Fatigue – Aircraft Maintenance Engineers Can Make Mistakes With Disastrous Consequences

flight maintenance engineer

We all know how concentration suffers when we’re feeling tired, and that the hours we work – and their timing – have a strong influence over this. We also know we aren’t the only link in the chain of getting safely from A to B without human error creeping in. We’re talking about the engineers maintaining your silvery birds.

Inevitable commercial pressures within the organizations they work for, as well as the vagaries of their own personal circumstances can, and often do, motivate them to work extensive hours. There have been some serious incidents where fatigue has been cited as a contributory factor leading to the initiating maintenance error.

The most recent high-profile event was the BA A319 in May 2013, which suffered a double cowl loss following maintenance by two engineers on a night shift. In the preceding 14 days the certifying engineer had worked four 12-Hour day shifts and eight 12-Hour night shifts (not including breaks) and the non-certifying engineer wasn’t far behind.

Thankfully BA have now amended procedures to more appropriately control hours, and of the five safety recommendations made in the AAIB report, the first one related directly to implementation of Fatigue Risk Management Systems (FRMS’) for maintenance organizations.

This is not the only instance where maintenance error has occurred on a night shift when circadian rhythms are at a natural low; fatigue has been implied or directly cited as a factor in the maintenance errors that led to the following serious incidents and, sadly, catastrophes:

BAC one-eleven, over Didcot, Oxfordshire, 1990

A windscreen blew-out during climb at about 17,000 feet. The windscreen had been replaced beforehand on a night shift using the wrong bolts.

Bombardier DHC-8-102, April 2010, Bristol

In-flight shut down of right engine following significant oil leak; shortly afterwards the left engine also started leaking – fortunately a diversion and safe landing was achieved. O-ring seals within the oil cooler fittings had been damaged during a C-Check. In the preceding 17-week period, the supervisor signing-off had worked an average of 57 hours/week (9 hours/week over the UK Working Time Regulations (WTR); he had also averaged 15.7 hours/day in the 10 days leading up to the C-Check’s commencement.

Eurocopter AS350, near Las Vegas, Nevada, December 2011

Lapses in maintenance led to a hydraulic servo providing inputs to the main rotor head disconnecting, resulting in a catastrophic loss of control. Investigators determined significant fatigue had been present in both the mechanic who carried out the work and the supervisor/inspector.

Air Midwest Flight 5481 North Carolina, January 2003

Aircraft crashed on take-off. As well as being overweight, the investigation found that elevator travel was restricted due to improperly rigged flight control cables. Maintenance work to the aircraft’s elevator system was again performed during a night shift in the early morning hours.
Of course there are other issues compounding fatigue such as lengthy commutes, unsettled home life, shift changes, excessive workloads etc. etc. The investigation into the A319 double cowl loss event showed the engineers had not opted-out of the WTR. This implies there are others out there working even longer hours – indeed the report into the DHC-8-102 oil-loss incident states that ‘97% of engineers at the AMO, including Sup A, had signed an ‘opt-out’ agreement so that the 48-hour limit would not apply to them’; it also found that the maintenance organization had no policy on maximum hours engineers could work in any 24-hour period.
The Air Navigation Order makes it an offence to work on aircraft whilst knowingly unfit to do so, but there are currently no mandated limits.
Is it right that someone performing a safety critical role – indeed one that you pilots and several hundred other lives depends on, can work 80 or 90 hours a week, week after week – or for them to be able to do back-to-back double shifts, on a Friday, Saturday, and a Sunday? Right now they still can. As can be seen above, this isn’t just a UK problem and industry is trying to address the issue. However the extreme ends of the scale should be prevented – it’s really just a question of common sense – or maybe everyone’s too tired for that?


The portfolio holders believe that efforts should continue to focus on removing the UK WTR Opt-Out for maintenance staff. ASG should also engage with the CAA and EASA (through its HFWAG (via its European Human Factors Advisory Group (EFHAG) – http://easa.europa.eu/node/15714) to ensure maintainer fatigue is afforded the priority it deserves.


[Original article source]

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