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Refer to the extract below from an Operational Flight Plan (OFP). What is the average TAS over the given route segments?

Leg

TAS

t (min)

1

216

22

2

228

17

3

221

13

4

224

16

5

224

8

  • A

    224 kt

  • B

    223 kt

  • C

    221 kt

  • D

    222 kt

We are asked to calculate the average speed over all of the segments. In essence:

  • Average TAS = Total Distance / Total Time

So by calculating the total distance for each leg and total time we can calculate the average TAS:

LEG

TAS (kt)

t (min)

Distance (NM)

1

216

22

79.2

2

228

17

64.6

3

221

13

47.9

4

224

16

59.7

5

224

8

29.9

76 min

281.3NM

Average TAS = 281.3 / (76/60) = 222 kt

Note: For those who are comfortable with it, to save time, you can "skip" the step of calculating each of the distances individually, by entering the entire equation into your scientific calculator as follows:

  • ((216 x 22) + (228 x 17) + (221 x 13) + (224 x 16) + (224 x 8)) / (22 + 17 + 13 + 16 + 8)

This also saves the need to calculate the distance in NM by dividing the minutes by 60, etc..

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