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  • A321 / B738, en-route, south eastern Bulgaria, 2016 (Synopsis: On 8 September 2016, an Airbus A321 en route in Bulgarian airspace at FL 350 was given and acknowledged a descent but then climbed and came within 1.2nm of a descending Boeing 737. The Investigation found that the inexperienced A321 First Officer had been temporarily alone when the instruction was given and had insufficient understanding of how to control the aircraft. It was also found that despite an STCA activation of the collision risk, the controller, influenced by a Mode ‘S’ downlink of the correctly-set A321 cleared altitude, had then added to the risk by instructing the 737 to descend.)
  • C525 / B773, vicinity London City UK, 2009 (Synopsis: On 27 July 2009, a Cessna 525 departing from London City failed to comply with the initial 3000 feet QNH SID Stop altitude and at 4000 feet QNH in day VMC came into close proximity on an almost reciprocal heading with a Boeing 777-300ER. The 777, on which line training was being conducted, failed to follow any of the three TCAS RAs generated. Actual minimum separation was approximately 0.5nm laterally and estimated at between 100 feet and 200 feet vertically. It was noted that the Cessna had been given a stepped climb SID.)
  • A320, en-route, north of Swansea UK, 2012 (Synopsis: On 7 September 2012, the crew of an Aer Lingus Airbus A320-200 mis-set their descent clearance. When discovering this as the actual cleared level was being approached, the AP was disconnected and the unduly abrupt control input made led to an injury to one of the cabin crew. The original error was attributed to ineffective flight deck monitoring and the inappropriate corrective control input to insufficient appreciation of the aerodynamic handling aspects of flight at high altitude. A Safety Recommendation to the Operator to review relevant aspects of its flight crew training was made.)
  • GLF5 / A319, south-eastern France, 2004 (Synopsis: On 16 September 2004, a loss of separation occurred over Geneva between Air France A319 and a Gulfstream 5 which commenced descent without clearance by ATC and with coordinated TCAS RAs not followed by either aircraft.)
  • F15 / E145, en-route, Bedford UK, 2005 (Synopsis: 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.)
  • DH8D, vicinity Edinburgh UK, 2008 (Synopsis: On 23 December 2008, a DHC8-400 being operated by Flybe on a scheduled passenger flight from Southampton to Edinburgh continued descent below its cleared altitude of 2100ft in day VMC prior to and then whilst tracking the ILS LLZ for Runway 23 at destination. It remained below the ILS GS until the ATC GND Controller, who had no formal responsibility for this phase of flight but was positioned alongside the TWR Controller, observed that aircraft had descended to within 800 ft of local terrain approximately 5 nm from the runway threshold. The flight crew appeared unaware of this when making a ‘Finals’ call to TWR at 5.5 nm and so the Controller queried the descent. The aircraft was then levelled to achieve 600ft agl at 4nm from the threshold and an uneventful landing subsequently followed.)
  • A319/B733, en-route, near Moutiers France, 2010 (Synopsis: On 8 July 2010 an Easyjet Airbus A319 on which line training was being conducted mis-set a descent level despite correctly reading it back and, after subsequently failing to notice an ATC re-iteration of the same cleared level, continued descent to 1000 feet below it in day VMC and into conflict with crossing traffic at that level, a Boeing 737. The 737 received and actioned a TCAS RA ‘CLIMB’ and the A319, which received only a TCAS TA, was given an emergency turn by ATC. The recorded CPA was 2.2 nm and 125 feet.)
  • H25B, vicinity Kerry Ireland, 2015 (Synopsis: On 16 June 2015, the crew of a US-operated HS125 on a commercial air transport flight failed to continue climbing as cleared to FL200 after take off from Kerry for a transatlantic flight and instead levelled at 2000 feet on track towards higher terrain. Prompt ATC recognition of the situation and intervention to direct an immediate climb resolved the imminent CFIT risk. The Investigation found that the two pilots involved had, despite correct readback, interpreted their clearance to flight level two hundred as being to two thousand feet and then failed to seek clarification from ATC when they became confused.)
  • BE20/SF34, vicinity Stornoway UK, 2011 (Synopsis: 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.)
  • A310, vicinity Birmingham UK, 2006 (Synopsis: On 24 November 2006, an A310 descended significantly below cleared altitude during a radar vectored approach positioning, as a result of the flight crew's failure to set the QNH, which was unusually low.)
  • A319 / A321, en-route, west north west of Geneva, Switzerland 2011 (Synopsis: On 6 August 2011 an Easyjet Airbus A319 on which First Officer Line Training was in progress exceeded its cleared level during the climb after a different level to that correctly read back was set on the FMS. As a result, it came into conflict with an Alitalia A321 and this was resolved by responses to coordinated TCAS RAs. STCA alerts did not enable ATC resolution of the conflict and it was concluded that a lack of ATC capability to receive Mode S EHS DAPs - since rectified - was a contributory factor to the outcome.)
  • DH8D / B772, vicinity Sydney Australia, 2016 (Synopsis: On 9 December 2016, a Bombardier DHC8-400 departing Sydney lost prescribed separation against an inbound Boeing 777-200 after its crew failed to ensure that the aircraft levelled as cleared at 5,000 feet and this was exceeded by 600 feet. The Investigation found that the First Officer, as Pilot Flying, had disconnected the autopilot prior to routinely changing the selected airspeed because it tended to disconnect when this was done with altitude capture mode active but had then failed to re-engage it. The Captain's lack of effective monitoring was attributed to distraction as he sought to visually acquire the conflicting traffic.)
  • A346, en route, eastern Indian Ocean, 2013 (Synopsis: On 3 February 2013, an Airbus A340 crew in the cruise in equatorial latitudes at FL350 in IMC failed to use their weather radar properly and entered an area of ice crystal icing outside the prevailing icing envelope. A short period of unreliable airspeed indications on displays dependent on the left side pitot probes followed with a brief excursion above FL350 and reversion to Alternate Law. Excessive vibration on the left engine then began and a diversion was made. The engine remained in use and was subsequently found undamaged with the fault attributed to ice/water ingress due to seal failure.)
  • B763, en-route North Bay Canada, 2009 (Synopsis: On 19 June 2009 a Boeing 767-300 was level at FL330 in night IMC when the Captain’s altimeter and air speed indicator readings suddenly increased, the latter by 44 knots. The altimeter increase triggered an overspeed warning and the Captain reduced thrust and commenced a climb. The resultant stall warning was followed by a recovery. The Investigation found that a circuitry fault had caused erroneous indications on only the Captain’s instruments and that contrary to the applicable QRH procedure, no comparison with the First Officer’s or Standby instruments had been made. A related Operator FCOM error was also identified.)
  • B773, en route, northern Turkey, 2014 (Synopsis: On 8 August 2014, the First Officer of a Boeing 777 in the cruise at night at FL340 inadvertently input a change of desired track into the MCP selected altitude window whilst acting as both PF and PM during controlled rest by the aircraft commander. The aircraft then descended for nearly 2 minutes without her awareness until ATC queried the descent and it was arrested at FL317.)
  • B738, en-route, south south west of Brisbane Australia, 2013 (Synopsis: On 25 February 2013, a Boeing 737-800 about to commence descent from FL390 began to climb. By the time the crew recognised the cause and began to correct the deviation - their unintended selection of a inappropriate mode - the cleared level had been exceeded by 900 feet. During the recovery, a deviation from track occurred because the crew believed the autopilot had been re-engaged when it had not. The Investigation noted the failure to detect either error until flight path deviation occurred and attributed this to non-compliance with various operator procedures related to checking and confirmation of crew actions.)
  • B733, vicinity Helsinki Finland, 2008 (Synopsis: On 26 March 2008, a Ukraine International Airlines’ Boeing 737-300 being vectored by ATC to the ILS at destination Helsinki in IMC descended below its cleared altitude and came close to a telecommunications mast. ATC noticed the deviation and instructed a climb. The investigation attributed the non-compliance with the accepted descent clearance to the failure of the flight crew to operate in accordance with SOPs. It was also noted that the way in which ATC safety systems were installed and configured at the time of the occurrence had precluded earlier ATC awareness of the hazard caused by the altitude deviation.)
  • B734 / MD81, en-route, Romford UK, 1996 (Synopsis: On 12 November 1996, a B737-400 descended below its assigned level in one of the holding patterns at London Heathrow in day IMC to within 100 feet vertically and between 680 and 820 metres horizontally of a MD-81 at its correct level, 1000 feet below. STCA prompted ATC to intervene and the 737 climbed back to its cleared level. Neither aircraft was fitted with TCAS 2 or saw the other visually.)