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Zoyberg

2nd February 2009 07:02

737 NG optimum flight level reduction with reducing mach no.

Can someone explain how my 737 optimum altitude is calculated.

Yesterday I completed an automatic FMC max rate climb to meet an ATC restriction ... the speed came back to 230 knots/0.68 mach and approaching FL350 ....ISA -10...at 69,000 tonnes the FMC optimum calculation was around 3,000' lower ( I would typically expect FL380 @ 0.78 mach in these conditions).

Thought this would be the only place to get a scientific answer,

Thanks in advance.

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