RUNWAY COLLISION RISK
- SETTING THE CONTEXT
Captain Ed Pooley
The Air Safety Consultancy & FSF European
Advisory Committee
5th Brussels Safety Forum 2017
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40 YEARS AGO - THE BIGGEST
SINGLE LOSS OF LIFE IN AN
AIRCRAFT ACCIDENT WAS A
RUNWAY COLLISION
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On 27 March 1977, two Boeing 747s collided on the runway at Tenerife
(now Tenerife North) because the Captain of one of them began take off in
fog without clearance and was not challenged by the other two flight crew
despite indications that they were aware of his error and of another aircraft
ahead on the runway.
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583 people died and 61 survived.
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Fortunately, times have changed and absolute authority has been replaced
by the concept of CRM.
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But much of the other circumstantial context of this accident remains…..
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TENERIFE - THE SCENARIO
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Poor day visibility of around 300 metres in fog.
A late sighting as the 747 taking off was beginning to rotate.
The other 747 had already advised that it was still backtracking on the
runway.
There were no restrictions on minimum taxiing visibility.
There was no measurement of RVR but there was visibility sensor near the
beginning of the take off runway.
The runway centreline lighting which was required to determine whether
the visibility was sufficient for a take off to commence was inoperative.
Imprecise communication between ATC and both aircraft involved was
partly attributable to a combination of the controller being a non-native
English speaker and pilot use of non standard phraseology open to
misunderstanding.
The evidence indicated that the Captain of the aircraft taking off without
clearance had been under self-imposed pressure to minimise departure
delay.
It was an unusually busy time at a normally relatively quiet airport due to
multiple unexpected diversions and a shortage of parking space.
There was no surface movement radar display.
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SINCE THEN….
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There have unsurprisingly been very big improvements in relevant aircraft
operation, ATC and aerodrome procedures and in aerodrome signage,
markings, lighting and charts but there have still been nine more fatal
runway collision accidents involving ‘Western’ aircraft conducting
commercial air transport flights which have killed 182 people. These
accidents show that some aspects of the risks at Tenerife still remain –
along with many more opportunities for risk management.
There have also been many more non-fatal runway collision accidents
involving these and other aircraft with a range of contributory factors.
And the context for these accidents has been a huge number of Runway
Incursions after which the extent of the subsequent investigation has been
largely predicated on the actual risk of collision assessed after any avoiding
action has mitigated that outcome – just as with AIRPROX and airborne
collision risk - rather than the potential to learn new lessons.
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MADRID 1983
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What Happened
A Boeing 727 taking off in daylight from Madrid as cleared had reached V1 when,
after a very late sighting, it unavoidably collided with a DC9 which had been cleared
to taxi to the full length holding point of the same runway but had failed to follow its
clearance and inadvertently entered the take off runway at its intersection with
another runway about one third of the way along its length. 93 people were killed
and 30 others seriously injured.
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The Context
Thick early morning radiation fog with an RVR of 200 metres or less in the vicinity of
the runway intersection near where the collision occurred.
Both aircraft were Spanish-operated.
Guidance needed for the DC9 to safely acquire the correct taxiway in such low
visibility was poor.
The DC9 crew made no attempt to use their compasses to confirm they were on the
correct taxiway.
The available evidence indicated that about 30 seconds prior to impact, the crew had
finally suspected that they might have entered a runway. This uncertainty was not
reported to ATC and 8 seconds later, in the absence of a requested position report
from the DC9 during its taxi out, the GND controller requested its position and it
became clear that the crew were probably lost. Before further clarification could be
obtained, the collision occurred.
ATC visual surveillance was impossible and there was no surface movement radar.
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ATLANTA 1990
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What Happened
The crew of a Boeing 727 cleared to land without conditions in sequence
behind a King Air A100 did so but during deceleration after touchdown saw
the King Air ahead and about to exit the runway too late to avoid a
collision. One of the two pilots in the King Air was killed and the other
seriously injured.
The Context
Good night visibility
The anti collision lighting on the King Air was deficient - both the upper and
lower anti collision beacons and the tailcone strobe light were inoperative.
Both aircraft had flown their approaches in accordance with ATC
sequencing instructions but these were insufficient to maintain the
prescribed minimum separation between them. The runway controller had
failed to monitor separation or give the 727 crew traffic information on the
aircraft ahead after becoming distracted and the approach radar controller
had failed to issue timely speed reductions.
Inadequate ATC procedures were found not to allow for the potential
consequences of inevitable lapses in controller normal performance.
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DETROIT 1990
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What Happened
A DC9 taxiing for a daylight departure failed to follow its taxi clearance and
eventually entered the active runway where it stopped at one side shortly
before being hit by a Boeing 727 taking off and about to rotate. 8 people
were killed and 10 seriously injured.
The Context
Thick Fog (effective forward visibility less than 400 metres), no time for
effective avoiding action by the 727 crew.
A DC9 Captain on his first flight after a licence medical suspension lasting
almost 7 years; conclusive evidence of command weakness in the face of
an over confident F/O.
Prolonged DC9 crew doubts about their position and failure to advise ATC;
no use of the compass to detect gross taxi error.
No use of progressive taxi instructions by ATC.
No controller use of available surface monitoring display to detect taxi error.
Deficient surface markings, signage & lighting undetected by FAA
inspections.
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LOS ANGELES 1991
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What Happened
As a Boeing 737-300 touched down on the full length of the runway at
night, its crew immediately saw a smaller aircraft - a Metroliner - stationary
on the runway ahead of them too late to avoid it and a collision followed.
Both aircraft were being operated in accordance with their clearances. 34
people were killed and 13 seriously injured.
The Context
Good night visibility.
The Metroliner was difficult to see because:
Its anti-collision beacon was on but obstructed from view by the
empennage
Its strobe lights were off because procedures only required them to be
switched on upon receipt of a take off clearance.
Its white tail navigation light was likely to have been virtually
indistinguishable from the white runway centreline lighting
The controller who issued both clearances was found to have been
previously identified as having deficiencies indicative of weak performance
which had not been adequately addressed
Inadequate ATC procedures undetected by regulatory oversight
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ST. LOUIS 1994
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What Happened
The pilots of an MD-82 taking off from St Louis in accordance with their
ATC clearance and past the 80 knot call suddenly became aware of a
smaller aircraft - subsequently found to have been a Cessna 441 - which
had failed to follow its departure taxi clearance and was stationary ahead
on the runway. With no time for avoiding action, a collision followed and 2
people were killed.
The Context
Good night visibility.
The wing tip-mounted anti collision/strobe lights on the Cessna had not
been on making it difficult to see.
The Cessna pilot had been given clearance to taxi to and line up on a rarely
used secondary runway parallel to the accident runway on which he had
recently landed and report ready to GND as this runway was not yet active
and therefore remained under GND control.
An incomplete read back of this taxi clearance which omitted any reference
to the runway designation went unchallenged.
There was no reference on the ATIS to the departure runway given to the
Cessna and no other ATC information regarding its occasional use.
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QUINCY, ILLINOIS 1996
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What Happened
As it decelerated after touchdown at the uncontrolled aerodrome at
Quincy, Illinois, a Beech 1900C collided with a King Air A90 which had
commenced take off on an intersecting runway at that intersection. All 14
occupants of both aircraft were killed.
The Context
Good daylight visibility.
No impediment to sight of the Beech 1900 by the King Air pilots during
most of its 6 mile final approach.
The failure of the King Air pilots to effectively monitor the CTAF or properly
scan for potentially conflicting traffic before beginning their take off.
The King Air pilots did not respond to a short final transmission on the CTAF
from the Beech 1900 crew seeking to clarify if they were going to roll
before or after their landing but an inappropriate & interrupted response
from a third aircraft waiting to take off behind the King Air led the Beech
1900 crew to conclude that the King Air would wait until they had landed
before beginning its take off.
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PARIS CDG 2000
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What Happened
An MD83 on a full length night take off in accordance with its ATC
clearance was unable to avoid a high speed collision with a Shorts SD330
which had incorrectly begun to enter the same runway at an intersection
after being conditionally cleared to do so. One of the pilots of the 330 was
killed and the other was seriously injured.
The Context
Visibility was good but light pollution aggravated by the illumination of
construction work compromised the runway controller's view of the runway
and the available surface movement display showed only unidentified
primary targets and was difficult to read.
Although the GND controller had cleared the 330 to an intermediate
holding point on one of the opposite-direction RETs and annotated the strip
accordingly, the runway controller did not notice this and assumed that the
330 was proceeding for a full length take off behind the MD83.
The use of two languages for ATC radio communication meant that the 330
crew were unaware as they began to taxi towards the runway that the
MD83 had received a take off clearance (in French). The MD83 crew
assumed that the 330, whose conditional line up clearance in English was
understood, was behind them.
ATC procedures were, in general, found to be poorly documented
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MILAN LINATE 2001
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What Happened
An MD87 taking off in accordance with its ATC clearance and beginning
rotation was hit by a Cessna Citation which had failed to follow its taxi
clearance. The collision killed 118 people and seriously injured one.
The Context
Thick Fog - reported visibility was around 50 metres and RVR 200 metres.
To enter the runway, the Cessna crossed a permanently lit red stop bar.
Taxiway centreline lighting could only be switched all-on or all-off.
ATC surface radar had been de-activated continuously for almost two years.
The Citation Crew did not declare their apparent uncertainty about their
position to ATC and their call indicating that it was not taxiing as cleared
was not recognised as such by the GND controller.
The very low visibility meant that the intended take off would have been
well outside the minimum permitted under both Operator and aircraft
certification and the pilots were not trained for such operations.
The Citation had arrived earlier on a positioning flight and landed off an ILS
approach in Cat 3 conditions when the aircraft was only certified to operate
to Cat 1 minima. The intended take off would have been in visibility well
below that permitted under both the AOC and aircraft certification and the
pilots were not trained for such operations.
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MOSCOW VNUKOVO 2014
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What Happened
The crew of a Falcon 50 taking off at night from Moscow Vuknovo in
accordance with their ATC clearance initially sighted a 'vehicle' moving
across their runway some distance ahead and then apparently saw a
stationary snowplough 200 metres ahead at the intersection of their runway
and another one closed for snow clearance. An attempt at an early rotation
was unsuccessful and the collision killed all 4 occupants of the Falcon 50.
The Context
Fog with 350 metres visibility was being reported but the relevant RVR was
stable at 1000 metres and it was concluded that restricted visibility had not
hindered visual acquisition of the obstruction.
Procedures for control of snow clearance on the intersecting but closed
runway were both inadequate and, to the extent that they functioned at all,
were ineffective.
An A-SMGCS installed over a year prior to the collision had not been
properly configured nor had controller training been conducted. Its conflict
alerting functions were effectively non functional and it was not being used
to enhance controller situational awareness.
The runway controller was supervising an ab-initio trainee.
The unexplained performance of the snowplough driver involved may have
been affected by his consumption of alcohol whilst on duty.
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THE PREVALENCE OF SOME
RECURRENT FEATURES
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A late sighting made avoiding action impossible [10]
At least one departing aircraft was involved [9]
The primary cause of the collision was pilot non-compliance with
ATC clearance [7]
No system for display of ground movements to controllers was
installed [6]
Two departing aircraft were involved [6]
Good visibility at night [5]
Thick fog in daylight [4]
The primary cause of the collision was ATC error [3]
Inadequate aircraft conspicuity in good night visibility [3]
Delay in pilots uncertain of their position declaring this to ATC [3]
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TOWED AIRCRAFT - A RISK
MISSING FROM THE FATAL
ACCIDENT RECORD
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Two significant near misses in the 40 year period reviewed are worth recall:
In 1998, a Boeing 767 taking off from Amsterdam in day visibility
which precluded controller visual surveillance was just able to see a towed
Boeing 747 crossing the runway ahead in time to stop. Both clearances had
been given by the runway controller but that for the towed aircraft was
given to the tow vehicle on the GND frequency where it remained in the
local language.
 Access to active runways for vehicles was enabled on a different
frequency to that used by aircraft moving under their own power.
In 2016, a Boeing 737 taking off at night from Jakarta Halim in
good visibility was unable to avoid an ATR42 under tow which had entered
the active runway in the opposite direction without clearance. A collision
followed with consequent fuel fed fires in both aircraft.
 Access to active runways for vehicles was enabled on a different
frequency and language to that used by aircraft moving under their
own power.
Both events arose from inappropriate controller action and resolution relied
on pilot/driver situational awareness which was unsupported by the
opportunity to monitor all runway access clearances on a single frequency.
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SOME OF THE USEFUL
RESPONSES SO FAR
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The widespread introduction of TWR/GND controller access to both surface
movement and approach radar displays to supplement/replace reliance on
visual awareness of relative traffic positions.
The development and deployment in the USA of two complimentary
systems - RWSL and FAROS - to directly and autonomously warn
pilots/drivers at complex aerodromes of a runway collision risk regardless of
its origin.
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The spread of ATC-controllable stop bars and taxiway centreline lighting.
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The widespread adoption of appropriate ATC and Pilot SOPs and of at least
ICAO-standard aerodrome taxiway designation, signage and markings.
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The widespread introduction of Runway Safety Teams and aerodrome Hot
Spot designation.
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SOME POTENTIAL ACTIONS (1)
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All Runway Safety Teams to have effective representation of non-based
aircraft operators and clear links to post holding decision makers whose
responses to any proposals made are documented.
A continued focus on achieving more effective and consistent monitoring on
flight decks especially in respect of compliance with taxi clearances.
A global review of the criteria being used for the designation of Hot Spots
to achieve consistency and the introduction of periodic review for all such
designations which requires documented justification for their continued
designation in place of alternatives.
Every vehicle permitted to operate in the vicinity of an active runway to
have two equally qualified occupants with a clear forward view and robust
defences to ensure that vehicles without such occupants do not exceed
their restricted area of airside operation. Where the nature of the vehicle
concerned makes this impossible, a compliant escort vehicle should be
provided.
Careful control of runway lighting intensity at night is essential to avoid
degrading pilot/driver vision by excessive brightness. Where take offs are
commenced from the full length of a displaced threshold runway, this
control must include the final segment of the approach lighting.
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SOME POTENTIAL ACTIONS (2)
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Restrictions on all aircraft/vehicle ground movements when visibility is
below that required for a Cat 1 approach which are supported by the
automatic measurement of visibility on active runways and in their vicinity.
Such restrictions should take into account whether a surface movement
screen display is available to controllers and be more limiting if it is not
installed or temporarily unavailable.
Where the adequacy of external lighting of small aircraft relative to larger
ones is assessed to result in poor aircraft conspicuity at night even in good
visibility, individual aerodromes might consider either proscribing night
operations by such aircraft or consider prohibiting their line up at
intermediate points on a mixed mode runway at night.
New small aircraft designs should ensure that aircraft external lighting
aimed at aiding conspicuity is considered for the ground case as well as the
airborne one.
Aircraft runway entry for take off should permit the approach and any part
of the runway prior to that point to be visually checked for other traffic.
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SOME POTENTIAL ACTIONS (3)
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Aircraft Operator SOPs should include a crew check of the TCAS display
immediately prior to entering an active runway.
Mandate controllable red stop bars at all active runway access points and
require alternative procedures in the event of unserviceability that are
universal and no less robust.
The 24/7 use of controllable taxiway centreline lighting should be promoted
where appropriate, especially where the response to a perceived
heightened risk of error is the designation of a Hot Spot.
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The universal use of a single frequency for the control of access to an
active runway including the request for and issue of all clearances.
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The universal use of a single language on any frequency used for active
runway control with language competency requirements to match.
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AIP alerting to runway longitudinal profiles which may impede visibility
along the runway when pilots check that a runway is clear before beginning
take off or when lining up at an intermediate point.
The use of progressive taxi clearances in low visibility.
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SOME POTENTIAL ACTIONS (4)
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All vehicles towing aircraft must be in two way contact with ATC and the
aircraft and those on the aircraft flight deck must be able to communicate
with the towing vehicle and at least monitor the communications on the
runway control frequency.
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Towed aircraft must always be illuminated to the same standard as aircraft
moving under their own power.
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Unambiguous procedures for changing the status of a runway between
active and inactive both as part of a daily routine or ad hoc.
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Adoption of RWSL and FAROS at all complex airports – a regulatory
determination of ‘complex’ would be useful.
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Universal adoption of ICAO guidance on airside signage, surface markings
and lighting and an inspection regime which ensures continued integrity
should be encouraged.
Use of RUNWAY AHEAD/NO ENTRY surface markings at runway
access/egress points could be actively encouraged where appropriate.
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LEARNING LESSONS FROM
RUNWAY INCURSIONS
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Independent investigation of runway collisions and incursions which are ‘Accidents’ or
‘Serious Incidents’ under ICAO Annex 13 is only followed in just over half of ICAO
Member States and the definition of the threshold for a ‘Serious Incident’ of this type
is variably interpreted.
Runway Collision risk management therefore depends heavily on the investigation of
non fatal runway incursion events mainly through other processes.
The ICAO severity classification system for runway incursion events is (as for
AIRPROX) based on the actual outcome. It thereby implicitly links the scale of an
investigation to the actual outcome whereas the value of the lessons to be learned
may not be so linked. As an example, since severity is classified after taking
account of any avoiding action, the important distinction between such actions
which are systems-based are not distinguished from those which are partly or wholly
based on ‘providential’ human performance.
Whilst the Annex 13 process is understandably based on outcome severity, more
informed guidance on the way non-Annex 13 runway incursion events are initially
evaluated could better inform the appropriate scale of investigation and support an
improved alignment between the resource cost of that investigation and its potential
benefits. Much better dissemination of transferable lessons learned is also needed.
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THANK YOU
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