B777 9M-MRO findlostaircraft.co.nz threads Aug 12, 2015 14:00:55 GMT 12
Post by grgrimmer on Aug 12, 2015 14:00:55 GMT 12
Posted: Sat Aug 09, 2014 3:18 pm Post subject: MH370
Hopefully, we now have this forum up and running again!
I tried to post on it and found that I was locked out!!!
After spending a lot of time sorting it, all appears to be running okay now.
I'm after the following information if anyone reading this knows, (or knows someone who knows) and any help would be appreciated if someone can forward this to me, either directly, or post the answer on this forum.
We know that the Ground Station - (GES) (in this instance Perth) attempts to contact the aircraft - (AES) - via the satellite every hour for a 'handshake' checking that it is still in the area. Presumably, if the GES hasn't had a 'Log-off request from the AES and doesn't get an answer to a 'handshake' request, then the GES will check with other neighbouring satellites to see if any of these can make contact in case the AES has traveled into their area.
1/ If none of these can make contact with the AES, then what does the GES do?
2/ Does it then go to another timer frequency - say every 15 minutes to attempt a 'handshake', or some other time frame?
3/ As with a cellphone, if it cannot make contact with a cellphone tower to log-in to the Network, it will keep trying at certain periods of time until it does connect - if for some reason the AES has this same problem, at what timing frequency does the AES unit attempt a log-in with the GES?
Looking forward to any answers,
Posted: Tue Apr 28, 2015 11:40 pm
As far as I can ascertain once the GES initiates a failed expected hourly logon through the Inmarsat 3F1 satellite at the set frequency range to 9M-MRO no further pings are undertaken. Luckily (in context) The flight was always in the same one Inmarsat communication satellite coverage area.
It like a game of ping pong. Table is there (Satellite) player one is there (Ground) nothing. Player two turns up (MH370) active. Player one hits ball 8, player two has already zipped to the toilet. Failed play and no one to play with.
The flight did initiate its own an out of sequence ping prior to the failed hourly login possibly due to end of flight scenario such as engine generators electrical spike/RAT deployment?
6th log-on initiated by the ground station 0010.58
7th log-on request initiated 9M-MRO 0019.29 (Spike?)
Failed log-on initiated by the ground station
Posted: Fri May 01, 2015 9:50 am
Thanks for your reply.
Yes I understand what you are saying, but the problem is no-one in the 'know' of satellite/satcom systems seemed to know exactly how these systems actually worked - probably because this occurrence is something completely new to them - something that was never even imagined could happen when the software was written. What you are saying is what is meant to happen, but in this situation of 9M-MRO it is not that straight forward.
However, in the latest releases of "Factual Information" released March 7th 2015, and April 15th 2015, by the "Malaysian Ministry of Transport Safety Investigation Team" they do state answers to these questions.
These Reports can be found on this link and in complete form on other links: www.mh370.gov.my/index.php/en/media2/transcript/category/13-mh370-safety-investigation-public
Interestingly, in these Reports, they now claim that the final Log-on at 0019.29 was a legitimate Log-on.
The thing that really 'grates' me is the emphasis put on these Satcom communications and the explanations they feed us as to why it has happened.
From my understanding of the electrical system of the B777 (after reading the 777 Electrical Manual) if ever there is even a hint of a major electrical shortage, one of the first things to be shut down is the Satcom as this is considered as non-essential equipment to the safety of the flight systems, yet through all of the major shortages of electrical supply claimed by the experts, this (obvious power hungry) device remains on... only to be starved of power when the aircraft runs out of fuel!
Then to top it off, it miraculously starts up again when the RAT pops out - a small wind driven generator designed to generate enough power for the essential flight control systems only.
To me, this is all simply fanciful thinking, and just look at all the scenarios that have been built on this thinking!
Before you can build an accurate scenario, one needs to get the foundations of the theory correct first.
As far as I can ascertain from the information I have available, there are only four reasons that could cause the Satcom via the Satellite Data Unit (SDU) to go off-line.
1/ The 'Primary Engine Driven Generators' (IDG's) go off line (stop generating, or are switched off by opening the field and generator electrical breakers) and the 'APU' (Auxillary Power Unit) doesn't start - or the APU circuit breaker is open because there is a fault - which in turn prevents the APU from connecting to the Main Buses
2/ The 'Electrical Load Management System' (ELMS) senses a high electrical load and shuts it down until the electrical load decreases to a safe level. This would only be in extreme cases though as other functions such as the Galley are shut down first.
3/ The "Left Main Bus" fails, or power is lost to the Left Main Bus - resulting in cutting power to the SDU
4/ The "Left Main Bus Tie" switch is locked "open" starving the SDU of power. Any loss of power to the Left Main Bus causes the SDU (and hence Satcom) to lose power.
If power is restored to the Left Main Bus, then the SDU (and Satcom) will connect back on line and attempt a Log-in with the GES, but this cannot happen with power from the "Back-up engine driven generators", nor the "RAT".
To think that there could be a 'spike' in the power (as in the last Log-on) I would be very doubtful, as there is also the battery in the line and this of course acts as a condenser that irons out any possibility of a spike.
The engine driven electrical generators are just that - engine driven. So long as the engine (in this case a gas turbine) is turning, the generators are generating electrical power.
When a gas turbine in a fast moving aeroplane is deprived of fuel, it doesn't just stop turning... it windmills - and so hence is still generating electrical power. The only way it could stop generating power (without human intervention) is for the turbine to stop spinning, and this could only happen if the aeroplane came to a stand still... in other words - physically impossible if it is still airborne.
Initially I was under the impression that if the pilots turned off the Primary engine driven generators, then they could not turn them back on.
On researching this further, I find the pilots can disconnect and reconnect the Primary IDG's (Engine driven Primary Generators), when it comes to it's electrical power output, but not if they disconnect the "drives" to these Generators.
After studying this more thoroughly, what they are talking about is the IDG drive (presumably something like a gearbox) and the purpose needed to disconnect this is obviously if something goes mechanically wrong with the IDG - such as low oil pressure (have warning lights for this). Better to have a way of mechanically disconnecting the Generator from the engine, rather than have the engine self destruct due to a seized generator! Once this drive is disconnected, if they were able to attempt to connect it again while the engine is running, would cause enormous problems such as exploding the gearbox... sort of like throwing your car into gear without a clutch - with the motor revving it's head off. Hence they are only talking about the DRIVE not being able to be reconnected in flight - and consequently the generators.
In my article, I believed at the time that the only way 9M-MRO could land without the GES being sent a signal was if it was out of line of sight of the satellite, but I now know that this is not necessarily a requirement. In the case of a very well planned elaborate theft of an aeroplane such as 9M-MRO, all that is needed is to override the undercarriage "squat switches" and then the Satcom would not send a signal out to the GES (via the satellite) to say the flight has ended and the aircraft is on the ground... at least this is the way I understand the system. Hence there is in my mind, no more requirement for it to have landed in the Himalayas - It could have landed anywhere!
Posted: Sat May 02, 2015 12:01 pm
As I understand mainly from satellite experts such as Mike Exner who also worked with pilots in a 777 simulator, and the Inmarsat data logs published each aircraft logs on from the ground station with a unique identifier. Once the link is disestablished (end of flight) any further attempt on the unique identifier when an aircraft shuts down disestablishes. This all third hand information but working through the Inmarsat logs and running some extremely amateur calculations it does make sense. According to Inmarsat “Inmarsat has confirmed that during the flight, no SATCOM signalling or traffic was routed via any other satellites (including MTSAT) to any other GESs (including MTSAT7 GESs)” so again I can only take that as third hand published information. It would be good to hear from an actual satellite engineer to confirm all this. The Boeing 777 AIMS Cabinet is one of two Airplane Information Management System cabinets, which route numerous information to and from the SDU, including ACARS data, Navigational data, AES ID and the Flight ID.
Yep going back through screeds of data the IDG receives 115v ac from the Left Main bus routed with power from both engines on the 777. They share electrical load however if any one engine fails essential systems are shutdown including SATCOM. Normal comms is routed through HF radio.
The interesting issue is over the span of several minutes, between 18.25 and 18.28, the SDU transmitted as they called it a flurry of brief electronic messages. Going through ATSB data and the 585 page report this has not been explained or elaborated on as to how or why?
Since the APU has to be pilot initiated this has been discounted. Again going back through schematics and Boeing information the last out of sequence logon has been explained as shutdown sequence.
The whole issue is everything is the most probable scenarios. The end of light kinaesthetic analysis came down to left engine shutdown, right engine shutdown, RAT (SATCOM Spike), spiral into the sea. But until a FDR is found, retrievable and readable and wreckage analysis is completed most of it is all educated guesses.
I created a file on MH370 as there is so much data and submissions from various contributors from satellite BFO/BTO calcs/Biases to images, flight path analysis and avionics. I have a little library, use university library and study towards Bachelor of aviation and completed a paper on accident investigation. Only have a PPL but grounded medically. The more I learn the less I know! I do wish my Father in law (Avionics and airframe engineer) was alive he could explain everything.
For my two cents extremely amateur calculations and even worse algebra, and only using published Inmarsat information I come up with a location of S38.09 and E87.5. My brain is getting mushy at the moment though too much info.
Essentially what we have is an aeroplane is lost under suspicious circumstances in vast area it should not be.
I am confident in the satellite system/data as over the year many sources have supplied objective various views. Using an objective critical analysis there is a lot of rubbish out there and some have not looked at the whole picture. As you can see from this site any many others any aircraft accident/loss has multiple aspects to it.
Good to have some info shared. I am not studying summer school so will look into MH370 and the other losses in detail then.
Posted: Wed May 06, 2015 1:35 pm
Just a couple of points...
Quote: "any further attempt on the unique identifier when an aircraft shuts down disestablishes"
Yes, that is true. This is exactly my point. The GES didn't receive a signal to say that 9M-MRO had landed, so the 'unique identifier' was still logged into the system. The GES sent a handshake request at 00:11 and it was acknowledged by the AES (9M-MRO). Eight minutes later 9M-MRO requested a Log-on to the system - a system it was already logged on to. The 'powers that be' claim this was due to a power spike caused by the RAT coming on line... According to all the info I have, this is a physical impossibility! The RAT is not even linked into the same wiring circuit as the SDU/Satcom. Not only that, if the three main power sources (IDG's and SDU) had shut down (as we are led to believe), the SDU/Satcom has long been off line as non-essential to flight safety!
Quote: "Since the APU has to be pilot initiated"
The APU does not have to be pilot operated. If all power is lost to both main buses, the APU will start automatically regardless of where the pilot's switch is. The only exception to the APU coming on line in this situation is if there is a fault detected in the line - and if this is the case the APU electrical breaker will remain open.
Quote: "if any one engine fails essential systems are shutdown including SATCOM. Normal comms is routed through HF radio."
As I have pointed out previously, if an engine shuts down (stops delivering thrust), the generator still generates electricity as the turbine is still spinning (windmilling) so I guess you have simply meant "primary generator (IDG) fails" instead of "engine" in this instance?
If any one primary generator fails, it's role is taken over by either the other engine's primary generator, or the APU. If for some reason the APU doesn't come on line, the EMS will load shed - shutting down the Gallery first and if this means it needs to include the Satcom as well to keep enough power for more important systems... it will. I have not to date found anywhere where it says which order it shuts down services other than the Gallery though, so I can't tell you the order of priority.
The biggest problem I see to unravelling this mystery is that the whole thing is a very complex problem in that for one person to solve it, they would need to be an expert on absolutely everything to enable them to understand what has happened.
Unfortunately there would be no-one alive that would fit that criteria, so all anyone can do is try to learn as much as they can of every system - to see if any of us can work it out... what appears at this stage as an impossible task!
Posted: Thu May 07, 2015 9:45 am
To summarise I am confident from the released data, expert information released over the year that once the ground state attempts its hourly ping on the frequency no response discontinues initiation so would be confident in a yes.
Going back through 777 avionics manuals avionics are is run through the AIMS cabinet interfaced through two different data buses, there are two cabinets each with four core processors and input/output modules. Beyond that the complexity of the system once battery power is exhausted (Pretty quickly) the RAT electrical load may return back through various channels or ARINC 629 interface and turn on/off the SATCOM system.
So I say RAT plausible.
As for the APU I can get a definitive answer on auto-start as different AME’s are vague some say yes some say no. However APU start can only be below FL130. The APU runs off the central fuel tank and same as the main engines so under 15psi pressure pumps shut down so it was not in the end of flight sequence of MH370. I assume (dangerous word) that’s where the ATSB EOF summary.
I gather what are saying about windmilling reading through the RR Trent 800 manual the IDG synchronous drive generator needs to spin at a constant specific high RPM from the IP turbine to generate power. What I can’t discern is in a dive, will the internal turbine windmill enough to generate enough constant power for a significant time to create electrical load.
Was this what caused the out of sequence spike? Plausible.
You are right – in an accident investigation the lead investigator assigns various areas to experts. The bigger the mess the experts become teams. Various areas of analysis such as metallurgy/engine teardowns etc. are done by approved AME's/analysis.
That’s what has intrigued me on MH370 (and other losses) as I have studied aircraft accidents for years and done a university paper on aircraft accident investigation. Studies are all about analysing physical accidents or waterborne accidents where wreckage has been recovered.
I will check back soon – got another university paper essay due and exam soon.