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.
• Post crash fire is often a result of a CFIT due to the combined presence of heat/fire sources and ruptured fuel tanks/lines.

Generic Scenarios

• Pilot-induced situation: The pilot encounters weather conditions that are worse than forecast and, in an attempt to maintain or regain visual contact with the ground in an area of very low cloud, descends below Minimum Safe Altitude (MSA) and the aircraft strikes the ground. Contributing to this accident is 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 gives an aircraft which was still at 210 KIAS an intermediate heading towards the ILS centreline during a radar vectored initial approach but is subsequently distracted and fails to issue the intercept heading for the ILS LLZ. When the flight crew, who are unfamiliar with the approach, fail to notice the situation in time to query it, the aircraft flies beyond the centreline and into high terrain on the other side before resolution is 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 and Defences

• Adherence to Standard Operating Procedures (SOPs).
• Maintaining situational awareness in relation to terrain.
• More widespread equipment of aircraft with TAWS.
• Greater awareness of Approach and Landing risks.
• Continuous Descent Final Approaches (CDFA).
• Minimum safe altitude warning (MSAW).
• Electronic Terrain and Obstacle Data (eTOD)
• Use of radio altimeters

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:

• ALAR Briefing Note 5.1 - Approach Hazard Awareness

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

• CAD 516 - Ground Proximity Warning System (GPWS): Guidance Material, April 2013

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

• Correcting the Effects of Magnetic Variation

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