Aviation Safety Glossary: CVR, FDR, CFIT, Stall and Ditching

Accident reports are written for specialists, and they lean on abbreviations and technical shorthand. This glossary explains the terms readers meet most often, in plain language and in the units aviation uses: feet, knots and nautical miles. It is a reference, not a teaching manual, and each entry is kept short.

Flight recorders

Two recorders are fitted to most large aircraft. Investigators often recover them first, because they hold the most objective record of what happened. They are popularly called black boxes, though they are painted bright orange so that they can be found in wreckage.

CVR (cockpit voice recorder)

The CVR records sound on the flight deck. That includes conversation between the pilots, radio calls, alerts and warnings, and background noise such as engine sound and switch clicks. Investigators use it to understand what the crew knew, what they discussed and when. It holds a limited period of audio, and the required length has increased over the years.

FDR (flight data recorder)

The FDR records technical parameters from the aircraft's systems. Typical examples are altitude, airspeed, heading, pitch and roll, engine settings and control positions. Modern recorders log hundreds or even thousands of parameters. Investigators can use the data to reconstruct the flight path and animate the final minutes.

Crash-protected memory

Both recorders store their data in a hardened unit built to survive impact, fire and deep water. Many also carry an underwater locator beacon, which sends out an acoustic pulse to help searchers find them after an accident at sea.

Flight-path and handling terms

CFIT (controlled flight into terrain)

CFIT describes an accident in which a serviceable aircraft, under the control of its crew, is flown into the ground, water or an obstacle without the crew being aware of the danger in time. The word "controlled" means the aircraft was not failing. It does not mean the crew intended the outcome. CFIT has historically been associated with approaches in poor visibility, night flying and mountainous terrain.

GPWS and TAWS

The ground proximity warning system (GPWS) was developed to reduce CFIT. It issues alerts when the aircraft is too close to the ground or descending too quickly. Its successor, the terrain awareness and warning system (TAWS), adds a digital terrain database and position data. This lets it warn of high ground well ahead of the aircraft.

Stall

An aerodynamic stall happens when the wing meets the air at too steep an angle, and lift drops sharply. It is not an engine problem, and the engines can be running normally. The key quantity is the angle of attack, the angle between the wing and the airflow. A stall can occur at any speed, in any attitude and at any altitude. The standard recovery is to reduce the angle of attack, then restore power and level the wings. Modern aircraft have stall warnings, such as a stick shaker or an audible alert, to give pilots notice before the wing stalls.

Go-around

A go-around is the decision to abandon an approach to land and climb away, either to try again or to divert. It is a normal, trained procedure. Investigators often study whether a crew should have gone around and when they chose to do so.

Wake-turbulence

Every aircraft generating lift leaves behind two rotating columns of air, trailing from the wingtips. This is wake-turbulence. It is strongest behind heavy aircraft flying slowly and can upset a smaller aircraft following too closely. Air traffic control applies minimum separation distances to manage the risk.

Emergencies and forced landings

Ditching

Ditching is a deliberate, controlled landing on water by an aircraft not designed to operate from it. It differs from a crash into the sea because the crew choose the time and place and prepare the cabin. Success depends on the sea state, the aircraft's attitude and speed at touchdown, and how quickly occupants can evacuate and be rescued. Airliners that fly long distances over water carry life rafts and life vests for this purpose.

Forced landing

A forced landing is an unplanned landing on land, usually after an engine failure or another problem that makes continued flight impossible.

MAYDAY and PAN-PAN

These are internationally recognised radio calls. MAYDAY signals grave and imminent danger. PAN-PAN signals an urgent situation that does not yet threaten life or the aircraft. Both give air traffic control priority information and allow rescue services to be alerted.

Investigation terms

Annex 13

Annex 13 to the Chicago Convention is the international standard for aircraft accident and incident investigation. Published by the International Civil Aviation Organization (ICAO), it sets out which state leads an inquiry and how others take part. It also sets out the purpose of an investigation, which is to prevent future accidents rather than to assign blame or liability.

Probable cause

In many national reports, including those of the National Transportation Safety Board in the United States, the probable cause is the investigators' conclusion about why the accident happened. Other authorities use the phrases "causes" or "contributing factors". These are findings based on evidence, not legal judgments.

Safety recommendation

A safety recommendation is a formal proposal from an investigation body to a regulator, manufacturer or operator. It describes a change that could prevent a similar event. It is not binding on the recipient, but regulators are generally expected to respond to it.

UTC (Coordinated Universal Time)

UTC is the common time reference used in aviation records, so that events in different time zones can be compared. Reports usually give local time first, then the UTC equivalent.

Why the vocabulary matters

These terms are more than jargon. Each reflects a lesson learned. Recorders exist because investigators needed objective evidence. Terrain warnings grew out of repeated CFIT accidents. Ditching procedures and stall warnings came from studying how crews cope with unusual situations. Knowing the vocabulary makes it easier to read an official report and to see how its findings lead to changes in training, design and regulation.