March - April 2001 - Aviation Life Support Equipment: Providing Protection

by Maj. Gen. Anthony Jones    and LTC Paul Cain

The Aviation Life Support Equipment Retrieval Program (ALSERP) is based at the U.S. Army Aeromedical Research Laboratory (USAARL) at Fort Rucker, Ala., and for the last 30 years has had one simple mission: to continually improve the protection afforded to military aviators. Ensuring that aviation life-support equipment (ALSE) meets the highest standards provides the best possible chance of survival in an accident and safeguards the health of the crew and passengers who travel in Army aircraft. As the incidence of serious injury is reduced, aviators will spend less time off flight status and, ultimately, human suffering is reduced, costs are minimized and mission effectiveness is optimized. 

                An understanding of the ALSERP process can help every aviator contribute to the success of this program. Some may worry that this is an organization that aims to uncover the misdemeanors committed by aviators. Even if the USAARL investigation uncovers the improper use of ALSE, the aim is to find out why this is happening and then use the findings for continuing education and development, not for retribution.

The Team

                The work is carried out by the USAARL's Aircrew Protection Division (APD). Although the analysis is completed in-house, you can expect to see team members collecting equipment and data at accident sites around the globe.

                The nucleus of this multidisciplinary team is made up of flight surgeons, aerospace and mechanical engineers, aviators and aviation safety professionals. Although this approach is not absolutely unique, there are very few organizations in the world that employ this level of expertise to tackle the problem. If the case is sufficiently complex, further assistance is available from other disciplines within the laboratory, the Department of Defense (DOD), the Federal Aviation Administration (FAA) or industry.

The Challenge

                Accident investigations start with the arrival of initial accident reports from the U.S. Army Safety Center or the unit involved. Ideally, USAARL team members visit all sites to witness first hand the effects of the crash. This is not always possible, however, so the timely passage of information is vital to the success of the investigation. While written reports are important, photographic evidence is always very welcome as it leads to a much clearer understanding of the accident. As the saying goes: "a picture is worth a thousand words."

                Once the available data concerning the accident sequence, crash forces and occupant injuries have been assembled, the detailed USAARL analysis can begin. Helmets are torn down to their component parts, photographed and examined for damage [Figure 1]. They often seem only to have minor surface scrapes, but turn out to be much more seriously damaged on the inside. 

                These permanent impressions in the polystyrene energy-absorbing liner are one of the best guides to the force of the impact [Figure 2]. 

                The next stage of the investigation is to compare this damage with helmets from earlier accidents, or with materials that have undergone controlled tests in the laboratory. The mechanism of injury is determined and an assessment of the protection provided by the helmet is made. Any failure is noted and will lead to the team meeting with system developers and contractors to improve the manufacture and/or design.

                Of course, helmets are only one part of the ALSE that is inspected; clothing, seats, harnesses and survival equipment are also examined [Figure 3]. There is a particular interest in the way current flight clothing protects from the now fortunately rare cockpit fire. Seats are examined in order to determine the amount of energy that has been absorbed, and harnesses are tested by loading the straps until they fail.

Results

                The ALSERP has had many successes over the years. The early work of the team and the application of data from accidents from the Vietnam era revealed a high proportion of burn injuries in older aircraft. This work, combined with that of the U.S. Army Safety Center, was instrumental in improving fire protection through the adoption of crashworthy fuel systems and flight suits made of Nomex instead of cotton. Nomex-backed leather gauntlet gloves have also been added to protect the vulnerable wrist area. 

                During the 1980s fractures in the base of the skull were a common finding following a blow to the side of the helmet.  Investigation revealed that the ear cups could transmit significant force to the skull, so a crushable ear cup was developed. These were incorporated into the SPH-4B, and since then have been a standard feature of Army helmets. 

                Newer helmets such as the HGU-56P (Figure 4) provide better head protection as a result of the improved specifications developed from accident investigations. Early helmets like the SPH-4 had thinner, more dense polystyrene and, as a result, less impact energy was absorbed and injuries were more common. Since then, progressively thicker but less dense linings have been incorporated and, even at higher impact speeds, less than half the crash force is transmitted to the head. Obviously, there will be less chance of injury C but the most important benefit is the ability of a pilot wearing an HGU-56P to remain conscious, despite severe blows to the head, and escape after a crash. The potential for injury has also helped to drive down helmet weight.

                Proper restraint is vitally important in an accident. Although the existing generation of inertia reels lock harnesses in an accident, they do allow some movement.  Because of this, injuries are still seen by investigators.  The most recent designs lock the harness earlier in the accident sequence and should reduce the potential for injury.  These are now being fitted to the current fleet of aircraft.

The Future

                As technologies are introduced to solve old problems, new challenges appear. Stroking seats were developed to reduce the number of aircrew back injuries, but they can also contribute to injury by bringing the chest and face closer to the cyclic. These findings have helped drive the development of cockpit airbags for aircraft, and these are scheduled for fielding in the next few years. Future aircraft can also benefit from the program C the HGU-56P helmet is being developed for the Comanche, for example. Despite a further reduction in weight and additional optical equipment, the helmet specifications set following earlier accident investigation have ensured that the advanced protection remains. 

                Key improvements in ALSE have already been achieved; nevertheless, the program continues on strongly. As in the past, USAARL investigators complete thorough examinations of ALSE from crashed aircraft in order to ensure future aircrew safety. The price of this information on equipment performance is unfortunately measured in human injury, but it has at least resulted in the best possible protective equipment for others. In the unforgiving aviation environment, it is vitally important that all aviators use and maintain their equipment correctly and, as a result, gain the full benefit from the protection. 

MG Anthony R. Jones is commanding general of the U.S. Army Aviation Center at Fort Rucker, Ala., and chief of the aviation branch. LTC Paul Cain is a British Army aviator and flight surgeon currently on exchange with the Aircrew Protection Division of the U.S. Army Aeromedical Research Laboratory at Fort Rucker.