Can anyone comment on the following document that was given to me? It seems to relate a serious safety concern and I wonder if those of you in industry share the concern.
Public Interest Issue
ACARs is an automated system for monitoring and reporting airline on-time performance, introduced in 1988 and used internationally – by more than 120 companies. Airlines apply intense pressure to their own staff to achieve good ratings, and as a consequence it has apparently become common practice to use certain ‘tricks’ to fool the ACARs system into reporting better on-time performance. These practices violate aviation safety regulations, create safety significant risks to passengers and staff, and create a climate of disrespect for other safety regulations – the beginning of a very dangerous ‘slippery slope’ for commercial aviation safety.
The ‘tricks’
ACARs detects that a flight has begun when all doors are closed and the aircraft parking brake is released. The system can be fooled by releasing the parking brake early before the aircraft is ready to push back, thus signalling a false departure time.
ACARs detects that a flight has ended when any door is opened and the parking brake is applied. For safety reasons, doors are supposed to be opened only after all engines are shut down and the aircraft is safe to approach. The ACARs system can be fooled by momentarily applying the parking brake and opening a door prematurely, thus signalling a false arrival time.
The consequences
Both of these unauthorized practices greatly increase the risk of aircraft standing at the gate with the parking brake left off. In this situation the aircraft may or may not immediately move – it may be held stationary by the wheel chocks and/or the small ‘tug’ vehicle that is used for pushback. However it may spontaneously start to roll later, at any time. Most ramps slope slightly for drainage and a large aircraft fully loaded and fuelled weighs hundreds of tons. In an uncontrolled roll it becomes a massive slow-motion projectile that can injure or kill ground staff and collide with gate structures, ground equipment or other aircraft. It is also quite conceivable that a ground collision involving two aircraft could result, potentially injuring or killing many people.
The evidence
Gate incidents are a significant source of risk for passengers and crew: internationally, hundred of such incidents are reported every year, some of them involving fatalities. Uncontrolled or unplanned rollbacks represent a significant proportion of gate incidents.
It is impossible to determine how many of these incidents are related to these ACARs-related practices, however various sources (such as online forums frequented by pilots) suggest that such practices are widespread and are a matter of concern to many airline staff.