Help: Calculating Mach number
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Join Date: Apr 2011
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Help: Calculating Mach number
Hi all,
- Using the LSS formula a = 39 √ T and..
- Mach number (M) = Speed of aircraft (TAS) ÷ Local speed of sound (a)
What is the Mach number of an aircraft doing 453 knots groundspeed, with a 58 knot headwind component, cruising at FL380, at ISA plus 5 degrees Celsius?
Appreciate if the workings can be illustrated. Thank you all.
- Using the LSS formula a = 39 √ T and..
- Mach number (M) = Speed of aircraft (TAS) ÷ Local speed of sound (a)
What is the Mach number of an aircraft doing 453 knots groundspeed, with a 58 knot headwind component, cruising at FL380, at ISA plus 5 degrees Celsius?
Appreciate if the workings can be illustrated. Thank you all.
Join Date: Mar 2014
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Temperature drops 1.98°C every 1000ft up to FL360 where it remains constant at -56,5°C.
FL380 at ISA + 5° means -56,5+5=-51,5°C
Headwind means that groundspeed will be lower than TAS, so TAS will be 453+58=511kts.
You have what you need. Remember to convert °C in K before using the temperature in the LSS formula.
FL380 at ISA + 5° means -56,5+5=-51,5°C
Headwind means that groundspeed will be lower than TAS, so TAS will be 453+58=511kts.
You have what you need. Remember to convert °C in K before using the temperature in the LSS formula.
