Survival After Ditching in Motorized Aircraft, 1989-2022.

INTRODUCTION: Although an unintended aircraft landing on water (referred to as ditching) is a rare event, the potential for occupant injury/fatality increases immediately following the event due to adverse conditions. However, to date, few studies have addressed the subject. Herein, ditching events and post-ditching survival were investigated.METHODS: Ditchings (1982-2022) in the United States were identified from the National Transportation Safety Board database. Occupant injury severity, aircraft type, pilot experience, flight conditions, and number of occupants were extracted. Poisson distribution, the Chi-squared test (2-tailed), Mann-Whitney U test, and Kruskal-Wallis one-way analysis of variance were employed.RESULTS: A total of 96 ditchings were identified. A systematic survey was hampered by the lack of a standardized reporting matrix in the reports. In total, 77 reports were included in the analysis. Across all ditchings, 128 of 169 (76%) occupants survived ditching and were rescued. Importantly, the initial ditching event was survived by 95% of all occupants. However, 32 (19%) occupants died post-ditching by drowning (21/32 cases) or for undetermined reasons. Considering probability per ditching event, in 26 (34%) of all ditchings, one or more occupants was/were fatally injured.DISCUSSION: Initial survival of the emergency ditching is high. Drowning was the leading cause of death after ditching and reduced the overall survival to 76%. Further investigation is needed to identify risk factors for fatal outcomes and/or improve probability of survival after ditching.Schick VC, Boyd DD, Hippler C, Hinkelbein J. Survival after ditching in motorized aircraft, 1989-2022. Aerosp Med Hum Perform. 2024; 95(5):254-258.

Deficient Aeronautical Decision-Making Contributions to Fatal General Aviation Accidents.

INTRODUCTION: General aviation (GA), mainly comprised of light (≤12,500 lb) aircraft, maintains an inferior safety record compared with air carriers. To improve safety, aeronautical decision-making (ADM) practices have been advocated to GA pilots since 1991. Herein, we determined the extent to which GA pilots disregard such practices.METHODS: Fatal accidents (1991-2019) involving private pilots (PPLs) in single-engine airplanes were identified (N = 1481) from the National Transportation Safety Board AccessR database. Of these, deficient go/no-go and in-flight ADM-related mishaps were scored using the PAVE (pilot, aircraft, environment, external pressure)/IMSAFE (illness, medicine, stress, alcohol, fatigue, eating) and PPP (perceive, process, perform) models, respectively. Statistical testing used Poisson distributions, Fisher exact tests, and Mann-Whitney U-tests.RESULTS: Of the 1481 accidents, 846 were identified as deficient ADM-related. Electing to depart into a hazardous environment (PAVE), disregarding wellness (IMSAFE), and poor aircraft familiarity (PAVE) represented the most common categories (54%, 21%, and 20%, respectively) of errant go/no-go ADM. A 64% decline in fatal accidents related to errant go/no-go decisions for the environment category was evident over the 30-yr period, with little decrements in the other domains. Within the errant environment-related category accidents, the decision to depart into forecasted adverse weather (e.g., degraded visibility, icing, thunderstorms) constituted the most prevalent subcategory (56%, N = 195). Surprisingly, of this subcategory, accidents were overrepresented by over nine- and threefold for instrument-rated PPLs disregarding icing and thunderstorm forecasts, respectively.CONCLUSION: With little decrement in ADM-related accidents in the pilot, aircraft, and external pressure domains, new strategies to address such deficiencies for PPLs are warranted.Boyd DD, Scharf MT. Deficient aeronautical decision-making contributions to fatal general aviation accidents. Aerosp Med Hum Perform. 2023; 94(11):807-814.

Use of flight tracking data to inform safety deficiencies for general aviation cross-country operations in challenging flying environments.

BACKGROUND: Air carriers, but not general aviation, have long employed in-flight data to identify risks/implement corrective measures for improved safety. Herein, using in-flight data, aircraft (in non-instrument-rated private pilots (PPLs) ownership) operations in two potentially hazardous environments (mountains, degraded visibility) were researched for safety practice deficiencies. Four questions were posed, the first two related to mountainous terrain operations: were aircraft (a) flown with hazardous ridge-level winds, (b) within gliding distance of level terrain? Regarding degraded visibility, did aviators (c) depart with low cloud ceilings (≤3,000 ft.), (d) fly at night away from urban lighting? METHODS: The study cohort comprised: (a) single engine aircraft in sole PPL proprietorship (b) registered in Automatic Dependent Surveillance-Broadcast (ADS-B-Out) equipage-required locations prone to low cloud ceilings in three mountainous states. ADS-B-Out data for cross-country flights (>200 nm) were collected. RESULTS: 250 flights (50 airplanes) were tracked (spring/summer 2021). For aircraft transiting areas subject to mountain winds influences, 65% completed one/multiple flights with potentially hazardous ridge-level winds. Two thirds of airplanes traversing mountainous topography would have, for at least one flight, been unable to glide to level terrain with a powerplant failure. Encouragingly, flight departures for 82% of the aircraft were with >3,000 ft. cloud ceilings. Likewise, flights for >86% of the study cohort were undertaken during daylight. Employing a risk scale, operations for 68% of the study cohort did not exceed low-risk (i.e., ≤1 unsafe practice) and high-risk flight(s) (three concurrent unsafe practices) were rare (4% of airplanes). In log-linear analysis, no interactions were evident between the four unsafe practices (p = 0.602). DISCUSSION: Hazardous winds and inadequate engine failure planning were identified as safety deficiencies for general aviation mountain operations. PRACTICAL APPLICATION: This study advocates for the expanded use of ADS-B-Out in-flight data to inform safety deficiencies/implement corrective measures toward improving general aviation safety.

General Aviation Flight Safety During the COVID-19 Pandemic.

BACKGROUND/OBJECTIVE: The COVID-19 virus has caused over 582,000 deaths in the United States to date. However, the pandemic has also afflicted the mental health of the population at large in the domains of anxiety and sleep disruption, potentially interfering with cognitive function. From an aviation perspective, safely operating an aircraft requires an airmans cognitive engagement for: 1) situational awareness, 2) spatial orientation, and 3) avionics programming. Since impaired cognitive function could interfere with such tasks, the current study was undertaken to determine if flight safety for a cohort of single engine, piston-powered light airplanes was adversely affected during a period of the pandemic (MarchOctober 2020) prior to U.S. approval of the first COVID-19 vaccine. METHODS: Airplane accidents were per the National Transportation Safety Board Access ^{database. Fleet times were derived using Automatic Dependent Surveillance-Broadcast. Statistics used Poisson distributions, Chi-squared/Fisher, and Mann-Whitney tests. RESULTS: Little difference in accident rate was evident between the pandemic period (MarchOctober 2020) and the preceding (JanuaryFebruary) months (19 and 22 mishaps/100,000 h, respectively). Similarly, a proportional comparison of accidents occurring in 2020 with those for the corresponding months in 2019 failed to show over-representation of mishaps during the pandemic. Although a trend to a higher injury severity (43% vs. 34% serious/fatal injuries) was evident for pandemic-period mishaps, the proportional difference was not statistically significant when referencing the corresponding months in 2019. CONCLUSION: Surprisingly, using accidents as an outcome, the study herein shows little evidence of diminished flight safety for light aircraft operations during the COVID-19 pandemic. Boyd DD. General aviation flight safety during the COVID-19 pandemic. Aerosp Med Hum Perform. 2021; 92(10):773779.}

Analysis of Air Taxi Accidents (20042018) and Associated Human Factors by Aircraft Performance Class.

INTRODUCTION: Air taxis conduct nonscheduled transport and employ aircraft in various performance categories hereafter referred to as low, medium, and high performance, respectively. No study has yet addressed fixed-wing air taxi safety by performance category. Herein, we compared accident rates/occupant injury across air taxi airplane fleets grouped by performance category and identified human factors contributing to fatal accidents for airplanes in that category with the highest mishap rate.METHODS: Accidents (20042018) in the United States were identified from the National Transportation Safety Board database. General Aviation/Part 135 Activity Surveys provided annual fleet times. Fatal accident contributing factors were per the Human Factors Classification System (HFACS). Statistics utilized Poisson distributions, Chi-Square/Fisher, and Mann-Whitney tests.RESULTS: There were 269 air taxi mishaps (53 fatal) identified. Over the 15 yr, the accident rate (1.10/million flight hours-all categories) declined 50%, largely due to a reduction in medium/high performance category airplane crashes. However, little temporal change was observed for low performance airplanes (1.5/million flight hours) and injury severity trended higher. At the aircrew/physical environment levels, HFACS revealed decision (improper choices), skill-based (stick and rudder) and perceptual (night, instrument conditions) errors contributing to > 60% of fatal accidents involving low performance airplanes. At the organizational level, failing to correct problems, time pressures, and incentive systems contributed to 16% of fatal mishaps.CONCLUSION: Safety deficits remain for the low performance category air taxi fleet warranting increased pilot instrument flight training/utilization of the mandatory 3-axis autopilot in degraded visibility. Safety culture improvements to address issues of personnel/equipment/training deficiencies, failing to correct problems, and time pressures/a safety-compromising incentive system all need to be addressed.Budde D, Hinkelbein J, Boyd DD. Analysis of air taxi accidents (20042018) and associated human factors by aircraft performance class. Aerosp Med Hum Perform. 2021; 92(5):294302.

A comparison of general aviation accidents involving airline pilots and instrument-rated private pilots.

INTRODUCTION: The extremely low accident rate for U.S air carriers relative to that of general aviation (∼1 and ∼60/million flight hours respectively) partly reflects advanced airman certification, more demanding recurrency training and stringent operational regulations. However, whether such skillset/training/regulations translate into improved safety for airline pilots operating in the general aviation environment is unknown and the aim of this study. METHODS: Accidents (1998-2017) involving airline pilots and instrument-rated private pilots (PPL-IFR) operating non-revenue light aircraft were identified from the NTSB accident database. An online survey informed general aviation flight exposure for both pilot cohorts. Statistics used proportion testing and Mann-Whitney U tests. RESULTS: In degraded visibility, 0 and 40% (χ2p = 0.043) of fatal accidents involving airline and PPL-IFR airmen were due to in-flight loss-of-control, respectively. For landing accidents, airline pilots were under-represented for mishaps related to airspeed mismanagement (p = 0.036) relative to PPL-IFR but showed a dis-proportionate count (2X) of ground loss-of-directional control accidents (p = 0.009) the latter likely reflecting a preference for tail-wheel aircraft. The proportion of FAA rule violation-related mishaps by airline pilots was >2X (7 vs. 3%) that for PPL-IFR airmen. Moreover, airline pilots showed a disproportionate (χ2p = 0.021) count of flights below legal minimum altitudes. Not performing an official preflight weather briefing or intentionally operating in instrument conditions without an IFR flight plan represented 43% of airline pilot accidents involving FAA rule infractions. CONCLUSIONS: These findings inform safety deficiencies for: (a) airline pilots, landing/ground operations in tail-wheel aircraft and lack of 14CFR 91 familiarization regulations regarding minimum operating altitudes and (b) PPL-IFR airmen in-flight loss-of-control and poor landing speed management. Practical Applications: For PPL-IFR airmen, training/recurrency should focus on unusual attitude recovery and managing approach speeds. Airline pilots should seek additional instructional time regarding landing tail-wheel aircraft and become familiar with 14CFR 91 rules covering minimum altitudes.

Accident Rates, Causes, and Occupant Injury Involving High-Performance General Aviation Aircraft.

BACKGROUND: Spatial disorientation, poor situational awareness, and aerodynamic stalls are often causal/contributory to general aviation accidents. To mitigate against the occurrence of these mishaps Cirrus Aircraft has, since 2002, introduced advanced avionics into their piston airplanes (Cirrus SR20/22). These airplanes are also certificated to more rigorous crashworthiness tests than legacy aircraft approved prior to these standards being codified. Herein, using for comparison two legacy aircraft fleets manufactured prior to 2002, we determined whether a reduced mishap rate for all accidents or relating to the aforementioned causes/contributing factors and/or diminished injury severity for survivable accidents were evident for Cirrus SR20/22 airplanes.METHODS: Accidents (2008-2017) involving Cirrus SR20/22 airplanes (manufactured 2002 or later) and Beechcraft 35/36 (Bonanza) and Mooney 20 models (both manufactured no later than 2001) (14CFR Part 91 rules) were identified (N = 136, 259, 164, respectively) from the NTSB database. Statistical analyses used Poisson distribution/contingency tables/ t- and Mann-Whitney tests.RESULTS: For each year within the 2013-2017 timespan the Cirrus SR20/22 all-accident rate was diminished 39-75% relative to both legacy fleets. Temporally, the fraction of fatal Cirrus SR20/22 accidents, initially higher, declined 50% achieving a lower, or comparable, proportion to the two legacy airframes. Fatal accident rates involving spatial disorientation/situational awareness/aerodynamic stalls were > 80% lower for Cirrus SR20/22 airplanes. For survivable mishaps, Cirrus SR20/22 aircraft showed a lower proportion (0.13 compared with 0.20-0.35) of fatal/serious injuries.CONCLUSION: Toward improving legacy aircraft safety, owners should be encouraged to upgrade their avionics for mitigating against the occurrence of such human-factor-related mishaps and install airbags to minimize injury severity.Boyd DD, Howell C. Accident rates, causes, and occupant injury involving high-performance general aviation aircraft. Aerosp Med Hum Perform. 2020; 91(5):387-393.

Occupant Injury Severity in General Aviation Accidents Involving Excessive Landing Airspeed.

BACKGROUND: Of all phases of flight operations, accidents during landings are the most frequent. Of these, poor speed management during landing has ramifications for injury severity since: 1) impact forces increase as a square of forward velocity; and 2) an aerodynamic stall, associated with inadequate landing speed, imparts high vertical G forces. Herein, the proportion of landing accidents involving deficient airspeed control and occupant injury severity was determined.METHODS: General aviation landing accidents (1997-2016) were identified from the NTSB database. An accident involving high-airspeed (high-energy) was one for which the NTSB cited airplane porpoising, multiple bounces, or floating, whereas an inadequate airspeed related (low energy) mishap was one citing this term or in which an aerodynamic stall occurred. An anonymous online survey of certificated pilots was used to inform landing technique. Statistical analyses used Poisson distribution and Chi-squared tests.RESULTS: Relative to the earliest period (1997-2001), the landing accident rate was undiminished for more recent years (2007-2016). Of 235 accidents, 38% involved high-energy, whereas 4% were inadequate airspeed-related. For the former, 17% resulted in occupants with fatal-serious injuries, twofold higher than for mishaps with no evidence of mis-speed. Of 1392 survey respondents, 73% selected a landing airspeed higher than required for an under-maximum weight airplane.CONCLUSION: For landing accidents involving airspeed mismanagement, those related to excessive energy predominate and are associated with more severe injuries. Two mitigating strategies are advanced: 1) pilot training should discuss landing airspeed adjustment for aircraft weight; and 2) installation of inflatable restraints for reducing injury severity should be encouraged.Boyd DD. Occupant injury severity in general aviation accidents involving excessive landing airspeed. Aerosp Med Hum Perform. 2019; 90(4):355-361.

A comparison of special category light-sport and corresponding type-certificated aircraft safety.

INTRODUCTION: The special category light sport airplane (light sport) sector of general aviation has grown 10-fold in as many years with solo operations requiring only a sports pilot's certificate. With little research on light sport airplane safety, the study objective was to compare light sport and type-certificated airplane accident rates. METHOD: Accidents were identified from the National Transportation Safety Board database. Statistics employed Poisson distribution/proportion analyses/Mann-Whitney U-tests. RESULTS: For the 2009-2015 period, the light sport airplane accident rate (fatal/non-fatal combined) was >15-fold higher than comparable type-certificated aircraft, undiminished over time. The excessive light sport airplane accident rate was associated with inferior airman experience (time-in-type, certification). Mishaps were most frequent during landing (40%) and, of these, nearly half were due to a deficiency in the flare. There were a dis-proportionate number of trainees involved in landing accidents compared with mishaps for other phases of operations. CONCLUSION: Towards improving safety, additional light sport training with emphasis on landings and a focus on the flare and directional control is warranted. PRACTICAL APPLICATION: In the confines of the present study considering that landing mishaps, the most common accident cause, are often related to deficiencies in the flare and loss-of-directional control, instructors should ensure that airmen have mastered these aspects of landing and, for trainees, acquired the appropriate visual monocular cues.

General Aviation Accidents Involving Octogenarian Airmen: Implications for Medical Evaluation.

BACKGROUND: No upper age limit exists at which general aviation pilots are disallowed from exercising their flying privileges. Operating an aircraft, and landing in particular, requires high visual acuity, cognitive function, and eye-hand/foot coordination; i.e., functions which commonly deteriorate with age. No studies have addressed flight safety of airmen ≥ 80 yr of age (octogenarian+ or 80+) or whether such airmen are more landing accident-prone. This research seeks to answer these questions. METHODS: Accidents and private pilot-certificated airmen counts were obtained from the National Transport Safety Board accident database and the U.S. Civil Airmen Statistics, respectively. Contingency tables were used to determine differences in proportions. A Poisson distribution was employed to determine whether airmen count (80+ and 30-39 yr) and their accident rates differed over time. Differences in median values were tested with a Mann-Whitney test. RESULTS: The proportion of airmen 80+ years doubled and their accident rate increased (6 and 11 mishaps/1000 airmen, respectively) between 2002 and 2016. Landing accidents were over-represented for octogenarian+ pilots compared with airmen 30-39 yr (31 and 17%, respectively) and did not reflect inferior experience but were often due to an aircraft flaring deficiency. The proportion of fatal accidents was comparable (11 and 13%, respectively) for the older and younger age cohorts. CONCLUSION: A growing population and a climbing accident rate for octogenarian+ airmen were evident. The disproportionate count of pilots involved in landing mishaps raises a concern for an increase in such mishaps for octogenarian airmen opting for BasicMed due to less restrictive/frequent visual acuity tests.Boyd DD. General aviation accidents involving octogenarian airmen: implications for medical evaluation. Aerosp Med Hum Perform. 2018; 89(8):687-692.

In-Flight Decision-Making by General Aviation Pilots Operating in Areas of Extreme Thunderstorms.

BACKGROUND: General aviation (comprised mainly of noncommercial, light aircraft) accounts for 94% of civil aviation fatalities in the United States. Although thunderstorms are hazardous to light aircraft, little research has been undertaken on in-flight pilot decision-making regarding their avoidance. The study objectives were: 1) to determine if the thunderstorm accident rate has declined over the last two decades; and 2) assess in-flight (enroute/landing) airman decision-making regarding adherence to FAA separation minima from thunderstorms. METHODS: Thunderstorm-related accidents were identified from the NTSB database. To determine en route/arriving aircraft real-time thunderstorm proximity/relative position and airplane location, using a flight-tracking (Flight Aware®) website, were overlaid on a graphical weather image. Statistics employed Poisson and Chi-squared analyses. RESULTS: The thunderstorm-related accident rate was undiminished over the 1996-2014 period. In a prospective analysis the majority (enroute 77%, landing 93%) of flights violated the FAA-recommended separation distance from extreme convection. Of these, 79 and 69% (en route and landing, respectively) selected a route downwind of the thunderstorm rather than a less hazardous upwind flight path. Using a mathematical product of binary (separation distance, relative aircraft-thunderstorm position) and nominal (thunderstorm-free egress area) parameters, airmen were more likely to operate in the thunderstorm hazard zone for landings than en route operations. DISCUSSION: The thunderstorm-related accident rate, carrying a 70% fatality rate, remains unabated, largely reflecting nonadherence to the FAA-recommended separation minima and selection of a more hazardous route (downwind) for circumnavigation of extreme convective weather. These findings argue for additional emphasis in ab initio pilot training/recurrency on thunderstorm hazards and safe practices (separation distance and flight path).Boyd DD. In-flight decision-making by general aviation pilots operating in areas of extreme thunderstorms. Aerosp Med Hum Perform. 2017; 88(12):1066-1072.

A Review of General Aviation Safety (1984-2017).

INTRODUCTION: General aviation includes all civilian aviation apart from operations involving paid passenger transport. Unfortunately, this category of aviation holds a lackluster safety record, accounting for 94% of civil aviation fatalities. In 2014, of 1143 general aviation accidents, 20% were fatal compared with 0 of 29 airline mishaps in the United States. Herein, research findings over the past 30 yr will be reviewed. Accident risk factors (e.g., adverse weather, geographical region, post-impact fire, gender differences) will be discussed. The review will also summarize the development and implementation of stringent crashworthiness designs with multi-axis dynamic testing and head-injury protection and its impact on mitigating occupant injury severity. The benefits and drawbacks of new technology and human factor considerations associated with increased general aviation automation will be debated. Data on the safety of the aging general aviation population and increased drug usage will also be described. Finally, areas in which general aviation occupant survival could be improved and injury severity mitigated will be discussed with the view of equipping aircraft with 1) crash-resistant fuel tanks to reduce post-impact conflagration; 2) after-market ballistic parachutes for older aircraft; and 3) current generation electronic locator beacons to hasten site access by first responders.Boyd DD. A review of general aviation safety (1984-2017). Aerosp Med Hum Perform. 2017; 88(7):657-664.

Rates and causes of accidents for general aviation aircraft operating in a mountainous and high elevation terrain environment.

BACKGROUND: Flying over mountainous and/or high elevation terrain is challenging due to rapidly changeable visibility, gusty/rotor winds and downdrafts and the necessity of terrain avoidance. Herein, general aviation accident rates and mishap cause/factors were determined (2001-2014) for a geographical region characterized by such terrain. METHODS: Accidents in single piston engine-powered aircraft for states west of the US continental divide characterized by mountainous terrain and/or high elevation (MEHET) were identified from the NTSB database. MEHET-related-mishaps were defined as satisfying any one, or more, criteria (controlled flight into terrain/obstacles (CFIT), downdrafts, mountain obscuration, wind-shear, gusting winds, whiteout, instrument meteorological conditions; density altitude, dust-devil) cited as factors/causal in the NTSB report. Statistics employed Poisson distribution and contingency tables. RESULTS: Although the MEHET-related accident rate declined (p<0.001) 57% across the study period, the high proportion of fatal accidents showed little (40-43%) diminution (χ2=0.935). CFIT and wind gusts/shear were the most frequent accident cause/factor categories. For CFIT accidents, half occurred in degraded visibility with only 9% operating under instrument flight rules (IFR) and the majority (85%) involving non-turbo-charged engine-powered aircraft. For wind-gust/shear-related accidents, 44% occurred with a cross-wind exceeding the maximum demonstrated aircraft component. Accidents which should have been survivable but which nevertheless resulted in a fatal outcome were characterized by poor accessibility (60%) and shoulder harness under-utilization (41%). CONCLUSION: Despite a declining MEHET-related accident rate, these mishaps still carry an elevated risk of a fatal outcome. Airmen should be encouraged to operate in this environment utilizing turbo-charged-powered airplanes and flying under IFR to assure terrain clearance.

General aviation accidents related to exceedance of airplane weight/center of gravity limits.

BACKGROUND: Obesity, affects a third of the US population and its corollary occupant weight adversely impacts safe flight operations. Increased aircraft weight results in longer takeoff/landing distances, degraded climb gradients and airframe failure may occur in turbulence. In this study, the rate, temporal changes, and lethality of accidents in piston-powered, general aviation aircraft related to exceeding the maximum aircraft weight/center of gravity (CG) limits were determined. METHODS: Nation-wide person body mass were from the National Health and Nutrition Examination Survey. The NTSB database was used to identify accidents related to operation of aircraft outside of their weight/CG envelope. Statistical analyses employed T-tests, proportion tests and a Poisson distribution. RESULTS: While the average body mass climbed steadily (p<0.001) between 1999 and 2014 the rate of accidents related to exceedance of the weight/CG limits did not change (p=0.072). However, 57% were fatal, higher (p<0.001) than the 21% for mishaps attributed to other causes/factors. The majority (77%) of accidents were due to an overloaded aircraft operating within its CG limits. As to the phase of flight, accidents during takeoff and those occurring enroute carried the lowest (50%) and highest (85%) proportion of fatal accidents respectively. CONCLUSION: While the rate of general aviation accidents related to operating an aircraft outside of its weight/CG envelope has not increased over the past 15 years, these types of accidents carry a high risk of fatality. Airmen should be educated as to such risks and to dispel the notion held by some that flights may be safely conducted with an overloaded aircraft within its CG limits.

Occupant Injury Severity and Accident Causes in Helicopter Emergency Medical Services (1983-2014).

BACKGROUND: Helicopter emergency medical services (HEMS) transport critically ill patients to/between emergency care facilities and operate in a hazardous environment: the destination site is often encumbered with obstacles, difficult to visualize at night, and lack instrument approaches for degraded visibility. The study objectives were to determine 1) HEMS accident rates and causes; 2) occupant injury severity profiles; and 3) whether accident aircraft were certified to the more stringent crashworthiness standards implemented two decades ago. METHODS: The National Transportation Safety Board (NTSB) aviation accident database was used to identify HEMS mishaps for the years spanning 1983-2014. Contingency tables (Pearson Chi-square or Fisher's exact test) were used to determine differences in proportions. A generalized linear model (Poisson distribution) was used to determine if accident rates differed over time. RESULTS: While the HEMS accident rate decreased by 71% across the study period, the fraction of fatal accidents (36-50%) and the injury severity profiles were unchanged. None of the accident aircraft fully satisfied the current crashworthiness standards. Failure to clear obstacles and visual-to-instrument flight, the most frequent accident causes (37 and 26%, respectively), showed a downward trend, whereas accidents ascribed to aircraft malfunction showed an upward trend over time. CONCLUSION: HEMS operators should consider updating their fleet to the current, more stringent crashworthiness standards in an attempt to reduce injury severity. Additionally, toward further mitigating accidents ascribed to inadvertent visual-to-instrument conditions, HEMS aircraft should be avionics-equipped for instrument flight rules flight.

Accident-precipitating factors for crashes in turbine-powered general aviation aircraft.

General aviation (14CFR Part 91) accounts for 83% of civil aviation fatalities. While much research has focused on accident causes/pilot demographics in this aviation sector, studies to identify factors leading up to the crash (accident-precipitating factors) are few. Such information could inform on pre-emptive remedial action. With this in mind and considering the paucity of research on turbine-powered aircraft accidents the study objectives were to identify accident-precipitating factors and determine if the accident rate has changed over time for such aircraft operating under 14CFR Part 91. The NTSB Access database was queried for accidents in airplanes (<12,501lb) powered by 1-2 turbine engines and occurring between 1989 and 2013. We developed and utilized an accident-precipitating factor taxonomy. Statistical analyses employed logistic regression, contingency tables and a generalized linear model with Poisson distribution. The "Checklist/Flight Manual Not Followed" was the most frequent accident-precipitating factor category and carried an excess risk (OR 2.34) for an accident with a fatal and/or serious occupant injury. This elevated risk reflected an over-representation of accidents with fatal and/or serious injury outcomes (p<0.001) in the "non-adherence to V Speeds" sub-category. For accidents grouped in the "Inadequate Pre-Flight Planning/Inspection/Procedure" the "inadequate weather planning" sub-category accounted (p=0.036) for the elevated risk (OR 2.22) of an accident involving fatal and/or serious injuries. The "Violation FARs/AIM Deviation" category was also associated with a greater risk for fatal and/or serious injury (OR 2.59) with "Descent below the MDA/failure to execute the missed approach" representing the largest sub-category. Accidents in multi-engine aircraft are more frequent than their single engine counterparts and the decline (50%) in the turbine aircraft accident rate over the study period was likely due, in part, to a 6-fold increased representation of single engine airplanes. In conclusion, our study is the first to identify novel precursive factors for accidents involving turbine aircraft operating under 14CFR Part 91. This research highlights areas that should receive further emphasis in training/recurrency in a pre-emptive attempt to nullify candidate accident-precipitating factor(s).

Should Charity Air Medical Organizations Require Commercial Certification of Their Pilots?

OBJECTIVE: Fixed wing medical transportation crashes operating under 14 CFR Part 91 show higher fatal outcomes than nonmedical Part 91 flights. Advanced certification may translate into increased safety, yet we know of no charity air medical transportation requiring such certification. Herein, in a retrospective study, we determined whether commercial certification is associated with a reduced fatality rate compared with the less stringent private pilot certificate and accident causes. METHODS: The National Transportation Safety Board accident database was queried for fatal accidents in single-engine aircraft occurring between 2002 and 2012. Poisson and proportion tests were used in statistical analyses. RESULTS: For the period spanning 2002-2012, commercial pilots showed a lower fatality rate. Under visual meteorologic conditions, aerodynamic stall was a frequent cause for fatal accidents affecting both airman cohorts equally. For operations in instrument meteorologic conditions, fatal accidents were most commonly attributed to instrument approach deficiency and spatial disorientation. At night, failure to maintain obstacle/terrain clearance was the most prevalent cause of fatal crashes. CONCLUSION: Our data suggest that charity air medical transportation organizations should encourage their pilots to acquire commercial certification. Furthermore, our study indicates areas in which general aviation training/currency should be directed to reduce fatal accidents.

Occupant injury and fatality in general aviation aircraft for which dynamic crash testing is certification-mandated.

Towards further improving general aviation aircraft crashworthiness, multi-axis dynamic tests have been required for aircraft certification (14CFR23.562) since 1985. The objective of this study was to determine if occupants in aircraft certified to these higher crashworthiness standards show a mitigated fraction of fatal accidents and/or injury severity. The NTSB aviation database was queried for accidents occurring between 2002 and 2012 involving aircraft certified to, or immune from, dynamic crash testing and manufactured after 1999. Only operations conducted under 14CFR Part 91 were considered. Statistical analysis employed proportion tests and logistic regression. Off-airport landings are associated with high decelerative forces; however for off-airport landings, the fraction of fatal accidents for aircraft subject to, or exempt from, dynamic crash testing was similar (0.53 and 0.60, respectively). Unexpectedly, for on-airport landings a higher fraction of fatalities was evident for aircraft whose certification mandated dynamic crash testing. Improved crashworthiness standards would be expected to translate into a reduced severity of accident injuries. For all accidents, as well as for those deemed survivable, the fraction of minor and serious injuries was reduced for occupants in aircraft certified to the higher crashworthiness standards. Surprisingly, the fraction of occupants fatally injured was not decreased for aircraft subject to dynamic crash tests. To shed light on this unexpected finding flight history, airman demographics and post-impact fires for aircraft for which dynamic crash testing is mandatory or exempt was examined. For the former cohort the median distance of the accident flight was nearly 44% higher. Aircraft subject to dynamic crash testing were also involved in a greater fraction (0.25 versus 0.12, respectively) of post-impact fires. Our data suggest that while the more stringent crashworthiness standards have mitigated minor and serious injuries, surprisingly the fraction of occupants fatally injured is unaltered. The unchanged fraction of fatal injuries may reflect partly (a) fatigue associated with longer flight distances and (b) a greater proportion of post-impact fires.

Causes and risk factors for fatal accidents in non-commercial twin engine piston general aviation aircraft.

Accidents in twin-engine aircraft carry a higher risk of fatality compared with single engine aircraft and constitute 9% of all general aviation accidents. The different flight profile (higher airspeed, service ceiling, increased fuel load, and aircraft yaw in engine failure) may make comparable studies on single-engine aircraft accident causes less relevant. The objective of this study was to identify the accident causes for non-commercial operations in twin engine aircraft. A NTSB accident database query for accidents in twin piston engine airplanes of 4-8 seat capacity with a maximum certified weight of 3000-8000lbs. operating under 14CFR Part 91 for the period spanning 2002 and 2012 returned 376 accidents. Accident causes and contributing factors were as per the NTSB final report categories. Total annual flight hour data for the twin engine piston aircraft fleet were obtained from the FAA. Statistical analyses employed Chi Square, Fisher's Exact and logistic regression analysis. Neither the combined fatal/non-fatal accident nor the fatal accident rate declined over the period spanning 2002-2012. Under visual weather conditions, the largest number, n=27, (27%) of fatal accidents was attributed to malfunction with a failure to follow single engine procedures representing the most common contributing factor. In degraded visibility, poor instrument approach procedures resulted in the greatest proportion of fatal crashes. Encountering thunderstorms was the most lethal of all accident causes with all occupants sustaining fatal injuries. At night, a failure to maintain obstacle/terrain clearance was the most common accident cause leading to 36% of fatal crashes. The results of logistic regression showed that operations at night (OR 3.7), off airport landings (OR 14.8) and post-impact fire (OR 7.2) all carried an excess risk of a fatal flight. This study indicates training areas that should receive increased emphasis for twin-engine training/recency. First, increased training should be provided on single engine procedures in the event of an engine failure. Second, more focus should be placed on instrument approaches and recovery from unusual aircraft attitude where visibility is degraded. Third, pilots should be made aware of appropriate speed selection for inadvertent flights in convective weather. Finally, emphasizing the importance of conducting night operations under instrument flight rules with its altitude restrictions should lead to a diminished proportion of accidents attributed to failure to maintain obstacle/terrain clearance.

Causes of fatal accidents for instrument-certified and non-certified private pilots.

Instrument certification (IFR) enhances a pilot's skills in precisely controlling the aircraft and requires a higher level of standards in maintaining heading and altitude compared with the less stringent private pilot certificate. However, there have been no prior studies to compare fatal accident causes for airmen with, and without, this rating, The NTSB accident database was queried for general aviation fatal accidents for private pilots with, and without IFR certification. Exact Poisson tests were used to calculate whether two rate parameters were equal (ratio of 1), normalized to the number of IFR-rated pilots and flight hours in the given time period. Proportion tests were used to determine whether there were significant differences in fatal accident causes between IFR-certified and non-certified pilots. A logistic regression for log-odds success was used in determining the trend and effect of age on fatal accident rates. IFR certification was associated with a reduced risk of accidents due to failure to maintain obstacle/terrain clearance and spatial disorientation for day and night operations respectively. In contrast, the likelihood of fatal accident due to equipment malfunction during day operations was higher for IFR-certified pilots. The fatal accident rate decreased over the last decade for IFR-certified but not for non-IFR-certified private pilots. However, the overall accident rate for IFR-certified private pilots was more than double that of the cohort lacking this certification. Finally, we found a trend for an increased fatality rate with advancing age for both group of pilots. Our findings informs on where training and/or technology should be focused. Both training for aerodynamic stalls, which causes over a quarter of all fatal accidents, should be intensified for both IFR-certified and non-certified private pilots. Similarly, adherence to minimum safe altitudes for both groups of pilots should be encouraged toward reducing the fatal accidents rate due to failure to maintain obstacle/terrain clearance. For night operations, the high percentage of accidents due to spatial disorientation for non-IFR certified airmen suggests that additional training be required for such operations or such flights carry restrictions for this subset of pilots.