Aircraft Operations. Volume II - Construction of Visual and Instrument ...

Appendix D to Chapter 1
INDEPENDENT PARALLEL APPROACHES TO
CLOSELY SPACED PARALLEL RUNWAYS
1. INTRODUCTION
1.1 Independent parallel approaches to closely spaced parallel runways are allowed when the distance between
runways is not less than 1 035 m. To guarantee the safety of such operations, an obstacle assessment has to be carried
out to protect a lateral break-out manoeuvre, which may need to be executed to avoid collision with a potential
blundering aircraft. This will provide obstacle clearance from obstacles in the areas adjacent to the final approach
segments.
1.2 The following method provides an example for the assessment of these obstacles and was derived from an
existing procedure used by one State. This section includes the considerations made in developing the basis for the
assessment.
1.3 It was considered that a difference exists between the current precision approach procedures described in
Chapter 1, “Instrument landing system (ILS)” and Chapter 3, “MLS”, and the break-out procedures. For the approach
procedures, an extensive data collection could be performed from which statistical probabilities of aircraft distributions
could be obtained. In establishing a target level of safety (TLS) of 10 -7 , obstacle assessment surfaces (OAS) and the
collision risk model (CRM) are derived. For the assessment surfaces of the break-out manoeuvre, this type of method
was not considered feasible due to the low probability of occurrence of a break-out manoeuvre. From one State’s
report, it was learned that the occurrence of a break-out during simultaneous approaches was initially assumed to be in
the order of 10 -4 and 10 -5 per approach and may even be lower.
1.4 In order to find obstacle clearance criteria for break-out manoeuvres, other methods were considered. One
way was to use the existing missed approach criteria. However, these criteria are based on an occurrence of 10 -2 which
may be unduly restrictive at some aerodromes, and missed approaches are not primarily designed for break-out
manoeuvres.
2. PARALLEL APPROACH OBSTACLE ASSESSMENT SURFACES (PAOAS)
2.1 The proposed method for the obstacle assessment for simultaneous parallel approaches was based on existing
criteria provided by one State (FAA Order 8260.41). An evaluation was carried out by the Obstacle Clearance Panel
(OCP). This evaluation was made by means of certification and operational criteria contained in the FAR/JAR 23/25
minimum climb requirements with all engines operating, together with the operational assumptions made by the ICAO
Study Group on Simultaneous Operations on Parallel or Near-parallel Instrument Runways (SOIR), which established
the minimum runway separation for use with simultaneous independent precision approaches (Cir 207). The evaluation
considered that the initial part of the break-out manoeuvre would be executed in the landing configuration, followed by
a climb gradient of 8.3 per cent within a height of 120 m (400 ft) above the break-out altitude/height. This evaluation
indicated, in general, that the following restrictions to the break-out manoeuvres were necessary:
a) no break-out manoeuvres below 120 m (400 ft); and
II-1-1-App D-1 23/11/06