Page Links: First Previous 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 Next Last Index Page
nachtmusak
2025-06-19T01:00:00 permalink Post: 11905642 |
My understanding of altitude capture is that the autopilot will automatically adjust both thrust and pitch to intercept the requested altitude. However to my eyes there is very little pitch adjustment in the CCTV video of the plane taken from behind, until the very end of the video when it pitches up somewhat (obscured by buildings, more visible in the smartphone video). Please correct me if I'm wrong but I'd have thought that if the autopilot was trying to capture a very low altitude it would start pitching down (quite noticeably!) to do so, not remain at what looks like 10+ degrees nose-up. I honestly struggle to reconcile what I'm looking at in the video with an attempt to level off at 0ft, 200ft, or any of the other mentioned low-level altitudes. Also maybe I'm missing something 787-specific but generally doesn't the autopilot have to be activated for the aircraft to automatically attempt to capture the pre-selected altitude? That was the case in this incident involving a Dash 8 and a target altitude of 0 feet that I am reading about ( https://www.gov.uk/aaib-reports/aaib...-dash-8-g-ecoe ). I'd have thought the PF would still be hand-flying the departure at the point that things went wrong, considering that the gear hadn't even been retracted yet... 2 users liked this post. |
bbofh
2025-06-19T01:30:00 permalink Post: 11905658 |
The 787-8 landing gear retraction is primarily hydraulic, using the center hydraulic system for the main operation. However, the alternate gear
extension
system utilizes a dedicated electric pump to pressurize fluid from the center hydraulic system for gear extension. Obviously due its size and weight and staged retraction, the effort required to raise and stow the gear greatly exceeds that required for extension.
The main gear retraction/extension is controlled by the center hydraulic system. It is apparent that the hydraulics failed when the engines shut down after breaking the down-locks and leaving the Main Landing gear bogeys in the tilt position, ready for a next step internal stowage and door closure (that was now never to happen). It is therefore apparent that the dual engine failure and consequent automated RAT extension was precipitated by this gear selection or retraction cycle and thus likely to be either WoW micro-switch or 5G Radar altimeter-effect associated. Due to accumulator depletion, the electric pump load would have spiked to replenish it. This may have precipitated the dual engine shutdown due to an unfiltered electrical surge affecting the Ground/Air microswitches (or a local 5G transmission affecting the RADALT) and resetting the TCMA. The RADALT? Another plausibility? Because of the furore over a spasticated frequency allocation by the US FCC, the US FAA had finally “bought in” and declared that individual nations and their airline operators were responsible for their own 5G frequency spectrum allocations and for taking essential steps to ensure mitigation of the interference effects upon aircraft automated landings and other critical systems caused by their own national approved 5G spectrum decisions. It was admittedly a situation calling for extensive modifications to (and shielding for) the three radar altimeters fitted for redundancy considerations to all modern airliners... for Category 3 ILS approach and landing in zero/zero visibility conditions. The RADALT also features in many air-ground sensing applications. (eg the 747-8). This was an unusual FAA “passing of the buck” to manufacturers such as Honeywell etc. (to sort out with client operators). But then again, it was not the US FCC’s right to dictate the specific 5G frequencies internationally. These spectrum allocations now vary over the wide selection of 5G phones available (and also nationally). 5G Radar Altimeters constitute a part of the ground/Air sensing that changes the TCMA from ground mode (able to fuel-chop engines) to the air mode (inhibited from doing so)... Ground activation is acceptable ...where fuel chopping of uncommanded thrust can prevent runway sideways excursions or runway length overruns. The question now becomes: “Is it more (or less) safe having an automated fuel-chopping capability on BOTH your left and right, rather than leaving it to the pilot to react via his center console fuel cut-off switches... in the unlikely event of a runaway engine after landing (or during an abandoned take-off)? 5G Frequency Variations The frequencies of 5G phones vary nationally based on the frequency bands allocated and used by different carriers in each country. In the United States, for example, carriers such as AT&T, Verizon, T-Mobile, and others use a combination of low-band, mid-band, and high-band 5G frequencies. Low-band 5G frequencies typically range from 600 MHz to 1 GHz, mid-band 5G frequencies range from 1.7 GHz to 2.5 GHz, and high-band 5G (mmWave) frequencies start at 24 GHz and go up to 40 GHz . These frequencies are allocated by regulatory bodies such as the Federal Communications Commission (FCC) and can vary between countries based on spectrum availability and regulatory decisions. In other countries, the specific frequency bands used for 5G may differ, leading to variations in the frequencies supported by 5G phones. Additionally, the deployment of 5G networks can also influence the frequencies used, with some countries focusing more on sub-6 GHz bands while others prioritize mmWave technology. 5G interference? It may be an avenue worth exploring? 6 users liked this post. |
Pinkman
2025-06-19T07:55:00 permalink Post: 11905808 |
I too watched his explanation with interest. However I believe he is not considering the possibility of C hydraulics failure prior to wheels lift-off, because I speculated this is the more likely reason the gear trucks remained in a forward tilt position,
see my earlier post here
. I believe the crew never got as far as calling for the Gear Up... many possible reasons for this, flickering instrument screens during the electrical switchover to battery power, flurry of EICAS messages. For any of those things happening around time of rotation, I would be advocating delaying gear up decision until safely climbing away above AA and as a crew you have chance to discuss safest course of action. Not putting the gear up shouldn't kill you.
Point is the gear truck tilt is a clue of a C hydraulics failure, but we cant determine if hydraulics failed prior to wheels off runway or prior to gear doors opening in retraction sequence. |
Aerospace101
2025-06-19T08:27:00 permalink Post: 11905828 |
Last edited by Saab Dastard; 19th Jun 2025 at 10:58 . Reason: Reference to deleted post removed 1 user liked this post. |
FullWings
2025-06-19T08:44:00 permalink Post: 11905837 |
Thank god someone has pointed out the absolute cobblers some people who claim to have some experience of this type (and other completely unrelated types) have been spouting. And if anyone else wants to erroneously compare the 757/767 low level EPR ALT CAP scenario , that keeps the TO thrust on, it doesn\x92t reduce it! This is truely one of the worst of these accidents threads I\x92ve read in a long time, I pity the mods.
2 users liked this post. |
thnarg
2025-06-19T09:45:00 permalink Post: 11905876 |
I wasn\x92t going to jump on the hamsterwheel, but\x85
Those takeoff FMA annunciations look similar to all previous Boeings and I think all of us would have slammed the thrust levers forward as soon as the speed and climb rate started decaying, where presumably they would have stayed in THR HOLD no matter what the TCMA/FADECs were doing? Would \x93top of the amber band\x94 or equivalent have been less than RAT stall speed? If the RAT stalled as the speed decayed depriving the pilots of all control, that\x92s a horrible end. Those of us who have had to perform non-normal landings at least had a runway or clear area to aim for, and the means to do it. They didn\x92t. Which perhaps explains why we\x92re all honouring the crew by trying to understand what happened, even with the stupidest posts about autopilots etc. Jumping off the hamsterwheel now\x85 |
Aerospace101
2025-06-19T10:04:00 permalink Post: 11905882 |
It's possible the RAT was not providing correct power in the last moments, remember RAT provides Hydraulic (C system flight controls only) and Electrics. The evidence is the spoiler pair deflection behind the engines prior to impact. See earlier post . . That specific spoiler pairing is only controlled by electrical power (directly connected to pilot control column). We should see other flight control deflections if the RAT was powering hydraulics. In the final moments I would speculate the flight controls had only emergency electric power from the battery. 5 users liked this post. |
EDML
2025-06-19T10:22:00 permalink Post: 11905894 |
The evidence is the spoiler pair deflection behind the engines prior to impact.
See earlier post
. . That specific spoiler pairing is only controlled by electrical power (directly connected to pilot control column). We should see other flight control deflections if the RAT was powering hydraulics. In the final moments I would speculate the flight controls had only emergency electric power from the battery.
Furthermore: The small hydraulik pump of the RAT only powers some of the flight controls that are powered by the center hydraulic system. The ones powered by the engine driven pumps will not work once the engine(s) failed. 1 user liked this post. |
Someone Somewhere
2025-06-19T10:54:00 permalink Post: 11905921 |
I still think that the small black area is the back of the engines visible through the small gap of the extended flaps.
Furthermore: The small hydraulik pump of the RAT only powers some of the flight controls that are powered by the center hydraulic system. The ones powered by the engine driven pumps will not work once the engine(s) failed. This doesn't apply if the pumps are depressurised by a fire handle, or to allow easier engine relight. |
Aerospace101
2025-06-19T10:58:00 permalink Post: 11905922 |
2 users liked this post. |
LGB
2025-06-19T11:18:00 permalink Post: 11905939 |
THR REF/VNAV SPD
Does a Boeing 787 go from HOLD TO/GA to THR REF/VNAV SPD at 400' AGL/AAE, like older versions of the Boeing?
If so, what if the WoW stayed in ground mode, for whatever reason, how would that affect 1) Retraction of the landing gear (it didn't retract, as obvious in videos released) 2) The transition from HOLD to THR/REF at 400' (they reached just barely over 400' AGL before leveling, then descending) I am also thinking that Air India would follow Boeing procedures in that the left seat pilot will move their right hand away from the thrust levers at V1, and thus, at 400', the thrust levers are not guarded or monitored? Even if thrust levers were pushed forward, is there some kind of logic related to FMC and-or FADEC or other involved systems, which regardless of thrust lever position commands IDLE thrust to the engine? Remember that Airbus accident where the aircraft thought it was landing, while the pilots wanted full thrust, and they crashed into a small forest because some kind of idle is all they were afforded by the system? If the engines of this 787 thought it was in the rollout or final part of the flare, it might also command thrust levers to idle? This does not explain the RAT, though, unless there is some weird combination of software working against each others logic. Had the engines failed by some really random, odd reason, like birds, fuel contamination-vapor-starvation or such, wouldn't there be at least a slight bit of roll or yaw visible? Even with TAC or whatever they have on the 787, I would think even a 1 second difference in thrust reduction between the engines, a hint of yaw or roll should be visible ... Thoughts, especially by someone who flies the 787? Last edited by LGB; 19th Jun 2025 at 11:36 . Reason: Updates and more thinking .. 1 user liked this post. |
Roo
2025-06-19T11:19:00 permalink Post: 11905941 |
The RAT is a small turbine that operates an electrical generator and a hydraulic pump.
“A ram air turbine (RAT) pump converts mechanical input power into hydraulic power for the center system flight controls. The RAT is in the right, aft wing-to-body fairing.” Last edited by Saab Dastard; 19th Jun 2025 at 12:11 . Reason: Quoting deleted post |
JPI33600
2025-06-19T11:34:00 permalink Post: 11905954 |
The RAT is an electrical generator, not a hydraulic pump. How many times does this need to be said?
This service bulletin provides instructions to replace the Ram Air Turbine (RAT) Pump and Control Module
Assembly to prevent failure of the hydraulic pump at low air speed. The RAT Assembly provides an emer- gency source of electrical and hydraulic power for the primary flight control if the left, center and right main hydraulic systems fail. Loss of the RAT Pump and Control Module Assembly could lead to loss of control of the airplane when emergency power from RAT Assembly is needed. If this change is not incorporated on the RAT Assembly and hydraulic power is lost on the left, right and center main hydraulic systems, then the RAT Assembly may not provide sufficient hydraulic power which could result in the loss of many critical control systems that are necessary for safe flight. ![]() 787 RAT hydraulic pump location Last edited by Senior Pilot; 19th Jun 2025 at 11:40 . Reason: Image 6 users liked this post. |
Someone Somewhere
2025-06-19T12:25:00 permalink Post: 11905981 |
RAT types vary significantly by aircraft family. The 777 and 787 types (along with most BBD aircraft) are indeed dual hydraulic-electric (lifted from the 2010 FCOM available online):
![]() Other types are different. The A350/A380 do have an electric-only RAT with adequate electric flight controls. The A320/A330 have a hydraulic-only RAT with a separate hydraulic-driven electrical generator. The 757/767 are similar except the generator is optional. Some used an electric RAT to drive an electric hydraulic pump. Be careful when attempting to transfer knowledge from one type to another. Last edited by Saab Dastard; 19th Jun 2025 at 15:45 . Reason: Reference to deleted post removed 10 users liked this post. |
Capn Bloggs
2025-06-19T12:37:00 permalink Post: 11905990 |
The RAT (unverified source):
1 user liked this post. |
LGB
2025-06-19T13:28:00 permalink Post: 11906021 |
Here we go again.
They are not "ground-only" levers, Why do you and MagPlug have this idea that the PF would not place their hand back on the thrust levers after the gear up call, or at least be guarding the throttles just in case, heaven forbid, they started to roll back? ... It is noteworthy that the point that thrust is lost, is very close to 400' AGL, where at least on some other Boeing aircraft, HOLD changes to THR REF. It seems coincident with this height, the thrust is lost. And lost so closely, between the engines, that there seems to be neither yaw nor roll to see in the videos. Does the 787 have a system for asymmetric thrust, like the TAC on the 777? Even if it does, would the aircraft still not show at least a slight bit of yaw/roll before such a system kicked in, unless both engines lost thrust near simultaneously? If all AC and DC was lost in an instant, then that would be within a split second for both engines, via the FSOVs, rendering FADEC powerless. If anything like birds, bad fuel, lack of fuel, vapour or all other things like that mentioned, the chances of no yaw seem only remotely possible. Then there is the RAT and the landing gear. Any indication from known videos as to what height the RAT comes on, around 400' AGL, or well before reaching 400' ? |
bbofh
2025-06-19T13:40:00 permalink Post: 11906028 |
Hidden
Has anybody the skill, knowledge, hands-on system familiarity or diagrammatic access to examine the
Ground/Air, gear-handle, gear doors gear position lights emergency extension, Throttle lever position and W.o.W. circuitry - in any sanguine detail? What for? It could possibly reveal some abstract relationship flaw between microswitches, RadAlts, and/or even shock-strut extension or travelling gear or door position that allows for an effect dependent upon the high ambient temperature-dictated interrelationship? Why ferret thusly? Many latent gremlins reside in complex circuitry. It is very hard to get away from the logical proposition that gear selection / travel (or possibly the earlier G/A transition) predicated the double flame-out and RAT deployment. The 787 was always ever described as an electric airplane and I see that as a harbinger - not of doom, but of inspiration. I personally have never trusted electro-mechanical devices such as micro-switches... or for that matter, solenoid-operated relays. Or travelling further afield, those fiendish devices called circuit-breakers (thermal or otherwise). And a description of an RCD as a "safety switch" sends a shiver up my spine. They are really just a potential annoyance and an ongoing expense. As I have found again and again, their reliability and test functions are no guarantee of serviceability. A ceiling fire cured me of that fantasy. You might also reflect deeply upon the following observation: From the outset, this electric airplane had electrical issues. The Lithium Ion battery fires were never really resolved. They just re-housed it in a very stout titanium box - one that can only breathe a fiery breath overboard I believe... as if it was a slice of thorium always threatening to turn into lethal plutonium. The 787 designers convinced the regulator that their electric airplane could only become an industry steed if it had the power of such a battery. Unsure whether there's since been any ongoing issues (or if there had been, would it become a "known" event - now that this malignant potency has been robustly "contained"?). So what happens when a fire breaks out inside that titanium box and all its volts are discharged overboard? Are any battery-powered holding relays released at that point? i.e. is there a damning catch? Pandora's stout box may prove to be a gift-horse. Last edited by bbofh; 19th Jun 2025 at 15:42 . |
OldnGrounded
2025-06-19T13:59:00 permalink Post: 11906042 |
OK, enough quick, consecutive, posts from me for now. Off to do required chores. |
Surlybonds
2025-06-19T14:08:00 permalink Post: 11906052 |
Dunno, the discussion around the switch as a failure point looks spurious to me. With that used to support the idea that a possible engine shutdown was due to the master fuel valve closing.
I don\x92t really buy that, since we don\x92t know at this stage whether the engines did in fact fully shutdown, or were commanded to spool down to idle, or other lower thrust setting, both of which would produce the same result. Thoughts ?. 3 users liked this post. |
Seamless
2025-06-19T14:08:00 permalink Post: 11906053 |
I have read most of the thread (old and new). As a lawyer working in forensic investigations, I am constantly involved in problem-solving. My field of work also includes complex investigations related to insolvencies, which almost always require an analysis of the causes behind a specific, established outcome. In doing so, I naturally also have to deal with probabilities. However, it often turns out that the most likely or plausible explanation does not reflect what actually happened.
Many of the considerations I’ve read fail because the simultaneous failure of both engines is extremely unlikely, leading to a constant search for higher-order causes. It was suggested that an incorrect altitude setting led to an early thrust reduction. However, this would not explain the deployment of the RAT (Ram Air Turbine), especially since the thrust could have been readjusted. FADEC and TCAM are highly redundant systems, and TCAM failure is unlikely due to WOW (Weight on Wheels) logic, making a simultaneous engine failure after VR equally improbable. With that said, and with regard to my question concerning the AD that relates to the fuel control switches (FCS), my thought—and it was nothing more than that—was that their activation becomes more probable if it can occur accidentally. That’s how I came across SAIB: NM-18-33. Another user then brought up an iPhone. That notion would, of course, be dramatic—but how unlikely is it really that after approximately 10,000 actuations between December 2013 and June 2025, the two FCS no longer lock perfectly? Considering all of this, I find it quite conceivable that the A/T slightly reduced thrust in the first seconds after VR (e.g., if an incorrect target altitude had been entered) and that an object lying between the thrust levers and the FCS could have pushed the FCS into the “Off” position. Due to the buttons on top of the switches, which provide some resistance, it’s even possible that the object both pulled and pushed them. But all of this is speculation. The investigation report will bring clarity. Even if my theory is not confirmed, I still believe that the positioning and mechanism of the FCS are suboptimal. Switches of such critical importance should be better protected, and movements in the area in front of the switches (like reducing thrust) should not follow the same direction as shutting off the fuel supply. A different switching direction alone would provide more safety—especially considering that the FCS are protected laterally by metal plates. 5 users liked this post. |
Page Links: First Previous 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 Next Last Index Page