Thursday, July 16, 2009
The naval aviation flight deck is a hazardous high noise environment in which current legacy systems are not able to provide sufficient hearing and head protection. Flight deck crew noise exposure levels are among the worst in the world.
The Navy wanted to protect personnel hearing and improve the ability to hear commands accurately in jobs where others’ lives and millions of dollars in aircraft are at stake.
NAVAIR Human Systems Department Chief Scientist James Sheehy, PhD was asked by the Department of Defense Research and Engineering, to host a workshop in which he would invite DoD and international experts to discuss the noise problem that had long plagued flight deck personnel throughout the Navy.
‘‘Rather than hosting a workshop, I suggested an electronic survey of national and international experts to review a research plan to get from the current level of hearing protection, to a level one that would target all our noisier systems in use,” Sheehy said.
The companies that participated in the review (experts from the Netherlands, the United Kingdom and U.S. companies) agreed and supported the approach outlined in the proposed near, mid and far term research plan. Sheehy and Valerie Bjorn, a physiologist with NAVAIR, published the results which were presented to the Joint Aeronautical Commander’s Group.
The research was well-received. Sheehy said he used the funding saved by conducting the electronic survey, rather than a sponsored workshop, to start a tri-service research program to improve aviation personnel hearing protection.
By combining funding assistance from the small business innovative research (SBIR) program, the Office of Naval Research, the Air Force Office of Scientific Research and the JSF, the project became a multi-million dollar program in which ‘‘a structured approach was pursued to improve hearing protection from less than 6 decibels (6dB) of attenuation up to the maximum of 47dB to 53dB,” Sheehy said.
Jill Moore, deputy associate director of the NAVAIR Office of Small Business Programs, facilitated SBIR support for the program and discussed the transition to production. ‘‘We were able to leverage this SBIR technology development program to reduce production risks by using the Defense Department-funded mentor-protÈgÈ program,” she said of the cooperation between prime contractor and their production supplier. By using the mentor-protÈgÈ program funding, Moore said both program offices has benefitted.
The state-of-the-art cranial and hearing protection provided by NAVAIR’s personnel is more than just hearing protection. It also provides compatibility with chemical, biological and radiation clothing, night vision goggles, eyeglasses and communication devices.
The upgraded design can fit a diverse naval population as the system is able to integrate correctly and work on all personnel, regardless of age, gender, race or size.
The deep insert earplugs are fitted to each individual. They are easy to use and maintain and are comfortable for several hours of daily use.
These earplugs are also hand washable in soap and water and are tethered to prevent to possibility of becoming litter or Foreign Object Damage, which is always a problem when working around aircraft.
Development of custom molded earplugs and upgraded ear muffs have been completed and are now available for fleet purchase and provide 29 dB mean attenuation.
‘‘The current flight deck cranial program has two objectives,” says Martin Ahmad, Program Manager for PMA-202, aircraft systems. ‘‘The first is to protect personnel’s head. In the event of a fall or head bump, a person’s cranium would be protected. The second is to enhance the hearing protection from the noisy environment in which maintainers work.”
Ahmad said the cranial protection currently available in the fleet is not good enough so NAVAIR’s research and engineering community has been working to improve this system over the past several years.
The first generation of today’s flight-deck cranial was designed by Capt. Ralph L. Christy Jr., a Navy flight surgeon and David M. Clark, of the David Clark company. They used the ‘‘Mickey Mouse” earmuffs in the original cranial-helmet system. At that time, the state of the art head and hearing protection was worn to protect against the F2H-2 Banshee’s twin Westinghouse J34 turbojet engines, capable of producing 3,140 pounds of thrust each.
When the Navy graduated to the more powerful and noisier F⁄A-18 aircraft, two general electric F-404-GE-402 afterburning engines, capable of 18,000 pounds of thrust each and producing up to 148 dB of noise, was more than the current cranial and hearing protection could safely withstand. Modern aviation-maintenance crews wore the commonly known HGU24⁄P and HGU-25(V)2⁄P crania device.
This design not only failed to meet the modern safety standards for impact protection and electrical shock prevention but also to support several key 21st Century mission scenarios.
‘‘Our program is still in development,” said Ahmad. ‘‘We recently completed critical design reviews for both vendors with production to start in fiscal year 2010. However, the custom molded earplugs and upgraded ‘Mickey Mouse’ ears are fully tested, approved and available.”
A pilot program on USS Eisenhower was recently initiated under which all personnel who work on the flight deck were provided custom molded earplugs and upgraded ‘Mickey Mouse’ ears. Ahmad said the pilot program will provide lessons learned on the use of the custom molded earplug.
The custom-molded ear plug provides a proper fit which achieves the maximum reduction. ‘‘Legacy foamie ear plugs are difficult for many personnel to insert fully, thus not achieving the desired protection,” he said.
Hazardous shortcomings of the current cranial device were first reported by a Navy command master chief, Wynn Young, who developed a point paper that highlighted the cranial’s failure to support a NAVAIR mandate that required the use of night vision devices (NVDs) on amphibious flight decks, as well as the ‘‘can do”spirit of the fleet maintainer.
The document pointed out that fleet solutions often resulted in non-standard, unsafe practice. As an example, the NVD attachment to the cranial often results in poor NVD eye alignment, vision and face hazards, and cracked cranial-impact shields.
NAVAIR’s human systems department conducted a survey of more than 740 flight deck personnel on board several naval vessels and across fleet squadrons. The survey included a detailed assessment of cranial-helmet fit and maintenance condition, earplug use and insertion depth, and head-size measurements.
Worn without earplugs, the cranial provides approximately 21 dB of noise attenuation when correctly fit, adjusted and maintained. All survey subjects reported wearing cranial helmet with earmuffs, but 75 percent of subjects were issued a questionable size and 41 percent of earcup cushions and foam inserts were deteriorated, hard, creased or missing.
Many maintainers, who were issued even the largest of the four cranial sizes, reported being in severe pain after wearing them for five minutes.
A detailed cost analysis found that the cost to build, maintain and replace the old cranial was not cost effective. Survey data showed approximately two hours are required to build one complete cranial system from scratch, with an additional 45 minutes needed to configure NVDs.
As a result, NAVAIR worked with two vendors, Adaptive Technologies, Inc., (ATI), and Creare, Inc., to develop new design concepts. Both vendors developed prototypes designed to meet or exceed initial performance requirements. The Naval Safety Center then hosted multiple open forums with the fleet to gather firsthand feedback of the ATI and Creare prototypes and to overcome certain unmet performance requirements.
In March 2008, the performance specifications were approved. It established minimum performance and validation requirements for a modular helmet to be worn by aircraft handlers and maintainers working in and around military aircraft both onboard ship and ashore. The plan is to issue the new cranial system as an individually-issued item to improve fit, comfort and maintenance.
The program was authorized and is now in the system design and development phase. Both ATI and Creare have conducted laboratory performance validation testing.