Accident and Serious Incident Reports: LOS
Accident and Serious Incident Reports: LOS
Definition
Reports relating to accidents and incidents which involved Loss of Separation.
The accident and serious incident reports are grouped together below in subcategories.
TCAS RA Mis-flown
On 23 February 2018, an Embraer 195LR and an Airbus A320 on SIDs departing Brussels lost separation after the 195 was given a radar heading to resolve a perceived third aircraft conflict which led to loss of separation between the two departing aircraft. STCA and coordinated TCAS RA activations followed but only one TCAS RA was followed and the estimated minimum separation was 400 feet vertically when 1.36 nm apart. The Investigation found that conflict followed an error by an OJTI-supervised trainee controller receiving extended revalidation training despite gaining his licence and having almost 10 years similar experience in Latvia.
On 4 June 2016, a Boeing 737-800 instructed to climb from FL340 to FL380 by the controller of one sector in Bulgarian upper airspace came into sufficiently close proximity to an Airbus A320 under the control of a different sector controller to trigger co-ordinated TCAS RAs. Separation was eventually restored after the 737 followed its RA despite the A320, which had already deviated from its clearance on the basis of a prior TCAS TA without informing ATC, ignoring their RA. The Investigation found that the root cause of the conflict had been inadequate coordination between two vertically separated ATC sectors.
On 10 June 2011 an ATC error put a German Wings A319 and a Hahn Air Raytheon 390 on conflicting tracks over Switzerland and a co-ordinated TCAS RA followed. The aircraft subsequently passed in very close proximity without either sighting the other after the Hahn Air crew, contrary to Company procedures, followed an ATC descent clearance issued during their TCAS ‘Climb’ RA rather than continuing to fly the RA. The Investigation could find no explanation for this action by the experienced crew - both Hahn Air management pilots. The recorded CPA was 0.6 nm horizontally at 50 feet vertically.
On 20 November 2011, a problem in reading the altitude labels on the ATC radar control display led to a Finnair Boeing 757 being cleared to make a descent which brought it into proximity with a Thomas Cook Boeing 757 in day VMC. Co-ordinated TCAS RAs were generated onboard both aircraft but when the Finnair aircraft failed to respond to its Climb RA and continued descent, the other aircraft, which had responded correctly to its initial RA, received a further RA to reverse their descent to a climb. The Finnair aircraft reported retaining visual contact with the other aircraft throughout.
On 7 February 2011 two Air Inuit DHC8s came into head-to-head conflict en route over the eastern shoreline of Hudson Bay in non radar Class A airspace when one of them deviated from its cleared level towards the other which had been assigned the level 1000 feet below. The subsequent investigation found that an inappropriate FD mode had been used to maintain the assigned level of the deviating aircraft and noted deficiencies at the Operator in both TCAS pilot training and aircraft defect reporting as well as a variation in altitude alerting systems fitted to aircraft in the DHC8 fleet.
Accepted ATC Clearance Not Followed
On 23 February 2018, an Embraer 195LR and an Airbus A320 on SIDs departing Brussels lost separation after the 195 was given a radar heading to resolve a perceived third aircraft conflict which led to loss of separation between the two departing aircraft. STCA and coordinated TCAS RA activations followed but only one TCAS RA was followed and the estimated minimum separation was 400 feet vertically when 1.36 nm apart. The Investigation found that conflict followed an error by an OJTI-supervised trainee controller receiving extended revalidation training despite gaining his licence and having almost 10 years similar experience in Latvia.
On 4 June 2016, a Boeing 737-800 instructed to climb from FL340 to FL380 by the controller of one sector in Bulgarian upper airspace came into sufficiently close proximity to an Airbus A320 under the control of a different sector controller to trigger co-ordinated TCAS RAs. Separation was eventually restored after the 737 followed its RA despite the A320, which had already deviated from its clearance on the basis of a prior TCAS TA without informing ATC, ignoring their RA. The Investigation found that the root cause of the conflict had been inadequate coordination between two vertically separated ATC sectors.
On 10 June 2011 an ATC error put a German Wings A319 and a Hahn Air Raytheon 390 on conflicting tracks over Switzerland and a co-ordinated TCAS RA followed. The aircraft subsequently passed in very close proximity without either sighting the other after the Hahn Air crew, contrary to Company procedures, followed an ATC descent clearance issued during their TCAS ‘Climb’ RA rather than continuing to fly the RA. The Investigation could find no explanation for this action by the experienced crew - both Hahn Air management pilots. The recorded CPA was 0.6 nm horizontally at 50 feet vertically.
On 20 November 2011, a problem in reading the altitude labels on the ATC radar control display led to a Finnair Boeing 757 being cleared to make a descent which brought it into proximity with a Thomas Cook Boeing 757 in day VMC. Co-ordinated TCAS RAs were generated onboard both aircraft but when the Finnair aircraft failed to respond to its Climb RA and continued descent, the other aircraft, which had responded correctly to its initial RA, received a further RA to reverse their descent to a climb. The Finnair aircraft reported retaining visual contact with the other aircraft throughout.
On 7 February 2011 two Air Inuit DHC8s came into head-to-head conflict en route over the eastern shoreline of Hudson Bay in non radar Class A airspace when one of them deviated from its cleared level towards the other which had been assigned the level 1000 feet below. The subsequent investigation found that an inappropriate FD mode had been used to maintain the assigned level of the deviating aircraft and noted deficiencies at the Operator in both TCAS pilot training and aircraft defect reporting as well as a variation in altitude alerting systems fitted to aircraft in the DHC8 fleet.
"See and Avoid" Ineffective
On 18 December 2020, a Bombardier Challenger descending on an ILS approach into Sion in VMC within the Sion TMA was advised of unknown VFR traffic on a potentially conflicting track and working a different frequency. Minimum separation was 100 feet vertically and just over 1 nm laterally before the Challenger response to a TCAS RA increased vertical separation despite the other traffic also initially attempting visual separation by climbing. The Class ‘D’ airspace Sion TMA was inactive and therefore downgraded to Class ’E’. The Investigation concluded that procedures which prevented activation of the TMA at short notice were outdated.
On 20 June 2010, a Boeing 737-800 being operated by New Zealand company Pacific Blue AL on a scheduled passenger flight from Auckland to Queenstown lost IFR separation assurance against a Boeing 737-800 being operated by Qantas on a scheduled passenger flight from Sydney to Queenstown whilst both aircraft were flying a go around following successive but different instrument approaches at their shared intended destination. There were no abrupt manoeuvres and none of the respectively 88 and 162 occupants of the two aircraft were injured.
On 15 October 2017, a Falcon 2000EX on base leg for an easterly ILS approach at St Gallen-Altenrhein came into close proximity with a reciprocal track glider at 5000 feet QNH in Class ‘E’ airspace in day VMC with neither aircraft seeing the other until just before their minimum separation - 0.35 nm horizontally and 131 feet vertically - occurred. The Investigation attributed the conflict to the lack of relevant traffic separation requirements in Class E airspace and to the glider not having its transponder switched on and not listening out with the relevant ATC Unit.
On 27 June 2016, an Airbus A319 narrowly avoided a mid-air collision with an AS532 Cougar helicopter whose single transponder had failed earlier whilst conducting a local pre-delivery test flight whilst both were positioning visually as cleared to land at Marseille and after the helicopter had also temporarily disappeared from primary radar. Neither aircraft crew had detected the other prior to their tracks crossing at a similar altitude. The Investigation attributed the conflict to an inappropriate ATC response to the temporary loss of radar contact with the helicopter aggravated by inaccurate position reports and non-compliance with the aerodrome circuit altitude by the helicopter crew.
On 7 July 2015, a mid-air collision occurred between an F16 and a Cessna 150 in VMC at 1,600 feet QNH in Class E airspace north of Charleston SC after neither pilot detected the conflict until it was too late to take avoiding action. Both aircraft subsequently crashed and the F16 pilot ejected. The parallel civil and military investigations conducted noted the limitations of see-and-avoid and attributed the accident to the failure of the radar controller working the F16 to provide appropriate timely resolution of the impending conflict.
Required Separation not Maintained
On 4 February 2023, a Boeing 767-300 which had initiated a night go-around in freezing fog passed within 115 feet of a Boeing 737-700 taking off from the same runway. The aircraft had been respectively cleared to land and takeoff by the same controller but on sighting the 737 on the runway ahead, the 767 crew deemed a go around was necessary to avoid a ground collision. The experienced controller’s poor judgement was attributed to a combination of expectation bias, lack of awareness of a predictable delay to the 737’s departure and absence of any training in low visibility operations.
On 29 April 2022, an Airbus A320 and a Boeing 737-800 both came into close proximity at Barcelona at night - 247 metres laterally and 44 feet vertically - after the A320 received landing clearance for runway 02 and the 737 was then given takeoff clearance on runway 06R. Both aircraft were following ATC instructions issued shortly after runway use had changed from daytime (parallel runways in use) to nightime configuration (near-intersecting runways in use). The landing clearance was issued contrary to procedures by a controller who had failed to reconfigure their position when runway use changed.
On 16 June 2017 a Bombardier DH8-400 inbound to Vienna and an Airbus A319 which had just departed the same airport lost separation in the vicinity of 7,000 feet in Class ‘C’ airspace whilst under radar control. Both aircraft responded to their TCAS RAs and minimum separation was 1.2nm laterally and 300 feet vertically - less than half the prescribed separation. The conflict followed an unintended instruction to the DHC8 to turn right rather than left onto a heading of 270°, the controller’s failure to recognise this and, finally, the inappropriate instruction to the departing A319 to resume its climb.
On 29 April 2023, a Boeing 737-800 night takeoff clearance at Sydney was delayed by unexpectedly slow landing traffic clearance and it became necessary for another Boeing 737-800 on approach to the same runway to be instructed to go around and minimum separation was reduced below safe distances both laterally and vertically. It was found that the conflict had resulted from a combination of inappropriate intervention by the Tower Supervisor and the controller’s own actions. A review of potential conflicts during mixed mode runway use at Sydney to improve resilience to inevitable pilot and controller error was initiated by ATC.
On 14 September 2022, a Boeing 787-9 inbound to Mumbai lost separation against a Boeing 787-8 also inbound to Mumbai on the same airway when it began a descent from FL410 to FL340 at night without clearance close to an air traffic control sector boundary. ATC soon observed the error but a delay in achieving contact with the 787-9 resulted in it descending to FL389 before being instructed to return to its cleared level. As it passed through FL390 descending and then again when climbing, it came within 3nm of the same-direction 787-8 which was level as cleared at FL390.
Released to Own Separation
On 23 July 2011 a Boeing 757 in Class E airspace east of Glasgow in VMC encountered a glider ahead at the same altitude and deviated right to avoid a collision. The glider, climbing in a thermal, had not seen the 757 until it passed during avoiding action. The closest proximity was estimated as 100 metres at the same level as the glider passed to the left of the 757 in the opposite direction. Since the circumstances were considered to have demonstrated a safety critical risk by the UK CAA, an interim airspace reclassification Class D was implemented
On 20 June 2010, a Boeing 737-800 being operated by New Zealand company Pacific Blue AL on a scheduled passenger flight from Auckland to Queenstown lost IFR separation assurance against a Boeing 737-800 being operated by Qantas on a scheduled passenger flight from Sydney to Queenstown whilst both aircraft were flying a go around following successive but different instrument approaches at their shared intended destination. There were no abrupt manoeuvres and none of the respectively 88 and 162 occupants of the two aircraft were injured.
On 27 June 2016, an Airbus A319 narrowly avoided a mid-air collision with an AS532 Cougar helicopter whose single transponder had failed earlier whilst conducting a local pre-delivery test flight whilst both were positioning visually as cleared to land at Marseille and after the helicopter had also temporarily disappeared from primary radar. Neither aircraft crew had detected the other prior to their tracks crossing at a similar altitude. The Investigation attributed the conflict to an inappropriate ATC response to the temporary loss of radar contact with the helicopter aggravated by inaccurate position reports and non-compliance with the aerodrome circuit altitude by the helicopter crew.
On 2 June 2012, a Dornier 328 and a commercially-operated Robinson R44 helicopter came into close proximity within the airport perimeter whilst both were departing from Bern in VMC as cleared. The Investigation attributed the conflict to inappropriate issue of clearances by the controller in a context of an absence of both a defined final approach and take off area and fixed departure routes to the three designated departure points.
On 18 July 2013, an Airbus A319 level at 2000 feet QNH in Class G airspace and being radar vectored towards an ILS approach at Southend in day VMC had a sudden but brief base leg encounter with a paramotor which was not visible on radar and was seen too late for avoiding action to be practicable, before passing within an estimated 50 metres of the A319. The paramotor pilot could not subsequently be traced. The Investigation made a safety recommendation to the UK CAA to review the regulation and licensing of paramotor pilots.
Level Bust
On 21 March 2022, an Airbus A320 level at FL 360 lost separation with another Airbus A320, which continued its descent beyond its cleared level. A predictive conflict alert prompted the controller to issue multiple calls confirming the clearance limit but with no response. When both aircraft tracks crossed at FL 360, lateral separation was reduced to 3.8 nm. It was concluded that the immediate cause of the conflict was the failure of the descending aircraft to respond to ATC alerting calls, but that its origin was an undetected incorrect readback of the descent clearance.
On 29 April 2021, the crew of an Airbus A319 that had just taken off from runway 18 at St Petersburg saw a Cessna M337 about to cross their intended track close to the same height, and levelled off to ensure they passed beneath it, achieving a 100-foot separation. The conflict was attributed to the controller’s general loss of situational awareness and his failure to properly scan airspace in the vicinity of the airport. The Cessna 337 pilot’s failure to fly at the standard circuit height or track downwind at the standard distance from the runway was deemed contributory.
On 12 January 2022, an Embraer 170 and a Cessna 525 crossed tracks without the prescribed minimum separation, with neither ATC nor the Embraer crew being aware. Although ATC had issued acknowledged clearances to keep the Embraer 1,000 feet above the Cessna, it actually passed beneath it, violating minimum lateral separation. The underlying cause of the event was found to be an unrectified recurrent intermittent fault in one of the Cessna’s air data systems. Poor Cessna crew/controller communication during the event, systemically poor safety culture at its operator, and shortcomings in the Textron Aircraft Maintenance Manual were considered contributory.
On 6 January 2018, a Boeing 737-900 and an Airbus A320 both inbound to Surabaya with similar estimated arrival times were cleared to hold at the same waypoint at FL100 and FL110 respectively but separation was lost when the A320 continued below FL110. Proximity was limited to 1.9nm laterally and 600 feet vertically following correct responses to coordinated TCAS RAs. The Investigation found that all clearances / readbacks had been correct but that the A320 crew had set FL100 instead of their FL110 clearance and attributed this to diminished performance due to the passive distraction of one of the pilots.
On 29 February 2020, an Airbus A320 inbound to Delhi lost separation against an outbound A320 from Delhi on a reciprocal track and the conflict was resolved by TCAS RA activation. The Investigation found that the inbound aircraft had correctly read back its descent clearance but then set a different selected altitude. Air Traffic Control had not reacted to the annunciated conflict alert and was unable to resolve it when the corresponding warning followed and it was noted that convective weather meant most aircraft were requesting deviations from their standard routes which was leading to abnormally complex workload.
Lateral Navigation Error
On 13 July 2022, an Airbus A330-300 inbound to Madrid and descending on the 32L ILS and a Cessna Citation 550 which had just departed from Torrejón Air Base lost separation. The aircraft came within 400 feet vertically and 0.6nm horizontally after the Citation failed to follow its assigned and acknowledged departure clearance. A TCAS RA "DON’T CLIMB" message was annunciated on the A330 as the opposite-direction Citation, which the A330 crew subsequently reported having had briefly in sight, passed just above it. Detection of the conflict risk to ILS traffic inbound to Madrid was delayed by sub-optimal civil/military ATC coordination.
On 29 November 2017, a Boeing 737-900 on an ILS approach at Atlanta became unstable after the autothrottle and autopilot were both disconnected and was erroneously aligned with an occupied taxiway parallel to the intended landing runway. A go-around was not commenced until the aircraft was 50 feet above the ground after which it passed low over another aircraft on the taxiway. The Investigation found that the Captain had not called for a go around until well below the Decision Altitude and had then failed to promptly take control when the First Officer was slow to begin climbing the aircraft.
On 11 May 2018, a Bombardier CRJ1000 climbing on departure from Tambolaka and an ATR72-500 descending inbound there lost safe separation when during opposite turns in visual flight in uncontrolled airspace. Prompt response to both coordinated TCAS RAs resolved the conflict. The Investigation found the departing flight Captain mixed up left and right downwind circuit joining by the ATR 72 and that his inexperienced First Officer had not picked this up. It also noted that this Captain may not have been fit for duty and that all parties may have failed to fully recognise the limitations of ANSP ‘information’ service.
On 21 January 2011, a Belarusian Bombardier CRJ200 failed to fly the prescribed missed approach procedure at night in IMC and when ATC observed a developing conflict with another aircraft which had just departed another runway with a conflicting clearance, both aircraft were given heading instructions to mitigate the proximity risk. The resulting CPA was 1.8nm at an altitude of 1600 feet. The subsequent investigation attributed the pilot error to a change of aircraft control in the flare when it became apparent that a safe landing was not assured.
On 27 June 2016, an Airbus A319 narrowly avoided a mid-air collision with an AS532 Cougar helicopter whose single transponder had failed earlier whilst conducting a local pre-delivery test flight whilst both were positioning visually as cleared to land at Marseille and after the helicopter had also temporarily disappeared from primary radar. Neither aircraft crew had detected the other prior to their tracks crossing at a similar altitude. The Investigation attributed the conflict to an inappropriate ATC response to the temporary loss of radar contact with the helicopter aggravated by inaccurate position reports and non-compliance with the aerodrome circuit altitude by the helicopter crew.
ATC Error
On 29 April 2022, an Airbus A320 and a Boeing 737-800 both came into close proximity at Barcelona at night - 247 metres laterally and 44 feet vertically - after the A320 received landing clearance for runway 02 and the 737 was then given takeoff clearance on runway 06R. Both aircraft were following ATC instructions issued shortly after runway use had changed from daytime (parallel runways in use) to nightime configuration (near-intersecting runways in use). The landing clearance was issued contrary to procedures by a controller who had failed to reconfigure their position when runway use changed.
On 16 June 2017 a Bombardier DH8-400 inbound to Vienna and an Airbus A319 which had just departed the same airport lost separation in the vicinity of 7,000 feet in Class ‘C’ airspace whilst under radar control. Both aircraft responded to their TCAS RAs and minimum separation was 1.2nm laterally and 300 feet vertically - less than half the prescribed separation. The conflict followed an unintended instruction to the DHC8 to turn right rather than left onto a heading of 270°, the controller’s failure to recognise this and, finally, the inappropriate instruction to the departing A319 to resume its climb.
On 29 April 2023, a Boeing 737-800 night takeoff clearance at Sydney was delayed by unexpectedly slow landing traffic clearance and it became necessary for another Boeing 737-800 on approach to the same runway to be instructed to go around and minimum separation was reduced below safe distances both laterally and vertically. It was found that the conflict had resulted from a combination of inappropriate intervention by the Tower Supervisor and the controller’s own actions. A review of potential conflicts during mixed mode runway use at Sydney to improve resilience to inevitable pilot and controller error was initiated by ATC.
On 28 September 2022, a Boeing 787-9 and an Airbus A330-200 were successively cleared for takeoff from Sydney having been instructed to follow the same SID and climb to the same level - FL280. The A330 climbed faster than the controller anticipated and turned towards the next waypoint inside the preceding aircraft, resulting in a loss of separation. The Investigation found that the SID concerned did not provide separation assurance to aircraft with different performance characteristics because aircraft had to satisfy two separate conditions prior to turning which meant the turning point was not a fixed position.
On 17 January 2018, two Airbus A320s both inbound to Surabaya at night were vectored to the same waypoint to hold, one at FL210 and the other at FL200 but the one initially given FL210 was then re-cleared to also descend to FL200. The two aircraft subsequently received and followed coordinated TCAS RAs which restored prescribed separation. The Investigation found that before the conflict, the experienced controller involved had made several transmissions to aircraft other than the intended ones and noted that the usually-available ATC conflict alerting system had been temporarily out of service without any consequent mitigations in place.
Near Miss
On 29 April 2022, an Airbus A320 and a Boeing 737-800 both came into close proximity at Barcelona at night - 247 metres laterally and 44 feet vertically - after the A320 received landing clearance for runway 02 and the 737 was then given takeoff clearance on runway 06R. Both aircraft were following ATC instructions issued shortly after runway use had changed from daytime (parallel runways in use) to nightime configuration (near-intersecting runways in use). The landing clearance was issued contrary to procedures by a controller who had failed to reconfigure their position when runway use changed.
On 28 May 2022, the crew of a Boeing 737-800 which had just taken off from Palma in good daylight visibility observed a light aircraft approaching from the right at high speed on a collision course and immediately initiated evasive action, achieving a minimum separation subsequently found to have been 116 feet vertically and 1,200 metres laterally and passing behind it. ATC radar showed that the other aircraft had not taken any action and it was found to have been operating on a VFR flight plan in controlled airspace without complying with the requirements for such access or listening out.
On 18 December 2020, a Bombardier Challenger descending on an ILS approach into Sion in VMC within the Sion TMA was advised of unknown VFR traffic on a potentially conflicting track and working a different frequency. Minimum separation was 100 feet vertically and just over 1 nm laterally before the Challenger response to a TCAS RA increased vertical separation despite the other traffic also initially attempting visual separation by climbing. The Class ‘D’ airspace Sion TMA was inactive and therefore downgraded to Class ’E’. The Investigation concluded that procedures which prevented activation of the TMA at short notice were outdated.
On 29 April 2021, the crew of an Airbus A319 that had just taken off from runway 18 at St Petersburg saw a Cessna M337 about to cross their intended track close to the same height, and levelled off to ensure they passed beneath it, achieving a 100-foot separation. The conflict was attributed to the controller’s general loss of situational awareness and his failure to properly scan airspace in the vicinity of the airport. The Cessna 337 pilot’s failure to fly at the standard circuit height or track downwind at the standard distance from the runway was deemed contributory.
On 13 October 2019, an Airbus A320neo inbound to Zurich had been cleared to the lowest available Class ‘C’ airspace level when a light aircraft crossing its intended track below in uncontrolled airspace began to climb into the same Class C airspace without clearance. An ATC Conflict Alert was activated and the controller put the A320 on an avoidance radar heading and safe separation was thereby achieved. The reason for the incursion was not determined but the event was considered yet another example of yet-to-be-addressed airspace infringement risk and a corresponding safety recommendation was made to the State Safety Regulator.
Lateral Offset in Use
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Mid-Air Collision
On 12 November 1996, an Ilyushin IL76TD and an opposite direction Boeing 747-100 collided head on at the same level in controlled airspace resulting in the destruction of both aircraft and the loss of 349 lives. The Investigation concluded that the IL76 had descended one thousand feet below its cleared level after its crew had interpreted ATC advice of opposite direction traffic one thousand feet below as the reason to remain at FL150 as re-clearance to descend to this lower level. Fifteen Safety Recommendations relating to English language proficiency, crew resource management, collision avoidance systems and ATC procedures were made.
On 1 December 2014, a night mid-air collision occurred in uncontrolled airspace between a Lockheed C130H Hercules and an Alenia C27J Spartan conducting VFR training flights and on almost reciprocal tracks at the same indicated altitude after neither crew had detected the proximity risk. Substantial damage was caused but both aircraft were successfully recovered and there were no injuries. The Investigation attributed the collision to a lack of visual scan by both crews, over reliance on TCAS and complacency despite the inherent risk associated with night, low-level, VFR operations using the Night Vision Goggles worn by both crews.
On 7 July 2015, a mid-air collision occurred between an F16 and a Cessna 150 in VMC at 1,600 feet QNH in Class E airspace north of Charleston SC after neither pilot detected the conflict until it was too late to take avoiding action. Both aircraft subsequently crashed and the F16 pilot ejected. The parallel civil and military investigations conducted noted the limitations of see-and-avoid and attributed the accident to the failure of the radar controller working the F16 to provide appropriate timely resolution of the impending conflict.
On 5 September 2015, a Boeing 737-800 cruising as cleared at FL350 on an ATS route in daylight collided with an opposite direction HS 125-700 which had been assigned and acknowledged altitude of FL340. The 737 continued to destination with winglet damage apparently causing no control impediment but radio contact with the HS 125 was lost and it was subsequently radar-tracked maintaining FL350 and continuing westwards past its destination Dakar for almost an hour before making an uncontrolled descent into the sea. The Investigation found that the HS125 had a recent history of un-rectified altimetry problems which prevented TCAS activation.
On 28 August 2006, a Hawker 800 collided with a glider at 16,000 feet in Class 'E' airspace. The glider became uncontrollable and its pilot evacuated by parachute. The Hawker was structurally damaged and one engine stopped but it was recovered to a nearby airport. The Investigation noted that the collision had occurred in an area well known for glider activity in which transport aircraft frequently avoided glider collisions using ATC traffic information or by following TCAS RAs. The glider was being flown by a visitor to the area with its transponder intentionally switched off to conserve battery power.
Uncommanded AP disconnect
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Military Aircraft Involved
On 13 July 2022, an Airbus A330-300 inbound to Madrid and descending on the 32L ILS and a Cessna Citation 550 which had just departed from Torrejón Air Base lost separation. The aircraft came within 400 feet vertically and 0.6nm horizontally after the Citation failed to follow its assigned and acknowledged departure clearance. A TCAS RA "DON’T CLIMB" message was annunciated on the A330 as the opposite-direction Citation, which the A330 crew subsequently reported having had briefly in sight, passed just above it. Detection of the conflict risk to ILS traffic inbound to Madrid was delayed by sub-optimal civil/military ATC coordination.
On 31 December 2011 a USAF C12 Beech King Air descended 700 feet below the cleared outbound altitude on a procedural non precision approach to Stornoway in uncontrolled airspace in IMC and also failed to fly the procedure correctly. As a result it came into conflict with a Saab 340 inbound on the same procedure. The Investigation found that the C12 crew had interpreted the QNH given by ATC as 990 hPa as 29.90 inches, the subscale setting units used in the USA. The Saab 340 pilot saw the opposite direction traffic on TCAS and descended early to increase separation.
On 1 December 2014, a night mid-air collision occurred in uncontrolled airspace between a Lockheed C130H Hercules and an Alenia C27J Spartan conducting VFR training flights and on almost reciprocal tracks at the same indicated altitude after neither crew had detected the proximity risk. Substantial damage was caused but both aircraft were successfully recovered and there were no injuries. The Investigation attributed the collision to a lack of visual scan by both crews, over reliance on TCAS and complacency despite the inherent risk associated with night, low-level, VFR operations using the Night Vision Goggles worn by both crews.
On 7 July 2015, a mid-air collision occurred between an F16 and a Cessna 150 in VMC at 1,600 feet QNH in Class E airspace north of Charleston SC after neither pilot detected the conflict until it was too late to take avoiding action. Both aircraft subsequently crashed and the F16 pilot ejected. The parallel civil and military investigations conducted noted the limitations of see-and-avoid and attributed the accident to the failure of the radar controller working the F16 to provide appropriate timely resolution of the impending conflict.
On 23 June 2014, a civil-operated Learjet 35 taking part in a German Air Force interception training exercise collided with the intercepting fighter aircraft as it began a follow-me manoeuvre. It became uncontrollable as a result of the damage sustained in the collision and crashed into terrain, killing both pilots. The Investigation found that whilst preparation for the exercise by all involved had been in compliance with requirements, these requirements had been inadequate, especially in respect of co-ordination between all the pilots involved, with both the civil and military safety regulatory authorities failing to detect and act on this situation.
Apparent de-selection of transponder
On 29 September 2006, a Boeing 737-800 level at FL370 collided with an opposite direction Embraer Legacy at the same level. Control of the 737 was lost and it crashed, killing all 154 occupants. The Legacy's crew kept control and successfully diverted to the nearest suitable airport. The Investigation found that ATC had not instructed the Legacy to descend to FL360 when the flight plan indicated this and soon afterwards, its crew had inadvertently switched off their transponder. After the consequent disappearance of altitude from all radar displays, ATC assumed but did not confirm the aircraft had descended.
On 27 January 2005, two USAF-operated McDonnell Douglas F15E fighter aircraft, both continued to climb and both passed through the level of an Embraer 145 being operated by British Airways Regional on a scheduled passenger flight from Birmingham to Hannover, one seen at an estimated range of 100 feet.
Transponder non selection
On 28 November 2020, in uncontrolled Class ‘G’ airspace, an Airbus A320 inbound to and in contact with Ballina and an en-route light aircraft tracking abeam Ballina both listening out on a shared Common Traffic Advisory Frequency (CTAF) did not recollect hearing potentially useful CTAF calls and converged on intersecting tracks with the light aircraft TCAS only selected to Mode ‘A’. The A320 received a TCAS TA but neither aircraft visually acquired the other until the minimum separation of 600 feet with no lateral separation occurred. Changes to the air traffic advisory radio service in the area were subsequently made.
On 11 March 2011, a Delta AL Boeing 757 departed Atlanta GA with no secondary radar indication visible to ATC and also failed to make contact with departure radar after accepting the frequency transfer instruction. During the eight minutes out of radio contact, it successively lost separation against two light aircraft and another passenger aircraft as it followed the cleared RNAV departure routing for eight minutes until the crew queried further climb on the TWR frequency and were invited to select their transponder on and contact the correct frequency.
On 15 October 2017, a Falcon 2000EX on base leg for an easterly ILS approach at St Gallen-Altenrhein came into close proximity with a reciprocal track glider at 5000 feet QNH in Class ‘E’ airspace in day VMC with neither aircraft seeing the other until just before their minimum separation - 0.35 nm horizontally and 131 feet vertically - occurred. The Investigation attributed the conflict to the lack of relevant traffic separation requirements in Class E airspace and to the glider not having its transponder switched on and not listening out with the relevant ATC Unit.
On 30 June 2015 the crew of an en route Embraer 170 failed to notice that their transponder had reverted to Standby and the ATC response, which involved cross border coordination, was so slow that the aircraft was not informed of the loss of its transponder signal for over 30 minutes by which time it had already passed within 0.9nm of an unseen Dassault Falcon 900 at the same level. The Investigation found that the Embraer crew had failed to follow appropriate procedures and that the subsequent collision risk had been significantly worsened by a muddled and inappropriate ATC response.
On 28 August 2006, a Hawker 800 collided with a glider at 16,000 feet in Class 'E' airspace. The glider became uncontrollable and its pilot evacuated by parachute. The Hawker was structurally damaged and one engine stopped but it was recovered to a nearby airport. The Investigation noted that the collision had occurred in an area well known for glider activity in which transport aircraft frequently avoided glider collisions using ATC traffic information or by following TCAS RAs. The glider was being flown by a visitor to the area with its transponder intentionally switched off to conserve battery power.
Go Around Separation
On 29 April 2023, a Boeing 737-800 night takeoff clearance at Sydney was delayed by unexpectedly slow landing traffic clearance and it became necessary for another Boeing 737-800 on approach to the same runway to be instructed to go around and minimum separation was reduced below safe distances both laterally and vertically. It was found that the conflict had resulted from a combination of inappropriate intervention by the Tower Supervisor and the controller’s own actions. A review of potential conflicts during mixed mode runway use at Sydney to improve resilience to inevitable pilot and controller error was initiated by ATC.
On 21 October 2020, an Embraer ERJ170 on short final at Paris CDG responded to a windshear warning by breaking off the approach and climbing. The warning soon stopped but the aircraft drifted sideways in the strong crosswind towards the adjacent parallel runway from which an Airbus A320 had just taken off. A Short-Term Conflict Alert on the controller's display was accompanied by a TCAS RA event triggered for both aircraft. The Investigation was concerned about the implications of failure to climb straight ahead from parallel runways during unexpected go-arounds. Safety Recommendations were made on risk management of parallel runway operations by both pilots and safety regulators.
On 4 February 2020, an Airbus A350-900 initiated a go around from its destination approach at 1,400 feet aal following a predictive windshear alert unsupported by the prevailing environmental conditions but the First Officer mishandled it and the stop altitude was first exceeded and then flown though again in a descent before control as instructed was finally regained four minutes later. Conflict with another aircraft occurred during this period. The Investigation concluded the underlying cause of the upset was a lack of awareness of autopilot status by the First Officer followed by a significant delay before the Captain took over control.
On 12 April 2019, a Boeing 717-200 commenced a go around at Strasbourg because the runway ahead was occupied by a departing Bombardier CRJ700 which subsequently, despite co-ordinated TCAS RAs, then came to within 50 feet vertically when only 740 metres apart laterally as the CRJ, whose crew did not see the 717, passed right to left in front of it. The Investigation attributed the conflict primarily to a series of flawed judgements by the TWR controller involved whilst also noting one absent and one inappropriate ATC procedure which respectively may have provided a context for the resultant risk.
On 29 March 2018, a Boeing 737-700 commenced a late go-around from landing at Amsterdam on a runway with an extended centreline which passed over another runway from which a Boeing 737-800 had already been cleared for takeoff. An attempt by the controller responsible for both aircraft to stop the departing aircraft failed because the wrong callsign was used, so low level divergent turns were given to both aircraft and 0.5nm lateral and 300 feet vertical separation was achieved. The Investigation concluded that the ATC procedure involved was potentially hazardous and made a safety recommendation that it should be withdrawn.
UAV Involved
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Unregulated Manned Flight Involved
On 18 July 2013, an Airbus A319 level at 2000 feet QNH in Class G airspace and being radar vectored towards an ILS approach at Southend in day VMC had a sudden but brief base leg encounter with a paramotor which was not visible on radar and was seen too late for avoiding action to be practicable, before passing within an estimated 50 metres of the A319. The paramotor pilot could not subsequently be traced. The Investigation made a safety recommendation to the UK CAA to review the regulation and licensing of paramotor pilots.
Procedural Control
On 12 May 2019, a Boeing 737-800 making its second procedural ILS approach to runway 25 at Reus came into conflict with an opposite direction light aircraft as the latter approached one of the designated VFR entry points having been instructed to remain well above the altitude which normally ensures separation of IFR and VFR traffic. The collision risk was resolved by TCAS RA promptly followed by the 737. The Investigation concluded that limiting the TWR radar display to the ATZ for controller training purposes had resulted in neither the trainee controller nor their supervisor being aware of the risk.
On 5 September 2015, a Boeing 737-800 cruising as cleared at FL350 on an ATS route in daylight collided with an opposite direction HS 125-700 which had been assigned and acknowledged altitude of FL340. The 737 continued to destination with winglet damage apparently causing no control impediment but radio contact with the HS 125 was lost and it was subsequently radar-tracked maintaining FL350 and continuing westwards past its destination Dakar for almost an hour before making an uncontrolled descent into the sea. The Investigation found that the HS125 had a recent history of un-rectified altimetry problems which prevented TCAS activation.
On 31 March 2012, after the implementation of contingency ATC procedures for a period of 5 hours due to controller shortage, two Garuda A330 aircraft which had been transiting an associated Temporary Restricted Area (TRA) prior to re-entering controlled airspace were separately involved in losses of separation assurance, one when unexpectedly entering adjacent airspace from the TRA, the other when the TRA ceased and controlled airspace was restored. The Investigation did not find that any actual loss of separation had occurred but identified four Safety Issues in relation to the inadequate handling of the TRA activation by ANSP Airservices Australia.
On 2 August 2007, a Fokker F50 on an ILS approach to Maastricht in IMC came into close proximity inside the CTZ with an unseen light aircraft which had failed to comply with its Special VFR transit clearance. The Investigation found that the transiting aircraft had come within 0.14nm / 260 metres of the opposite direction F50 at a similar altitude without either aircraft having sight of the other, and that the Harvard had been wrongly assumed by ATC to be a helicopter after an initial lack of call sign prefix clarity on first contact had not been positively resolved.
ATC control using ADS-B
On 4 February 2023, a Boeing 767-300 which had initiated a night go-around in freezing fog passed within 115 feet of a Boeing 737-700 taking off from the same runway. The aircraft had been respectively cleared to land and takeoff by the same controller but on sighting the 737 on the runway ahead, the 767 crew deemed a go around was necessary to avoid a ground collision. The experienced controller’s poor judgement was attributed to a combination of expectation bias, lack of awareness of a predictable delay to the 737’s departure and absence of any training in low visibility operations.
ATC control supported by ADS-C
On 14 September 2022, a Boeing 787-9 inbound to Mumbai lost separation against a Boeing 787-8 also inbound to Mumbai on the same airway when it began a descent from FL410 to FL340 at night without clearance close to an air traffic control sector boundary. ATC soon observed the error but a delay in achieving contact with the 787-9 resulted in it descending to FL389 before being instructed to return to its cleared level. As it passed through FL390 descending and then again when climbing, it came within 3nm of the same-direction 787-8 which was level as cleared at FL390.
Uncontrolled Airspace
On 28 April 2018, a Dassault Falcon F900B came into close proximity with a Beech B36T Bonanza at the uncontrolled VFR-only aerodrome at Bremgarten during its tailwind approach to runway 23 made without contacting the designated Flight Information frequency as the other aircraft was on approach to runway-in-use 05 and in contact with Flight Information. The Beech pilot took avoiding action by turning north and climbing in order to avoid a collision. The Falcon 900 crew had not prepared for the approach which was then unstabilised with late gear extension and multiple EGPWS ‘SINK RATE’ warnings annunciated.
On 28 November 2020, in uncontrolled Class ‘G’ airspace, an Airbus A320 inbound to and in contact with Ballina and an en-route light aircraft tracking abeam Ballina both listening out on a shared Common Traffic Advisory Frequency (CTAF) did not recollect hearing potentially useful CTAF calls and converged on intersecting tracks with the light aircraft TCAS only selected to Mode ‘A’. The A320 received a TCAS TA but neither aircraft visually acquired the other until the minimum separation of 600 feet with no lateral separation occurred. Changes to the air traffic advisory radio service in the area were subsequently made.
On 11 May 2018, a Bombardier CRJ1000 climbing on departure from Tambolaka and an ATR72-500 descending inbound there lost safe separation when during opposite turns in visual flight in uncontrolled airspace. Prompt response to both coordinated TCAS RAs resolved the conflict. The Investigation found the departing flight Captain mixed up left and right downwind circuit joining by the ATR 72 and that his inexperienced First Officer had not picked this up. It also noted that this Captain may not have been fit for duty and that all parties may have failed to fully recognise the limitations of ANSP ‘information’ service.
On 1 December 2014, a night mid-air collision occurred in uncontrolled airspace between a Lockheed C130H Hercules and an Alenia C27J Spartan conducting VFR training flights and on almost reciprocal tracks at the same indicated altitude after neither crew had detected the proximity risk. Substantial damage was caused but both aircraft were successfully recovered and there were no injuries. The Investigation attributed the collision to a lack of visual scan by both crews, over reliance on TCAS and complacency despite the inherent risk associated with night, low-level, VFR operations using the Night Vision Goggles worn by both crews.
On 7 March 2017, an en-route Cessna Citation and a manoeuvring Ikarus C42 light aircraft approaching almost head-on at speeds of 240 knots and 55 knots respectively almost collided at an altitude of 3,500 feet in VMC outside controlled airspace. The Investigation found that only the C42 pilot had seen a conflicting aircraft and that they had then taken avoiding action which had mitigated the high risk of collision. The closest point of approach was recorded on radar as less than 100 feet vertically and less than 185 metres laterally. The near miss was categorised as an ICAO 'A' event.
TCAS RA Reversal
On 29 June 2010, an Easyjet Switzerland Airbus A319 inbound to Basle-Mulhouse and an Air France Airbus A319 outbound from Basle-Mulhouse lost separation after an error made by a trainee APP controller under OJTI supervision during procedural service. The outcome was made worse by the excessive rate of climb of the Air France aircraft approaching its cleared level and both an inappropriate response to an initial preventive TCAS RA and a change of track during the ensuing short sequence of RAs by the Training Captain in command of and flying the Easyjet aircraft attributed by him to his situational ‘anxiety’.
On 30 October 2014, a descending Airbus A320 came close to a Boeing 737-800 at around FL 220 after the A320 crew significantly exceeded a previously-instructed 2,000 fpm maximum rate of descent assuming it no longer applied when not reiterated during re-clearance to a lower altitude. Their response to a TCAS RA requiring descent at not above 1,000 fpm was to further increase it from 3,200 fpm. Lack of notification delayed the start of an independent Investigation but it eventually found that although the A320 TCAS equipment had been serviceable, its crew denied failing to correctly follow their initial RA.
On 2 September 2013, a B737 crew were not instructed to go around from their approach by ATC as it became increasingly obvious that an A320 departing the same runway would not be airborne in time for a landing clearance to be issued. They initiated a go around over the threshold and then twice came into conflict with the A320 as both climbed on similar tracks without ATC de-confliction, initially below the height where TCAS RAs are functional. Investigation attributed the conflict to ATC but the failure to effectively deal with the consequences jointly to ATC and both aircraft crews.
On 31 July 2015 a Saudi-operated Embraer Phenom on a private flight continued an unstabilised day visual approach to Blackbushe in benign weather conditions. The aircraft touched down with excess speed with almost 70% of the available landing distance behind the aircraft. It overran and was destroyed by impact damage and fire and all occupants died. The Investigation concluded that the combination of factors which created a very high workload for the pilot may have saturated his mental capacity, impeding his ability to handle new information and adapt his mental model leading to his continuation of a highly unstable approach.
On 13 October 2009, an Avro RJ100 being operated by Malmo Aviation on a scheduled passenger flight from Stockholm Bromma to Malmo in day VMC came into proximity with a unseen light aircraft crossing below which activated a TCAS RA which was followed. The flight crew were unaware that they were outside controlled airspace at the time. No abrupt manoeuvring occurred and none of the 85 occupants were injured.
VFR Aircraft Involved
On 28 May 2022, the crew of a Boeing 737-800 which had just taken off from Palma in good daylight visibility observed a light aircraft approaching from the right at high speed on a collision course and immediately initiated evasive action, achieving a minimum separation subsequently found to have been 116 feet vertically and 1,200 metres laterally and passing behind it. ATC radar showed that the other aircraft had not taken any action and it was found to have been operating on a VFR flight plan in controlled airspace without complying with the requirements for such access or listening out.
On 18 December 2020, a Bombardier Challenger descending on an ILS approach into Sion in VMC within the Sion TMA was advised of unknown VFR traffic on a potentially conflicting track and working a different frequency. Minimum separation was 100 feet vertically and just over 1 nm laterally before the Challenger response to a TCAS RA increased vertical separation despite the other traffic also initially attempting visual separation by climbing. The Class ‘D’ airspace Sion TMA was inactive and therefore downgraded to Class ’E’. The Investigation concluded that procedures which prevented activation of the TMA at short notice were outdated.
On 29 April 2021, the crew of an Airbus A319 that had just taken off from runway 18 at St Petersburg saw a Cessna M337 about to cross their intended track close to the same height, and levelled off to ensure they passed beneath it, achieving a 100-foot separation. The conflict was attributed to the controller’s general loss of situational awareness and his failure to properly scan airspace in the vicinity of the airport. The Cessna 337 pilot’s failure to fly at the standard circuit height or track downwind at the standard distance from the runway was deemed contributory.
On 13 October 2019, an Airbus A320neo inbound to Zurich had been cleared to the lowest available Class ‘C’ airspace level when a light aircraft crossing its intended track below in uncontrolled airspace began to climb into the same Class C airspace without clearance. An ATC Conflict Alert was activated and the controller put the A320 on an avoidance radar heading and safe separation was thereby achieved. The reason for the incursion was not determined but the event was considered yet another example of yet-to-be-addressed airspace infringement risk and a corresponding safety recommendation was made to the State Safety Regulator.
On 26 June 2017, an Airbus A319 which had just taken off from Stuttgart came into conflict in Class ‘D’ airspace with a VFR light aircraft crossing its track and when, at 1,200 feet agl, the TCAS RA to descend which resulted was followed, an EGPWS Mode 3 Alert was generated. Clear of Conflict was annunciated after 10 seconds and climb resumed. The Investigation concluded that the light aircraft pilot had failed to follow the clearance which had been accepted and had caused the flight path conflict which was resolved by the response of the A319 to the TCAS RA.
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