Preflight Risk Assessment for Improved Safety in Helicopter Emergency Medical Service Operations.

INTRODUCTION: Adverse weather and poor visual cues are common elements in night-time Helicopter Emergency Medical Service (HEMS) operations contributing to spatial disorientation and fatal accidents. Pilots are required to make weather-related preflight risk assessments to accept or reject a flight. This study's aim was to develop predictive risk assessment tools based on historical accident data to assist the decision-making process.METHODS: We analyzed 32 single-pilot HEMS night-time visual flight rules fatal accidents to identify contributory risk factors. Logistic regression analysis was used to develop prediction nomograms for nonvisual meteorological conditions (non-VMC), cause and nonsurvivable accidents as dependent variables. Risk factors such as temperature dew point spread, elevation difference, and years of HEMS pilot experience, were entered as continuous variables. Flight crew composition, pilot DTE (domain task experience) and flight rule capability, primary missions, and temperature dew point spread were entered as categorical variables. A point scoring matrix transposed model probability to likelihood and consequence severity.RESULTS: The nomograms correctly predicted the likelihood of entering non-VMC, accident cause, and sustaining a nonsurvivable accident in 75%, 55%, and 94% of cases, respectively. Using data from a recent nonsurvivable HEMS accident, the nomogram estimated a 92% probability (Very Likely) of nonsurvivable accident if visual cues were lost.CONCLUSION: These nomograms can provide preflight information to predict the likelihood of adverse safety outcomes occurring during a planned HEMS mission. While further development work is needed, this approach has the potential to improve HEMS operational safety.Aherne BB, Zhang C, Chen WS, Newman DG. Preflight risk assessment for improved safety in Helicopter Emergency Medical Service operations. Aerosp Med Hum Perform. 2019; 90(9):792-799.

Systems Safety Risk Analysis of Fatal Night Helicopter Emergency Medical Service Accidents.

INTRODUCTION: In the United States, the proportion of Helicopter Emergency Medical Service (HEMS) fatal accidents remained unchanged despite an overall decreasing accident rate. Previous research showed night HEMS operations influenced fatal outcomes. Pilots with <6 yr of HEMS domain task experience (low-DTE) had a higher likelihood of a night operational accident in conditions associated with adverse weather. This study sought to determine whether a difference existed between day and night fatal accident rates and identify influences contributing to night fatal HEMS accidents. Any risk factors identified will be used for a risk analysis to inform future operational safety of the night visual flight rule (VFR) HEMS transport system.METHODS: Historical accident data and industry hours were obtained. Both pilot DTE groups (low and high) and mission VFR and instrument flight rule (IFR) capability were identified using data from 32 night VFR operational fatal HEMS accidents. Accidents were stratified by loss of control and controlled flight into terrain, pilot DTE, and flight rule capability. The effectiveness of both DTE groups and both flight rule capabilities were measured using system safety risk analysis techniques.RESULTS: Night fatal accident rates were statistically different from daytime. Low-DTE pilots and the VFR capability combination had the highest likelihood of night operational nonsurvivable accident.CONCLUSION: Low-DTE pilots and the VFR capability were the least effective mission combination to avoid hazardous conditions at night and maintain spatial orientation, respectively. The analysis identified measures to reduce likelihood of night fatal operational accidents.Aherne BB, Zhang C, Chen WS, Newman DG. Systems safety risk analysis of fatal night Helicopter Emergency Medical Service accidents. Aerosp Med Hum Perform. 2019; 90(4):396-404.

Pilot Decision Making in Weather-Related Night Fatal Helicopter Emergency Medical Service Accidents.

INTRODUCTION: In the United States, between 1995 and 2013, night-time visual flight rules (VFR) Helicopter Emergency Medical Service (HEMS) fatal accidents mostly encountered adverse weather, and pilots with <6 yr of HEMS experience showed higher likelihood of a night operational accident. One adverse weather indicator is cloud-ceiling likelihood indicated by temperature dew point spread (TDPS). This study investigated the relationship between TDPS and HEMS pilot years of experience. It was hypothesized pilots with <6 yr HEMS experience were associated with fatal outcomes encountered at lower TDPS. METHODS: Between 1995 and 2013, 32 single pilot night VFR HEMS fatal accidents occurring in the United States, caused by controlled flight into terrain or loss of control, were analyzed. Using Federal Aviation Administration weather guidance, the 0-4°C TDPS was selected as an indicator of cloud ceiling. Each flight's TDPS was analyzed with pilots' HEMS domain task experience. RESULTS: There were 27 flights which entered the 0-4°C TDPS range; 20 (74%) were significantly associated with adverse weather. A significant negative linear relationship was found between TDPS of each mission and years of pilot HEMS experience (r = -0.423, P = 0.028). Pilots with <6 yr of experience were significantly associated with fatal outcomes (P = 0.049). CONCLUSION: Pilots' incremental years of HEMS experience were associated with a TDPS decrement. Fatal outcomes were over nine times higher for pilots with <6 yr of HEMS experience in night VFR operational accidents in those conditions. Interventions for <6-yr pilots are recommended during experience building to prevent likelihood of operational accidents.Aherne BB, Zhang C, Chen WS, Newman DG. Pilot decision making in weather-related night fatal helicopter emergency medical service accidents. Aerosp Med Hum Perform. 2018; 89(9):830-836.

Pilot Domain Task Experience in Night Fatal Helicopter Emergency Medical Service Accidents.

INTRODUCTION: In the United States, accident and fatality rates in helicopter emergency medical service (HEMS) operations increase significantly under nighttime environmentally hazardous operational conditions. Other studies have found pilots' total flight hours unrelated to HEMS accident outcomes. Many factors affect pilots' decision making, including their experience. This study seeks to investigate whether pilot domain task experience (DTE) in HEMS plays a role against likelihood of accidents at night when hazardous operational conditions are entered. METHODS: There were 32 flights with single pilot nighttime fatal HEMS accidents between 1995 and 2013 with findings of controlled flight into terrain (CFIT) and loss of control (LCTRL) due to spatial disorientation (SD) identified. The HEMS DTE of the pilots were compared with industry survey data. RESULTS: Of the pilots, 56% had ≤2 yr of HEMS experience and 9% had >10 yr of HEMS experience. There were 21 (66%) accidents that occurred in non-visual flight rules (VFR) conditions despite all flights being required to be conducted under VFR. There was a statistically significant increase in accident rates in pilots with <2 and <4 yr HEMS DTE and a statistically significant decrease in accident rates in pilots with >10 yr HEMS DTE. CONCLUSION: HEMS DTE plays a preventive role against the likelihood of a night operational accident. Pilots with limited HEMS DTE are more likely to make a poor assessment of hazardous conditions at night, and this will place HEMS flight crew at high risk in the VFR night domain.