Draft ICAO Circular on NLA.pdf - Airports Council International

<strong>ICAO</strong> Version 4.1 — 15 March 2004
-28-
b) collision risk between an aeroplane leaving the runway and an object (fixed or mobile)
on the aerodrome or collision risk between an aircraft which runs off the taxiway into
the runway strip; and
c) ILS signal interference due to a taxiing or stopped aeroplane.
4.1.6.2.2 The first two hazards are potentially catastrophic and the third one is potentially major.
4.1.6.2.3 Main causes and accident factors are:
a) human factors (crew, ATS);
b) weather conditions (visibility);
c) aircraft mechanical failure (engine, hydraulic system, flight instruments, control
surfaces, auto pilot, etc.);
d) surface conditions (standing water, loss of control on ice-covered surface, friction
coefficient);
e) lateral veer-off distance;
f) aeroplane position relative to navaids, especially ILS; and
g) aeroplane size and characteristics (especially wing span).
4.1.6.2.4 Common accident/incident databases deal with lateral runway excursions and do not include
accident reports relative to in-flight collision and ILS signal interference. Therefore, the causes and accident
factors specific to the local environment and identified above for runway separation issues are mainly
supported by local aerodrome experience. The huge variety and complexity of accident factors for collision
risk should be emphasized.
4.1.6.3 Risk assessment and possible mitigation measures
Collision between an aircraft in flight and an object (fixed or mobile) on the aerodrome
4.1.6.3.1 The <strong>ICAO</strong> Obstacle Clearance Panel is conducting a study on NLA balked landing
operations. Some simulation tests are still to be done before analyses and final conclusions for all aircraft
operating modes (Autoland, Flight Director and visual approach conditions) are reached.
Collision between an aircraft veering off the runway and an object (fixed or mobile) on the aerodrome
4.1.6.3.2 The Aerodrome Design Manual, Part 2, paragraph 1.2.19 states “Separation distances are
based on the concept of the wing tip of an aircraft centred on a parallel taxiway remaining clear of the strip”.