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Tuesday, June 1, 2004

Technology

From engine filters and vibration dampeners to computer aids for avoiding collisions and friendly fire, new technology is helping helicopter crews do more and do it safely. Our editors highlight some of the best examples.

Tracking an Asymmetric Advantage

It has become common in military circles to say the United States today faces "asymmetric threats," as opposed to the "symmetric threats" of yesterday. This essentially means that no current or potential enemy threatens to match us man for man, tank for tank, plane for plane in a set piece battle a la World War II. Enemies instead promise to strike at us in a protracted, guerilla war of attrition. In short, a symmetric threat is Hitler and Nazi German; an asymmetric threat is Osama bin Laden and Al-Qadda.

The U.S. military is well prepared for conventional, symmetric threats. It is less equipped to confront unconventional, asymmetric threats. But as Adm. Vern Clark, the U.S. Navy's chief of naval operations, has observed, the United States also has unique asymmetric capabilities. These include "the expanding power of computing, systems integration [and] a thriving industrial base."

One such advantage is a system called Force XXI Battle Command Brigade and Below Blue Force Tracking. The Northrop Grumman-designed device was installed on more than 200 Army helicopters and 1,200 air and ground vehicles prior to Operation Iraqi Freedom in March 2003. The system has gotten rave reviews for dramatically enhancing situational awareness, improving combat strike capability and reducing fratricide.

Blue Force Tracking "provided a critical [satellite-based communications] link over extended distances, which we would not normally have had with our standard radio systems," said Col. Bill Forrester, chief of staff for the Army Aviation Center at Ft. Rucker.

Forrester served as brigade commander for the 159th Aviation Brigade (Assault) during initial combat operations in Iraq. Blue Force Tracking, he observed, gave him and his fellow pilots—as well as command and control headquarters—complete knowledge of the battle space and the ability to distinguish clearly friend from foe. This bird's eye view extended to at least 430 n.m. (800 km.), he noted.

The U.S. military "has never had this capability before," explained Al Albajan, director of Blue Force Tracking for Army aviation in Huntsville, Alabama. "This is the first time we've ever been able to track air and ground [assets] on a single system."

In fact, Blue Force Tracking performed so well that the U.S. military now is working overtime to get the system installed on all of its aircraft. As of June 1, a total of 600 Army helicopters were fitted with Blue Force Tracking. The Marine Corps last month began installing the system on its UH-1N Hueys and AH-1W Cobras, Albajan said.

Blue Force Tracking also is being integrated into the Air Force's E-8C Joint Surveillance Target Attack Radar System (Joint STARS)—and has attracted the interest of the British military and other U.S. allies. "The Brits have expressed interest in putting BFT on their Longbow Apaches," Albajan said.

Prior to Operation Iraqi Freedom, the Army successfully installed the system on 200 helicopters in roughly 100 days. The quick turnaround time was achieved because Blue Force Tracking was employed in rudimentary fashion, using strap-on components and detached hardware.

Installation has since taken considerably longer because the Army is integrating the system more fully into the aircraft, through software links with existing components like GPS and multi-function displays.

The effort, though, is well worth the time involved. It has reduced the weight of the system from 148 lb. to 15-18 lb., and made Blue Force Tracking more effective and pilot friendly, Albajan said.

For example, the system configuration employed during major combat operations in March and April 2003 permitted pilots only to broadcast their position. It did not give them a "blue-force" picture of the battle space. That has since changed.

Similarly, according to Forrester, the tracking device he employed last year was positioned in the rear of the aircraft; consequently, he carried an extra pilot to operate it. The new system is integrated into the standard piloting controls and displays.

How can we measure the success of Blue Force Tracking? "Let's put it this way," Albajan said: "In the early stages of OIF, there was virtually zero ground-to-ground fratricide." The fratricide instead came from high-altitude, fixed-wing bombers like the A-10 and F-15, he noted.

Helping the Blind See

Situational awareness has been the Holy Grail of safe flight since manmade wings first flew. Clearly Icarus died because he lacked it As imagined as his death may be, it can be attributed to a key culprit in the loss of situational awareness—the weather. It grounds and confounds us still. But while most of us only talk about the weather, some actually do something about it. Max-Viz, Inc. is in the latter group.

The Portland. Ore.-based company has taken the lead in bringing enhanced-vision capabilities aimed at foiling the weather and ensuring situational awareness to the helicopter market. Fixed-wing folks, particularly those in the high-end executive transport market, have enjoyed the benefits of enhanced vision. But the systems can be heavy, expensive and maintenance-intensive—a lethal trio for a technology seeking helicopter applications.

Max-Viz has overcome some of those drawbacks by simplifying the system it offers for helicopters. Its EVS-1000 Enhanced Vision System uses a solid-state microbolometer infrared sensor (above, right) to scan the outside world through clouds and fog and generate a clear image for a pilot. These sensors were chosen in part because they do not require cryogenic cooling, which cuts down on system weight and maintenance requirements.

Max-Viz also opted for a single, long-wave sensor, scanning wavelengths of 8-14 microns, for the EVS-1000 instead of a combination scanning multiple wavelength sets. This limits somewhat the conditions through which the EVS-1000 gather IR data for generating images, but also cuts down on system weight and complexity. (Its EVS-2000 system uses paired long- and short-wave IR sensors.)

The company gained FAA Supplemental Type Certificate approval to install the EVS-1000 on the Bell 212, 412 and 412EP, which company officials said opens the door to a significant market. Significant for the company, clearly, in terms of potential helicopter sales. But significant for helicopter operators, too, in terms of safer and more efficient operations in bad weather.

Erlanger Health Systems in Chattanooga, Tenn. was among the first to recognize that potential. It has installed the EVS 1000 on its aircraft. "For the first time we can `see' what is below us at night as we transport patients in emergency and other situations," said Steve Straughen, director of the Erlanger LIFE FORCE operation in a prepared statement.

Max-Viz is pursuing an STC for the Sikorsky S-76. Other companies offer IR-based enhanced vision systems, but they are focused for now on fixed-wing markets. Given the promise of the technology, it may not be long before most who fly helicopters in margin or changeable weather have a system like Max-Viz's on board.

Keeping Engines Clean

The U.S. military has become a major proving ground for inlet barrier filters, designed to increase the life of engine parts in heavy dust and sand areas. First introduced for the civilian market in the mid-1980's, the barrier filtration system is showing spectacular results both for civilian helicopters operating in unimproved areas and for the U.S. Army, particularly operating in areas such as Iraq and Afghanistan.

Two of the largest U.S. manufacturers of inlet filters are Novato, Calif.-based Filtration Development Co. , primarily on civil helicopters, and St. Charles, Mo.-based Aerospace Filtration Systems, which primarily serves the military market.

Filtration Development was started in 1985, pioneering inlet barrier filtration systems and now has its systems STCed for the Bell 206B and 206L series; Eurocopter's AS350B/D and EC120 series and the MD Helicopters MD500 and 600 series. It is also on OH-6s operated by the U.S. Border Patrol, although those did not require an FAA STC since they are not operated as standard category, according to Andrew Greene, vice president and a founding principal in the company. He also noted that STCs for the filtration system are expected in early 2004 for the Bell 407 and the Eurocopter EC-130, and later in 2004 for the Sikorsky S-76 and the EC135.

The Border Patrol actually has inlet barrier filtration systems on 37 OH-6s, 11 MD600Ns and four AS350BAs, and has started putting filter requirements in its bids for future helicopters, according to Michael Hester, acting chief of air operations for the U.S. Customs and Border Protections. Hester said that a filter would not be mandatory for bids on future aircraft, but that "for any helicopters that we decide to purchase, we're going to go (to the helicopter's OEM) and try to get a barrier filter developed for them. In the areas were we work, we just can't do without it."

The southwestern desert is a particularly nasty environment, with the helicopters operating very close to the ground "because a significant amount of work that we do is tracking from helicopters," he said. "The agents are basically doing from a helicopter what they used to do from the back of a bronco. So in places like Yuma, Arizona, where they have very fine silica, we were going through OH-6 case and vane assemblies every 300 hours. The cost is pretty prohibitive."

The Border Patrol had seen the Filtration Development filters on a 206, and approached FDC and asked for a similar type filter for their helicopters. "We cooperated with them for testing, using the military at Ft. Bliss (Texas), and it kind of evolved."

Along with the Border Patrol, the Filtration Development systems are on law enforcement helicopters such the California Highway Patrol and the Burbank and Fresno, Calif. police departments, Greene said. While the original planning for the filter was to keep dirt out of the engine, the California law enforcement agencies are finding that the filters are also protecting the engines against salt from the ocean and ash from the fires that swept the southern part of the state.

Among Filtration Development's biggest customers, however, are tour operators who consistently fly into unimproved areas such as the Grand Canyon and areas around Las Vegas.

Aerospace Filtration's filters proved themselves in Operation Iraqi Freedom, where they helped protect U.S. Army engines and keep the helicopters they power flying. The U.S. Army's OH-58Ds in Iraq were having their engines replaced every 20-50 hr., according to Mike Scimone, technical director for the company. Of the 116 OH-58Ds sent there, he said, 62 had no filters installed and virtually all had to have engines replaced. The Army has had Aerospace Filtration's Engine Barrier Filter kit installed on 57 of the 62 and plans to put it on its entire fleet of 375 OH-58Ds. The 54 OH-58Ds sent to Iraq with the filtration systems were the first combat helicopters to be deployed with the filter as an integrated part of the aircraft, he said.

Particle separators previously used to protect helicopter engines are ineffective against the fine sand encountered in the Iraq desert, Scimone said. They let 20-40 percent of the sand through to the engine. With the Aerospace Filtration's kits installed, the OH-58Ds are making it to their TBO of 1,750 hr. even in the desert operations, Scimone said.

Aerospace Filtration's system is primarily on the OH-58D and the MD 500 series, including the AH/MH-6J "Little Bird." The system is also currently on public-use helicopters, such as those flown by National Oceanic and Atmospheric Administration, and law enforcement organizations such as the MD-500s being flown by the Mesa (Arizona) Police Department and St. Louis (Missouri) County Police Department, he said.

Improving the Puma

Eurocopter continues to move toward certification of its advanced technology systems now going into the EC225, latest member of the Puma/Cougar family of twin-engine, mid-range helicopters. The Marignane, France-based company is using the experience from some 550 Puma/ Cougar helicopters flying in excess of 2.7 million flight hours as the basis of the new helicopter, upgrading its rotor systems, main gear box, avionics and flight control system.

A 220-hr. endurance test on the EC225 "Iron Bird" test bench was now been completed (bottom right), testing the dynamic components and power train. The testing included 20 cycles of 11 hr. each that involved 40 hr. at take-off power, 80 hr. at maximum continuous power and 40 hr. at one-engine inoperative rating. This was followed by three cycles of 11 hr. each performed simultaneously at high oil temperature and low oil pressure settings. Final testing involved 50 over-speed and 200 over-torque tests.

The aircraft will have a 15-percent increase in payload, five-percent increase in range and a seven-percent increase in speed compared to the Super Puma Mk1/Mk 2, with close to a 5-hr. flight endurance and a range in excess of 200 nm.

The new Turbomeca Makila 2A engine consists of five independently changeable modules for ease of maintenance, with emergency blade shedding technology. The engine system includes two dual-channel FADECs with fully automatic control to eliminate the need for manual back-up mode. The engines each generate 2,413 shp, a 13 percent increase over the previous model. They also include a new airflow concept and new materials to improve efficiency.

The aircraft's avionics are linked into the engine's system to include a mode that automatically performs the initial emergency tasks in the event of an engine failure. If an engine fails in cruise flight, the automatic mode reduces the airspeed without any pilot input, allowing the aircraft to continue flight with the remaining engine on maximum continuous power. If any altitude was lost, the aircraft will automatically return to the original altitude.

The engines allow a service ceiling of 20,000 ft. density altitude and a takeoff and landing altitude of 7,200-ft. pressure altitude. This increased engine power and gross weight called for an upgraded, reinforced main gearbox with a back-up lubrication system providing 30-minute dry run capability.

The new five-bladed main rotor system is growth version of the four-bladed Spheriflex main rotors currently used on the AS332 Super Puma. The blades have an advanced airfoil section with parabolic tips, with a multi-box structure. Both the rotors and the horizontal stabilizer can be equipped with a deicing/anti-icing system that makes it possible to fly in extreme icing conditions without limitation of severity. The five-bladed configuration also greatly reduces vibration levels. Vibration levels are also reduced through a new state-of-the-art active anti-vibration system. Internal noise levels have also been reduced by 3 decibels over the Super Pumas now being used in the North Sea. Because of the logarithmic, rather than linear, equivalent characteristics of decibel levels, the 3 dB reduction equates to reducing the noise level by half.

The cockpit is equipped with an Advanced helicopter Cockpit and Avionics System with four-axis automatic pilot. The system consists of four 6 in. by 8 in. LCD multifunction displays for piloting, navigation and mission information and two 4 in. by 5 in. VMS color displays for aircraft parameters.

Keeping Engines Clean

The U.S. military has become a major proving ground for inlet barrier filters, designed to increase the life of engine parts in heavy dust and sand areas. First introduced for the civilian market in the mid-1980's, the barrier filtration system is showing spectacular results both for civilian helicopters operating in unimproved areas and for the U.S. Army, particularly operating in areas such as Iraq and Afghanistan.

Two of the largest U.S. manufacturers of inlet filters are Novato, Calif.-based Filtration Development Co. , primarily on civil helicopters, and St. Charles, Mo.-based Aerospace Filtration Systems, which primarily serves the military market.

Filtration Development was started in 1985, pioneering inlet barrier filtration systems and now has its systems STCed for the Bell 206B and 206L series; Eurocopter's AS350B/D and EC120 series and the MD Helicopters MD500 and 600 series. It is also on OH-6s operated by the U.S. Border Patrol, although those did not require an FAA STC since they are not operated as standard category, according to Andrew Greene, vice president and a founding principal in the company. He also noted that STCs for the filtration system are expected in early 2004 for the Bell 407 and the Eurocopter EC-130, and later in 2004 for the Sikorsky S-76 and the EC135.

The Border Patrol actually has inlet barrier filtration systems on 37 OH-6s, 11 MD600Ns and four AS350BAs, and has started putting filter requirements in its bids for future helicopters, according to Michael Hester, acting chief of air operations for the U.S. Customs and Border Protections. Hester said that a filter would not be mandatory for bids on future aircraft, but that "for any helicopters that we decide to purchase, we're going to go (to the helicopter's OEM) and try to get a barrier filter developed for them. In the areas were we work, we just can't do without it."

The southwestern desert is a particularly nasty environment, with the helicopters operating very close to the ground "because a significant amount of work that we do is tracking from helicopters," he said. "The agents are basically doing from a helicopter what they used to do from the back of a bronco. So in places like Yuma, Arizona, where they have very fine silica, we were going through OH-6 case and vane assemblies every 300 hours. The cost is pretty prohibitive."

The Border Patrol had seen the Filtration Development filters on a 206, and approached FDC and asked for a similar type filter for their helicopters. "We cooperated with them for testing, using the military at Ft. Bliss (Texas), and it kind of evolved."

Along with the Border Patrol, the Filtration Development systems are on law enforcement helicopters such the California Highway Patrol and the Burbank and Fresno, Calif. police departments, Greene said. While the original planning for the filter was to keep dirt out of the engine, the California law enforcement agencies are finding that the filters are also protecting the engines against salt from the ocean and ash from the fires that swept the southern part of the state.

Among Filtration Development's biggest customers, however, are tour operators who consistently fly into unimproved areas such as the Grand Canyon and areas around Las Vegas.

Aerospace Filtration's filters proved themselves in Operation Iraqi Freedom, where they helped protect U.S. Army engines and keep the helicopters they power flying. The U.S. Army's OH-58Ds in Iraq were having their engines replaced every 20-50 hr., according to Mike Scimone, technical director for the company. Of the 116 OH-58Ds sent there, he said, 62 had no filters installed and virtually all had to have engines replaced. The Army has had Aerospace Filtration's Engine Barrier Filter kit installed on 57 of the 62 and plans to put it on its entire fleet of 375 OH-58Ds. The 54 OH-58Ds sent to Iraq with the filtration systems were the first combat helicopters to be deployed with the filter as an integrated part of the aircraft, he said.

Particle separators previously used to protect helicopter engines are ineffective against the fine sand encountered in the Iraq desert, Scimone said. They let 20-40 percent of the sand through to the engine. With the Aerospace Filtration's kits installed, the OH-58Ds are making it to their TBO of 1,750 hr. even in the desert operations, Scimone said.

Aerospace Filtration's system is primarily on the OH-58D and the MD 500 series, including the AH/MH-6J "Little Bird." The system is also currently on public-use helicopters, such as those flown by National Oceanic and Atmospheric Administration, and law enforcement organizations such as the MD-500s being flown by the Mesa (Arizona) Police Department and St. Louis (Missouri) County Police Department, he said.

Getting Rid of the Shakes

Lord Corp. continues to help aircraft operators get rid of the shakes, most recently applying its vibration-reduction expertise to Hindustan Aeronautics, Ltd. Advanced Light Helicopter, otherwise known as the Indian Dhruv.

The twin-engine Dhruv is unique in its ability to reach high altitude and high temperature areas—necessary functions for search and rescue operations. But it was plagued by vibration problems that made a key customer, the Indian air force, reluctant to accept the aircraft. HAL called on Lord, its sole supplier of main and tail rotor elastomeric bearings and isolators for the current pylon isolation system, to see if it could solve the problem on the the 12-passenger, two-crew member aircraft.

The Indians are far from alone in turning to Lord. Agusta a year ago won Italian certification of its A109 Power and A119 helicopters with Lord's fluidlastic pylon isolation systems installed. The company has been producing those aircraft since then. Lord is supply its rubber-to-metal bonded vibration control technology for the Bell/Agusta Aerospace AB139 .

Likewise, Erickson Air-Crane called on the vibration-mitigation expert to resolve vibration, noise and motion control that were causing cracking problems on S-64E Air-Crane engine cases.

In each case, these companies called on Lord to apply expertise gathered over decades to eradicate a nasty problem that was giving their product a bad name. Neither the problems nor the technology applied to solve them—active Frahms, elastomeric struts and such—are sexy (though they can be severe and dangerous). But they provide an excellent example of good, old nut-and-bolts application of proven skill and technology to helicopter problems.

HAL in 2002 hired Lord to conduct two phases of diagnostic testing to figure out the source of vibration on the Dhruv aircraft and determine whether the company's Active Vibration Control technology could help solve it.

A fuselage fitted with numerous accelerometers under a series of tests in a hangar, on ground runs and in flight, producing data that Lord's engineering and research team then crunched. That team came up with a solution that reduced the vibrations to acceptable levels and did so in time for an aircraft fitted with the Active Vibration Control system to be displayed at the 2003 Paris Air Show.

Erickson turned to Lord back in 2000 to help it solve the vibration problem on its remanufactured S-64Es. Lord applied the same approach, setting its engineers loose to scour the aircraft for sources of vibration, then narrowing that list down to the most likely subjects.

That was no easy task. Describing the S-64E as a unique airframe is something of an understatement. Add to its unique configuration the missions it flies—including lifting structure to the pinnacles of buildings, positioning power line stanchions and carting huge logs off mountains—and you've set the conditions right for some pretty intricate vibration modes. Figuring out what they were, which ones were cracking the engine cases and figuring out how to stop that is a pretty tall set of orders.

As Lord's account manager for Erickson at the time, Mike Kerlee, explained, the S-64E's logging missions illustrates the challenges. During those missions, the aircraft is flown sideways down a mountain slope with a log load slung underneath. This results in all sorts of shudder and shake conditions, which had to be identified and characterized.

Lord and Erickson were up to the challenges. The companies succeeded in analyzing the vibrations and in developing a design to damp out the unusual vibration conditions of such missions.

That led to other work reviewing other modifications to reduce fatigue and cracking and increase the life of the S-64E.

Lord's expertise and technology help keep helicopters flying, flying longer and flying safely, which is about as effective a technological application as we can think of.

Giving Downed Pilots the Hook

Imagine yourself on the ground, in unfamiliar and hostile territory, possibly injured and desperately in need of communicating with someone of a friendly bent.

You remember movie scenes of warfighters in this predicament, slogging through mud and rice paddies, wrapping wounds with shredded clothing, fighting off hunger and infection and death. You don't want to be there. If only you had a way to phone home.

General Dynamics Decision Systems has worked to make that phone call home possible with the ongoing development and refinement of the AN/PRC-112 combat search and rescue radio. Combined with the Hook 2 GPS-based CSAR system, the PRC-112 is a nifty little package that has saved more lives—it is safe to say, given known levels of special operations in Afghanistan and Iraq—than we may ever know.

The new AN/PRC-112G version of the device is much, much more than a radio. It combines a beacon, a transceiver and a transponder with GPS capabilities into a single, handheld unit. Embedded within it is distance measuring equipment which can be interrogated by the RSC-125G or the AN/ARS-6 personnel locator systems. (The AN/ARS-6 is the standard combat search-and-rescue system for the U.S. Army, Navy, Air Force and NATO.) Also embedded is a CA code, 12-channel parallel GPS receiver.

The transceiver is capable, the company says, of sending encrypted coordinates of your position (in latitude/longitude, Universal Transverse Mercator or Military Grid Reference System format). It can be used for two-way messaging and for identification. It also allows an on-scene commander to communicate directly with a downed subject and units en route to him by line of sight or over-the-horizon without having to be passed through multiple handoffs.

The device's GPS CSAR system is turned on automatically when a downed aircrew member turns the radio on. The embedded GPS transponder acquires the location of the radio from the GPS satellite constellation.

The pilot can then select from a menu of encrypted two-way messages that can be stored by the radio. The pilot also can select from a menu of answers to a list of questions scripted to elicit information that will give rescuers a fuller picture of the pilot's physical condition, surroundings, threat environment and general predicament. The answers also are stored in the radio.

The downed crewmember can then transmit the stored data, which is relayed through military satellites or other "national assets" to those coordinating the rescue forces. The radio also is designed to respond with transmission of the stored data when interrogated by nearby rescuers.

Any aircraft equipped with a Quickdraw 2 interrogator also can trigger transmissions from a PRC-112G, Quickdraw 2, another General Dynamics system, is designed to plug into the intercom system of any aircraft. It includes a commercial 12-channel GPS engine, a user's keypad, liquid crystal display and RS-232 port, user-selectable alert features that notify the operator — via audio or a flashing LED — when a new message is received, a modem with error correction and encryption, and an intercom interface with automatic level control.

The PRC-112G transmits in short, coded bursts that minimize the possibility that they will be intercepted and the transmitter detected.

Once rescue aircraft are in the area of the downed crewmember, the PRC-112G is designed to provide terminal guidance for them.

The PRC-112's wave forms are software-based, so if upgrades are developed (and they are continually) existing units can be updated without the need for changes to hard wiring. Designed to run on a variety of PCs, the device's Program Loader loads key, datum, frequencies, waypoints, user I.D. codes and response messages into the AN/PRC-112 as well as the B and B1 transceivers and the Quickdraw and Quickdraw2 interrogators. It includes an interface box, a cable set and a Windows-based software package.

Now that's manufacturer's line on the system. Does it really work? Ask Lt. Cdr. Scotty McDonald.

On April 1, 2003, McDonald was a radar intercept officer in the back of a Grumman F-14A assigned to the U.S. Navy's VF-154 Black Knights squadron.

At about 11 p.m. that night. he and his pilot were high over Iraq, somewhere shy of the border with Saudi Arabia, when the Tomcat's left engine quit.

It was "a mechanical malfunction that gracefully degraded," McDonald said.

The pilot shut down the engine, but the failure of the tower shaft to its accessory gearbox has somehow fouled the valve that allows fuel from the left side of the F-14 to be fed to the right engine. They flew on until it was time to cross-feed the fuel, at which point they discovered the problem.

"We were beating feet to get over the Saudi border to more friendly territory," McDonald said.

They were close to plugging in for an aerial fueling from a tanker when the right engine quit.

"Basically, we ran out of gas with the gage showing the tank half full."

The aviators ejected at about 20,000 ft. and landed, after a 13-min. parachute descent, a fair distance from each other. McDonald turned on his PRC-112G and established voice communications with rescuers, who had been alerted to the in-flight problems.

The device transmitted its coded bursts on his position and other data. Before long, rescuers were taking him and his pilot to safety.

"It was a real comfortable feeling," he said, knowing his communications with rescuers "was happening with real short transmissions with a low probability of intercept."

It's a good bet McDonald is not alone, and will not be the last, to draw such comfort from the PRC-112G.

A Fighter Pilots' Solution

To Helicopter Wire Strikes

Name the last time you can think of that two fighter jocks sat down to brainstorm something that would be beneficial to helicopter pilots.

Take your time . . . We're not going anywhere.

It is a bit hard to imagine, but that seems to be just what happened about five years ago in Norway.

The fighter jocks, Morten Mork and Rolf Bakken, had spent a fair amount of their time in the Royal Norwegian Air Force on low-level flights through that Scandinavian nation's fjords. They also did low-level flying in the United States and other countries. More than once, we'll assume, Mork and Bakken had their reflexes and piloting skills testing by the sudden appearance of a wire slung across a fjord. We'll assume that, because when they sat down five years ago, they brainstormed a system for averting collisions of aircraft and wires.

Their low-level flight experience made clear to the pair that "wires and towers are not adequately marked," Mork said. (OK, maybe they weren't thinking of their rotary-wing colleagues. But their brainstorm may be beneficial nonetheless.)

That brainstorm produced the Obstacle Collision Avoidance System. While it is still in development, the system has impressed aviation regulators in Norway and the United States as well as utilities and helicopter operators in both countries enough that they've lined up to help refine and test it.

The appeal of the system is simple. If it works as promised, it should be less expense for utilities than painting and installing lighting on power-line towers and keeping the paint clear and the lights working. Also, a 500-kV. power line knocked out of service by an aircraft collision can cost a utility $5,000-10,000 a minute in lost revenue.

As for the helicopter operators, the system required no new equipment to be installed on aircraft. No cost, no added weight, no new maintenance requirement—that's the kind of solution any aircraft operator would love.

The two former fighter pilots developed OCAS with funding from the Norwegian Industrial and Regional Development Fund and START-fondet ASA, a leading Norwegian technological investment capital firm.

They also gained the support of the Civil Aviation Administration of Norway, as well as that of the Royal Norwegian Air Force and Norway's leading utility, Stattnett SF. Mork characterizes OCAS now as a national effort in Norway.

The system uses octagonal, L-band radar transmitters mounted on masts near obstructions such as power lines or cellular-telephone towers to detect aircraft on a collision course. The radar is low-powered, transmitting at about one watt.

(A wire span 2,000 ft. wide would require a mast on either side.)

Once the system detects a potential collision, it activates lights on the obstruction and broadcasts an aural warning (such as "Wires, Wires" or "Tower, Tower") on all aeronautical VHF frequencies. The warning is transmitted at low power to keep the broadcast from propagating beyond the immediate hazard area. The only thing an aircraft needs to benefit from such warnings, Mork said, is a VHF radio and an alert pilot.

OCAS also logs data on the encounter for later analysis.

OCAS is a "sleeper" system. It does not activate ground lights or broadcast warnings until a collision looms.

The system underwent field testing in Norway in late 2003 and early this year. In March, Mork and his partner shipped an OCAS unit to the U.S. FAA's Technical Center in Pomona, N.J. for testing there. The Tennessee Valley Authority and the Kentucky utility LGE Energy each have agreed to set up a sight at one of their power-line river crossing for installation and field testing of OCAS. A report on the U.S. testing is due in July.

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