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Refer to figure.
Determine the TAS (kt) and Fuel Consumption (GPH) for an aeroplane flying at an altitude of 9 500 ft, QNH 995 hPa and ISA -15ºC.

The power setting is 2 300 RPM/MAP 25.

  • A
    TAS 178 kt, 14.5 GPH.
  • B
    TAS 179 kt, 13.1 GPH.
  • C
    TAS 182 kt, 14.5 GPH.
  • D
    TAS 184 kt, 15.2 GPH.
Refer to figure.
CALCULATE PRESSURE ALTITUDE:
On the table, TAS and Fuel consumption are dependent on Pressure Altitude. Therefore we must calculate the Pressure Altitude corresponding to an altitude of 9 500 ft at QNH 995:

1013 hPa - 995 hPa = 18 hPa
Assume 30 ft/hPa:
18 hpa x 30 ft/hPa = 540 ft
Pressure Altitude = 9500 ft + 540 ft = approx. 10 000 ft

FIND TAS AND FUEL CONSUMPTION
(TABLE):
Flying at a pressure altitude of 10 000 ft, we will have to use the values from the first table.


TAS and GPH at 10 000 ft and ISA -15ºC will have to be interpolated between the values for ISA -30ºC and ISA.

Enter the table at 2300 RPM and 25 MAP:
  • TAS
    ISA -30ºC = 183 kt
    ISA = 182 kt
    Therefore, for ISA -15ºC, TAS = (183 kt + 182 kt) / 2 = 182.5 kt
  • GPH
    ISA -30ºC = 14.9 gph
    ISA = 14.1 gph
    Therefore, for ISA -15ºC, GPH = (14.9 + 14.1) / 2 = 14.5 gph
Closest option: 182 kt, 14.5 GPH

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