What it is: On glass cockpits and some older-style indicators, this striped marker represents the overspeed limit at that moment rather than a fixed number. Its position changes with altitude, aircraft configuration and, in some types, the switch from structural speed limits to Mach limits.
In practice: During a simulated climb, cruise or descent, you use the barber pole as a visual boundary on the speed tape. If your indicated airspeed approaches it, you are getting close to overspeed, which can trigger warnings, autopilot disconnects, system damage in some add-ons, or simply unrealistic handling. At higher altitudes the limit often reduces in terms of indicated airspeed because the aircraft is nearing its Mach limit, so the barber pole can move down the tape even while the aircraft feels stable. When descending, configuration changes such as extending flaps or gear may also shift the limit sharply.
Key considerations:
- The barber pole is dynamic, so do not treat VMO or MMO as a single fixed speed throughout the flight.
- Watch for rapid movement after flap or gear extension, especially in faster descents.
- On modern jets, managed speed and VNAV modes usually keep clear of it, but manual flight can reach it quickly in thin air.
