Malaysian Airlines MH370 contact lost

[Coagie]

Slip and turn

Coagie makes a good point. If you are seriously interested in effective research I recommend learning a few quick-win effective research techniques so you don't have to bash fellow PPRuNers for their sources! E.g. start with Google and a few well chosen search words like AF447 acoustic locator sonar frequency.

Then in seconds you might easily stumble over stuff like:
BEA to examine why acoustic sweep missed AF447 recorders - 5/5/2011 - Flight Global
https://fenix.tecnico.ulisboa.pt/dow...issertacao.pdf

Thanks, Slip and turn.

I have to correct myself. I kept writing 43khz, but I meant 37.5khz, for the frequency of the pinger. Anyway, here's a quote from Slip and turn's first link:

While a nuclear submarine was enlisted to assist the search, its sonar interceptor was not originally designed to pick up the 37.5kHz beacon signal. Lower-frequency transmissions, around 8.5-9.5kHz, would have improved the chances, says the BEA. But improved sensor settings enabled the maximum distance for detection to increase from 2,000m to 3,200m during the last 10 days of the acoustic search.

Anyway, the "not originally designed" part is what popped into my head from the very first I heard of the French sending the Nuclear sub to try and hear the pinger. Running the signal through a heterodyne circuit, where they listened only for 37.5khz, would have helped tremendously. That's pretty much what the purpose built listening for pinger equipment does. The sub didn't have equipment purpose built or modified to listen for 37.5khz pingers.
I haven't yet read the dissertation, that the other link connects to, but wouldn't be surprised if it should be a "must read" for anyone thinking of locating a, downed in the water, airliner pinger.

YRP

If you are ignorant of communications engineering (which is ultimately what signal detection is), easy to say they screwed it up the first time...

YRP, The Albert Michelson Interference Theory is actually some of the only stuff I'm good at! I'm apologize if I've changed your whole paradigm on believing that authorities are infallible, and it makes you feel uncomfortable, but, in truth, a little cynicism and experience is a good thing!
If the sub had the equipment mods it needed, AF447 may have been found 2 years earlier. Since it didn't, the area should have been searched by vessels with purpose built equipment, instead of being checked off the "Areas Already Searched" list. YRB, A physics course could help you a lot. I'm sure there are some good, as well as interesting, ones online. I had to learn mine in the olden days, where it was a bit dry. Anyway, good luck, and hope you're melancholy goes away.