Tuesday, October 1, 2013
Emergency Egress Revisited
An accident investigation recently revealed once again – this time in the densest of urban settings – that helicopters are marvelous as aircraft, but are thoroughly misplaced when forced into unsolicited duty as boats. Most helicopter designs feature lots of machinery located topside, which usually produces a dramatic tendency for the aircraft to roll inverted almost any time the surface of water is encountered. The recently publicized New York mishap involved a Bell 206 sustaining a survivable impact to water just after departure, after which it immediately inverted, posing a specific and familiar survival challenge to its occupants. The fact that not all of the occupants succeeded in getting out of the undamaged but submerged cabin suggests that a review of water-filled enclosure blind egress procedure, developed during 1970s era accident analysis, might be a useful exercise for all contemporary helicopter users.
Not all helicopter users share an equal likelihood of unplanned water immersion, but they all, to include night EMS operators in most U.S. locations, face the same range of hazards once there. The average helicopter occupant not equipped with HEED (emergency air) gear can reliably tolerate submersion in warm water for about a minute. But in water below 65 degrees, breath-holding endurance diminishes rapidly. Although most water in North America is less than 70 degrees most of the time, breath-holding is usually not the central survival limitation, since a normally executed evacuation should take only 12 to 15 seconds. Swimming ability would seem to be another critical factor, but technically it is not. Swimming should never be attempted within the confines of a submerged aircraft cabin because it is not efficient and it increases the chances of the survivor becoming entangled or entrapped by obstructions. One conspicuous non-survivor carefully studied by the U.S. Coast Guard had actually egressed the side window of a cockpit and was very near the water’s surface when a swimming kick snagged a boot lace on a lever. This proved to be his last living act. Weak swimmers and even non-swimmers, though, can escape a submerged aircraft using the proper techniques.
To maximize the probability of surviving a submerged cabin at least two cabin egress routes should be identified. Visualization of these routes must be accomplished with eyes closed, actually feeling seat backs, dividers, instrument panel glare shields – any handholds that are secure and unlikely to change location with impact or flooding. Cabin doors can become jammed or obstructed, during or after impact, so a clear plan for using backup exit routes is essential.
If ditching becomes imminent, exit routes should be reviewed, and lap belts/restraint harnesses should be checked tight. If personal flotation devices are being worn, or are available, they should be kept handy but not inflated or armed, since premature inflation of such equipment is likely to create serious entrapment hazards.
As the aircraft contacts the water, doors can be jettisoned. Simple egress may be possible at this time, but if the aircraft doesn’t remain upright, it will fill with water rapidly with doors open, and the submerged cabin scenario will develop quickly. Several deep breaths can be undertaken just before immersion, remembering that the cabin will usually fill with water in only five to eight seconds. The urge to release seat restraints while the water is rushing in should be resisted, but headsets, helmets, and any other secondary attachments to the aircraft should be disconnected at this point. If individuals become unsecured in the cabin during inrushing of water, they may be moved unpredictably, usually producing extremely dangerous disorientation. When the rush of the water stops, a firm grasp of a previously established reference point should be maintained with one hand while releasing seat restraints with the other.
With primary reference point firmly in hand, you should visualize where you are in the cabin and how to proceed along your primary exit route. Pull yourself hand-over-hand along that route. Do not kick your feet or attempt to swim. Pulling is faster, requires less energy, minimizes the chances of becoming entangled and prevents disorientation. If you detect a random source of light, ignore it, since it may be a sealed window.
When you reach the open door, pull yourself through with a strong heave and move free of the aircraft. Now your flotation device can be inflated to assist in achieving the surface.
Beyond the aviation setting, media almost weekly report emergencies involving people becoming trapped in smoke-filled rooms, or in automobiles – situations requiring rapid exit for those deprived of normal visual orientation. Practiced emergency exit technique alone can’t solve every egress problem, in aircraft or elsewhere, but if pertinent lessons learned from past accidents and loss are assimilated, chances of escaping any enclosure, under almost any circumstance, are greatly improved.