Div 11Frangibility of markers and signs

Division 11 Frangibility of markers and signs

8.112 Markers

(1) To meet the frangibility requirements of this MOS, the materials used in markers must:

(a) have a low modulus of toughness; and

(b) be sufficiently strong and lightweight for the purpose of the marker.

Note In general terms, toughness is defined as the capacity of a material to resist fracture under dynamic loads. The modulus of toughness is the ultimate amount of energy by volume that a material will absorb and is determined by measuring the area under the material’s stress-strain diagram when plotted to failure. Minimum weight is important to ensure that the least amount of energy is expended to accelerate the mass to the velocity of an impacting aircraft. Further information is available in ICAO Document 9157, Aerodrome Design Manual, Chapter 6 – Frangibility. For ICAO documents, see section 1.07.

(2) Frangible materials must withstand, or be protected from, outdoor environmental effects, including weathering, solar radiation and temperature fluctuation.

(3) If weights or fixtures are used to hold markers in place, the weights or fixtures must:

(a) themselves be frangible; and

(b) not compromise the frangibility of the marker.

8.113 Movement area guidance signs

Note Movement area guidance signs include (a) mandatory instruction signs, such as runway designation signs, CAT I, II and III holding position signs, runway holding position signs, road-holding position signs and no entry signs; and (b) information signs, such as direction signs, location signs, runway exit signs, runway vacated signs and intersection take-off signs.

(1) Movement area guidance signs (MAGS) must be:

(a) frangible; and

(b) constructed of lightweight materials.

Note CASA recommends that MAGS should be designed for installation on a concrete pad or on stakes. All required mountings or support hardware should be regarded as part of the sign for frangibility purposes.

(2) The overall width of a MAGS, including its mounting, must not exceed 3 m.

Note If the total message does not fit on a 3 m sign, CASA recommends that 2 separate signs mounted side‑by-side should be provided.

(3) Each mounting leg or stake for a MAGS must have a frangible point located not more than 50 mm above the ground on which the MAGS is located.

(4) Each frangible point mentioned in subsection (3) must:

(a) be capable of withstanding the wind loading delivered by the maximum jet blasts of the aircraft for which the aerodrome is designed; and