In this post, we will continue our cold water survivability discussion and take a look at how the mechanics of a crash itself affect cold water survivability issues.
A passenger’s chances of surviving an aircraft’s initial impact with the water are most dependent on the degree to which the aircraft in under control at the time of the crash. We can analyze this factor under three broad categories:
The first category involves crashes where the aircraft has a high angle of descent and high rate of speed. In these crashes, the fact that the aircraft is impacting water instead of the ground makes little practical difference from a physics standpoint. Alaska Airlines Flight 261 is a tragic example of this type of crash, the speed and angle of impact made the crash not survivable. Krutch Lindell represented families of victims of Flight 261.
The second category is where the aircraft has a low rate of speed and a low angle of descent. This is the “ditching” situation described above. In this case, the aircraft is usually under positive control, and a large part of the success of the ditching is the type of aircraft involved and the skill of the pilot.
For example, the procedure in a helicopter with an engine failure generally follows the procedure for an autorotation approach and landing. As the helicopter nears the water, the doors should be opened. When the helicopter contacts the water, the pilot usually lowers the collective pitch and applies sideward cyclic in order to cause the rotor blades to strike the water and stop rotating. Then the crew and passengers release their belts and exit the helicopter. The low speed and angle of a helicopter ditching results in generally high initial impact survivability.
Ditching in a seaplane involves landing on the floats (or hull). Because seaplanes were designed to land on water, the initial impact in a controlled ditching in a seaplane is usually very survivable.
The initial impact survivability in ditching a regular (land-based) airplane is highly variable. Factors such as the weight and size of the aircraft, whether it has retractable landing gear, whether there are engines underneath the wing, its minimum approach and stall speed, and the direction and size of the waves all play a role in the initial crash mechanics. Generally, controlled ditching in jetliners has been largely successful (think US Airways Flight 1549 – the “Sully” landing). By contrast, ditching in small, fixed gear aircraft often results in the aircraft flipping and breaking up on initial contact with the water – in this circumstance the crash becomes less survivable as discussed in category three below.
The final (and third) category would be where the aircraft has either a high rate of speed and a low angle of descent, or a high angle of descent but a low rate of speed. These crashes have highly variable initial survivability. For example, many aircraft used in seaplane operations were built more than 60 or 70 years ago – before designing airframes for crashworthiness was an important consideration. Often, even minor damage to these aircraft makes a large impact on egress, or the ability to escape from the aircraft after the crash. For example, I have handled cases where the fuselage deformed in the impact, jamming the airplane’s doors closed and preventing escape for some of the passengers from the sinking wreckage.
Both the United States National Transportation Safety Board and the Transport Safety Board of Canada have analyzed accidents in water in order to determine survivability.
In analyzing one particular accident, the TSB wrote the following:
According to past research into accidents with aircraft submerged in water, typically only 10% to 15% of people are able to carry out the required egress actions effectively. Brooks, C.J., MacDonald, C.V., Donati, L., & Taber, J.T. (2008). Civilian Helicopter Accidents into Water: Analysis of 46 Cases, 1979-2006. Aviation, Space, and Environmental Medicine, 79(10), pp. 935-940. Another 10% to 15% of people typically fail to act from the extreme stress, greatly reducing their chance of survival. The remaining 75% may be stunned or shocked by the event; however, most are able to escape successfully if they are well trained and have rehearsed for such an event. Restrictions to normal exits, water temperature, darkness and disorientation following water impact further reduce the ability to egress. Escape training and passenger briefings emphasize the importance of memorizing exit locations. They are clearly identified in the passenger briefing cards; however, anecdotal information suggests few passengers refer to them.
Research has also shown that the ability to hold one’s breath is a key factor in surviving an accident into water. Researchers have concluded that the inability to breath-hold has resulted in the 15% to 50% fatality rate in accidents into water. Hayward, J.S., Eckerson, J.D., & Collis, M.L. (1977). Thermoregulatory Heat Production in Man: Prediction Equation Based on Skin and Core Temperature. J. Appl. Physiol. 42. pp. 377-384. One study indicated that the median breath-holding time of participants immersed in 25°C water was 37 seconds, which dropped dramatically between approximately 5 to 10 seconds in near freezing water temperatures. Cheung, S.S., D’Eon, N.J., Brooks, C.J. (2001). Breath-Holding Ability of Offshore Workers Inadequate to Ensure Escape from a Ditched Helicopter. Aviation Space and Environmental Medicine; 72, pp. 912-918. … The use of an underwater breathing apparatus by properly trained occupants can extend the time available to egress a submerged aircraft.
If an individual is successful in escaping an aircraft that has impacted deep water, continued survival is a significant concern. The TSB Safety Study on Survivability in Seaplane Accidents (SA9401) suggests it is unlikely that persons faced with the urgency of escape in water will retrieve the life vests stored in the aircraft. Without a life vest, considerable amounts of energy are expended to remain above the surface. This physical effort can result in the loss of body heat, fatigue and eventual drowning. Survival without a life vest is further complicated by injuries.
The mechanics of an accident also raise important legal issues. For example, how “crashworthy” was the aircraft? We expect that the cars we drive in are able to protect us in a crash – modern cars have crumple zones and airbags. Unfortunately, few aircraft incorporate those features.
The FAA recognizes this, and in its publication on Seaplane Operations, instructs pilots as follows:
NORMAL AND UNUSUAL EXITS The briefing should include specifics of operating the cabin doors and emergency exits, keeping in mind that this may need to be done without the benefit of vision. Doors and emergency exits may become jammed due to airframe distortion during an accident, or they may be too hard to open due to water pressure.
FAA-H-8083-23-4, sec. 8-8.
The adequacy of a preflight passenger safety briefing may be covered by a legal doctrine called “preemption”. Any attorney handling an aviation case should be well versed in the doctrine of preemption.
Cold water survivability issues can have a large impact on the litigation that follows. I have used the provisions of maritime (admiralty) law to change the standards of liability and damages available in the cases we litigate.
Jimmy Anderson is an Attorney with Krutch Lindell Bingham Jones, representing victims of aviation accidents and other aviation related incidents.