Runway Friction Measurement Standards
Mark Lacagnina’s article “Skidding Off a Cliff” (ASW, 6/12, p. 20) summarizes findings about a number of factors causing a runway overrun with a tragic outcome, based on the English translation of the Norwegian accident report.
I would add a few comments regarding determination of the general friction characteristics which the investigative agency performed and referred to in its accident report, although not decisive for the conclusion and the outcome.
The original report states that the investigative agency performed a friction measurement using a device belonging to the public road administration. This was a “dry” measurement that yielded a friction level of about 0.7. When it comes to friction measurement for design and maintenance purposes, ICAO Document 9137, Airport Services Manual Part 2, governs this area. Similarly, the same, correct procedures are found in FAA Advisory Circular 150-5320. Both refer to the use of water film in conjunction with friction measurement to understand the pavement micro-texture which provides the friction characteristics. This must not be confused with operative braking action assessments.
I am of the opinion that when the investigative agency performed a friction measurement for assessing the runway friction characteristics of this runway, it should have been in conformity with the framework for such procedures set forth by ICAO in Document 9137. To this end, it is also noteworthy that aviation authorities in Norway have made an exemption from ICAO Doc 9137, Annex 14, within this particular area, which is clearly stated in Norwegian Aeronautical Information Publications (AIP) Gen 1.7-14. Furthermore, the same AIP does not describe the type of design and maintenance systems to be used in place of the recommended ICAO system.
Runway excursions are a frequent accident type. Flight Safety Foundation initiated an initiative a few years ago which resulted in the Runway Excursion Risk Reduction (RERR) Toolkit. One of the many recommendations in this tool kit is “to ensure that runways are constructed and maintained to ICAO specifications.”
It is clear that providing good friction characteristics is an important constituent in reducing runway excursions. To what extent various countries follow this particular segment of the ICAO Doc. 9731 is unknown, but Norway is one that does not and is likely not the only one.
Implementing proper design and maintenance systems for runways should be an easy task for virtually all countries, because all procedures and routines are already established and published by ICAO. This is a simple yet important constituent to reduce the risk of runway excursions.
Capt. (retired) Oddvard Johnsen
Reach Should Exceed Grasp
Sometimes, the “we” directed by “them,” the salesmen of rules and theory, forget that in actual practice humanness does experience failure. That same failure can act to encourage us toward the constant improvement of our mastery of the third dimension. I applaud Cliff Jenkins’s brilliant reminder (ASW, 8/12, p. 7) that “quality” often lives just beyond our reach, so that we will keep reaching. To the “reachers,” press on.
Doug Perrill
chief pilot, B2 Flight