Posts by user "D Bru" [Posts: 14 Total up-votes: 0 Pages: 1]

D Bru
June 15, 2025, 15:31:00 GMT
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Post: 11902557
Originally Posted by fox niner
777/787 driver here.

When you lift off the runway, the gear doors open REGARDLESS of gear lever position. If you do not raise the gear within 30 seconds, the gear doors close again and you keep the gear down as you apparently desire. In the video, the gear doors are closed again as the airplane flies into the suburb. This requires normal hydraulics in system C, which was apprently available as the doors are closed again.
Originally Posted by DaveReidUK
Some previous posts have suggested that the 787-8 behaves differently from the later variants in respect of the automatic opening of the gear doors.

Are you saying that they are wrong?
I'm posting some YT-links to show that 787-9 gear doors indeed open on lift-off, while the -8 gear doors open only when gear up is actually selected. I also include links to a 787-8 and a -9 that keep their LG down after departure. The 8 doors are not opening. The 9 doors do open again regardless and indeed close again about 30 seconds after lift-off.

1. 787-8 LG retraction: boogies tilt forward, doors open, boogies tilt inward:
2. 787-9 LG retraction: doors open on lift-off, boogies tilt forward before inward:
3. 787-8 LG kept down: doors remain closed:
4. 787-9 LG kept down: doors open and close again about 30 secs after lift-off:

Last edited by D Bru; 16th June 2025 at 04:24 . Reason: Following pertinent comments EXDAC & Roo (thanks!)

Subjects (links are to this post in the relevant subject page so that this post can be seen in context): Gear Lever

D Bru
June 17, 2025, 22:37:00 GMT
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Post: 11904725
EEC MN4 - TMCA

Without a doubt one is looking at a very, very rare event, most likely the result of an unlikely/unlucky combination of issues, the grim gravity realised by the F/C (mayday) immediately after T/O. As a very, very FF/retired EU bureaucrat/economist/lawyer with an as ever staunch penchant for data/facts, I'm therefore wondering whether VT-ANB engines had already their EEC MN4 microprocessors replaced as mandated within 11000 cycles or 12 years per AD 2021-21-05 https://www.govinfo.gov/content/pkg/...2021-25491.pdf . This AD was prompted by in-service occurrences of loss of GEnX engines thrust control resulting in uncommanded high thrust. Uncommanded high trust on (at least one of) the engines during the TO-roll, in particular past V1, resulting in a discrepancy with the actual (likely derated)thrust settings, could have triggered TMCA on or just before lift-off.

Subjects (links are to this post in the relevant subject page so that this post can be seen in context): Air Worthiness Directives  GEnx (ALL)  MAYDAY  V1

D Bru
June 17, 2025, 23:03:00 GMT
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Post: 11904743
Originally Posted by EXDAC
How would the thrust lever idle condition have been satisfied?
Originally Posted by EDML
That is not what the TCMA logic is supposed to do. Only high thrust with the thrust lever idle should trigger the TCMA.
Yes, there's another snag in the million dollar Q for the explanation. If the MN4 microprocessor can run amok, so could perhaps the TCMA not exactly act as intended. But I take in both your pertinent comments and will (as per the mods advice) from now on sit on my hands and only read until the prelim report hopefully soon!

BR, D Bru

Subjects (links are to this post in the relevant subject page so that this post can be seen in context): Preliminary Report  Thread Moderation

D Bru
June 26, 2025, 21:39:00 GMT
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Post: 11911519
Originally Posted by Senior Pilot
https://www.pib.gov.in/PressReleseDe...x?PRID=2139785

Status Report on recovery and examination of data from Black Boxes \x96 Air India Flight AI-171

Note the front EAFR is the one with RIPS battery backup.
Thx, this indicates at least two issues:

1. The investigation's reliance on the front RIPS battery backuped EAFR indicates a confirmation of a total electrical power loss;
2. Earlier reports (i.e. AVH, now removed) of successful readout of and observations from CVR have proven outright fake.

Regards,
D Bru

Subjects (links are to this post in the relevant subject page so that this post can be seen in context): AI171  CVR  EAFR  RIPS

D Bru
June 26, 2025, 22:05:00 GMT
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Post: 11911534
Originally Posted by grumpyoldgeek
I have to disagree with point 1. They did not give a reason for using the front unit and I don't see why you would assume one.
Really, Grumpy? If aft EAFR (not RIPS supported) would have had any data/voice after elec failure following T/O, I think the AAIB would have been more than happy to extract everything from that one since it was found earlier and most likely more intact than the front one. Regards

Last edited by D Bru; 26th June 2025 at 22:17 . Reason: Sorry but I didn't want to sound too "grumpy" ;)

Subjects (links are to this post in the relevant subject page so that this post can be seen in context): AAIB (All)  EAFR  RIPS

D Bru
June 28, 2025, 17:04:00 GMT
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Post: 11912578
Originally Posted by Someone Somewhere
I am not certain on that. Remember the 737 didn't have them on the standby bus (Jeju). The NTSB doc states they're powered from the L/R 28VDC buses on the 787.

This shows the centre TRUs can only power the instrument buses not the L/R DC buses, the RAT can't really power the right TRU without powering both R1/R2 buses, and powering the left TRU would require powering the left 235/115 ATU which would probably be a lot of magnetising current even if not much actual load. The contactor naming supports that.

My money is on the L/R DC buses being unpowered in RAT operation; only the CA/FO instrument buses and the 235VAC backup bus.
That's exactly why I would really recommend reading through the NTSB FDR report on the 2013 JA829J Boston incident helpfully posted by EDLB . There's potentially a wealth of data concerning a to me at least surprisingly number of 2000 of parameters written on a 787 EAFR, that is that at least if there's elec power. Even the 10 min RIPS is useless if there's no data sent from electrically shut off systems.

Last edited by D Bru; 28th June 2025 at 17:06 . Reason: deleting a repeat image of the elec system

Subjects (links are to this post in the relevant subject page so that this post can be seen in context): EAFR  Electrical Busses  FDR  NTSB  Parameters  RAT (All)  RIPS  TRU

D Bru
June 28, 2025, 19:17:00 GMT
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Post: 11912637
Originally Posted by EXDAC
The requirements I have seen indicate that RIPS is applicable only to CVR or the CVR function of an EAFD. If you are aware of any requirement for RIPS to support flight data recording would you please provide a reference.

FAA requirements and the discussion/changes that resulted from the initial NPRM here -

https://www.federalregister.gov/docu...er-regulations

Yes, possible electric failure on the eafr is of course a totally different story concerning voice recording

Subjects (links are to this post in the relevant subject page so that this post can be seen in context): CVR  FAA  RIPS

D Bru
July 01, 2025, 10:21:00 GMT
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Post: 11914168
Originally Posted by Musician

1) I had seen the "50 feet below runway" referenced as well, and double-checked on Google Earth, and could not confirm this. The terrain looks reasonably level. I'd be happy to see evidence for this claim, but until I do, I'll think it's false.
According to official data ( https://aim-india.aai.aero/eaip-v2-0...AAH-en-GB.html & https://https://aim-india.aai.aero/eaip-v2-05-2023/eAIP/VAAH-ADC.pdf ):
05 THRE 180ft, TDZE 186ft
23 THRE 189ft, TDZE 189ft.
Google maps directions gives for walking from the nearest road next to the 05 THR (end of 23) to the accident site "mostly flat", i.e. going up 1m and going down 4m. That indeed can't add up to 50ft below RWY, more like 10/20ft, depending on the RWY elevation reference point. Moreover, the two floor building Air India 171 struck is about 20ft high.

Subjects: None

D Bru
July 11, 2025, 23:43:00 GMT
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Post: 11920013
10 seconds

Baffled, as probably all of us. But 10 seconds between \x93cut-off\x94 and \x93run\x94 is not excessive imo:

08:08:42 - max speed
08:08:43 - cut-off eng 1
08:08:44 - cut-off eng 2; run-down eng 1
08:08:45 - run-down eng 2
08:08:46 - startle moment
08:08:47-48 - instruments, levers and switch scan
08:08:49-50 interrogate other pilot why he moved switches
08:08:51: other pilot denies
08:08:52: eng 1 fuel switch to \x93run\x94
08:08:53: it\x92s both fuel switches that were cut off
08:08:56: eng 2 fuel switch to \x93run\x94

Subjects (links are to this post in the relevant subject page so that this post can be seen in context): Fuel (All)  Fuel Cutoff Switches  Preliminary Report  Timeline (Preliminary Report)

D Bru
July 13, 2025, 21:49:00 GMT
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Post: 11921703
A few observations

While IMO the Air India 171 preliminary report ( PR ) in some aspects leaves ample room for speculation rather than soothing it, let’s not loose sight of a straight forward assumption that what is presently known to AAIB India beyond what is explicitly stated in the PR , at least to AAIB India’s judgement (and I presume amongst others NTSB's as well), shouldn’t lead to any significantly different preliminary observations and conclusions than those made in the PR at this stage.

In other words, there shouldn't be at present other major known/established facts based on the EAFR readouts (2000+ parameters!), but for now not published, that could immediately lead to other observations/qualifications than those made in the present PR .

If there would be, this would actually mean the end of authority of air safety incident investigation and reporting around the globe as we have known it for the past decades.

Last edited by D Bru; 13th July 2025 at 23:16 . Reason: finetuning of argument :)

Subjects (links are to this post in the relevant subject page so that this post can be seen in context): AAIB (All)  AAIB (India)  EAFR  Parameters  Preliminary Report

D Bru
July 14, 2025, 17:26:00 GMT
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Post: 11922380
Good analysis; AvH MN4 thing is an absolute ruse

Originally Posted by YYZjim
The preliminary report narrows things down a lot but not as much as it could have done. The report will have been approved by several people. What we see is their consensus. Why did they choose this version?
The report is written to point the finger directly at: (i) the fuel cutoff switches and (ii) either pilot error or pilot mal-intent using them. The report is not written to point the finger at an electrical or mechanical malfunction.
...... The investigating team already knows. They could have disclosed more of the cockpit conversation, which would be a lot of help to us PPRuNers, but didn't need to. They have let Boeing and the type off the hook and put the blame on the pilots. They have fulfilled the primary purpose of an investigation -- to find out what happened.
Interestingly, they did not disclose whether it was error and mal-intent. Perhaps that is because they couldn't answer the grisly question: which is least worst, from the point-of-view of the airline, the victims' families and future customers?
Two posters above have quoted AvHerald's report that "... India's media reports that the investigation is NOT focusing on a human action causing the fuel switches to appear in the CUTOFF position, but on a system failure." One interpretation of this is that the investigation knows all about the human action and that the system they refer to is the industry's approach to pilot mental heath and well-being.
YYZJim
In the middle of all hamster wheel posts, this one stands out. However, I do take issue only with the last point reported in this no longer reliable AvH website. Concerning the MN4 processor (Ive been looking into this one extensively prior to the preliminary report), according to the AD cited, MN4 board replacement on the GEnx1B was mandated within 12 years of production, engine that is, not A/C. According to the preliminary report AI171 engine 1 was produced 20 May 2012, engine 2 on 20 January 2013. This means that both AI171 engines were with replaced MN4 boards at the time of event, certainly taking into account that both engines have been mounted onto the aircraft in May and March 2025 respectively.

Subjects (links are to this post in the relevant subject page so that this post can be seen in context): AI171  Air Worthiness Directives  Fuel (All)  Fuel Cutoff  Fuel Cutoff Switches  Preliminary Report  RUN/CUTOFF

D Bru
July 14, 2025, 22:27:00 GMT
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Post: 11922550
Originally Posted by GroundedSpanner
Switching off the engines would cut power. (the RAT deployed before they overflew the end of the runway) The HUD would go blank. As would most of the display units. The lighting would change. The hissing of conditioned air would stop. Various 'noises' would cease. The engines sound would change dramatically, and they would feel the deceleration. The one EICAS screen remaining would be generating all sorts of messages. It would be obvious that power was lost.
I cant speak for how long it would take to connect the dots though.
Display and Crew Alert (DCA)/EICAS would indeed receive signal about Fuel Cutoff switches (L&R) position and written to EAFR (source:
https://data.ntsb.gov/Docket/Documen...man-Master.PDF )



Last edited by D Bru; 14th July 2025 at 22:39 .

Subjects (links are to this post in the relevant subject page so that this post can be seen in context): EAFR  EICAS  Fuel (All)  Fuel Cutoff  Fuel Cutoff Switches  RAT (All)  RAT (Deployment)

D Bru
July 15, 2025, 17:41:00 GMT
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Post: 11923115
Hamster wheel diversification (at least an attempt): 787 core system hacking

Inspired by the mention in the PR about a MEL on the \x91core network\x92, I came across the polemics between Boeing and IOActive a few years ago about the alleged vulnerability of 787 core systems to outside interference (hacker attack from within a/c and/or ground), including the highly sensitive CDN module, from where also the fuel cut-off module can be accessed. It\x92s definitely not my specialty, but I thought to flag it in case someone has more informed ideas about this. To my mind it could potentially \x93outshine\x94 intentional crew action. Boeing at the time denied such options, of course. Obviously also in good faith, moreover it seems to be Honeywell &GE code anyhow, but who knows where we are 6 years on.

https://www.wired.com/story/boeing-7...ecurity-flaws/



Last edited by D Bru; 15th July 2025 at 18:10 .

Subjects (links are to this post in the relevant subject page so that this post can be seen in context): Fuel (All)  Fuel Cutoff  Fuel Cutoff Switches  Honeywell  MEL

D Bru
July 15, 2025, 19:20:00 GMT
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Post: 11923194
Originally Posted by Lonewolf_50
A short response to you both:
1. Note that the article was from 2019
2. I am very doubtful that this occurred, beyond estimating the efficacy of any protections Boeing and Honeywell will have come up with since that article was published.
3. Caveat: yes, hackers never sleep .

But I think that you are both grasping at straws, for a variety of reasons…...
Thanks really Lonewolf, I’m for sure not grasping at anything, let alone straws, just testing the sentiments on this one, which (unless I missed something) wasn’t subjected to the hamster wheel as yet, unlike imo far unlikely speculations

Subjects (links are to this post in the relevant subject page so that this post can be seen in context): Honeywell