| Earn your PPL and join the big tin at the airport of your choice. Have the freedom to drop in and impress your mates. However, you do need to know radio procedures in coltrolled airspace. So learn this part really well Soon you will be flying the big tin for a living. |
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| GROUNDSPEED TIPS Although we can use a computer to calculate groundspeed, there will be times when it would be more convenient to calculate it mentally. Groundspped calculation is similar to the second stage of drift calculation. We will again use our watch to calculate the proportion of wind that will act as a head or tail wind. To calculate actual head or tail wind,we need to know the wind's angle off the beam position ( the angle off a line joining the wing tips) and we need an analogue watch. Take the angle off the beam in degrees and go around the watch that number of minutes (up to a maximum of 60 minutes). The fraction of the watch face that we have reached is the fraction of wind speed that is acting as a head ot tail wind. We can then add this to or subtract this from the TAS to give us groundspeed. For example: Heading: 360 deg. TAS: 180 kts Wind Velocity: 050 deg/15 kts Angle-off Beam = 40 deg. Fraction of Watch Face = 2/3 Head Wind: 10 kts. Groundspeed = 180 - 10 = 170 kts |
| TAS-IAS CONVERSION TUTORIAL The airspeed indicator (ASI) measures the dynamic pressure entering the pitot head. This dynamic pressure is used to give a reading of indicated airspeed (IAS). Minor correection for pressure (or position) error and instrument error can then be made to give rectified airspeed (RAS) and then the effects of compressibility can be calculated to give us equivalent airspeed (EAS). In a light aircraft at cruise speed we can consider IAS and EAS to be equal. However, EAS is still not the speed at which the aircraft is really moving because we have not considered the effect of air density. As we climb density reduces and so TAC will increase if we hold a constant IAS. We can use a computer to calculate this change; however, it is not always practical to get out our computer when flying on instrumetns. This turorial will look at 2 different ways to calculate TAS from IAS. RULE OF SQUARES This method, though a little complicated, produces very accurate results. It is best used when flight planning, if no computer avilable, and can be summed up by the following table. HIEGHT FACTOR TAS= 5000 ft3 2sq.=9 IAS + 9% 10000 ft 4 2sq=16 IAS + 16% 15000 ft 5 2sq.=25 IAS + 25% 20000 ft 6 2sq.=36 IAS + 36% 25000 ft 7 2sq.=49 IAS + 49% 30000 ft 8 2sq.=64 IAS + 64% For example: IAS = 200 kts Height = 15000 ft TAS = 200 + 25% = 250 kts NEW IAS = IAS x (height change in thousands of feet x IAS in nms/minute) If you are climbing then IAS will decrease. If you are descending, then IAS will increase. For example: Planned IAS = 180 kts ATC requests a climb from FL50 to FL70 New IAS = 180 - 2 x (180/60) = 174 kts |
| DRIFT TUTORIAL Although we can use a computer to calculate drift, there will be times when it would be more convenient to calculate it mentally. Drift calculation is a two-stage process. First we will caclulate the maximum drift which is the drift caused by a wind at 90 degrees to our heading. Then we will modify this for the actual angel off of the wing. MAX DRIFT Max drift is easily calculated from this formula: Max Drift = Wind Speed / TAS in miles per minutes ACTUAL DRIFT To calculate actual drift, we need to know the wind's angle off the nose to tail and we need an analogue watch. Take the angle-off in degrees and go around the watch that number of minutes (up to a miximum of 60 minutes). The fraction of the watc face that we have reached is the fraction of maximum drift that we must apply. For example: Heading = 360 deg. TAS = 180 deg. Wind Velocity = 030 deg/15 kts Max Drift = 15 divided by (180/60) = 5 deg. Angle-off = 30 deg Fraction Of Watch Face = 1/2 Actual Drift = 2 1/2 deg. L |
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