Originally Posted by
NormalAbnormal
One thing I've always wondered about the first one… What's the rule of thumb on the Mach vs. GS? Mach depends on temperature, so wouldn't you need to know the either the SAT, or the altitude (assuming ISA lapse rate)?
On the second one, wouldn't it depend upon where you're standing? Turbojet v. turbofan? If you're at the front of the engine, wouldn't you hear the compressors mostly. The sound is pretty directional as you move around a running engine.
Rule of thumb is Mach number = miles per minute. In this scenario, .6m would equal 6 miles per minute, or 360 kts. I also got 1802.5z. Thought I was losing it!