From: Jim Innes <email@example.com> 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.