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BoeingG
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Posts: 140
Joined: Thu Sep 01, 2016 9:01 pm

A350 flight control airworthiness directive

Thu May 05, 2022 4:25 pm

https://ad.easa.europa.eu/ad/2022-0079-E

In brief: “An occurrence was reported where the PRIMary flight control computers (PRIMs) indicated that both elevator actuators were considered faulty. Subsequent investigations identified incorrect instructions had been implemented with the introduction of the PRIM P13 standard, that is part of the Flight Control and Guidance System (FCGS) X13 standard installed in production aeroplanes through Airbus mod 115496, and in-service aeroplanes through Airbus SB A350-42-P017. This condition, if not corrected, could lead to loss of control of the elevator surfaces, possibly resulting in loss of control of the aeroplane.”

Thoughts? This, when contextualized by the MAX hysteria, the QR dispute, and the XLR fuel tank woes, will not bode well for AB.
 
Avatar2go
Posts: 950
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Re: A350 flight control airworthiness directive

Fri May 06, 2022 4:12 am

Looks like similar to the MAX & MCAS, the AD is to update the AFM with temporary revisions, along with MMEL with temporary restrictions, until further instructions on updating the firmware to resolve the issue.
 
BoeingG
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Re: A350 flight control airworthiness directive

Fri May 06, 2022 11:59 am

Avatar2go wrote:
Looks like similar to the MAX & MCAS, the AD is to update the AFM with temporary revisions, along with MMEL with temporary restrictions, until further instructions on updating the firmware to resolve the issue.


I am not well-versed on the technicalities. You are not saying grounding is imminent, yet you liken it to the MCAS saga. How severe is the issue?
 
Avatar2go
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Re: A350 flight control airworthiness directive

Fri May 06, 2022 12:04 pm

BoeingG wrote:
Avatar2go wrote:
Looks like similar to the MAX & MCAS, the AD is to update the AFM with temporary revisions, along with MMEL with temporary restrictions, until further instructions on updating the firmware to resolve the issue.


I am not well-versed on the technicalities. You are not saying grounding is imminent, yet you liken it to the MCAS saga. How severe is the issue?


Just pointing out that the remedy proposed by EASA is similar to that proposed by the FAA after JT610. Alert pilots & airlines of the issue and insert pages in the manuals, while awaiting a firmware fix. Grounding was not imminent at that time for the MAX either.
 
Flow2706
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Re: A350 flight control airworthiness directive

Fri May 06, 2022 12:05 pm

Im not an engineer, but ADs are quite common for all aircraft types. I don’t think this is a critical issue, a fix will be developed and rolled out on the fleet. Most of the safety risks addressed by ADs are quite unlikely, but the application of the AD is still necessary to maintain the high level of safety desired in aviation. If there was a really urgent safety issue identified, the AD would probably be issued as an EAD, Emergency Airworthiness directive.
 
BoeingG
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Posts: 140
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Re: A350 flight control airworthiness directive

Fri May 06, 2022 12:10 pm

Flow2706 wrote:
Im not an engineer, but ADs are quite common for all aircraft types. I don’t think this is a critical issue, a fix will be developed and rolled out on the fleet. Most of the safety risks addressed by ADs are quite unlikely, but the application of the AD is still necessary to maintain the high level of safety desired in aviation. If there was a really urgent safety issue identified, the AD would probably be issued as an EAD, Emergency Airworthiness directive.


Is it common for ADs to address critical flight controls?
 
FluidFlow
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Re: A350 flight control airworthiness directive

Fri May 06, 2022 12:17 pm

BoeingG wrote:
Flow2706 wrote:
Im not an engineer, but ADs are quite common for all aircraft types. I don’t think this is a critical issue, a fix will be developed and rolled out on the fleet. Most of the safety risks addressed by ADs are quite unlikely, but the application of the AD is still necessary to maintain the high level of safety desired in aviation. If there was a really urgent safety issue identified, the AD would probably be issued as an EAD, Emergency Airworthiness directive.


Is it common for ADs to address critical flight controls?


If we regard flight controls as the devices to change the location within the three dimensional space I am pretty sure all of them are critical and you do not want any of them to fail. Taking this into account there are hundres of such ADs.

Just as en example: There are 301 publications from EASA regarding Ailerons

https://ad.easa.europa.eu/search/simple/result/

IMHO a pretty critical part and part of the flight controls.
Last edited by FluidFlow on Fri May 06, 2022 12:19 pm, edited 1 time in total.
 
Flow2706
Posts: 338
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Re: A350 flight control airworthiness directive

Fri May 06, 2022 12:18 pm

BoeingG wrote:
Flow2706 wrote:
Im not an engineer, but ADs are quite common for all aircraft types. I don’t think this is a critical issue, a fix will be developed and rolled out on the fleet. Most of the safety risks addressed by ADs are quite unlikely, but the application of the AD is still necessary to maintain the high level of safety desired in aviation. If there was a really urgent safety issue identified, the AD would probably be issued as an EAD, Emergency Airworthiness directive.


Is it common for ADs to address critical flight controls?

Quite common, yes. Or structural issues: „Cracks were found in the horizontal stabilizer (HS) centre box (CB) top skin of an A330 aeroplane in pre-mod 41330 configuration. The cracks were initiated at the upper flange corner at rib 3 rear spar area on left hand side of the CB.
This condition, if not detected and corrected, could lead to reduced structural integrity of the HS CB of the aeroplane.“
For one for the 787 is to mitigate explosion risks: „The FAA is issuing this AD to address ignition sources inside the fuel tanks and increased flammability exposure of the fuel tanks caused by latent failures, alterations, repairs, or maintenance actions, which could result in a fuel tank explosion and consequent loss of an airplane.“ There are many more similar ADs in the database…as you see they are quite common…
 
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armagnac2010
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Re: A350 flight control airworthiness directive

Fri May 06, 2022 12:50 pm

ADs are issued to correct potential unsafe condtions. So yes, you will should AD on flight controls primary structure propulsion system etc.

And at the risk of stating the obvious, an AD before an accident is totally different from an AD issued after an accident. Or worse, after 2 fatal accidents.
 
Avatar2go
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Re: A350 flight control airworthiness directive

Fri May 06, 2022 1:07 pm

armagnac2010 wrote:
ADs are issued to correct potential unsafe condtions. So yes, you will should AD on flight controls primary structure propulsion system etc.

And at the risk of stating the obvious, an AD before an accident is totally different from an AD issued after an accident. Or worse, after 2 fatal accidents.


An AD is an AD, regardless of circumstances. They address unsafe conditions of all kinds. They represent actions required to avoid potential future incidents & accidents.

This AD alerts pilots and airlines of the potential for false positive indication of elevator actuator failure, until such time as a permanent firmware fix is available. Thus forewarned, pilots should be able to recognize the issue and interpret it correctly.
 
WayexTDI
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Re: A350 flight control airworthiness directive

Fri May 06, 2022 2:31 pm

BoeingG wrote:
Avatar2go wrote:
Looks like similar to the MAX & MCAS, the AD is to update the AFM with temporary revisions, along with MMEL with temporary restrictions, until further instructions on updating the firmware to resolve the issue.


I am not well-versed on the technicalities. You are not saying grounding is imminent, yet you liken it to the MCAS saga. How severe is the issue?

Aircraft type grounding are extremely rare. In the past 70 years, we've had (going backwards):
- 737 MAX after the MCAS issues;
- 787 after the Battery fires;
- Concorde after the AF crash;
- DC-10 after the AA crash in Chicago;
- Comet after in-flight break-ups.
Whereas ADs are issued on a regular basis.
 
Staralexi
Posts: 31
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Re: A350 flight control airworthiness directive

Fri May 06, 2022 3:00 pm

737 400 was grounded in 1989 after Kegworth crash
 
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scbriml
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Re: A350 flight control airworthiness directive

Fri May 06, 2022 4:12 pm

BoeingG wrote:
Thoughts? This, when contextualized by the MAX hysteria, the QR dispute, and the XLR fuel tank woes, will not bode well for AB.


Sounds liKe wishful thinking.
 
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FiscAutTecGarte
Posts: 824
Joined: Tue Dec 24, 2019 6:40 pm

Re: A350 flight control airworthiness directive

Fri May 06, 2022 4:32 pm

BoeingG wrote:
Thoughts? This, when contextualized by the MAX hysteria,
, anti-airbus sentiment,
BoeingG wrote:
the QR dispute, and the XLR fuel tank woes, will not bode well for AB.


There, fixed it for you. :roll:
 
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zeke
Posts: 17348
Joined: Thu Dec 14, 2006 1:42 pm

Re: A350 flight control airworthiness directive

Sat May 07, 2022 3:15 pm

I had made a long post yesterday on how this worked, it seems to have been removed.

Pitch control on the A350 comprises of 3 different systems, the THS, the left elevator, and the right elevator. Each element is controlled by a different set of quad redundant computers (combinations of different PRIMS and SECs). The surfaces are powered by different combination of hydraulic systems.

There is no single computer, single sensor issue here like MCAS.

I suspect the MEL aspect of this to prevent dispatch without SEC2, and the flight manual side of things is a procedure to ensure redundancy is maintained even in the event of a failure of one of the PRIMs.
 
GalaxyFlyer
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Re: A350 flight control airworthiness directive

Sat May 07, 2022 10:58 pm

The Gulfstream G500/600 has a flight control AD note limiting the landing wind to 15 knots from any direction, effectively grounding the fleet of circa 200 planes.
 
11C
Posts: 424
Joined: Mon Jun 17, 2019 2:25 pm

Re: A350 flight control airworthiness directive

Sun May 08, 2022 12:03 am

BoeingG wrote:
Flow2706 wrote:
Im not an engineer, but ADs are quite common for all aircraft types. I don’t think this is a critical issue, a fix will be developed and rolled out on the fleet. Most of the safety risks addressed by ADs are quite unlikely, but the application of the AD is still necessary to maintain the high level of safety desired in aviation. If there was a really urgent safety issue identified, the AD would probably be issued as an EAD, Emergency Airworthiness directive.


Is it common for ADs to address critical flight controls?

Yes.
 
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HKAusFlyer
Posts: 37
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Re: A350 flight control airworthiness directive

Sun May 08, 2022 6:10 am

zeke wrote:
I had made a long post yesterday on how this worked, it seems to have been removed.

Pitch control on the A350 comprises of 3 different systems, the THS, the left elevator, and the right elevator. Each element is controlled by a different set of quad redundant computers (combinations of different PRIMS and SECs). The surfaces are powered by different combination of hydraulic systems.

There is no single computer, single sensor issue here like MCAS.

I suspect the MEL aspect of this to prevent dispatch without SEC2, and the flight manual side of things is a procedure to ensure redundancy is maintained even in the event of a failure of one of the PRIMs.


Agree. Plus there are three PRIMs and three SECs.
 
SEU
Posts: 469
Joined: Wed Mar 13, 2019 7:21 pm

Re: A350 flight control airworthiness directive

Sun May 08, 2022 12:45 pm

Absolutely nothing close to MCAS or the Boeing issues - some seem to almost want something like MCAS to happen to Airbus it seems
 
Avatar2go
Posts: 950
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Re: A350 flight control airworthiness directive

Sun May 08, 2022 2:09 pm

The issue appears to be the software load for the primary computers, which makes them all contributors. The essential thing is for pilots to be forewarned that the indication is false, if it should occur, and to have remedial actions spelled out.
 
Jungleneer
Posts: 133
Joined: Sat Nov 09, 2019 1:56 am

Re: A350 flight control airworthiness directive

Sun May 08, 2022 2:34 pm

This seems like that some allowed dispatch conditions on the MMEL combined with a software design issue were on the verge of a single or probable fault to achieve a complete loss of control scenario.

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