Controlled Flight Into Terrain (CFIT)
Controlled Flight Into Terrain (CFIT)
Description
Controlled Flight into Terrain (CFIT) occurs when an airworthy aircraft under the complete control of the pilot is inadvertently flown into terrain, water, or an obstacle. The pilots are generally unaware of the danger until it is too late.
Most CFIT accidents occur in the approach and landing phase of flight and are often associated with non-precision approaches.
Many CFIT accidents occur because of loss of situational awareness, particularly in the vertical plane, and many crash sites are on the centreline of an approach to an airfield. Lack of familiarity with the approach or misreading of the approach plate are common causal factors, particularly where the approach features steps down in altitude from the initial approach fix to the final approach fix.
Effects
- Collision with the ground resulting in Hull Loss and fatalities/injuries.
Defences
- Standard Operating Procedures (SOPs).
- Terrain Avoidance Warning Systems (TAWS).
- Situational awareness in relation to terrain
Typical Scenarios
- Pilot-induced situation: The pilot encountered weather conditions that were worse than forecast and, in an attempt to maintain or regain visual contact with the ground in an area of very low cloud, descended below Minimum Safe Altitude (MSA) and the aircraft struck the ground. Contributing to this accident was the pilot's over-reliance on GPS while attempting to maintain Visual Meteorological Conditions (VMC) and a resultant lack of adequate situational awareness of terrain.
- ATCO-induced situation: The controller gave an aircraft which was still at 210 KIAS an intermediate heading towards the ILS centreline during a radar vectored initial approach but was subsequently distracted and failed to issue the intercept heading for the ILS LLZ. When the flight crew, who were unfamiliar with the approach, failed to notice the situation in time to query it, the aircraft flew beyond the centreline and into high terrain on the other side before resolution was possible.
Contributory Factors
- Weather: Rain, turbulence, and icing, may increase the workload of the pilot and cause interference reducing the accuracy of radio navigation beacons. Poor visibility, particularly at night can contribute to disorientation and loss of situational awareness.
- Approach Design and documentation: The depiction of an approach, and particularly step down fixes, on Terminal Approach Procedure (TAP) plates may not be clear. Approaches may take aircraft close to high terrain in order to comply with diplomatic or noise abatement constraints, or to deconflict with departure routes.
- Failure to use Standard Phraseology leading to confusion and misunderstanding.
- Pilot fatigue and disorientation. Approach and landing is a demanding phase of flight for pilots.
Accident Precursors
Study of CFIT accidents has enabled a large number of accident precursors to be identified. These precursors are not necessarily contributing factors, though some may be; but they are warnings revealing that a weakness has been detected in existing defence mechanisms. The identification of an accident precursor usually necessitates action to strengthen these defences.
The article CFIT Precursors and Defences lists those CFIT precursors which have so far been identified, together with suggested lines of defence.
Solutions
- More widespread equipment of aircraft with TAWS.
- Greater awareness of Approach and Landing risks.
- Continuous Descent Final Approaches (CDFA).
- MSAW (MSAW) systems.
- Electronic Terrain and Obstacle Data (eTOD)
Accidents and Serious Incidents (approach and landing)
On 11 February 2022 an Airbus A320 making a visual approach to Guadeloupe at night was advised by ATC of a descent below the minimum safe altitude after continuing the approach after visual reference was temporarily lost. A repeat of this warning by ATC prompted crew recognition that the aircraft was not on the required approach track or profile and a go around was initiated from 460 feet agl. The decision to attempt a visual approach in unsuitable circumstances and a delay in recognising the need for a go-around were found to have been symptomatic of poor tactical decision making.
On 25 October 2022, a Boeing 777-300ER encountered deteriorating weather conditions after initiating a delayed arrival diversion from Singapore Changi to nearby Batam where four approaches were flown and a ‘MAYDAY Fuel’ declared before a landing was achieved. By this time, the fuel remaining was “significantly below final reserve” although the actual figure was not published in the Investigation Report. It was concluded that the delay in commencing the diversion and the inappropriate attempt to perform an autoland on RWY04 at Batam airport by the flight crew contributed to the potentially hazardous circumstances.
On 6 December 2019, a Boeing 737-800 below Decision Altitude on an ILS approach at Paris Orly was unexpectedly instructed to go-around in day VMC without explanation. The go around was mishandled and the aircraft began to descend after initially climbing which triggered EGPWS Warnings and controller alerting before recovery was achieved. It was suspected that surprise at the go-around and the early climbing turn required may have initiated the crew’s mismanagement of automated flight path control with further surprise leading to failure to revert to manual control when they no longer understood the automated system responses to their inputs.
On 18 October 2019, a Boeing 787-9 descending to 4,500 feet to join the ILS for runway 25R at Hong Kong at 15 nm from touchdown failed to establish on the localiser. The autopilot was disconnected and the aircraft manually positioned onto the localiser from the north, establishing at 12 nm with terrain proximity not sufficient to activate the EGPWS. It was found that the deviation was attributable to an anomaly in the aircraft type Autopilot Flight Director System, and a corresponding Alert Service Bulletin was issued by Boeing to replace the faulty system component.
On 22 November 2021, a Fokker F100 crew discovered as they neared their destination, Paraburdo, that the forecast weather was so inaccurate that instead of the anticipated benign conditions, a much lower cloud base prevailed. A delay in recognising the implications of initially unsuccessful approaches and difficulty in obtaining updated weather for diversion options resulted in a fourth approach being intentionally continued significantly below minima, albeit successfully. Relevant aircraft operator procedures were identified as inadequate.
On 22 April 2019, a Eurocopter-Kawasaki BK-117C-1 helicopter was being positioned for an aeromedical evacuation the following day when it was unintentionally flown into the sea at night. The three crew members were able to evacuate from the partially submerged aircraft before it sank. The accident was attributed to the single pilot’s loss of situational awareness due to loss of visual depth perception when using night vision goggles. The relevant aircraft operator procedures and the applicable regulatory requirements were both found be inadequate relative to the operational risk which the flight involved.
On 20 October 2021, the flight crew of a Bombardier CRJ1000 making a LNAV/VNAV approach at Nantes using Baro-VNAV minima read back an incorrect QNH which was not noticed by the controller. The crew then flew the approach approximately 530 feet below the procedure vertical profile which led to the MSAW system being activated and advised to the flight. The crew response was delayed until the controller had twice repeated the correct QNH after which the error was recognised and the vertical profile corrected. The investigation noted that neither the operator’s procedures nor aircraft instruments allowed straightforward crew detection of their error.
On 23 January 2020, a Bombardier CRJ700 making a HUD-supported manual Cat 3a ILS approach to Lyon Saint-Exupéry in freezing fog conditions deviated from the required flight path localiser and reached a minimum of 265 feet agl before a go around was initiated without initially being flown in accordance with standard procedures. The Captain involved was relatively new to type and had not previously flown such an approach in actual low visibility conditions. The Investigation was not able to determine exactly what contributed to the approach and initial go around being misflown but identified a number of possible contributors.
On 1 November 2021, a deHavilland DHC6-300 crew en-route to Fort Simpson realised that they had insufficient fuel on board to reach their intended destination and therefore decided to attempt a diversion to the nearest available airport at Fort Providence. As fuel available dwindled, one engine was shut down but after an inadvertent fuel tank selection, the initially intended diversion was no longer possible and a forced landing in a bog was successfully accomplished. The Training Captain involved had developed a habit of performing checklists silently and from memory after gaining all his professional pilot experience at the same operator.
On 4 March 2019, an Embraer 145 attempting to land off an ILS approach at Presque Isle in procedure-minima weather conditions flew an unsuccessful first approach and a second in similar conditions which ended in a crash landing abeam the intended landing runway substantially damaging the aircraft. The accident was attributed to the crew decision to continue below the applicable minima without acquiring the required visual reference and noted that the ILS localiser had not been aligned with the runway extended centreline and that a recent crew report of this fault had not been promptly passed to the same Operator.
On 1 January 2020, an Airbus A350-900 made an unstabilised night ILS approach to Frankfurt in good visual conditions, descending prematurely and coming within 668 feet of terrain when 6nm from the intended landing runway before climbing to position for another approach. A loss of situational awareness was attributed to a combination of waypoint input errors, inappropriate autoflight management and communication and cooperation deficiencies amongst the operating and augmenting flight crew on the flight deck.
On 10 September 2017, the First Officer of a Gulfstream G550 making an offset non-precision approach to Paris Le Bourget failed to make a correct visual transition and after both crew were initially slow to recognise the error, an unsuccessful attempt at a low-level corrective realignment followed. This had not been completed when the auto throttle set the thrust to idle at 50 feet whilst a turn was being made over the runway ahead of the displaced threshold and one wing was in collision with runway edge lighting. The landing attempt was rejected and the Captain took over the go-around.
On 24 February 2016 a DHC6 (9N-AHH) on a VFR flight to Jomsom which had continued towards destination after encountering adverse weather impacted remote rocky terrain at an altitude of almost 11,000 feet approximately 15 minutes after takeoff after intentionally and repeatedly entering cloud in order to reach the destination. The aircraft was destroyed and all on board were killed. The Investigation attributed this to the crew’s repeated decision to fly in cloud and their deviation from the intended route after losing situational awareness. Spatial disorientation followed and they then failed to respond to repeated EGPWS cautions and warnings.
On 2 May 2015, a Boeing 777-200 deviating very significantly north of its normal route from Malabo to Douala at night because of convective weather had just turned towards Douala very close to 13,202 feet high Mount Cameroon whilst descending through 5000 feet, when an EGPWS TERRAIN AHEAD alert and ‘PULL UP’ warning prompted an 8,000 foot climb which passed within 2,100 feet of terrain when close to and still below the summit. The Investigation attributed the dangerous event primarily to the augmented crew’s absence of situational awareness and the operator’s failure to risk-assess the route involved.
On 23 May 2022, an Airbus A320 came within six feet of the ground without crew awareness during a go around from a RNP BaroVNAV approach after failing to obtain visual reference. The descent below minimum altitude followed use of an incorrect QNH passed by ATC but not identified as such. The lack of an EGPWS warning was due to the non-current EGPWS version for which upgrading had not been mandated. It was concluded that the regulatory intention in Europe to transition from ILS to RNP approaches had not led to any recognition of the potential impact on operational safety.
Accidents and Serious Incidents (en route)
On 24 March 2015, after waiting for the Captain to leave the flight deck and preventing his return, a Germanwings A320 First Officer put his aircraft into a continuous descent from FL380 into terrain killing all 150 occupants. Investigation concluded the motive was suicide, noted a history of mental illness dating from before qualification as a pilot and found that prior to the crash he had been experiencing mental disorder with psychotic symptoms which had not been detected through the applicable process for medical certification of pilots. Conflict between the principles of medical confidentiality and wider public interest was identified.
On 23 January 2013, a Canadian-operated DHC6 on day VFR positioning flight in Antarctica was found to have impacted terrain under power and whilst climbing at around the maximum rate possible. The evidence assembled by the Investigation indicated that this probably occurred following entry into IMC at an altitude below that of terrain in the vicinity having earlier set course en route direct to the intended destination. The aircraft was destroyed and there were no survivors.
On 15 March 2012, a Royal Norwegian Air Force C130J-30 Hercules en route on a positioning transport flight from northern Norway to northern Sweden crossed the border, descended into uncontrolled airspace below MSA and entered IMC. Shortly after levelling at FL 070, it flew into the side of a 6608 foot high mountain. The Investigation concluded that although the direct cause was the actions of the crew, Air Force procedures supporting the operation were deficient. It also found that the ATC service provided had been contrary to regulations and attributed this to inadequate controller training.
On 9 May 2012, a Sukhoi RRJ-95 on a manufacturer-operated demonstration flight out of Jakarta Halim descended below the promulgated safe altitude and, after TAWS alerts and warnings had been ignored, impacted terrain in level flight which resulted in the destruction of the aeroplane and death of all 45 occupants. The Investigation concluded that that the operating crew were unaware that their descent would take them below some of the terrain in the area until the alerts started and then assumed they had been triggered by an incorrect database and switched the equipment off.
On 19 December 2002, a Piper PA-46 Malibu, after takeoff from Son Bonet Aerodrome, penetrated the control zone (CTR) of Palma de Mallorca tower. The pilot was instructed to leave the CTR and the aircraft headed towards mountainous terrain to the north of the island where the flight conditions were below the VFR minimum. In level flight the aircraft impacted terrain at an altitude of 2000 ft killing all three occupants.
On 26 August 2003, at night, a Eurocopter EC155, operated by Hong Kong Government Flight Service (GFS), performing a casualty evacuation mission (casevac), impacted the elevated terrain in Tung Chung Gap near Hong Kong International airport.
On 27 September 2000, a Cessna 185, struck a snow covered hillside, probably while in controlled flight, en-route from Smithers BC, Canada.
Related Articles
- Accident and Serious Incident Reports: CFIT - a list of all Accident and Serious Incidents within SKYbrary which resulted in, or involved a severe risk of, controlled flight into terrain.
- CFIT Precursors and Defences
Further Reading
Flight Safety Foundation CFIT Reduction Products
- CFIT Checklist (available in Arabic, Chinese, English, French, Russian and Spanish), external links
- CFIT Education and Training Aid
The Flight Safety Foundation ALAR Toolkit
The Flight Safety Foundation ALAR Toolkit provides useful training information and guides to best practice. All the Briefing Notes are on the SKYbrary Bookshelf and may be acceessed via the link above. A copy of the ALAR Toolkit on CD may also be purchased from the Foundation. See especially:
HindSight Articles:
- HindSight1 - Controlled Flight Into Terrain
- HindSight2 - Seminole in California
- HindSight3 - Descent Below the Glideslope
- HindSight3 - Misunderstandings: Wrong QNH Setting
- HindSight4 - Economy versus Safety - the Professional’s Dilemma
- HindSight6 - Alert Controller Prevents CFIT Accident
UK CAA
- UKCAA CAP710 - The "On the Level" Project
- UK CAA FODCOM 6/2007: Avoidance of Controlled Flight Into Terrain (CFIT) - Operational and Training Considerations
CAD Hong Kong
Airbus Safety Library
- Airbus Approach Techniques Briefing Note - Aircraft Energy Management during Approach
- Airbus Operational Environment Briefing Note - Enhancing Terrain Awareness
- FOBN - Approach Hazard Awareness offers a more expanded and categorised review of approach hazards
Boeing AERO magazine
Others
- Terrain Awareness and Warning Systems — TAWS (Pilot's Guide), Paul Novacek
- EASA video on Helicopter Distraction and CFIT
Terrain and Obstacle data
- ICAO Annex 15 Chapter 10 Terrain and Obstacle Data, Appendix 8 Numerical requirements for Terrain and obstacle data
- EUROCONTROL Terrain and Obstacle Manual, external link
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