Some flight guidance and control systems automatically switch from IAS to
Mach at a given Flight Level. Example would be the MD-80 DFGC. If the
IAS/Mach switch is pushed below FL 270 it shows and controls current IAS.
If the same switch is pushed above FL 270 is shows and controls current
Mach.

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B-58 Hustler History: http://members.cox.net/dschmidt1/
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"Mark Hewitt" wrote in message
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"Really Me" wrote in message
m...



At or above FL240, express speed (IAS) in Mach
Below FL 240, express speed in knots

Any reason?