As far as I know, they are constant speed trajectories (Inmarsat's). You may also want to fit constant bearing trajectories or variable speed/bearing trajectories... The altitude variations (unless they are well beyond those of a controlled aircraft) do not seem to impact the doppler profile significantly.

It is very much true that the underlying continuous doppler time serie has to be sampled at precise instants to see the doppler peak in the BFO... another way to put it: one the 3 consecutive handshakes around 18:30 in the BFO has to occur in a time frame of a few seconds (maybe not tenth of sec) centered on the moment when the speed vector is in the direction of the Inmarsat subsatellite. In my MonteCarlo simulations, this was the case for tens of simulated runs over a few thousands runs (a few percent probability)... This cannot be a coincidence, it would mean that the handshakes tended to occur when the flight conditions changed.

That's true again, we know nothing between the handshakes and we have to make assumptions like trying to find/fit trajectories with minimal speed or bearing variations. Back to the percentages, certainly, the lowest probability goes to the relative timing between the jet virage/manoeuver (toward the south) time sequence and the handshakes instants... either the handshakes are designed to be initiated when flight conditions change or this is a huge coincidence (which seems to happen also earlier in the flight when the plane diverted from its route to Beijing).
Jeff

It's a good observation. But I have two points to make:

* If you do a least mean square fit for all points except around 120 min, I think you'll find a scaling factor that is somewhere above 0.25 (not 0.15-0.2), and, at that scaling factor, you can't get the "possible turn" peak to match the data at _any_ heading.

* But if you assume that MH370 was climbing at around 18:25 UTC when the "peak" was observed, you can fit the peak nicely to the course before the turn. Put in something like ground speed 480 kts, heading 285, climb rate 4000 fpm. Recall that the Malaysian military radar picture has a "hole" in the track. It could be consistent with dropping to 5000' above the Strait of Malacca (for whatever reason) and then climbing back out.

BTW, how do you get the 17:07 data point to fit? It's been one of the problems bugging me for a long time. I can force-fit it by setting the heading to 5, but it's pretty artificial because we have the FR24 track up to 17:20 and it is showing straight and level flight at heading 25 from 17:01 to 17:20.

To me, both BFO inflexions at 1:07 and 2:25 are indicative of a turn (I don't see another phenomenon to explain such a rapid variation of the BFO), the 1st is when the plane diverted from the KL->Beijing route to turn back to Malaisia, the 2nd is the large turn toward the south.

The handshakes timing is very intriguing since it seems to capture/retain the exact flight sequence. See my answer to RetiredF4.
Jeff

Well, altitude changes produce speed changes. Climb or descend will produce different speed delta / doppler, lower altitude cruise will produce less groundspeed and thus different speed delta / doppler.
Therefore it has quite significant effect on those computations.

That´s where i have the most reservations against those theories. While a southern routing by deliberate human action or by autopilot with the human factor removed would fit straight track and constant altitude, the northern routing with human input would look quite different in order to avoid continueous detection threat, and that would have to include changes in track, altitude and thus speed.

Therefore in assuming a constant track and speed the northern routing is excluded by this assumption itself.

With a scaling factor of 0.25 (instead of 0.15-0.2), the 1st plot of the 2nd page of my doc would basically be translated higher (the 120 min peak would reach approx 290 Hz instead of 250 Hz): it would still be possible to reproduce the 120 min turn but no longer the initial conditions (already out of the enveloppe) and even around 180 min (the min enveloppe would be at 125 Hz slightly higher than the BFO).


Ok, this can kill this potential signature... 4000 fpm is ~22 m/s or ~14 m/s projected onto the LOS (@~40° of elevation)... which translates as a doppler of ~77 Hz (at 1640 MHz) hence 11.5 to 15.5 Hz after the scaling of 0.15 to 0.2... The last plot of my doc for the north trajectories shows that we need more than 50 Hz to get the BFO into the enveloppe of the tens of thousands of simulated flights. I would then need ~13000 fpm to fix the gap. But as RetirdF4 suggests, the ground speed would decline accordingly (also modifying the doppler), so I will introduce large altitude changes in the conditions you suggest to check it.

I got these runs fitting the 17:07 value of the BFO through the MonteCarlo simulation: among the thousands of simulated runs, some of them happens to replicate this inflexion at 17:07... this is exactly the same for the ~18:30 turn (some of the thousands of simulated runs replicate the peak), it seems to rely on a precise relative timing between the bearing changes (we need a turn around 17:07 to generate it) and the handshake instants.
Jeff
PS) a scaling factor between 0.15 and 0.2 is close to the wavelength value at 1640 MHz (0.1825 m): would it be possible that the Inmarsat BFO plot is plotted with a wrong unit (m/s instead of Hz) ?
PPS) to RetiredF4: note that these models/assumptions for the simulated trajectories does not hold at the 120 min turn, the only assumption behind the potential signature is the turn (toward the south or the north) itself... these assuptions apply more to the following hours of flight .

Killing yourself pulling 228 persons in the death with you is terrorist and criminal. Isn't it? In that hypothesis too Dr M. assets that it is Boeing's responsibility:=

Some earlier posters have implied that if MH370 ditched under control then it would have broken up on contact. This is not true. FAA certification requires that an aircraft can survive a ditching.

Fact Sheet ? FAA Regulations on Ditching

Regulation 25.801(b) states "Each practical design measure must be taken to minimise the probability that in an emergency landing on water the behaviour of the airplane would cause immediate injury to the occupants or would make it impossible to escape".

25.801(c) states that the ditching behaviour must be investigated by model tests.

When I joined BOAC over 45 years ago we had to watch a film of the VC10 certification ditching trials. They were carried out in a large tank which was normally used for designing ships.

There have been several survivable airliner ditchings in the past. If MH370 was ditched then it will be intact on the seabed.

I agreed with you wholeheartedly at first, but other posters here have pointed out (in deleted posts) that FR24 data as well as the probable location of the aircraft at 1:07 make this premise unsupportable. It would probably have still been northbound over the Malaysian penninsula at 1:07. Bloomberg News informed us that the last ACARS transmission at 1:07 included a position report: The engineers at Inmarsat were able to validate their estimates of the plane’s location by matching its position at 1:07 a.m., when it sent a burst of data through its Aircraft Communications and Reporting System, McLaughlin said. That final transmission on Acars included a GPS position that was used to calibrate the other estimates, he said. http://www.bloomberg.com/news/2014-03-21/missing-plane-flew-steady-speed-over-ocean-inmarsat-estimates.html - but we don't know what that position was. (Thank DocRohan for posting that link here)

Consider this.

From the radar, I have the location of the turn roughly at 18:30 at 6.7N 95.5E, which gives me initial satellite elevation 53.2°. Final satellite elevation is 40°. We can calculate line of sight distances for these angles. I get the difference of 900 km (you can double check). To travel 900 km in 5.67 hours, we need mean line of sight speed 159 km/h and mean Doppler shift 235 Hz @ 1.6 GHz (241 Hz @ 1.64 GHz).

What we can do now is take BFO data points for 19:45..00:11, extrapolate them back to 18:30, and see what mean observed BFO we get, and what scaling and bias get us there. I get BFO 160.5 Hz. If I assume that the frequency bias is given by the BFO at 16:30 (~87 Hz), mean residual Doppler is 73.5 and scaling is 73.5/235 ~ 0.315.

In your case, you seem to be getting scaling below 0.20 because you're trying to fit scaling and bias at the same time, and you can only get low scaling together with high bias. Which is why you're getting bad fits to the first 30 minutes.

Does the satcom firmware command an updated handshake with the satellite whenever there is a significant bearing change? I've seen it reported that the antenna was low gain (omnidirectional?) and perhaps didn't have beam steering. So this would seem pointless. Can anybody clear this up?

Calm sea, then yes, you could ditch keeping the wings and fuselage intact, but minus engines and flaps. But what are the chances of a calm sea in the open ocean? Flying into the swell would be a huge impact. Even flying boats avoided heavy seas.

And I don't believe a controlled ditching is compatible with a suicide. Suicides like a quick, painless death.

I agree up to the point that under certain conditions, such as during imminent danger at remote locations (outside VHF radio / radar range or total comms failure), as a last item prior to an emergency landing on land or ditching in the ocean, why not add "ELT . . . ON" to the QRH / Emergency check list?

However unlikely, it does happen. An example of total comms failure but without any other failure modes and within radar range, enabling the use of the transponder:
Air France B772 near Zurich on Apr 15th 2013, loss comm | AeroInside

Obviously, in this situation the ELT activation would not be necessary.

I mentioned this several hundred posts ago. I would certainly switch on if I was in any sort of emergency descent, depress, etc. It is just above my head and I have bashed it a few times.

I still maintain that the aircraft is at the bottom of the sea and intact.

No reason for the engines to be 'torn' off as the motors would be turning at initial impact. Most of the energy would have been absorbed by the time the flaps hit the water.

Given how low credibility is assigned to the Chinese methods, I wouldn't consider it likely, there is still plenty of square km to be searched around the current spot. The "current" 10 km radius can be easily doubled and this quadruples the area to be searched.

Aren't the engine pylons attached to the wing with shear bolts to allow them to break away at impact?

That's the general idea - you want to lose engines behind since they could be a source of ignition.

The idea is to make the wing box and its fuel tanks not be overloaded by the impact moment forces on the nacelle/pylons when it digs in.

Fair point. Can't hurt to get it on before impact if you have the time/task load available.

Lots of interesting things here to talk about

someone said the flaps would come off

if no one was flying, maybe they would not be down and less likely to come off?

about the ELT and switching it on as part of a checklist. How about also having the ELT on a timer, set before ENGINE START based on amount of fuel/estimated time to dry tanks at presumed fuel burn rate.

eg: 7 hours of fuel on board, set timer for 6 plus 45. And ELT will start transmitting with fifteen minutes of fuel left.


And the ELT timer would be reset to neutral/off during the after shutdown checklist.

In this way, "G" forces would not be the sole determining factor for transmission. Also remember that if the plane is still airborne, the ELT will transmit farther (ref terrestrial receivers)

Reference was made to switch the ELT on. I don't think this model of B777 would have the ELT switch on the overhead panel.