Posts by user "bbofh" [Posts: 10 Total up-votes: 15 Pages: 1]

Would not be the first time that an accident has uncovered unintended consequences of a particular fallback configuration that was never able to be checked by either/any of Airbus, McDD or Boeing developmental test-pilots. Thinking of the automatic thrust augment/restoration on the MD81 (regn OY-KHO) that crashed 27Dec91 near Gottrora in Sweden (double engine failure). Design Boffins failed to realize that ice-sheet ingestion (sliding off the wings to be ingested by both rear-mount engines) would not benefit at all from each engine hiccup causing a continual uprating of the other (and vice-versa). To be found/uncovered in a simulator you would have to be testing various pilot inadvertencies (rather than rote expected actions). Then again, don't always believe the outcomes to be seen in a simulator. They don't necessarily faithfully emulate what would happen systems-wise in an aircraft... particularly when it comes to complex materiel failure modes or illogical sequiturs (e.g. MCAS)

So, if such an untestable circumstance were to happen to a competent crew and they were to inadvertently shut-down the wrong engine (and then/were in "clean-up mode":

a. The residual hyds would break the downlocks - but not retract the gear (and it would appear to be still selected down)
b. The alternate flaps might start to retract (gear downlocks not being now "made") once selected, but the slats remain out.
c. the RAT would deploy

The point at which all thrust ceases (and the climb vector flattens/reverses) is easily seen
in the video shot from the 6:30 clock position from about a km away. It's readily apparent.

An engine failure just off the runway after V1 in a fully loaded 787-8 in high ambient temperatures would assuredly have a crew thinking about a "toute suite" shutdown of a misbehaving donk. That's human nature. When the PERF is quite sluggish you will be thinking that a quick clean-up of the situation is certainly called for. That's just human nature unfortunately, particularly when you are under the time compression of dire circumstance (and the airframe is performing like a lame dog, just due to the environmentals and the early failure). I think that what the pilot reportedly said to ATC in his Mayday bears that out as being his instant mindset (quite clearly). Been in that "fools rush in" circ myself. You just have to "sit on your hands" and fly the beast.
But then again, if the RAT was NOT found deployed, then it's a case of the right seat mistakenly sucking in the flaps and slats... and that will do it... whatever the power/TOGA might be.
https://tinyurl.com/4zzkeeud
Rotation +33s
Mayday call +44s, circa 300 ft altitude (ADS-B)
Peak altitude +49s, 625 ft (Flightradar24)
Impact +58s, crash site 1.6 km from runway

Content of AI 787 pilot's distress call:
https://tinyurl.com/2ud2cdyn

https://tinyurl.com/yj58apka

Cannot relocate the actual recording - but it seemed to be a clear and unrushed statement per the above content cited at the two links

The TCMA patent application is at: https://patents.google.com/patent/US6704630B2/en
Quite a simple system (not)
What gets your attention is the fact that you can continue to operate the aircraft without an MMEL entry when one of the two systems (per EEC) that shadow each other... is unserviceable.
As it says: "Typically the aircraft is allowed to operate for a limited period of time with just a single operative processing subsystem."
That 787 was not long out of maintenance.

Content of AI 787 pilot's distress call:
https://tinyurl.com/2ud2cdyn

https://tinyurl.com/yj58apka

Cannot relocate the actual recording - but it seemed to be a clear and unrushed statement per the above content cited at the two links

WHEN something catastrophic happens, like dual engine failure, that then creates a query about any "duality" between two standalone systems that really should have nothing whatsoever in common... except the PF.
Nothing in common? Is that really the case for the 787-8 in the Air India 787 crash?
Look at these three TCMA-related links in the order presented and note the proforma prescriptive caveats in the first two:

https://downloads.regulations.gov/FA...tachment_1.pdf
https://downloads.regulations.gov/FA...tachment_1.pdf
https://patents.google.com/patent/US6704630B2/en

TCMA is designed to detect and accommodate single failures within the EEC/FADEC, preventing a failure from jeopardizing the safe operation of the aircraft.
Implementation:
It involves implementing specific software changes within the engine's control system (EEC).
Regulation:
After some incidents, the design change was mandated by regulators, with a deadline for production aircraft by December 31, 2018, and a retrofit plan for existing aircraft.
Boeing 787 Application:
The TCMA feature is specifically relevant to the 787-8 equipped with GEnx-1B engines, but it may also be applicable to other 787 variants using the same engine type.

The first two links are respectively the request for and FAA affirmation/approval for a GENx-1b software system called TCMA (Thrust Control Malfunction Accommodation). TCMA is the system that precludes High Uncommanded Thrust (HUT) after touchdown by fuel-chopping the engines. It is designed to avoid runway departures. One input is power-lever position. It's then fair to say that (additionally) Air/Ground sensing is quintessentially vital (as to when the system is "armed" and can do this fuel-chop). The third link is the complex description (with diagrams) of the patent application's design functionality of TCMA.
FROM THE 3rd link above:
"​​​​​​The method of the present invention compares the engine's actual power level with a threshold contour defined by the TCMA software package. When the TCMA software package determines that a thrust control malfunction has occurred, based on the engine's power level exceeding the threshold contour, the engine is shut down by the TCMA circuit." It is also notable that it says within the 3rd link that "Typically the aircraft is allowed to operate for a limited period of time with just a single operative processing subsystem."
That Air India 787 was not long out of maintenance.
We are then motivated to ask "what dictates the Air/Ground sensing". Is it just a Weight-on-Wheels microswitch or a RADAlt? (or both? or triplicated micro-switches?). We may then ask: "Did Air India implement the post-5G changes to their RADAlts that concentrated on maintaining their auto-land capability (in the face of 5G interference with RADAlts?) I seem to recall that the FAA's dictums on this pointed out that it was an individual nation's responsibility to both control their 5G frequency spectrums and implement changes to Radar altimeters that would work interference-free in critical phases of flight. What has the Indian regulator done in this regard as the responsible entity? The whole shemozzle, starting with the US Federal Communications Commission (FCC) spectrum allocations, was an ongoing fight between the telecom giants and their getting their new mobile tech to market.

So where are we going with this line of causal reasoning? The only commonality/duality between left and right engines is the software driving the TCMA as monitored by the TCMA software incorporated in each engine's EEC. Most pundits have identified the gear-tilt as evidence that only the centre electrically-driven pump can do the gear-tilt if the engines' other two hyd systems are suddenly both in QUIT mode (which accords also with the instant RAT deployment and loud noise heard by the sole survivor) - and an ensuing transition from climb-out to a deadly sinking and commensurate attitude change for speed maint.
My unavoidable conclusion is that the selection of gear UP and the breaking of the gear downlocks (and WOW sensing and energization of the RADALTs) called upon the TCMA to fuel-chop the engines (via the TCMA functionality in each engine's EEC).
We could start by looking at the No Break Power Transfer (NBPT) tech used in modern airliners. This has led to Gen Control Panel meltdowns in 777's due to GEN contact meltdown. I know of one instance when a 773 was reduced to a RAT only landing enroute and another where a disastrous MEC fire occurred after start on pushback at LHR. A description of the systems glitch often experienced is at the following link. It's quite apparently a "gear-up" hiccup with potential damning consequences for smooth TCMA operation. As to be seen in the quality videos, a fuel-chop provides no real clue (such as engine failure/smoke/fire classically does). An uncommanded "reset" of the two engine's TCMA's upon gear retraction (link below) is trackable to be the sought after "duality" leading to a "both simultaneously quit" engine failure. These momentary electrical glitches and instant "resets" are described in the two links below. Food for reasoned thought?

https://tinyurl.com/yn5ce4tz

https://tinyurl.com/3kkh6n3d

If a gear retraction remains in "tilt", then what does that interregnum status say in response to various systems' interrogations of the WoW sensors? Is it stuck in the Netherworld of betwixt and between ?
Perhaps the safer solution should be an additional circuitry micro-switch feed of all three "up and locked"? (that agrees with the gear-handle).
Also waiting to hear what the 787-8 RADALT status is? Was it ever 5G emanations-proofed?
Is there any software provision for the TCMA to know for sure that the gear is neither up nor down? I would doubt it. Does that uncertainty affect the thrust-lever's positional input?

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?

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.

- at Minus 8 feet (A Significant Disservice to the TCMA's G/A sensing?)
https://asn.flightsafety.org/reports...738_TC-JGE.pdf

The radio altimeter

During the approach, the left radio altimeter system indicated -8 feet , although the aircraft was at a considerably greater height than that. The Board\x92s investigation has not uncovered a reason for this change in the radio height to -8 feet.

A Boeing 737-800 (flight TK1951) operated by Turkish Airlines was flying from Istanbul Atat\xfcrk Airport in Turkey to Amsterdam Schiphol Airport, on 25 February 2009. As this was a \x91Line Flight Under Supervision\x92, there were three crew members in the cockpit, namely the captain, who was also acting as instructor, the first officer who had to gain experience on the route of the flight and who was accordingly flying under supervision, and a safety pilot who was observing the flight.

There were also four cabin crew members and 128 passengers on board. During the approach to runway 18 Right (18R) at Schiphol airport, the aircraft crashed into a field at a distance of about 1.5 kilometres from the threshold of the runway. This accident cost the lives of four crew members, including the three pilots, and five passengers, with a further three crew members and 117 passengers sustaining injuries.

Shortly after the accident, the initial investigation results indicated that the left radio altimeter system had passed on an erroneous altitude reading of -8 feet to the automatic throttle control system (the auto-throttle). In response to this, the Board had a warning sent to Boeing on 4 March 2009. This asked for extra attention to be paid to the \x91Dispatch Deviation Guide\x92 for the Boeing 737-800, which is a manual of additional procedures and warnings for maintenance crews and pilots to consult before the aircraft is flown. This warning, which was added in 2004, states that with radio altimeter(s) inoperative, the associated autopilot or auto-throttle must not be used for the approach and landing......

More GRIST for the electric 787's software Glitch-Mill? (see my prior post above)
Not really "INOP" if it's feeding in -8 feet?
For those unfamiliar with this accident, the RADALT flaw caused the auto-throttle to enter its "flare/retard" mode quite early in the approach and the aircraft stalled into a field well short. I am not sure how one could extrapolate this into a post-take-off TCMA equivalent Ground/Air misadventure. Radar altimeters have considerable authority when it comes to CAT 3 ILS ops. It has an interface with the EEC, but to what extent?

During a post-flight inspection, engineering discovered that all four engine fan cowl static ports on the 787-9 aircraft were covered with tape. This oversight, which occurred despite the aircraft's flight being uneventful, reduced redundancy in the engine electronic control system. Assuming here that only one engine was affected by taping.
https://www.atsb.gov.au/media/news-i...d-static-ports
"While the flight was uneventful, the covered ports meant that redundancy for the engine electronic control system was reduced;"

Not sure whether this aspect has been covered in respect of the Air India accident? Obviously did not adversely affect or alarm this QANTAS 787 freighter flight to the USA. If it had been a passenger-carrier, would the pax have noticed?
However the pitot obstruction/covers and static port taped/NZ A320 not taped (for a high-pressure hose wash) did kill many in past crashes.
A Lufthansa 777 Freighter's Static port left disconnected from its ADM nearly did. AoA damage by ramp vehicles have also killed many (Abidjan A310-300): Kenya Airways Flight 431 stick-shaker on rotate.
Any port in icing, a dust- or a rain-storm can become a portal to Paradise. Water ingested/sucked into a static system once gave me a very interesting ride/recovery challenge once above FZLvl in total IMC.
For maintainers, it's the ImPORTance of being earnest. Per the photo at the link above, what is a "barricade tape?"

Was there a follow-up "probe"? This raises a few flags. Blanks are everywhere on an aircraft parked for a few days or weeks. You need to develop a "blank stare". We'd have to assume that the ATSB pulled and reviewed the QF 787 recorders to ascertain the effect upon critical engine data. Yet maybe not? Doing so would have grounded the next freighter flight ex the US. But were they (later in OZ) able to post-flight compare the two engines comparative take-off and enroute/approach data? If not/why not? - and if so, what may they have found? Did the engines report anything of consequence via ACARS enroute? Are those engine cowl ports critical in any operational respects? IS/Was the tape used intentionally porous? Two totally different types of tape were used on the QF787.
Perhaps of greater significance: Are the various I/O plugs and ports (that festoon the EEC) prone to a mis-connect/disconnect?. I would imagine that an ECAM/EICAS would raise a red flag on some/most? Would a poorly-made connection or a duff-plug on an EEC severely affect its arcane functionalities and outputs?
Could the Air India event indicate yet another format outcome of pitot/static input error blight with the EEC. I'm sure that it must have those inputs. Like any port or orifice on an airplane, I'm sure that the EEC's sensors could well be partially or wholly internally obstructed. I've not heard of any such incident on another type being sheeted home to such an intrusion.

Covered at:
Dreamliner preflight error, ground and tech crew?

"The engine electronic control (EEC) uses the ambient air pressure data from the ADRS for engine control algorithms, engine thrust calculations and to optimize engine performance. The fan cowl static port air pressure data is only used when an EEC determines that the ADRS data is unreliable. Where no ambient pressure data is available, the EEC assigns a failsafe mode for continued engine operation."

"It would have set numerous FADEC maintenance faults and the "L/R ENG CONTROL" EICAS messages. However the ENG CONTROL messages are inhibited above 80 knots, so the crew would not have seen them until they landed, and we don't expect the flight crew to check CMC faults (I don't think there is anything that would prevent it, but unlikely there would be any reason for them to look).
Engine operation may have been a bit 'abnormal' - not up-to -speed on the Trent 1000 Air Data Logic, but the general rule is if both engine sensors agree but disagree with aircraft, the system defaults to the engine sensors to protect engine-to-engine isolation. Of course when engine sensed Pamb became greater than the P total, it likely would have faulted everything and gone to some default failsafe value."