Surely though, BEDAX would be a better choice of starting point?

MH370 was no -300ER.

Form that article, a succinct summary:

I think we should be interested in seeing the outputs from both simple and monte-carlo models here. They certainly interest me, and the clustering of the high probability tracks is quite significant. I look at it like this: Every approach shown to be wrong has potential to remove distraction and complexity from the solution. Every approach not shown to be wrong, adds to the information we have about likely course solutions. I don't think it's a contest, just a process of elimination.

The BFO is surely not the sole discriminant. If course and heading change, you need an explanation for that. The presence or absence of such an explanation would also therefore be a discriminant.

I know ;) but the differences between the -200ER and -300ER for this particular topic (FDR and how it is connected / powered in a ER 777) are few.

Cockpit tampering?
 

The report in the Telegraph suggests that the satcom reboot implies some sort of mischief in the cockpit. Isolating all nonessential systems is also very close to the top of the 'smoke in the cabin' checklist. Communications with the ground give no indication as to why anyone would start executing that checklist, but it's probably something every wannabe pilot has tried in their simulator. Whether it was a real or perceived emergency or a ploy to clear the cockpit is a matter for speculation, but I would think the knowledge of (more or less) how to do it would be fairly common in the aviation community.

We don't have an exact time for when the power went off. We only know when power to the Satcom terminal resumed: 18:25 UTC.

The previous Satcom terminal handshake was at 17:07 UTC.

There was no response to Boeings Ground to Air ACARS request at 18:03 UTC so we can most likely guess that the power to the Satcom terminal was off then.

That leaves a period of 56 minutes where we have no idea if the Satcom terminal was powered or not.

SpannerInTheWerks says:
 

"I suggest this Thread is held until any relevant further information is received?!

Nothing worthwhile is being added at the moment."

Gotta agree - nothing but conjecture and speculation is being added, and none of it (at this point) can be considered helpful.

In my humble opinion, anyway . . .

Agree wholeheartedly that this thread should be locked and a new one started once new information becomes available.

The Mods did exactly that (more than once) during the AF447 loss and it was both effective and appreciated.

Hyperveloce
I am a retired airline pilot rather than a boffin. It looks to me from the data published that if LNAV is used it is likely that Wilkins (YWKS) was the "destination" or somewhere in that region.

All tracks flown in LNAV however small are G/S not rhumb lines. It would be reasonable to assume that at least for the cruise the aircraft would have flown a constant Mach No. (but not G/S as that is dependent on the upper winds) and changing heading to maintain the G/C track. In which case if you could take the 7th ping arc (use the ATSB yellow arc) and compare the tracks from various waypoints in the north and compare the times to cross the earlier ping arcs. Likewise you should be able to take the last "fix" round about MEKAR and look at the what waypoint(s) tie in with it).

If I was "doing the flight planning" I would have concentrated on the FIR points as turning points as they are handovers between ATC units. Skyvector.com has a good flight planning facility to play around with.

My understanding of this is very weak but from what I have read there are four sources of navigation information that George might use to hold a course. They are Inertial, magnetic, radio and GPS. It seems that aircraft comms were impaired and the information we have consists of some satellite pings. With no comms, what information is still available to the auto pilot to maintain course?

Can anyone shed some light on the possibilities? My reason for asking about the rhumb lines is that even if all other systems are switched off, a magnetic compass might still provide a heading.

Ulric,


I'm not a T7 expert, but...


FWIW we used to fly much earlier aircraft between Kano and Jeddah using a single course (C) of 072 or 252 for some 7 hours, on Hadj flights. This was a "Modified Lamberdrome" route, ie. a straight line on a Lambert's projection, between the Standard Parrallels. This gave us a Base leg at Jeddah and very long Finals at Kano.


Following ONE then TWO engines shut down... Others may have more ideas for the 100 -ish mile descent's heading.


This flight from KL would have expected sunrise on the Starboard, ( right) side. NOT the Port ( left).


Something similar, with sunrise in the wrong direction, had happened to G-ALDN, the " Hermes in the Desert", 60 odd years ago.

Should thread be closed?
 

I should stress at beginning that I'm not a pilot, professional or otherwise (unless you count PPL 50 yrs ago in a Tiger Moth , open cockpit, no electrical system, no brakes and only air to ground comms a Verey Pistol!!)

However, I do see a reason to keep thread active. What I think I am seeing from authorities is that as finding the aircraft becomes less and less likely, they become more and more definite in attaching blame to the aircrew. This thread does keep things balanced and evidence based. As fellow pilots I think you have a role to protect your colleagues from a rush to judgement unless and until the evidence clearly supports such a judgement.

Gysbreght,


That looks fairly logical, thank you.
My "100+ miles..." should be Track miles, to allow for the possibility of not maintaining a constant heading, when without engines. ( RAT might help, I suppose.)

Unfortunately, 2nd engine out = short decent
 

Gysbreght,
(2nd hand info...)
The B777 simulation results from the last month show that the one engine out case is handled gracefully - TAC (Thrust Asymmetry Control) will keep the plane flying straight. At first airspeed will be sacrificed due to single engine thrust limits. Then, altitude will be sacrificed to maintain airspeed. Eventually, flight will stabilize at an altitude and airspeed combination appropriate for the single engine case. (There are specific max engine limits for single engine operation that 'can' be different from the limits for 2 engine opration.)
An article I found very informative on TAC (beyond reding the manual...)
Thrust Asymmetry Compensation

Things get uglier when the 2nd engine cuts out...
1) TAC will (would?) drop out when it detects that both engines are out.
2) When the engines stop supplying AC power and hydraulic pressure, the hydraulic flight controls (including the TAC-adjusted rudder) will remain locked in place.
3) The Autopilot will drop out (disengage) with the total loss of AC power.
>> This creates a race condition in which the exact sequence of events will determine the flight control settings locked in after power is lost.

The suggestion has been made that the Autopilot would drop out first, with the rudder trip from TAC still fully applied. This would lead to an unfavorable condition while power is out. And, when power returns, the autopilot remains disengaged, so these flight control positions will be maintained.
-- This is what leads to the expectation of a very short glide period. The the plane will begin turning right at 2nd engine flame out, and continue that turn even when power is restored from the APC and/or RAT.
This is most likely the 'spiral decent' mentioned in the June 26th ATSB report.

Can anyone tell me how the "log on" at 18.25 UTC determines that "this" was MAS370 ?

I presume "user data" unique to the satcom equipment ?

Gysbreght,
Three distinct dependencies-
1) Autopilot disengages when all AC power is lost

2) The flight control surfaces will (would) lock up on loss of hydraulic power (not on loss of electrical power - sorry, I left that vague). This is a different chain of events. If Hydraulic power is restored, before pressure in the lines drops, then there will be no lock up.

3) TAC drops out when neither engine is powered. Part of the race condition is that TAC would release the rudder back to a neutral (to the prior trim) position, unless the hydraulics have already locked.


Battery backup keeps the lowest level flight controls operational. But, the plane is no longer in Normal mode (Law 1), so many of the stability controls would no longer apply. That is what allows any remaining rudder to continue to turn the plane.

The SATCOM logon has the equivalent of a hardware MAC Address that is specific to that airframe. The range ring for the logon passed through the last radar reponse location +/- 3 miinutes to the accuracy of these rings. This was verified by comparing the known and calculated position of other aircraft.

I suspect this is one of the reasons for believing the aircraft was intentionally disappeared, as it's consistent with someone turning the power back on shortly after they knew they'd be out of radar range. I believe someone mentioned a few thousand posts back that the SATCOM terminal is on the same power bus as some other communication equipment, so turning off the power to that bus would turn all that equipment off.