High wires and low fliers: new technology targets old conflict

HAI Convention News » 2008
February 25, 2008, 8:47 AM

Safety device manufacturers are striving to offer better obstacle detection equipment to confront the dangers of collisions with obstacles and especially wires. Options range from expensive systems that provide greatly enhanced situational awareness to lower-cost systems with more limited functionality.

Germany-based EADS Defence and Security offers helicopter laser radar (Hellas), a system that scans the area in front of the helicopter with a laser beam capable of detecting wires at distances of up to 3,300 feet. According to the company, the system can also warn of obstacles such as towers, trees, cables and phone lines.

Of the two versions available, the one most likely to be installed in civil helicopters is Hellas-W/HR (warning/high risk). It uses aural and visual warning indicators and/or a multifunction display (MFD) to make the pilot aware of obstacles. On an MFD, the pilot sees a depth and grayscale image of the terrain in front of the helicopter, with obstacles displayed in red. Detection range is about 2,000 feet for wires having a diameter of more than 10 mm.

The other variant, Hellas-A, displays obstacle information in a helmet-mounted display. It was developed specifically for the NH90 military transport, “but if a civil helicopter has a helmet-mounted display, it is also possible to use it for civil applications,” an EADS spokesman said. Detection range is about 2,500 feet for wires with diameters of more than 5 mm. In both versions, Hellas guarantees a probability of detection of 99.5 percent within one second.

Italian-based Selex Communications, meanwhile, is offering its laser obstacle avoidance and monitoring system (LOAM). It has been fitted to six AgustaWestland search-and-rescue EH101s for the Danish Air Force. LOAM is said to be suitable for the civil market, including light singles. The system can detect wires with a diameter of 5 mm.

LOAM and Hellas are based on the same principle. A laser beam scans the area ahead of the flight path and, by analyzing the returned echoes, it identifies possible obstacles and provides the crew with information and warnings.

The main difference between the two systems is in the way they search for obstacles. Rather than raster scanning, Selex uses Palmer scanning, which is a more circular pattern, thereby reducing the units’ blind area and making obstacles easier to recognize, according to Luca Taverni, navigation and optoelectronic system engineer at Selex.

Thanks to a second-generation processing capability, the system can classify obstacles as wires, pylons or buildings. Each category is viewed as a family. For example, a tree or other vertical obstacle will be highlighted as a pylon, while a tower will be classified as a building or other extended obstacle.

Obstacles can be highlighted clearly on a video or infrared image display or on an existing multifunction display, providing valuable visual assistance if the crew should have to execute an escape maneuver. On the same image, an escape cue provides guidance.

Selex said the LOAM has a field of vision of 40 degrees horizontally and 30 degrees vertically. The advertised maximum detection range is 6,500 feet, while the minimum is 160 feet. The false-alarm rate is supposed to be less than one every two hours. The system consists of a sensor, a control panel and the warning unit. Total weight is 53 pounds.

Certification remains an issue for civil applications, Taverni said. Only STCs seem possible in the near future. “The FAA and the EASA have no document to certify this class of equipment,” he explained.

Taverni declined to provide a price for the system, citing variations due to options, installation and so on. He did, however, comment that the system is affordable for small private EMS operators of two- to three-metric-ton-mtow helicopters. In the U.S., Selex is partnering with Lockheed Martin Systems Integration-Owego to market the system.

Not every operator can afford such sophisticated safety equipment. U.S.-based SafeFlight offers a significantly different detector in the $20,000 to $30,000 range. The company’s Powerline Detection System (PDS), which has been available in the U.S. for a few years and was recently certified in Europe, looks for the electromagnetic field radiated by power lines.

When the helicopter is approaching a live powerline, a red light flashes on the instrument panel. Simultaneously, an aural signal warns the pilot of the line’s proximity. Frequency increases as the helicopter gets closer to the line. However, one limitation is the system’s inability to provide a direction to the source of the warning. Another is the fact that it can detect only live power lines.

Wire strikes account for two-thirds of helicopter crashes, a PDS demo pilot noted. In Europe, SafeFlight distributor Trans Hélicoptère Service has negotiated with one insurance company for a 20- to 25-percent premium discount for those helicopters fitted with the PDS.

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