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-   -   Effects of warm air masses (https://www.pprune.org/tech-log/238660-effects-warm-air-masses.html)

katooie 12th Aug 2006 01:47

Effects of warm air masses
 
To all the smarties...

We (in a turbofan aircraft) fly into a region of warmer air. What are the effects on the flightpath and engine performance?

Is the following correct?

On the Engine side: Warmer air = less density = reduced thrust = EPR decrease?

On the flight side: For a given angle of attack lift will decrease so we need to increase thrust or we will descend?

Any thoughts?

Thanks

Clandestino 12th Aug 2006 21:37

Your asumptions are correct for plane flying with manual throttles (set at constant position, too) and autopilot engaged in AoA hold mode (nonexistant AFAIK).

In everyday operation planes are flown with autothrottles engaged and autopilot in alt hold mode, so moving from cold to warm airmass will produce slight pitch-up to increase AoA and compensate for lost lift and slight throttle-up to compensate for bit of extra drag and bit of thrust loss. However, those effects are far from signifficant.

katooie 12th Aug 2006 22:26

Hey Clandestino,
Thanks for your input. That makes sense.

Cheers


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