Recommendation

OCCURRENCE SUMMARY



While taxiing on a non-active runway at Moorabbin, the pilot of the
aircraft crossed the duty runway without a clearance. The pilot
later reported that he had become confused, and considered that the
markings to indicate the approach to the active runway were
inadequate.





SAFETY DEFICIENCY



Moorabbin has no runway markings in the form of "taxiway hold point
lines", or signs to indicate to a pilot that his aircraft is about
to infringe the flight strip of an active (duty) runway.





BACKGROUND





Moorabbin airport operations



The investigation of this occurrence revealed that when aircraft
are being taxied on non-active runways, there are no signs or
runway markings to indicate to pilots that the aircraft is about to
infringe the flight strip of the duty runway. For example, when
pilots are taxiing on runway 22/04 and approaching 13R/31L or
17L/35R, they must rely on being able to view the gable markers of
the active runway's flight strip in order to make an assessment of
when to stop and seek a clearance to cross the active runway. On
some occasions, pilots may not easily acquire the visual cues
provided by gable markers due to their distance/spacing from the
runway and other factors such as the nature of the runway strip
surface. On these occasions, pilots must make a subjective
judgement. Without cues such as guidance signs or runway markings,
it is more likely that pilots will misjudge their position in
relation to the flight strip, or that thay will continue onto the
active runway without a clearance, having given little or no
conscious thought to the need to stop. Such information signs are
in use at Melbourne aerodrome.



A Moorabbin tower controller confirmed that it is common practice
to use non-active runways as taxiways in order to make best use of
aerodrome resources and, in turn, maintain an efficient flow of
traffic. The Bureau was informed that Melbourne aerodrome also uses
runways as taxiways in times of low traffic density. As this
practice appears to be a commonly accepted and utilised one, the
requirement for appropriate information signs on runway-to-runway
intersections may need to be addressed.





Reference material pertaining to runway and taxiway signs and
markings



(1) The Rules and Practices for Aerodromes handbook



The Rules and Practices for Aerodromes handbook, issued by the
Civil Aviation Safety Authority (CASA) for use by operators of
licensed aerodromes, contains a number of references relating to
taxiway signs. The emphasis, however, appears to be on taxiway
markings/signs. Limited guidance is provided on runway-to-runway
intersection markings/signs.



Chapter 11 Visual Aids - Day, paragragh 2.1, states that "visual
aids are cues for pilots, marshallers, air traffic controllers and
ground vehicle drivers to help them in ensuring safe aircraft
operations. Visual aids assist pilots to locate an aerodrome,
determine the areas of an aerodrome upon which it is safe and
permissible to land and take off, taxi aircraft safely on the
movement area, and precisely position aircraft on the apron".



Paragraph 8.4 states that "taxi holding position markings are used
to indicate to pilots positions along taxiways at which they must
temporarily hold their aircraft when a runway ahead is occupied by
another aircraft, or when so instructed by ATC. They are to be
provided on all asphalt, sealed or concrete taxiways wherever these
join or intersect with a runway". However, there is no reference to
runway-to-runway intersection markings.



Chapter 12 Movement Area Guidance Signs (MAGS), paragraph 12.5,
states that "MAGS with information are normally provided where the
aerodrome has multiple runways and a complex taxiway system. It is
an inexpensive way to maintain the movement rate of aircraft on the
taxiway, particularly in reduced visibility conditions". Again,
there is no reference that specifically covers runway-to- runway
intersections.



Paragragh 12.21 states that "intersection signs are information
signs, which provide advice to pilots on the designation of the
runway or taxiway about to be joined or crossed. When used, one
intersection sign is to be provided for each direction, at the
left-hand side of the taxiway as viewed by the pilot, prior to the
relevant taxiway intersection. The inscription on the sign is to be
the designation of the taxiway(s) being approached, as shown in Fig
11.62". This again appears to emphasise the taxiway-to-runway
intersections, not runway-to-runway intersections.



(2) Aeronautical Information Publication (AIP)



The AIP defines a taxi holding point as "a designated position on a
taxiway, runway or channel at which aircraft may be required to
stop pending receipt of permission to proceed". The inference from
this reference is that holding points may be designated for
runways.



(3) The International Civil Aviation Organisation (ICAO) Annex
14-Aerodromes



This publication contains specific references to runway-to-runway
intersections and indicates the requirements that must be met in
relation to runway markings/signs.



Paragraph 5.4.2 - Mandatory instruction signs



5.4.2.1 "A mandatory instruction sign shall be provided to identify
a location beyond which an aircraft taxiing or vehicle shall not
proceed unless authorised by the aerodrome control tower".



5.4.2.2 "Mandatory instruction signs shall include runway
designation signs, category I, II or III holding position signs,
taxi holding position signs, road holding position signs and no
entry signs".



5.4.2.3 "A pattern "A" taxi-holding position marking shall be
supplemented at a taxiway/runway intersection or a runway/runway
intersection with a runway designation sign". A taxi-holding
marking on a runway is a further defence to the runway designation
sign.



Paragraph 5.2.9.6 "The taxiway holding position marking displayed
at a runway/runway intersection shall be perpendicular to the
centreline of the runway forming part of the standard
taxi-route".





SUMMARY



There appears to be an accepted practice of using runways as
taxiways for the management of aircraft traffic at aerodromes with
multiple runways and complex taxiway systems, such as Moorabbin.
Guidance available to aerodrome operators for the use of runway
markings and/or signs for runway-to-runway intersections, is
limited and does not appear to be adequately addressed.
Consequently, there is a need to consider the requirement for a
specific and unambiguous system of markings and/or signs in order
to prevent the possibility of collisions, particularly at
runway-to-runway intersections.