What it is: Vmo is a structural and handling limit based on indicated airspeed rather than groundspeed or true airspeed. On many aircraft, especially airliners and faster turboprops, it appears alongside Mmo, with the limiting value changing by altitude and flight conditions.
In practice: During a simulated flight, you will normally see Vmo marked on the airspeed tape or analogue ASI with a red line or barber-pole. Exceeding it can trigger overspeed warnings, autopilot pitch changes, or aircraft damage in sims that model failures and structural limits. At lower altitudes, Vmo is often the speed ceiling you are managing against in descent or when levelling off after a rapid acceleration. As you climb, the limiting factor may shift from Vmo to Mmo, so the aircraft can reach its Mach limit before reaching the IAS limit.
Key considerations:
- Vmo is based on indicated airspeed, so a strong tailwind does not change the limit even if groundspeed is much higher.
- Fast descents, idle-power dives, and delayed speedbrake use are common ways sim pilots accidentally overspeed past Vmo.
- If the aircraft has both Vmo and Mmo, watch the barber-pole rather than relying on a single memorised number.
