Today's press conference on the loss of the AF447 Air France Airbus A330-200 showed the importance of black boxes in any major fatal crash investigation.
Spokespeople for BEA, the French air accident investigators, were at the conference to report their interim findings. They didn't know what had happened to the Airbus, or have any idea what happened.
Yet more is known about the performance of the Airbus in its last minutes than is known about Chinook ZD576.
The Airbus, flying over the Atlantic off Brazil, sent 24 maintenance data messages to Airbus Industries in France in the minutes before the links were lost. The messages, according to the investigators, show that the pilots were getting conflicting information on their air speed, possibly because blocked pitot tubes.
The BEA says that the pitot tubes are a suspected factor in the chain of events but not the cause which may never be known.
If French investigators are so uncertain about the probable cause of a major fatal crash because they don't have the black boxes, how is it that some believe they can be certain about the cause of the crash of ZD576 when there weren't any black boxes?
The uncertainties over the crash of ZD576 run deeper because it did not transmit any real-time messages about its performance in the minutes before it crashed.
Some of the Airbus 330-200 has been recovered and some of ZD576 too. Many people have tried to draw conclusions from what was left of ZD576 but that is speculation without a CVR or FDR.
The air marshals derived conclusions from the TANS. But the information recovered from the TANS was not independently verified, and indeed was extracted without independent supervision. It was not intended as a black box, so the manufacturer had to devise its own routines to extract data from it. The integrity of those routines has not been checked independently.
So it’s difficult to see how any information from the TANS could be taken as verified fact; and it's worth nothing that the AAIB did not rely on TANS data in its report.
French investigators are determined to find the black boxes by different methods if the current ones fail. They say that without them they may never know why AF447 crashed.
Would they change their minds if told about ZD576? That it was possible reconstruct the last moments of flight without black boxes, when large parts of the aircraft have been destroyed, when the AAIB has been limited by the RAF to investigating only some aspects of the crash, and when there have been no maintenance data links?
The French investigators would probably say that they would like to carry on their search for the black boxes. So anxious are they to find them that a nuclear sub is involved in the search, as is the US Navy.
As for the cause of the crash of Chinook ZD576, who needs black boxes when, as far as the MoD and its ministers are concerned, speculation can serve as irrefutable fact?