Much research has been done on human factors in maintenance, but the tasks that face managers have still not changed

The Taiwan Aviation Safety Council (ASC) "factual data collection" on the China Airlines Boeing 747-200 that suffered catastrophic structural failure has highlighted problems that aviation has always suffered. If the final report reflects the ASC's instinct, as demonstrated by its clearly developing area of focus - a rear fuselage repair made 23 years ago, around which fatigue cracks had developed - then the issue, as usual, will be one of human factors.

Meanwhile, the January 2000 crash of one of its Boeing MD-80s still haunts Alaska Airlines - some families of those who died have still not settled their compensation claims and a court will rule some time in the next few months on whether punitive damages are appropriate. The US National Transportation Safety Board (NTSB) judged this to be a maintenance-based disaster of staggering simplicity: a crucial mechanical system controlling the horizontal stabiliser - very robust but with no failsafe system fitted to cope in the event of physical breakage - broke because of inadequate lubrication.

Early investigation by the NTSB in the case of the US Airways Express Beech 1900 crash just after take-off from Charlotte Douglas airport in January this year suggests that mis-rigging of the pitch controls was a significant factor in the accident, although load management has also been cited.

The generic problems, individual mistakes, failures to follow procedure, or faulty management systems that these events highlight are common to engineering in all fields. But as Capt A G Lamplugh of the British Aviation Insurance Group said famously in the early 1930s: "Aviation is, in itself, not inherently dangerous, but to an even greater extent than the sea it is terribly unforgiving of any carelessness, incapacity, or neglect." This has often been thought of as applying to flightcrew and the exercise of their skills, judgement and airmanship, but Lamplugh was almost certainly referring to the entire task of keeping aircraft fit to fly as well as safe in the air.

There is a certain level of resignation - possibly even defeatism - in some airline engineering departments' credo that carrying out maintenance or repair tasks before they are essential is not necessarily the safest way to manage them if it results in more frequent work on the aircraft. The argument is that maintenance itself can be dangerous because, especially in repair or replacement tasks that involve much dismantling, there is room for error both in the execution of the objective and in the reassembly process. But mistakes are made even in routine jobs. Failure to replace O-ring seals or blanking plates after an oil change or an inspection is not frequent, but in recent years at least two such events have forced crews to act fast to get their aircraft on the ground before the engines seized up.

The industry is taking grand strides towards instituting improved systems for quality control in operations and engineering. These are laudable, and if they work perhaps there will be fewer events like the Alaska MD-80 crash, after which an overdue Federal Aviation Administration audit of the carrier's maintenance practices found that an admired and operationally innovative airline was not so smart in the hangar.

There has also been painstaking research over more than a decade, led by organisations like Boeing and the International Federation of Airworthiness, to research the complex business of human factors in maintenance. Seminars on the subject have become common. But back in 1980 when China Airlines carried out work on the rear fuselage of its ill-fated 747-200, the world's worst single-aircraft accident - a maintenance-caused mid-air pressure hull failure to a Japan Airlines Boeing 747SR-100 in 1985 - had not yet happened, and neither had the 1988 Aloha Airlines 737-200 event in which it lost an entire section of cabin fuselage just behind the cockpit but landed with the loss of only one person. The former showed how a maintenance failure can "sleep" for years before it kills, and the Aloha event woke the world up to the other maintenance time-bomb: old and high-cycle aircraft.

Despite all the research, hard work and better-designed workplace practices, maintenance is still carried out by human beings with all their failings, and airlines still operate old aircraft. The ultimate test of a well-run maintenance hangar is that the people who work there know how important their every job is, feel their work and their judgement is appreciated by their seniors, and are proud of that.

Source: Flight International