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23 March 2005
23. March 2005 Commercial Aircraft



Interview with Dr. David Warren, inventor of the Black Box

In 1934, the Miss Hobart, a Holyman Airlines new, four-engine, DH86, crashed without a trace in Bass Strait (separating Australia's mainland from the island state of Tasmania). It was Australia's first major air accident involving a civil aircraft and Dr David Warren's father was one of those who died. The last thing he did for his nine-year-old son was to give him a crystal set (a small, simple-design radio that operated without batteries) to take to boarding school. This sparked the boy's interest in things technological, electrical and scientific, so when the family moved to Sydney, he took up radio as a hobby.

Most inventors have a moment of insight or clarity when their idea takes a definite form. When did that moment occur to you?

Yes, that's true. It occurred to me after I was invited to join a "think-tank", or technical committee, set up to investigate the De Havilland Comet crashes in 1953 and 1954. By that time I was working in the Defence Department's Aeronautical Research Laboratories (ARL) specialising in fuels, and as Australia was one of the countries planning to acquire Comets my task was to look into the possibility of a fuel tank explosion being the cause of the disasters. As there were no surviving witnesses, passengers or crew, to tell what had happened, the accidents were a major obstacle to the future development of commercial jet travel.

While I knew a bit about fuels, I knew very little about aircraft structures, crew operating procedures and the like. But as I sat through those long committee sessions I found myself thinking about something I had seen recently at Australia's first post-war Trade Fair, a Miniphon Portable Wire Recorder from Germany. It was the world's first miniaturised voice-recorder, and I began to imagine a businessman on his way to London using the recorder to dictate a letter for his secretary to type when he arrived. And then the penny dropped, the realisation that not only would the device record the businessman's words, but also the sound of anything else that happened on board, be it the demands of a hijacker, or an explosion. While the investigators might have found it difficult to trace the cause of a crash, I thought there was a good chance that the flight crew might have known, and it might well be revealed in their conversations in trying to deal with the emergency.

So I interrupted the committee's discussions and said: "Hey, what about something like this", and told them of my idea. The Chairman replied: "That's a good suggestion Dave, but now's not the time to bring it up. We are here to discuss what did happen, not what you wish had happened".

So initially, your idea was greeted with little interest from the aviation and scientific community. Why were you so convinced of the need for it when others were not?

Well. I continued to talk about it and most of the younger scientists at the ARL thought it was a good idea and urged me to do something about it. However, the older men took a more cautious view, their attitude being that if it was any good it would have been done already, and by an American, not an Australian. In 1954 I outlined my ideas in a report entitled "A Device for Assisting Investigation into Aircraft Accidents", which was circulated widely to aviation authorities and the aircraft industry. There was still little interest. But I kept at it because the idea of a voice recorder in an aircraft cockpit seemed so simple that I couldn't understand why it wasn't taken up, and that's the force that kept driving me.

Why do you think there was that disinterest, given that we are talking about something that was destined to play a huge role in international aviation safety in the future?

I think the reason for the lack of interest in Australia was because we had not experienced a major aircraft accident for many years and, in fact, were regarded as having the best aviation safety record in the world at that time. The general feeling seemed to be "we don't have accidents any more".

About this time I decided that maybe a "show and tell" approach would be more effective than simply a "tell" approach, and obviously a demonstration unit was needed. So, in 1958, with the help of some colleagues, I set out to design the prototype of what we called a "Flight Memory Unit". But because I worked in a government institution and couldn't spend any time or money on something that wasn't an officially approved project, I had to work at home where I refined and perfected the design. After successfully testing it in the air, we formally requested that the various aviation authorities officially assess it, but the response was discouraging and the Australian Aeronautical Research Council recommended that no action be taken.

Can you describe the breakthrough moment in 1958 when you explained your idea to Sir Robert Hardingham? What was the immediate outcome of this meeting?

I was working at my desk one day when my Chief Superintendent, in company with another man, walked up and said "Dave, I would like you to meet a friend of mine from England, tell him about your recorder idea". I didn't know it at the time but Air Vice-Marshall Sir Robert Hardingham was Secretary of the UK Air Registration Board. I described the workings of the flight recorder and he was instantly enthusiastic. He turned to my boss and said "I say old chap, that's a damn good idea, we'd better get this young lad on the next courier flight to London". I thought he was mad. Then my boss turned to me and said "Well come on, don't just stand there Dave, go and get your passport ready." I thought he was mad too!

But I went to London on a courier bomber and the response to the demonstrations in the UK was very encouraging. The BBC featured the recorder on television and radio, UK manufacturers offered developmental support and the British civil aviation authority began to move to make flight recorders mandatory on all British civil aircraft.

Modern flight recorders are able to store a wealth of information. Looking back, can you remember your first prototype model? The prototype measured about 18 x 8 x 6cm and was designed and built using steel wire as the recording medium. It was fully automatic for fit-and-forget operation with a "memory" mechanism that could store four hours of pilot voice and instrument readings at the rate of eight per second up to the moment of an accident, but would automatically erase older records for the wire to be re-used. It is now on display in the Science Museum in Melbourne.

Can you briefly describe the significant events in the development history of the black box and your involvement from the first prototype through to commercial release?

After I came back from the U.K., because of all of the interest they showed over there, the Aeronautical Research Laboratories in Melbourne gave me a team of four technicians to update the prototype to a more efficient pre-production standard. We improved it in a number of ways, including a method of recording instrument readings with greater accuracy and at an increased rate of 24 readings per second. The recording mechanism was housed in a separate crash-and-fire-proof container mounted in the tail of the aircraft. While we were working on this, a British company, S. Davall & Son, had acquired the production rights from the ARL and developed a crash recorder for the British and overseas markets.

What are your feelings today as you reflect on your invention and the contribution it has made to aviation safety? What makes you most proud?

Well, obviously I'm very proud and pleased that one of the many ideas that I was paid to have over the years was worth the time and effort that went into it, and has paid off in terms of the research and development involved. While it's impossible to predict how many aircraft and lives have been saved, it certainly has been accepted universally as being a major contributor to the enhancement of air safety. And I'm also very happy that Australia has at last got the recognition that the idea was developed in this country and that Australia was, in fact, the first country to make cockpit voice recording mandatory.

(Footnote: While the UK and other countries had earlier adopted the practice of recording flight instrument data, progress in Australia had to wait until the unexplained crash of a Fokker Friendship at Mackay, Queensland, in 1960. The judge inquiring into the crash, when told of the existence of Dr. Warren's flight recorder, ordered that all Australian registered airliners should carry recorders for pilot speech as from January 1963. Although Dr. Warren's machine was offered as an immediately available system, the authorities commissioned an American company, United Data Control (UDC) to develop a cockpit recorder to meet the Australian requirement, reasoning that the local industry lacked the expertise. However, UDC chose to use magnetic tape rather than wire as the recording medium and developmental problems arose resulting in delays, so that when Australia's next major air accident occurred at Winton, Queensland, in 1966, recorders had still not been fitted. Questions were asked at the Winton inquiry about the failure to comply with the 1960 judicial requirement. Finally, in 1967, Australia became the first country to make both flight data and cockpit voice recording mandatory.

Today, voice-plus-data recording is now mandatory for all major civil aircraft throughout the world and has proved to be of inestimable value in finding the causes of a many aircraft accidents, just as Dr. Warren had predicted. However, he gained no financial advantage from his invention).

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