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Has everyone suddenly forgotten how to build airplanes?
A320neo ans A321neo experiencing CoG issues?
https://simpleflying.com/lufthansa-a320-cog-economy/ Following concerns regarding the center of gravity issues with the A321neo, the European Union Aviation Safety Agency (EASA) has uncovered a similar problem with the A320neo |
Originally Posted by Mark in CA
(Post 10568536)
A320neo ans A321neo experiencing CoG issues?
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I don't know, but I flew the 757 since it first came out of the factory. I don't recall any issues with the design.
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It's worth noting that all that happens with the neo is that it behaves like a normal aeroplane under a specific set of circumstances, and all the pilot has to do is fly it like a normal aeroplane. It is vastly different from the MAX issue.
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Salute!
Prolly a flight control law that needs some work. As the bus model(s) in question go, they do not have to meet the same control column pressure WRT AoA requirement that the 737Max does (no direct or indirect control surface posiiton/force feedback required for the FBW bus) They also do not have a stick vibrator like the Boeing stick shaker for stall warning, just "bells and whistles". Besides using direct AoA values for the control laws, we also have gains due to CAS ( Q, or dynamic pressure) and some rate variables. So unless there are serious aero pitch moment problems that the existing control surfaces cannot overcome, this should be a quick fix,and an effective one. EDIT: The AoA limiter ( they call it "protection") should have some degree of "rate" or pitch onset to prevent overshoots, but we would have to see the curves/plots and time constants for all the variables to gain a good understanding.. This problem appears to be an overshoot one, does it not? So maybe the rate variable could use some attention, as well as the gains in effect got TOGA scenarios.. END EDIT Gums opines... |
it behaves like a normal aeroplane under a specific set of circumstances, and all the pilot has to do is fly it like a normal aeroplane As the systems have improved, the point at which they fail keeps getting deeper and deeper into the areas that make the aircraft unnecessarily hard to fly. At some point, as they keep progressing, the 'system' will hand over a larger and larger bag of **** each time. Airbus has had the effect of weakening pilot skills because they've automated a lot of the day to day stuff...but at the same time, when it all goes tits-up, you'll need those very same weakened skills. Just a thought..... |
The problem is essentially mitigated if the rear row of seats is unoccupied. That’s not a fundamental aeronautical design issue, it is a 'Well, head office insist on another row up back' issue. |
Originally Posted by gums
(Post 10568696)
As the bus model(s) in question go, they do not have to meet the same control column pressure WRT AoA requirement that the 737Max does (no direct or indirect control surface posiiton/force feedback required for the FBW bus) ..
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Why are we allowing electronics to make planes safe to fly? Should they not be designed to be "stable" in normal flight conditions without computer intervention, with override only happening when something very unusual happens?
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Originally Posted by robdean
(Post 10568760)
The problem is essentially mitigated if the rear row of seats is unoccupied. That’s not a fundamental aeronautical design issue
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That's what happens with the modular approach airplane families are designed today. Stretch them, make them heavier, install more powerful engines and change the cabin interior and onboard installations (tanks) to upset weight and balance - But keep the wings and rudders the size they were before.
No surprise you end up with some surprises at the corners of the flight envelope. On computer controlled aircraft those things can be modified more elegant than on old style (MAX) mechanical controlled airplanes. |
Engineers have not forgotten how to build airplanes. It is just that today, it is the CEOs, accountants, and marketing people who are driving the design process from the top down. In the past it was the engineers saying what could be done and the upper management marketed and sold what the engineers could build.
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Originally Posted by Atlas Shrugged
(Post 10568712)
And therein lies the problem.
As the systems have improved, the point at which they fail keeps getting deeper and deeper into the areas that make the aircraft unnecessarily hard to fly. At some point, as they keep progressing, the 'system' will hand over a larger and larger bag of **** each time. Airbus has had the effect of weakening pilot skills because they've automated a lot of the day to day stuff...but at the same time, when it all goes tits-up, you'll need those very same weakened skills. Just a thought..... |
Has everyone suddenly forgotten how to build airplanes? |
Although they may look like airplanes, they are really giant computers. That said, it doesn't hurt to all step back and remember that the recent era of the aviation industry is safer now statistically that it ever was. That is not an argument against continuing to improve.
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As is ever the case we pilots love to debate niff naff and trivia. Airliners may be giant computers but airlines buy them to MAKE MONEY! Airlines are run by accountants whose sole purpose is to MAKE MONEY! Safety is not in the ledger. When have you ever heard of an accountant being held responsible for anything safety related in ANY industry? Industry are under intense pressure to produce these aircraft quickly and cheaply. This isn’t a “rocket science” problem. A few high profile corporate manslaugter convictions when accidents happen will soon focus the mind, before these slippery corporate types slither away to take charge of a nuclear power station project or the next space shuttle. As a pilot I don’t give a rip how many computers or widgets the manufacturer has incorporated into the design. I don’t care whether it’s a Boeing or an Airbus. I just want the hunk of metal to be a quality product and safe. And I want to be properly instructed to fly it. I’d personally be willing to take a lower salary to be sure of those things. Sadly the thing we senior pilots seem far to preoccupied with is MAKING MONEY!........... and round and round we go! |
Originally Posted by NEDude
(Post 10568879)
Engineers have not forgotten how to build airplanes. It is just that today, it is the CEOs, accountants, and marketing people who are driving the design process from the top down. In the past it was the engineers saying what could be done and the upper management marketed and sold what the engineers could build.
Take the 777, in which the market had a seat at the table. It makes no sense for it to work any other way, it just requires engineers to be clear about what can or cant be done |
Originally Posted by svhar
(Post 10568676)
I don't know, but I flew the 757 since it first came out of the factory. I don't recall any issues with the design.
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"The problem is essentially mitigated if the rear row of seats is unoccupied. That’s not a fundamental aeronautical design issue
Originally Posted by DaveReidUK
(Post 10568866)
Sounds like a pretty good description of one to me.
I believe we have talked about not sitting in the last row on our own flights on some planes |
Originally Posted by lomapaseo
(Post 10569151)
Rarely does the designer specify where each row of seats are placed or baggage stowed. They tend to specify the pressure bulkheads fore and aft and then provide info for an operator to use the plane.
But the designer will have determined the C of G envelope within which the airlines can configure the cabin and operate the aircraft. For a regulator to step in and retrospectively impose a more limited C of G range indicates that something hasn't gone according to plan. |
Originally Posted by Joe le Taxi
(Post 10568783)
It's an interesting point - how come Airbus gets away with this exemption just because the stick is on the side, while Boeing are required to create perfectly progressive stick feedback force, all the way to the extremes of the envelope, and in trying to meet the requirement, create MCAS? Progressive pitch force is a major design headache, from single engine homebuilts, right through to airliners. Meanwhile there have been several Airbus incidents, arguably attributable to the lack of stick force feedback.
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Originally Posted by DaveReidUK
(Post 10569187)
But the designer will have determined the C of G envelope within which the airlines can configure the cabin...
So, where did the process break down? A poor envelope specification up front? Or marketing caving in to a customer to cram in just one more row of seats? The article says Lufthansa is affected rather than all customers. So I suspect it's the latter. |
Originally Posted by EEngr
(Post 10569200)
So, where did the process break down? A poor envelope specification up front? Or marketing caving in to a customer to cram in just one more row of seats? The article says Lufthansa is affected rather than all customers. So I suspect it's the latter.
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Balance.
All you need is fatter folk in row 0.
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When I trim my Airbus in DCT law for clean speed and then bring towards stall using a pitch up command on the stick, there is progressive force that needs to be overcome. No issue.
Next. Oh, wait. If I have a stroke mid-way and let go off the stick, the nose drops down and does not hang up, or - heaven forbid - keep raising. For those interested in the particular CG restriction on A320, please see my comment on the A321 thread. Speaking of which: if the manufacturer discovers on a test rig something about the pitch response is not aligned with the book exactly, WITHOUT any prior in-service event or SIM observation, just by doing their QA homework properly, that is actually how you DO build an aeroplane. Not faultless, but responsible is the key word. If I wanted to be mean, a little note would slip about how you can fully trim the Bus manually in and out of all settings at all corners of the envelope. But I am a much nicer person than that. |
Expecting a pilot who had 250 hours years before he started flying Airbus airplanes to actually know how to fly a normal airplane is a little much. I flew the A320 and loved it, but I spent years flying most of the Boeings first. There is a huge difference.
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It’s “stick forward to lower the nose” type skills, not something esoteric like landing a tail dragger. |
I cannot understand how being a pilot of an FBW airliner is any lesser than a cables and pulley airliner pilot.
Does anyone criticise F16 or current FBW fighter pilot as being a lesser pilot than an F4 or A4 pilot? Strange logics (no pun intended). You are there to fly/operate a flying machine that 'makes money' for 'shareholders'. If you're lucky you have an aeroplane that makes doing that day in, day out easier and 'backs you up'. If you wanna go 'flying', dislodge some quids out of your wallet and go fly a Maul! |
Having flown both, I'd say “not at all”. Each has their challenges. But please do note that somewhere in the first few pages of the Airbus FCTM is the helpful advice that, when in direct law, one simply flies the aircraft like a conventional jet transport. What do you expect that pro tip might mean to somone who has never done that? i never really loved the manual flying on FBW, but then again I never HAD to, it was always done for skill retention only. |
Is the C of G issue because of too much of a forward or an aft trim, or both scenarios?
If so, this maybe the case of a full Business class load in the front (and maybe cargo), and too few Y pax down the back, or vice versa... Hardly anyone has checked bags anymore in Business so one cannot offset out of trim situations with the hold baggage. We had a particular problem with Transavia Holland on a 737-200 used for the LGW-AMS scheduled services, which had a movable business cabin so you never knew much in advance of the variable loads - It was a pig to trim which for a 737-200 was unusual, but caused by a lot of extra metal installed in the front area due to some re-skinning (post Aloha HNL) |
Originally Posted by rog747
(Post 10569590)
Is the C of G issue because of too much of a forward or an aft trim, or both scenarios?
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Originally Posted by Joe le Taxi
(Post 10568783)
...............how come Airbus gets away with this exemption just because the stick is on the side, while Boeing are required to create perfectly progressive stick feedback force, all the way to the extremes of the envelope, and in trying to meet the requirement, create MCAS? Progressive pitch force is a major design headache, from single engine homebuilts, right through to airliners..........
An analogy might be modern cars having ABS braking systems. Cars without ABS require the driver to prevent locking the wheels in slippery conditions, ABS performs the anti-locking function ‘in the background’. Cars with ABS are safer in slippery conditions than those without. (ABS also works on individual locked wheels. The driver of a non ABS car can only release or apply brakes to all the wheels simultaneously). |
The Lufthansa A320neo is tail heavy because they moved the lavs into the tail using the spaceflex option and did some modifications in the front to squeeze in two extra rows of seats. The tail heavy situation was known and because of it they didn't fit the inflight WiFi equipment either.
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i never really loved the manual flying on FBW, but then again I never HAD to, it was always done for skill retention only. Any new type is going to have teething problems, the airlines always finish off the testing program for the manufactures by which stage anything major should have been picked up. It would be uneconomic and probably impossible to have a new aircraft absolutely perfect before the first delivery, some faults will only manifest themselves under very specific conditions or after a certain length of time in service. |
Lufthansa blocking off last row
This according to Aviation Week. Begs the question. If you removed the last row and re-configured the seat map so the ac would have one less row total but the 'new' last row would be in current position of the blocked row, would the CoG issue still remain?
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[QUOTE]would the CoG issue still remain?/QUOTE]
Maybe, the CG of pax stays at the same point but with a little less weight. So it depends. |
Originally Posted by b1lanc
(Post 10571261)
This according to Aviation Week. Begs the question. If you removed the last row and re-configured the seat map so the ac would have one less row total but the 'new' last row would be in current position of the blocked row, would the CoG issue still remain?
Either way, you still have 6 sellable seats less than you started with, plus you'd have the cost of re-aligning all the PSUs, etc with the revised configuration. |
Originally Posted by DaveReidUK
(Post 10571338)
Even if it cured the C of G issue
There is a pitching moment attenuation issue, not a CoG one. To avoid manifestation of the problem a CoG restriction was put in place, until the flight controls are sorted out. |
Originally Posted by FlightDetent
(Post 10571553)
There is a pitching moment attenuation issue, not a CoG one. To avoid manifestation of the problem a CoG restriction was put in place, until the flight controls are sorted out.
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Originally Posted by robdean
(Post 10568760)
The problem is essentially mitigated if the rear row of seats is unoccupied. That’s not a fundamental aeronautical design issue, it is a 'Well, head office insist on another row up back' issue. Therefore, if there were no extra seats, the aircraft would have requisite stability? |
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