Draft ICAO Circular on NLA.pdf - Airports Council International

<strong>ICAO</strong> Version 4.1 — 15 March 2004
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4.1.2.7 Risk assessment and possible mitigation measures
4.1.2.7.1 The hazards listed above are dependent on the relationship between the shoulder width, the
bearing capacity and the critical characteristics of the aeroplane (overall mass, gear width and configuration,
wingspan, outer engine position). Possible mitigation measures are:
a) Prevention of damage to aircraft after incursion onto runway shoulder. To prevent
structural damage to aircraft in case of veer-off from a runway which does not meet
Annex 14, Volume I specifications for a code F aircraft, hard shoulders to ensure at least
an overall width of the runway and its inner paved shoulders of 60 m should be provided
to allow pilots to steer the aircraft back onto the runway. The thickness and composition
of shoulder pavements would need to be such as to withstand the occasional passage of
the aeroplane that has the most demanding pavement loading impact, operating at the
airport, as well as the full load of the most demanding airport emergency vehicle. The
impact of an NLA on pavements should be assessed and, if required, existing runways
and taxiways (if allowed to be used by these heavier aeroplanes) may need to be
strengthened by providing a suitable overlay. Similarly, the existing shoulders also need
to be evaluated for adequacy.
b) Jet blast issue. Information about outer engine position and jet blast velocity contour
at take-off is needed to calculate the required width for jet blast protection. Jet blast
velocity data is available on the respective manufacturers Web sites. Lateral deviation
from runway centre line should also be taken into account. Regarding the risk of
ingestion of foreign objects by the outer engines, additional data on ingestion tendency
in front of these engines at take-off thrust are, in theory, needed before drawing any
conclusions. Nevertheless, a comparison with the respective geometry of current large
aircraft operations on existing runways helps to provide a better understanding of the
issue. The dimension to be considered should include the margins between outer engine
axis and edge of shoulder, and the distance from the outer engine to the ground.
c) RFF vehicles intervention. Operational experience with current large aircraft on
existing runways suggests that an overall width of the runway and its shoulders of 75 m
may be adequate for occasional RFF vehicle traffic in order to permit intervention to
NLA (code F) at least as easily as for the current code E aircraft on a code E runway.
However the longer extension of upper deck escape chutes may reduce the margin
between the shoulder edge and the extremity of these escape slides and reduce the
supporting surface available to rescue vehicles. Additional <strong>ICAO</strong> guidance material is
under development, and will be issued later.
4.1.3 Runway strip and runway end safety area
4.1.3.1 Runway strip and runway end safety area are based on the runway length classification and
instrument approach classification. The runway strip is intended to provide an area free of fixed and moving
objects in order to permit safe landing and take-off of aeroplanes using the runway. Particularly, the graded
portion of the runway strip is provided to minimize the damage to an aeroplane in the event of a veer-off
during a landing or take-off operation. It is for this reason that Annex 14, Volume I requires objects to be
located away from this portion of the runway strip unless they are needed for air navigation purposes and
are frangibly mounted.