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Old 8th Apr 2014, 13:30   #9581 (permalink)
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For all the intelligent discourse earlier in this thread regarding Doppler effects of electromagnetic waves, the mention of Doppler with respect to sound waves is curiously missing even though the effect is far more pronounced. The odds of getting precisely a 37.5 kHz return in an extremely noisy ocean are pretty low, at any considerable distance from the source.
Right, it wasn't exactly 37.5 kHz. It was 33.2kHz. They believe this is still indicative of the pingers, as the AF447 was transmitting at ~34kHz. But the cadence/interval of both pings (1Hz) did match, that's why they believe it is a legit detection.

re the Chinese RIB, I believe that was a handheld detector. (the kind the Chinese have is designed for shallow water/handheld use e.g. by a diver)
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Old 8th Apr 2014, 14:41   #9582 (permalink)
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On the B777 does the RAT automatically deploy with a loss of both generators?
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Old 8th Apr 2014, 14:43   #9583 (permalink)
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I think a Trent engine windmilling will keep a genny on line, providing the TAS remains reasonably high, so the partial ping will not necessarily coincide with fuel exhaustion time.
Nope, not even close. IDG and VSCF will drop off line at ~50% N3, windmill N3 is around 15-20% even at a high airspeed. At 20% N3, the FADEC will still be powered and there will be some hydraulic pressure from the pump (although not enough to control the airplane - that's why there is a RAT), but that's about it.
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Old 8th Apr 2014, 14:48   #9584 (permalink)
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On the B777 does the RAT automatically deploy with a loss of both generators?
Yep, automatic if both engines fail, with a manual override 'just in case'. IIRC, it'll also automatically try to start the APU, but if the fuel is exhausted that won't help...
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Old 8th Apr 2014, 15:06   #9585 (permalink)
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Lonewolf/RHAG, the answer to the problem, resolving differences, is a twin system. A ULB that remains with the airframe and a FLB (ELT) that is released on impact.

There appear to be two problems with the existing ELT - is it buoyant and does it have sufficient battery life?

As the ELT would help locate a crashed aircraft in the first vital 48 hours its short battery life was understandable. Even the existing short battery life should enable detection and localisation.

So, make the ELT ejectable and buoyant and give it the same black box capability of the ULB.
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Old 8th Apr 2014, 15:20   #9586 (permalink)
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Looking at AIS (marine traffic), there seems to be frequent if not a great amount of traffic in or near the search areas at any one time, not including the vessels involved in the current search. I assume this means that the area is fairly close to some designated shipping lanes. Would be interesting to have historical data as you can with FR24, just to see what was in the general area around the early morning of 8/3.
I'm sure that someone will remind me of the vast expanse of the area involved and the chances of a vessel being remotely close are slim, but you never know.

BTW I'm only talking about seeing or hearing something, not being involved in any way....
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Old 8th Apr 2014, 15:22   #9587 (permalink)
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Floating beacon and memory module

I thought I posted this earlier, but it appears to have evaporated in the ether. This HR Smith Group : (Technical Developments), Techtest Limited, Specmat Limited, Specmat outfit make just such a thing. I guess that the cost will be immoderate, but less so than the cost of the AF447 and current SAR efforts.
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Old 8th Apr 2014, 15:26   #9588 (permalink)
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How much difference would it make to locating an ULB if the pulse rate was lower, or perhaps 1 pulse every 10 seconds for, say, five pulses then one every second for a further five pulses. The aim being to extend the battery life. Or even making pulses less and less frequent after 5 days, then after 10 days and so on. Anything to make the battery last longer. The electronics to do this would be simple enough and would consume only very minimal power.

The people that wrote the specs probably never considered a situation like this - which is hardly surprising!

And why not a second ULB with a far longer interval at a low frequency to facilitate long range detection and rough position finding, then rely on the ultrasonic unit for precise location. It would need to have a long interval to make the battery last - low frequencies will require greater energy per pulse, but travel far greater distances. I suspect having one ULB operating at both low and ultrasonic frequencies would be rather too challenging, so on the KISS principle have two.

But that would of course not be necessary had the plane not been "lost" in the first place!
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Old 8th Apr 2014, 15:27   #9589 (permalink)
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Adding to things to improve detectability:

A floatable transponder, activated by g and/or seawater, that can be interrogated by search aircraft equipped with I band interrogators. Most military aircraft will have such interrogators for IFF (Mode2)

The transponder could be set inside part of the fuselage (wing root? tail area?) and be accompanied by a fluorescent dye marker. The panel could be released by g and/or seawater battery. Might de-icing be a problem here?

Having been winched out of survival dinghies many times in my aircrew career, I know how effective dye markers are. One idiot on my crew asked what does THIS do? while pointing the day end of a day/night flare INSIDE the dinghy. Needless to say he got wet. Had this been the Med, as opposed to the Moray Firth, we would have got wet to get the orange dye off. Instead the local pub was full of men who looked like we'd just been Tango'd!!!
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Old 8th Apr 2014, 15:36   #9590 (permalink)
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Originally Posted by Wader2 View Post
Lonewolf/RHAG, the answer to the problem, resolving differences, is a twin system. A ULB that remains with the airframe and a FLB (ELT) that is released on impact.
Makes sense to me. Getting industry and civil aviation regulating bodies to come to agreement ... ball's in your court! Best wishes.
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Old 8th Apr 2014, 15:50   #9591 (permalink)
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I doubt that both engines would have shut down simultaneously from fuel exhaustion. My experience (12,000 hours) has been that engines always burn fuel a little different, even when set in cruise to the same numbers. I can see a situation where one engine sucked air first, then the autopilot tried to maintain heading or track and altitude or speed, which resulted in a large yaw with roll angle followed by a spiral into the water. Not a long smooth glide as some have talked about here.

Yes, on the B-777 the APU will auto start with loss of both AC generators. Yes, the RAT will auto deploy with loss of both AC generators. Auto electrical load shedding occurs with loss of even one engine AC generator.
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Old 8th Apr 2014, 15:51   #9592 (permalink)
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Interestingly, I believe the frequency of the ping heard from Air France Flight 447 was 34kHz. I guess this may be due to battery aging?
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Old 8th Apr 2014, 15:59   #9593 (permalink)
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Search Strategy

Australian Air Chief Marshal Angus Houston announced on April 6 that the Australian vessel Ocean Shield detected two pingers in the water and showed a map displaying the location of the sighting as S21E104. The map also showed the location of the sighting by the Chinese vessel HaiXun01 as S25E101, and showed that the two sightings were about 600 km apart. A map supplied later by the Australian government showed the same two sightings as lying on an arc going from northeast to southwest that corresponded to “satellite handshake calculation number 7”, which was made from the Inmarsat satellite data corresponding to the last partial ping of flight MH370. The aircraft is believed to have gone down somewhere along this arc, with slower air speeds corresponding to locations further northeast, and faster air speeds corresponding to locations further southwest.
It is interesting that there is an air route that passes between these two points on its way to Perth, route L894, as determined by waypoints POLUM at S1959.95' E9832.91' and NINOB at S260.15' E10628.84. This air route happens to be the most southern of all air routes in the south Indian ocean and passes from northwest to southeast on its way to Perth. Is it possible that flight MH370 was on this air route just before ditching when its fuel ran out? If it had been flying by waypoints from POLUM to NINOB, this would have been consistent with using waypoints to fly from VAMPI to IGREX over the Andaman sea, and possibly also from IGARI to VAMPI to pass over the Malaysian peninsula. It would also have been consistent with using waypoints to fly around the Indonesian peninsula on its way south from IGREX to avoid Indonesian radar. If one assumes that MH370 used a waypoint like NISOK to avoid Indonesian radar on its way south from IGREX, then one can construct a flight plan consisting of the waypoints WMKK PIBOS GUNBO IKUKO IGARI VAMPI GIVAL MAPSO IGREX NISOK POLUM NINOB and determine how long it might take to get from Kuala Lumpur to the area between POLUM and NINOB. When you do this, you find that the flight time from Kuala Lumpur to NINOB is 7 hours and 52 minutes at 430 knots, which compares quite closely to the actual 7 hours and 54 minutes flight time determined by the 0:25 a.m. departure time and the 8:19 a.m. time of the last partial ping. Allowing for the possibility of additional waypoints between IGREX and NINOB would mean a longer flight distance, which would mean that the aircraft did not quite reach NINOB, but instead went down somewhere on the flight path between POLUM and NINOB. This, of course, assumes an airspeed of 430 knots. A faster air speed would have caused the plane to come down further southeast along the air route, and a slower air speed would have caused the plane to come down further northwest along the air route.

If one combines the Inmarsat data with the assumed flight path data, one gets two lines which intersect at nearly a 90 angle. The intersection point is almost exactly half way between the two ping sightings by the Chinese vessel HaiXun01 at S25E101 and the Ocean Shield at S21E104. This means that the most likely place where MH370 went down is approximately S234.24’ E10227.58’, which is the only point to lie on both the 40 arc and the L894 flight path. Given the short time remaining in the pinger lifetime, it would be well worth searching around this location.

Last edited by Double07; 8th Apr 2014 at 17:56. Reason: Better coordinates for intersection of 40 arc and L894 flight path
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Old 8th Apr 2014, 16:28   #9594 (permalink)
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Nine Lima, not much of a yaw at 300 kts or even 200 autopilot would easily handle it.
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Old 8th Apr 2014, 16:51   #9595 (permalink)
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The speed of sound is not constant in water. It varies greatly with pressure, temperature, and salinity. One must also consider that the medium itself is moving, and at the bottom of the ocean the currents can be quite swift and unpredictable.

As a pressure wave (longitudinal?) changes in speed of propagation are interpreted by a microphone as a change of frequency, even if the source and target are stationary relative to each other.
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Old 8th Apr 2014, 16:52   #9596 (permalink)
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Niner Lima

I can see a situation where one engine sucked air first, then the autopilot tried to maintain heading or track and altitude or speed, which resulted in a large yaw with roll angle followed by a spiral into the water.
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Old 8th Apr 2014, 17:07   #9597 (permalink)
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ICAO has just announced a two-day meeting in May, covering several topics mentioned here, such as new guidelines on ULBs and deployable flight recorders:

"The unprecedented and unusual circumstances of flight MH 370 have been particularly difficult for civil aviation officials to resolve and the lack of definitive answers has been much harder still for the victims' families to come to terms with. They, above all, will benefit from a fuller explanation of this accident," he added.

Aliu also said ICAO recently added a new guideline on underwater locator beacon (ULBs) which will take effect in 2018.

ICAOs Flight Recorder Panel is reviewing new methods to speed up process of determining accident sites, deployable flight recorders and the triggered transmission of flight data.

Furthermore reviews will be conducted on aviation security, travel documents as well as requirement for the transport of lithium batteries.
MH370 Tragedy: ICOA to meet on global tracking - Latest - New Straits Times
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Old 8th Apr 2014, 17:15   #9598 (permalink)
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Originally Posted by selfin
FASID CNS/4A states both Banda Aceh and Lhokseumawe/Malikussaleh's PSR ranges are 90 NM. Apparently 60 NM might be closer to the truth.
The 90nm figure is obviously a politically motivated figure. 90 nm is about half the width of the Malacca Strait, so by stating 90nm the Indonesians are stating that they can only see over their own territorial water and have no capability over Malaysian territory. The fact is that for a primary radar the range limit will be about equal to the horizon. Factoring in a target altitude and the radar antenna elevation this will work out to something like 200 miles, probably a little more in practice. (The limitation of a radar's range will not be transmit power or receiver sensitivity, as even late 20th century technology has provided ample capability there.) It is possible that the Indonesian radar operators were blinded from seeing into Malaysian territory when looking to the east, but to the north they would have had a full 200 mile view, at least the military people would have had full range capability, if not the ATC too.
Originally Posted by selfin
MH370 was below Butterworth's RADAR horizon for a significant period enroute VAMPI.
VAMPI is a little over 200 mi from Butterworth so if the "significant period' part of that statement is true, MH370 would have been flying quite low in order to get below radar coverage. This is certainly possible.
Originally Posted by hamster3null
if last known radar contact is near NILAM and MH370 wasn't visible to Indonesian radars at that point, it's pretty straightforward to get from NILAM to 20.8S 104.1E in less than 2000 NM without getting any closer. If radar slide is false though, MAPSO-IGREX-TOPIN-IKASA-Ocean Shield is 2213 NM (370 kts) while giving a wide berth to Indonesian airspace.
I am projecting the necessity of a wider berth than you are, along with an assumption of lower altitude for a significant part of the flight, so that does make the fuel expenditure/ground speed to the northern parts of the search area a better fit.

The unknown here is what the Indonesian radar capabilities actually are, or what they were perceived to be at any rate, they have a 10,000 ft mountain about 30 miles south of Malikussaleh and it would seem logical for them to have placed their military radar antenna somewhere on that height.

Last edited by Propduffer; 8th Apr 2014 at 19:53.
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Old 8th Apr 2014, 17:24   #9599 (permalink)
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777-2 fuel exhaustion simulator test

This post was just magically undeleted.
Originally Posted by suninmyeyes View Post
As a 777 pilot I, like many others, have wondered how the 777 would perform in the scenario where the pilots were incapacitated and the aircraft ran out of fuel. I had my ideas but there is nothing like seeing it for "real" so we tried this in a 777-2 full motion zero flight time approved simulator.

We used a zero fuel weight of 175 tonnes. We let it run out of fuel at FL 250 in track hold and alt capture. However it would not make any difference what mode it was in as everything would drop out. In real life one engine uses fractionally more fuel per hour than the other and there is typically a difference between main tanks of a few hundred kilos, so we had a 300 kg difference between the contents of the left and right tank.

When the first engine failed TAC (Thrust asymmetry compensation) automatically applied rudder. The speed reduced from 320 knots indicated to 245 knots indicated. It was able to maintain 245 knots and FL250. When the second engine failed the rudder trim applied by TAC was taken out and the trim went to zero. The autopilot dropped out and the flight controls reverted to direct mode. The speed initially came back to 230 knots but then the nose started to lower. The nose continued to lower and the rate of descent increased to 4,000 feet per minute, the nose kept lowering and the descent rate increased to 7,500 feet per minute with a bank angle that increased to 25 degrees. The speed at this point had increased to 340 knots indicated, above VMO but there was no horn as it was on limited electrics. About this point the RAT (Ram air turbine) chipped in and the CDUs and copilot's PFD (Primary flight display) came alive. The flight controls stayed in direct mode.The eicas screen was full of messages like pitot heat, flight controls, APU fault (The APU had tried to autostart due double engine failure but failed due no fuel to start it) low fuel pressure etc.

Then with a max descent rate of almost 8,000 feet per minute the nose started to slowly rise and keep rising. We had dropped to about FL170 but the nose slowly rose up to 6 degrees pitch up and we started climbing at about 3000 feet per minute and the bank angle reduced to only 5 degrees. It climbed back up to FL210 at which point the speed had come back to 220 knots and then the nose dropped down again and we were soon back to descending at 8000 feet per minute. So basically a series of phugoid oscillations with bank angle between 5 and 25 degrees and pitch attitude between about 9 degrees nose down and 6 degrees pitch up. It was losing about 8000 feet and then gaining about 3 or 4000 feet with airspeed fluctuating between 220 and 340 knots.

We didn't watch it all the way down due time constraints and stopped the experiment at 10,000 feet but it was consistent all the way down. Having watched it I can say with certainty that if the pilots were incapacitated and it ran out of fuel there is no way it could have landed on the water with anything like a survivable impact. Just passing on the info.

Last edited by rampstriker; 8th Apr 2014 at 18:12. Reason: post undeleted
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Old 8th Apr 2014, 17:29   #9600 (permalink)
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Working together

> but remember the two navies have worked together before with ship under way and other live fire exercises so it is not totally new to each other.

But that doesn't rule out that they have have differing agendas and must maintain a competitive stance toward each other. Different branches of militaries within a single nation do that all the time so it is a virtual certainty that comaraderie between nations is incomplete.
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