Re: A340 speed

From:         Jim Innes <jinnes@direct.ca>
Organization: Canada Internet Direct, Inc.
Date:         20 Jul 96 15:56:08 
References:   1 2 3 4 5
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Once again there appears to be a great misunderstanding between the
relationship of Indicated Mach and TAS. Everyone seems to hang thier hats on
this thing called Mach No.'s. The real question is at what altitude are these
quotes from. If your cruising at .83 at FL310 standard day, your TAS is
anywhere form 490-495kts. If your cruising the Giant JetLiner at .85 at FL390
your TAS is probably the same or darn near it.

The 4 engine SKUD (A340) typically cruise at .82-.84 inorder to stay with
traffic flows over the ocean, both the NOPAC PACOTS and NAT system. For the
A340 to cruise at these speeds it's fuel economy (range) decrease greatly! The
aircraft must cruise at these higher speeds because it's optimum cruising
atlitudes are typically the same as the faster transports, the 744 and the MD
11.

We normally cruise the DC 10-30 long range at .82-.84, however it's optimum
cruising altitudes are typically FL310-FL350 no higher. Therefore your
effective TAS is really close to the aircraft flying higherand faster Mach's.