Bubbers,I can't remember all the physics behind it but back in my 707 days cruising @ M.81 the formula used to X check or in case of Machmeter failure was:SAT+TAS=521(?) at any altitude.I'm pretty sure it was 521 but it was a while ago and it worked spot on every time.
Last edited by 30/30 Green Light; 18th May 2006 at 06:42.