EHEST ranks 15 technologies that improve helicopter safety

The European Helicopter Safety Team lists EGPWS/TAWS as the top accident prevention technology that exists today. EHEST Photo

The European Helicopter Safety Team (EHEST) has released a report conducted for the National Aerospace Laboratory (NLR) about the ways in which technology can help lower the helicopter accident rate. The study, “The Potential of Technologies to Mitigate Helicopter Accident Factors,” is part of the International Helicopter Safety Team (IHST)’s efforts launched in 2005 to reduce the global accident rate 80 percent by 2016. The EHEST established a Specialist Team (ST) for technology in March 2011 that put together the report, which was the subject of a workshop on Oct. 16 during Helitech International in Amsterdam.

According to the study, technology “provides a variety of solutions that can (directly or indirectly) address the identified safety issues and that can contribute to prevent various types of accidents or to increase survivability.”

EHEST identified a list of new and emerging technologies, existing technologies not used on helicopters, and technologies used on large helicopters but not yet on smaller variants to come up with a total of 145 individual technologies that could help reduce accidents. The group then rated 93 of the 145 listings from a scale of 0 to 5 to come up with a “technology matrix tool,” and determined that there are 15 “highly promising” technologies that stand out from the pack.

The combination of the 15 highly promising technologies can help to mitigate 11 of the top 20 safety issues, including: pilot judgment/human factors; situational awareness; part, component or system failure; skill-based errors; terrain and obstacle avoidance; low visibility and bad weather; design flaws; maintenance; and regulations.

At the top of the list of the 15 technologies is an enhanced ground warning system (EGPWS), also known as a terrain awareness and warning system (TAWS). Digital range image algorithms that assist with low-level flight, laser detection and wire strike warning systems, digital maps, and voice/data flight recorders round out the top five. Below is EHEST’s summary of the top 15 technologies:

1. EGPWS/TAWS: Although not a predominant feature of helicopter operations, in-flight collision with other aircraft is inevitably catastrophic and in busy offshore operating areas where air traffic services, communications and weather may be variable, the risks undoubtedly increase. Landing on a helideck is a challenging task, which currently relies heavily on the skill of the pilot and the helideck environment. The risks can be reduced by improving helideck design, standardizing take-off and landing profiles and procedures, and by introducing new equipment. Risks can also be mitigated by installing technological advances such as EGPWS, generically known as TAWS. Such systems can also provide a warning of fixed, land-based obstacle hazards such as towers. Fitment of collision avoidance systems can undoubtedly be justified in busy offshore environments, where the risk of mid-air collision rises.

2. Digital range image algorithms for flight guidance aids for helicopter low-level flight: Low-altitude and terrain-following flights are needed for both civil and military rotorcraft. Carrying out such tasks at low altitude and in poor visibility, whether in daylight or at night-time, can be extremely hazardous. Studies have shown that controlled flight into terrain (CFIT) accidents, including wire strikes, have been of major concern for both civil and military helicopter users. Extensive simulation and flight tests were conducted to develop and test a complete set of algorithms for terrain following or contour flight, and more particularly to improve means of computing a reference obstacle contour line (OCL) for terrain-following flights. All practical experimentation was performed using two actual Lidar OWS (obstacle warning systems). In addition, a wire detection algorithm was designed and simulation tested using real flight test data.

3. Laser radar obstacle and terrain avoidance systems: Wire strikes have been a major concern for both civil and military helicopters. In addition to wire strike protection devices, there are a number of devices that warn the pilot about the proximity of wires. This specific system uses an eye-safe laser that is mounted on the fuselage to provide the pilot with the information about the surrounding environment using both optical display and aural warning. By using a laser the system can sense objects as thin as wires.

4. Digital Map: Digital moving maps provide a fast, clear and precise information medium. They are capable of displaying moving maps based on all relevant formats and scales. Consequently, the armed forces, border patrol, police, rescue services and other organizations were amongst its first users. Nowadays, the benefits of digital map preparation are also used in land, maritime and air traffic. Modern systems can also provide terrain elevation and obstacle information to the pilot. Systems can be either standalone or integrated within the avionics suite.

5. Deployable Voice and Flight Data Recorder: Voice and flight data recorders (VFDR) acquire and store cockpit voice and flight data. They have been around for a long time and have proven to be valuable tools in the accident investigation process. But after a crash they normally stay inside the wreckage, which may hamper the investigative process. The deployable VFDR (DVFDR) is a rather new development. The crash-survivable memory unit gets deployed (ejected) in case of or shortly before a crash, or in case of sinking of the helicopter. The equipment can float and also contains an emergency locator transmitter (ELT) and/or underwater locator beacon (ULB) to ease localization and retrieval.

6. Passive tower-based Obstacle Collision Avoidance System: The Obstacle Collision Avoidance System (OCAS) consists of units located on utility and power line towers and detects all air traffic entering a predefined warning zone and activates warning lights that illuminate the tower. The fact that the OCAS does not require any installations in the helicopters can make it attractive to helicopter operators. It is also attractive to utilities in spite of its cost. However, the lights on the utility towers can normally be turned off. The OCAS has potential to prevent wire strikes.

7. Miniature Voice and Flight Data Recorder: Voice and flight data recorders (VFDR) have proven to be valuable tools in the accident investigation process. They can provide information that may be difficult or impossible to obtain by other means. Large commercial aircraft and some smaller commercial, corporate, and private aircraft are required to be equipped with VFDRs. Existing solutions however are too cumbersome and expensive for ‘light’ helicopters. The Miniature VFDR is intended to be smaller and cheaper, and can have all relevant sensors (pressure, gyros, GPS) integrated in case the helicopter platform itself does not provide the necessary data.

8. Wire Strike Protection System: A U.S. Army study found that fatalities associated with wire strikes decreased by nearly half after helicopters were equipped with a wire strike protection system (WSPS), also called wire cutters. The system basically consists of cutters placed on the roof and bottom of the rotorcraft. These can cut through wires in case of collision and thus prevent an accident. The system is already installed on many (but not all) civil helicopters, so there is room for improvement.

9. Flight data evaluation and processing for accident and incident investigation: The system comprises devices for voice, mission and flight data recording and data transfer, which are indispensable for post-mission analysis. As such it provides the interface between aircraft and ground station for both mission data upload and mission and maintenance data download. But it also includes the required support equipment for conducting investigations as well as comprehensive flight data analysis, such as the one required for accident / incident investigations.

10. Cockpit Information Recorder: Flight data recorders (FDR) can provide a wealth of useful information to operators, flight instructors, maintenance engineers and accident investigators. But in many cases these systems are too expensive for general aviation applications. A radically different approach to the standard FDR is a cockpit image recording system (CIRS) which only uses a high resolution camera, an area microphone and a collection of internal sensors (like GPS) to build a picture of the flight path of the aircraft. The camera is directed at the aircraft instrument panel where it can ‘see’ the information being presented to the pilot and to also observe the pilots operation of switches / controls. The microphone records background noise and the pilot’s communications.

11. Full Authority Digital Engine Control: The latest designs of (large) helicopters have full authority digital engine controls (FADEC), sometimes linked through the flight management system (FMS) to a four-axis autopilot, which also minimizes the mishandling of the engine controls. The FADEC starts recording automatically when the engine exceeds some kind of limit (for a limited period of time) and can give vital information about the cause of failure and may result in future prevention.

12. Light helicopter HOMP systems: The Helicopter Operations Monitoring Program (HOMP) is a preventive system for improving safety. Data recorded during the flight is systematically analyzed on the ground, and used to identify and quantify risks related to operations. The principle is based on the automatic detection of previously defined events. A more in-depth analysis then leads to the implementation of corrective actions through training programs or changes to operational procedures. The system has first been used for Oil & Gas operations. Nowadays helicopter manufacturers are also offering flight data recording and analysis systems that are adapted to other sizes of helicopter.

13. Efficient Numerical Approaches for On-Board Rotorcraft Flight Performance Modeling: Modern flight systems allow aviators to complete performance/mission planning on-board the aircraft during flight. Previously, the aviator planned their performance and mission as a pre-mission exercise using either paper charts and pencil, or using specialized software on a personal computer. On-board flight performance models answer such questions as: what is the available power, what is the power required to hover or cruise, what is the maximum (flight/hover) weight, what is the maximum flight speed, how much fuel is required or what is the best rate-of-climb that can be achieved. These models are composed of data and equations that are used to calculate many performance parameters. Also included in these models are the boundaries and limits for each of these parameters. These models must be efficient in both size and speed while maintaining accuracy for on-board systems, particularly when the flight performance model is used for pilot guidance such as terrain following. A number of numerical approaches have been used to maintain the accuracy of the flight performance model while being efficient for both size and speed. These approaches include the use of non-dimensional data, higher order interpolation and pre-processing of derivatives and derived results.

14. Radar Altimeter for altitude measurement: A radar altimeter used on aircraft measures the actual altitude of that aircraft above the terrain by timing how long it takes a beam of radio waves to reflect from the ground and return to the plane. As such the system provides the pilot with real time and accurate information. Recent developments of the equipment consist of a single unit containing both transmitter and receiver antennas as well as the processing unit, thereby providing a low-cost solution that can be easily installed, also on ‘light’ helicopters.

15. Immersive Visualization: The analysis of accidents can be complicated and often smaller aircraft and helicopters are not equipped with a Flight Data Recorder. Radar data can be inadequate due to terrain reflections when the aircraft flew in very low altitude. This means that in some cases little information can be available and taking witness testimonies into account can be time and cost consuming. A new method called Immersive Witness Interview (IWI) has been developed to support the analysis of accident investigation, taking witness statements into account. Based on the witness reports that are transformed in three dimensional, a flight path of an observed aircraft can be reconstructed including all potential errors. IWI has been evaluated in the beginning of 2009 within a test in real circumstances.

There are three safety issues that EHEST says there is no promising technology solution: safety management; regulatory oversight and psycho-behaviorial factors/conditions of individuals (more widely known as human factors).

EHEST recommends that the helicopter industry, regulators and university researches use the study and constantly update the information as technology develops. “The challenge on how to implement these technologies lies with the industry,” the report concludes.

Download the full report from EHEST’s website.