Auto-Throttle Speed Protection (ASP)

James Albright

Updated: 2020-07-15

Note: the following sentences come directly from the cited AOM pages, but have been reordered for readability.

What is it?

[G500 Ground and Flight Operations, p. 107] The Auto-Throttle Speed Protection (ASP) function uses Auto-Throttle auto-engagement and selective airspeed targeting to prevent excursions outside of the normal aircraft speed envelope. ASP includes both static and dynamic speed protection functions.

[G500 Ground and Flight Operations, p. 99] The Auto-Throttle system has a speed protection mode to automatically engage the Auto-Throttles to prevent underspeed. The Auto-Throttle Speed Protection (ASP) system will target the higher of the guidance panel (GP) speed target or Auto-Throttle (VMIN), which is calculated as 1 knot above the LSA airspeed. ASP activation is annunciated to the pilot as "VMIN" on the Auto-Throttle (or Performance) FMA.

[G500 Ground and Flight Operations, p. 107] Auto-Throttle Speed Protect (ASP), when engaged during a high-speed excursion, initially targets a speed inside the speed envelope (VMO) and then will subsequently target the speed set in GP speed window.

Static ASP

[G500 Ground and Flight Operations, p. 100] The static underspeed threshold is set to be coincident with the LSA airspeed, preventing airspeed excursions outside of the envelope that may develop slowly over time. Static underspeed protection will activate when the current underspeed threshold has been exceeded without activating the dynamic ASP function.

[G500 Ground and Flight Operations, p. 100] Static overspeed protection will activate when the current overspeed threshold has been exceeded without activating the dynamic ASP function.

Dynamic ASP

[G500 Ground and Flight Operations, p. 100] For dynamic underspeed protection, the ASP function uses a filtered CAS rate and the current CAS to determine if the aircraft will underspeed in the next 6.5 seconds. The dynamic underspeed threshold is determined by predicting if the aircraft's Calibrated Airspeed in the next 6.5 seconds will hit or the amber or red bars on the airspeed tape. The dynamic underspeed threshold is defined as 30% below the top of the amber bar. For example, if LSA was 119 and Vshaker was 104, the dynamic underspeed threshold would be 114.5 knots.

[G500 Ground and Flight Operations, p. 107] For dynamic overspeed protection (aircraft accelerating towards the limit), the ASP logic uses a filtered Calibrated Airspeed (CAS) rate and the current CAS to determine if the aircraft will overspeed within the next 2.5 seconds.