Download Blackbox Call Recorder
Aurora Benskin
There are two types of flight recording devices: the flight data recorder (FDR) preserves the recent history of the flight through the recording of dozens of parameters collected several times per second; the cockpit voice recorder (CVR) preserves the recent history of the sounds in the cockpit, including the conversation of the pilots. The two devices may be combined into a single unit. Together, the FDR and CVR objectively document the aircraft's flight history, which may assist in any later investigation.
The two flight recorders are required by international regulation, overseen by the International Civil Aviation Organization, to be capable of surviving the conditions likely to be encountered in a severe aircraft accident. For this reason, they are typically specified to withstand an impact of 3400 g and temperatures of over 1,000 C (1,830 F), as required by EUROCAE ED-112. They have been a mandatory requirement in commercial aircraft in the United States since 1967. After the unexplained disappearance of Malaysia Airlines Flight 370 in 2014, commentators have called for live streaming of data to the ground, as well as extending the battery life of the underwater locator beacons.
One of the earliest and proven attempts was made by François Hussenot and Paul Beaudouin in 1939 at the Marignane flight test center, France, with their "type HB" flight recorder; they were essentially photograph-based flight recorders, because the record was made on a scrolling photographic film 8 metres (8.7 yd) long by 88 millimetres (3.5 in) wide. The latent image was made by a thin ray of light deviated by a mirror tilted according to the magnitude of the data to be recorded (altitude, speed, etc.).[1] A pre-production run of 25 "HB" recorders was ordered in 1941 and HB recorders remained in use in French flight test centers well into the 1970s.[2][3]
In 1947, Hussenot founded the Société Française des Instruments de Mesure with Beaudouin and another associate, so as to market his invention, which was also known as the "hussenograph". This company went on to become a major supplier of data recorders, used not only aboard aircraft but also trains and other vehicles. SFIM is today part of the Safran group and is still present in the flight recorder market. The advantage of the film technology was that it could be easily developed afterwards and provides a durable, visual feedback of the flight parameters without needing any playback device. On the other hand, unlike magnetic tapes or later flash memory-based technology, a photographic film cannot be erased and reused, and so must be changed periodically. The technology was reserved for one-shot uses, mostly during planned test flights: it was not mounted aboard civilian aircraft during routine commercial flights. Also, cockpit conversation was not recorded.
Another form of flight data recorder was developed in the UK during World War II. Len Harrison and Vic Husband developed a unit that could withstand a crash and fire to keep the flight data intact. The unit was the forerunner of today's recorders, in being able to withstand conditions that aircrew could not. It used copper foil as the recording medium, with various styli, corresponding to various instruments or aircraft controls, indenting the foil. The foil was periodically advanced at set time intervals, giving a history of the aircraft's instrument readings and control settings. The unit was developed at Farnborough for the Ministry of Aircraft Production. At the war's end the Ministry got Harrison and Husband to sign over their invention to it and the Ministry patented it under British patent 19330/45.
The first modern flight data recorder, called "Mata Hari", was created in 1942 by Finnish aviation engineer Veijo Hietala. This black high-tech mechanical box was able to record all important details during test flights of fighter aircraft that the Finnish army repaired or built in its main aviation factory in Tampere, Finland.[4]
During World War II both British and American air forces successfully experimented with aircraft voice recorders.[5] In August 1943 the USAAF conducted an experiment with a magnetic wire recorder to capture the inter-phone conversations of a B-17 bomber flight crew on a combat mission over Nazi-occupied France.[6] The recording was broadcast back to the United States by radio two days afterwards.
Warren built a prototype FDR called "The ARL Flight Memory Unit" in 1956,[9] and in 1958 he built the first combined FDR/CVR prototype.[8][10] It was designed with civilian aircraft in mind, explicitly for post-crash examination purposes.[11] Aviation authorities from around the world were largely uninterested at first, but this changed in 1958 when Sir Robert Hardingham, the secretary of the British Air Registration Board, visited the ARL and was introduced to David Warren.[7] Hardingham realized the significance of the invention and arranged for Warren to demonstrate the prototype in the UK.[9]
Carriage of data recording equipment became mandatory in UK-registered aircraft in two phases; the first, for new turbine-engined public transport category aircraft over 12,000 lb (5,400 kg) in weight, was mandated in 1965, with a further requirement in 1966 for piston-engined transports over 60,000 lb (27,000 kg), with the earlier requirement further extended to all jet transports. One of the first UK uses of the data recovered from an aircraft accident was that recovered from the Royston "Midas" data recorder that was on board the British Midland Argonaut involved in the Stockport Air Disaster in 1967.[13]
A flight recorder was invented and patented in the United States by Professor James J. "Crash" Ryan, a professor of mechanical engineering at the University of Minnesota from 1931 to 1963. Ryan's "Flight Recorder" patent was filed in August 1953 and approved on November 8, 1960, as US Patent 2,959,459.[14] A second patent by Ryan for a "Coding Apparatus For Flight Recorders and the Like" is US Patent 3,075,192[15] dated January 22, 1963. An early prototype of the Ryan Flight Data Recorder is described in the January 2013 Aviation History article "Father of the Black Box" by Scott M. Fisher.[16]
Ryan, also the inventor of the retractable safety seat belt now required in automobiles, began working on the idea of a flight recorder in 1946, and invented the device in response to a 1948 request from the Civil Aeronautics Board aimed at establishing operating procedures to reduce air mishaps. The requirement was for a means of accumulating flight data. The original device was known as the "General Mills Flight Recorder".
The benefits of the flight recorder and the coding apparatus for flight recorders were outlined by Ryan in his study entitled "Economies in Airline Operation with Flight Recorders" which was entered into the Congressional Record in 1956. Ryan's flight recorder maintained a continuing recording of aircraft flight data such as engine exhaust temperature, fuel flow, aircraft velocity, altitude, control surfaces positions, and rate of descent.
His patent was for a device for recording audio of pilot remarks and engine or other sounds to be "contained with the in-flight recorder within a sealed container that is shock mounted, fireproofed and made watertight" and "sealed in such a manner as to be capable of withstanding extreme temperatures during a crash fire". The CSR was an analog device which provided a continuous erasing/recording loop (lasting 30 or more minutes) of all sounds (explosion, voice, and the noise of any aircraft structural components undergoing serious fracture and breakage) which could be overheard in the cockpit.[22]
Magnetic tape and wire voice recorders had been tested on RAF and USAAF bombers by 1943 thus adding to the assemblage of fielded and experimental electronic devices employed on Allied aircraft. As early as 1944 aviation writers envisioned use of these recording devices on commercial aircraft to aid incident investigations.[25] When modern flight recorders were proposed to the British Aeronautical Research Council in 1958, the term "black box" was in colloquial use by experts.[26]
By 1967 when flight recorders were mandated by leading aviation countries, the expression had found its way into general use: "These so-called 'black boxes' are, in fact, of fluorescent flame-orange in colour."[27] The formal names of the devices are flight data recorder and cockpit voice recorder. The recorders must be housed in boxes that are bright orange in color to make them more visually conspicuous in the debris after an accident.[28]
Modern FDRs are typically double wrapped in strong corrosion-resistant stainless steel or titanium, with high-temperature insulation inside. Modern FDRs are accompanied by an underwater locator beacon that emits an ultrasonic "ping" to aid in detection when submerged. These beacons operate for up to 30 days and are able to operate while immersed to a depth of up to 6,000 meters (20,000 ft).[31][32]
A cockpit voice recorder (CVR) is a flight recorder used to record the audio environment in the flight deck of an aircraft for the purpose of investigation of accidents and incidents. This is typically achieved by recording the signals of the microphones and earphones of the pilots' headsets and of an area microphone in the roof of the cockpit. The current applicable FAA TSO is C123b titled Cockpit Voice Recorder Equipment.[33]
The earliest CVRs used analog wire recording, later replaced by analog magnetic tape. Some of the tape units used two reels, with the tape automatically reversing at each end. The original was the ARL Flight Memory Unit produced in 1957 by Australian David Warren and instrument maker Tych Mirfield.[39][40]
Other units used a single reel, with the tape spliced into a continuous loop, much as in an 8-track cartridge. The tape would circulate and old audio information would be overwritten every 30 minutes. Recovery of sound from magnetic tape often proves difficult if the recorder is recovered from water and its housing has been breached. Thus, the latest designs employ solid-state memory and use fault tolerant digital recording techniques, making them much more resistant to shock, vibration and moisture. With the reduced power requirements of solid-state recorders, it is now practical to incorporate a battery in the units, so that recording can continue until flight termination, even if the aircraft electrical system fails.
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