In 2006, the frangibility and deflection/wind speed requirements of approach lighting masts and other obstacles were more clearly defined with the publication of the ICAO’s Aerodrome Design Manual, Part 6 Frangibility. A manual designed to be read in conjunction with Annex 14 but offering clearer guidance on the design, testing and installation of frangible structures at airports. Frangible objects, as defined within the manual were to be of a low mass and designed to break, distort or yield on impact presenting a minimum hazard to an aircraft.
Annex 14 Vol 1 Chapter 9 specifies in detail the equipment and installations of operational significance on the airfield which should be frangible; including:
ICAO’s Aerodrome Design Manual, Part 6 Frangibility looks more closely at the design, siting and testing requirements for operational equipment that is required to be frangible.
"The frangibility of any aid should always be proven before the aid is considered for installation"
The manual sets out a general expectation for testing of frangible masts including procedures and acceptance or rejection criteria.
Testing for Frangibility
“High Speed, full scale testing is a proven method for verification of frangibility” - 5.1.2 Testing for Frangibility ICAO Aerodrome Design Manual Pt 6
Within this ICAO design manual is the clear guidance that frangibility in masts exceeding 1.2m must be verified through full scale dynamic testing to ensure full compliance with the above mentioned criteria. This testing is specifically recommended for:
FAA Advisory Circular No. 150/5345-45C Low Impact Resistant Structures
As with ICAO the FAA issued in March 2007 an advisory circular with their own specifications for frangible masts used to support approach lighting systems. With specific regard to frangibility the FAA circular follows the same frangible design goals as ICAO’s Design Manual.