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In the event of a plane crash such as MH17, and the flight data recorders (FDR, a.k.a. "black boxes") are potentially in the "wrong hands", is it theoretically possible to:

  1. open the FDR and close it again without leaving traces?
  2. alter or selectively erase data of the FDR?

In other words, can an FDR professionally be tampered with as opposed to purely destroyed for the purpose of hindering an investigation?

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Fortunately for MH17 case the CVR and FDR are not very important. There would be nothing unusual before the explosion and the explosion most likely stopped power and so the recording. Important proofs will be radar records observing the missile that USA officials already reported to have (mentioned on AvHerald), debris of the missile itself if the official investigators or OSCE observers manage to find any and traces on debris of the aircraft indicating the explosion happened outside. – Jan Hudec Jul 21 '14 at 8:33
I know it's conspiratorial, but what if the plane crashed due to malfunction and both sides are trying to use this unfortunate event as a pretext to other actions? – jnovacho Jul 21 '14 at 8:39
@jnovacho In that case the examination by investigators will have to find no fregments of anti-aircraft equipment and the remains of the fuselage will have to contain no signs of shrapnel or external damage where it cannot occur, e.g. if one of the engines disintegrated without external influence, the damage on the fuselage will indicate this by the way the debris or engine parts penetrated the structure. I am not sure if chemical traces would be on the fuselage. That's a question for the missile-experts. – SentryRaven Jul 21 '14 at 9:53
Dont know if this is true of current commercial planes, but I saw a recent air disaster documentary that stated that even after removing power the recorders will carry on recording for a few seconds. – Eno Jul 21 '14 at 20:03

Yes. Black boxes aren't designed to be tamper-resistant.

The hard part is not the physical act of tampering with a black box, it's constructing a coherent false narrative of what happened during the time period. The FDR records 80+ channels of data, which an investigator can correlate against each other, against data in the quick access recorder, against ACARS reports, and against the physical condition of the airplane itself.

For example, say you want to "prove" that an airplane's engines were shut down mid-flight, leading to a crash. You could modify the FDR's record to show a throttle setting of "closed" and an engine RPM of 0, but the exhaust temperature would still be high, the fuel tank levels would still be dropping, and analysis of damage to the turbine blades would show a mix of axial and circumferential bending around the entire circumference of the blade disk, rather than the pure axial bending on a single side that would be expected if the engines had stopped spinning.

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Do you know if there is at least a seal? Has there ever been a reported case where someone has tried to tamper with the FDR? – greener Jul 20 '14 at 23:11
What would stop someone from reflying a crashed flight in another plane and swapping out the FDRs? Not referring to MH17. – Danny Beckett Jul 21 '14 at 0:40
@DannyBeckett: The information recorded by the second FDR wouldn't match the information recorded by external systems such as ATC. It would be extraordinarily difficult to replicate all the conditions of the original flight. – Greg Hewgill Jul 21 '14 at 1:19
But Shirley a device designed to withstand hundreds of G shock, hundreds of degrees fires and submersion in hundreds of meters of water, should to a certain extent be more than a little difficult to disassemble, let alone reassemble. – Aron Jul 21 '14 at 10:36
I see what you did there. – CGCampbell Jul 21 '14 at 11:19

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