Taking off with incorrect weight data entered into the flight management system is happening with sufficient regularity that the industry should be worried about it.

In its recent report on an incident involving a Virgin Atlantic Airbus A340-600 take-off incident at London Heathrow, the UK Air Accidents Investigation Branch has admitted that adding additional take-off performance figure checks to the already thorough system Virgin uses to try to prevent errors like this would be more likely to create problems than solve them. Alerting pilots to the fact that weight data is frequently entered incorrectly and that no crew should ever consider itself immune from making such a mistake probably has some effect immediately after such a bulletin is issued, but that awareness of risk will fade as time passes and the number of successful take-offs builds, and the checking routine becomes more of a routine than a system of checks. That's human factors. To deny it is foolish.

Cockpit
 © Max Kingsley-Jones/Flightglobal
Weight watchers are needed in the cockpit

What can be done to reduce this risk before there is a serious accident? It's an urgent question, but since most of the events did not lead to fatal accidents because there was sufficient runway left to accelerate to a rotate speed that was adequate for the actual weight rather than the lower one entered, the motivation to find a solution does not seem to be sufficiently strong.

But in 2004 an MK Airlines Boeing 747-200F crew was not so lucky in its attempt to take off from Halifax, Canada. The weight entered into the electronic flight bag performance calculator was far too low, so the system provided a commensurately low rotate speed. The 747 went off the runway end at 155kt (285km/h) and was destroyed with the loss of all the crew.

The AAIB has called twice now for industry to find a technical solution before an aircraft full of passengers crashes. There are two basic ways in which a system could alert the pilots to wrongly entered weights. One would recognise inconsistency in the figures at entry and alert the pilots: Airbus is promising such a system for the A350. The other would be a take-off performance monitoring system that would recognise the sluggish acceleration resulting from the entry of a falsely low weight and warn the pilots in good time.

A good monitoring system has been a holy grail for many. Airbus is close to a potential solution, but is the solution commercial? What kind of accident would it take to make such a system commercial, or get it mandated like terrain awareness warning systems were?

Source: Flight International

Topics