What does Mmo stand for and when does it become the controlling limit?

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Multiple Choice

What does Mmo stand for and when does it become the controlling limit?

Mmo stands for the maximum operating Mach number—the highest Mach the aircraft is certified to operate at in normal flight. It’s a Mach-limit, not a knots-based limit. This limit becomes the controlling constraint at higher altitudes because, as you climb, the indicated airspeed limit (the VMO in knots) tends to become less restrictive in terms of the actual airspeed you can fly, while the Mach limit stays fixed in Mach. When you reach the point where continuing to increase speed would push you past the local Mach limit, the Mach limit governs your top speed. In other words, below a certain altitude the speed is limited by VMO, but at higher altitudes the limiting factor shifts to MMO and you must not exceed that Mach number.

Mmo stands for the maximum operating Mach number—the highest Mach the aircraft is certified to operate at in normal flight. It’s a Mach-limit, not a knots-based limit.

This limit becomes the controlling constraint at higher altitudes because, as you climb, the indicated airspeed limit (the VMO in knots) tends to become less restrictive in terms of the actual airspeed you can fly, while the Mach limit stays fixed in Mach. When you reach the point where continuing to increase speed would push you past the local Mach limit, the Mach limit governs your top speed. In other words, below a certain altitude the speed is limited by VMO, but at higher altitudes the limiting factor shifts to MMO and you must not exceed that Mach number.

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