Test and Evaluation:

Reducing Risks to Military Aircraft From Bird Collisions

NSIAD-89-127: Published: Jul 13, 1989. Publicly Released: Jul 25, 1989.

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Pursuant to a congressional request, GAO reviewed the services': (1) testing of military aircraft to reduce losses and damages resulting from bird collisions; and (2) development and use of nonflammable hydraulic fluid to reduce fire risks.

GAO found that: (1) between 1983 and 1987, military aircraft collided with birds over 16,000 times, causing the loss of 9 aircraft, 6 crew member fatalities, and $318 million in damage; (2) the services' specifications for testing jet engines against bird collisions served as guidance, rather than as requirements, resulting in the services not always requiring testing or using analytical methods which fully tested against known bird hazards; (3) jet engine testing methods did not always reflect the sizes and numbers of birds that could be ingested; (4) the services did not test airframes to identify and minimize vulnerability to bird collisions; (5) military oversight of engine testing against bird collisions was typically limited to monitoring; and (6) little documentation existed to evaluate the effectiveness of tests against bird collisions. GAO also found that: (1) between 1965 and 1986, hydraulic fluid fires during aircraft accidents have caused at least 5 crew member fatalities, 19 injuries, and $237 million in lost aircraft; (2) the Air Force has developed a nonflammable hydraulic fluid that is not compatible with existing aircraft hydraulic systems; and (3) costs of the Air Force's attempts to develop the nonflammable fluid and new components for hydraulic systems exceeded $21 million through September 1988.

Recommendations for Executive Action

  1. Status: Closed - Implemented

    Comments: According to DOD, a revised test specification has been prepared (MIL-JSGS-87231A) and is in the final approval cycle. Issuance is expected no later than mid-October 1994.

    Recommendation: The Secretary of Defense should require the services to revise test specifications to reflect the sizes and the number of birds actually colliding with military aircraft.

    Agency Affected: Department of Defense

  2. Status: Closed - Implemented

    Comments: The Navy adopted the Air Force specifications for making such evaluations. In addition, more modelling and simulation is being used by the services in their evaluations. Finally, individual aircraft reviews by the services are to evaluate the impacts of bird collisions. Although DOD believes that financial savings will eventually be realized from these actions, no attempts have been made to calculate or project such savings. This is largely due to the extensive time it would take to identify and quantify financial savings.

    Recommendation: The Secretary of Defense should require the services to evaluate the vulnerability of critical airframe areas such as the nose and the wing's leading edges to minimize the risk from bird collisions.

    Agency Affected: Department of Defense


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