Device automatically warns pilots of wires and obstacles

Aviation International News » February 2004
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February 1, 2007, 8:36 AM

Wire strikes–long the bane of low-altitude rotorcraft and agplane operations–could be reduced if a system now undergoing testing on both sides of the Atlantic is able to supplement or even replace marker balls and continuously flashing strobes. It could also aid other low-flying aircraft in avoiding any obstacles in the flight path.

The system consists of a radar sensor that detects aircraft entering a predefined warning zone around an obstacle, activating a flashing warning light system. If no evasive action or insufficient evasive action is undertaken by the pilot, a voice/audio warning message is transmitted on all channels in the airborne VHF or optional UHF communication bands.

The obstacle clearance avoidance system (OCAS) is described as a joint national effort from Statnett SF, Norway’s largest utility owner; the Civil Aviation Administration of Norway; and the Royal Norwegian Air Force. In addition to warnings, OCAS provides utility companies and other users with date-logged, explicit radar track records of aircraft movement, including speed, heading and altitude.

According to manufacturer OCAS AS of Norway, it provides dependable obstruction-avoidance warnings to all aircraft around-the-clock at costs competitive with standard, daytime-only obstruction marking, such as painted towers and marker balls.

The FAA is having an OCAS unit delivered to its William Hughes Technical Center near Atlantic City, N.J., this quarter for an initial evaluation. “After that, we have to look at some sort of an evaluation period in the U.S. to examine the various issues,” said Bill Wallace, FAA national resource specialist for rotorcraft operations.

Among the agency’s concerns are radar spectrum issues and how OCAS interfaces with other radar systems. Additionally, there are questions on how it copes with the greatly increased numbers of aircraft that operate in the U.S. compared with other parts of the world.

Wallace described OCAS as a very-low-powered system that has been tested only for individual aircraft. “We have a lot more aircraft in the air at one time,” he said, “so that’s one of the questions that we have to look at.”

OCAS is being readied for operational field testing and evaluation in Norway. The certification process will be performed with the Norwegian CAA and the Norwegian Post and Telecommunication Authority as participants. OCAS AS expects the units to be commercially available in the first quarter of next year.

The OCAS field unit is a self-powered modular mast design that can be placed almost anywhere. Internal network communication produces real-time system status reports and reports of all aerial movement and warning activations. Data reported will be stored at the OCAS control center. In the event of a system failure, OCAS can automatically produce messages to notam services or similar systems.

The OCAS field unit, which can be remotely maintained to reduce cost and increase reliability, “sleeps” until a target is detected and it uses a wireless link to control a number of strobe light units installed at the obstruction. Defined warning zones are controlled by 360-degree continuous wave radar that detects incoming aircraft.
OCAS consists of two or three nine-foot, 375-pound modular tubes (depending on topography) powered by 220/110-volt AC or solar panels and a battery bank. The target detection range for OCAS is 1.7- to three miles (depending on target size) and the VHF range is about 19 nm (depending on radio service area). No modification is needed to the aircraft.

Wallace said the FAA would like to determine whether OCAS could be adapted to provide warnings around TFRs. He said such low-level radar is already being used in Afghanistan by U.S. Special Operations forces and the Norwegian military for perimeter defenses. Norway is looking at possible civil applications for that country’s homeland defense system.

However, using the P-40 area around Camp David, Md., as an example, Wallace pointed out that busy Frederick Airport (FDK) is nearby, and the flyway around it is heavily used. “What would happen to the specific system when there are high numbers of small aircraft on a weekend?” he asked. “We don’t know.”

Late this spring, Lexington, Ky.-based LG&E Energy plans to begin testing OCAS after field units are installed where some of its electric transmission lines cross the Ohio River near Madison, Ind. The tests are expected to continue into the fall. Several other power companies are also planning tests, including the Tennessee Valley Authority, which covers much of the Southeast.

Nate Mullins, manager of transmission lines for LG&E, said his company has been told the OCAS target price is about $50,000 per installation, which he said is half what it costs the company to provide wire-strike protection now. “We can replace all of those systems [painted towers, marker balls and strobes] with the OCAS way of lighting a tower because it will work at nighttime or daytime,” he said. “Additionally, you’ve got the verbal warning and also the lights.” Utility companies also like the fact that the system sleeps until an aircraft penetrates the dome of coverage, thus reducing complaints from adjacent property owners.

Morton Mork, CEO of OCAS AS, told AIN that the Norwegian CAA is working with the JAA/EASA, as well as the FAA, to ensure that a single system can be produced and certified for use in the EU and the U.S. “The challenge for the regulators is that nothing like OCAS has been produced before,” he said. “So they just can’t open a book and say you have to comply with A, B, C and D.” But he added that the support from the FAA has been outstanding.

“We are taking the guidelines that we get from the Norwegian authorities on behalf of the JAA and the FAA and trying to combine them to see if one product can serve them all,” said Mork. “It is a tough job.”

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