Dutch investigators probing a serious Boeing 737-800 take-off incident at Groningen have noted that pilots are seldom exposed to performance-related events during simulator training.
The Dutch Safety Board found that the first officer had miscalculated the take-off weight, introducing a 10t error, which resulted in the Transavia aircraft's only becoming airborne 60m from the end of the runway.
It describes the incident as "critical", pointing out that – even before the calculated V1 decision speed – the captain had realised that the take-off could not be safely aborted with the remaining runway length.
Boeing subsequently calculated that the calculated V1 threshold was 15kt higher than the safe 122kt abort speed.
But the inquiry into the September 2014 incident determined that, despite observing the slow acceleration, neither pilot took corrective action to increase the engine thrust.
The first officer had been the pilot flying, while the captain, as monitoring pilot, had his hand on the thrust levers.
"As a consequence the first officer could only select full thrust by requesting the captain to do so," says the inquiry.
"For the captain as pilot monitoring there might be a reluctance to add thrust, as it interferes with the operation of the first officer as pilot flying.
"Actions from either pilot would have required clear communication and time."
Analysis of similar performance-related take-off incidents reveals that no additional thrust was selected in the majority of cases, the inquiry states, and that early rotation is only occasionally initiated.
Pilots regularly undergo simulator training to handle time-critical events such as engine failure during take-off.
But the inquiry claims: "Performance-related incidents are not trained in the simulator and the accompanying cues are less obvious.
"[Owing] to the time-critical situation, and the lack of associated and trained procedures, it is less likely that pilots take corrective action during a performance-related event."
Reduced-thrust take-off is used to limit wear and conserve engine life, reducing maintenance costs for the carrier.
But the inquiry says that using reduced thrust carries an increased chance of performance-related mishaps.
"As the variables that determine the cost benefit of reduced-thrust take-offs vary with time, there might be times when the safety risks of conducting these take-offs outweigh the decrease in maintenance costs achieved by them," it adds.
Source: Cirium Dashboard
