Cleared and Graded area (CGA): Critical Analysis and Proposal of a Criterion for Grading Its Bearing Capacity

The Italian Standards for the Construction and Management of Airports (II edition – Oct. 2003) define the CGA (Cleared and Graded Area) that portion of the runway strip graded and obstacle-less, with well defined dimensions, aimed to decrease damages risks to aircrafts in case of veer-off. At the chapter 3.3.4, the same standards state that the CGA must be jointed together the runway and it must bear the design aircraft that must be able to run on it with its gross weight without suffering any significant damages. […] The bearing capacity of the CGA may gradually decrease outwards in the cross direction to favourite the aircraft stop. In the same standards, the Italian Civil Aviation Authority (ENAC) gives the 12/31/2005 as expiring date to bring into line with it the bearing capacity of the National airports. Such limitation often generates some uncertainty both to designers and construction contractors on the opportunity and, eventually, on the way of giving this gradual decrease in the bearing capacity. In the paper the authors face this issue through the study of the incidents/accidents for runway lateral excursions occurred from 1980 to 2000 world-wide. The incidents and their consequence have been analyzed in comparison to the lateral excursion range. The risk connected to the over-passing a certain distance from the centreline has been evaluated too. Finally, a criterion is proposed to define the gradation of the CGA bearing capacity