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Plane Crash Diaries

Episode 19 - Cockpit Voice Recorders (CVR) and Flight Data Recorders (FDR)

Plane Crash Diaries
Plane Crash Diaries
It was Australia that initiated the mandatory installation of cockpit voice recorders after an accident in 1960, while we’ll also probe a mid-air collision involving United Airlines and Trans World Airlines aircraft over New York in the same year. That led investigators to call for more information when accidents were being analysed.

So let’s find out more about how these two crucial bits of tech ended up in all commercial aeroplanes and helicopters.

The flight data recorder or (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 in a single unit. Together, the FDR and CVR objectively document the aircraft's flight history, which may assist in any later investigation if there is an accident.

They are built tough – capable of withstanding in impact of 3400 Gs and temperatures of over 1000 degrees centigrade. As I explained in the episode analysing the disappearance of MH370 there are now moves to have live streaming of data to the ground and an agreement to increase the battery life when a plane ends up lost over the ocean.

The first example of a Flight Data Recorder is actually pretty old, dating back to 1939 when Frenchman Franscois Hussenot built something called the TYPE HB flight recorder. IN his machine, photographic film was used which scrolled along recording the main flight information such as speed, altitude and position.

Another form of Flight Data Recorder was developed in the UK during the Second World War when Len Harrison and Vic Husband built a sturdy device that could withstand a crash and a fire and keep the data intact. In this case, they used copper foil as a recording system – a bit like the early phonographic recordings.

But it took a Finnish engineer by the name of Veijo Hietala to introduce his black box called Mata Hari in 1942. She was a famous spy during the first world war, naturally his machine collected intel in a way. This box was used in Fighter aircraft test production.

Voice recorders were first tried by the United States also during the Second World War. In August 1943 the United States Airforce use magnetic wire to capture the inter-phone conversations on board a B-17 bomber crew flying a mission over Nazi-occupied France. The broadcast was then fed back to the US by radio two days later.

So the idea was nothing new and yet aviation authorities did not move on the concept for another two decades after the Second World war. That’s despite a number of commercial aircraft going missing. Indulge me as I go through a list.
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