within the Fact Sheet was to “promote technol- ogy such as Night Vision Goggles, terrain aware- ness and warning systems and radar altimeters.” But, if the current NPRM is based on the
statements in the Fact Sheet, then it is puzzling that
the FAA has eliminated any reference to night vision goggles in the proposal. As
an
enhancement to situational awareness, night vision systems such as NVGs provide the pilot an actual visual representation of terrain, weather, and traffic. When utilized by a properly trained crewmember, NVGs provide vital real world information to the user. HTAWS technology has proven its effec-
tiveness in the high-altitude IFR environment, but minimal data exists for its use in the low-altitude helicopter environment.
The FAA Fact Sheet
states, “the FAA concluded that there are a number of issues unique to VFR helicopter operations that must be resolved before the FAA considers mandating the use of TAWS in this area.” On December 17, 2008, the FAA issued
Technical Standards Order (TSO) C-194 to standardize the manufacture of HTAWS within the industry. Even with
this standardization in
place, the benefits of this system to the low-alti- tude helicopter environment have yet to be con- clusively validated or demonstrated. With regard to NVGs, the FAA has stated
their position on the issue in this statement: “While the FAA encourages use of NVGs where appropriate, they are not a one-size-fits-
ROTORCRAFTPROFESSIONAL
all magic bullet. Flying at night is not inherent- ly dangerous if rules and procedures are fol- lowed. In fact, many operators who do not use NVGs have never had an accident at night.” But, it is unquestionable that HTAWS is
also not a one-size-fits-all magic bullet. Many operators who do not use HTAWS have never had an accident at night, either. And, the FAA's statement above is certainly arguable: flying at night at the lower altitudes required by HEMS operations is inherently more dangerous than fly- ing those same missions in full daylight. A pilot's unaided visual acuity on a dark night is approx- imately 20/200, which is legally blind by most accepted definitions. With the current generation of night vision goggles, that acuity is improved to about 20/30 - sometimes a little better, some- times slightly worse, depending on the level of ambient light. To suggest that a technology such as
HTAWS should be preferred in lieu of NVIS, as this NPRM does, is to ignore the realities of fly- ing a helicopter at relatively low altitudes during periods of darkness, sometimes combined with marginal weather conditions. Using NVG's, the pilot sees the terrain in much the same manner as during daylight flying. Even with the somewhat degraded visual acuity and a slight degradation in depth perception, the pilot is able to perceive all the same visual cues that he enjoys during day- light flight. These include the position, shape, size, and apparent distance to all obstacles while at the same time providing a visual indication of the
44
rate of closure with the obstacles, along with other visual cues of the aircraft's position and motion in 3-dimensional space which correlate with
the proprioceptive cues generated by his
physical senses. This ability to see in the dark and to fly by visual reference to the environment out- side the aircraft reduces pilot workload and stress to a level more like daytime flight and lessens the likelihood of vertigo or spatial disorientation in a way that HTAWS symbology cannot. In addition, many pilots are not content to
wait for the audio warning that indicates that the aircraft is on a collision path with the terrain, so they feel a need to shift their attention to the HTAWS cockpit display to confirm that the course and altitude are safe. On a dark night, and without NVIS, the need to do that may be very frequent, especially if the weather is forcing a pilot to fly at the lower altitudes that are allowed by the proposed new rules. For example, flying on a dark night beneath an overcast ceiling, at an altitude only 500 feet above the terrain or the highest obstacle with only 3 miles of visibility (assuming flight within the local flying area), is not a good time to have to keep shifting atten- tion into the cockpit to see what lies ahead. Two other issues that make NVIS a superi-
or solution compared to HTAWS, are the ability to see where the ceiling is above the current flight path and altitude, and the ability for the goggle- equipped pilot to turn his head as needed to locate and select an appropriate forced landing area in the event of an engine failure. HTAWS
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