Final Report Summary - HELISAFE TA (Helicopter Occupant Safety Technology Application)
The HELISAFE TA project aimed to improve the survivability of occupants in case of helicopter crashes and to minimise the risk of severe injuries in both cockpit and cabin. Helicopters are unique in the variety of tasks they can perform and in the types of sites at which they can be carried out. Accidents may occur mainly when lifting off, landing and due to critical manoeuvres at low altitude, often in bad weather conditions. On the other hand, the occupant has a great chance of surviving when flying close to the ground at low velocity. To date, most of the work on helicopter safety has been concentrated on preventing technical failures and crashworthy design for airframe structures (absorbing elements in the sub floor, landing gear and seats). Nevertheless, today's safety equipment in helicopter still consists of passive harnesses and vertical energy-absorbing seats in new helicopters, which cannot reduce the risk of fatal or severe injuries, especially if the impact loads are higher. Since crashworthy structural concepts are now well established, attention has been turned to increased occupant survivability in helicopter crashes based on cockpit and cabin safety through interacting advanced safety equipment. The approach to occupant safety was studied in the European research project HELISAFE TA based on these aspects of helicopter safety.
The scientific issues concerned a better understanding through full-scale tests and computer modelling of helicopters crash dynamics to improve the knowledge of human body limits and injury criteria. In detail these were:
- improve understanding of the overall crash behaviour of the helicopter structure with regard to the occupant, not only the cockpit / cabin in a rigid environment;
- development of appropriate prediction tools, which need to cover the total airframe behaviour, the cabin and occupant in a crash;
- develop supplemental realistic aviation related injury criteria with focus more on the whole occupant;
- application of previous research technology of HELISAFE to further improve the survivability and mitigate severe injuries like offset, second and third impact, side impact effects;
- improve knowledge of the detailed course of helicopter accidents, by the motion analysis of occupants and resulting contacts with the cabin structure;
- consider intelligent crash management concepts able to predict an accident, choose the necessary safety devices before and during a crash and identify post crash scenarios;
- transfer the high level of passive / active safety standard of automobiles into occupant safety in helicopters and tilt rotors and later into fixed wing aircraft;
- make airworthiness recommendations for certification requirements in the future.
The technical objectives can be summarised as follows:
- adaptation of advanced automotive technology where possible and validation of the concepts;
- develop supplemental passive / active restraint systems to protect occupants independent of their weight, size and seat position;
- develop a modified FAA hybrid III dummy (including hardware and instrumentation) appropriate for helicopter crashes;
- integration of safety features (active / passive) into the seat - harness system to get a modular occupant safety system easy for retrofit in new and / or current helicopter types;
- evaluate intelligent adaptive structure elements which either do not exist or need significant improvements regarding the fuselage;
- assess the effectiveness of proposed safety concepts and equipment by using the HELISAFE HOSS concept to simulate occupant response;
- introduce new / advanced safety features in the cockpit and cabin because these topical issues are not addressed by the current airworthiness rules;
- put the HELISAFE sensor concept in concrete terms and show feasibility;
- integration of automotive active safety technologies like adaptive structures, roll bars in the direct occupant environment (seats, panel, sticks, side wall etc.);
- evaluation of unconventionally inflatable features especially intended for aviation use (active seat cushion, harness airbags, inflatable carpets, knee-padding etc.) in order to find alternative solution for occupant protection and compute / demonstrate their advantage;
- application of previous research technology of HELISAFE to further improve the survivability and mitigate severe injuries like offset, second and third impact, side effects.
Special attention was paid to current crash statistics with the aim to reduce major injuries which subsequently may lead to fatalities. A full-scale baseline drop test was carried out in May 2005 with a full-scale helicopter fuselage. The impact scenario applied was determined in order to cover the most typical helicopter accidents. The intention was to get reliable crash data of a real world crash and the accompanying kinematics in order to develop enhanced safety features to protect the occupants in crash cases that have a high probability of occurrence and significance. Based on the measurements during impact the acceleration floor pulses were determined with the aim to decouple the helicopter structure for the forthcoming investigations by using real crash loads.
Two full-scale test rigs were designed and assembled representing the most common helicopter geometry's of the cockpit and cabin area. The geometry incorporates all injury related details of the interior to be as close as possible to the reality. These mock-ups were used for the hardware sled tests where as basic condition current standard safety items were used to validate the HOSS simulation concept and to establish a starting point to compare later improvements.
Based on the substantial injuries found in the documentation of helicopter accident investigations certain additional injury criteria were considered to be relevant for the enhancement of the HELISAFE FAA hybrid III dummy. These criteria with their thresholds defined in the automotive sector were considered for this purpose in order to adequately assess the level of safety in a helicopter environment. Furthermore to cover the majority of the population an additional FAA hybrid III dummy was developed. Both dummies enabled the consortium to measure and assess all relevant areas of injuries by covering 95 % of the adult population. Exhaustive component testing was performed in order to produce validated results with the new dummy. Parameter studies are then carried out to investigate the effectiveness and to optimise the layout of the new developed and proposed safety concept. These were simulated with the cabin / occupant software to evaluate the effectiveness of the enhanced safety features and to verify the safety system concept for crash load scenarios.
The project's main achievements were:
- definition of a crash scenario suitable to carry out a drop test with a full scale helicopter structure;
- execution of a baseline full-scale drop test to establish injury levels with standard safety equipment and to get realistic accident data;
- definition of an advanced helicopter occupant simulation software (HOSS) concept, in particular to extend the modelling capability to include the more complex cabin and cockpit systems, extended safety system concepts and more severe crash scenarios;
- definition of an enhanced HELISAFE FAA hybrid III hardware dummy with enhanced instrumentation for injury assessment under severe crash loads. Determination of a nonstandard dummies (95 percentile) representing the critical occupant size appropriate for helicopter crashes;
- execution of baseline sled tests to determine the state-of-the-art technology in order to compare later the improvement of HELISAFE TA designed safety equipment;
- development of an enhanced restraint system consisting of harnesses, airbags and seats;
- perform parameter studies in order to get an enhanced occupant safety system with high crash survival capabilities;
- conducting final sled tests to confirm the effectiveness of the enhanced HELISAFE TA safety equipment;
- definition and prototyping of a crash sensor system including electronic control unit (ECU);
- execution of a final full-scale drop test to assess and validate the achieved improvement of the safety equipment developed in HELISAFE TA;
- assessment of helicopter safety improvements based on simulation and hardware tests;
- assessment of the HELISAFE TA results with respect to transferability to fixed wing aircraft;
- airworthiness recommendations for future helicopters; if required, authorities will be supported in their rule making process;
- implementation strategy plan for HELISAFE TA advanced technology.
The results may set new standards for aviation safety systems resulting in new specifications. Since United States competitors started some time ago to intensify their research on pilot / passenger survivability, European helicopter manufacturer have to address this subject in order to maintain competitive.
Crushable fuselages of the aircraft lead to non sufficient energy absorption demonstrating that passenger safety is not limited to the aircraft design but depends to a large extend on the safety equipment. Furthermore, accident analysis has shown that restraint systems alone are not sufficient to guaranty survivability. Studies and investigations of crash cases show that in spite of using energy absorbing devices fatalities occurs also within the specified crashworthy range due to main head and upper body injuries. Crashworthy seats capable to sustain a crash case without a loss of their structural integrity may result in an unacceptable dynamic response which a human body is not able to withstand. Energy absorbing devices fitted to crashworthy seats become state-of-the-art in the meantime to modern helicopter and for retro-fit.
HELISAFE TA provides a safety concept which does not yet exist in Europe and a validated numerical simulation tool to predict typical crash scenarios and to simulate the response load on the human body with respect to the interaction of safety equipment. This simulation tool is able to analyse and optimise any cockpit and cabin in respect to response loads to human bodies.
Strengthening the European aeronautical industry this way will create new jobs having a positive influence on social and economic conditions. Spin-offs of the new technologies may be the use in other applications such as but not limited to inflatable passenger restraint systems in helicopter or general aviation aircraft with a broad application.
The scientific issues concerned a better understanding through full-scale tests and computer modelling of helicopters crash dynamics to improve the knowledge of human body limits and injury criteria. In detail these were:
- improve understanding of the overall crash behaviour of the helicopter structure with regard to the occupant, not only the cockpit / cabin in a rigid environment;
- development of appropriate prediction tools, which need to cover the total airframe behaviour, the cabin and occupant in a crash;
- develop supplemental realistic aviation related injury criteria with focus more on the whole occupant;
- application of previous research technology of HELISAFE to further improve the survivability and mitigate severe injuries like offset, second and third impact, side impact effects;
- improve knowledge of the detailed course of helicopter accidents, by the motion analysis of occupants and resulting contacts with the cabin structure;
- consider intelligent crash management concepts able to predict an accident, choose the necessary safety devices before and during a crash and identify post crash scenarios;
- transfer the high level of passive / active safety standard of automobiles into occupant safety in helicopters and tilt rotors and later into fixed wing aircraft;
- make airworthiness recommendations for certification requirements in the future.
The technical objectives can be summarised as follows:
- adaptation of advanced automotive technology where possible and validation of the concepts;
- develop supplemental passive / active restraint systems to protect occupants independent of their weight, size and seat position;
- develop a modified FAA hybrid III dummy (including hardware and instrumentation) appropriate for helicopter crashes;
- integration of safety features (active / passive) into the seat - harness system to get a modular occupant safety system easy for retrofit in new and / or current helicopter types;
- evaluate intelligent adaptive structure elements which either do not exist or need significant improvements regarding the fuselage;
- assess the effectiveness of proposed safety concepts and equipment by using the HELISAFE HOSS concept to simulate occupant response;
- introduce new / advanced safety features in the cockpit and cabin because these topical issues are not addressed by the current airworthiness rules;
- put the HELISAFE sensor concept in concrete terms and show feasibility;
- integration of automotive active safety technologies like adaptive structures, roll bars in the direct occupant environment (seats, panel, sticks, side wall etc.);
- evaluation of unconventionally inflatable features especially intended for aviation use (active seat cushion, harness airbags, inflatable carpets, knee-padding etc.) in order to find alternative solution for occupant protection and compute / demonstrate their advantage;
- application of previous research technology of HELISAFE to further improve the survivability and mitigate severe injuries like offset, second and third impact, side effects.
Special attention was paid to current crash statistics with the aim to reduce major injuries which subsequently may lead to fatalities. A full-scale baseline drop test was carried out in May 2005 with a full-scale helicopter fuselage. The impact scenario applied was determined in order to cover the most typical helicopter accidents. The intention was to get reliable crash data of a real world crash and the accompanying kinematics in order to develop enhanced safety features to protect the occupants in crash cases that have a high probability of occurrence and significance. Based on the measurements during impact the acceleration floor pulses were determined with the aim to decouple the helicopter structure for the forthcoming investigations by using real crash loads.
Two full-scale test rigs were designed and assembled representing the most common helicopter geometry's of the cockpit and cabin area. The geometry incorporates all injury related details of the interior to be as close as possible to the reality. These mock-ups were used for the hardware sled tests where as basic condition current standard safety items were used to validate the HOSS simulation concept and to establish a starting point to compare later improvements.
Based on the substantial injuries found in the documentation of helicopter accident investigations certain additional injury criteria were considered to be relevant for the enhancement of the HELISAFE FAA hybrid III dummy. These criteria with their thresholds defined in the automotive sector were considered for this purpose in order to adequately assess the level of safety in a helicopter environment. Furthermore to cover the majority of the population an additional FAA hybrid III dummy was developed. Both dummies enabled the consortium to measure and assess all relevant areas of injuries by covering 95 % of the adult population. Exhaustive component testing was performed in order to produce validated results with the new dummy. Parameter studies are then carried out to investigate the effectiveness and to optimise the layout of the new developed and proposed safety concept. These were simulated with the cabin / occupant software to evaluate the effectiveness of the enhanced safety features and to verify the safety system concept for crash load scenarios.
The project's main achievements were:
- definition of a crash scenario suitable to carry out a drop test with a full scale helicopter structure;
- execution of a baseline full-scale drop test to establish injury levels with standard safety equipment and to get realistic accident data;
- definition of an advanced helicopter occupant simulation software (HOSS) concept, in particular to extend the modelling capability to include the more complex cabin and cockpit systems, extended safety system concepts and more severe crash scenarios;
- definition of an enhanced HELISAFE FAA hybrid III hardware dummy with enhanced instrumentation for injury assessment under severe crash loads. Determination of a nonstandard dummies (95 percentile) representing the critical occupant size appropriate for helicopter crashes;
- execution of baseline sled tests to determine the state-of-the-art technology in order to compare later the improvement of HELISAFE TA designed safety equipment;
- development of an enhanced restraint system consisting of harnesses, airbags and seats;
- perform parameter studies in order to get an enhanced occupant safety system with high crash survival capabilities;
- conducting final sled tests to confirm the effectiveness of the enhanced HELISAFE TA safety equipment;
- definition and prototyping of a crash sensor system including electronic control unit (ECU);
- execution of a final full-scale drop test to assess and validate the achieved improvement of the safety equipment developed in HELISAFE TA;
- assessment of helicopter safety improvements based on simulation and hardware tests;
- assessment of the HELISAFE TA results with respect to transferability to fixed wing aircraft;
- airworthiness recommendations for future helicopters; if required, authorities will be supported in their rule making process;
- implementation strategy plan for HELISAFE TA advanced technology.
The results may set new standards for aviation safety systems resulting in new specifications. Since United States competitors started some time ago to intensify their research on pilot / passenger survivability, European helicopter manufacturer have to address this subject in order to maintain competitive.
Crushable fuselages of the aircraft lead to non sufficient energy absorption demonstrating that passenger safety is not limited to the aircraft design but depends to a large extend on the safety equipment. Furthermore, accident analysis has shown that restraint systems alone are not sufficient to guaranty survivability. Studies and investigations of crash cases show that in spite of using energy absorbing devices fatalities occurs also within the specified crashworthy range due to main head and upper body injuries. Crashworthy seats capable to sustain a crash case without a loss of their structural integrity may result in an unacceptable dynamic response which a human body is not able to withstand. Energy absorbing devices fitted to crashworthy seats become state-of-the-art in the meantime to modern helicopter and for retro-fit.
HELISAFE TA provides a safety concept which does not yet exist in Europe and a validated numerical simulation tool to predict typical crash scenarios and to simulate the response load on the human body with respect to the interaction of safety equipment. This simulation tool is able to analyse and optimise any cockpit and cabin in respect to response loads to human bodies.
Strengthening the European aeronautical industry this way will create new jobs having a positive influence on social and economic conditions. Spin-offs of the new technologies may be the use in other applications such as but not limited to inflatable passenger restraint systems in helicopter or general aviation aircraft with a broad application.
