One critical aspect of the Emirates Boeing 777-300 landing accident in Dubai which has yet to become clear is the decision process which led the crew to execute the ill-fated go-around.
Investigators found that a long-landing alert sounded in the cockpit just as the aircraft touched down on runway 12L, some 1,100m past the threshold.
While the inquiry has not specifically stated that the go-around was triggered by the alert, it says the aircraft became airborne, during the go-around attempt, just 4s after the warning sounded.
The General Civil Aviation Authority, which has disclosed factual data on the 3 August accident, has yet to reach any conclusions on the crew’s decision.
Runway 12L has a length of 4,050m and, although its threshold is displaced by 450m, the runway distance remaining following touchdown would probably have been around 2,500m.
Boeing data indicates that, for a dry runway in zero wind, a 777-300 at maximum weight would require a sea-level landing runway length of some 1,800m.
Emirates has been closely involved with avionics specialist Honeywell’s development of the SmartLanding and SmartRunway safety tools – an evolution of the manufacturer’s runway advisory and awareness system.
The tools are a software upgrade to the enhanced ground-proximity warning system and are designed to reduce the risk of overrun by comparing an aircraft’s approach profile with the length and condition of the runway.
Honeywell says the trigger for a long-landing warning can be customised, with various options available in the reloadable customer definitions database.
These include setting the system to alert at a fixed distance from the approach or far end of the runway, or a point where a specific percentage of the runway, such as the first 25%, has been passed.
Honeywell says the intent of the long-landing alert is to “match” the standard operating procedure of the carrier, and it points out: “The alert is not intended to be landing performance monitor.”
Investigators have not disclosed the specific settings which were being used on the Emirates 777-300 at Dubai, nor the standard procedures which crews are expected to follow in the event of receiving a long-landing caution.
The aircraft’s captain, who was flying, had accumulated close to 7,500h of which more than 5,100h had been on the 777.
Cockpit crew representatives support the development and installation of runway overrun alerting systems as a means to cut the chance of longitudinal excursion.
But the International Federation of Air Lines Pilots’ Associations also notably states that such systems should be viewed by the crew as a “safety net” and “not as a substitute for pilot assessment” of landing distance calculations or braking performance monitoring.
The federation also insists that they must provide timely and explicit notification to crews.
“Warnings issued by [runway awareness systems] should be clear and unambiguous,” it says in a position paper issued in mid-September.
“They should be descriptive, in the case of a calculated possible overrun, or prescriptive in the case of a calculated overrun.”
Operators should also develop “clear and unambiguous” standard operating procedures and call-outs, it adds, regarding these systems, and their use should be part of initial and recurrent training.