Yes that’s an interesting point. They do look like Mmo (maximum operating Mach number) rather than a normal cruising speed. The reason I think this is interesting is that this speed is often faster uf the aircraft is FAA registered than JAA registered. For example, JMC would put a couple of 757’s on the FAA register for winter operations in the US. At these times the Mmo went up from the JAA figure of M0.84 to M0.86
The reason the FAA speeds are faster is they way they calcuate Mmo for a given type.The FAA require a margin of 0.05M between Md (design limit dive speed) and Mc (design cruise speed). Whereas the CAA require the margin between Md and Mc be sufficient to cope with a head on gust of 45ft/sec at Vmo/Mmo which equates to 0.07M
In the case of the 757/767 Md is 0.91M so 0.91-0.05=0.86M under FAA rulings and 0.91-0.07=0.84M under CAA.
Shall I get my coat? Too warm for a coat. It’ll have to be an anorak.
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