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Section 6.5.1

Experimental Design for NLSI Research Program on Comparative Behavior of Air Terminals


What air terminal (AT) tip geometry performs better as a preferential attachment point for lightning? Project No. 199 continues earlier work on this issue conducted by New Mexico Tech from Moore, Rison, et al (1998).

Experimental Design

Site - The CU INSTAAR site on Niwot Ridge, elevation 12,000 ft., was selected because of the high (100+TDY) assumed level of thunderstorm days. Travel time from Boulder, CO is about 2+ hours
Distribution of experimental stations - Ten stations each are installed on the east (elev. 11,679) and west (elev. 12,284) knolls of Niwot Ridge, at approx N 39 58 45.2 and W 105 08 38.0. The site is situated about 30 miles west of Boulder, CO. (see installation details and examples)st - All of 1999 season and, year 2000 +.
Equipment - 80 copper-clad steel air terminals, 5/8 dia. X 4 ft high, are mounted in clusters of four rods per wooden sawhorse platform. 20 amp fused sensors are attached to each platform to provide lightning attachment verification. 20 sawhorses are deployed. Four AT tip designs are being studied: blunt; hemispheric, bullet-shaped; and sharp…one of each at each sawhorse. Visual observation of tip arcing will indicate which geometry was preferred after a lightning strike has occurred. See installation details.

Data Collection

Equipment will be checked often. Struck terminals will be replaced.

INSTAAR is informed of test results as observations are recorded. Summaries will be posted periodically. All materials will be removed from Niwot Ridge at completion of testing.

Site Safety

Proximity to sawhorses during close-in lightning should be avoided. Plastic-laminated safety signage will be displayed at all sawhorses. The signage will describe the purpose of the test program, as well basic lightning safety measures.


Ongoing results are available. The site has been prepared for winter and will be reopened in spring when accessible. Stay tuned.

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Providing expert training and consulting for lightning problems