Re: 767 Service Ceiling

From: (Morten Norby Larsen)
Date:         11 Aug 94 02:18:14 
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In article <airliners.1994.1490@ohare.Chicago.COM>,
(Terrell D. Drinkard) writes:

>Interestingly, service ceiling is a light aircraft type of parameter.  It
>is fairly meaningless for heavy commercial airplanes.  The cruise altitude
>is generally pretty close to optimum cruise altitude at any given stage of
>the flight.  This is an economic issue as it is pretty costly to fly off
>optimum.  The 500 fpm climb rate line is generally well above the optimum
>cruise altitude, and service ceiling is defined as the altitude where the
>rate of climb is 100 fpm.  The lowest climb parameter I've seen is 300 fpm,
>and that is well above even the 500 fpm line.

Sorry to interrupt an interesting discussion... But I don't understand 
anything: How can 300fpm be well above 500fpm? Or to put it another way: 
What is the XXX fpm line? 

I would buy a beer for any aircraft designer that would come by my local
waterhole and explain it! 

In ordinary flight they seem not to get very high very often:
I was riding in the jump seat of a 767 with 4 PAX on a long-haul
flight. We set out at 39000ft and climbed half-way to 43000ft. The
first officer had never been so high before and the captain was there
for only the second time. However, the question was not as much when
they had to climb there, but when they could justify it...

Morten Norby Larsen                              e-mail:
Joint Research Centre, Ispra, Italy              Phone:  +39 332 78 92 18
Institute for System Engineering and Informatics Fax: +39 332 78 58 13