hypersonic
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Changing Feel Of An Aircraft: Pilots Perspective?

Mon Apr 28, 2008 10:15 am

From a pilots perspective....

During the normal course of your jobs, I'd imagine that when you're flying a particular aircraft type on your routes, that, even though the aircraft type may stay the same... 757-200 for example, I'm sure that the actual physical aircraft you fly changes frequently.

My question simply is, as you go from operating one 747-400 to the next 747-400 etc etc/, are the aircraft so precisely made & so well maintained, that the actual 'handling' & 'feel' from plane to plane is the SAME?
OR... due to differences in age, prior handling behaviour of other pilots, different maintence issues over time & so on, make each plane of the same make & model actually feel quite different handling-wise, performance & so on.

I guess this can also apply to air aircraft type..
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Starlionblue
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RE: Changing Feel Of An Aircraft: Pilots Perspective?

Mon Apr 28, 2008 11:03 am

As I understand it:
- On Boeings and pre-FBW Airbi, feel changes all the time even on the same aircraft due to weight changes, altitude changes, flex take-off, etc...
- On post-FBW Airbi, feel is regulated by computers to compensate for differences. For example 318-321 all feel the same to the pilot.

I'm not a pilot, but I imagine the feel thing is a bit like different cars of the same model. Sure, you might notice the differences, but it's hardly going to impair your driving and you will adjust quickly and more or less subconsciously.
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PhilSquares
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RE: Changing Feel Of An Aircraft: Pilots Perspective?

Mon Apr 28, 2008 11:31 am



Quoting Hypersonic (Thread starter):
My question simply is, as you go from operating one 747-400 to the next 747-400 etc etc/, are the aircraft so precisely made & so well maintained, that the actual 'handling' & 'feel' from plane to plane is the SAME?

Surprisingly, two different aircraft, both at roughly the same weights do fly just about the same. You do really notice the difference between a lightly loaded 400, vs a 400 at MTOW. But similar aircraft, as similar weights/CG do feel the same.
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CosmicCruiser
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RE: Changing Feel Of An Aircraft: Pilots Perspective?

Mon Apr 28, 2008 11:54 am



Quoting Hypersonic (Thread starter):
My question simply is, as you go from operating one 747-400 to the next 747-400 etc etc/, are the aircraft so precisely made & so well maintained, that the actual 'handling' & 'feel' from plane to plane is the SAME?

I've always noticed some jets may differ in feel. One may be a little stiffer or "heavier" on the elevators or ailerons but nothing that's very significant. The time or two I thought it was I made a maint write up.
 
point8six
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RE: Changing Feel Of An Aircraft: Pilots Perspective?

Mon Apr 28, 2008 5:17 pm

As Phil Squares states, there is a difference between light and heavy performances, but the variation across the fleet is hardly noticeable. What is noticeable is that if the fleet consists of hulls originally delivered to different customers, then the location of various switches and CRT/LCD information is often very different - and can be quite demanding at times of high workload.  Confused
 
2H4
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RE: Changing Feel Of An Aircraft: Pilots Perspective?

Mon Apr 28, 2008 5:27 pm



Quoting Point8six (Reply 4):
What is noticeable is that if the fleet consists of hulls originally delivered to different customers, then the location of various switches and CRT/LCD information is often very different

I've always found it amazing that aircraft manufacturers ever even allowed their (transport-category) aircraft to leave the factory with such differing flight decks.

It seems pretty obvious that, at some point in their lifespan, the aircraft fleets will split and combine with one another. The resulting dissimilar fleets will have less standardization and more potential for confusion and errors on the flight decks.

I suppose flight deck standardization might have been undervalued in the past. It seems as though current-production aircraft have far less variation when it comes to panel/cockpit layout.

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Alias1024
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RE: Changing Feel Of An Aircraft: Pilots Perspective?

Mon Apr 28, 2008 6:28 pm

Feel does change a slightly from aircraft to aircraft. Some might require rudder or aileron trim in one direction or another, while others fly perfect at the neutral setting. Eventually you get it trimmed out nicely and it feels like every other aircraft in the fleet.
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JRadier
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RE: Changing Feel Of An Aircraft: Pilots Perspective?

Mon Apr 28, 2008 7:14 pm



Quoting 2H4 (Reply 5):

I suppose flight deck standardization might have been undervalued in the past. It seems as though current-production aircraft have far less variation when it comes to panel/cockpit layout.

Keep in mind that an operator often already has a certain layout (say from previous 737's when ordering the NG) and wants to keep it that way. I remember a tv show about the acceptance and delivery of a KLM 737-800 where the test pilots made Boeing (per the contract) change the colour of the needle of the standby airspeed gauge. It's that precise.
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point8six
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RE: Changing Feel Of An Aircraft: Pilots Perspective?

Mon Apr 28, 2008 7:29 pm

Should an operator decide to standardise the cockpit layout of the same type of aircraft originally delivered to different customers, I'm sure the manufacturer and the various suppliers would undertake the work. However, it would cost and I think that is why it is cheaper to issue the crews with "difference notes" rather than pay for the conversions. Different engine types require different upper and lower EICAS presentations e.g the RR has N1,N2 and N3 read-outs and the GE has no EPR read-out, whereas the PW has N1 and N2 and EPR. In particular, Boeing offer the basic aircraft and the airline 'customises' it's choice.Some -400's have a stab tank and some (including freighters, do not). Some NDs display TAS and some do not. etc.etc..  Smile
 
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HAWK21M
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RE: Changing Feel Of An Aircraft: Pilots Perspective?

Mon Apr 28, 2008 10:05 pm

There can be occassions when the Artifical feel of each type of an Aircraft in the fleet would vary.Thats when Mx is informed & same can be corrected.
regds
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2H4
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RE: Changing Feel Of An Aircraft: Pilots Perspective?

Mon Apr 28, 2008 10:12 pm



Quoting HAWK21M (Reply 9):
There can be occassions when the Artifical feel of each type of an Aircraft in the fleet would vary.

Here's a rather extreme example:

Cross-wired controls almost bring down Lufthansa A320

Tim van Beveren/MIAMI

A Lufthansa Airbus A320 almost crashed shortly after take-off because of reversed wiring in the captain's sidestick flight control. Quick action by the co-pilot, whose sidestick was not faulty, prevented a crash.

The 20 March Frankfurt-Paris schedule service hit turbulence just after rotate and the left wing dipped. The captain responded with a slight sidestick input to the right but the aircraft banked further left. The pilot followed up with a stronger right input. The aircraft responded with more left bank, reaching 21í. Realising the problem, the copilot switched his sidestick to priority and recovered the aircraft.

According to sources close to the investigation, the flight data recorder revealed that the left wing dipped to within 0.5m (1.6ft) of the ground. "If this had continued for 5s more, the aircraft would have definitely crashed," says the source. A full report by the German BFU aircraft accident investigation board is expected shortly. Airbus declines to comment and Lufthansa would not make anyone available for comment.


 Wink

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tdscanuck
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RE: Changing Feel Of An Aircraft: Pilots Perspective?

Tue Apr 29, 2008 2:28 am



Quoting 2H4 (Reply 5):
I've always found it amazing that aircraft manufacturers ever even allowed their (transport-category) aircraft to leave the factory with such differing flight decks.

Although it's obvious that the fleets will eventually get mixed, the OEM is only dealing with the original purchaser. All the second/third/forth/etc. hand trades are between airlines (or leasors and airlines). The manufacturer will do what the original purchaser wants.

Quoting 2H4 (Reply 5):
I suppose flight deck standardization might have been undervalued in the past. It seems as though current-production aircraft have far less variation when it comes to panel/cockpit layout.

This is being strongly driven by the rise of the leasing companies. When most airplanes were owned by their airline the value proposition to the buyer was to have that aircraft aligned as closely as possible to your operation. As a result, specialization for different operators and little pressure for commonality. For a leasor, where the aircraft is likely to change hands several times over its life, portability is a much greater value proposition. And, as leassors became a bigger and bigger piece of the purchasing pie, their needs floated higher on the list requirements. This phenomenon is the direct cause of the much higher number of "standard options" and ability to swap engines on the 787.

Tom.
 
SlamClick
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RE: Changing Feel Of An Aircraft: Pilots Perspective?

Tue Apr 29, 2008 3:44 am

The only time I've ever experienced this in transport category aircraft was when there was something wrong with the tail number in question. As to how they 'feel' or how they 'fly' they are remarkably similar at any given weight, configuration and speed. There are types where I've had a pretty good sampling. For example I've flown over a hundred different airframe number 737s and over a hundred different A-320 series as well. I couldn't identify a nickel's worth of individuality in any one of them.

On the other hand, that was not unheard of among small airplanes. I have felt rather out-of-sorts when flying one particular single after having flown a different tail number exclusively for about a year. Jumped in a stablemate just as identical as metalcrafters know how to make them and it felt very different. Had I been jumping from one to another to another all year long, however, I doubt that I'd ever have noticed anything.

Quoting 2H4 (Reply 5):
at some point in their lifespan, the aircraft fleets will split and combine with one another. The resulting dissimilar fleets will have less standardization

Long-since addressed by FAR Part 121 training requirements. Any "differences" no matter how insignificant they may seem to you must be taught and otherwise presented to the pilots. So an all-GPS airline merges with a partly- or non-GPS airline and the non-standard planes must be conspicuously placarded. In more extreme cases an airline might have three different models of the same type, with four or five different engine possibilities and with still further variances in avionics and accessories, all of which might necessitate a full day of "differences" training in the initial checkout.

One particular plane I flew happened to be the last remaining one in US registry that had a certain overhead panel configuration. All others, including all the simulators had the switches operate in the opposite direction. No "differences" training required there because there was no public safety issue. We flew our plane as it was configured and if we crashed the simulator no one got hurt. Motivated you to be pretty careful on the overhead during a checkride, though.
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HAWK21M
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RE: Changing Feel Of An Aircraft: Pilots Perspective?

Tue Apr 29, 2008 8:10 am



Quoting 2H4 (Reply 10):
Here's a rather extreme example

That was one serious snag.Surprising it was not detected on Ground check though.
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SlamClick
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RE: Changing Feel Of An Aircraft: Pilots Perspective?

Tue Apr 29, 2008 2:26 pm



Quoting HAWK21M (Reply 13):
Surprising it was not detected on Ground check though.

I don't know what checks were performed by maintenance but it shouldn't surprise anyone that it could be missed by the first officer when the captain did his flight control check before takeoff.

The flight control check for the 320 typically has the captain take his sidestick:

Full aft. - The 'flight control' page pops up on the lower ECAM screen and the first officer observes correct control movement and replies "full up"

Full forward. - The first officer observes full nose down on the ECAM and replies "full down"

Full left. - The first officer observes left aileron up, right aileron down, roll spoilers on left wing up. and replies "full left"

Full right. - The first officer observes right aileron up, left aileron down, roll spoilers on right wing up. and replies "full right"

And the same thing with the rudder.

Simple enough but this is not the sort of thing humans do reliably. What he saw when the captain moved the sidestick laterally was "correct" indications but reversed as to left/right. We have a natural tendency to see what we expect to see. This is why airport screeners frequently allow something shaped exactly like a pistol pass right on by. Had a couple of the roll spoilers not extended he undoubtedly would have caught that. Had no flight controls moved at all he would almost certainly caught that. But what he saw was exactly right - just opposite. Unless it just happens to jump out at you, in a complacent moment it is easy to slip reversals past you.

How easy? Well, there is a famous photograph of the outlaw "Billy the Kid" and for fifty years or more people saw his holster rig and concluded that Billy Bonney was left handed. Finally, after a million or more people had stared at the photograph someone suddenly noticed that the loading port for the Winchester rifle in his hands was on the WRONG SIDE. The negative had been reversed when the picture was printed and no one had ever caught that.

Of all the things Airbus could automate how about that one. If the microswitches detect either sidestick full in one directon and the flight controls moving in the opposite you get a WARNING message? Doesn't that seem pretty easy to fix? After all the movement/position sensors are already installed! Just add a line of program to a flight control computer.

Yes, it was a human error, a total no-brainer. But that Airbus itself doesn't make a miniscule change to their product and absolutely prevent this sort of thing forever is pretty hard to defend. I mean the rest of the world freely admits that we humans are (a.) error-prone and (b.) very hard to re-engineer. This is one of the big arguments for automation in the first place. I love the Airbus but shame on them for not fixing this one.

Oh, and fly-by-wire is not to blame. This sort of design flaw goes at least back to the DC-3 which had its aileron cables exactly the same length. It was possible to connect them backwards at a bellcrank and it has happened.

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BAE146QT
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RE: Changing Feel Of An Aircraft: Pilots Perspective?

Tue Apr 29, 2008 4:29 pm



Quoting 2H4 (Reply 5):
I've always found it amazing that aircraft manufacturers ever even allowed their (transport-category) aircraft to leave the factory with such differing flight decks.



Quoting Tdscanuck (Reply 11):
Although it's obvious that the fleets will eventually get mixed, the OEM is only dealing with the original purchaser. All the second/third/forth/etc. hand trades are between airlines (or leasors and airlines). The manufacturer will do what the original purchaser wants.

Maybe this is excessively cynical, but I reckon that Tdscanuck is right at the nub of the situation. Where practical, the supplier accedes to the demands of the customer. And if a future owner wants things different, well that's not the supplier's problem. Might even work out well for the supplier if the new customer brings the bird to them for modification.

The question you might ask is, why do the various regulatory bodies allow it to happen?

Quoting SlamClick (Reply 12):
I couldn't identify a nickel's worth of individuality in any one of them.

I guess if they're all the same, you don't have the safety issue of a pilot being distracted by getting used to an aircraft which handles differently. The psychology behind this is obvious, but recent experiments with cars (of the same model) seem to suggest that even they don't differ that much, despite (supposedly) being shoddily-built, everyday consumer items.

Manufacturing tolerances and quality assurance have improved so much and I wonder what DC2 pilots would think of it.

Quoting SlamClick (Reply 12):
In more extreme cases an airline might have three different models of the same type, with four or five different engine possibilities and with still further variances in avionics and accessories, all of which might necessitate a full day of "differences" training in the initial checkout.

Apologies for being Anglo-centic, (since all manner of large airlines are in this situation), but I imagine this must be a huge headache for BA*.




* That's "British Airways" not Mr. T.
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2H4
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RE: Changing Feel Of An Aircraft: Pilots Perspecti

Tue Apr 29, 2008 4:43 pm



Quoting BAe146QT (Reply 15):
* That's "British Airways" not Mr. T.

Any kind of flying is a huge headache for Mr. T...

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lowrider
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RE: Changing Feel Of An Aircraft: Pilots Perspective?

Tue Apr 29, 2008 5:14 pm

I think it is easier to detect a difference in aircraft with cable or push rod controls verses hydraulic controls. Even that difference has been more attributable to being a different version (ex a -200 vs. a -300) or having different engines or props. I haven't flown anything that is Fly By Wire (though I suppose you could say the cable controls count as Fly By Wires). The biggest difference I notice on the current fleet is the rigging of the thrust levers. Some match up at identical settings and others aren't even in the same zip code.
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wilco737
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RE: Changing Feel Of An Aircraft: Pilots Perspective?

Tue Apr 29, 2008 5:16 pm



Quoting CosmicCruiser (Reply 3):
I've always noticed some jets may differ in feel. One may be a little stiffer or "heavier" on the elevators or ailerons but nothing that's very significant. The time or two I thought it was I made a maint write up.

Yeah I thought the same! but just slightly different! the biggest difference - as said before - is with different weight! Today I had a landing weight of 200 tons (222.9 is maximum) and the other day we had only 130 tons... And with only 130 tons she is not so stable, every little disturbance in the air affects the aircraft! not with 220 tons! Then she is stable and not so easy to be tossed around (and easier to land as well)...

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2H4
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RE: Changing Feel Of An Aircraft: Pilots Perspecti

Tue Apr 29, 2008 5:19 pm



Quoting Lowrider (Reply 17):
The biggest difference I notice on the current fleet is the rigging of the thrust levers. Some match up at identical settings and others aren't even in the same zip code.

I propose a Tech/Ops photo contest for the most out-of-rig thrust levers in cruise. The engine instruments and thrust levers must both be visible in the shot. Let's see what you guys can come up with...  biggrin 

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SlamClick
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RE: Changing Feel Of An Aircraft: Pilots Perspective?

Tue Apr 29, 2008 11:18 pm



Quoting Lowrider (Reply 17):
I think it is easier to detect a difference in aircraft with cable or push rod controls verses hydraulic controls.

I agree with you on that. However, I can think of a couple of early examples where, very subjectively, I felt that the pilot seat was just a bit to the left of where I'm used to , or something like that. That is an actual example I referred to above: The planes are identical except the pilot eyeball position in this one example seems just a bit off-center. Every time I reach for something with hand or eye it turns out to be not quite where I expected it. Not a difference in control feel, but in ambiance if you will, and that is vaguely disorienting.
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Jetlagged
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RE: Changing Feel Of An Aircraft: Pilots Perspective?

Wed Apr 30, 2008 12:43 am



Quoting BAe146QT (Reply 15):
Apologies for being Anglo-centic, (since all manner of large airlines are in this situation), but I imagine this must be a huge headache for BA*.

BA certainly used to make an effort to standardise their fleets, if only because BA used to have some unusual options installed. The problem is much worse for cargo airlines which pick up aircraft from all sorts of sources and usually make little or no effort to standardise on one configuration. Especially a problem for 747 classic operators, since there are so many variations possible. The only way to ensure a reasonably common configuration is to source all aircraft from one airline which bought theirs from new, not usually possible.
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saab2000
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RE: Changing Feel Of An Aircraft: Pilots Perspective?

Wed Apr 30, 2008 12:47 am

FWIW, a heavy aircraft of one type flies much nicer than a light aircraft of the same type. I fly the CRJ and when we are at Max Gross T/O weight the performance is lame and the runway length used is ridiculous, but it does fly better. Less affected by gusts, etc. And landings when at MLW at the nicest.
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tdscanuck
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RE: Changing Feel Of An Aircraft: Pilots Perspective?

Wed Apr 30, 2008 5:19 am



Quoting SlamClick (Reply 14):
Of all the things Airbus could automate how about that one. If the microswitches detect either sidestick full in one directon and the flight controls moving in the opposite you get a WARNING message? Doesn't that seem pretty easy to fix? After all the movement/position sensors are already installed! Just add a line of program to a flight control computer.

It's relatively rare to have fault detection for mis-wiring. Most fault detection assumes that everything is hooked up right and is just looking for missing or invalid signals.

Quoting SlamClick (Reply 14):
But that Airbus itself doesn't make a miniscule change to their product and absolutely prevent this sort of thing forever is pretty hard to defend.

It's very easy to defend. A piece of code to pick up that exact error is trivial. However, you'd have to know in advance that that was the wiring error that would get made. The average airliner has thousands (probably tens of thousands) of individual wires. The number of possible mis-wirings is astronomical. You'd need tens of millions of lines of code to catch all the potential mis-wirings alone, which is more than the entire aircraft software suite typically employs.

It's *far* more efficient to assume that the mechanics will do it right and then do a functional check to make sure they actually did. The real question is how did this not get picked up during the maintenance action, not how did the flight crew miss it.

Tom.
 
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RE: Changing Feel Of An Aircraft: Pilots Perspecti

Wed Apr 30, 2008 5:30 am

Quoting Tdscanuck (Reply 23):
It's *far* more efficient to assume that the mechanics will do it right and then do a functional check to make sure they actually did.

The power cord on my flatbed scanner has a connector that can only be plugged in the correct way. Due to the shape of the plug, it's physically impossible to plug it in backward. Given that humans are prone to error, such as in the above example, it seems to me the prudent solution would be to equip the most critical (ie: flight control) connections with similarly idiot-proof connectors.

If this is, for whatever reason, impossible, I would investigate the possibility of simple IF/THEN sensors that would detect abnormal relationships between the yoke/pedals and control surfaces. For example, IF the yoke is moved left and the left aileron moves upward, THEN all is ok. But IF the yoke is moved left and the left aileron moves downward, THEN a warning illuminates. The physical positions would be compared, and reversed flight-control takeoffs will never happen again. No need for millions of lines of code or faultless humans.

2H4

[Edited 2008-04-29 22:37:39]
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SlamClick
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RE: Changing Feel Of An Aircraft: Pilots Perspective?

Wed Apr 30, 2008 5:52 am



Quoting Tdscanuck (Reply 23):
It's relatively rare to have fault detection for mis-wiring.

I'm not talking about fault detection for mis-wiring.

> The airplane has sensors that know where the sidesticks are positioned.
> The airplane has sensors that know the position of every control surface.
> There is NEVER an occasion when you want full left sidestick with full right control inputs.
> The highly automated airplane depends on the pilot's HUMAN eye-brain combination to detect if it happens when a line of code in a SEC or ELAC could trigger a warning if it does happen.

In my opinion that is trusting to luck to an almost criminal degree.

It will happen again.
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tdscanuck
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RE: Changing Feel Of An Aircraft: Pilots Perspective?

Thu May 01, 2008 3:29 am



Quoting 2H4 (Reply 24):
The power cord on my flatbed scanner has a connector that can only be plugged in the correct way. Due to the shape of the plug, it's physically impossible to plug it in backward. Given that humans are prone to error, such as in the above example, it seems to me the prudent solution would be to equip the most critical (ie: flight control) connections with similarly idiot-proof connectors.

The major difference is that your power cord can't be repinned. Most aircraft connectors are keyed...they only go together the right way. However, they can all be repinned because you're never going to have every pin, joint, and and wire in every connector survive for 20-30 years of heavy use and replacing a wire bundle is typically only possible on a heavy maintenance visit (and then it's still a pain in the a$$). If an electrician screws up a pinout having the right connector on the right way around doesn't help.

Quoting 2H4 (Reply 24):
If this is, for whatever reason, impossible, I would investigate the possibility of simple IF/THEN sensors that would detect abnormal relationships between the yoke/pedals and control surfaces. For example, IF the yoke is moved left and the left aileron moves upward, THEN all is ok. But IF the yoke is moved left and the left aileron moves downward, THEN a warning illuminates. The physical positions would be compared, and reversed flight-control takeoffs will never happen again.

Absolutely true. It would make a lot of sense to have this type of test written into the maintenance BITE for the flight control system...doing it in real time in flight would be eating a lot of processor cycles for no real reason.

Quoting SlamClick (Reply 25):
> The airplane has sensors that know where the sidesticks are positioned.
> The airplane has sensors that know the position of every control surface.
> There is NEVER an occasion when you want full left sidestick with full right control inputs.

Unfortunately, that's not true on a FBW aircraft, especially one with envelope protection or active gust alleviation. Once you break the one-to-one relationship between input device position and control surface position, your diagnostic system has to be far more complex to pick up these types of things. It's obviously doable, but it's not as trivial as one might think.

Tom.
 
SlamClick
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RE: Changing Feel Of An Aircraft: Pilots Perspective?

Thu May 01, 2008 4:12 am



Quoting Tdscanuck (Reply 26):
it's not as trivial as one might think.

On the ground, with weight on the wheels it sure as hell is. I'm just not buying it.

Sorry, easy fix. Important fix.
It will kill a load of people some day and the guilty party will blame the pilots for making one of the most common human errors there ever was.

If I can figure this out, Airbus can figure this out. The FAA can figure this out. The airlines can figure this out.
It is negligent and if my loved ones have the misfortune to be aboard WHEN it happens I will sue the living snot out of all of the above.
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2H4
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RE: Changing Feel Of An Aircraft: Pilots Perspective?

Thu May 01, 2008 4:17 am



Quoting Tdscanuck (Reply 26):
If an electrician screws up a pinout having the right connector on the right way around doesn't help.

Ah, good point.

Quoting Tdscanuck (Reply 26):
doing it in real time in flight would be eating a lot of processor cycles for no real reason.

I bet those A320 pilots would argue otherwise....  Wink

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tdscanuck
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RE: Changing Feel Of An Aircraft: Pilots Perspective?

Thu May 01, 2008 6:45 am



Quoting SlamClick (Reply 27):
Quoting Tdscanuck (Reply 26):
it's not as trivial as one might think.

On the ground, with weight on the wheels it sure as hell is. I'm just not buying it.

Sorry, easy fix. Important fix.

I'm not suggesting that this exact error is non-trivial to diagnose on the ground...as you correctly note, it's really easy. However, continuous monitoring for this type of error in flight is non-trivial. There are also a huge number of trivial errors that can be checked for so, even if you catch this one, odds are that the next one will be one that you haven't programed the system to catch. Functional and operational tests are a far better option than system monitoring to catch one-time maintenance screwups.

Quoting SlamClick (Reply 27):
If I can figure this out, Airbus can figure this out. The FAA can figure this out. The airlines can figure this out.

The problem isn't figuring it out. It's really really easy to figure out. The problem is that there are an essentially infinite number of ways a mechanic can do a procedure incorrectly, but only a few ways to do it correctly. Almost all of the ways of doing it incorrectly are easy to figure out and, in isolation, easy to mitigate. However, the shear number of them means that manufacturers don't design the maintenance procedures to be 100% idiot proof...it's a total economic non-starter and you can't do it effectively anyway. You write the procedures so they work *if followed correctly* and then you follow every maintenance procedure with a functional or operational check that can only be passed if the procedure was done correctly. It's far more effective to identify when you've made a screwup than try to proactively engineer out all possible screwups.

The mistake here was not checking the sidestick agreement with flight control movement when the sidestick was installed. It's not a flaw in the airplane that the airplane isn't looking for a mistake that a) shouldn't have been made and b) should have been caught before the plane was released to service.

Tom.
 
CosmicCruiser
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RE: Changing Feel Of An Aircraft: Pilots Perspective?

Thu May 01, 2008 12:40 pm



Quoting WILCO737 (Reply 18):
the biggest difference - as said before - is with different weight! Today I had a landing weight of 200 tons (222.9 is maximum) and the other day we had only 130 tons... And with only 130 tons she is not so stable,

Your right this jet was made to fly at a heavier wgt. Light landings are always the biggest challenge.

What i was referring to in my first post was slight diff from jet to jet probably the result of act valves, etc as I show in this blurb below from the CFM. Like I said never a big deal just noticeable.

The actuator valves (surface position) are controlled
mechanically by movement of the control columns in
the cockpit. The two cockpit control columns are
mounted on a common torque tube.
Linear Variable Differential Transformers (LVDT) in
the actuators send elevator position signals to the
Flight Control Computers (FCC) and the SD configuration
display.
 
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Jetlagged
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RE: Changing Feel Of An Aircraft: Pilots Perspective?

Thu May 01, 2008 3:10 pm



Quoting Tdscanuck (Reply 29):
I'm not suggesting that this exact error is non-trivial to diagnose on the ground...as you correctly note, it's really easy. However, continuous monitoring for this type of error in flight is non-trivial.

The answer surely is to limit the automatic cross check to on ground only, while the ECAM system "knows" the check is required (i.e. while the FLT CTLS page is automatically displayed. If the direction of control travel is opposite to the command then the deflection should be shown but the synotic control position drawn in red.
The glass isn't half empty, or half full, it's twice as big as it needs to be.
 
SlamClick
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RE: Changing Feel Of An Aircraft: Pilots Perspective?

Thu May 01, 2008 3:57 pm

Quoting Tdscanuck (Reply 29):
continuous monitoring for this type of error in flight is non-trivial.

Well here's the problem. NO ONE is talking about continuous monitoring in flight. That aspect of Airbus flight controls is fine as far as I can tell. The problem is on the ground before takeoff. If it tests correctly then it is not going to re-wire itself after you take off.

Airbus procedures call for the captain to take his sidestick full aft, neutral, full forward, neutral, full left, neutral then full right, as the first officer watches the "flight controls" page which automatically pops up on the lower ECAM. He then will press and hold the PEDALS DISC button and do the same check with the rudders - full left, full right, neutral.

The Lufthansa crew did exactly as above. The problem, the one and only problem is this: The only real "check" on the system is the first officer's eye-brain circuit recognizing full and correct movement of the flight controls. For a first officer to see the wrong movement and think he was looking at the correct movement may be a one-in-a-million shot, but it DID happen and it WILL happen again. This is an "incident" because his failure followed a related one in a million event. Frankly that he was able to recognize the problem and apply corrective action that didn't make the situation worse is also one in a million and every person who was aboard that plane should buy lottery tickets because they are extremely lucky.

The FAA (and other nations' regulatory bodies) have always recognized the 'one in a million' concept. An engine failure at V1 is petty much one in a million. A second engine failure shortly after that one is one in a million millions and aircraft designers are generally not required to make the planes safe in the once in a million millions event. Some trust to luck is needed if airplanes are even going to be able to fly.

My problem with the Airbus flight control check is simple. I'd guess that a human watching a video monitor for a certain display, seeing a display that was EXACTLY CORRECT except reversed left-right and missing that it was reversed is NOT one in a million. I'll bet it is more like one in a hundred. Every single day and almost every airport that uses human screeners they are tested on recognizing shapes associated with threats. Just about every single day some of them fail and are sent for additional training. It happens all the time.

So you ride on an Airbus and you bet your life that

(a.) Everyone who touches the flight control computer boxes, cannon plugs, wiring bundles etc. got all of it right AND

(b.) If they did get it wrong a copilot will rise above his normal human brain wiring and catch the reversal.


Personally I think the chances of that being caught are about 50/50 on any one visual check and I like better odds than that.

Now, no hardware needs to be added. They revise and update flight control computer code all the time. So add one line that says, in effect:
IF the airplane is on the ground
AND the sidestick or rudder pedals are moved to one stop
AND the associated flight controls move in the opposite direction
THEN a red master warning with CRC will be signalled.


It really is simple.

I'm betting a jury would feel exactly as I do about this.

[Edited 2008-05-01 09:06:08]
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SlamClick
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RE: Changing Feel Of An Aircraft: Pilots Perspective?

Thu May 01, 2008 4:03 pm



Quoting SlamClick (Reply 32):

An afterthought to the above: The cost of the software change would be nil. All they have to do is pad the bill of the next personal A-380 they build for some oil-rich customer. They'd never miss the money and they would be doing something altruistic and charitable for once.
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Jetlagged
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RE: Changing Feel Of An Aircraft: Pilots Perspective?

Thu May 01, 2008 4:25 pm



Quoting SlamClick (Reply 32):
Well here's the problem. NO ONE is talking about continuous monitoring in flight. That aspect of Airbus flight controls is fine as far as I can tell. The problem is on the ground before takeoff. If it tests correctly then it is not going to re-wire itself after you take off.

As I said here,

Quoting Jetlagged (Reply 31):

the ECAM already is aware the test is going on, because it automatically displays the FLT CTLS page when the stick or pedals are moved. Adding monitoring software along the lines you suggest while in this mode would not be difficult. It's actually a very Airbus-like thing to do. The M in ECAM stands for monitoring, IIRC.
The glass isn't half empty, or half full, it's twice as big as it needs to be.
 
SlamClick
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RE: Changing Feel Of An Aircraft: Pilots Perspective?

Thu May 01, 2008 5:20 pm



Quoting Jetlagged (Reply 34):
Adding monitoring software along the lines you suggest while in this mode would not be difficult.

Just be advised that a mediocre attorney could absolutely shred your argument in front of a jury.

It is preposterous.
They can make two hundred and fifty tons of metal in an A-330 FLY for hell's sake!
They can make an A-380 fly. They can almost make it sell!

They sure as hell can add the simple software change and they can do it cheaply.

Quoting Jetlagged (Reply 34):
The M in ECAM stands for monitoring, IIRC.

So you would be willing to allow a crash as almost happened just to prove the point - you were supposed to MONITOR that, dammit!

That is grotesque!

That you would be willing to smash 140 human beings to protein-jelly, then flambé their remains in jet fuel just to prove a point?

Just because it might take a week to design, two months to get into production and next C or D check to retrofit?

Look, we have proved time and time again that we cannot change, we cannot modify, we cannot improve HUMANS. In a thousand generations they have not changed perceptibly. They are just not wired to watch video screens at 100% accuracy. The entire point of invention, of engineerign, of system design is to take the human shortcomings out of it. Now you argue to keep a single human being responsible for the whole system just because... why?


It is not going to be of any comfort to the families of the people weeping over closed coffins that "at least we get to blame the copilot" Yep, "pilot error" fixes everything.

Grotesque!
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wilco737
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RE: Changing Feel Of An Aircraft: Pilots Perspective?

Thu May 01, 2008 5:24 pm



Quoting SlamClick (Reply 35):
It is not going to be of any comfort to the families of the people weeping over closed coffins that "at least we get to blame the copilot" Yep, "pilot error" fixes everything.

Grotesque!

Agreed! Pilots error is always the easiest explanation for a crash! And everybody has it's bad guy!

Quoting SlamClick (Reply 35):
They can make an A-380 fly. They can almost make it sell!

 rotfl  Yeah, almost  duck 

Quoting SlamClick (Reply 35):
They sure as hell can add the simple software change and they can do it cheaply.

And in my opinion it's a MUST to change it better now than later!!

WILCO737 (MD11F)
 airplane 
 
2H4
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RE: Changing Feel Of An Aircraft: Pilots Perspecti

Thu May 01, 2008 5:40 pm



Quoting WILCO737 (Reply 36):
Quoting SlamClick (Reply 35):
They sure as hell can add the simple software change and they can do it cheaply.

And in my opinion it's a MUST to change it better now than later!!

Airbus, take note - when such changes are implemented, compensation in the form of type-ratings may be made to the proponents participating in this thread. Contact me for details.

2H4
Intentionally Left Blank
 
BAE146QT
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RE: Changing Feel Of An Aircraft: Pilots Perspective?

Thu May 01, 2008 5:54 pm



Quoting SlamClick (Reply 35):
The entire point of invention, of engineerign, of system design is to take the human shortcomings out of it.

To reinforce the point, this is true of many automated processes. Take it from someone with 1st-hand experience in that field.

Automation is - depending on application - usually cheaper over time than using a human. If you're looking at the bottom line, you see that, not any ancillary safety/accuracy aspects.

But this is countered by the up-front cost of implementing a change in an existing automated system. The cost in doing so is all human, be it in effort or regulatory efforts. So the change doesn't get done, even if it reduces risk and loss, or increases safety, accuracy, or long-term expenditure.
Todos mis dominós son totalmente pegajosos
 
SlamClick
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RE: Changing Feel Of An Aircraft: Pilots Perspective?

Thu May 01, 2008 5:55 pm



Quoting 2H4 (Reply 37):
compensation in the form of type-ratings

Hey, I have a couple I'll give ya. World's second most perishable commodity right behind Christmas trees. No further use to me.
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tdscanuck
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RE: Changing Feel Of An Aircraft: Pilots Perspective?

Fri May 02, 2008 12:33 am



Quoting SlamClick (Reply 32):
So you ride on an Airbus and you bet your life that
(a.) Everyone who touches the flight control computer boxes, cannon plugs, wiring bundles etc. got all of it right AND
(b.) If they did get it wrong a copilot will rise above his normal human brain wiring and catch the reversal.

You completely skipped the fact that all aircraft maintenance procedures are supposed to be followed by a functional check.

Quoting SlamClick (Reply 32):

Now, no hardware needs to be added. They revise and update flight control computer code all the time. So add one line that says, in effect:
IF the airplane is on the ground
AND the sidestick or rudder pedals are moved to one stop
AND the associated flight controls move in the opposite direction
THEN a red master warning with CRC will be signalled.

It really is simple.

I'm betting a jury would feel exactly as I do about this.

I'm sure they would...which is why you get completely BS verdicts when aviation trials get in front of juries. What you're proposing is, essentially, that the OEM is liable for all possible ways that the airline can do their maintenance incorrectly. That one legal theory, by itself, would destroy the entire business model of the commercial aviation industry.

Quoting SlamClick (Reply 33):
The cost of the software change would be nil.

To Airbus, if financed the way you describe. It's not nil to the airline, who has to upgrade each airplane.

Quoting SlamClick (Reply 35):
So you would be willing to allow a crash as almost happened just to prove the point - you were supposed to MONITOR that, dammit!

That is grotesque!

That you would be willing to smash 140 human beings to protein-jelly, then flambé their remains in jet fuel just to prove a point?

I can think, off the top of my head, of dozens of ways to incorrectly maintain an airplane that would result in a hull loss that are not monitored or detected by the airplane. Should the manufacturer engineer each one of them out? And the hundreds or thousands of others that you could think up if you had dozens of engineers working on it?

Tom.
 
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Jetlagged
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RE: Changing Feel Of An Aircraft: Pilots Perspective?

Fri May 02, 2008 12:41 am



Quoting SlamClick (Reply 35):
Just be advised that a mediocre attorney could absolutely shred your argument in front of a jury.

Hang on, I was supporting your suggestion. I said it would NOT be difficult. Please read my post again and reconsider your reply.

Quoting SlamClick (Reply 35):
So you would be willing to allow a crash as almost happened just to prove the point - you were supposed to MONITOR that, dammit!

Supporting your idea again. ECAM is designed to automatically monitor aircraft operation, so adding automatic pass/fail for controls movement would logically be part of it. I was not talking about the pilot monitoring ECAM.
The glass isn't half empty, or half full, it's twice as big as it needs to be.
 
PITingres
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RE: Changing Feel Of An Aircraft: Pilots Perspective?

Fri May 02, 2008 12:54 am



Quoting BAe146QT (Reply 38):
But this is countered by the up-front cost of implementing a change in an existing automated system. The cost in doing so is all human, be it in effort or regulatory efforts.

Also, and this is something not often appreciated, software is discontinuous in a sense. A trivial change can have entirely unpredictable effects on seemingly unrelated parts of the program, and it's very hard to prove that the program remains correct. This is especially true when timing constraints are involved.

Of course, there are techniques for alleviating the problem or we'd never get anything done at all; but the fact remains that making a seemingly trivial change to software is totally unlike making an incremental change to a physical item.

Now ... I expect it's true that

Quoting SlamClick (Reply 32):
They revise and update flight control computer code all the time.

but I also expect that it's a rather more expensive process than generally realized. That is not to say that Airbus could not implement the suggestion:

Quoting SlamClick (Reply 32):
IF the airplane is on the ground
AND the sidestick or rudder pedals are moved to one stop
AND the associated flight controls move in the opposite direction
THEN a red master warning with CRC will be signalled.


Fair enough. Where I think Tdscanuck is going is that this is an essentially reactive process. You've spent expensive software update cycles on one problem. Ok, fine, and now some goofball wires something else backwards and we add another patch. Rinse and repeat. So, the question sort of becomes, is this a one-shot problem with a one-shot fix? Or are we getting into the business of chasing will-o-the-wisp's?

(I actually got involved in this game once, although it had nothing to do with aviation. A product I worked on in the 90's had an automated update procedure. Our customers would inevitably screw up the update in some new and bizarre method, and we'd waste time and money fixing it. Then, we'd have a big meeting, and say "in the NEXT update, we'll check for THIS and THAT and THIS OTHER THING, and it will be foolproof! And the next update would get broken in some even more bizarre manner. Over and over and over....)
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SlamClick
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RE: Changing Feel Of An Aircraft: Pilots Perspective?

Fri May 02, 2008 2:37 am



Quoting Tdscanuck (Reply 40):
It's not nil to the airline, who has to upgrade each airplane.

My airline pays Airbus for upgrades to flight control computer and other software ALREADY. Always has, probably always will. There are data loading ports galore in modern airlines.

And who gives a good God damn!

You are arguing in favor of human perfection to trap an almost uniformly catastrophic type of error.
I am dumbfounded.
Why would you do that?
To protect Airbus profit margin by 0.0000000000001% in this current quarter.

Honestly, why are you arguing against a software-only change. Not one piece of hardware would have to be added. Not one. Airbus wastes more than this painting stripes in their parking lot! Pennies to save lives and you continue to argue against it. I just do not understand your attitude.

Quoting Tdscanuck (Reply 40):
not monitored or detected by the airplane.

No no no! You don't understand. The airplane does monitor this already. It just doesn't do anything about it! It leaves that up to the pilots when there would never ever be a time when you would want the fail mode to occur.

Quoting Tdscanuck (Reply 40):
that the OEM is liable for all possible ways that the airline can do their maintenance incorrectly

No. Just when they are identified as real-world possibilities and as killers. Especially so when they are so cheap and easy to fix as this.

Quoting Tdscanuck (Reply 40):
which is why you get completely BS verdicts when aviation trials get in front of juries

This would emphatically NOT be a BS verdict.

Was Airbus aware of the problem?
Yes.
Did the means exist to correct it?
Yes.
Did they avail themselves of those means?
No.
What did they do.
Jack shit.
Thank you very much. [bangs gavel]

The truth is, it is the sort of attitude toward public safety that your arguments exemplify that brings lawyers and legislators down on what is actually a very good industry.

Quoting Jetlagged (Reply 41):
I was supporting your suggestion.

Sorry, perhaps I got a half-cycle out of phase. I was refering to Tdscanuck's argument that (apparently) it's too much trouble to fix it.

Quoting PITIngres (Reply 42):
You've spent expensive software update cycles on one problem.

I'm only aware of one, out of I don't know how many, software updates that dealt with only one single issue. Normally we get a summary of the changes and issue revisions to pilot handbooks and maintenance manuals to reflect them. They are going to be fiddling with that very software anyway.

So I gotta ask you Airbus, do you feel lucky?
Well do ya?
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tdscanuck
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RE: Changing Feel Of An Aircraft: Pilots Perspective?

Fri May 02, 2008 2:47 am



Quoting PITIngres (Reply 42):
Where I think Tdscanuck is going is that this is an essentially reactive process. You've spent expensive software update cycles on one problem. Ok, fine, and now some goofball wires something else backwards and we add another patch. Rinse and repeat. So, the question sort of becomes, is this a one-shot problem with a one-shot fix? Or are we getting into the business of chasing will-o-the-wisp's?

That's exactly what I was trying to get across. Thank you!

Tom.
 
SlamClick
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RE: Changing Feel Of An Aircraft: Pilots Perspective?

Fri May 02, 2008 5:02 am

Are you now saying that there was ONLY ONE WAY to have the flight controls respond incorrectly and it's been found and fixed?

I don't think that is the case.

What I am saying is that no matter how many possible ways, from miswiring, to spilled liquids to lightning strikes or chafed wiring as the planes age, where you might get a dangerous flight control response the passengers have only one last-chance check. That is when the pilots do the flight control check on taxi out. And the efficacy of that hinges entirely on a human doing something that, as is well-documented, humans perform badly at.

When all possible failure modes could have one extremely simple, dirt-cheap error trap applied in the form of a coded instruction that tells it to turn on a light and ring a chime.

And the argument against is?

It might cost money.
It might not be easy for the programmers to do.
If we do this we will have to fix ____
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tdscanuck
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RE: Changing Feel Of An Aircraft: Pilots Perspective?

Fri May 02, 2008 8:05 am



Quoting SlamClick (Reply 43):

And who gives a good God damn!

Well, you, obviously. Me too, although I suspect you don't believe me.

Quoting SlamClick (Reply 43):
You are arguing in favor of human perfection to trap an almost uniformly catastrophic type of error.
I am dumbfounded.
Why would you do that?



Quoting SlamClick (Reply 43):
Honestly, why are you arguing against a software-only change.



Quoting SlamClick (Reply 43):
I just do not understand your attitude.

That's because you don't understand my point.

I'm not arguing against the change...it's easy and simple. I'm arguing against your theory that all changes of this type should be fixed by altering aircraft monitoring. To whit:

Quoting Tdscanuck (Reply 26):
It would make a lot of sense to have this type of test written into the maintenance BITE for the flight control system..



Quoting Tdscanuck (Reply 29):
I'm not suggesting that this exact error is non-trivial to diagnose on the ground...as you correctly note, it's really easy.



Quoting SlamClick (Reply 43):
Quoting Tdscanuck (Reply 40):
not monitored or detected by the airplane.

No no no! You don't understand.

Actually, I do. You don't understand because you clipped that quote out of a much larger sentence that's talking about a completely different point:

Quoting Tdscanuck (Reply 40):
I can think, off the top of my head, of dozens of ways to incorrectly maintain an airplane that would result in a hull loss that are not monitored or detected by the airplane.



Quoting SlamClick (Reply 43):
Quoting Tdscanuck (Reply 40):
that the OEM is liable for all possible ways that the airline can do their maintenance incorrectly

No. Just when they are identified as real-world possibilities and as killers. Especially so when they are so cheap and easy to fix as this.

That was the point of my sentence quoted immediately above. There are, literally, hundreds of real-world killer possibilities that can be fixed by a simple engineering change and aren't.

Quoting SlamClick (Reply 43):
Was Airbus aware of the problem?
Yes.
Did the means exist to correct it?
Yes.
Did they avail themselves of those means?
No.
What did they do.
Jack shit.
Thank you very much. [bangs gavel]

Exactly...you're arguing that the OEM is liable for any problem they're aware of and had the means to correct but didn't.. That just isn't how aircraft are designed. No airline could afford to buy an aircraft designed that way.

Quoting SlamClick (Reply 45):
When all possible failure modes could have one extremely simple, dirt-cheap error trap applied in the form of a coded instruction that tells it to turn on a light and ring a chime.

For one thing, it doesn't cover all possible failure modes. For another, it introduces some new ones. As diagnostics go, I agree that this one is easy, but it's not nearly as easy as you're making it out to be.

Quoting SlamClick (Reply 45):
And the argument against is?

It might cost money.
It might not be easy for the programmers to do.

That isn't my argument at all. Hence my belief that you don't understand my point. That may be my problem for not communicating it well, it's hard to tell.

There are two key points:
1) reactively adding software monitoring to catch a triple maintenance error is not an effective way to reduce risk
2) the fact that an OEM is aware of a possible maintenance error and a possible engineering solution to that error does not make them liable for not implementing that solution

Tom.
 
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Jetlagged
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RE: Changing Feel Of An Aircraft: Pilots Perspective?

Fri May 02, 2008 2:18 pm



Quoting SlamClick (Reply 43):
Sorry, perhaps I got a half-cycle out of phase. I was refering to Tdscanuck's argument that (apparently) it's too much trouble to fix it.

Accepted, I understand.

Quoting Tdscanuck (Reply 46):
1) reactively adding software monitoring to catch a triple maintenance error is not an effective way to reduce risk

This is true, however, Slamclick's original point is valid, the crew will often see what they expect to see. Adding an automatic sanity check to ECAM (which after all is not part of the FCS) would be straight-forward, and could be added at with the next software revision. The cross-check need only run on the ground with the controls deflected.

The point is that the check can be done, so there is not reason why it should not be done. This is analagous to the fuel leakage mods that were made to the Airbus ECAM after that Air Transat A330 ran out of fuel.
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PITingres
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RE: Changing Feel Of An Aircraft: Pilots Perspecti

Fri May 02, 2008 3:36 pm



Quoting Jetlagged (Reply 47):
Slamclick's original point is valid, the crew will often see what they expect to see. Adding an automatic sanity check to ECAM (which after all is not part of the FCS) would be straight-forward, and could be added at with the next software revision. The cross-check need only run on the ground with the controls deflected.

I certainly don't argue with this, and I don't think anyone else is either. The change would be easy, as such things go, and would add a useful layer of protection.

Quoting Jetlagged (Reply 47):
The point is that the check can be done, so there is not reason why it should not be done.

But here, while I don't disagree exactly, I think we need to be very careful to agree on the scope of what we're applying this point to. Are we talking about an isolated incident, or are we talking about instituting a program?

It's one thing to say, here's this one problem, and we should try to catch it in software, for whatever reason. (because the consequences are sufficiently serious, or because it's really simple, or because we can't stand reading about it in a-net one more second, or whatever.) Well and good.

On the other hand, from a higher level perspective, saying "checks that CAN be done, SHOULD be done" starts to sound like a general course of action -- meaning, let's attempt to reduce risk by thinking of all the ways that maintenance can screw up, and let's try to add software checks for them. As a plan of attack, this notion has serious flaws, not least of which being that it's nearly impossible to anticipate all the different ways in which stuff can be incorrectly reassembled. Also, software has its own risks of being incorrect, and you'd better make sure that ITS failure modes aren't just as catastrophic as what you are trying to prevent. The more complex the software, the more chance it will be the problem rather than the solution.

I have to agree that as a program philosophy,

Quoting Tdscanuck (Reply 46):
reactively adding software monitoring to catch a triple maintenance error is not an effective way to reduce risk

I don't actually think that people are disagreeing on this topic, just that they are looking at it from different perspectives -- the pilot/maint incident perspective vs the overall program perspective.
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SlamClick
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RE: Changing Feel Of An Aircraft: Pilots Perspective?

Fri May 02, 2008 4:01 pm



Quoting PITIngres (Reply 48):
I think we need to be very careful to agree on the scope of what we're applying this point to. Are we talking about an isolated incident, or are we talking about instituting a program?

Perhaps I should be more clear about my position. I was talking about two things so maybe I can't be more clear.  Smile

Actually, I was referring to this one incident where LH very nearly crashed because of a few human failings and ultimately didn't crash because one final human eye-brain filter diagnosed it, literally on the fly and applied correct technique.

My point with this one is this:

Whereas there are probably tens of thousands of possible minor problems that could cause a flight control malfunction. And
Whereas they all come together at a last-chance check just before taking flight and
Whereas that last-chance check depends completely on the eye-brain of the less-experienced of the two pilots seeing, assessing and reporting on dozens of correct indications on the flight control page and
Whereas in the real world there has now been an actual occurrence of all pre-takeoff checks being sidestepped by a human-error control failure and
Whereas that event made worldwide news and
Whereas the causes and fixes have been widely debated in forums other than this one
Therefore it would be prudent of Airbus Industrie and their customers to fix that obviously weak last-chance filter on flight control problems.

I have survived three flight control problems (rudder battle damage, roll spoiler uncommanded deployment and elongated bolt hole in elevator circuit allowing horizontal stab to fly from one end of the hole to the other) and the very thought of them makes my blood run cold. They rank right up there with midair collisions for not leaving survivors. If you know about a problem you pretty much have to fix that problem.

None of the above should be construed as my advocating that armies of engineers should take an in-service airliner with a good record and analyze every possible combination of failures, hardware, software and human and try to compensate for all of them. There is not enough time left before the sun goes supernova to accomplish that.

The one in a million-millions scenario is probably acceptable risk - UNTIL a specific one emerges. Then it must be fixed.

And that's all I have to say about that. /gump
Happiness is not seeing another trite Ste. Maarten photo all week long.

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