS [/underlined and centred]
Due to the fact that it is necessary to use a [underlined] Pendulous magnetic system, [/underlined] errors arise in the reading given by a P Compass during [underlined] turns. [/underlined]
These occur when the aircraft is banked, the magnetic system now being able to act to some extent as a [underlined] Dip Needle. [/underlined]

1. [underlined] Turns through North [/underlined]
(a) To E. – E. deviation.
(b) To W. – W. deviation.

During these turns, the grid wires & the needle turn in the same direction. Hence, in order to obtain the correct turn, the pilot must [underlined] not [/underlined] allow the grid wires to approach the needle, but stop some degrees away. When the turn is completed, the needle will move back to correct position.

As the needle & the grid wires turn in the same direction, there may be 3 effects:-
i) When the aircraft turns more quickly than the needle (in [underlined] slow [/underlined] turns),

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a turn of [underlined] smaller [/underlined] amount than the actual turn is indicated.
ii) When the aircraft & the needle turn at the same rate, [underlined] no turn [/underlined] is indicated.
iii) When the needle turns more quickly than the aircraft (in [underlined] steep [/underlined] turns), a turn in the [underlined] wrong direction [/underlined] is indicated.
These effects are know as [underlined] Northerly Turning Errors [/underlined]

2. [underlined] Turn through South. [/underlined]
(a) To E. – E. deviation.
(b) To W. – W. deviation.

In both cases, needle & Grid wires turn in opposite directions, towards each other. Hence, if pilot follows compass, he will not turn [underlined] far enough. [/underlined] If pilot is to make correct turn, he must take his grid wires [underlined] over and past [/underlined] the needle. When the turn is complete, needle will return to correct position.

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3. [underlined] Turns through East. [/underlined]
(a) To N. – no deviation; no error.
(b) To S. – no deviation; no error.

4. [underlined] Turns through West [/underlined]
(a) To N. – no deviation; no error.
(b) To S. – no deviation; no error.

N.B. All these deviations are reversed for turns in S. Hemisphere (in S. Hem. [line covered and indecipherable]

[underlined] DECELERATION ERRORS. [/underlined]
(a) [underlined] Northerly courses: [/underlined]
No deviation; no error.
(b) [underlined] Southerly courses: [/underlined]
No deviation; no error.
c [underlined] Easterly courses: [/underlined]
Westerly courses.
[indecipherable word] pilot follows compass [three indecipherable words] N

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[underlined and centred] AIR SPEED INDICATOR [/underlined and centred]
[underlined] Theory [/underlined]
If a tube, with one end closed, is moved rapidly through air, so that the open end points against the current of air, the pressure in this tube will be greater than the atmospheric pressure at the same height.

Obviously, with a suitable means of measuring this excess pressure in terms of speed, the air speed can be found.

[underlined] Construction [/underlined]
[diagram] System of linkages used to magnify changes in volume of expansion chamber

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The [underlined] Pitot Head [/underlined] is led to the inside of the expansion chamber. The free side of the expansion chamber moves under the influence of the excess pressure, and this movement, magnified by a suitable system of linkages, causes a pointer to move over a scale graduated in M.P.H. or Knots.

In order to have around the expansion chamber the correct pressure for the height at which the aircraft is flying, the expansion chamber is surrounded by a metal box which has a lead to the [underlined] Static Pressure Head [/underlined]

[underlined] Notes: [/underlined]
i) The inclination of the Pitot Head and Static Pressure Head to the airflow must not be greater than 10°
ii) The Pitot Head and Static Pressure Head are mounted nowadays in one unit called the [underlined] Pressure Head. [/underlined]
[diagram showing air flow]
iii) The Pressure Head should be mounted clear of slipstream and eddy currents from mainplanes etc.
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[underlined] Errors: [/underlined]
(a) [underlined] Position Error. [/underlined] This arises from the fact that it is impossible to find a perfect position free of slipstream etc for the Pressure Head, within a distance of 20 feet from the aircraft.
(b) [underlined] Instrument Error: [/underlined] Due to the imperfect elasticity of the Expansion Chamber, and the friction at the Pivots, there is an error called Instrument Error.
These two errors are compounded and entered in the [underlined] Table of Position & Instrument Error.
[chart for Table of Position & Instrument Error]
I.R.S. + P & I Error = G.A.S.

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(c) [underlined] Density Correction: [/underlined] Air Speed Indicators are calibrated to read correctly at density corresponding to Mean Sea Level Pressure (1013.2 millibars), and a temperature of 15° C. Any change in pressure and temperature affects density, and density affects the reading of the Air Speed Indicator.
[underlined] Rules: [/underlined] (i) Add 1.75% of C.A.S. for every 1000’ to obtain T.A.S.
e.g. C.A.S. = 120k. Height 10,000’
T.A.S. = 120 + (17.5% of 120)
= 120 + 17.5 x [deleted] 120 [/deleted] [inserted] 6 [/inserted] [over]
[deleted] 100 [/deleted] [inserted] 5 [/inserted]
= 120 + 21 = 141 knots.

(ii) Use the computer to obtain T.A.S. from C.A.S.

To find C.A.S. given T.A.S. and Height
T.A.S. = 200k. Height 10,000’
200 = C.A.S. + 17.5% of C.A.S.
= 117.5 C.A.S. [over] 100

C.A.S. 200 x 100 [over] 117.5 = 170 Knots.

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[underlined] AMENDMENT [/underlined]

Air Speed and[?] Reading + Instrument Error = Indicated Air Speed
Indicated Air Speed + Position Error = Rectified Air Speed
Rectified Air Speed + compressibility = Equivalent Air Speed
Equivalent Air Speed + density correction = True Air Speed.

A.S.I.R. + I.E. = I.A.S.
I.A.S. + P.E. = R.A.S.
R.A.S. + C. = E.A.S.
E.A.S. + D.C. = T.A.S.

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[underlined] AMENDMENT [/underlined]

[underlined] TIME & DISTANCE SCALE FOR 1:500 000 MAP. [/underlined]
Distance on may travelled in 5 mins at 120 mph = 10 x 1760 x 3 x12 [over] 500 000
= 1.27 inches

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[underlined] TIME SCALE [/underlined]
The time-scale is a device for finding one’s position quickly on a map when on a certain track at a certain G/S. The Scale is marked on celluloid, usually in 5 minute intervals. The distance along the Scale is that which the aircraft would have travelled in an interval of time to the same scale as that of the map (Map Distance).

Thus, by laying the time scale along the map and considering the time representing the given G/S. the position at a given time can be readily found.

The scale of the time-scale [underlined] must [/underlined] be the same as that of the map.

[underlined] USES:[?] [/underlined]
To find [underlined] map distance [/underlined] given G/S and time.
To find [underlined] G/S [/underlined] given map distance and time.
To find [underlined] time [/underlined] given map distance and G/S

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[underlined] THE ALTIMETER. [/underlined]

[underlined] Theory: [/underlined]
Air exerts a pressure because it has weight. Obviously, as one ascends, pressure decreases, as the weight of air above one is less. It is thus evident that, if one has a means of translating the changes in pressure into units of height, one has an Altimeter.

This is performed by observing the movement of the free side of an evacuated capsule whose movement is magnified by a system of linkages, and causes a pointer to move over a scale graduated in [underlined] feet. [/underlined]

[underlined] Construction: [/underlined]

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The vacuum chamber is prevented from collapsing by the action of a spring which resists atmospheric pressure acting on the free side of the capsule. The movement of the free side of the chamber, magnified by a system of linkages, causes a pointer to move over a scale graduated in feet.

The whole apparatus is enclosed in a metal box which has a lead to the Static Pressure Hand[?], so that the pressure utilised by the Altimeter is the correct pressure for the height at which the aircraft is flying.

Incorporated in the instrument is a [underlined] Temperature Compensating Unit [/underlined] which is so adjusted that temperature changes along have no mechanical effect on the reading of the instrument.

[underlined] Isothermally Calibrated Altimeter. [/underlined]
Reads correctly only for an atmosphere which is isothermal at 50° F.

[underlined] Corrections to Isothermal Readings.
(i) Subtract 1% of the indicated height for each 5° F. by which mean temperature of atmosphere is below 50° F., from indicated height.

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e.g. (a) Indicated Height = 10,000’
Temp. at aircraft = 20°F
“ “ M.S.L. = 60°F

10,000’ ---------------------------20% )
) average temp.
) = 40°F.
M.S.L. -------60°F )
Corrected heigh = 10,000’ – 2% of 10,000’
= [underlined] 9800 feet. [/underlined]

(b) Indicated height = 10,000’
Temp. at MSL = 50°F
Normal lapse rate = 3°F / 1000’
[‘therefore’ symbol] Temp at aircraft = 20°F
Average temp = 35°F
Corrected height = 10,000’ – 3% of 10,000’
= [underlined] 9700 ft. [/underlined]

(c Temp. at aircraft = 10° F Indicated height 1000’
“ “ M.S.L. = 40°F
Air temp = 25°F
Corrected height = 10,000’ – 5% of 10000’
= [underlined] 9500 ft. [/underlined]

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ii) The [underlined] Height and Air Speed Computer [/underlined] may be used to correct readings of Isothermal Altimeter [underlined] (Isotherm Pattern) [/underlined]

[underlined] I.C.A.N. Calibrated Altimeter. [/underlined]
International Convention of Air Navigation – reads correctly for standard I.C.A.N. atmosphere i.e. when M.S.L. temperature is 15°C, and lapse rate is 1.98°C per 1,000 ft.

[underlined] Correction to I.C.A.N. Altimeter. [/underlined]
If standard I.C.A.N. atmosphere is not in operation, use [underlined] Height & Air Speed Computer (I.C.A.N. Pattern) [/underlined] to correct indicator height.

i) I.C.A.N. Altimeter can be set on the ground to rad 0’ for height above M.S.L.
ii) When Altimeter is set at 0’ on aerodrome, it also records aerodrome pressure (in millibars)
iii) When Altimeter is set at height of aerodrome above M.S.L., it records M.S.L. pressure. [diagram] Turning knob moves pointer & pressure scale.

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[underlined] LAG: [/underlined]
Owing to the imperfect elasticity of the Vacuum Chamber and the friction at the various pivots, the Altimeter does not immediately record changes of height.
The time interval between actual change of height and its recording on the Altimeter is termed “lag”.
N.B. There is [underlined] no [/underlined] lag in the [deleted word] [underlined] Kollsman[sic] Sensitive Altimeter Mark XIV. [/underlined]


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[inserted] Pressure decreases approximately 1 [indecipherable letters] / 30’.

In practice, the M.S.L. pressure for the area over which the aircraft is flying is set on the Altimeter. Should this pressure change, the new M.S.L. pressure is set.

It is obvious from the diagram that the Altimeter [underlined] over reads [/underlined] when flying from a region of higher pressure to lower pressure, e.g.

i) Flying from A (30’: 1015 mbs[?] ) to 600’: 1012 mbs) Altimeter set at A to read ht[?] above M.S.L.
M.S.L. pressure at A = 1015 + 1 = 1016 mbs.
“ “ “ B = 1012 + 20 = 1032 mbs.
Altimeter [underlined] underreads [/underlined] by 16 x 30 = [underlined] 480 ft. [/underlined]

ii) A (30’: 1015.4 mbs) to B (360’: 1000.4 mbs) Altimeter set at A to read ht. above M.S.L.
M.S.L. pressure at A = 1015.4 + 1 = 1016.4 mbs
“ “ B = 1000.4 + 12 = 1012.4 mbs
Altimeter [underlined] overreads [/underlined] by 4 x 30 = [underlined] 120ft. [/underlined]

iii) A (600’: 1010 mbs) to B (300’: 1008 mbs) Altimeter set at A to read 600’.
M.S.L. at A = 1010 + 20 = 1030 mbs
“ “ B = 1008 + 10 = 1018 mbs
Altimeter [underlined] overreads [/underlined] by [underlined] 360’. [/underlined] At B and[?] ht. = [underlined] 660 ft. [/underlined]

[page break]

iv) A (1200’: 1000 mbs) to B (900’: M.S.L. Press. 1010 mbs)
Altimeter set at A to read 600’.
At A, altimeter underreads by 600 ft.
M.S.L. at A = 1000 + 40 = 1040 mbs.
“ “ B = 1010 mbs
Altimeter [underlined] overreads by 900 ft. [/underlined]
[‘therefore’ symbol] at B, altimeter overreads by [underlined] 300 ft. [/underlined]
Thus altimeter reads at B height of [underlined] 1200 ft. [/underlined]

v) A (1200’: 1000 mb) to B (900’: 1012mb)
Alt. set at A to 600’. [underlined] Find reading at C (800’)
2/3 distance AB from A. [/underlined]
MSL at A = 1000 + 40 = 1040 mb
“ “ B = 1012 + 30 = 1042 mb
“ “ C = 1040 + 4/3 x 2 = 1041.3 mbs.
Altimeter underreads by 4/3 x 30 = 40 ft.
Since altimeter underreads at A 600’,
“ “ “ “ C 640’.
[‘therefore symbol] Altimeter reading at C = [underlined] 160 ft [/underlined]

[page break]

vi) A (900’: 1012 mb) to B (600’: 1014 mb)
Altimeter set at A to 1200’.
[underlined] Find clearance between aircraft & ground when passing over range of hills 5000’ high, halfway between A and B, if altimeter reads 7000ft. [/underlined]
M.S.L. at A = 1012 + 30 = 1042 mbs
“ “ B = 1014 + 20 = 1034 mbs
“ “ halfway = 1042 – 8/2 = 1038 mbs
Altimeter overreads by 4 x 30 = 120 ft
“ “ at A “ 300 ft
Thus “ “ “ 420 ft.

Passing over hills, altimeter reads 7000’
Correct height = 6580 ft
[‘therefore’ symbol] Clearance = [underlined] 1580 ft. [/underlined]

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[underlined] METEOROLOGY. [/underlined]
[underlined] Isobars:- [/underlined] Lines joining points of equal M.S.L. pressure
[underlined] Millibars:- [/underlined] 1/1000th of a bar (about atmospheric pressure)
Average rate of decrease of pressure with height = 1 mb/30ft.
[underlined] Wind:- [/underlined] On a weather map it is found that the closer the isobars, the stronger the wind.
Experience shows that wind arrows tend to follow the run of the isobars, but they are inclined at ground level towards the side of [underlined] low pressure [/underlined]
[underlined] Buy’s Ballot’s Law [/underlined]
If you stand with back to wind in N. Hem., [underlined] lower pressure [/underlined] is on [underlined] left. [/underlined] Reverse holds for S. Hem.
[two diagrams]

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[underlined] Intensity of wind:- [/underlined] Wind speed is proportional to pressure gradient (rate of change of pressure in a direction perpendicular to the isobar)
The [underlined] Geostrophic Scale [/underlined] enables the speed of the wind at 1500 ft. to be read. [underlined] (pressure gradient wind, [/underlined] or [underlined] pressure wind) [/underlined]

Owing to the friction between the air and the earth’s surface, including mountains, buildings etc, winds that blow at low altitudes are of lower intensity than those in higher altitudes. No general rule can be laid down connecting [underlined] intensity & height. [/underlined]
[underlined] Direction of Wind:- [/underlined] At [underlined] low altitudes, [/underlined] friction affects the direction, the wind being directed towards the [low pressure] side of the isobars.
At [underlined] 1500 ft, [/underlined] the wind blows along the isobars (geostrophic wind)
[underlined] Above 1500 ft, [/underlined] winds from an [underlined] easterly point [/underlined] tend to fall off with height, and above 3000 ft are often replaced by winds from a westerly point. [underlined] Westerly winds [/underlined] tend to increase in intensity.
When wind changes in a clockwise

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direction, it [underlined] veers [/underlined] [arrow showing direction]
When wind changes in an anticlockwise direction, it [underlined] backs [/underlined] [arrow showing direction]

[underlined and centred] PRESSURE DISTRIBUTION [/underlined and centred]
1. [underlined] Depression, or low: [/underlined]
A series of more or less concentric isobars with lower pressure at centre.
2. [underlined] Secondary Depression: [/underlined]
A separate area of low pressure within a pressure. A secondary depression often develops and takes the place of the Primary depression, in which case the weather changes for the worst.

[page break]

3. [underlined] Anticyclone, or High: [/underlined]
A series of more or less concentric isobars with higher pressure at centre.
4. [underlined] Trough of low pressure: [/underlined]
The isobars extending outwards from the depression roughly in V-shape.
5. [underlined] Ridge or Wedge of high pressure: [/underlined]
A bulge in a high pressure system.
6. [underlined] Col:[?] [/underlined]
A neutral area situated between two High and two Low pressure areas.

[page break]

[underlined and centred] DIURNAL VARIATION OF WIND. [/underlined and centred]
Owing to the fact that the earth becomes heated by day, [underlined] turbulence [/underlined] is set up in the lower layers of the atmosphere. This is at a maximum in the afternoon. Hence at this time the ground level wind, and the wind at 1000’ – 1500’, interfere with each other.
From the diagram it is seen that by day the ground level wind [underlined] increases [/underlined] in intensity and [underlined] veers; [/underlined] the wind at 1500’ suffers the reverse changes – [underlined] decreases [/underlined] in intensity and [underlined] backs. [/underlined]
At night turbulence ceases, ground level wind [underlined] backs [/underlined] and [underlined] lulls; [/underlined] wind at 1500’ reaches maximum speed and [underlined] veers. [/underlined]

[page break]
[underlined] BY DAY [/underlined] [diagram]
The rays of the sun heat the sides of the valley causing the air in contact with these sides to expand and rise [underlined] (Convection currents) [/underlined]
The air that flows [underlined] up [/underlined] the valley to replace the ascending air gives rise to an [underlined] Anabatic [/underlined] or [underlined] Ascending Wind. [/underlined]

[underlined and centred] KATAGATIC WIND [/underlined and centred]
[diagram] [underlined] BY NIGHT [/underlined]

By night the earth cools rapidly. The air in contact with earth increases in density, falls, and flows [underlined] down [/underlined] the valley, giving rise to a [underlined] Katabatic [/underlined] or [underlined] Descending Wind. [/underlined]

[page break]

[underlined and centred] LAND BREEZES [/underlined and centred]
[diagram] [underlined] BY NIGHT. [/underlined]
By night the earth cools rapidly to a lower temperature than the sea.
Hence the air over the land will become denser than air over the sea, and there will be a flow of air from land to sea, giving rise to a [underlined] Land Breeze [/underlined] which rarely exceeds 15 m.p.h. The return current can be ignored.

[underlined and centred] SEA BREEZES [/underlined and centred]
[diagram] [underlined] BY DAY [/underlined]
By day the land becomes warmer than sea, giving rise to ascending air over

[page break]

the land. Denser air from the sea flows in to take its place, giving rise to a Sea Breeze.

[underlined and centred] HOW AIR IS WARMED [/underlined and centred]
The source of atmospheric heat is the Sun, which distributes infra-red or heat rays which heat all objects which impede their passage.

Pure, clean, dry air absorbs directly very little heat from the rays, but the earth upon which the sun’s rays fall is warmed considerably [underlined] (Radiation), [/underlined] and consequently the air in contact with it is heated by [underlined] Conduction. [/underlined]

This warmer, and therefore lighter air tends to rise, and so the atmosphere becomes warmer [underlined] (Convection) [/underlined]

[page break]

[underlined and centred] INVERSION. [/underlined and centred]
[centred] No Clouds [diagram] [/centred]

Under certain conditions, temperature may actually [underlined] increase [/underlined] with height, giving an [underlined] inversion. [/underlined]

It occurs most frequently on a clear night in Winter. There are no clouds to re-radiate back to the earth some of the heat radiated by the earth, and hence the earth loses heat rapidly, and becomes cooler than the air above it.

Obviously, the air in contact with the earth loses heat by [underlined] Conduction, [/underlined] and therefore its temperature is lower than that of the air above it.

Hence an Inversion has been formed.

As cold air is denser than warm air, the air in contact with the earth will not rise. This is an example of a [underlined] Stable Atmosphere [/underlined

[page break]

[underlined and centred] ADIABATIC LAPSE RATE [/underlined and centred]
A mass of gas is said to be subjected to an Adiabatic change if no [underlined] heat [/underlined] is given to or taken from the mass suffering the change; e.g. gas in a cylinder with walls lined with non-conducting material.

Consider a mass of gas which has become warmer than the surrounding gas. It rises, but, as it ascends the pressure decreases, and so it [underlined] works [/underlined] against the surrounding gas, losing heat with a consequent reduction in temperature.

For such a persistent change the lapse rate is the [underlined] Adiabatic Lapse Rate [/underlined] of [underlined] 5.4°F/1000’. [/underlined]

Air containing water vapour, but unsaturated, has approximately the same lapse rate as air with no water vapour.

But if [underlined] Condensation [/underlined] occurs, as it will at some point if temperature is progressively reduced, the lapse rate is lower on account of the heat given off during the Condensation.

Hence, for a saturated or wet gas, there

[page break]

is an appropriate lapse rate – the [underlined] Wet Adiabatic Lapse Rate [/underlined] of [underlined] 2.7°F/1000’. [/underlined]

The mass of air considered has an insulating “coat” of air that enables it to be subject to Adiabatic changes.

[underlined and centred] STABLE & UNSTABLE ATMOSPHERE [/underlined and centred]

It is obvious from above table that the [underlined] greater [/underlined] the lapse rate of air, the [underlined] less stable [/underlined] it is.

Conversely, the [underlined] smaller [/underlined] the lapse rate, the [underlined] more stable [/underlined] it is.

[page break]

[underlined] NOTES: [/UNDERLINED]
6000’ 30°F 31°F
5000’ ( 35°F 35°F ) cloud
4000’ ( 40°F 39°F )
3000’ 45°F 43°F
2000’ 50°F 47°F
1000’ 55°F 51°F
0’ 60°F 55°F

Dewpoint[?] 40°F; Lapse Rate 4°F/1900’[?]; Adiabatic 50°F/1000’
Cloud forms at 4000’.
Thus the [underlined] greater [/underlined] the lapse rate, the [underlined] thicker [/underlined] the cloud.

[underlined] Clear ice [/underlined] is found when flying through clouds with supercooled drops in it. These freeze immediately in contact with aircraft.

When flying from above cloud to below cloud, there is a [underlined] change of wind [/underlined] and [underlined] increase of pressure. [/underlined]

Best operational clouds are [underlined] Alto-Stratus [/underlined] and [underlined] Strato-Cumulus. [/underlined]

[page break]

[underlined]BEAUFORT SCALE[/underlined]

[underlined] SCALE NO. [/underlined]
[underlined] GENERAL DESCRIPTION [/underlined]
Dead calm
[underlined] LAND [/underlined]
[underlined] SEA [/underlined]
[underlined] SPEED [/underlined]
[underlined] SCALE NO. [/underlined
[underlined] GENERAL DESCRIPTION [/underlined]
Light air
[underlined] LAND [/underlined]
Shown by smoke but not by weather vane
[underlined] SEA [/underlined]
[underlined] SPEED [/underlined]
1 – 3 mph.
[underlined] SCALE NO. [/underlined]
[underlined] GENERAL DESCRIPTION [/underlined]
Light breeze
[underlined] LAND [/underlined]
Felt on face leaves rustle
[underlined] SEA [/underlined]
Tiny wavelets glassy crests
[underlined] SPEED [/underlined]
4 - 7 mph.

[underlined] SCALE NO. [/underlined]
[underlined] GENERAL DESCRIPTION [/underlined]
Gentle breeze
[underlined] LAND [/underlined]
Twigs moving small flags blow out
[underlined] SEA [/underlined]
Crests begin to break few ‘white horses’
[underlined] SPEED [/underlined]
8 - 12 mph.

[underlined] SCALE NO. [/underlined]
[underlined] GENERAL DESCRIPTION [/underlined]
Moderate breeze
[underlined] LAND [/underlined]
Small branches move dust and papers raised
[underlined] SEA [/underlined]
Small waves become longer ‘white horses’ common
[underlined] SPEED [/underlined]
13 - 18 mph.

[underlined] SCALE NO. [/underlined]
[underlined] GENERAL DESCRIPTION [/underlined]
Fresh breeze
[underlined] LAND [/underlined]
Small leafy trees sway
[underlined] SEA [/underlined]
Spray many ‘white horses’
[underlined] SPEED [/underlined]
19 - 24 mph.

[underlined] SCALE NO. [/underlined]
[underlined] GENERAL DESCRIPTION [/underlined]
Strong breeze
[underlined] LAND [/underlined]
Large branches move telegraph wires whistle
[underlined] SEA [/underlined]
White foamed crest more extensive
[underlined] SPEED [/underlined]
25 - 31 mph.

[underlined] SCALE NO. [/underlined]
[underlined] GENERAL DESCRIPTION [/underlined]
Moderate gale
[underlined] LAND [/underlined]
Whole trees in motion
[underlined] SEA [/underlined]
Waves heap up foam blown off
[underlined] SPEED [/underlined]

32 - 38 mph.
[underlined] SCALE NO. [/underlined]
[underlined] GENERAL DESCRIPTION [/underlined]
Fresh gale
[underlined] LAND [/underlined]
Twigs break off
[underlined] SEA [/underlined]
Streaks of foam
[underlined] SPEED [/underlined]
39 - 46 mph.

[underlined] SCALE NO. [/underlined]
[underlined] GENERAL DESCRIPTION [/underlined]
Strong gale
[underlined] LAND [/underlined]
Chimney pots blow off
[underlined] SEA [/underlined]
Dense streaks of foam affecting visibility
[underlined] SPEED [/underlined]
47 - 54 mph.

[underlined] SCALE NO. [/underlined]
[underlined] GENERAL DESCRIPTION [/underlined]
[underlined] LAND [/underlined]
Trees uprooted
[underlined] SEA [/underlined]
White surface to sea
[underlined] SPEED [/underlined]
55 - 63 mph.
[underlined] SCALE NO. [/underlined]
[underlined] GENERAL DESCRIPTION [/underlined]
[underlined] LAND [/underlined]
Very rare structural damage
[underlined] SEA [/underlined]
Exceptionally high waves sea covered with foam
[underlined] SPEED [/underlined]
64 - 75 mph.
[underlined] SCALE NO. [/underlined]
[underlined] GENERAL DESCRIPTION [/underlined]
[underlined] LAND [/underlined]
Very rare great structural damage
[underlined] SEA [/underlined]
Immense waves sea covered with foam and spray
[underlined] SPEED [/underlined]
Over 75 mph.

[page break]

[underlined and centred] THE NAVIGATIONAL COMPUTOR MARK III [/underlined and centred]
1. [underlined] Airspeed: [/underlined]
Rotate knob until required T.A.S. is exactly below central dot.
2. [underlined] Course: [/underlined] (a) Set required course at black course arrow.
(b) Read course at black course arrow.
3. [underlined] Track: [/underlined] Represented by a red line and shown as drift to port or
4. [underlined] G/S: [/underlined] Read at end of wind Vector.
5. [underlined] W/V: [/underlined] Rotate ring until required wind direction is shown at the black arrow, then draw a line downwards from centre dot to represent wind speed.

1. [underlined] To find course & G/S. [/underlined]
Given track, T.A.S., & W/V.
i) Set W/V.
ii) Set T.A.S.
iii) Set Track at course arrow & judge drift.
iv) Rotate Track to drift on drift scale.
v) Adjust until drift shows on drift scale equals drift line.
vi) Read Co & G/S at end of vector.

[page break]

2) [underlined] To find W/V. [/underlined]
Given Tr.[?] T.A.S. Co. & G/S
i) Set T.A.S.
ii) Set Co.
iii) Set Tr & G/S. using drift.
iv) Rotate ring until end of wind vector is towards operator, & [underlined] read off speed [/underlined] & direction.

3) [underlined] To find Tr. & G/S. [/underlined]
Given W/V., Co., T.A.S.
i) Set T.A.S.
ii) Set W/V
iii) Set Co.
iv) Read off [underlined] drift; find Tr. & read [/underlined] off G/S

4) [underlined] To find W/V by multiple drifts [/underlined]
i) Set T.A.S.
ii) Set first Co(T) against course arrow
iii) Draw fine along 1st drift line.
iv) Set second Co(T) & draw 2nd drift line to cut first
v) Repeat with 3rd Co(T) & drift.
vi) Wind point is point of intersection.
vii) Rotate until wind point is directly below centre dot.
viii) Read off direction & speed.

[page break]

5) [underlined] To find Wind Speed from distance & time. [/underlined]
(a) Set [underlined] distance [/underlined] on outer scale against time on inner scale.
(b) Read off wind [underlined] speed against [/underlined] 60 min. arrow.

6) [underlined] To convert Naut. Mls. To Star. Mls.[/underlined]
(a) Place naut. ml. arrow on inner scale against given number of naut. mls.
(b) Read off Star. Mls. Against Star. Ml. arrow.

7) [underlined] To correct Airspeed (R.A.S. to T.A.S.) [/underlined]
(a) Set [underlined] 57 [/underlined] on inner scale against [underlined] 57 [/underlined] on outer scale.
(b) Rotate inner scale until 57 is against 57 + height on outer scale.
(c) Read off T.A.S. against R.A.S. on inner scale.

[page break]

[underlined] Examples: [/underlined]

Co(T) T.A.S. W/V Tr(T) G/S
255½° 135 K. 193/35K 270° 122K
187° 305K 152/15K 189° 292K
000½° 195K 045/32K 352° 174K

T.A.S. Co(T) G/S Tr(T) W/V
200K 100° 180K 090° 154°/39K
180K 000° 175K 020° 284/61K
220K 330° 225K 338° 235/31K

T.A.S. Co(T) W/V Tr(T) G/S
200K 100° 160/25K 093½° 188K
180K 200° 260/25K 192° 168K
220K 300° 350/25K 294½°[?] 205K

[page break]

[underlined] Fixes by the use of Position Lines. [/underlined]
When two or more position lines intersect, & the point of intersection constitutes a [underlined] fix. [/underlined]

When one or more of the position lines have been transferred, the resulting fix is known as a [underlined] Running fix. [/underlined]

[underlined] Precautions: [/underlined]
(a) Position lines should meet at about 90°; never less than 30°.
(b) If possible, take bearings of objects near the aircraft.
(c) Do not transfer position lines unless necessary.
(d) When possible, use a third position line.

[underlined] Course to make good Reciprocal Track. [/underlined]
1. [underlined] Starboard drift going out:- [/underlined]
Reqd. Co = recip. Co. + 2 drift
2. [underlined] Port drift going out:- [/underlined]
Reqd. Co. = recip. Co. – 2 drift.

[page break]

[underlined] To calculate Rhumb line Track & Distance. [/underlined]

[indecipherable word] Rhumb line Track = [underlined] Ch.[?] long [/underlined]
Ch.[?] mer. part.
Rhumb line distance = Ch. Lat x sec. track

(i) [underlined] R.L. Track [/underlined]
log Ch. Long 3.43136
log Ch. m.p. 3.21676
[‘therefore’ symbol] log tan track = 0.21460
Track = [deleted figures] S 58° 37’ E = 121° 23’

(ii) [underlined] Distance [/underlined]
log Ch. lat 3.07372
log Sec. Tr 0.28336
log distance 3.35708
Distance = 2276.5 n mls.

[underlined] To 121°(T) Distance 2277 n mls. [/underlined]

[page break]

[underlined] W/T Bearings of Range greater than 150 mls.
Northern Hemisphere. [/underlined]
(i) [underlined] Aircraft E. of Transmitter [/underlined]
Great Circle bearing 287°(T)
Conversion angle 3°
Rhumb Line Bearing 284°(T)
Rhumb line laid off from transmitter in direction 104°(T), giving position line in the vicinity of D.R. position of the aircraft.

[page break]

(ii) [underlined] W. of Transmitter [/underlined]
Great Circle bearing 040°(T)
Conversion angle 3°
Rhumb line laid off from transmitter in direction 223°(T), giving position line in the vicinity of D. R. position of the aircraft.

[page break]

188° 181 + 7
286 229 + 57
017 092 - 75
096[?] 130 - 34 [calculation]
138 105 + 33 [calculation]
184 126 + 58
225 140 + 85
320 348 - 28
002 358 + 4
053 024 + 29
093 095{?] [deleted] + 53 [/deleted] [inserted] – 2 [/inserted]

[page break]

[underlined] D. R. COMPASS [/underlined]

[page break]

Regard Gyro contact arm as remaining fixed in position on the inner frame, & therefore the metal & quartz strip as moving relative to it.

If, as in diagram, the inner frame has moved in an anticlockwise direction, the quartz strip will be under the Gyro Contact arm, & the relay circuit broken, i.e., electro magnet not energised, soft iron not attracted, which, by means of push bar, brings contact 2 against Contact 1. This makes circuit containing feel winding 1 of the Reversing motor, & by means of gearing between Reversing motor & Inner Frame, turns the Inner Frame in a clockwise direction. The line of Gyro & inner frame returned[?] into coincidence once again.

If the Inner Frame moves clockwise, then the metal strip is brought under contact arm – relay circuit made, soft iron attracted, contact 2 forced by pushbar to contact 3, thus [inserted] energising [/inserted] feel winding 3, which is oppositely wound to feel winding 1, thus causing Reversing Motor to rotate in reverse direction.

[page break]

By means of gearing, inner frame then rotates (also metal strip) anticlockwise.

Thus, the line of Inner Frame will oscillate slightly about the line of the Gyro, & since the line of the Gyro is in the Earth’s magnetic field (H) (precession of the Gyro controlled by magnet element) the line of Inner Frame will oscillate slightly about direction of Earth’s field. This gives what is known as the Hunt[?] of the Inner Frame, & with instrument functioning correctly, is approximately ½°.

[page break]


[page break]

[calculations and diagram]

[page break]


[page break


[page break]

[symbol] 250 [symbol] 250 UNLIGHTED OBSTRUCTION, ABOVE 60m. = 200ft.
[symbol] 250 [symbol] 250 LIGHTED OBSTRUCTION

[underlined and centred] RADIO-ELECTRIC STATIONS [/underlined and centred]

[page break]

[symbol] )

[page break]

[underlined and centred] CONVENTIONAL SIGNS [/underlined and centred]
[symbol 600] LAND AERODROME. Ht. in Ft. OR METRES.
[symbol 600] LANDING GROUND. Ht. in Ft. OR METRES.
[symbol 600] AIRSHIP BASE. Ht. in Ft. OR METRES.



D Phillips, “Daniel Phillips's Air Navigation course notes,” IBCC Digital Archive, accessed May 20, 2024, https://ibccdigitalarchive.lincoln.ac.uk/omeka/collections/document/27493.

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