Flying and aviation stuff

...but, their engine/motor listening gear (which performs acoustic "finger-printing" sonic spectral analysis) CAN detect 37.5 kHz pinging.

 

duplicate post (this forum hangs when posting)

 

Really? How do you know this if I may ask? There IS a difference between sonic and ultrasonic. I don't think motors emit ultrasound.

Lessons from Flight 447
Undersea Search Operations:

http://www.ifremer.fr/web-com/sar2011/Presentations/SARWS2011_FERRANTE.pdf

 

..I wonder if there is something they can do...such as hang a mic out the torpedo tube.

 

I see you must be referring to this:

 

Having been the sonar officer on a US submarine, I will state clearly that statement is wrong.

 

Can a submarine pull a towed listening array without entangling the tow cable in its own prop?

 

It's possible that US submarines are much different from French/European submarines. Or, you are just saying that.

The European experts are pretty firm about uselessness of military submarines. Here is another reference on this:

http://www.azi.hr/docs/ACC_GuidelinesWeb[1].pdf

 

Your source isn't saying that subs can't hear 37.5 kHz. Just that those not equipped or have crew trained to do so aren't much help. SOme subs may not be able to hear it. Others probably can. Then there are the states that don't want it known what their sub can or cannot do.

 

Yes. A towed array is standard equipment on US attack submarines since the 1980's. Within a decade the Soviets were putting towed arrays on their latest classes. The towed array housing tube on US subs runs along the hull and then routes past the hull to the top of the starboard rear stabilizer fin (not the rudder fin). In the picture, it's the bump that runs along the starboard side. That keeps it quite separate from the prop. The core limitation is avoid putting the prop in reverse with the array deployed. The Soviets used a huge pod at the top of their upper rudder fin.

 

No. What I will say is that submarine acoustic capabilities (of any nation) is kept extremely secret, so open source literature or publications on the web is guaranteed to be more misleading then insightful. Providing a powerful acoustic detection capability is rather trivial if you know what frequency you are looking for and the emitter is wanting to be found. Physics is the limitation here, not submarine acoustic detection capabilities.

Any uselessness is far more likely due to delays deploying and supporting a rather slow moving diesel submarine to the far extremes of the search area. Additionally all submarines are national military assets not routinely available for short turnaround deployment. Most are either deployed, in overhaul or maintenance, or have other commitments. That's why they should be considered useless. It would be much better to just pick the most available ships already close or available and just put a big container with the transducers and audio range spectrum analyzers and a few experts. Coverage is the critical thing here and subs are not going to be able to provide much on a very short turnaround, if any.

 

Why worry about "declassified" information. Use physics. It's much like the calculation of the operational depth of a submarine. Take the hull diameter, the thickness of the steel, and the yield strength and you get the max depth. All that is left is the safety factor each nation uses. For sonar, just start with the physical dimensions of the transducers or transducer array. For a reporter, these parameters are mysterious numbers. For an engineer, they are known to the extent the source assumptions are valid.

It has been thought about. With many millions of sonobouys made for the Navy, a lot of technical issues have been solved. The issues revolve much more around who pays for this and why do we need to pay for it. That does not mean it's a good idea, but even good concepts have to be powered through extremely old school international aviation regulatory agencies. Without a strong champion, most stuff like this flounders. This might be the case that creates a champion.

 

At one time I had been aware of some of the props being quite large, with secret blade shapes requiring covers in port. Before that, I'd heard about very long wire VLF antennas that could be deployed behind the boats to receive signals from the Jim Creek transmitter, not far from where I used to work (and coincidentally, close to the recent Washington State landslide), and another transmitter in Michigan. But I didn't know if towed arrays fit.

Your answer also explains that weird looking bulb on the Soviet rudders.

 

That depends. If it's a GEC Marconi submarine, when calculating the hull's ability to withstand pressure, you should also factor in the question of whether the front section of the hull was welded on (a) the right way up or (b) upside down.

Apparently.

 

No, the quoted uselessness is based on the actual French experience with their own nuclear submarine searching for AF447.

Air France Flight 447 - Wikipedia, the free encyclopedia

 

One shouldn't state that a technology is useless based on a failed first attempt.

The French SSN (Émeraude) was initially built as more of an ASuW platform than a true SSN when the first four of that class (Rubis) was built in the late 90s.
However (comma!) she was/is equipped with a towed array sonar and she should have been able to locate the CVR/FDR pinger, if indeed it was pinging at the time.
There isn't anything magic about ultrasonic pings. Torpedoes use ultrasonic pingers (I've been told) so it's really REALLY advantageous for a boat that's underwater, underway to be able to detect signals in that range.

The recorders from AF447 were found as stated in the referenced article but only after the debris field was located the following year.

With all due respect to the T-AGOS ships, I'm a little skeptical of the superiority of collecting sound data from the surface.
It's noisy and rough up there!!

Submarines are equiped with BST buoys that will deploy automatically if the hull reaches collapse depth, or if the crew forgets to hand wind a mechanical timer...and after a series of very VERY loud alarms.
AN/BST-1A - United States Nuclear Forces
It's pretty clear that we're going to get a reboot on the FDR/CVR locator pingers. If they're only effective for a 5NM range, and you're trying to find one in an ocean that's 2NM deep, you're pretty much setting yourself up for failure, and it isn't going to take very many multinational searches costing hundreds of millions of dollars before somebody drags commercial aviation kicking and screaming into the 21st century.

 

That seems a little one sided. EVERYTHING was useless during that search phase; subs, ships, aircraft, psychics, etc. for about two years.

 

A couple of points worth making in the overall search effort
1) Most Towed arrays (sub or surface) are working in a frequency range not likely to encompass ultrasonic pings.
2) A "VLF Floating antenna" is a completely different and independent system from the sonar towed array.
3) The T-AGOs towed arrays are extremely far from the towing ship, so self noise is not an issue.

The idea of the floating antenna was to be able to listen with stealth. I found out on one watch that seagulls are fantastic floating antenna detectors. Looking through the periscope aft of the sub, I see about 10 seagulls sitting in a row moving sideways through the ocean at a couple of knots following me. So much for stealth. If you see a line of seagulls moving sideways anywhere in the ocean....it is not magic.

 

We didn't always use a floating wire antenna...
Boomers also carry a communications buoy that serves the same purpose....but again, this is communications and not Sonar.
Interestingly enough...there is a long floating wire pigtail on the buoy that seagulls like to hang out on if the boat is moving slowly enough (boomers do) and if the wire is close enough to the surface (often it is.)
The one pictured below is several generations old, and it looks a lot more menacing than the newer ones.
We used to tell the tender pukes that it was a self destruct device....or the skipper's escape capsule.


I just caught a squib on the hourly news that the Aussies are sending a boat in to sniff for the pinger(s) although once they localize the debris field, a side-scan sonar would probably be more useful.
I'm guessing that whoever was in the front office of the 777 might have ditched the aircraft to lessen the surface debris.
If he (or she) did it right, then the aircraft's hull might be largely intact and much more difficult to localize in 13 kilofeet of water out in the middle of nowhere.

We'll find out....
One way or another.
I'm very sorry for the pax and crew, but my primary concern is locating the plane so that we don't have to worry bout somebody lawn-darting it into a city somewhere.
Eight figure lawsuits are reason enough, but THAT is far and away what will REALLY drive this recovery mission.

Then????
CNN will have to go back to covering trials and twisting politics.