Posts about: "Air Worthiness Directives" [Posts: 40 Pages: 2]

Not 757 - it was a 767. Second time it happened in about 12 months.

Determined to be an ergonomics problem with the switch layout in the flightdeck.

Early 767s (JT9D and CF6-80A) had a supervisory "EEC" (Electronic Engine Control - Boeing still uses "EEC" to identify what most people call the FADEC on modern engines). The procedure if an EEC 'failed' was to switch both EECs off (to prevent excessive throttle stagger - unlike FADEC, the engine could operate just fine with a supervisory EEC failed).

Problem was that the EEC ON/OFF switch was located on the aisle stand - right above the fuel cutoff switches. Turned out 'muscle memory' was when the pilot reached down there, it was usually to turn the fuel ON or OFF - which is what they did. Fortunately realizing what he'd done wrong, the pilot quickly restored the switches to RUN and both engines recovered. And yes, they continued on to their destination (RAT was still deployed since there is no way to retract it in-flight).

Previous event was with JT9D engines (United IIRC). In that case, only one engine recovered (second engine went into an unrecoverable stall), they simply came back around and did a single engine landing.

Realizing the ergonomic issue, the EECs were relocated to the pilot's overhead (retrofit by AD).

To the best of my knowledge, there hasn't been a repeat of an inadvertent dual engine shutdown since the EEC switches were relocated. It's also very difficult to 'accidentally' move the switches as there is a locking detent - the switch must be pulled out slightly before it can be moved to CUTOFF.

Many GE engines - including GEnx-1B/67s - require microprocessors to be routinely replaced due to soldered joints failing after multiple cycles. There is a 2021 AD that notes "This AD was prompted by an in-service occurrence of loss of engine thrust control resulting in uncommanded high thrust" (I cannot post a link but google: 2021-25491 (86 FR 66447))

I am NOT suggesting that this specific failure mode happened here - for one thing, this would happen to one engine, not both. But on any flight it is possible that a unique set of sensor inputs to occur that are the first time any system has encountered them (example: NATS incident in 2023), and then you need failover & redundancy to keep things working.

The GE Aviation CCS system, which includes thrust management, has up to now flown for 1m flight hours without incident. It would be interesting to hear the perspectives of any engineers familiar with the system.

Let\x92s be careful about absolutes. Emirates 521 and Turkish 1951 are both examples of crews not firewalling the thrust levers despite low energy. The late pitch up could be due to the onset of a stall not an order from the crew.

TCMA is function which can reduce thrust on both engines simultaneously. It had done so in error in the past resulting in an AD. It uses air/ground logic so that it only operates on the ground, however note that at the point of thrust loss the gear is still down without any movement of the gear or doors. I would expect gear retraction to start before that height. Could we imagine an air/ground logic fault inhibiting gear retraction and allowing TCMA, which triggered (for whatever reason!) causing dual thrust loss? I would expect this to be in the realms of a combination of failures shown to be extremely impossible, but\x85

https://www.federalregister.gov/docu...pany-airplanes

Do we know what electronics / avionics have been leaked onto previously that ended up resulting in this AD and its previous iteration?

No. Mainly because it relates to a 10 year old AD.

The software operates regardless of engine type and there are other triggers (not just engagement of thrust reversers, that was just the specific combination of inputs on the ANA flight). As I understand it the EEC compares the engine performance to thrust lever inputs to identify a potential runaway.

Note, the EEC module in GEnx itself is subject to periodic replacement under an AD due to risk of solder failure, but this seems unlikely to be related as would only impact a single engine.

I believe the loud bang that survivor heard was a (BTB) Bus Tie Breaker short.

Based on the comments made by the passenger who travelled on the aircrafts previous sector, speaking about air conditioning that was going on and off, I think a faulty (CAC) Cabin Air Compressors may have contributed.

The B787 FCOM has information about the about only two of four CAC’s being used for ground operation, maybe B787 crew can confirm.

I am curious if the increased electrical demand of the CAC’s shortly after take-off somehow contributed to this potential short.

If such a short did occur then the next question would be how this may influence the engine controls, but given the 248 day AD for electrical issues, it could potentially affect the engines.

I was also surprised to learn that the B787 EICAS actually has a ENG THRUST caution, so not a totally unexplored issue.

The aircraft register posted above does show an air compressor issue, albeit in 2015:

I have now watched a number of "normal" 787 takeoffs online and in none of them does the gear go up super early, certainly not before the 10 seconds or so where this one seems to loose power. I think the flap/gear raising is wrong personally

Still valid Dave. That AD was raised circa post #248 (Search thread for \x93AD\x94)

All four Variable Frequency Generators (2 per engine) going offline at once is too much of a coincidence not to mention that AD.

RAT deployment has been substantiated, which occurs automatically, extension of which takes about 6 secs & would be heard by pax in the cabin as a loud \x93bang\x94 as the leg locks into place.

The sole on-board survivor quote regarding flickering green/white lights (Emergency Exit lights) directly adjacent to his seat 11A, speaks to electrical disruption during the takeoff phase.

If the double engine failure or electrical bus/distribution failure causing loss of thrust occurred for a reason other than the AD mentioned above, the cause will need to be established without delay lest the void is filled with mis-information, fear, uncertainty, & doubt.
The current level of trust in the manufacturer is fragile for good reason.
.
This occurrence will have operators & regulators around the world reviewing their risk assessment models, especially regarding Master Minimum Equipment List (MMEL)/ Defect Deferral Guide (DDG) maintenance relief.

Compliance & maintenance come at a cost.
Lack thereof comes at a far greater & heavier cost.

Would anyone know whether this AD is relevant?

FAA Orders Boeing 787 Inspections to Fix Water Leak Issues

​​​​​​​
I add this note: the background on this AD is here:
https://www.federalregister.gov/docu...pany-airplanes
T28B

Water ingress into the E/E bay is a serious issue. The B744 had this issue in the past causing serious problems, one of which was fortunate to not lead to a loss of the aircraft, on a B744F. The B744 pax aircraft had a number of water problems related to the toilets and the galley. The forward galley on the B742/3s had many issues.

Any large aircraft going through maintenance is interesting to observe the extent of corrosion that occurs near toilets and galleys, and from water lines.

The B777 was not immune to this either. The potable water tank failing caused one of our aircraft to have 6.5 tons of ice accumulating in the underfloor area of the aft cargo hold, which we detected on a preflight walk around as a series of water streams from the drain holes in one area of the aircraft. This was an interesting item for CG, a note on weight, but only affected the electrical services related to the aft cargo systems.

Water accumulations on the B744 came to light at rotate, and took out a lot of electrical services.

My suspicion is some cause such as this will come to light shortly.

The water leak issues with the B787 go back to in service reports in 2014 and before, considered an unsafe condition in 2016, and were covered by AD 2016-14-04. This latest AD is curious as it stems from an administrative oversight in the drawings of the aircraft, that arose on aircraft manufactured from 2018 onwards. 2025-09-12 stands alone related to missing sealant, following the drawing oversight in production. It did not affect all aircraft. The earlier AD, 2016-14-04 was related to water line coupling issues, and is in Service Bulletin B787-81205-SB380009-00 WATER/WASTE - Water System- Potable Water System - Couplings Replacement. It notes on page 21 of 229 the reason for the work

The latest AD and the earlier AD highlight that problems can occur, and have done so in the past. Both of the E/E bays contain stuff that is nice to keep dry and operating, and prior events have shown that multiple system failures can and have occurred when a flood is added to all the black boxes sitting innocently on their racks.

The ADs are not necessarily directly related to the specific cause, they highlight the potential for water damage and that bad stuff happens. In two cases I investigated, the event occurred at rotate. Both were B744's one pax, one F.

Compound, unrelated system failures at rotate? Single cause? Water in the E/E bay.

The amount of flooding that occurs in the toilet cubicles is unfortunate, apparently towels still fit well into toilet bowls, signs are disregarded etc. Coffee grounds block galley drains with monotonous regularity, the planes are only as good as we care for them, and passengers seem to have odd ways of treating the conveniences.

The 787 AD refers to uncommanded movement in a forward direction.

This page https://i1.prth.gr/images/w880/jpg/f...air-india.webp (update: also https://www.protothema.gr/images/w13.../air-india.jpg ) is an alleged summary of the preliminary report, posted by the Greek journal. One suspicious thing is it lists the URL of the report, but that's 404.

I'm posting this so that others can scrutinize the thing.

[update] The more I look at it, the less I believe it. The "Immediate ActionsTaken" and "Next Step" sections could not be in a preliminary report at this stage. Some details are wrong (like the state of the surviving passenger) or made up (the FAA emergency AD 2025-16-51 listed as source is not there: https://drs.faa.gov/browse/ADFREAD/doctypeDetails ).

The Ipeco seats fitted on the 787 (and other airframes) have had numerous problems and numerous Airworthiness Directives to correct issues of uncommanded movement. They are not exclusively electric (i.e. can also be manually adjusted), and presumably there is some sort of pin or locking mechanism to hold them in place and this mechanism (at least in original form or if not corrected) has been known to fail.

The most famous incidents involving the 787 resulted in uncommanded forward movement of the seat, resulting in inadvertent depressing of the yoke and an unexpected pitch down. Other Ipeco seats have been implicated in unexpected forward AND rearward movements. The FAA published an AD just a couple of days ago related to an Ipeco seat doing just that (different model seat not on Boeing planes, FWIW).


You're probably right. Until we start getting reliable information from official sources it's wise to take the theories of a single news outlet with a huge chunk of salt.

A Qantas 747-438 suffered an 'Electrical System Event' when on approach to Bangkok airport on 7 January 2008. The following extracts are taken from the report:

"System malfunctions

Between 0846 and 0852, 4 after passing FL 100 and when the aircraft was turning
onto an extended left downwind leg for runway 01 Right (01R), the EICAS, flight
displays and automated systems showed faults of numerous electrical and other
aircraft systems, including:
\x95 AC buses 1, 2 and 3 not powered
\x95 autothrottle disconnected
\x95 autopilot disengaged
\x95 some fuel pumps not operating
\x95 weather radar not operating
\x95 automatic cabin air conditioning and pressurisation system not operating
\x95 right (FO\x92s) displays blanked
\x95 between three and five pages of messages on the EICAS display
\x95 lower EICAS display blanked.
The CSM contacted the flight crew and advised that the cabin lighting had failed."

"Origin of Generator Control Unit (GCU) faults

Post-incident examination of the GCUs revealed corrosion of the internal circuit
boards in all three of the GCUs that shut down. Analysis of the corrosion materials
observed in GCU 3 showed evidence of long-term exposure to water, including
evidence of acids and carbohydrates that are present in beverages such as coffee,
fruit juice and soft drinks. Those findings indicated a fluid source originating from
the aircraft\x92s galley drains or from spilt liquids in the cabin, and also suggested that
liquid ingress had been occurring over an unknown, but extended period of time."

https://www.atsb.gov.au/sites/defaul.../ao2008003.pdf

This link to the report includes diagrams of where the 747 forward galley was located, directly above the Main Equipment Centre and the E1/E2 racks.

The phtographs show how ineffective the dripshield was in protecting the electrical equipment and the extent of corrosion and damage.

The aircraft was 17 years old at the time of the incident and had completed a C-check approximately three months before the incident.

As FDR notes, this issue seems to have carried over to the 787-8 with Airworthiness Directive AD 2016-14-04 ( https://drs.faa.gov/browse/excelExte...A0058AF6B.0001 )

"We are issuing this AD 2016-14-04 to prevent a water leak
from an improperly installed potable water system coupling, or main cabin water source, which could
cause the equipment in the EE bays to become wet, resulting in an electrical short and potential loss
of system functions essential for safe flight"

AD 2016-14-04 mirrors precisely what occurred to the Qantas 747 on 7 January 2008. It is possible something similar may have occurred on take-off of AI171, with water causing the equipment in the EE bays to become wet resulting in electrical short and potential loss of system functions

Not 757 - it was a 767. Second time it happened in about 12 months.

Determined to be an ergonomics problem with the switch layout in the flightdeck.

Early 767s (JT9D and CF6-80A) had a supervisory "EEC" (Electronic Engine Control - Boeing still uses "EEC" to identify what most people call the FADEC on modern engines). The procedure if an EEC 'failed' was to switch both EECs off (to prevent excessive throttle stagger - unlike FADEC, the engine could operate just fine with a supervisory EEC failed).

Problem was that the EEC ON/OFF switch was located on the aisle stand - right above the fuel cutoff switches. Turned out 'muscle memory' was when the pilot reached down there, it was usually to turn the fuel ON or OFF - which is what they did. Fortunately realizing what he'd done wrong, the pilot quickly restored the switches to RUN and both engines recovered. And yes, they continued on to their destination (RAT was still deployed since there is no way to retract it in-flight).

Previous event was with JT9D engines (United IIRC). In that case, only one engine recovered (second engine went into an unrecoverable stall), they simply came back around and did a single engine landing.

Realizing the ergonomic issue, the EECs were relocated to the pilot's overhead (retrofit by AD).

To the best of my knowledge, there hasn't been a repeat of an inadvertent dual engine shutdown since the EEC switches were relocated. It's also very difficult to 'accidentally' move the switches as there is a locking detent - the switch must be pulled out slightly before it can be moved to CUTOFF.

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.

A case in point is the 2013 Boeing 787 battery fires. After two thermal runaways in 52 000 flight-hours, the root cause was still unknown; however, the FAA nevertheless issued Emergency AD 2013-02-51 grounding every 787 until a modification was available. IMHO a risk where the outcome is catastrophic, even very low probability, would trigger the FAA to issue an Emergency Airworthiness Directive as per their policy.

As I said in a previous post, every day that passes without a EAD suggest the cause was was specific to that aircraft (fuel contamination, maintenance failure, crew error - pick you own theory)

The IIC would bring together the investigators, which include the FAA rep, OEM reps, and try to reach a consensus on the what and is there a technical fix or advisory needed. It could be notice to operators, an emergency AD. This process is not played out in the media. We don\x92t need to know until the IIC releases the information.