Air travel is as safe as houses. Really. But airliners are incredibly sophisticated feats of advanced engineering, so why don’t they go wrong more often?
There are many obvious reasons. They include design progression, which incorporates not only stepwise refinement over time, but also learning the lessons of earlier passenger jet problems from the Comet through to Concorde. Materials science plays a part, with the development of advanced composites and the application of metallurgical forensics. Mention also has to be made of the skill, quality and dedication of maintenance engineers the world over. It’s thanks to all these things that we can roll up to the airport with hardly a care, secure in the expectation that the plane will be ready and that it will take us safely to our destination.
There’s one other factor in the maintenance equation that may not be so obvious but which is of the utmost importance in ensuring not only that our flights are safe but that their cost isn’t too inflated. That factor is the emergence and development of Health & Usage Monitoring Systems, or HUMS. Time is money, and nowhere is that more true than in the aviation industry. A new aircraft costs, in dollars, a nine figure sum. To get payback, the airline must keep the plane in service, in the air, as long as possible. Maintenance activity on a modern airliner is non-trivial. It is essential for the economics to work that aircraft are offline for maintenance for not a minute longer than is necessary to guarantee the highest possible level of safety. HUMS involves the placement of sensors on strategic components of an aircraft and its engines, that yield data on usage, vibration and temperature. This data is collected and analysed during and after every flight, and used to refine the maintenance schedule for the aircraft and its major systems. Minute temperature changes may give only a short warning before a catastrophic failure, but vibration anomalies will typically give warning of maybe as much as a hundred flight-hours that something is going awry.1 HUMS therefore offers the dual benefit of detecting things that may be going wrong before routine scheduled maintenance is due, but also the ability to confidently postpone maintenance activity until it really is necessary.
What happened to QF32 on 3rd November was without doubt an exceptional event, which explains the worldwide media attention. It’s pointless to speculate at this juncture as to just what caused its number two engine to blow up: whatever it was its no exaggeration to say that it will have a been a one in a million occurrence, given the sheer number of flights that progress safely day in and day out throughout each year. The kind of advances that Critical Software is making in HUMS, and the related disciplines of structural health monitoring and condition based maintenance, will ensure that air travel becomes even safer in the future, even though high profile events like that which occurred on QF32 will still happen from time to time.