Asked by: Byron Williams, Wales
Modern flight recorders store up to 25 hours of data in a continuous loop. They monitor at least 88 parameters such as cockpit control settings, information about the engine and the time. The voice recorder also continuously records sounds in the cockpit. While all this information could be transmitted live to the Cloud, there is no guarantee that this will always work, especially during those critical seconds of a disaster. Wireless transmissions are also susceptible to electrical storm interference, jamming or fraud. For this reason, black boxes are self-contained, fireproof, shockproof and waterproof, with their own internal battery that allows them to keep working even if the plane is destroyed.
Subscribe to BBC Focus magazine for fascinating new Q&As every month and follow @sciencefocusQA on Twitter for your daily dose of fun science facts.