Evaluation of Minimum Approach Light System for Lower Activity Airports

Flight tests were conducted during actual Category I weather conditions at the National Aviation Facilities Experimental Center (NAFEC), Atlantic City, New Jersey, to determine the suitability of three approach light patterns in providing guidance for aircraft approach speeds of 125 knots using ILS into lower activity airports. Each pattern tested provided less visual guidance (fewer lights) than the U.S. Standard Approach Light System. A fourth pattern which was not available during
the weather period will be evaluated and test results reported at a later date.

It was concluded that the minimum pattern provided adequate visual guidance in a Category I visibility condition with a high approach success rate provided a minimum decision height of 150 feet is authorized with reported ceilings of 200 feet and higher.

Several amendments to operating practices were suggested to permit flight to a minimum decision height below a reported ceiling height.

It was also concluded that runway visual range alone provided a poor indication of what approach light contact height to expect and, consequently, there was a requirement to provide slant visibility measurements to improve the approach success rate.