Saturday, 30 August 2008

PPL Ex 18 (x): NAVIGATION: (MAX DRIFT & Cross Wind Component XWC)

(Remember - Click on an image to ENLARGE.)


Q. What IS Maximum Drift?
A. It is the maximum drift possible with a given wind strength at a given TAS. The Drift Angle that the aircraft would experience IF the wind was directly ACROSS i.e. at 90-degrees to the Track.

Q. How is this useful to ME?
A. Having calculated the Maximum Drift, it is easy to calculate the Drift Angle for a given Wind Direction relative to the aircraft track.

Fraction of Max Drift: We only consider ANGLES OFF from 0 to 60 and this is done by using 1/6ths Rule:

0-degrees OFF = 0/6
10-degrees OFF = 1/6
20-degrees OFF = 2/6
30-degrees OFF = 3/6
40-degrees OFF = 4/6
50-degrees OFF = 5/6
60-degrees OFF = 6/6
Example 1:
True Air Speed (TAS) = 90kts.
Wind Speed = 27kts.
Max Drift = 60/90 x 27 = 18-degrees.

Assume Wind Direction relative to the Aircraft Track is 20-degrees OFF.
Therefore Drift Angle = 18-degrees X 2/6 = 6-degrees

Example 2:
True Air Speed (TAS) = 100kts.
Wind Speed = 40kts.
Max Drift = 60/100 x 40 = 24-degrees

Assume Wind Direction relative to the Aircraft Track is 30-degrees OFF.
Therefore Drift Angle = 24-degrees X 3/6 = 12-degrees.
Now apply the Drift Angle to the Track to get the Heading.

Example 3: (Illustrated on the 1:500,000 ICAO Aeronautical Chart above)
True Air Speed (TAS) = 90.
True Track = 030
W/V = 050/27
Max Drift = 18
Actual Drift = 6

The wind is blowing from the Right, therefore the Heading is 036-degrees.

Example 4:
True Air Speed = 100
True Track = 140
W/V = 350/40
Max Drift = 24
Actual Drift = 12

The wind is blowing from the Left, therefore the Heading is 128-degrees.

Cross Wind Component (XWC) :
MAX DRIFT - which is an 'angle' has been addressed above. Let's now have a look at CROSS WIND COMPONENT (XWC) which is a 90-degree vector:

The 1/6ths Rule above applies.

Assume that the aircraft that you are flying today has a 12 knot Cross Wind Limit (XWC). We will consider only winds up to 60-degrees OFF the runway (RW) Track:
0-degrees OFF RW = 0/6ths of Wind Strength
10-degrees OFF RW = 1/6th of Wind Strength
20 = 2/6
30 = 3/6.......etc to >>>> 60 = 6/6ths of Wind Strength

Example 1: If the Runway is RW23 [(say) 233-deg Magnetic = 230-deg True (Var 3-deg West)], and the Wind Vector is 260/22 i.e. 30-degrees OFF, then the XWC is 3/6 X 22 = 11kts.

Example 2: If the Runway is RW35 [(say) 348-deg Magnetic = 351-deg True (Var 3-deg West)], and the Wind Vector is 310/18 i.e. 40-degrees OFF, then the XWC is 4/6 X 18 = 12kts.

I think that is the MAX DRIFT & XWC dealt with!

Friday, 29 August 2008

Thursday, 28 August 2008

PPL Ex 18 (ix): NAVIGATION: (Work-in-Progress)

Of course, the GPS is a legitimate aid to navigaion. USE ALL MEANS to navigate safely. Keep SITUATION AWARENESS going by understanding and practising the basics - TRACK & GS, DRIFT & HEADING, XWC, HWC, TWC etc.

Here are some extracts from GASCo Flight Safety Vol.44 No.3 autumn 2008:

This website is very much work-in-progress. Standby for further Practical Navigation and other exercises here soon.

Wednesday, 27 August 2008


Colonel Don Blakeslee - He led the 4th Fighter Group across Germany and Eastern Europe using only a map on his kneee and a watch. (See the Daily Telegraph report below.)

These are the main pointers:
  • Plan the route meticulously.

  • Check for gross errors.

  • Keep the markings on your route to a sensible minimum (K.I.S.).

  • 6 minute marks, or ½ and ¼ and ¾ marks, or time marks at major features.

  • Possibly mark the Track and Distance at the start point of each leg.

  • Consider marking the wind direction and speed in green.

  • Mentally note the major geographical features on the route.

  • Mentally note the ATZs, MATZs, CTRs, CTZs, AIAAs, Restricted Areas and Danger Areas on your route – or make notes on your Navigation Log + Radio Frequencies.

  • Brakes OFF – Airborne – Landed – Brakes ON spaces are useful on the Nav Log.
BUT KEEP IT SIMPLE! The normal priorities always apply and this includes Pilot Navigation. Aviate – Navigate – Communicate.
Make every effort to be organised in the cockpit. Do not spend more time than is absolutely necessary looking at your chart. LOOKOUT is absolutely important and the rule Lookout – Attitude – Instruments applies here as it does in all regimes of flight.

Accurate Pilot Navigation is dependent on two main factors:
These are:
Have faith in your meticulous planning. Have faith in the met winds and temperature. Clock and Heading will get you there.
(About a hundred years ago I used to fly twin-piston aircraft over the South African bush. Clock and Heading over large distances always worked.)
CHRONO: At TAKE-OFF start the CHRONO and anticipate each TURNING POINT. ZERO the Chrono a few seconds before the T.P. and START the Chrono exactly overhead the TURNING POINT.
HEADING: Concentrate on maintaining the HEADING accurately. This is best achieved by utilising a ground feature in the ‘far’ distance as an aiming point which lines up with your heading. Lookout – Attitude – Instruments. DO NOT FLY WITH YOUR EYES ‘INSIDE’.
Part of the Daily Telegraph obituary of Colonel Don Blakeslee - printed Saturday 27th September 2008

PPL Ex 18 (vii): NAVIGATION: The Navigation Log, HDG(M), GS

On the WIND SIDE of the computer: (Please see Blog: “The Dead Reckoning Computer” or “Wizz Wheel”). From TAS and the WIND VELOCITY applied to TRK˚T we can calculate TRUE HEADING (HDG˚T). The HEADWIND or TAILWIND COMPONENT for each ‘leg’ is also graphically displayed on the plotting surface of the computer. Therefore the GROUNDSPEED (GS) is easily calculated by adding or subtracting the component to/from the TAS.
Applying VARIATION to TRUE HEADING will give us MAGNETIC HEADING (HDG˚M) and applying DEVIATION to MAGNETIC HEADING will give us COMPASS HEADING. (Note 1: VARIATION EAST, MAGNETIC LEAST. DEVIATION EAST, COMPASS LEAST. Note 2: ISOGONALS are lines of equal variation and are printed as pecked lines on the Aeronautical Chart. Note 3: A COMPASS CARD is displayed in the aircraft which gives a COMPASS HEADING to steer based on a MAGNETIC HEADING.)

From - To - TAS - TRK(T) - W/V - HDG(T) - VAR - HDG(M):
Shipdam Alconbury 97.5 - 250 - 280/25 - 257 - 3˚W - 260
Alconbury MeltonM 97.5 - 315 - 280/25 - 307 - 3˚W - 310
MeltonM Shepshed 97.5 - 280 - 280/25 - 280 - 3˚W - 283

From - To - GS - Dist - Time - Fuel Rqd - ETA:
Shipdam Alconbury 76 - 44.5 - 35.2 - 2.94 - +35
Alconbury MeltonM 75 - 33.0 - 26.4 - 2.20 - +51
MeltonM Shepshed 72 - 14.0 - 11.7 - 0.98 - +63

Please read Blog: August "Navigation Ex 18 - Legend”

PPL Ex 18 (vi): NAVIGATION: (Winds and Temperature Aloft)

Let us assume that we are flying a Cessna 152 from Shipdam via Alconbury (See ICAO Chart below, click to enlarge!), Melton Mowbray and Shepshed E/E to East Midlands. (See LASORS SAFETY SENSE 22!) and the Met Office: Aviation – F214, 0900 to 1500 UTC via gives the forecast winds:

5230N 0230W
24 270 35 -29
18 280 25 -17
10 280 20 -01
05 280 25 +08
02 280 25 +10
01 270 20 +14

The two givens when planning a route are: True Track (TRK˚T), measured, and Wind Velocity downloaded. The TAS is calculated based on the known Indicated Cruising Speed at the planned altitude. The Cessna 152, which we are using as an example for these briefings, cruises at 90KIAS. The third value that we require for navigation planning is TAS.
Let us assume that our flight is planned at 5000ft AMSL. From the table above: The winds are 280/25 and the temperature is +08.
Using the AIR SPEED window on the computer and aligning 5000ft with +08, the DENSITY ALTITUDE is 5300ft and 90kts RAS = 97.5kts TAS.

Click on any image to ENLARGE!

PPL Ex18 (v)[Page3]: NAVIGATION: (True Air Speed -TAS Page 3)

The Standard Atmosphere is defined as follows:
  1. The air is a dry perfect gas
  2. The temperature at sea level is 15˚C
  3. The pressure at sea level is 1013.25 millibars
  4. The temperature gradient from 5,000m below sea level to an altitude at which the air temperature becomes -56.5˚C is -0.0065˚C per metre (approx. -1.98˚C/1000ft)
  5. The density ρ0 at sea level under the above conditions is 0.002378 slug/ft3 (or 1.225kg/m3)
Now observe the DENSITY ALTITUDE window. The DENSITY ALTITUDE is 0. So, at zero feet density altitude RAS = TAS. At 5,000ft DENSITY ALTITUDE you will notice that the temperature is +5˚C in the AIR SPEED window at 5,000 Pressure Altitude, and the 90 on the R.A.S. scale is now opposite 97 on the T.A.S. scale. So, in a standard atmosphere, 90kts R.A.S. at 5000ft AMSL = 97Kts T.A.S. At 2000ft Density Altitude 90kts R.A.S. = 92.7Kts T.A.S.

Note: If the temperature is not standard for the altitude then use the AIR SPEED window to align the C.O.A.T. against the PRESSURE ALTITUDE. E.g. if the temperature at 5000ft is not the standard +5˚C but (say) +20˚C (ISA+15 see iv. above - Standard Atmosphere) the T.A.S. will be 99.5kts. The higher the temperature the higher will be the T.A.S because the Density is lower at that altitude. +20˚C at 5000ft altitude equates to a ‘Density Altitude’ of 6800ft. Conversely -20˚C at 5000ft altitude equates to a ‘Density Altitude’ of 1950ft.

Here is a definition of DENSITY ALTITUDE: The altitude in the Standard Atmosphere corresponding to the flight level density. Basically it is the measure of the number of molecules of air per cubic metre which can act upon the aircraft surfaces with the resulting forces of lift, drag etc. Density of a gas is determined by pressure and temperature. Density Altitude is the theoretical density of a standard atmosphere at that altitude. Aircraft performance is directly related to air density; therefore, performance is determined by DENSITY ALTITUDE regardless of the actual altitude.OK – that is TAS out of the way!

PPL Ex 18 (v)[Page 2]: NAVIGATION: (True Air Speed -TAS Page 2)

On the ‘front face’ of your navigation computer (the TIME – SPEED – DISTANCE side) you will see that (T.A.S.) is on the outer scale and (R.A.S.) is on the inner scale. Match up any two like numbers on these scales, say, 90 against 90. I.e. 90 TAS against 90 RAS. Now observe the AIR SPEED window on the inner part of the face. (This window should give you Press. Alt x 1000ft against C.O.A.T ˚C.) Find 0 Pressure Altitude and note the C.O.A.T. This is +15˚C. (At standard atmosphere* temperature of +15˚C RAS =TAS.)

Now, follow the 'arrow' to the 'Density Altitude' window. read the DENSITY ALTITUDE is (0x1000 ft) ZERO.

Note: ISA - International Standard Atmosphere is on the next page.........
GO TO PPL Ex18 (v)[Page3]>>>>>>>>>>>>>>

PPL Ex 18 (v): NAVIGATION: (True Air Speed -TAS Page 1)

Firstly: a) Indicated Air Speed (IAS) is the reading of a particular air speed indicator & b) Rectified Air Speed (RAS) or Calibrated Air Speed (CAS) is the indicated airspeed corrected for instrument and installation errors & c) Equivalent Air Speed (EAS) is equal to the air speed indicator reading corrected for position error, instrument error and for adiabatic compressible flow for the particular altitude. (EAS is equal to RAS at sea level in standard atmosphere.)
True Air Speed (TAS) is the air speed relative to the surrounding air undisturbed by the aircraft’s motion. It is determined from the RAS (UK) or CAS (USA) by applying a correction for the density error and – at higher speeds – for the effects of compressibility. The density error is caused by deviation of the flight level pressure and temperature from the standard sea level values upon which the calibration of air speed indicators is based.
GO TO PPL Ex 18 (v)[Page 2] for page 2 of TAS>>>>>>

PPL Ex 18 (iv): NAVIGATION: (Measuring the Track Page 2)

Remember: Click to enlarge!

Having measured the track angle it is now necessary to measure the track distance. The 1:500,000 ICAO Aeronautical Chart is a Lambert Conformal Conic Mercator Chart. The lines of Latitude are at ½ ˚ (30nm) intervals. Each 1˚ is equal to 60nm. Do not measure your track distance along the lines of Latitude. The lines of Longitude are also at ½˚ intervals. The distance must be measured along a line of Longitude (i.e. vertically). E.g. even if your track line is (say) 090˚(T), the distance of the track line must be measured using a North/South graticule line. If you observe these lines closely it will be apparent that each 1 degree of latitude is 60nm with small marks to one side (the west side) of the line at each 1nm, with slightly larger marks at each 5nm and a cross line at each 10nm. Of course, provided that you use a ruler of the correct scale you can also measure the distance in this manner. In the illustration you may notice that I have attached a small dayglo arrow on the ruler pointing to the 1:500,000 scale (as this is the scale of chart that I always use), and a dayglo arrow at the North (360˚) mark on my Douglas Protractor. These are time-saving devices! Having measured the Tracks (˚T) and Distances (nm) we now write them down on the Navigation Log for each ‘leg’ of the route. On inspecting a typical Nav Log you will notice that there can be 14 or more columns! Don’t worry – the whole process of figuring out your navigation plan is quite logical. Before proceeding any further, however, I believe that it would be a good idea to explain TRUE AIR SPEED or TAS, because TAS features early in these columns. Ignore the blue writing if you already know all this stuff!

PPL Ex 18 (iv): NAVIGATION: (Measuring the Track Page 1)

This exercise follows on from the ‘briefing’ for “The Dead Reckoning Computer or Wizz Wheel”.
Remember: Click on an image to enlarge!

In this ‘briefing’ it should suffice to remind you that with the air navigation charts that we use the angles are correctly represented. The most useful chart to use is AERONAUTICAL CHART ICAO 1:500,000. It is possible to use an ordinary protractor for measuring angles (i.e. tracks) and a chart with these properties is called ORTHOMORPHIC. A desirable property of the chart is that it should be constant scale so that you can use an ordinary scale rule to measure distance. The chart presupposes a scale model of the Earth called the reduced earth on which is drawn the required details of the Earth – coastlines, railways, rivers, roads etc, and also a graticule of latitude and longitude. The graticule is made up of a series of circular lines on the sphere, but, of course, parallel lines on the chart; the lines of longitude are called MERIDIANS and join the geographic poles. The PRIME MERIDIAN joins the North Pole to Greenwich and to the South Pole. All meridians are GREAT CIRCLES and are labelled East or West. The equator is at right angles to the axis of the Earth, the lines of latitude are circles on the Earth whose plane is parallel to the equator; they are therefore small circles and are named North or South.
Assuming the Earth to be a true sphere, a nautical mile is defined as the length of arc of a great circle which subtends an angle of one minute at the centre of the Earth. This is the reason that the Airspeed Indicator (ASI) is graduated in nautical miles per hour i.e. Knots. (Sorry; I know that YOU know that!)
OK, so we have resolved the little matter of representing a spherical Earth on a flat chart. Now it is essential to understand how to measure a True Track [TRK(T)] on an Aeronautical Chart using a Douglas (square) Protractor. Accurately place the centre crosshairs of the protractor somewhere on the track that you have drawn, ensuring that the North (360˚) mark is at the top (where North is, of course) and in such a position that the track line extends beyond the side of the protractor. Now adjust the protractor so that the vertical lines of the protractor align exactly with the North/South graticule lines keeping the centre of the protractor exactly on the measured track line. It is now possible to read the True Track [TRK(T)] in the direction that you intend to fly. Note: The direction is measured clockwise around the edge of the protractor from 000˚N through 090˚E, 180˚S, 270˚W and 360˚ (000˚) N. In the picture above: 250-degrees True.

PPL Ex 18 (iii): NAVIGATION: (The Douglas Protractor Page 2)

PPL Ex 18 (iii): NAVIGATION: (The Douglas Protractor Page 1) [Click image to enlarge]

PPL Ex 18 (ii): Navigation: (Legend Page 3)

PPL Ex 18 (ii): Navigation: (Legend Page 2)

PPL Ex 18 (ii): NAVIGATION: (Legend Page 1)

Before starting to use the ICAO Aeronautical Chart 1:500,000 here is the LEGEND. i It may be a good idea to copy the legend into an A5 ClearView Folder. Why not make a Handy Dandy by using an A5 size ClearView folder?
Note: Click on a LEGEND image to enlarge.







From Flight Safety BULLETIN Vol.XXXV No.2 Summer 1999 - Journal of the General Aviation Safety Council. An article by John Stewart-Smith.
(Click on an image to ENLARGE.)

Tuesday, 26 August 2008

Correct R/T Phraseology? Any Feedback?

CAP413 1.5.2 and 1.13.3 (Click here) and LASORS Safety Sense 22 p.13 (Click here) give conflicting information regarding requests to an ATSU for Flight Information Service or Radar Information Service or MATZ Penetration or Zone Transit or whatever. This is the latest information. According to the latest Seminar the following is the correct format for these types of messages:
  • AIRCRAFT: Station address - Callsign - Request.
  • ATSU: Callsign - "Pass your message."
  • AIRCRAFT: Callsign - Type - Point of departure - Destination - Routing -Position - Altitude - Request.
  • Note 1: Heading is not required. VFR/IFR not required. Pressure setting not required.
  • Note 2: If your initial request is for (say) a “MATZ penetration” then the ATSU require, in the subsequent request, the type of service through their MATZ or in their Airspace e.g. “Radar Information Service”.

(Click on the image to ENLARGE.)

A Visitor from DURBAN

A new friend, from Durban, recently came flying with me in a Beagle Pup 150.
He owns and flies his own Cessna Citation from Virginia Airport KZN - standby for some pictures soon.
We flew over many of the spectacular sights of the Peak District.
This little aircraft is a pleasure to fly with excellent handling characteristics. The visibility is also very good. We both enjoyed the flight.
(Click on the image to ENLARGE.)


The AIM: As the site develops, to 'brief' and offer practical advice re many of the PPL Flight Exercises. To offer advice regarding safe operation & procedure, correct prioritisation, good practice and, where appropriate, to add useful information & highlight common errors. Also, via 'Comments' to answer questions and give feedback.
There will be other items of interest e.g. who has recently flown their First Solo and any other relevant information.
Hopefully this site will generate interest and participation - ANYONE may participate.
No warranty or claims are made or implied regarding the accuracy or worthiness of the information included or linked to via this web site. We are doing the best we can to ensure accurate information, however, the actual data may not be accurate, up-to-date, or it may be faulty to begin with (If you find inaccuracies please let us know). Use these sources at your own risk. The CAA is the primary authority.

PPL Ex 12: Take-off and Climb to Downwind

Short Field Take-off: (Based on Cessna 152): Organise the turn onto the runway (Tip: Windsock 'points' towards runway take-off end) so that the line-up on the centre-line of the runway is with the nosewheel straight and maximum runway ahead of the aircraft. A rolling take-off is the most efficient, but at these early stages stop the aircraft and hold it stationary on the brake pedals, check the engine Ts and Ps and re-check the CARB HEAT, ignition at BOTH and FLAP 10-deg. Check the wind direction and now put the control wheel (aileron) into the wind by an amount relative to the wind direction and strength. (Tip: Mentally note the wind direction for two good reasons: 1. How much drift angle to apply for the heading after take-off, and 2. Forced landing after take-off = land ahead within 30-degrees of wind direction). Apply full power against the brakes and re-check the Ts and Ps and the RPM. Release the brakes and keep straight using coarse rudder initially. Your focus of attention is now at the far end of the runway (peripheral vision is also giving your brain vital information, as always) and your attention is also on the Airspeed Indicator (ASI). Of course the Ts and Ps are always important. As the aircraft accelerates less rudder and aileron input will be required due to the airspeed effect on the control surfaces (ailerons and rudder). Quite early in the take-off run you will have effective elevator authority which will enable you to apply enough back pressure to raise the nosewheel just off the ground. At 50 knots indicated airspeed (KIAS) 'rotate' (i.e. back pressure on the control wheel) to the correct attitude for a short field take-off and simultaneously apply a degree of right rudder (slipstream effect remember? - Note: The rudder has a different function in flight to the function on the ground).

As the aircraft translates into the air the controls must now be pressured to balanced and wings level climbing flight. Rule: Lookout - Attitude - Instruments. IF the required attitude is not exactly right having applied the principles of: lookout, adopted an attitude and checked the flight instruments (instruments = the ASI at this point for the correct short field take-off speed of 54KIAS at 10-deg flap), THEN change the attitude gently to achieve the correct IAS. Check the heading (HDG) on the Direction Indicator (DI) and adjust to the correct HDG which = runway track (TRK) + or - drift angle. (Tip: Maximum Drift = 60/TAS X WS). The TAS will approximate indicated airspeed (KIAS) which is approximately 60KIAS (54KIAS actually). Let's assume that the windspeed is 12kts, so the maximum drift will be 60/60 X 12 = 12-degrees if the cross-wind is at 90-degrees to the runway. (Tip: Drift Angle: For each 10-degrees off of the runway, up to 60-degrees, use 1/6th of the maximum drift. So if the wind is 10-degrees off the runway use 1/6 of 12-degrees = 2-degrees of drift, 20-degrees off the runway = 2/6 of 12-degrees = 4 degrees etc, up to 60-degrees off the runway = 6/6 of 12-degrees = 12-degrees of drift). This approximation is also useful for dead-reckoning navigation. More under Exercise 18 later! Having achieved the correct attitude the important action now is to TRIM. Remember Power - Attitude - Trim. You have full power and the correct attitude for the required speed so now TRIM. Applying the principle of LOOKOUT - ATTITUDE - INSTRUMENTS maintain the climb straight ahead until a minimum of 300ft above airport level (AAL). [Note 1: QFE set on altimeter subscale = altimeter reads Height above aiport level. QNH set on altimeter subscale = altimeter reads Altitude above mean sea-level (AMSL) = add airport elevation to 300ft. Note 2: Here is an extract from GASIL Issue No.3 of 2008 with regards to the climb speed after obstacles are no longer an issue. Click to ENLARGE.] When the aircraft is above 300ft AAL lower the nose by a small amount to allow the aircraft to accelerate slowly. When the ASI reads 60KIAS minimum raise the flap to zero-degrees, i.e FLAPS UP and re-adjust the attitude for a 65KIAS climb (CLB). Again, Power - Attitude - Trim. The power has not changed, but the attitude has and so has the configuration (Flaps 10 to Flaps ZERO). Attitude flying and correct trimming are the answer to accurate and efficient flight. Do not chase the instruments, but LOOKOUT and use the visual horizon to adopt the correct ATTITUDE. Only when the attitude, speed and the power are stabilised do you TRIM. Do not 'trim' the aircraft into the attitude - this is a COMMON ERROR and useless! Roll the aircraft into a 15-degree angle of bank climbing turn. Keep the aircraft balanced by maintaing the BALL in the middle and adopt a slightly lower pitch attitude in order to maintain the correct cimbing speed of 65KIAS (67KIAS @ S.L. reducing to 61KIAS @ 10,000ft AMSL). Do not trim for the turn, but anticipate the rollout by approx 1/2 of the angle of bank (AoB). You know what the wind direction and strength is (approximately), so apply the drift angle using the max drift method to fly a correct crosswind HDG. Continue the CLB to circuit height (typically 1000ft AAL). Anticipate levelling off by 10% of the rate of climb (RoC) or vertical speed (VS). VS = 500FPM = 50ft anticipation. Make a level 30-deg angle of bank turn onto the downwind track. Leave the power at full power until the aircraft reaches cruise speed (CRZ SPD) of 90KIAS. As the aircraft accelerates towards CRZ SPD progressively and gently pitch down - Progressively Adjust Attitude - until the IAS and the altitude (ALT) have stabilised. Now reduce the power gently to CRZ POWER of 2150RPM. ATTITUDE - POWER - TRIM. (HDG = TRK +/- Drift Angle. Now TAS will stabilise at approximately 90KIAS, so max drift will be 60/90 X WS). Fly Straight & Level downwind.


No pilot ever forgets his first solo flight. Chaka the dog came along too to congratulate his master on a milestone achievement. Onwards and upwards........................

PPL: Ex 18 (i): NAVIGATION: The Dalton "Dead Reckoning Computer" OR Wizz Wheel Ex 18

I am often asked the question, "Should I use the 'wind UP' or the 'wind DOWN' method when solving the problem of finding Heading and Groundspeed on the "Dalton" navigation computer? Personally I use a Jeppesen CR-5 Computer which solves the wind triangle trigonometrically and you can put the CR5 in your shirt pocket. I also have a beautiful AristoAviat 617 which has a rotary indicator for the wind. Both of these instruments are EXCELLENT for accuracy. I am attaching the R.A.F. teaching (at least it was the teaching when I was in the air force a long time ago) which should clarify any queries you may have. Nothing has changed since then, but do also study the USER MANUAL that comes with your flight navigation computer. The important facts to remember are: HEADING (HDG) is on the same vector as TRUE AIRSPEED (TAS) and TRACK (TRK) is on the same vector as GROUNDSPEED (GS). Like oil and water, they do not mix. The conventional PPL navigation problem is to find HEADING and GROUNDSPEED. You have measured the TRACK and you have downloaded the WINDS for your planned flight from the Met Office (Click here for the Met Office weather & winds). So you know the track and you know the wind. We will have to assume that you also know the True Airspeed. TAS will be addressed later (see Ex 18 (v)). Paragraph 12 of the R.A.F. Notes addresses the problem of finding the HEADING and the GROUNDSPEED neatly (although you will note the TAS is 350kts - those were the days!! not a mere 90!!), but please read everything up to, and including Paragraph 12. Click on any image to ENLARGE.