Over the last six years, the North American aeromedical transport industry, particularly its helicopter EMS community, has become increasingly concerned about an accident rate it (and others) sees as excessive. Attention has focused on night flights and operations in reduced visibility, both of which contribute significantly to the number of mishaps. There is growing interest in wider use of technologies to enhance and amplify the visual capabilities of pilots. Night-vision goggles (NVGs) have garnered most of the attention in safety studies and operator preference, but infrared (IR) sensing is gaining a constituency.

Chuck Crompton, senior manager of marketing and dealer relations for Max-Viz, which markets enhanced vision systems (EVS) that derive their images from uncooled IR sensors, asserts that there is a growing sentiment in the EMS community that the best way to improve the safety of night helicopter operations while achieving higher mission completion rates is by combining the use of NVG and infrared EVS. He noted that years of experience by the military have proved the advantages of using both NVGs and forward-looking infrared (FLIR) sensors.

Crompton described some advantages to having both NVG and IR sensing available in night helicopter operations. “The pilot may choose to use only the EVS after coming to a hover during a dark landing or brown-out, dust-obscured landing,” since the night goggles cannot “see” through dust or other obscurants.

He continued, “With EVS you avoid the orientation problems of NVG transition from dark flight to lighted landing zones, with flashing lights on emergency vehicles. With infrared you ‘see’ the hot vehicles but not the flashing lights.

“During an approach to a landing, EVS would let you discern ‘hot from cold’ on vehicles and other aircraft in the landing zone, ever useful in an active landing zone or at an EMS auto accident scene. With EVS on a cold night, people in the landing zone will be highlighted as ‘white hot.’ Having both NVGs and EVS available makes possible a complementary combination scene of lights and thermal (non-light-emitting) targets and the surrounding environment,” he said.

Bob Yerex, a former U.S. Coast Guard and EMS helicopter pilot now regional sales manager rotary wing with Max-Viz, used FLIR and NVGs concurrently in USCG operations. He is a strong proponent of using both technologies in civilian operations. “I expect that in the near future we’ll see civilian operators evaluating the use of both,” he said. Already, San Diego (Calif.) County Fire and Rescue has installed and is operating Max-Viz EVS with NVGs in the agency’s Bell 212s.

Yerex added that if insurance underwriters can be convinced to reduce premiums on aircraft equipped with the safety-enhancing advanced technology now available, many more operators will deem it affordable.

On that note, at this year’s Aviation Insurance Association annual meeting, keynote speaker NATA president Jim Coyne stated, “A good [rotary-wing] safety management system would include night-vision goggles and thermal enhanced vision” as well as radio altimetry and enhanced ground proximity warning. He expressed hope that this equipment combined with appropriate aircrew training would result in lower insurance premiums and better coverage.

Max-Viz contends that its system– which features an uncooled microbolometer IR sensor–makes a joint EVS-NVG better suited to helicopters than an EVS using cryogenically cooled sensors because the uncooled sensor is lighter, smaller and less expensive.

CMC Electronics, a leading provider of cryogenically cooled IR sensors for civil and military operators, late last year announced plans to offer a line of uncooled sensors for EVS applications, and is known to be marketing them to the helicopter community.

Worth the Cost?
Despite the additional cost of providing EMS helicopters with NVG and EVS capability, there is anecdotal evidence suggesting the equipage could pay off by reducing the rotary-wing EMS accident rate, the highest in U.S. civil aviation. An NTSB report on a fatal helicopter EMS accident near Chico, Calif., on the evening of Sept. 22, 2001, described how NVGs alone were not sufficient to prevent the pilot’s losing visual contact with the surface when main rotor downwash kicked up a thick cloud of dust and dirt.

The NTSB narrative said, “One of the flight nurses stated that he was sitting behind the pilot using a pair of handheld night-vision goggles to assist in making sure that the landing area was clear. He indicated that the approach was normal. [Then at] about 10 to 12 feet agl during the flare for landing, their vision became obscured by dirt/dust storm (brown-out) initiated by the main rotor blades. The flight nurse stated that he kept asking the pilot if he could see anything but did not receive a response. He heard the engine power up with no problem and then remembers hitting trees.”

An EVS operating in the long-wave portion of the IR spectrum (eight to 14 microns), if available to complement the NVGs, might have prevented this mishap and spared the resulting death and a serious injury. Long-wave IR is able to penetrate the “brown-out” phenomenon, which blinds both the naked eye and NVGs.

Will Lovett, chief insurance underwriting officer for AIG Aviation in Atlanta, is an experienced Army helicopter pilot and a strong believer in using NVG and EVS for EMS operations. “Once you fly with NVG you’d never want to be without it,” he observed, adding his agreement that infrared EVS represents a vital adjunct to a nighttime EMS equipment suite.

A primary difference between night vision goggles and infrared sensors is that the goggles sense visible light and amplify it electronically, while the IR sensor detects electromagnetic energy emitted from heat sources at lower frequencies. The former greatly enhances the eye’s ability to see; an infrared EVS can display targets that do not emit or reflect visible light and even some features that would be invisible to the human eye regardless of light level.

An EVS will provide situational awareness with imagery gained from differences in thermal content and reflectivity even where the visible light level is at or below the threshold of NVG detection. During ground operations in fog, EVS will detect objects at substantially longer distances than NVGs will, and at four to 10 times greater distance than the naked eye.

While the typical NVG image intensifier can produce a useful image from starlight or low-level moonlight by amplifying it an average of 1,000 to 3,000 times, the NVG will always require some visible light.

Since the FAA issued the first STC for NVG use by a civilian helicopter EMS operator in 1999, aviation medical examiners have become aware of some basic operational issues and associated clinical implications.

For example, at a visual light level one-tenth of normal starlight, NVGs will allow the wearer to see with the equivalent of 20/40 daylight visual acuity, but 20/40 vision “will not let you see wires or poles unless they are shiny, large or very close,” vision specialists G.J. Salazar and V.B. Nakagawara pointed out in a Federal Air Surgeon’s Medical Bulletin article. An infrared EVS, by contrast, “sees” active powerlines through the heat produced by the current they carry.

Salazar and Nakagawara caution that “NVG-aided acuity of 20/30 or 20/40 assumes perfect cockpit lighting, properly focused goggles and ideal weather conditions. Particularly hazardous are obstacles or terrain features masked in shadows. Experience and recurrent training are crucial to using NVGs safely.”

Yet, despite some operational limitations, NVG use by EMS operators continues to expand. Nowhere is this more evident than at Air Methods, a major EMS fleet operator and a designer and installer of EMS interiors and avionics.

Air Methods earlier this year earned certification of an EFIS panel-equipped Bell 407 that joined Air Med, one of the company’s two air medical services, upon STC issuance.

Its panel is anchored by two 10.4-inch (diagonal) Sagem liquid crystal displays (LCD), hosting primary flight and multifunction (MFD) presentations with some EMS-specific software features.

Mike Slattery, director of marketing for Air Methods’ product division, said the 407, part of an Air Med fleet expansion, is NVG-compatible with goggles that are interchangeable between crewmembers. “Almost every aircraft we deliver is. It’s almost a mandatory requirement now. We have done NVG-compatible lighting and provisioning on everything from the 407 to a [Sikorsky] S-70A for the Los Angeles Fire Department. We do have customers who are getting interested in EVS, but we have not installed any yet.”

Slattery said the company is also installing and certifying a Sagem AP-85 digital autopilot in the Air Med 407. “We’ve done about 20 AP-85 installations, but this is our first Sagem (formerly Sfim) glass cockpit,” he noted. The MFD will include an oxygen gauge to monitor levels both in the medical supply and the pilot’s system. “When flying out of Salt Lake City at night, the pilot always has to be on oxygen,” said Slattery. The electronic display also shows autopilot control actuator positions along with a moving map and engine parameters. “It provides great information display flexibility, but it’s relatively inexpensive,” he said of the EFIS.

EVS is not yet common in the EMS helicopter market, but it is building hours and pilot confidence with two air medical operators in the south-central U.S. Erlanger Medical Center Life Force in Chattanooga, Tenn., pioneered use of the Max-Viz EVS-1000 single IR sensor system in rotary-wing air ambulance service four years ago. And this summer Air Evac Lifeteam, in West Plains, Mo., announced an order for 10 EVS-1000 systems for installation on its fleet of Bell 206L LongRangers, with options for 30 more next year.

Colin Collins, president of Air Evac Lifeteam, said the company chose the EVS-1000 system “for its demonstrated performance, particularly as related to avoidance of CFIT as well as enhancing landing zone identification and obstruction clearance.”    o