DALLAS – The flight data recorder (FDR) is widely considered the most important witness in the investigation of air accidents. The history of the FDR is intriguing, and it has come a long way since its introduction.
For 70 years, flight recorders have been regarded as essential components of onboard equipment for both military and civilian aircraft all over the world. They are utilized not just for flight evaluation following an unforeseen event but also for pilot training, pilot skill assessment, onboard system diagnostics, and overall aircraft system evaluation.
The device is commonly referred to as a “black box,” which is an obsolete term that has become a misnomer because they are now mandated to be painted bright orange to aid in their recovery following an accident. The name “black box” originated with the development of radio, radar, and electronic navigational aids in British and Allied combat aircraft during World War II. These often-secret electronic devices were literally housed in black, non-reflective boxes or housings.
The flight data recorder (FDR) saves the recent history of the flight through the recording of dozens of parameters collected multiple times per second, while the cockpit voice recorder (CVR) preserves the recent history of the sounds in the cockpit, including the pilots’ dialogue. It is possible to integrate the two devices into a single unit. The FDR and CVR work together to objectively document the aircraft’s flight history, which can help with any subsequent investigation.
As we will see in this deep dive, the invention of the flight data recorder is unlikely to be attributed to a single person, as with most innovative equipment.
François Hussenot and Paul Beaudouin attempted one of the first and proven attempts in 1939 at the Marignane flight test center in 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 meters (8.7 yards) long by 88 millimeters (3.5 in) wide.
A thin ray of light diverted by a mirror slanted according to the magnitude of the data to be recorded created the latent picture (altitude, speed, etc.). In 1941, a pre-production run of 25 “HB” recorders was ordered, and HB recorders were used in French flight test labs until the 1970s.
Hussenot, Beaudouin, and another collaborator created the Société Française des Instruments de Mesure in 1947 to market his invention, which was also known as the “hussenograph.” This company grew to be a major supplier of data recorders, which were used not just on planes but also on trains and other vehicles.
World War II Advances
During World War II, the United Kingdom created a new type of flight data recorder. To keep the flight data intact, Len Harrison and Vic Husband created a unit that could resist a crash and fire. In being able to endure situations that aircrew couldn’t, the unit was a predecessor of today’s recorders.
Copper foil was employed as the recording medium, with numerous styli indenting the foil to correspond to various instruments or aircraft controls. The foil was advanced at predetermined intervals, providing a historical record of the aircraft’s instrument data and control settings.
The facility was created for the Ministry of Aircraft Production at Farnborough. The Ministry was able to persuade Harrison and Husband to hand over their innovation to it at the end of the war, and the Ministry was able to patent it under British patent 19330/45.
Veijo Hietala, a Finnish aircraft engineer, invented the first modern flight data recorder, dubbed “Mata Hari,” in 1942. During test flights of fighter aircraft that the Finnish army repaired or produced in its main aviation facility in Tampere, Finland, this black high-tech mechanical box was able to record all critical details.
During the war, both the British and American air services experimented with aircraft voice recorders with great success. The United States Army Air Forces used a magnetic wire recorder to record the inter-phone discussions of a B-17 bomber flight crew on a combat mission over Nazi-occupied France in August 1943. Two days later, the recording was broadcast on the radio in the United States.
The first flight data recorders were developed in the 1950s. Originally, these were still basic metal foil-based devices. The initial ‘black box,’ which was introduced in 1958 after a series of fatal accidents involving the de Havilland DH 106 Comet, the first production airliner, could only measure five parameters: heading, altitude, airspeed, vertical acceleration, and time.
These parameters were again recorded by a stylus storing information on metal foil, so the information could, unfortunately, only be used once. It was soon discovered that they were substantially useless for assessing the causes of accidents.
Dr. David Warren first proposed the concept of a gadget that would record not just flight data but also voices and other sounds in airplane cockpits just before a 1954 crash. In Australia, the prototype he designed in the late 1950s was viewed with skepticism, but it was met with enthusiasm elsewhere in the world.
The concept for developing an exceptionally reliable recording device that could endure enormous trauma and deep saltwater immersion was sparked by a number of crashes in the early years of commercial jet aircraft travel.
The Comet Crashes
In 1949, British aviation company De Havilland introduced the Comet, the world’s first jet airliner. The public was captivated by the fast and comfortable jet. Seven Comets, however, crashed between 1952 and 1954, killing 110 people.
Several of the planes were destroyed high in the sky, leaving no survivors, witnesses, or immediate clues as to what had happened.
The whole fleet of Comets was grounded permanently in 1954, and the most thorough air crash investigation ever conducted commenced. It was eventually discovered that the crashes were caused by metal fatigue, which was exacerbated by the plane’s square windows.
Meanwhile, the Department of Civil Aviation in Australia convened an expert committee to explore the likely causes of the incidents. Dr. David Warren, a 28-year-old scientist at the federal government’s Aeronautical Research Laboratories (ARL) in Melbourne who specializes in aviation fuels, was one of these experts.
During the inconclusive meeting, Warren realized that the issue with discussing the Comet crashes was simply a lack of data. The flight crew, who were all killed, were frequently the people best placed to know what might have caused the crashes.
At the same time, he remembered seeing a device a few weeks prior at a trade show. This was a steel-wire-recording dictaphone designed in Germany.
The Cockpit Voice Recorder
Flight data recorders were used in some military test aircraft at the time, but not in commercial aircraft or for crash investigations. There were no voice recorders utilized at all.
Soon after, Warren sent an email to his boss asking that ARL construct a cockpit voice recorder, stating that knowing what the pilots were thinking at the time of the crash and why they took the judgments they did is often critical.
This, along with flight data, might be stored in a crashproof container. He also stated that as airplanes fly faster, higher, and further, crashes would become more common, and the need to understand why they happen will become more critical.
Warren’s supervisors displayed only a passing interest in the proposal and advised him to send it to ARL’s instruments section. The flight recorder project stalled as a result of the latter’s overstretching, and Warren resorted to working on a prototype in his garage on weekends.
Tom Keeble, Warren’s new, more supportive manager, pushed him to create a detailed document for dissemination across Australian aviation authorities by 1957. Keeble also set aside £600 for a professionally constructed prototype.
On the same sturdy steel wire, the device recorded four hours of cockpit sound and eight instrument readings four times a second. It was low-maintenance, automatically turned on and off with the aircraft’s engines, and was self-erasing (unless there was a crash).
Warren’s paper advocated for the installation of flight recorders in every major aircraft, addressing issues regarding weight, size, cost, pilot privacy, and maintenance. In Australia, however, it was met with a lack of interest, if not outright disdain. Keeble and Warren subsequently emailed it to appropriate organizations in other countries but received no response.
The lack of local interest stemmed in part from the fact that Australia had comparatively few aviation catastrophes and a notion that Britain and the United States, rather than Australia, were the centers of aeronautical innovation. (However, Australia was the first country to require the installation of both data and voice recorders in significant aircraft in 1967.)
Sir Robert Hardingham, Secretary of the British Air Registration Board, paid a visit to the ARL in early 1958. Lawrence Coombes, the ARL’s chief superintendent, presented Hardingham to Warren, who showed him the flight recorder, during the tour.
Despite Warren’s report being distributed to British aviation agencies earlier, it appears that Hardingham was unaware of the device. He was so delighted with the recorder that he encouraged Warren to bring it to the UK.
Warren stayed for a month, and the different aviation authorities to whom he demonstrated his flight recorder were enthralled.
It sparked a campaign to make flight records compulsory on all British civilian planes. Warren visited similar organizations in the United States on his way back to Australia but received little or no interest.
Warren had full support from the ARL upon his return. Lane Sear, Ken Fraser, and Walter Boswell from the instruments section were assigned to him as part of a team to construct a pre-production standard prototype, which was completed in 1962.
The device’s recording speed was boosted to 24 measurements per second, which was a significant improvement. A fire-resistant and shockproof enclosure, as well as a piece of ground-based decoding equipment, were also included. Additionally, magnetic tape was able to record thirty minutes of ambient cockpit noise.
In 1963, Australia became the first country in the world to require the compulsory installation of cockpit voice recorders. The United States also became the first to require flight data recorders, and in 1965, it became mandatory in the U.S. to install the cockpit voice recorder, and in 1967, a mandatory requirement in commercial aircraft.
The Australian government eventually received £1000 in compensation for ARL’s intellectual property, but it has gained no money from the creation of a technology that is placed in thousands of planes each year.
In 2010, David Warren passed away. For his contributions to aviation, he had been named an Officer of the Order of Australia eight years earlier.
US FDR Developments
The ARL did not apply for patents until many of the design components were already well-known. As the installation of flight recorders became necessary around the globe, this allowed companies in other parts of the world, particularly in the United States, to develop the notion and capitalize on a burgeoning market.
Professor James J. “Crash” Ryan, a mechanical engineering professor at the University of Minnesota from 1931 until 1963, designed and patented the flight recorder in the United States.
Ryan’s “Flight Recorder” patent was filed in August 1953 and issued as US Patent 2,959,459 on November 8, 1960. US Patent 3,075,192, dated January 22, 1963, is a second patent by Ryan for a “Coding Apparatus For Flight Recorders and the Like.” Scott M. Fisher’s January 2013 Aviation History article “Father of the Black Box” describes an early prototype of the Ryan Flight Data Recorder.
Edmund A. Boniface Jr., an aeronautical engineer with Lockheed Aircraft Corporation, designed and patented a “Cockpit Sound Recorder” (CSR). On February 2, 1961, he filed a patent application for an “Aircraft Cockpit Sound Recorder” with the US Patent Office. Some criticized the invention in 1961 as an “infringement of privacy.”
Boniface then applied for a “Cockpit Sound Recorder” (US Patent 3,327,067) on February 4, 1963, with the addition of a spring-loaded switch that allowed the pilot to erase the audio/sound tape recording after a safe flight and landing.
Boniface’s involvement in aircraft crash investigations in the 1940s, as well as the accident investigations into the loss of one of the wings at cruise altitude on each of two Lockheed Electra turboprop-powered aircraft (Flight 542 operated by Braniff Airlines in 1959 and Flight 710 operated by Northwest Orient Airlines in 1961), led him to wonder what the pilots might have said just prior to the wing loss and during the descent, as well as the type and nature of any sounds omitted.
The most revolutionary advances in-flight recorder technology occurred in the 1990s. Over the course of a decade, the ‘Solid State’ data recorder was able to record hundreds of metrics as well as two hours of speech recording. The Federal Aviation Administration issued a Code of Federal Regulations in 2002 that required aircraft produced after August 2002 to have at least 88 characteristics.
With the advent of digital recorders, the FDR and CVR can be manufactured in one fireproof, shockproof, and waterproof container as a combined digital cockpit voice and data recorder (CVDR). Currently, CVDRs are manufactured by L3Harris Technologies and Hensoldt among others.
The European Aviation Space Agency issued additional rules for black boxes in 2012, requiring them to have a minimum voice recording duration of 25 hours rather than two hours. These will take effect in January 2021.
In the aftermath of the MH370 catastrophe in 2014, one of the most recent changes took place. Because of its inexplicable disappearance, a 90-day underwater flight data recorder locator beacon was created. After an accident, this technology gives investigators extra time to search for the plane over water. In Europe, installing these has also become a requirement.
Many feel that the next stage will be to send real-time parameter data and audio recordings from the cockpit to the cloud.
Flight recorders are now required on all major aircraft across the world, and they have made a significant contribution to aviation safety.
Air crash investigators can download hours of cockpit conversation as well as enormous amounts of flight data captured just prior to the crash using ‘black box’ flight recorders. This assists them in determining the causes of a crash and aids in the prevention of future ones.
Because 80% of crashes involve a human aspect, the pilots’ communications with each other, with air traffic control, and with other planes are all crucial data.
The design of today’s FDR is governed by the internationally recognized standards and recommended practices relating to flight recorders which are contained in the International Civil Aviation Organization (ICAO) Annex 6, which makes reference to industry crashworthiness and fire protection specifications such as those to be found in the European Organisation for Civil Aviation Equipment documents EUROCAE ED55, ED56 Ficken A, and ED112 (Minimum Operational Performance Specification for Crash Protected Airborne Recorder Systems).
Specifically, the two flight recorders are required by international regulation, overseen by ICAO, 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.
In the United States, the Federal Aviation Administration (FAA) regulates all aspects of US aviation and cites design requirements in their Technical Standard Order, based on the EUROCAE documents, as do the aviation authorities of many other countries.
Featured image: A flight data recorder and a cockpit voice recorder are installed on their mounting trays in the rear fuselage of an aircraft. Photo: By YSSYguy at English Wikipedia, CC BY-SA 3.0. Article sources: National Museum Australia, ICAO.