Calculating Density Height & TAS from Pressure Height

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Calculating Density Height & TAS from Pressure Height

Post  Admin on Tue Dec 01, 2009 6:56 am

ALT – 2119 ft
QNH – 998
TEMP - +24c
AE – 2119 ft
IAS – 115 Knots
CAS – 111knots

• Calc Pressure Height
PH = (ISA 1013.994 hPa – 998hPa) x 30 feet + AE
= +479.82 ft + AE
= +479.82 ft + 2119 ft
= 2598.98 ft PH (say 2600 ft)

• Calc Density Height
DH = +15c – (ISA 2 x 2.5)
= + 10c
Var = +5c
= +5c x 120 ft
= +600 ft + 2598.98 ft
= 3198 ft DH (say 3200 ft)

• Calc TAS
TAS = DH in 1000’s x 1.5 = % increase over IAS
= 3.2 x 1.5
= CSA + 4.8%
= 111+4.8%
= 125.8 (say 126) KTAS

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