Since EASA certified the first night-vision image system on a civil helicopter (see AIN, September 2007), several European operators have expressed interest in or have started to adopt night-vision goggles (NVGs). Eurocopter reports it has begun testing for a German operator. No doubt, newcomers will draw from the experiences of two major European rescue operators–Sécurité Civile and Rega. They did not have to wait for EASA approval because they had to convince only their national aviation authorities.
For the Sécurité Civile, France’s rescue arm, NVGs are a response to automation at destinations, said Guy Roger, an EC 145 pilot. Previously, pilots would talk to a person when they called their destination and receive a firsthand assessment of weather conditions. Now pilots reach a recording. In some cases this absence of a fuller interpretive weather briefing has resulted in night missions being canceled,
reducing the credibility and effectiveness of the Sécurité Civile.
However, NVGs enable the organization to fly more missions, despite less than comprehensive weather briefings. The devices are proving to be reliable, needing minimal maintenance, and they are cost effective, Roger emphasized. Moreover, they are ergonomic, offering an advantage over a head-up display in that they move with the pilot’s head. They are also easy to use and provide a quality image, Roger said.
Sécurité Civile helicopters fly with a crew of two–a pilot and a flight engineer. The latter takes care of navigation and hoist operations. Both wear NVGs. However, if the flight engineer operates the hoist with a conventional searchlight, only the pilot wears NVGs.
Training Is Essential
Roger cautioned that safe and effective use of NVGs requires that crews are properly trained. For example, “The way trees appear when viewed through NVGs is not exactly intuitive, as some are white and some are black,” he explained. In addition, “you do not see green and blue colors very well through NVGs, whereas infrared, which you would not normally see, appears clearly,” Roger said.
Pilots must also be trained to compensate for how the device modifies sight. First, the field of vision is only 40 degrees, and a 120-degree field of view is usually recommended for flying purposes. In addition, the pilot has to look under the goggles to see the instrument panel.
A major drawback is the poor separation performance. “You cannot see a power line until it is as close as 650 feet,” Roger said. In the event a bright light reaches the NVGs, the system protects itself, and the pilot cannot see anything as long as the light dazzles the system.
Operators using NVGs must learn to readjust their entire mental process. “A lot of brain activity is required for estimating distances,” Roger said. The absence of 3-D references (NVGs provide 2-D vision) means the brain must perform even more elaborate calculations. The mental activity is so intense that most pilots find it impossible to sleep immediately after an NVG mission. This has to be taken into account when an operator is developing a roster with duty and rest periods. The crew can also become euphoric from seeing at night, making them more vulnerable to error.
Sécurité Civile pilots have learned the importance of synergy between the helicopter and the NVG equipment. It uses Litton M949s on all 30 of its Eurocopter EC 145s. “The EC 145 is well suited because it provides good visibility, the autopilot is stable and we have one infrared searchlight,” Roger said. An infrared light is a conventional white light with a filter that releases only infrared light. Therefore, it does for the NVG-equipped eye what a conventional light does for the naked eye.
Not all operators use NVGs to enable previously impossible flights. In Switzerland, the Rega air rescue organization uses NVGs to enhance safety during operations that would otherwise be conducted with the naked eye. Rega pilots do not fly with NVGs if conditions would prevent a naked-eye mission. Weather minimums remain unchanged, which is consistent with EASA rules. However, Rega acknowledges that use of NVGs reduces the likelihood of inadvertent flight into IMC.
“We do not do anything more but we do it more safely,” pilot and instructor Walter Schneibel, who is also responsible for night flights and NVG operations, told AIN. All 43 Rega pilots are trained to use NVGs. Schneibel commented that they are economical because they cost “three times less than a big searchlight.”
Under Rega’s operating principles, only one crewmember wears NVGs. The thinking is that this way at least one person has a full field of vision. During a final approach, for example, the pilot not flying looks for naked-eye visual cues, and he calls them the moment he sees them. The pilot then flips up his goggles. Rega pilots do not use NVGs when the helicopter is close to the ground.
In addition, always having one pair of naked eyes in the cockpit eliminates the risk of euphoria, Schneibel said. “One can caution the other, ‘Hey, visibility is too bad; we must fly back home,’” he added. Schneibel commented that fatigue is not an issue, as Rega’s flights are short.
Rega uses ITT F4949 NVGs, compatible with its AgustaWestland A109 K2s and the Eurocopter EC 145.