With the news that the Malaysian authorities announced that Malaysian Airlines flight MH370 ended in the Southern Indian Ocean, and the US Navy is sending a “pinger locator” there to look for the black boxes, we need to raise some caution about assumptions that these will reveal all there is to know about what happened on the flight.
The flight data recorder (FDR) and cockpit voice recorder (CVR) are located in the rear of the airplane, inaccessible to the cockpit or cabin, a Boeing 777 instructor tells us. Unlike the Boeing 737 in which a rogue pilot turned off these devices before plunging the airplane in a suicide dive, the 777′s FDR and CVR power controls are only accessible in the electronics bay and the access is through a floor panel outside the cockpit, in the cabin of the aircraft.
Assuming the FDR and CVR, therefore, were operational right up until the time of the crash of the airplane, there should be data recoverable if these units are eventually found. The FDR, being digital, has a 24 hour capacity and should provide a wealth of information. The CVR has only a two hour capacity and may yield much less, however. Clearly, it won’t reveal anything that happened over the Gulf of Thailand—this will have been overwritten by the end of MH370. But whether there is anything to be revealed on the last two hours for the flight is going to be uncertain.
In the US, by law the cockpit conversations recordings are only in 30 minute increments-the most recent 30 minutes. If this practice is true for other countries, including Malaysia, anything said in the cockpit as to what transpired when the plane originally was “lost” while still over the Gulf of Thailand will be lost to history. But the final 30 minutes of cockpit conversation, and any noise from the cabin within “earshot” of the cockpit microphones, should be retained on the CVR. But also in the US, pilots have the ability to erase the CVR once at the gate—and it’s certainly possible this occurred before MH370 went into the ocean.
Given the success, albeit two years after the crash, investigators had in recovering the FDR and CVR of Air France Flight 447 (the one that crashed into the South Atlantic in 2009, with main wreck recovered from around 12,000 ft), we feel reasonably confident MH370 will eventually be found and the recorders recovered. But manage your expectations about what might be found on the recorders.