Why is the beacon only good for 30 days? Why not longer?
Well, it’s controlled by a battery within the box itself. If you want a longer-lasting beacon you’d have to build in a bigger battery. 30 days is a reasonable length of time for most purposes so that’s what they designed for.
Well yeah, generally when a plane crashes nowadays they have a pretty good idea where it went down so the search already knows where to look. Plus, the majority of crashes are on approach or take-off, hence relatively shallow water. I mean, how likely is it that a modern aircraft would fly on for hours with no radar tracking it, no contact from the flight crew, and no idea of their heading or location?
Despite the fact that you’ve seen multiple airliners go missing in 2014, the fact is that such incidents are incredibly rare.
According to the ICAO’s 2014 report, there were about 32.1 million commercial passenger flights in 2013 and the number of crashes that resulted in any fatalities was only nine. Yes, 9 fatal crashes out of 32,100,000 flights. That’s 0.000028%. And every single one of them occurred within a few miles of an airport, usually while attempting to land. Finding the black boxes was just a matter of sifting through the wreckage. In 2013, the number of missing airliners where they had to comb the ocean day after day looking for traces of the wreckage so they could find the black box, hoping they could find it before the battery ran down, was zero.
So, the answer is, “Money”. Its always money.
Or, the answer is “30 days is a reasonable design goal.”
Not to mention nobody is going to suggest changing to Lithium-Ion batteries for FDR being that they’re considering banning them from passenger airliners completely!
No. The cost of the battery is essentially zero compared to the rest of the system. The device will have been designed to meet the requirements in the technical standard demanded by the FAA: TSO-C121. This required 30 days. That was what the FAA felt was a sensible time.
The FAA changed their mind in late 2011, after the Air France accident, and the new spec calls for 90 days. But this only applies to new locators. There is no requirement to retrofit existing planes.
Small batteries in home security devices last for years. So, the issue seems to be the power requirement to output the beacon’s signal. Can that be improved? We are detecting (admittedly with very special receivers) signals from spacecraft that originate from outside the solar system.
Here are the capabilities of the current Black Box.
there is a big difference between sending an acoustic signal through water at great depth and a radio signal through space.
The big trick with detecting signals from our various space probes is that we know exactly where they are. Typically to insane precision. Thus we can bring into play very large antennas with extraordinarily narrow beam widths (high gain). When we have no idea where something is we have to use a detector with a wide angle of view, and that necessarily means low gain.
Also the signal to noise in the oceans is awful. Both detecting spacecraft signal and pinger signals requires some reasonable amount of signal processing to lift the signal from the noise. Something that really bothers me about the design of the ULBs is that the signal is so poorly thought out. It should be absolutely unique, to reduce false positives, and should have had a high precision multi-tone signature that could have been used to allow design of a matched filter set to really allow signal processing systems to dig the signal out.