True Air Speed (TAS) = 90kts.
Saturday, 30 August 2008
True Air Speed (TAS) = 90kts.
Friday, 29 August 2008
Thursday, 28 August 2008
Wednesday, 27 August 2008
- 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.
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:
· HEADING DISCIPLINE
· CHRONO DISCIPLINE
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’.
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”
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!
- The air is a dry perfect gas
- The temperature at sea level is 15˚C
- The pressure at sea level is 1013.25 millibars
- 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)
- The density ρ0 at sea level under the above conditions is 0.002378 slug/ft3 (or 1.225kg/m3)
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!
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>>>>>>
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!
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.
Tuesday, 26 August 2008
- 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.)
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.
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.