A321neo Pitch Warning
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A321neo Pitch Warning
Original design modified and then.....
A321neo operators alerted over 'excessive pitch' anomaly
- 17 July, 2019
- SOURCE: Flight Dashboard
- BY: David Kaminski-Morrow
- London
Airbus has introduced a temporary revision to A321neo flight manuals intended to prevent the possibility of the aircraft reaching excessive pitch attitudes.
The European Union Aviation Safety Agency has disclosed that the revision follows analysis of the re-engined type's elevator and aileron computer.
It has not elaborated on the situation beyond stating that "excessive" pitch could occur under certain conditions and "during specific manoeuvres".
EASA cautions that this could result in "reduced control" of the aircraft.
Airbus has issued temporary revisions to the aircraft's flight manual incorporating operational limitations.
EASA has ordered operators of the A321neo to amend the flight manuals accordingly, within 30 days.
The order covers both the CFM International Leap-1A and Pratt & Whitney PW1100G versions of the aircraft.
Airbus has issued seven relevant temporary revisions to the flight manual, on 21 June and 10 July. EASA says the safety measure is an interim action and could be followed by further requirements.
The European Union Aviation Safety Agency has disclosed that the revision follows analysis of the re-engined type's elevator and aileron computer.
It has not elaborated on the situation beyond stating that "excessive" pitch could occur under certain conditions and "during specific manoeuvres".
EASA cautions that this could result in "reduced control" of the aircraft.
Airbus has issued temporary revisions to the aircraft's flight manual incorporating operational limitations.
EASA has ordered operators of the A321neo to amend the flight manuals accordingly, within 30 days.
The order covers both the CFM International Leap-1A and Pratt & Whitney PW1100G versions of the aircraft.
Airbus has issued seven relevant temporary revisions to the flight manual, on 21 June and 10 July. EASA says the safety measure is an interim action and could be followed by further requirements.
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Excessive pitch attitude can occur with:
CG aft of 34% and
Flight controls "Flare Mode" activated and
Flaps Full and
Large pitch up sidestick inputs (during a GA for example)
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Talked to a former Boeing 737-200 pilot who flew for Silk Air. He was cruising in IMC one night in that part of the world and due to a mix-up in radio frequencies was unaware he was trailing a Boeing 747 freighter about ten miles ahead. Suddenly his aircraft was affected initially by mild turbulence followed by an extremely sharp wing drop to 90 degrees angle of bank. The AP disconnected at the same time. He was able to unload and rapidly regain control and roll wings level. Discussed this incident with a current 737-800 pilot who had a similar experience when being vectored behind an A330 ahead. On this occasion the 737 rolled rapidly to more than 60 degrees angle of bank and the AP disengaged. Weather was VMC and the pilot rolled back to wings level.
When practicing unusual attitude recoveries in the simulator some instructors restrict UA manoeuvers to be within the legal definition of an unusual attitude which among other parameters includes bank angle more than 45 degrees. The perceived reason being fidelity is not assured beyond those figures.
If real aircraft affected by wake turbulence behind a heavy aircraft have finished up at extreme bank angles well beyond official UA parameters, it strikes me as the ostrich head in the sand approach to pretend it will never happen and thus let the unfortunate crew and passengers wear it on the day. Prompt and ideally flawless recovery on instruments is the mark of the true professional pilot. There is no shortage of examples where unusual attitudes have resulted from a wake turbulence encounter. Yet because simulator fidelity may not be guaranteed, we choose not to equip the crew with the instrument flying skills to recover from an extreme wake turbulence encounter. I think that is wrong in principle. No doubt there are other points of view.
Question: With Airbus aircraft, does the inbuilt protection prevent instant roll beyond a specified figure regardless if the aircraft is being manually flown or on autopilot at time of jet upset due wake turbulence?
When practicing unusual attitude recoveries in the simulator some instructors restrict UA manoeuvers to be within the legal definition of an unusual attitude which among other parameters includes bank angle more than 45 degrees. The perceived reason being fidelity is not assured beyond those figures.
If real aircraft affected by wake turbulence behind a heavy aircraft have finished up at extreme bank angles well beyond official UA parameters, it strikes me as the ostrich head in the sand approach to pretend it will never happen and thus let the unfortunate crew and passengers wear it on the day. Prompt and ideally flawless recovery on instruments is the mark of the true professional pilot. There is no shortage of examples where unusual attitudes have resulted from a wake turbulence encounter. Yet because simulator fidelity may not be guaranteed, we choose not to equip the crew with the instrument flying skills to recover from an extreme wake turbulence encounter. I think that is wrong in principle. No doubt there are other points of view.
Question: With Airbus aircraft, does the inbuilt protection prevent instant roll beyond a specified figure regardless if the aircraft is being manually flown or on autopilot at time of jet upset due wake turbulence?
No. If something induces a roll beyond the authority of the ailerons then no protection will prevent it, how could it? Airbus will go to abnormal attitude law if necessary, this is similar to alternate law.
given sufficient aileron authority, the abnormal attitude will not be reached in an Airbus FBW system, as the envelope protection is trying to level the aircraft while the wing is being dropped. In a Boeing, the AP will disconnect as soon as the AP detects insufficient authority, similar to giving the control column a good yank with AP engaged. It'll disengage rapidly. A wing drop due to wake turbulence in an Airbus thus will be slowed down compared to a Boeing. Difference in philosophy.
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From the source cited by Longtimer: "It (Airbus) has not elaborated on the situation beyond stating that "excessive" pitch could occur under certain conditions and "during specific manoeuvres". Isn't that sort of pitch up problem why MCAS was developed by Boeing? What's going on here? Does the A321neo also have a problem with pitch instability?
This is the first I've heard of a possible pitch stability problem with the A-321neo. Let's hope that no lives are lost before the problem can be rectified.
Cheers,
Grog
This is the first I've heard of a possible pitch stability problem with the A-321neo. Let's hope that no lives are lost before the problem can be rectified.
Cheers,
Grog
Trying to compare flight control systems between certain aircraft types is very flawed as some are trying to do.
Anyway, this AD affects L102 STD ELAC software only. Spoke to a Tech Services colleague and if you want to recover the full operating envelope ie not have to apply the AFM TR requirements then you can request approval for the L101 STD software to be reloaded (de-modding the aircraft), not a big deal on the software loadable ELACs which would likely be all that are installed on A321neo aircraft.
Anyway, this AD affects L102 STD ELAC software only. Spoke to a Tech Services colleague and if you want to recover the full operating envelope ie not have to apply the AFM TR requirements then you can request approval for the L101 STD software to be reloaded (de-modding the aircraft), not a big deal on the software loadable ELACs which would likely be all that are installed on A321neo aircraft.
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Here is the goto: https://www.flightglobal.com/news/ar...ch-ano-459718/
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Here is the goto: https://www.flightglobal.com/news/ar...ch-ano-459718/
"halfofrho" elaborates somewhat in his Post #5; however, some of the acronyms he's cited, such as "ZFW/TO/LDG" are not meaningful to me. To my old, "back in the day" understanding, "TO" was short for TakeOff, and LDG was short for LanDinG. I'm embarrassed to admit that I have never encountered the acronym, "ZFW", and the only meaning I've found for it on the ol' interweb was "Zero Fuel Weight". I'm sure that's incorrect, since one would not sustain powered flight for very long at "Zero Fuel Weight". I'd appreciate some help on the meaning of these acronyms since I need all the help I can get ... in most circumstances.
In his Post #11, Station Zero seems to imply that the alleged (by EASA) pitch up problems of the A321neo are due to a software glitch, not to an aerodynamic problem. Has that been confirmed by EASA/Airbus?
Cheers,
Grog
Airbus response to Leeham enquiry:
https://leehamnews.com/2019/07/19/bj...itch-up-issue/
"The issue is an A321neo landing configuration at extreme aft CG conditions and below 100ft only issue, discovered by Airbus and reported to AESA. Violent maneuvers in for instance a go-around in these conditions can cause a pitch up which the pilots can counteract using their side-sticks. No FBW nose downs or similar is commanded, it’s just the FBW doesn’t neutralize the pitch-up (like FBW using the Airbus style flight laws are supposed to do), the pilots have to do it. Airbus has assisted AESA in issuing the AD which restricts the aft CG used in operational landings until the ELAC software is updated."
https://leehamnews.com/2019/07/19/bj...itch-up-issue/
"The issue is an A321neo landing configuration at extreme aft CG conditions and below 100ft only issue, discovered by Airbus and reported to AESA. Violent maneuvers in for instance a go-around in these conditions can cause a pitch up which the pilots can counteract using their side-sticks. No FBW nose downs or similar is commanded, it’s just the FBW doesn’t neutralize the pitch-up (like FBW using the Airbus style flight laws are supposed to do), the pilots have to do it. Airbus has assisted AESA in issuing the AD which restricts the aft CG used in operational landings until the ELAC software is updated."
This is most certainly software rather than Aerodynamics, read the second page of the AD. Group 1 aircraft with L102 ELACs fitted the AFM TR has to be placed in the manual with 30 days. Group 2 aircraft without L102 ELACs fitted the AFM limitation is only applicable once the L102 is installed. This alone means it affects just one ELAC standard.
I’ve not seen the TR but if is below 100ft it will be something to do with the landing aspect of the flight control software. The A321neo from my understanding doesn’t have flare law compared to a CEO, its been replaced with something more akin to direct law where the sidestick input is proportional to output during that flight phase.
I’ve not seen the TR but if is below 100ft it will be something to do with the landing aspect of the flight control software. The A321neo from my understanding doesn’t have flare law compared to a CEO, its been replaced with something more akin to direct law where the sidestick input is proportional to output during that flight phase.
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I wonder what the reason for the change in the flare mode/law and the takeoff law was on the NEO series? For over 30 years it has been working perfectly fine.
If it ain't broke, don't fix it...
If it ain't broke, don't fix it...