Originally Posted by
davejb
...an ASW aircraft that does not wish to risk being detected acoustically will fly most of the time at (say) 10,000 ft to maximise it's ability to pick up the signals from widely dispersed buoy patterns, which will be high enough to avoid acoustic detection (although it wouldn't surprise me to find somebody once managed it).
Yup. 1977. P3 out of Kef, on topped the previous aircraft barrier and blotted out each buoy he on topped. He was at 20k, the buoys were probably deep.
* I doubt you'll get 737's crossing the Atlantic, by the way, so I'd have thought that P8's would fail to benefit from any conceivable camouflage effect...they'll be the only version of the 737 out over the oggin.
The camouflage would come from the engines not the airframe and Atlantic is of course only one pond. Perhaps more signifcant for 'not an airliner' is, as stated the height of the aircraft (engines) and hence audio strength. Also a transiting civil air liner will go doppler high/doppler low/no contact. An MPA will return and repeat the noise sequence at power settings that will be variable and different from a cruising airframe.
The lower the aircaft flies the more energy will pass into the water. All you then require is a microphone (submarine sonar array
which means that the aircraft detection may be some considerable distance from the submarine.
, or sonobuoy) that is sensitive enough to detect the noise.
which could even be one's own sonobuoys.
There is no resaon why a submarine cannot detect sonobuoy transmissions to the MPA albeit over a very limited range. There was a case of a Canadian O-boat that surfaced, located each sonobouy and switched them off to the puzzlement of the MPA.
how many blades are fitted to the shaft. If you recognise the signature as belonging to a specific class then the blade count can be simply converted to tell you how fast the ship is going.
And if the blades are damaged, as could happen with passage through an ice field, could enable an individual unit to be identified.
A sensor operator can reas acoustics like a book.