Wednesday, 27 August 2008

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!

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