Rotorcraft Loss of Control In-Flight – The need for research to support increased fidelity in flight training devices, including analogies with upset recovery for fixed-wing aircraft

A review of the worldwide commercial jet fleet accident data, 2001 – 2010, showed that the largest single factor leading to fatalities was Loss of Control In-Flight (LOC-I). 20 such accidents occurred during this timeframe with over 1800 fatalities [1], highlighting the need for research to investigate the causes of this problem and to develop new regulations and training programmes to improve flight safety. For civil helicopter operations, the need to significantly reduce accident rates has been the focus of the International Helicopter Safety Team (IHST), which was formed in 2005 to address factors affecting the “unacceptable” helicopter accident rate. The Team’s mission was to facilitate an 80% reduction in accident rates by 2016. From 2006 to 2011, a team completed a review of 523 U.S. helicopter accidents, from which LOC-I was cited as the main factor in accidents; LOC-I was evident in 217 (41%) of the accidents [2]. Addressing LOC-I for fixed-wing aircraft, the Royal Aeronautical Society’s Flight Simulation Group (FSG) 2009 Spring Conference was entitled: ‘Flight Simulation: Towards the Edge of the Envelope’, during which Upset Prevention and Recovery Training (UPRT) was highlighted as a major potential contributor to enhanced aviation safety. During the FSG conference, the International Committee for Aviation Training in Extended Envelopes (ICATEE) was formed to deliver a long-term strategy for reducing the rate of LOC-I accidents and incidents through enhanced UPRT [3]. To achieve this, ICATEE created two streams: the Training and Regulations Stream addressing the development of a UPRT training requirements matrix, and the Research and Technology Stream performing a thorough analysis of the technological requirements for UPRT. Key recommendations from the ICATEE work included better use of existing simulators for training, and aerodynamic enhancements to simulators to include stall characteristics. The impact of the ICATEE work is that their recommendations resulted in a new ICAO publication, “Manual on Aeroplane Upset Prevention and Recovery Training” [4]. National Authority regulations have also been impacted, with EASA UPRT requirements expected to be complete by May 2019 and the FAA requiring all Part 121 pilots to be UPRT-trained by March 2020. For the rotorcraft community, an equivalent safety initiative has recently been established. In 2016, the US Helicopter Safety Team (USHST) began the analysis of 104 fatal helicopter accidents (2009–2013) to develop intervention strategies and produce Helicopter Safety Enhancements (H-SE) that would further reduce rotorcraft accident rates. The USHST analysed accidents where LOC-I occurred during basic manoeuvres (e.g., hover, quick stop) and during unsuccessful attempted recoveries from potentially unsafe conditions (e.g., loss of tail rotor effectiveness, settling with insufficient power). Helicopter Safety Enhancement (H-SE) 81 titled, “Improve Simulator Modeling for Outside-the-Envelope Flight Conditions” [5] was established to “improve the accuracy of full flight simulators (FFS)/flight training devices by providing recommendations for developing better mathematical/physics-based models for helicopter flight dynamics”. The goal is to “achieve more realistic, higher-fidelity simulations of outside-the-envelope flight conditions” and to examine the “possible use of simulation for purposes of preventing, recognizing, and recovering from spatial disorientation”. Complementing the H-SE 81 initiative, a rotorcraft simulation fidelity research activity is underway at the University of Liverpool and Liverpool John Moores University [6]. The goal of this work is to establish a rational and systematic engineering approach to flight simulation fidelity enhancement, using physics-based models, linking in with goals of H-SE 81. Whilst rotorcraft operations pose different challenges to fixed-wing operations, drawing on the best practices developed by the fixed-wing safety community could benefit the rotorcraft community by reducing the time to implement new safety regulations and develop new training programmes. The presentation will provide an overview of the critical success factors of the ICATEE work, will report on the rotorcraft fidelity research ongoing in Liverpool, highlighting challenges and opportunities involved in developing simulator-based training for rotorcraft LOC-I scenarios

Identification of the mechanical properties of tires for wheelchair simulation.

The development of high performance wheelchairs and wheelchair simulators requires dynamic models taking into account the properties of tires. In this paper the properties of two wheelchair tires are measured by means of a rotating disc testing machine and are compared with the properties of bicycle tires, which have similar dimensions and structure. Tests are carried out considering variations in speed, inflation pressure and load. The possibility of fitting experimental results with the Magic Formula, the Dugoff formula and a linear model is discussed. A dynamic model of a wheelchair is developed, which includes a linear tire model derived from experimental results. Steady turning and slalom manoeuvres are simulated. Numerical results show the effect of tire properties on the handling characteristics of the wheelchair.N/

Review of flight simulation fidelity requirements to help reduce ‘rotorcraft loss of control in‑flight’ accident rates

This paper examines the fidelity requirements for flight simulators to improve training and address the problems associated with rotorcraft loss of control in-flight (LOC-I). To set the context, trends in rotorcraft accident statistics are presented. The data show that, despite recent safety initiatives, LOC-I rotorcraft accidents have been identified as a significant and growing contribution to accident rates. In the late 1990s, the fixed-wing commercial aircraft community faced a similar situation relating to upset prevention and recovery, and through a coordinated international effort, developed a focussed training programme to reduce accident rates. Lessons learned from the fixed-wing programme are presented to highlight how improved rotorcraft modelling and simulation tools are required to reduce rotorcraft accidents through higher quality, simulator-based training programmes. Relevant flight simulator certification standards are reviewed, with an emphasis on flight-model fidelity and vestibular motion cueing requirements. The findings from rotorcraft modelling and motion cueing research, that highlight relevant fidelity issues, are presented to identify areas for further activities to enhance the fidelity of simulators standards for use in LOC-I prevention training

Design of the DLR AVES Research Flight Simulator

The German Aerospace Centre DLR in Braunschweig has developed a reconfigurable flight simulator for research into rotorcraft and fixed-wing aircraft behavior – the AVES (Air VEhicle Simulator). This new simulator features a common motion platform and interchangeable roll-on/roll-off (RoRo) cockpits enabling rapid turnaround of research activities. Additionally, the cockpits may be used in a fixed-base mode with a separate visual display system. Particular emphasis was placed on achieving high motion and visual cueing performance in this flight simulator, while maintaining the flexibility. The justification for the design, the challenges in its realization, the specific testing procedures, and the applications of the simulation facility will be described in this paper