# Subject: FAA Inter-Agency Agreement to the Department Of Defense Air Force Research Laboratory (AFRL)/HEC, Wright-Patterson, AFB

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# FAA Technical Monitor: Dr. William K. Krebs, (202) 267-8758

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# (AFRL)/HEC Principal Investigator: Dr. Alan R. Pinkus, (937) 255-8767

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# Project Title: Inexpensive Night Vision Imaging System Field Evaluation Methodology

# Duration: Three Years; Anticipated Award Date April 1^st^, 2002

**Project Summary**:

Interest and use of NVIS technology is increasing. The currently
accepted practice for making a final determination of the compatibility
of a lighting system with a night vision goggle (NVG) is to compare
visual acuity through the NVGs with and without the lighting activated.
The configuration for this procedure was developed by the military and
requires relatively expensive illumination sources and radiometric
measurement equipment (costs in excess of \$100K). In addition, the
military method has not been validated for repeatability or
reproducibility. The RTCA organized a special committee (SC-196) to
address the area. This committee has described one method for
determining NVIS acceptability that is very similar to the method
employed by the military, which uses relatively expensive equipment.
Although this procedure developed by the military and supported by the
RTCA committee is the only one proven to be safely employed as an
effective evaluation process, applicants applying for NVG certification
have the right to not use this method if another method is appropriately
documented and justified. As a result, the FAA and DOD are concerned
that alternate means of compliance that are suggested from applicants
may not be totally proven safe and the FAA will be confronted with
unverified alternative methods by applicants who cannot afford the
expensive equipment that is used in the evaluation process developed by
the military.

**Objectives**

Currently two technical approaches are envisioned for this effort. The
first approach will investigate possible NVIS compatibility test
methodologies that do not depend on any type of measurement equipment
and the second approach will investigate methods that require a bare
minimum of inexpensive or easily fabricated equipment. An example of the
first approach is to have observers make judgments on light level by
viewing through the NVGs. It is not critical to know the exact light
level but rather just that the NVGs are operating at their optimum. This
occurs if the NVG is providing a lot of light output but is not
saturated. One way of judging this light level condition may be to have
the observer increase the light level until the NVG output scene does
not get any brighter. Then have the observer lower the light level until
the output is judged to be about 80% of the saturated level. The actual
light level would not be known but even with a considerable margin of
error on the judgment of the 80% level (say from 95% down to 50%) this
would still mean the NVGs are operating at optimum. In a similar
fashion, a cheap, non-calibrated light meter could be attached to the
output of the NVGs to achieve an output level of about 80% of saturated
using the same basic technique.

Since the accepted military technique has not been tested for
repeatability and reproducibility it will be necessary to devise a means
to accomplish this test. To this end a laboratory-level simulation of an
NVIS cockpit will be fabricated and evaluated with the existing
military-approved evaluation methodology. This simulated cockpit will
include a means to adjust the level of compatibility (e.g. by changing
cockpit light level or spectrum) so that the approved evaluation
methodology will result in three possible conditions. These conditions
will be: a pass condition (no loss of VA), a marginal pass condition
(loss of only 1 element level -- 12.25%), and a fail condition (loss of
2 element levels -- 24.5%). The methodologies developed will be tested
against this "calibrated" simulated cockpit to determine if they
reliably produce the same results. At least two organizations should
verify the compatibility nature of the simulated cockpit. These will
most likely be AFRL/HEC at Wright-Patterson AFB, OH and either AFRL/HEA
at Mesa, AZ or NAWC at Patuxent River, MD.

## **Benefits to the FAA and the aviation maintenance industry:**

-   It will identify an alternative method to measure NVG cockpit
    lighting compatibility that is as valid and reliable as the accepted
    military methodology.