An instrument that records the performance and condition of an aircraft in flight.
An aircraft flight recorder records many different operating conditions of a flight and provides information that may be difficult or impossible to obtain by any other means. By regulation in most countries in the world, newly manufactured aircraft must monitor at least twenty-eight important parameters. These include time, altitude, airspeed, heading, vertical acceleration, and aircraft pitch. Some recorders can record the status of more than three hundred additional in-flight characteristics that can aid in an accident investigation. Some of these include flap position, autopilot mode, and even smoke alarms. To ensure that a large amount of information is recorded, a flight recorder is able to record for at least twenty-five hours.
Computer programs have been written to take flight recorder data and reconstruct animated videos of aircraft flight. The animation allows the investigation team to view the last moments of a flight prior to an accident. In the event of an accident, investigators can visualize the instrument readings, power settings, airplane’s attitude, and other important characteristics of a given flight.
A cockpit voice recorder records the flight crew’s voices, as well as other sounds within the cockpit. Communications with air traffic control, automated radio weather briefings, and conversation between the pilots and ground or cabin crew are recorded. Sounds of interest to an investigation board, including engine noise, stall warnings, landing gear extension and retraction, and any clicking or popping noises, are typically recorded. Based on these sounds, important flight parameters, such as speed, system failures, and the timing of certain events can often be determined.
In the event of an accident, an investigation committee creates a written transcript of the cockpit recorder tape. Local standard times associated with the accident sequence are determined for every event on the transcript. This transcript contains all the pertinent portions of the cockpit recording. Due to the highly sensitive nature of the verbal communications inside the cockpit, a high degree of security is provided for the cockpit recorder tape and its transcript. The timing of release and the content of the written transcript are strictly regulated.
The idea of a device to record both the voices and the instrument readings in the cockpit of an aircraft was originally conceived by Dr. David Warren at the Aeronautical Research Laboratory in Melbourne, Australia, in the 1950’s. A demonstration unit was constructed in 1957. Although Australian aviation authorities did not initially approve the device, it was taken to Great Britain and the United States for further development.
On June 10, 1960, a Trans-Australian Airlines Fokker F-27 crashed while landing at an airport in Queensland, Australia, killing all twenty-nine people on board. The subsequent board of inquiry was unable to arrive at any definite conclusions as to the factors underlying the accident. The board recommended that all airliners be fitted with flight recorders. In 1961, Australia became one of the first countries to make flight recorders mandatory in aircraft. Any craft with a takeoff weight greater than 12,568 pounds must carry both a cockpit voice recorder and a flight data recorder.
Flight recorders and cockpit voice recorders, also known as black boxes, are actually painted bright orange to aid in their recovery following an accident. They have provided critical clues in solving the mysteries associated with many of the world’s air disasters and have also been invaluable in helping to prevent future accidents.
Flight recorders and cockpit voice recorders are housed in titanium boxes that are lined with many layers of insulating material. This design protects the recorders against impacts that produce accelerations up to 3,400 times the acceleration of gravity, against fires of up to 2,000 degrees Fahrenheit (1,093 degrees Celsius), and against pressures at water depths of up to 20,000 feet. The recording devices are protected against contact with seawater and inadvertent erasure of recorded information. These specifications preserve the devices in the most serious accidents and in extreme climatic conditions. In addition, the boxes are fitted with battery-powered ultrasonic beacons that aid with underwater recovery. The beacons can transmit pulses from water depths of up to 14,000 feet for at least thirty days over a range of 2 miles.
Because they are more reliable and require minimal maintenance, computer memory chips have replaced most magnetic tapes as the recording media. Flight recorders are connected to a flight data acquisition unit that processes, digitizes, and formats the data for recording on the memory chips. Both the flight recorder and the cockpit voice recorder are carried in the tail of an aircraft. Flight data recorders reveal what happened in an accident, whereas cockpit data recorders reveal why it happened.
Even before a crash occurs, it is possible to monitor the safety of flights by using a quick access recorder. This device records even more parameters than a typical flight recorder and samples the data at higher rates for a longer duration of time. The data are stored on an optical disk and can be studied to identify problems before they become fatal. A ground-based computer analyzes the data and determines what is going wrong, rather than what went wrong.
Launius, Roger D., ed. Innovation and the Development of Flight. College Station: Texas A&M University Press, 1999. Excellent description of the history of the technological innovations in aeronautics. Trujillo, Anna C. Effects of Historical and Predictive Information on the Ability of Transport Pilot to Predict and Alert. Hampton, Va.: National Aeronautics and Space Administration, 1994. Useful technical discussion about the operation and uses of flight recorders. United States Federal Aviation Administration. Airworthiness and Operational Approval of Digital Flight Data Recorder Systems. Washington, D.C.: U.S. Federal Aviation Administration, 1999. Description of flight recording systems and necessary specifications to meet certification. Veatch, D. W., and R. K. Bogue. Analogue Signal Condition for Flight Test Instrumentation. Neuilly-sur-Seine, France: North Atlantic Treaty Organization, 1986. Discusses the operation and mechanics of flight recorders.
National Transportation Safety Board
Pilots and copilots
The cockpit voice recorder (left) and the flight data recorder (held by engineer) help investigators reconstruct the events leading up to crashes and other midair incidents.