Maintenance faults suspected in French Canadair CL-415 incident |
| Helen Chachaty |
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29 NOV 2017 | 691 words
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© BEAD Air |
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France's BEAD Air (Investigation and analysis agency - Defence) recently published its report on the incident involving a Canadair CL 415 which occurred on 1st August 2016 at the Ajaccio base in Corsica while it was taxiing. The water bomber's main gear had collapsed, requiring the mission to be interrupted and grounding the whole fleet while the necessary checks were carried out on the other aircraft.
BEAD Air's conclusions confirm the collapse of the right landing gear while taxiing "due to a breakage of one of its components following a maintenance error generated by a translation fault in technical documentation". Six causes have been identified: "CMM ("component maintenance manual") translation error" in the equipment intervention procedure, lack of supervision, migration and violation of maintenance procedures, non-conforming alignment of the brace strut, change of slope and passage on turn of the channel, high speed and absence of a speed limit in the documentation".
The time-scale for the events reports that the Canadair registered F-ZBEU started its alignment "by turning to the left" and crossing a runway run-off water channel at a speed of 14 knots, a manoeuvre during which "the crew felt a subsidence on the right hand side". The damage was observed "in the lower part" at the level of the hull, the right main gear and the right bag. As for the right landing gear, "the elements composing the brace strut's system for locking in lower position were broken", like "the elements providing the link between the gear's actuating cylinder and the gear's lower kinematic system". The report also recorded "debris [...] in the lower part of the gear's compartment".
Crossing the channel at too high a speed ("2.3 times higher than the speed requested by the pilot") seems to have led to the loss of the landing gear, as this manoeuvre was not carried out "at the same time by both wheels", generating "a compression/release/compression" phenomenon, leaking to the brace strut being unlocked - which is one of the components of the landing gear which prevents ground subsidence. This brace strut, which had already been showing signs of damage, was adjusted "well beyond the recommended range", causing the "automatic unlocking of the right landing gear" and premature wear. This was made worse by the presence of over-wedges, which led to "a wrong angle between the two semi-brace struts". "Of indeterminate origin", the installation of these over-wedges constitutes "a violation during maintenance with the desire to hide it".
The faults observed on the brace strut highlight the serious maintenance failings identified by BEAD Air, which calls into question Sabena Technics as an MCO (Maintien en Condition Opérationnelle) body and the sub-contractor since 2007 Hydrep, which has become Safran Landing Systems Services Dinard since then. Blame is also placed on Antavia, the previous sub-contractor. The technical failure of the brace strut results from an adjustment which did not comply with the manufacturer's directives, but also an "initial violation of the procedure" and a "lack of vigilance" by maintenance companies, with the report accusing Sabena Technics of a maintenance procedure "supervision failure".
These procedures had initially been written in English, but were translated into French by Hydrep, with no proof-reading and with no verification against the CMM. A translation error led to a "wrong angle between the upper and lower brace struts", but the report also notes "partial maintenance of the brace strut", which made a direct contribution to the incident.
Among BEAD Air's recommendations are the revision of the brace struts by the relevant procedure (PSP 498), modification of the CMM "adding warnings and mathematical formulae for the definition of the adjustment ranges", and also the approval of procedures for government products by Safran Landing Systems Services Dinard "by someone other than the author". The incident report also recommends that Sabena Technics "present to the DSAE, the SIMMAD, to government clients and the DGA quality department all the elements which guarantee satisfactory supervision of internal and sub-contracted activities, including those which are not monitored by the DGA quality department".
Le Journal de l'Aviation contacted Sabena Technics but they were not immediately available to comment on these conclusions.
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