Malaysian Airlines MH370 contact lost

[BJ-ENG]

Yes, Water landings are hard too!

To add to the many suggestions attempting to ponder the question regarding a water landing for any aircraft, and particularly a large wide body aircraft like a 777, it is worth pointing out some of the differences between ground and water impacts, much of which was covered in the AF447 thread.

When considering relatively slow speed aircraft impacts, water impacts vary from those on hard terrain in the following way. During an impact with rigid ground, the undercarriage, if deployed, absorbs a significant portion of the impact energy, with the remainder being transferred to the stiffest structural members such as the energy absorbing subfloor beams. These are generally designed to progressively collapse in order to limit to G load on the occupants. The key thing to think about here is “progressively collapse”. To give an example, drop tests on passenger sized airframes at NASA Langley Research Centre have shown how the cabin section experiences quite a pronounced deformation even for a 10m/s drop. The section progressively collapsed, as designed, and but remained intact.

For a water impact, the loading mechanisms differ significantly. The landing gear is unable to absorb the impact energy and instead the impact loads are distributed as a transient dynamic pressure load over the fuselage skin. This initial absorption by the skin momentarily slows the rate that force is applied to the structural members, and has the effect of inhibiting the buckling process to the extent that energy absorbing subfloor components become ineffective. This is why Navy helicopters are designed with additional features to improve their crashworthy response over both hard terrain and water.

In addition to the previous mechanism, the structure also experiences considerable hydraulic shock as the aircraft skin is penetrated and fluid is forced into the interior allowing large pressure forces to act directly upon the cabin floor and interior bulkheads, and as a consequence, actually increases the damage. The result is that vertical accelerations experienced by the occupants is higher due to the lack of initial buckling and rogressive collapse, compounded by the hydraulic shock effect on flooring.

In the Hudson river Airbus ditching on a smooth surface, the evidence for significant hydraulic surge is evident as can be seen from the damaged to the fuselage underside and the dislodged rear bulkhead.

http://graphics8.nytimes.com/package...9/original.pdf


http://www.aero-farm.com/museum/pa-ditch.jpg


How ditching should be done - Learmount

[tail wheel]

One of the more accurate media comments:

[Vinnie Boombatz]

@hamster3null (#8555, 28 Mar 2014, 02:13)

Excellent spreadsheet!

The problem is made harder by having two sources of Doppler -- aircraft motion and satellite motion.

Even for a stationary satellite, the problem is still hard because of the unknown aircraft velocity vector orientation.

So all one can do is hypothesize a set of aircraft positions and velocities, and look for a decent fit to the measurements.

INMARSAT or AAIB must have done something quite similar.

[olasek]

And yes, the Australian government *ARE* going to get the bill for all the wear and tear, jet fuel, etc..

For their own aircraft/ships, etc, I suspect every participating country is paying their own expenses.

[500N]

The base cost for the military and the military aircraft is the same whether used on the search or not.

[Orestes]

BJ-ENG:

Interesting to note that in the Hudson River Airbus ditching, the NTSB report states that although the CVR remained in the plane and was physically undamaged, its underwater locating beacon (ULB) was tested and found to be non-functional.

[ana1936]

Former Australian Defence chief Angus Houston to help coordinate search for missing plane

Malaysia Airlines flight MH370: former Defence chief Angus Houston to help coordinate search for missing plane - ABC News (Australian Broadcasting Corporation)

[etudiant]

"Commodore Peter Leavy, the overall military commander of the search effort, said: ''This is a very, very big operation … Normally a military exercise involving different nations is the result of a lot of planning. Something like this … we had to come together very quickly and just get on with the job.''

This is a sign that the search is nearing its final stage.
To coordinate any kind of large, multinational effort, there needs to be a boss. He can allocate the resources and make the tough decisions, such as when to call it quits.
The reality is that nothing is being found and the odds are declining.

Only a boss can call a halt to an obviously futile effort without anyone losing face.

[777fly]

Olasek:
Then you don't know the B777 in alternate nav. All radios have to be tuned in alternate radio mode, no needles or ILS otherwise. There is no situational guidance unless you programme it in, its not a question of following the magenta line, its simply needing to know where you are. Looking out of the window at night is not enough.
I'm talking about a back up mode, not normal nav.

[Porrohman]

Ambient Sheep. If it was a criminal act then misdirection could have been an important part of their plan. By manipulating the response to the satellite pings, the aircraft could have flown west whilst giving the search teams the impression that it was flying north or south.

Buttmonkey1; the existence of the pings might not have been widely known amongst the aircrew community but it will have been part of a specification and I would be surprised if that specification is secret. I would accept that this would require some detailed technical knowledge but I expect that this information was in the public domain, albeit not widely known.

[oldoberon]

Skynews showing a graphic of the fdr/cvr as one unit, a cylindrical one mounted on a L shaped one, and 1 beacon, I always thought they were separate and two beacons, twice the chance of finding something.

Are they wrong or is the 777 a combined unit.?

[training wheels]

Originally Posted by parabellum

Forget all about LNAV in the immediate aftermath of a serious problem, it will be FLCH and HDG Select, bring up ARPT display and head for nearest suitable. Pumping in Lat and Long would be unnecessary and both time and attention consuming, maybe revert to LNAV when everything is under control but if it is an immediate landing even that is unlikely.

Yes, agreed. Actually if you look at the track that they were on at the time on airways R208 from IKUKO to IGARI, it has a reciprocal track of 197 deg M. Assuming they wanted to return to Kuala Lumpur immediately, could they have set a heading of 197 initially and for whatever reason, the aircraft wondered further to the west, possibly with a DIRECT TO WMKL (Langkawi) set in the FMC? Once having passed WMKL with no further waypoints to track to, could LNAV then later have disconnected due to flight track discontinuity and then reverted to HDG select with the original 197 Heading that was selected?

If so, this matches the heading of 197 deg M and associated track that Capt Kremin was suggesting in his post 7539 of where the aircraft may have ended up.

[vapilot2004]

Originally Posted by oldoberon

Skynews showing a graphic of the fdr/cvr as one unit, a cylindrical one mounted on a L shaped one, and 1 beacon, I always thought they were separate and two beacons, twice the chance of finding something.

Are they wrong or is the 777 a combined unit.?

2 separate boxes, although they are located side by side. There is a CVR and a DFDR. Both are equipped with a ULB (beacon.)

[nnc0]

IMHO money should be spent on the decades-old detachable ELTs rather than
lower frequency pingers on the FDR if you can only do one thing. We are all
looking something going BEEP-BEEP with our ears in an area nearly the size of
Australia right now. The 406 MHz signal wouldn't find the needle, but it would
find the haystack

Absolutely! Something is very wrong that in this age of satellites, cpdlc, etc, we still lose track of airplanes. What if there had been survivors from this crash or AF? They'd have perished waiting for rescue. What if there was a aircraft issue or a handling/maint issue that leaves other aircraft in danger. We need those black boxes! We sent rovers to deliberately crash on mars and survive. Surely we can build a better ELT that is cheap, rugged and effective and spares us all the time, effort, money and heartbreak running around blindly.

[ferry pilot]

The airplane left a major airport with a competent crew, no known deficiencies and the best navigation and communication equipment available. It apparently ended up in the least accessible area it could reach with the fuel on board, and there is still debate about the possibility it did this without deliberate action on the part of a pilot. It keeps the story alive, but needs more imagination than fact, of which there is an unlimited supply of the former but very little of the latter, which only points in one direction. Somebody put this airplane wherever it is, and knew what he was doing.

[sardak]

oldoberon-
Two separate boxes. Here is a link to the photo of the Asiana 777 CVR and DFDR next to each other in the NTSB lab. They look similar but note the size difference of the "box," while the cylinder with the memory cards and ULB appear to be identical https://twitter.com/NTSB/status/353891249230585856

[hamster3null]

Originally Posted by ferry pilot

It apparently ended up in the least accessible area it could reach with the fuel on board

I'd dispute this conclusion.

If you take a map and draw a circle with the radius of 2500 nm centered in Kuala Lumpur, at least a third of the circle would be comparable to the current search area in terms of inaccessibility. One could even ditch it in the Mariana Trench (and good luck retrieving the wreckage from the depth of 36,000'...)

Inaccessible areas don't have to be in the ocean, either: ASN Aircraft accident Antonov 12BP BL534 Dhaka Glacier

[Coagie]

Decreasing the ULB transmitted signal’s frequency. The attenuation losses induced by the Underwater Acoustic Channel (UAC) are highly dependent on frequency, and increase proportionally to its cube. Hence, reducing the current 37.5 kHz to a reasonable 10 kHz has the potential to greatly enhance the maximum depth and range for which the ULB signal can be detected. The downside of this solution is that the physical size of the beacon would have to increase

Just like on your stereo speakers, the tweeter handles the high frequencies and is physically smaller than the woofer that handles the lower frequencies. The physical size is certainly a factor, but I don't think it's a show stopper. You would also need a larger battery to handle the larger power needs of the lower frequency, but maybe, like was suggested in an earlier post, it could make up for some of the added power consumption by not sounding off as often.

[Flybrat]

On “good” authority we became aware early on the plan was for the captain to fly MH370 to Mongolia.


This would be close to the reciprocal of the heading of 197 deg M that Capt Kremin was suggesting in his post 7539.

[ferry pilot]

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