The "Black Box" Cockpit-Voice-plus-Flight-Data-Recorder is the invention widely attributed to Dr David Warren (full name David Ronald de Mey Warren) of what was then known as the Aeronautical Research Laboratories (ARL) at Fishermans Bend, Melbourne, Australia. At the time of the invention, ARL was part of the Commonwealth of Australia's Department of Supply - ARL later became part of the Defence Science and Technology Organisation (DSTO), part of Australia's Department of Defence.
Following the rapid development of jet fighters during the Second World War, the British began to develop the first jet-powered airliner, the famous Comet, which first flew in the 1950s. However in 1953 a number of the aircraft crashed inexplicably, putting doubt in the public's mind about the safety of jets. Aircraft engineers and scientists all round the world were also perplexed. The cause of the crashes had to be found or the Comet would be doomed to failure. Many professional committees discussed the possible causes at endless meetings. Dr Warren, who was a combustion/fuels specialist, was one of those involved with some of these meetings, his role being to consider whether a fuel explosion could account for the crashes. It was at this time that he conceived the idea of some sort of recording of the flight crew's conversation, and of protecting the record so that it would survive the crash. Such recording would have a heavy bias in the field of electrical engineering. While Dr Warren had some competence in the electrical field, gathered mainly via self-interest in the field, he required electrical design assistance from specialists in that area.
Dr Warren, at age 29, first published his accident recorder concept in 1954 (Black Box Ref. 1 below). Basically his proposal included:
Dr Warren referred to his invention as the "ARL Flight Memory system". The term "black box" was believed to have been attributed to a journalist. In the early days black box was in common usage for such things as a mystery box of electronics for which the main interest was in what it does rather than how it works. Black Box has now become the accepted term for accident recorders even though, for aircraft, a readily distinguishable orange colour is standard.
An early version of the ARL Flight Memory system was produced and some limited flight testing, organised by Dr Warren, was performed (Ref. 2) in 1958 with particular emphasis on microphone options for cockpit voice recording. Ref. 2 also defined a requirement for the following additional capabilities:
With the help of work undertaken by instrument maker Tych Mirfield under an ARL contract, a recording unit was designed and built using magnetisable steel wire of 0.002 inch diameter as the recording medium. The wire was the same as that used in the German Minifon recorder. The ARL recorder was fully automatic for fit-and-forget operation with a "memory" mechanism that would store four hours of cockpit voice and flight data up to the moment of any accident, but would automatically erase older recordings making the wire reusable. Magnetic wire was in use before magnetic tape (that typically used a ferrous oxide coating of a plastic tape). Wire rather than tape was chosen by Dr Warren because of its compact size and its ability to withstand much higher temperatures than tape.
While some small interest was shown in the early version tested in 1958 overall it was very disappointing. Subsequently a decision was made to build an improved version that could be flight validated so Dr Warren could "show and tell" the doubters. In March 1961 Dr Warren proposed (Ref. 3) that an advanced system capable of demonstrating previously defined and some additional capabilities be developed and fully flight tested.
My black box involvement began in 1961 when the development of the improved system of airborne recording and ground station recovery equipment was undertaken prior to in-flight testing. This was my first meeting with David Warren and found him then to be an inspirational scientist well capable of "thinking outside the box". Our friendship endured through the years. Although Dr Warren was a combustion/fuels specialist, he had a keen interest in electrical science and was capable of defining the requirements in that area. However, he required electrical design specialists to assist in the development of the updated system. The updated system had the following characteritics:
My involvement, together with that of other scientific staff (Lane Sear and Walter Boswell, both deceased) aimed to update the early model Flight Memory system to a pre-production standard suitable for recording cockpit voice and instrument readings on a crash-survivable medium. The updated system included the magnetic wire recording unit developed with the help of instrument maker Tych Mirfield and was now mounted in a crashproof and fireproof enclosure with the addition of an airborne-standard connector for the flight test in which I was involved. Lane Sear (full name Walter Francis Lane Sear) and I (full name Kenneth Francis Fraser) had about equal share of the overall circuit design for the airborne recording and ground recovery electronic systems, and Walter Boswell accomplished the assembly. The pre-production prototype was installed in the Department of Civil Aviation Fokker Friendship aircraft, VH-CAV, and the test flight took place on 23 March 1962 departing from Essendon airport (in Melbourne, Australia). Recording and recovery of cockpit voice and flight data were 100% successful. It was my first flight test and I was aged 24 at the time.
While no tests were performed on a crash location beacon the idea was in the forefront of those being investigated by Dr Warren. A detachable recording medium within a foam plastic aerofoil and fitted with a radio beacon transmitter was one such possibility under review. It was based on a type that had been developed by the National Research Council of Canada. More details are provided in the 1962 Ref. 4 film.
At the time of the flight ARL was part of the Department of Supply, not the Department of Defence as became the case later. And so it was that we captured that small window where we could be involved with civil aircraft. Without that window I believe we would not have had the opportunity to pursue such a venture.
A major limitation of the use of magnetic wire was that, unlike magnetic tape, it was essentially a single recording track medium. That meant that the audio and flight data channels needed to be restricted to separate frequency bands. The flight data were time multiplexed and used a pseudo-digital recording technique. Graphical plots of the recovered data from the 1962 concept validation flight are included in the column of images on the right. A photograph of the intense fire test performed at ARL, also in 1962, of the recording within the fireproof enclosure is also included in the column of images on the right.
In anticipation of the coming British Ministry of Aviation (MOA) accident recording mandatory requirement, the British firm of S. Davall & Son approached ARL for the production rights. Subsequently the MOA announced a requirement for airliners to fit an FDR but a CDR was omitted in this initial requirement. British European Airways (BEA) contracted Davall to make the recorder but the electronics contract went to Plessey. The Davall "Red Egg" accident recorder using magnetic wire as the recording medium was developed based on the ARL system and won a large part of the British and overseas market at that time. Cockpit voice recording did not become mandatory in England until after the "Staines disaster" on 18 June 1972 when BEA Flight 548, on a scheduled passenger flight f rom London Heathrow to Brussels, crashed soon after take-off, killing all 118 people on board.
Prior to the 60th anniversary of the ARL/DSTO Melbourne laboratory in 1999 Dr Warren and I wrote a summary of the ARL Black Box history with the pre-1961 aspects being totally attributable to Dr Warren. This document (Ref. 5) reveals the difficulties presented with convincing people that the black box idea was worth pursuing. Doubters were plentiful. This document provides the most authentic summary information on the ARL Black Box.
Dr Warren, together with the team involved in the pre-production prototype development, were recognized in the Lawrence Hargrave Award granted by the Australian Division of The Royal Aeronautical Society in February 2001 (almost 40 years after the successful flight demonstration occurred). The award was presented by The Hon John Anderson MP, who was the Australian Minister for Transport at the time. A photograph of the award is included in the column of images on the right.
Apart from the Lawrence Hargrave Award mentioned above, Dr Warren has received a number of honours:
My involvement in the Black Box development has been reported in publications 9, 10, 25 and 41 on my List of Publications page. I still find it hard to comprehend that the work I did at about age 24 (my age at the time of the successful flight demonstration on the Fokker Friendship aircraft) is the item for which I have received most compliments.
Most of the Black Box hardware is held at the Scienceworks Museum, 2 Booker Street, Spotswood, Melbourne, Victoria 3015, Australia. The wire recorder is held at DSTO's Melbourne Laboratory, 506 Lorimer Street, Fishermans Bend, Victoria 3207, Australia.
Other sources of information on the Black Box are listed below. As mentioned earlier, Ref. 5 provides the most authentic summary information on the ARL Black Box. Author Jeremy Sear (Black Box Ref. 11) is a grandson of Lane Sear, a member of the team honored via the Lawrence Hargrave Award in 2001. Ref. 11 is a pdf formatted version of Jeremy Sear's original html document with updated links that I produced on 20-Jan-2013. Of special note is the book written by Janice Witham (Black Box Ref. 12) - she found "intrigue, drama, controversy, a dash of mystery and a lot of unanswered questions" in writing the book. Her book is the most comprehensive publication on the ARL Black Box development with particular reference to the personal background relating to Dr Warren and to the impediments he faced in gaining acceptance for his ideas. Films produced in 1962 and 1990 are referred to in Refs 4 and 9 respectively. They can be run on-line or downloaded. Ironically, the ARL Black Box topic has come alive in recent years after being dormant for about 40 years.
In 2012 schoolgirl Eve Cogan from Sydney Australia organised a petition that promoted having the Canberra airport named after Dr Warren. At the time of this update (October 2014) such naming has not transpired.
Accident recorders have progressed a long way since the Dr Warren invention days. Australia became the first country to make the fitting of both CVR and FDR mandatory on large passenger aircraft. In other countries the requirement to fit CDRs occurred later than that for FDRs. Multi-track magnetic tape recorders soon overtook magnetic wire recorders. CVRs and FDRs fitted before the 1990s were always housed in separate boxes. With the advent of high storage capacity solid state memory recorders in the 1990s, the combination of the CVR and the FDR in the one box became feasible and the fitting of the combination, referred to as a CVFDR, was adopted for some aircraft. Although fairly rudimentary, the ARL Black Box was a CVFDR.
ARL Black Box References
Dr David Warren in 1962
Electronics team involved in the 1962 airborne and ground systems development - from left Lane Sear, Ken Fraser and Walter Boswell.
Ken Fraser working on ground station recovery in 1962
Oscillogram of total signal on wire and its separation on playback into speech and data components for 23-March-1962 flight
Chart printout of small portion of the 23-March-1962 flight with cockpit voice annotation added by Dr Warren
Chart printout of large portion of 23-March-1962 flight data recorded during the test flight and decoded by the ground station