In the past years, for HEMS operations the number of helicopter accidents increased significantly. This is partly caused
by an increase in the number of operations but it was also caused by the fact that the operators have been trying to extend
the operation time and the operating conditions of the helicopter into the night and into adverse weather conditions.
Based on this fact, the NTSB has started a concerted effort "to improve the safety of emergency medical services
The project "Pilot Assistance System for Helicopters" which was started in 2003 and funded by the German Federal
Ministry of Economics and Technology tried to find solutions to exactly these types of problems. The project should
provide an electronic system which improves the situational awareness of the pilot and support the pilot in routes
planning considering all external and internal constraints. It should monitor the execution of the helicopter flight during
the mission taking care of all hazards like terrain, obstacles, bad weather zones, air traffic and airspace restrictions. The
system developed was called PILAS and included a projection of the current environmental situation of the helicopter
into the future as well as a module for proposing alternate solutions for avoiding hazardous situations. During all phases
of the flight the system should be an alerted assistant to the pilot.
In Germany as well as in numerous other countries the air rescue system has been extended significantly since the first operation of the rescue helicopter Christoph 1. The primary target of the air rescue system was to guarantee fast and efficient emergency medical services for victims of accidents. During the years, the scope of the helicopter operations has been extended not only to other types of emergency medical services, but also to secondary medical services like the displacement of patients from hospitals to special service hospitals. While in general the displacement of patients is operated from well known and registered helipads, the primary rescue service currently has to rely on available onboard systems only. Those operations are risky and challenging for the pilots because of time pressure and the danger of obstacles in the environment of the helicopter. In addition, reduced visibility due to fog, rainfall or low light levels can further increase the risks or can make the services unavailable at all. Almost one decade ago, Eurocopter started the investigation of technologies and systems that could help the pilots to perform their tasks with reduced workload and risk, and to allow for a 24 h operation of helicopters irrespective of the weather conditions. After a number of preliminary studies, in 1995 the research program 'All-weather helicopter' has been started as a joint effort of Eurocopter and the supplier industry in Europe. The first phase of the program has been successfully completed in 1999 and the second phase is currently in progress.
Currently available radar instruments are not capable of guiding a helicopter pilot safely during approach and landing under poor visibility conditions. This is due to lack of resolution and lack of elevation information. The RADAR technology that promises to improve this situation is called ROSAR, which stands for Synthetic Aperture Radar based on ROtating Antennas. In 1992 Eurocopter and Daimler- Benz Aerospace investigated the feasibility of an imaging radar based on ROSAR technology. The objective was to provide a video-like image with a resolution good enough to safely guide a helicopter pilot under poor visibility conditions. ROSAR proved to be especially well suited for this type of application since it allows for a stationary carrier platform: Rotating arms with antennas integrated into their tips can be mounted on top of the rotor head. In this way the scanning region of the antennas can cover 360 degree(s). While rotating, the antenna scans the environment from various visual angles without assuming a movement of the carrier platform itself. The signal is then processed as a function of the rotation angle of the antenna movement along a circular path. A radar system of this type is now under development at Eurocopter and Daimler-Benz Aerospace: HeliRadar. HeliRadar is designed as a frequency modulated continuous wave radar working in a frequency band around 35 GHz. The complete transmitter/receiver system is fixed mounted on top of the rotating axis of the helicopter. The received signals are transferred through the center of the rotor axis down into the cabin of the helicopter, where they are processed in a high performance digital signal processor (processing power: 10 GFLOPS). First encouraging results have been obtained from an experiment with `slow motion' movement of the antenna arm.
In 1992 Eurocopter Deutschland and Daimler-Benz Aerospace started a research program to investigate the feasibility of a piloting radar based on the so-called ROSAR technology: HELIRADAR. While available radar instruments are not capable of guiding a helicopter pilot safely under poor visibility conditions due to lack of resolution and lack of height information, ROSAR technology, a Synthetic Aperture Radar based on ROtating antennas, has been the promise to overcome these deficiencies. Based on ROSAR technology HELIRADAR has been designed to provide a video-like image whose resolution is good enough to safely guide a helicopter pilot under poor visibility conditions to the target destination. To yield very high resolution a similar effect as for Synthetic Aperture Radar systems can be achieved by means of a rotating antenna. This principle is especially well suited for helicopters, since it allows for a stationary carrier platform. Additional rotating arms with antennas integrated in their tips are mounted on top of the rotating rotor head. While rotating, the antenna scans the environment from various visual angles without assuming a movement of the carrier platform itself. The complete transmitter/receiver system is fixed mounted on top of the rotating axis of the helicopter. The antennas are mounted at the four ends of a cross and rotate at the same speed as the rotor. The received radar signals are transferred through the center of the rotor axis down into the cabin of the helicopter, where they are then processed in the PolyCluster type high performance digital signal processor.