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ASN Wikibase Occurrence # 176645
Last updated: 11 April 2021
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Time:10:25 UTC
Type:Silhouette image of generic B77L model; specific model in this crash may look slightly different
Boeing 777-F28
Owner/operator:Air France
Registration: F-GUOC
C/n / msn: 32966/752
Fatalities:Fatalities: 0 / Occupants: 4
Other fatalities:0
Aircraft damage: None
Category:Serious incident
Location:Paris-Charles de Gaulle Airport (CDG/LFPG) -   France
Phase: Take off
Departure airport:Paris-Charles de Gaulle Airport (CDG/LFPG)
Destination airport:Mexico City-Benito Juárez International Airport (MEX/MMMX)
Investigating agency: BEA
The crew used a takeoff mass of 243 tonnes in their performance calculations, while the actual weight was 343 tonnes.
The calculated speeds were entered in the FMS. During rotation the plane failed to respond as expected. The crew then used TOGA power for a safe takeoff.

Causes and contributing factors:
The low-level overflight of the runway end during take-off resulted from a take-off undertaken with incorrect parameters (take-off speeds too low, insufficient flap setting and thrust).
The incorrect parameters, entered into the FMS and used for take-off, result from a performance calculation based on a mass 100 tonnes lower than the actual weight of the aircraft.
The 100 t error occurred when the estimate was made by each member of the planned mass and its entry into their EFB.
The following factors may have contributed to the lack of detection and propagation of the 100 t error:
- the crew's handling of numerous formats, media and titles of take-off weight data;
- the non-use of orders of magnitude, partly due to the increasing use of performance optimization tools;
- procedures including many basic but not very robust controls, taking insufficient account of the operational context and crewed operation. These procedures are based in particular on a supposedly independent double calculation, whereas a simple verbalization can put this independence at risk. These procedures do not include a means of detecting gross errors or simultaneous control of the three media using mass data (load state, OPT and FMS);
- the absence on this aircraft, as on most commercial air transport aircraft, of systems to detect or prevent such gross errors and warn the crew, or systems to warn the crew that the performance measured during take-off flight is insufficient.
Some of these points have been identified for several years by various investigation authorities, in particular by the BEA through a safety study on this issue, published in 2008.
The lessons learned from the analysis of many incidents and accidents around the world did not lead the aviation community to make significant progress on this subject until the serious incident of F-GUOC.
In particular:
- even when the state of the art technology became favourable, the civil aviation authorities were unable to encourage manufacturers to develop and then deploy appropriate technical solutions in a satisfactory manner;
- similarly, the development or even deployment of new systems by some manufacturers has not led these authorities, in particular EASA in Europe, to study their benefits and, where appropriate, to promote their wider deployment.


Accident investigation:
Investigating agency: BEA
Status: Investigation completed
Duration: 3 years and 7 months
Download report: Final report


Photo of F-GUOC courtesy

Glasgow - Prestwick (EGPK / PIK)
7 June 2019; (c) Martin Bridges

FDR parameters (BEA)

Revision history:

04-Jun-2015 20:14 harro Added
22-Dec-2018 08:51 harro Updated [Time, Registration, Cn, Total occupants, Narrative, Photo, Accident report, ]
22-Jan-2019 18:08 harro Updated [Source, Accident report, ]

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