Re: 747-400 Initial Cruise

Date:         01 Oct 97 14:08:46 
From:         "Michael F. Lechnar" <michael.f.lechnar@boeing.com>
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Andrew Cruickshank wrote:
> A few years ago a flew BA from KUL to LHR and the pilot's
> commentary over the PA stated cruise would be at 26,000 ft.
> I though this a bit low and stowed it away for future
> reference.
>
> Last week I did LHR to KUL with MAS and the pilot said
> we would be at 29,000 ft initially until we were lighter.
>
> This raises the question - is the cruise level of a 747-400
> with full load of passengers and cargo limited until fuel
> burn off occurs.
>
> Given that no specific climb was obvious (increase in
> engine noise or change in cabin pressure) then this also
> raises the question as to whether some of cruise-climb
> phase is used as fuel burns off.

At least in the case of the KUL-LHR flight, 26,000 ft was probably
assigned by ATC.  Indian ATC is particulary notorious for keeping
airplanes at low altitudes in their airspace.  The first flights out
generally get the highest altitudes.

The flight out of LHR was again probably limited by ATC rather than
airplane performance.  BA's 747-400s are capable of at least 31,000 ft
initial altitude capability at maximum certified takeoff weights

Mike Lechnar
Aircraft Performance Engineer
"If I was speaking for Boeing, I wouldn't be doing it here."