Causes and Trends in Maintenance-Related Accidents in FAA-Certified Single Engine Piston Aircraft
Journal of Aviation Technology and Engineering
Causes and Trends in Maintenance-Related Accidents in FAA-Certified Single Engine Piston Aircraft
Douglas Boyd 0
Embry-Riddle Aeronautical University
0 University of Texas Graduate School of Biomedical Sciences at Houston , USA
The accident rate for general aviation remains high. While most general aviation accident studies have been pilot-focused, there is little research on the involvement of aircraft maintenance errors. We undertook a study to answer this question. The Microsoft Access database was queried for accidents occurring between 1989 and 2013 involving single engine piston airplanes operating under 14CFR Part 91. Pearson Chi-Square, Fisher's Exact Test, and Poisson probability were used in statistical analyses. The rate of maintenance-related general aviation accidents was 4.3 per million flight hours for the 1989-1993 period and remained unchanged for the most recent period (2009-2013). Maintenance errors were no more likely to cause a fatal accident than accidents unrelated to a maintenance deficiency. Inadequate/improper maintenance (e.g., undertorquing/non-safetied nuts) represented the largest category causal for, or a factor in, accidents. Maintenance errors involving the powerplant caused, or contributed to, most accidents, but did not carry a disproportionate fraction of fatal accidents. Noncertified airframe and powerplant (A&P) aircraft maintenance technicians (AMTs) performed maintenance on 13 out of 280 aircraft involved in maintenance-related accidents. While there is current concern as to the safety of the aging general aviation fleet, the fraction of fatal accidents for aircraft manufactured prior to 1950 was not higher than those manufactured more recently. We conclude that the general aviation accident rate related to maintenance deficiency, while low, is static. Increased emphasis should be placed on tasks involving torquing and improper rigging as well as maintenance related to installation/assembly/reassembly. Whether a maintenance error decision aid plan, shown to reduce maintenance errors at airline facilities, would benefit general aviation deserves consideration.
general aviation accidents; aircraft maintenance; aging general aviation fleet
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About the Authors
Douglas Boyd, PhD Professor, University of Texas, is an active commercial pilot in single- and multiengine aircraft and is IFR-certified. His current projects/
interests focus on the causes of general aviation accidents. Correspondence concerning this article should be sent to .
Alan Stolzer, PhD Professor, Embry Riddle Aeronautical University, holds a PhD in Quality Systems, an Airline Transport Pilot Certificate, and an A&P mechanic
certificate. Dr. Stolzer’s research interests include Safety Management Systems (SMS) and aviation safety programs.
We are grateful to Brad Wacker at the FAA for supplying general aviation flight hours for 1989.
Introduction
General aviation, governed by 14CFR Part 91
regulations, includes all civilian aviation with the exclusion of
operations involving paid passenger transport—the latter
covered under the comparable 14CFR Part 121 and 135
rules. Although accidents for the airlines (14CFR Part 121)
have dramatically declined over recent decades
(Aviation
Safety Institute, 2012; Li & Baker, 2007)
, such a decrease
is not as evident for general aviation, although preliminary
data
(NTSB, 2014b)
indicate a decline for the most recent
year (2013). Still, general aviation accounts for the
overwhelming majority (94%) of civil aviation fatalities
in the United States (Li & Baker, 2007), and represents an
unresolved safety challenge for aviation. Furthermore,
general aviation accidents carry an associated annual cost
of $1.6 to $4.6 billion to individuals and institutions
affected (e.g., family and nonfamily incurring injury and/or
loss of life, insurance companies, accident investigation
costs) when taking into account hospital costs, loss of pay
with a fatal accident, and loss of the aircraft
(Sobieralski,
2013)
. In all likelihood, these costs would be even higher if
litigation costs were assessed as well.
Most studies on general aviation accidents to date
(Bazargan & Guzhva, 2011; Bennett & Schwirzke, 1992;
Groff & Price, 2006; Li & Baker, 1999; Li, Baker,
Grabowski, & Rebok, 2001; Rostykus, Cummings, &
Mueller, 1998; Shao, Guindani, & Boyd, 2014)
have focused
on the pilot either in terms of pilot error, or corresponding risk
factors such as pilot flight experience, certification,
demographics, and flight conditions. This is not surprising since the
airman has been faulted in 55–85% of general aviation
accidents
(Li et al., 2001; Shkrum, Hurlbut, & Young, 1996)
.
Therefore, the remaining general aviation accidents likely
have pilot-independent causes, and it is hypothesized that
maintenance errors represent such a subset. No peer-reviewed
studies on the involvement of aircraft maintenance errors in
general aviation accidents (...truncated)