Description

Brake to vacate (BTV) is a system designed by Airbus to assist pilots with optimal use of brakes so that the aircraft reaches the desired runway exit at an appropriate speed for vacating.

Optimal braking is crucial for minimizing the runway occupancy time (which, in turn, translates into increased capacity and reduced delays). If the aircraft slows down too early (i.e. between two exits), it may need to move at taxi speed for a considerable period of time until the desired exit is reached. If braking is insufficient, the exit may be missed, which in some cases may lead to the need of backtracking to vacate. Either scenario leads to reduced efficiency. The situation is aggravated in low visibility conditions where the next exit may not be visible from the cockpit.

Most modern airliners are equipped with an autobrake system that automates brake application based on a selection made by the pilot. This is intended to reduce pilot workload in a demanding situation, such as a landing or a rejected take off. Depending on the aircraft, it has several available settings (e.g. LO/MED, LO/2/3/4/HI, RTO/1/2/3/MAX, etc.). These are entirely aircraft-based and do not take account of the aerodrome layout. While the pilot will normally choose the most appropriate mode in respect to the landing conditions and the desired runway exit, it is likely that in many cases autobrake override will be necessary.

The BTV system uses GPS data to determine (and update) aircraft position and aerodrome data (location of exits) in order to calculate the necessary brake pressure to be applied. The desired runway exit is selected by the pilot during the approach phase based on a number of factors (expected taxi route, controller instructions, etc.). After that, calculation and application of brakes is automated.

The benefits of BTV include:

• Reduced runway occupancy time. This, in turn, increases the runway (and hence, aerodrome) capacity.
• Reduced pilot workload. This allows the crew to focus on other matters in a high-workload situation.
• Optimal use of brakes which reduces wear and increases passenger comfort (fewer pilot interventions are necessary).
• Greatly reduced (almost eliminated) risk of missed exit situations.

The BTV system is installed on the A380 (2009), the A320 Family (2012/2013) and as an option and on A350XWB.

Related Articles

• Deceleration on the Runway
• Runway Overrun Prevention System (ROPS)
• Runway Awareness and Advisory System (RAAS)

Further Reading

• Brake-to-Vacate System, an article in FAST Magazine (issue 44, July 2009)