FATIGUE – Tired Aircraft Maintenance Engineers (AME’s) Can Make Mistakes With Disastrous Consequences
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 organisation 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.
Stuart Mackrell and David Haward, November 2015
Stuart and David are both ASG members and both hold positions on the committee. This article was written for BALPA and originally appeared in the 'Log' Winter 2016