"relaxed static stability" et al
 

I'll go out on my normal limb and tell all that the FBW system on the 'bus can't provide "simulated" or "apparent" static stability. The jet is either stable or not, and it is not like that little thing I flew long ago which was actually unstable until 0.95 M and depended upon HAL to keep the pointy end forward.

If we are talking about little or no speed stability because HAL is trimming for a gee versus an AoA ( just like the Viper), then you may think you have "neutral" static stability, but you don't. The 'bus has positive static stability throughout a good combination of cee gee versus center of aero pressure, but never has inherent aerodynamic negative static stability.

I agree with those here stating that it would never have been certified within any realm on the charts indicating negative static stability. Even AF447 showed positive static stability at 40 degrees AoA or whatever the exact value was. Push forward and eventually recover. What we DID SEE was an AoA and cee gee that allowed it to remain fairly stable while stalled, courtesy of HAL, which was constantly commanding nose up and trimming the THS to reach the nominal one gee command, hands on or hands off. Only forward stick and maybe manual THS trimming could have enabled a recovery.

God, but I would love to get some of you in my old jet and show you the differences between the older jets and one with a FBW system with all the "limits"/"protections" and fly it to the limits. Knowing a lot more about the 'bus now than two years ago, I would relish the oppo to do the same thing in the beast. As Doze is fond of reminding me, our jet was designed with different goals/missions. Nevertheless, it was the first one with FBW, no mechanical back up, and we all became test pilots for a year or two, even after 4 or 5 years of development and testing at Edwards.
out,

@MM43:

When ALT2'something' latches as a result of multiple 'ADR disagree', I can count down 1 knot at a time and when the difference between the 'median' ADR and the next closest reaches 19 knots, the FD's return and the AP 1+2 inop status is removed, regardless of the magnitude of the remaining ADR discrepancy. The A/P pb can then be engaged, even though ACTUAL speed (CAS) is below ACTUAL VLS. VLS is neither displayed nor indicated on the FMGEC landing phase PERF page. It is dashed and appears not to be computed.

As soon as I take the speed discrepancy back to 20 knots or above, the FD's go away and the A/P pb cannot be engaged.

Either I'm not really in ALT2B, which, on the surface, is problematic to determine, or there is a potential Level D problem, always a possibility, or 20 IS the magic number.

This is what I'm trying to determine. :confused:

C of G

There was quite a lot about C of G about a year ago in Thread 5 #394 ...etc. Some of it IIRC implied that fuel was transferred " in chunks" forward for use in flight whilst keeping the C of G within the normal "in flight limits" by some margin. I would guess that during the transfer of each "chunk" the aircraft would respond to the change of C of G with a change of speed or F/L , normally adjusted by A/T and A/P - but if these are not available then manual control would seem more sensitive.

( On a York hand flown, it could feel as though the passengers were playing cabin football, with a goal at each end of the cabin !)

John, yes I meant within aft CG limits if that was what you were asking.The LSS thing isn't familiar to me but it must have something to do with stability and CG. Us yanks use different terms so help us out.

CG at time of event:

CG is the red dot representing 28.7% Prior to TO it was 23.3%


http://i1166.photobucket.com/albums/q609/DaveK72/cg.jpg

God, but I would love to get some of you in my old jet

Yes, please. Only FJ I've been in was an RAAF ARDU Mirage in the early 70s and that was good fun.


The LSS thing isn't familiar to me

Apologies. (Longitudinal) Static Stability. Basic thing for (required) positive stability is

(a) maintaining slower than trimmed speed requires the pilot to pull
(b) maintaining faster than trimmed speed requires the pilot to push

Thanks John, I never encountered that way of approaching it before.

That's the way the testing and measuring is approached ..

The typical pilot training thing about strange balls in teacups is useful if explained appropriately but, near invariably, it is a case of the blind leading the blind and the explanations tend to be more fanciful than useful.

Stick force for positive static stability can be thought of in terms of "if I relax the load, the aircraft initially would seek to return to the trim speed".

In terms of balls and cups .. the analogy is "if I let the ball go .. its initial movement would be in the direction of the bottom of the cup".

Either way static stability is to do with the aeroplane's being at a fixed off trim attitude and looking at what it might want to do if you were to let go of the stick/ease off the stick load .. dynamic stability looks at what it actually does.

@OK465;Agreed!:ok:

But there is one more set of variables (includes CAS > VLS) to be confirmed before the A/P will actually engage, and that is not met. The logic presented by A33Zab clearly shows that with regard to the A/P the CAS/Pitch/Roll condition is the final inhibition - irrespective of FMGEC, other than when Pitch Angle Protection is active in Normal Law.

The BEA did retract on that but did not propose any other possible explanation ... ?
In a 6 seconds period, the captain said it once and the PNF twice - I cannot figure out what they were talking about ... ?
That's a period of time when the PF was full back stick !
BTW that part of the CVR has changed since the third Interim Report ...

Also, as mentioned earlier by Lyman, why the captain is telling "AP OFF" at time 2:13:53 ?
What is that 'bruit de selecteur' ... an AP that is selected would make such a 'bruit' ...

That BEA is really not curious, at least publicly.

Another point is that total confusion related to the vertical speed indications or possible intermittent lack of it.
The comments made by the crew suggest how that information was erratic when displayed ... How were behaving the altimeters ... ?

Otelli's book ?
I should read it before commenting further but have no intention to pay for that ... Any link for the CVR part ?

Thanks for the chart, Turbine, it's the one I used making my assertion that the jet was well within the cee gee envelope.

To JT, I tink you have to further explain about LSS. So if I am below the trimmed AoA, the plane noses up to get there all by itself if I let go. And vice versa. So trimmed for 80 knots in my Cessna and I am zooming along at 100 knots without re-trimming, then the thing pulls up if I relax the wheel/yoke/stick. U.S. nasal radiators like 'bird are very familiar with this, as it was the way they made their approach to the deck - they trimmed for AoA and used power to control rate of descent.

For the 'bus drivers here. you could try this in the sim, but the control laws would fight you. Normal law is not heavily biased for AoA, and the auto-throttle would thwart you. But I guess ya gotta play the cards that you are dealt.

So if I am below the trimmed AoA, (ie motoring along the aerial freeway faster than trim speed) the plane noses up to get (back) there (somewhere near trim speed - within a reasonable tolerance) all by itself if I let go (strictly, if you ease off the stick load gradually). And vice versa. So trimmed for 80 knots in my Cessna and I am zooming along at 100 knots without re-trimming (but holding a pretty decent push stick force as you descend - test normally would be for a fixed thrust setting), then the thing pulls up if I relax the wheel/yoke/stick. U.S. nasal radiators like 'bird are very familiar with this, as it was the way they made their approach to the deck - they trimmed for AoA and used power to control rate of descent.

[My red additions above for additional wordiology confusion].

The current test procedure for FAR 25 is given in the FTG AC 25-7B starting at page 109.

Similarly, for Part 23, the FTG is at AC 23-8C starting at page 78. (be warned - 14MB)

Imho some of you are on the wrong path concerning the stability issue.

Fact is, that BEA brings in the "neutral stability" issue and they wouldn´t have done it for no reason.

This neutral stability is not a built in by design into the airframe or caused by shift of CG (trimtank), it is done by managing the position of aerodynamic pressure by the computers with the elevators in the short term and the THS in the long term. Therefore i did use the term "natural" and "artificial".

Gums described it in his words.

While the new generation of combat jets are "natural unstable" and are made stable by the computers, it is quite different in the A330. It is natural stable with positive static stability (See the graph posted by TurbineD) even when computers change CG a bit by transfering fuel to or from the trimtank. With the automatic THS trim besides the elevators the computers have a formidable tool to change the aerodynamic pressure, hence the airframe is kept in neutral stability all the time.

In a conventional aircraft it is the same situation when you have the aircraft perfectly trimmed, with one big difference. The trimmed conventional aircraft is speed stable and will return to equilibrium if disturbed out of that trim condition, the discussed A330 is not speed stable but flightpath stable within limits defined by the built in flight envelope protections.

At least BEA mentions this neutral stability, wether as excuse for the problems the crew faced, as a hint to the manufacturer that the reversion sequence and the documentation needs a look up, or as a hint to better training and understanding of the resulting flight behaviour when vital inputs are lost? Or any other reason we can think of.

As described, here with the A330 it´s vice versa. The aircraft has a natural positive stability, it needs the computers to keep it in the neutral region.


Imho the "Nil Box Assistance" is not the problem, as the aircraft would then (with manual THS trim) be a natural positiv stable airframe.

The problem here is, that with all protections except load factor protection lost the aircraft was kept in this neutral stability by the computers and the crew could not cope with the responsiblity to keep the aircraft within the flight envelope.

See RR´s post below.

Exactly

Imho not necessarily, as explained before. The aft CG helps in saving fuel, but is not necessary for creating the neutral stability. The continuous autotrim is creating this permanent neutral stability with the help of the box.


The CG doesn´t change except for the fuel in the fin, the location of the center of aerodynamic pressure is constantly changing and keeps the aircraft in neutral stability until the degradation drops into direct law. Then you might have an aircraft completely out of trim, but it is basically now an aircraft with positive static stability. As in direct law only the trim wheel is available for longitudonal control, you wind it where it needs to be and the aircraft would be no longer flightpath stable, but speed stable.

Whereas in ALt law2 the aircraft was still kept in neutral stability by the box and was flightpath stable, but the necessary protections to make such a system safe (including the backup system "aircrew" ) were not working, thus leading to the flight-envelope excursion.

True for a conventional aircraft, ts different here.

I hope Owain Glyndwr can cut in and correct where i´m wrong or to add where necessary.

Hi JT,
Ref your post 594

I've confused you with the wrong terms.
The aircraft feels like it is neutrally dynamically stable in normal law, and slightly positively stable in ALT law.
The only time we feel Direct Law is after the gear is down. I've never handled it at aft c o g in direct law, but presumably the gear drag couple would help.

Franzl,

I am uncomfortable with your thoughts regarding neutral stability although I have no problem with the Airbus's maintaining a constant flight path hands off.

Indeed, one of our PPRuNe number was in the Regulator's FT chair when the A320 was introduced to AN in Australia and he was quite ecstatic about the aircraft's capabilities at the time of Australian certification.

However, I acknowledge that my FBW knowledge is limited so I guess I will have to dig into the books and read up some more on FBW bits and pieces ...

John T,

there are differences between the A320 and the A330, also concerning the reversion of laws.

I´m not sure wether i should be uncomfortable about the system itself or about the general knowledge about those systems and the asociated training by some operators including their crews.

Franzl,

The general dumbing down of things piloting is an extreme worry to most of us. If the systems design folks could guarantee that they get it all correct (which, of course, they can't .. and don't) it might be a different matter .. but, until they can, the folks up front are the last ditch defence and if they don't know much beyond "light A ON .. button B PRESS" we are better off going fishing.

The beancounting fraternity has a lot to answer for I suggest.

[Thanks for the PM offer]

Understanding "speed stable" versus "flight path stable"

If the driving concern is "flight path stable" then I'd gather that the system makes small speed corrections, or small corrections that manifest themselves in small airspeed changes, continuously. These changes would dampen until they reached vitrually zero when we reach desired altitude and mach/speed for a given sector of the flight. This would include automated and minor corrections of the power setting as part of this flight path seeking method.

Do I understand your explanation correctly, or am I simply confusing myself?

To whomever posted flight global article: thanks! :ok:

This provides me with a very nice explanation points for some of the laymen I know who are curious about this accident.

You know, this is a broader cultural issue. We are seeing the exact same paradox in medicine. Everything is being reduced to autopilot with clinical pathways and guidelines. This approach inevitably de-emphasizes critical thinking, and clinical decision making skills are being lost as a result.

This approach standardizes care and produces better outcomes - most of the time. And so risk managers and administrators and legal departments love this stuff.

But (and there is always a but), if the patient gets misdiagnosed and put on the wrong pathway, or if the pathway does not address an uncommon set of circumstances particular to an individual patient, the physician is left with nothing to fall back on.

The physician blames the author of the pathway for not anticipating an unusual scenario, the managers blame the physician for not recognising s/he was out of his depth. The solution is to invariably to revise the guideline - because that is the only component of the system amenable to change.

And so it will be with AF447. Some improvements will be made to the automation. And they will be an improvement. But the underlying problem will be papered over.

Some change of spped and heading
 

In the building business, a similar 'pathway' process is utilized. The concept is called the critical path, and sounds similar to the approach in medicine. It is applied in each project, drives scheduling and assessment, and must be monitored constantly by process (project) managers.

If applied (very) loosely to 447, one starts to appreciate the British expression: "losing the plot". I hope the comparison to construction does not offend, in Medicine, as in Aviation, lives are on the line moment to moment, and generally, losing the critical path does not cost lives.....

But in investigation, the critical path is apt, and perhaps could be used to better results if it were applied....

It depends wholly on the mission.

@OK465:
 

AMM 22-11-00 PB 001 AUTOPILOT/FLIGHT DIRECTOR (AP/FD) ENGAGEMENT D/O.

Par. 2.C:

• AP engagement is inhibited when abs(phi) > 40°
• AP is automatically disengaged when abs(phi) > 45°.

- Pitch angle

• AP engagement is inhibited when theta < -10° or theta > +22°
• AP is automatically disengaged when theta < -13° or theta > 25°.

(b) AP engagement is inhibited in flight when CAS < VLS or CAS > (VMO/MMO or VLE/VFE).

(c) AP engagement is inhibited when the FMGEC receives the "pitch angle protection active" information from the FCPC.

slats11;
Yes, a very good observation indeed. Medicine and aviation have a great deal in common when it comes to "passenger/patient" care.

We could say it is cultural but I think of it also as a political economy which has been developing since the early 70's, sometimes loosely known as "neo-liberalism" - the notion that privatization, de-regulation, and "free enterprise" will provide "market solutions" for all problems including the ones you have just outlined.

Nothing could be further from the truth and further from what is needed.

Like all social/economic phenomenon it's not all bad but recognition of the worst effects of a neoliberal political economy in the areas under discussion is only now taking hold.

If the regulators of the western world are not tuned into these notions, massive safety initiatives like SMS could be the de-regulation of safety rather than an enhancement of safety using modern data technologies and new knowledge regarding psychology and human factors in high risk enterprises.

The notion of "ethics" has all but evaporated in this fundamentally-instrumental economy. It is a shame that the term "business ethics" is often joked about as an oxymoron. However there are encouraging signs of change, beginning first with awareness that untoward outcomes in high-risk endeavours do not favour high profit or shareholder satisfaction nor do such events sustain the viability of an organization which normalizes deviance for short-term solutions.

A "prescriptive" approach where responses are patterned, quietly assumes that given sufficient rules and flow-charts for programmed diagnoses and actions, that anyone with a bit of bread-and-butter training, (MCPLs...), can be plugged into a sophisticated system even within a high-risk environment, and succeed.

The notion of automation is a social phenomenon, not a technical description.

A flow-chart process works for ordinary cases, as you say and it does save time, money, guessing and lives.

But the regulators often hearken to, and follow, private enterprises' ways, and, assuming that prescriptive approaches actually work, download expensive responsibilities which are the rightful pervue of government, onto profit-centered organizations, assuming that they will willingly and effectively monitor themselves and act in safety's best interests. Further, none of this requires experience but mere adherence to policy and procedures. An audit by the regulator sometimes seems more focussed on process and documents than it does on "smelling the health" of the place.

A lot of people really believe that this approach works but try telling a VP of Flight Ops who's knocked around aviation for a lifetime and knows his or her stuff, that kind of nonsense. It is an aid for quick reference, not a replacement for knowledge, training and experience, none of which are valued nearly as highly today as a nice, organized shelf of perfect documents in everyone's office.

This isn't to denigrate the changes - I think in many ways they're better now. But addiction to paper and process without watching and knowing what's actually being done and not just written or said, makes the difference.

I think, as the saying goes, that those chickens are coming home to roost, but private enterprise, with government's assistance through and relative absence in the past, (it seems to be changing...but how?), and the elixir of short term profit, have taught the travelling public that airlines can fly people safely for $59 one way and that complaint is legitimate when airfares differ or increase by the cost of a McDonald's happy meal. Such standards are going to be extremely difficult to alter when the factors we are seeing against the background noise become stark.

I wrote the following on automation and pilots earlier this year:

Standards, the notion of professionalism and the career and the job of “Airline Pilot” all have changed since de-regulation, even more so since the 90’s, almost singularly through the hands of non-aviation, finance people.

These changes were likely well-meaning, intending to come to terms with economic challenges in an increasingly deregulated, speculative political economy. But the effects must be examined for what they are, not what was intended.

The present environment makes it very difficult for airline executives to plan and finance an industry which by its nature requires very heavy capital investments over long periods of time as well as investor patience.

Downward pressures on costs, wages, benefits and pensions remain significant on those areas of an airline’s operation which remain most “flexible”, in terms of reducing costs. The most “flexible” of all tend to be its labour force. The effect is now familiar to all employees, known as ‘the race to the bottom’. The relationship to fares and fare structures, outsourcing, reduced regulatory oversight and other factors is complex and well beyond examination here.

From a flight safety point of view, the effects of wholesale cost reductions in a high-risk enterprise usually do not show themselves right away and so they appear to be justified because “nothing happened”. The immediate rewards are, costs were ‘successfully’ reduced and the department manager looked good and met his or her quarterly reductions.

Quarterly Reports may be important to the life of the corporation but only convey a financial snapshot. Other systems reflect the health of the organization but they are rarely “attached” to the organization’s fiscal statements.

The effects and the results of a fiscal “cutting to the bone” on flight operations may only emerge years later. Changing trends in incident or accident rates are thus disconnected from their origin. Solutions may thus be incorrectly informed.

Is “automation” the problem?

Many observers, including pilots, have already stated that automation itself is not the problem. Having flown such automation for many decades I agree with this view.

Automation is just part of the kit for flight crews. The approach was always, “We fly an aircraft, we do not "manage a software platform". Just because a technology can be created to accomplish something does not mean that it should be adopted as natural or inevitable. Automation is a conscious choice made primarily by airlines and manufacturers and is essentially an economic one with flight safety benefits.

I and my colleagues were comfortable with automation because, as a colleague has stated, we flew older generation aircraft and knew how, and automation was an “add-on” which, like anything in an airplane, was always watched carefully.

We had the attitude that “the airplane was trying to kill us”; perhaps blunt but it remains an effective attitude for aviators, especially when the obvious benefits of full automation were in some minds beginning to eclipse the utility and even the definition of “pilot”.

In the seventies and eighties almost every departure and every arrival was hand-flown, sometimes to and from cruise altitude. Except for those flying versions of the B737 and MD80, nobody entering the profession today does that, nor is it emphasized anymore.

Encouragement to hand-fly and the “freedom to practice” was always offered by captains who knew the value of remaining cognitively engaged and situationally aware. However, very few took up offer, citing discomfort, especially when disconnecting the autothrust.

Automation was engaged just after takeoff and disengaged at around 400ft just before landing, just like the FCOM required.

In fact, one hand-flew the airplane at some risk should an incident have occurred while doing so. Hand-flying was, and remains, discouraged by airlines. It is not automation that is the problem – it is the absence of piloting the airplane, a physical and psychological act which creates a cognitive situational awareness that is not available otherwise.

I think a historical misunderstanding of what automation does and what automation’s capabilities are, which are quite spectacular and wonderful in my opinion, is quietly replacing a corporate understanding of what flight crews do and what their job and what their profession is. This shift in attitude towards pilots as "almost redundant to automation", has translated into a silent legitimation of what in some cases is inappropriate cost-control initiatives including the unwillingness to pay reasonably and otherwise ensure a reasonable career. It wasn't hard to imagine the outcome: Young people have taken note and are avoiding aviation as a career.

Because training is enormously expensive, (crews are non-productive during training, training itself is costly), time spent in training is focused on the one thing that is perceived to reduce costs, and that is automation.

As well, automation is viewed by the industry as a fatigue-management tool, (“the airplane flies itself” thinking), and therefore justifies reductions in both augmented crew requirements (in terms of how many) and the qualifications of those doing the augmentation, (in terms of experience and training). In fact automation is a superb fatigue-management tool, used appropriately but it is not “the third (or fourth) crew member”.

Because of inherent accuracies and predictability, ATC accepts and views automation as a flow-control and accuracy tool and, to accommodate greater traffic demands (in both time and space), design SIDS and STARS which have tighter tolerances for altitude, speed and route control, requiring the use of automation to ensure accuracy.

Automation’s complexity and training costs (crews are non-productive while in-training), requires that most recurrent training time in the simulator is spent in automatic flight. It is extremely rare to be given a hand-flown, raw-data, manual thrust ILS to limits. Hand-flying at altitude is simply never done; even the Emergency Descent (after a depressurization or verified bomb threat), is done on the autoflight system.

There is no time formally set aside for hand-flying and practicing one’s instrument scan. The expectation is that professional crews will develop this skill for themselves. The failure in such thinking is, there is no opportunity afforded to do so, not, at least, without risk should an incident occur.

The almost-complete absence of hand-flying has led to a state of affairs not discussed in the industry or by the regulator until AF447. While airline pilots flying international overseas routes might “fly” 700hrs per year, 99% of the air time (excluding takeoffs and landings) is under automation and actual manual stick time is only about 3 to 5 hours per year.

There are about two to five minutes during takeoff and initial climb in which the airplane may be hand-flown, (on autothrust), and between 40 seconds and two minutes during the approach and landing.

On international routes that would be done twice, perhaps three times per month. Domestic flights do more flight legs per month, but I cannot speak to how much manual flying is done.

An RP, (Relief Pilot) will fly manually even less because of the nature of the job and the qualifications, (Air France’s RPs are trained to take off and land. In Canada, the Relief Pilot is not legally permitted to sit in the front seats below cruise altitude. Therefore, a Canadian Relief Pilot receives no training in takeoffs or landings except in initial training. In one operation I am familiar with the Relief Pilot is trained to do the Emergency Descent from the left seat when relieving the captain.

Flying an airplane, either under autoflight or in manual flight, are cognitive and physical skills which must be practiced, but we have an industry which continuously is reducing the opportunity and the legality of hand-flying.

Automation as non-paid labour – the “third pilot” syndrome

The perception is largely held by non-aviation people who manage the business of aviation that "these airplanes fly themselves" and that the computer got passengers to their destination, safely.

This perception subtly opens the door to cost-saving notions justified on the basis of utility and safety. The matter is far more complex. There is risk in portraying this state of affairs as an industrial and an economic issue. It is such a matter but only in part.

The notion that ‘automation reduces the need for pilots’ has slowly translated into legitimation of changed (lowered) hiring standards, lowered wages and, importantly, a loss of those financially intangible but psychologically-critical factors such as professionalism and its associated sense of “the apprenticeship” when bringing new pilots along.

This process has become self-justifying and is now self-sustaining. In fact the goal of papers like this from many people who do this work is to intervene in this recursive process by answering the question about why the character of accidents is changing.

Another side of this is awareness is, the career, (and the industry itself), has become especially unattractive to young people who find they can do far better elsewhere. Captain Sullenberger spoke eloquently of this in his February 2009 presentation before Congress.

In speaking with senior executives in the business (major carrier) who regularly visit the flying schools and universities from which airline pilot candidates come, I hear that they are seeing a significant dwindling of pilot entrants. Young people are not coming into the profession.

Those visiting the schools say that the passion for aviation has been lost. They know that such passion has been taken advantage of and young people now know how corporate values degrade the profession. As a result they are going to more rewarding jobs, careers or professions to earn their living. This is not necessarily about capability and talent; it is as much about attitude as anything.

Downward pressures on regional carrier pilot wages are significant. We know that the First Officer on the Colgan Q400 was earning US$16,000/year. She was living at home with her Mom and Dad near Seattle while commuting to fly out of Newark. These circumstances have been unfolding over the last thirty years and are not the result of recent events. These circumstances and low wages are common in the commercial aviation industry.

There is another factor in the development of a professional pilot which has been lost and that is the notion of “apprenticeship”.

With regard to the Colgan accident, there was no one within this organization teaching their young First Officer how to be a professional pilot. This lack is not unique to one airline.

There was no one, including her captain, who was teaching her, for example, that texting during taxiing was unprofessional.

Should she have known it was unprofessional? Young and old are endlessly texting and talking on cell phones, while driving cars, operating trains, ships and heavy equipment. Today in our culture it is “normal”. We must ask, Wither “professionalism?”

Defined in law, the Colgan First Officer was “qualified” and passed flight tests but that is where her professional development stopped. I have deep empathy for this First Officer and all new entrants to our profession.

The changes required are not ours alone to make, and they are not all merely “technical”.

B-Schools and an MBA degree do not teach business leaders about the principles of aviation, perhaps nor should they. But those entering aviation at the executive level do not innately possess an understanding of how high-risk enterprises are made safe and they need to to be able to provide leadership in non-finance areas of an aviation operation.

What is good for shareholders and what looks good on quarterly reports often does not present a full picture. The notion of “risk”, if broached at all in such reports, is only framed in the fiscal discourse.

The nature of aviation accidents has been changing. We know that there is an increase in loss-of-control accidents. We are starting to see why this is so but the question requires a change in perspective. Automation is neither servant nor master; automation is kit.

Sorry for the length slats11- these issues beg to be discussed, perhaps in other forum threads but I wanted to echo your concerns as part of the discussion on AF447 because I believe there is a relationship.

The Actual Cause of the Crash
 

Absolutely brilliant article, PJ2! I humbly suggest that you submit it for publication. Your political/corporate analysis is astute.

This is the true cause of this awful crash, and likely more to come.
(At last I reveal my stripes.)

Franzl,

There is not a lot I can add to your remarks, but I can't resist an invitation ;)

The BEA wording is rather loose, but I think the context indicates that they are concerned with static "speed stability" rather than classical short period mode.

It is fundamental that you can change/control either speed or flight path by the use of elevator alone, but not both at the same time.

So JT's description of "pull to reduce speed, push to increase it" is fine for classical airplanes or the A330 in direct law, but it rather loses meaning when stick movement commands a flight path change. Even more so when the implied pilot's command on releasing the stick is "Hold this flight path". With the flight path being held by the FCS any pitching moments are taken care of by the automatics so the CG to aerodynamic centre moment arm isn't really a great concern for speed control. For what it's worth, the aircraft would have to be statically stable in pitch to get certification. Moreover (and I am not sure of my ground here) I think they might have had to show that it was flyable for extended periods in failed states to get EROPS clearance.

Speed stability on the A330 in normal or alternate laws is therefore a rather different animal to what we were all brought up to understand.

As I said previously, it looks as if the aircraft under normal or alternate laws would be more or less neutrally speed stable over a fair range of airspeed - say from 200 kts to 260 kts - and increasingly speed stable above that (Mach 'tuck' effects excepted - but they seem to be modest and it doesn't affect AF447 anyway). Below about 200 kts the aircraft would be increasingly speed unstable because it would be flying up the back side of the drag curve.

The problem, as I see it, is that if the FCS is trying to maintain 1g flight when the airspeed is falling it will apply NU pitch. But even though the aircraft is descending rapidly the measured 'g' (without pilot input) may not be all that far away from 1.0 so that NU command may not be all that big (I'm not specifically relating to AF447 here because there was considerable pilot input on those traces). In such a case the attitude might not change much even though the airplane was decelerating and the AoA increasing rapidly due to the increasingly negative flight path angle. I think this is what the BEA are getting at.

Neo-liberalism
 

Right on the spot PJ2 !

What we are witnessing in the aerospace industry today with deregulation and enforcement of regulations by those that have all kind of incentives to watch the other way is also SOP in others high risk industries such as oil, nuclear power and banking.
In the end, the golden rule of neo-liberalism is always applied : privatize profits and socialize losses !

Back to the thread, the recent discussions about "stability" are much more interesting than the senseless ramblings about BEA / Airbus / AF / French State hiding the thruth from the unsuspecting public. Thanks to all for these knowledgeable inputs on that matter !

Why should that be "senseless" ?

I'm afraid it would make sense for all mentioned parties to hide the truth or at least some aspects.

Senseless
 

Hetfield,

Because against tremendous odds (A/C lost at night, in the middle of an ocean and in deep water), BEA / Airbus / AF / French State spent months and millions of bucks to find the wreckage. And they found it ... just for the sake of hiding the truth :ugh:

A330/340 A/C have flown more than 30 000 000 hours since their entry into service. No doubt that BEA / Airbus / AF / French State need to hide the fact that it is poorly designed and full of traps for unsuspecting pilots !

@A33Zab;Though PAP is "lost" in ALT and DIRECT Laws?

So your logic schematic is still correct for all conditions.

Thank you, OG, for your contribution.

There's one helluva difference between speed stability and longitudinal static/dynamic stability in the FBW jets that emphasize gee compared to what many of us learned back when the Earth was still cooling.

The 'bus does not change the center of aero pressure using the control surfaces or the FBW system. The crew can change the cee gee by transferring fuel or having all the SLF's run back and forth, but the aero remains the same. Maybe the F-111. F-14 and Tornado could actually change the center of aero.

The big deal is that one can reduce the downward lift from the elevators/THS in order to gain fuel efficiency and such by moving the cee gee aft. The jet does not come anywhere close to the tiny one I flew in the dark ages of FBW. As an example, we manually transferred fuel once the deep stall phenomena was verified. This gave us a forward cee gee and supposedly help keep us outta test pilot land. Unfortunately, we would forget to re-position the fuel transfer switch back to "normal" when coming home after initially placing it in "aft fuel transfer". Hell, we were joining up and changing IFF codes and all that stuff. The procedure was not in our checklists, either. So we would have an unbelieveable aft cee gee. I only weighed about 135 - 140 pounds naked, and maybe 150 pounds with survival gear on. Our nose gear WOW would intermittently disconnect our nose wheel steering. So one day I stepped off the ladder and the jet started to tilt back on the engine exhaust nozzles!!! Crew chief and I grabbed the nose and I stepped back on the boarding ladder!!! Still laugh about that. But my point is that no jet ever built could have been flown with that combination of cee gee and center of aero pressure.

Gotta go, and some good discussion here. I'll address PJ's point paper later, maybe a separate thread.

I will counter with this.

A market solution has never been tried.

A market solution would exclude government "oversight" in all ways and safety would be dictated by the customers. In such an environment, airline X could sell tickets based entirely on price and airline Y could sell tickets on properly maintained birds - properly trained pilots - adequate fuel loads, etc.

I'm not necessarily endorsing such a solution, but it certainly has not been tried up to now.

The premiums required by the insurance industry in this X versus Y scenario would IMO work very rapidly to restoring something close to the status quo.

Estimated price of all searches is 18 million Euros
A330-200 factory list price (2010) is 191.4 million dollars
Everything is relative ...
The price of research is not very high for the sake of (maybe) increase the safety of flights

Not really. The fallout of the DC-10 "Gentlemens' Agreement" proved that if you try to deal with problems surreptitiously, it *will* come back and bite you in the empennage.

I think by "active" it means "engaged and working" rather than merely "armed and ready". This makes sense because you don't want autopilot commands muddying the waters when you're in that situation.

You rode the F-16 bareback? Duuuude! ;)

To all intents and purposes it has, and the result was the Great Depression.

Except that's not how it works though. What would in all likelihood happen is that your hypothetical "Airline X" would undercut the hypothetical (safe) "Airline Y", and because of the technological and safety advances, X would get away with shaving safety margins for some time - probably long enough for Y to go out of business, with X taking over the routes and heading towards a monopoly. By the time something catastrophic happens to X, either it will have become a monopoly (meaning the choice is X or nothing), or the only remaining competing airlines will also be price-driven - meaning if the accident puts X out of business, the only remaining players are much the same.

The problem with all these modern "free-market" theories is that they don't take human capriciousness into account.

@PJ2 : :ok:

A33Zab:

I understand what you're saying and I thank you for the info.

However, it's not what I'm seeing, and it leads me to question either the fidelity of the simulation, or the 'applicability' of the guidance in 'all' circumstances.

In the interest of quality simulation I'm not quite willing to accept either one or the other just yet. :)

Dozy, I think that if the legal liability, and hence the insurance costs, are included in the “market” place for airline X, X may not be cheapest after all. This would depend upon somebody persuading the insurers of the x-type risks, and providing enough quantitative data for actuaries or assessors to put a price on it, but insurers are a conservative lot and price highly for unknown elements.

(Edited to add – In fact, when the legal costs are finally added up for Air France, I would not be at all surprised if the savings in training with no manual flying at cruise altitude, lack of UAS comprehension, poor CRM etc. are exceeded by the costs.)

I somehow doubt that the mods want this to turn into politics. My argument was micro, not macro and we're talking about aviation not world economies.

This market solution, how is it working out for all the people who live, walk, loiter or posses land and property under the flight and potential crash paths? Will the airlines have to get individual permission from each of these people, pay life insurance for them and compensate individually for noise and other emissions? Who owns the air the airlines obviously need for their business, who "rents" it out to them, at what price, who sets the conditions?

The problem is that RPT air travel is so safe that most carriers ( with a few notorious exceptions) look much the same regarding safety to the average person. The inflight experience is much the same. The schedules are much the same. This has left price as a key discriminator for a large section of the market.

In this environment airlines must compete on price. The growth in LCC is evidence of this. Legacy airlines are cutting costs where they can. Using offshore cabin crew, offshoring maintenance and eroding existing terms and conditions are examples of this.

I suspect some managers are concerned about degraded pilot skills. But they are between a rock and a hard place. There is no point being safe if you are out of business. Other managers do not understand and will not listen.

And so everyone is playing the odds. Air travel is still pretty safe even with a few corners cut. The planes and the wider system are safer than before. And hopefully this will be enough. And it almost always is.

In the event of a disaster, various conventions will serve to limit liability. And the causes will be sufficiently complex that the blame and costs will be shared. That's how the risk managers and lawyers view it.

Market forces at predicated on an informed market. This is not the case here.

It would be great if the insurers sent a price signal. They likely do up to a point, but only up to a point. Insurance is most efficient with a frequent number of smal claims ( auto accidents or heart attacks). The high frequency allows accurate determination of risk. That is not the case with infrequent catastrophic claims. Insurers manage these through exclusions (acts of God, war etc) and also through reinsurance.

With airlines, crashes are rare and so insurers have difficulty determiniing the risk to apply. AF however may have now had a sufficiently bad run that the insurers will see hem as high risk.

If premiums really offset savings from corners cut, then LCC wouldn't be growing as they are.

mm43:

IMO they mean: activated (in NORMAL LAW θ <-15° or θ >25/30°)
This is outside APs own Operational Conditions θ >10° and θ <22° which are also valid in ALTERNATE.

OK465:

Text is from AMM, but you have reason to question this based on your sim experience.

Are you able to verify this in NORMAL LAW condition in the sim?
AP & A/THR off,
NORMAL Law (to make sure VLS available),
fly CAS<VLS-5 and then try to engage AP....?