Fog, blizzards, gusts of wind - poor weather can often make the operation of rescue helicopters a highly risky business, and sometimes even impossible. A new helmet-mounted display, developed by researchers at the Technical University of Munich (TUM), may in the future be able to help pilots detect hazards at an early stage, even when their visibility is severely impaired: the information required to do this is created in an on-board computer and imported into digital eye glasses. A new study has shown that this augmented reality improves the performance of pilots.

Thick clouds hang over the Tegernsee. The range of sight is just a few hundred meters. Under normal circumstances, a helicopter would not be allowed to take off in such weather - the danger that the pilot would not be able to react in time to a construction crane, a power line or a mountain would be too great. But this does not stop Franz Viertler from entering the cockpit. Thanks to his head-mounted display - digital eye glasses attached to his head that display additional information - Viertler can detect hazards and navigate around them, even in thick fog.

The new technology is still in the research stage: the Alpine foothills are a projection, Viertler is not a pilot, but a TUM engineer and he is not really operating an actual helicopter, rather a flight simulator. Yet that is all you need to demonstrate the possibilities of augmented reality - a type of reality enhanced by additional information in digital form.

The rotor purrs, the cockpit vibrates, clouds approach and obscure the view. Nevertheless, Viertler knows exactly where he is: the head-mounted display paves the way with green lines representing the outlines of mountains and houses. A red outline in between depicts wind turbines, construction cranes and high buildings.

Many realities, one goal: safety
"Our goal is to increase safety for pilots using augmented reality," explains the researcher. Together with his colleagues at the Institute of Helicopter Technology, he has developed software that combines terrain information with sensor readings that can be taken during a flight. Light Detection and Ranging, LIDAR for short, has proved especially useful here, stresses Viertler: the measuring instruments that can be attached to the helicopter's skids emit radiation in the micrometer range and detect the waves reflected by hazards or obstacles.

All of the data is processed on-board and projected directly to the see-through head-mounted display. This allows the pilot to not only see what he can detect with his own eyes, but also the digitally-generated outlines of the landscape and potential obstacles. Furthermore, flight data, such as speed, altitude, position and course, can also be displayed. In addition, a head-tracking system ensures that the projections adjust to the pilot's line of sight - depending on whether he is looking forward, downward or out the side of the cockpit.

The right amount of information
Does all of this information really help the pilot? To answer this question, the TUM researchers conducted a study with 16 professional helicopter pilots. They were allowed to test the new head-mounted display during various simulator flights. The engineers recorded how the participants flew and queried them afterward on their stress symptoms.

Viertler recently presented the results to the members of the American Helicopter Society in West Palm Beach, Florida: for ranges of sight below 800 meters, the pilots benefited measurably from the terrain and flight data displayed. They not only flew more quickly and more safely than without the head-mounted display, but they also felt that the flights had been less demanding both physically and mentally. The advantages of the system really came to bear when visibility was extremely poor, e.g. in visual ranges of just 100 to 400 meters.

Fighting the white-out phenomenon
"The new technology can reduce the risk when helicopters are operated," Viertler is convinced. "The main problem is poor visibility caused by clouds or snow, or dust blown up when taking off and landing. Augmented reality can help to overcome this white-out or brown-out phenomenon."

However, it may take some time before pilots benefit from this in daily practice: the collection, evaluation and projection of the data must first be tested in research helicopters. "We cannot leave that to our simulators," explains Viertler. Here, support from the industry is required. Fortunately, the industry has already shown great interest in this technology.