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Thursday, October 1, 2015

HEMS Watch

Dress for Success

By Terry Terrell

A moderately wise helicopter pilot once proclaimed that it is better to dress to avoid an accident than to survive one.

This postulation brings to mind a rough approximation of a quandary I originally appreciated in the 1970s as Ralph Nader declared Chevrolet’s Corvair unsafe at any speed. He suggested that cars from that time forward be made crashworthy, rather than have designers plan (perhaps by refining brakes, suspensions and weight distributions) to have motorists avoid crashes in the first place.

This same sort of strategy selection is with us constantly in aviation, as endless choices are made generically (and by individual case) regarding what equipment to use when flying, what to wear and even how to interface with the aircraft.

It has long been known, for example, that facing airline seats rearward would substantially improve safety during survivable deceleration-type mishaps. It is also known that passengers—likely to demonstrate a psychological aversion to flying backwards—would mutiny in the marketplace, virtually destroying ticket sales if a backward-seat design were ever to be implemented.

With helicopter flying, there are a couple of “dress” strategy choices. Helmets have now become standard operating equipment in many rotary-wing sub-specialties, certainly to include emergency medical services. On the face of it, this embracing of a protective gear choice would seem to be a sensible and useful trend.

But evaluating the effectiveness of such a convention is not as simple as it might seem.

True, helmets can provide protection against the threat of minor or intermediate impact concussion injuries. Their typically installed visor features are clearly valuable in minimizing bird-strike hazards to the eyes of pilots and crews. But from there, value analysis becomes more complex.

Helmets represent an increase in weight and mass supported by the wearer’s neck, back and spine. It will probably always be true that most survivable helicopter accidents present occupants with the reality of high vertical-impact stresses. Having the neck support a heavier load during such encounters can never be considered a good thing, since that tends to measurably increase the likelihood of a neck or spine injury.

Also, in cases of more extreme impact-generating accidents, like most midair collisions, helmets can’t be expected to improve survivability very much in any case.

It must always be appreciated that helmets inevitably represent at least a slight degradation of visual efficiency, restricting peripheral vision and scan flexibility to some extent. Therefore, to some degree they increase the chances of an undetected threat of midair collision in the first place. I suppose this is another way of suggesting that sometimes (perhaps when flying into a setting sun, for instance), a good headset and a baseball cap could reasonably be considered a superior dress selection to a full-coverage helmet. This is especially the case when the head is further burdened with night vision goggles hardware in anticipation of night conditions.

With regard to NVG equipment, I can recall at least one instance in which the use of goggles generated a distraction in the cockpit that was nearly catastrophic. To be fair, this episode occurred a number of years ago, as one particular EMS operation was flying its first operational NVG familiarization hours.

The pilot, innocently unaware that his muscle-memory habit patterns and performance around the cockpit environment might be subtly altered as he concentrated on NVG use, inadvertently switched off his hydraulics system master switch. This caused a flight attitude upset that could have been disastrous if his flying skills had not been good enough to accomplish a safe recovery.

A major challenge, of course, (implicit in deciding exactly what dress and equipment options provide optimum safety and performance) lies in appreciating that the conditions presented in flight operations are constantly changing, and that a nearly infinite range of selections would be required to accommodate all likely scenarios in any given setting. It will never be possible to anticipate all imaginable helicopter flight demands with perfectly ideal dress and equipment selections, so our task will always involve making intelligent compromise choices.


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