兰德-美国空军飞机失灵率的趋势（1950–2018年）（英文）-2020.11-16页_263kb

Summary of Trends in U.S. Air Force Aircraft Mishap Rates (1950-2018)

Core Content

This document presents an analysis of U.S. Air Force aircraft mishap rates from 1950 to 2018. It examines how mishap rates have evolved over time and explores the influence of various factors such as aircraft design age, type, and engine configuration on these rates. The findings are based on data from the Air Force Safety Center and are used to support the National Commission on Military Aviation Safety, established in 2019.

Main Findings

• Overall Improvement in Safety: There has been a significant improvement in mishap rates over the past 70 years, with the most substantial reductions occurring in the 1950s and 1960s.
• Decline with Age: Mishap rates tend to improve as the design age of an aircraft increases, though the rate of improvement decreases over time for Class A mishaps and destroyed aircraft.
• Newer Aircraft Perform Better: Aircraft introduced more recently generally experience lower mishap rates.
• Multiengine Aircraft Are Safer: Multiengine aircraft have lower Class A mishaps and destroyed aircraft rates compared to single-engine aircraft.
• Mobility and Trainer Aircraft Are the Safest: These aircraft types have the lowest mishap rates, while fighters and RPAs have the highest.
• Pilot Fatality Rates Decline Consistently: The rate of improvement in pilot fatalities is more consistent over time, with a steady decline.
• RPA and ISR Aircraft Are Safer: RPA and ISR aircraft have lower mishap rates, especially in terms of pilot fatalities, due to their operational nature (e.g., no onboard pilots for RPA).

Key Points from Data Analysis

• Trends in Mishap Rates:

  • Class A mishaps and destroyed aircraft rates show a more significant decline in the early years, with a slower rate of improvement in later decades.
  • Pilot fatality rates show a more consistent decline over time.
  • The average number of aircraft lost per 100,000 flying hours dropped from 23.6 in the 1950s to fewer than one in the 2010-2018 period.

• Statistical Significance:

  • Statistically significant improvements are indicated by ** (99% significance) and * (95% significance) in the data.
  • The t-test results show that the mean annual mishap rates differ significantly between decades, but the magnitude of these differences has slowed over time.

• Factors Influencing Mishap Rates:

  • Flying Hours: Mishaps scale less than proportionally with flying hours, with a 10% increase in flying hours expected to increase mishap rates by approximately 7-8%.
  • Design Age: Mishap rates decrease as design age increases, but the rate of improvement diminishes over time.
  • Aircraft Type: Fighter and RPA aircraft have the highest mishap rates, while mobility and trainer aircraft have the lowest.
  • Design Vintage: The rate of improvement is also influenced by the year the aircraft was first introduced, with an estimated 5-6% reduction in mishap rates per year of design vintage.
  • Single vs. Multiengine: Multiengine aircraft are less likely to be involved in mishaps compared to single-engine aircraft, with a 36% lower likelihood of Class A mishaps and a 33% lower likelihood of being destroyed.

Statistical Modeling

• A negative binomial regression model is used to estimate the effect of various factors on mishap rates.
• The model includes variables such as annual flying hours, design age, design vintage, and aircraft type.
• The model also accounts for single vs. multiengine design and MD dummies (dummy variables for aircraft types).
• The results show that specification 1 (with design age as a polynomial) fits the data better than specification 2, but specification 2 provides additional insights into the effects of aircraft type and design vintage.

Conclusion

The analysis concludes that overall, the U.S. Air Force has made major strides in improving flight safety. While the rate of improvement has slowed in recent decades, the long-term trend is still positive. Factors such as aircraft age, type, and design play a crucial role in determining mishap rates. Continued monitoring and updating of these trends are essential, particularly as the fleet ages and new technologies are introduced.