A number of serious incidents have been attributed to incorrect takeoff performance. A total of 20 occurrences were identified between the period 1 January 1989 and 30 June 2009 where the calculation or entry of erroneous takeoff performance parameters was cited as contributing to commercial jet aircraft accidents
The Boeing 777-F takes off on 22 May 2015, from Paris Airport at low speed and the tailstrike protection (TSP) of the aircraft is activated. The plane does not take height. The crew then applies the full thrust. The aircraft flies over the opposite threshold at a height of approximately 170 ft and continues to take off. During the climb, the crew questions the causes of the incident and realizes that it has made a mistake of 100 tons in the mass used for the calculation of takeoff performance. The crew continues the flight to destination without further incident.
The Captain and three Co-pilots prepared a cargo flight from Paris – Charles-de-Gaulle bound for Mexico City. While the two Relief Pilots carried out the exterior walkaround and checked that the load was safely in place, the Captain (PM) and the Co-pilot (PF) carried out the flight preparation in the cockpit.
The Co-pilot added up the various scheduled weights in his head and found a preliminary Take-Off Weight (TOW) of 243 tonnes instead of 343 tonnes. He entered this erroneous value in his Onboard Performance Tool (OPT)(3). The Captain added the supplementary fuel decided on by the crew to the TOW on the Operational Flight
Plan (OFP) and obtained a correct weight of 343 tonnes. The Captain entered the same erroneous TOW (243 tonnes) into his OPT as that calculated by the Co-pilot.
The Captain and the Co-pilot then cross-checked the take-off parameters calculated by their respective OPTs and obtained the same results.
The crew began to enter the OPT results, obtained from an erroneous TOW of 100 tonnes, in the FMS. The Co-pilot (PF) entered, in particular, the balance, an assumed temperature of 37°, a flap configuration of 5°, and the V1 of 143 kt calculated by the OPT(4). The Captain was surprised that the calculated take-off speeds were about 20 kt below the reference speeds calculated by the FMS.
The Captain received the Final Loadsheet and announced the final load figure to the Co-pilot (PF). The latter recalculated on paper, the take-off weight based on the Dry Operating Weight (DOW), the payload and final fuel weight. He made carrying over error and obtained 241.5 tonnes instead of 341.5 tonnes. He compared the newly calculated value (241.5 tonnes) with that previously entered in his OPT (243 tonnes) and called out ‘‘it is consistent’’.
The Captain compared the Take-Off Weight (TOW) of the Final Loadsheet with the gross weight (GR WT)(5) displayed on the FMS and found that they were consistent.
The latter was correct because it was calculated from the Zero Fuel Weight
(ZFW) – which was correctly entered into the FMS by the crew – and the fuel on board automatically calculated by the aircraft.
When the refuelling was completed, both crew members went back to entering the speeds. This time, the reference speeds were no longer displayed and the crew unsuccessfully tried to display them by repeatedly pressing REF SPDS ON/OFF. None of the crew members understood why the reference speeds had disappeared.
The Captain and Co-pilot (PF) re-entered all the data in the FMS starting with the ZFW. The reference speeds calculated by the FMS were still not displayed.
The crew finally entered into the FMS, the take-off speeds calculated by the OPTs (V1=143 kt, VR=152 kt and V2=156 kt) for take-off. The flap configuration was 5°. This configuration surprised one of the Relief Pilots, but he did not express his misgivings. The aircraft lined up for runway 26R from taxiway T12 and took off at 10:25.
The following elements may have contributed to the 100 tonnes error not being detected and its propagation:
Humans are adaptive and flexible but are still prone to making errors. The reasons for the failure attributed to human factors have been investigated. Various measures have been taken by the airlines and industry to eliminate the errors. However, either the error reoccurs or new types of error occur.
The problem is that not every scenario can be defined and resolved. New types of error or unexpected errors may occur.
The human represented by the flight crew have to be trained to identify and mitigate the risk generated by these errors.
Since errors are not intentional, and since we do not need a particular theory of errors, it is meaningless to talk about mechanisms that produce errors. We need to look at reasons for non-compliance of normal procedures.
Inventing separate mechanisms for every single kind of ‘human error’ may be great fun, but is not very sensible from a scientific point of view (Cacciabue, Hjälmdahl, Luedtke, & Riccioli, 2011, p. 4). Repeated and error-free operation can be achieved through enhanced awareness of the situation, preventing distractions and increasing concentration.
If cockpit checks and checklists were to be performed diligently, there would be no room for error. One of the reasons for errors to escape the human barrier is what is called “learned carelessness”.
Checklists are used in aviation in order ensure that critical actions are carried out and they are confirmed and/or crosschecked by the crew. Checklists are carried out on every flight but incidents occur rarely. According to Frey and Schulz-Hardt(1997), (Aust, Moehlenbrink, & Jipp, 2011), procedures of this type can lead to the development of a psychological state called learned carelessness.
Humans are “cognitive misers” (Wickens & Hollands, 2000) which means that they follow the path of the least cognitive resistance. A reduction in effort is positively reinforcing and therefore, increases the likelihood of future shortcuts in the absence of negative consequences.
The underlying motivation is assumed to maximize pleasure while minimizing discomfort. Once learned carelessness has developed it will distort a person’s perception, selection, and interpretation of subsequent information in favour of the monopoly hypothesis. This top-down information processing impairs motivation and capability to detect incidents. The result is unreasonably risky behaviour.
Such events can be prevented by practising ‘Mindfulness’ or the age-old ‘Vipassana’, which means to see things as they really are, is one of India’s most ancient techniques of meditation. It was taught in India more than 2500 years ago as a universal remedy for universal ills. Being present at the moment with undivided attention will ensure that the mind, brain and senses are working in unison.
For the non-aviators, I would suggest that they watch the movie, ‘The great art robbery’.
This movie is about how our brain gets deceived by attention or loss of it.
Category: #safety, #training, Aviation, Human Factor, Social animalTags: #humanfactor, #safety, #takeoffperformance, attention, carelesness, distraction, learned, learnedcarelesness, speeds, takeoff, vipassana, weight
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