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Research Questions

  1. What are the trends in military aircraft mishap rates?
  2. What is the significance of aircraft design vintage, age, and certain broad aircraft attributes on mishap rates?

The U.S. Air Force's aircraft inventory is getting older. Aircraft, such as the B-52 and KC-135, were designed and manufactured more than 60 years ago but remain critical elements of the Air Force's force structure. The aging of the fleet and increasing complexity of newer military aircraft have led some officials to worry that the Air Force's fleet is likely to be more prone to incidents that result in a loss of aircraft or, worse, life. At the same time, significant efforts to improve the safety of military aircraft have been pursued. The authors describe trends in aircraft mishap rates to assess the overall impact of these competing factors.

Researchers assembled and analyzed mishap data from the Air Force Safety Center for 55 different types of aircraft in operation since 1950. A mishap is defined as an unplanned, noncombat-related event resulting in death, injury, occupational illness, or damage to or loss of equipment or property, or damage to the environment. The analysis focuses on three classes of mishap events: (1) Class A mishaps, (2) destroyed aircraft, and (3) pilot fatalities. The focus of this analysis is to identify trends in military aircraft mishap rates going back to the 1950s and the significance of aircraft design vintage, age, and certain broad aircraft attributes on mishap rates.

Key Findings

  • Trends in average mishap rates suggest major improvements in flight safety have been achieved, with the greatest rate of improvement occurring in the 1950s and 1960s. The rates of improvement in Class A mishaps and destroyed aircraft, although still meaningful, have been less dramatic since the 1970s. Mishaps involving pilot fatalities, however, have shown a more persistent rate of improvement.
  • As an aircraft mission design ages, mishap rates tend to improve.
  • Aircraft introduced more recently have tended to experience lower mishap rates.
  • Multiengine aircraft tend to experience fewer Class A mishaps and destroyed aircraft when compared with single-engine aircraft, all else equal.
  • There are meaningful differences in the frequency of mishaps across aircraft types over time. Mobility and trainer aircraft experience the lowest mishaps rates.

Recommendations

  • Future research in this area might consider trends in the causes of mishaps (e.g., operator error, failure of systems and electronic parts, quality defects, environmental factors, and design-related problems) to understand the relative importance of different drivers.
  • Readily available data currently do not support this type of analysis over long periods and may only be obtained from conducting detailed case studies of the mishap experience observed for select types of aircraft.
  • Additionally, the development of better measures for the effectiveness of different steps taken to reduce aircraft accidents over time could be pursued using statistical models, such as those developed in this study.

Research conducted by

This research was funded by the U.S. Air Force and conducted by the Resource Management Program within RAND Project AIR FORCE.

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