takata

Hi Confiture,
First, yes, I guess that we are reading the same report, but I'm trying to include every available informations from it, not only a single quote about the general case above that you underlined from it.

Second, the point is mostly to understand what we already have, before even going further with new data when they will be available (soon).

So, my initial point was to link those ACARS with real cockpit events:

1. Event started at 0210:05 with AP/FD and A/THR faults;
2. Event is due to 2 or 3 PITOT-PROBEs (total pressure) faults affecting some of their respective ADR outputs (barometric altitude, speed, Mach, angle-of-attack, temperature and overspeed warnings);
3. Those PITOT-PROBE faults caused all the following 0210 ACARS to be reported;
4. ALTERNATE LAW 2 was consolidated after monitoring, it was not transient;
5. 2 or 3 ADRs were rejected by FCPCs and FMGCs;
6. There was no "ADR DISAGREE" triggered during the 0210 sequence;

Hence, it may be deduced that it was due to a "triple ADR" fault:
=> ADR 1 + 2 / ADR 1 + 3/ ADR 2 + 3 (ECAM)
=> ADR 1 + 2 + 3 (not displayed by ECAM)
Consequently, Low and High Speed protections were lost while "SPD LIM" was flagged on both PFDs without VSw and VMax displayed.

- ADR 1 & 3 were coherent and valid again before 0211:06.
- Another triple ADR fault sequence started "after 0211:40";
- All speeds became invalid again;
=> It may be assumed that aircraft's airspeeds went below 30 kt, they would not be displayed anymore on both PFDs between 0211:40+ and 0212:19+
=> It may be assumed that "ADR DISAGREE" was triggered after this second triple fault was cleared.

CONF iture

Ground speed is affected, but not airspeed.
Once airborne, the glider is in the air mass that is moving at the speed of the wind, but for the glider itself regarding that air mass, there is no notion of tail or head wind.

takata

See my post above. Low speed Stability, VSw, (and associated speed stall warnings) would only be available with two ADRs being declared valid, which might not have been possible before 0211:40+. Moreover, if it has been available before or after this point, it would have triggered "DIRECT LAW", whatever imputs made by the PF in order to counter those active ND protection imputs. Quite frankly, there is no trace of "Direct Law" and this never happened.

No (first question). Yes (second one). All events involved 2 or 3 ADRs faults, this ruling out "Low Speed Protection" (other have been transient, hence, the system would revert to NORMAL LAW and this protection doesn't apply). Moreover, not a single aircraft ever made a single excursion out of its flight envelope.

Lonewolf_50

After reading post #661 ...

Following so far, these protections are features of Normal Law.

Caveat: the following informed by sources that are between 5 and 10 years old.

When the pilots noted "Alternate Law," speed stability functions should have been in play if they were in Alt 1, but not Alt 2.

The system needs two valid ADR for stall warning and low speed stability.

I look at the FMA, and try to figure out if alert to "Alternate Law" is in one of the five fields above the attitude display, or on the ECAMS page. I cannot. (Don't have anything that tells me.)

Stability function can make inputs but can be overridden by the pilot's inputs.

This makes me wonder: did the crew know if their state was Alt 1 or Alt 2? (There may be more on CVR that will clear this up from next report, but there may not. Likely their work load was up, see below, and as such precluded any discussion as to which Alt mode was in play).

If PF didn't recognize alt 2 versus alt 1, would that have made a difference in how PF made and monitored nose inputs? My guess is no, but it's a guess.
(Question based on not having flown A330 ...)
This leads to the question: were the pilots aware of this?

Perhaps the next reprt, and CVR analysis, release will shed light on that question. Perhaps task load precluded such a realization.
From June 2005 revision of the Flight Crew Training Manual (8.110.3)

"... if all three ADRs provide consistent and erroneous data, the PRIMs and FEs will reject the “good” outlier ADR and will continue to operate normally using the two consistent but faulty ADRs."

Interestingly, in another section of the manual (2.60.11)
DIRECT LAW - In most cases of triple failure, e.g. triple ADR failure, direct law is triggered. Autopilot and auto-trim are not available.

One hopes that the various cases are handled in the simulator training sessions.

I also note that around pages 2.30.5 through 2.30.8 some ECAMS crew coordination is disucssed.

The process by which a crew clears ECAMS alerts is organized and formalized, but I see a source of possible scan disruption for the PF in this process, based on standard procedures for clearing ECAMS alerts.

ChristiaanJ

HN39 and CONFiture,
Your aircraft is not purely a feather blowing in the wind, it has a certain amount of inertia. Usually more of an issue during windshear, rather than while turning from downwind onto finals....
I would suggest the subject is mostly O/T here, and could maybe do with a separate thread on TechLog to kick the relevant notions around?

CONF iture

• Should not we have expected a relevant ACARS message ?
• If 2 ADRs self auto detect at fault, should not we get SPD and ALT flags accordingly ?

Squawk_ident

The BEA will publish a new report next Friday 29th of July in the afternoon.

airtren

henra, grity, jd_ee,

Thanks for the additional comments on your previous posts.

I am looking forward for the next BEA report, and see how more it will contribute to the theoretical side of the accident understanding and interpretations.

Dutch M,

Interestingly, I am among those that went through the same reaction, from an initial, simplistic, trivial "pilots fault" to understanding better and better the complexity of a rare intersection and confluence of multiple causes, that have a much wider span, and involve so many more players. Consequently, I believe, the AF 447 is one of those cases - the allocated resources were a big help as well - which will contribute to improving multiple aspects of the safety of commercial air transport.

I think the spacial 3D/3axle character of the Kinetic Energy requires a consideration in its conversion to Potential Energy, regardless of it being linear or non-linear in terms of a mathematical function. However - if I understand correctly your sentence - I could not consider each of the 3 axle components "independent" of each other, by virtue of them all depending on the same spacial element, of which they are a component of.

I have struggled with the use of airspeeds, including TAS, for the Kinetic to Potential Energy conversion/conservation, and I came to the same conclusion that the speed relative to the ground is the one that is relevant. Two elements are relevant, IMO, in this very order: (i)the height is relative to the ground, and therefore, that's the reference system, and (ii) air can transition from adding, diminishing, or being a null factor in the A/C speed relative to the ground, and thus Kinetic Energy, which is conserved from one (air) transition to the next, and relative to the ground.

I would not go that far though, as to using the ground rotational speed.

Based on the info that we have so far - this may change, once we have the next BEA report, and more info about the state of awareness in the cockpit - the Stall Warning or the lack of it is, IMO, a very, very important contributor to the accident. It was the lack of a Stall Warning while in the middle of the "stall" and the presence of a Stall Warning, when the A/C was close to "exit" from the "stall"..

One or another, is ultimately less relevant as the fact, that in adverse weather condition, all fail the same way, reducing this part of the system's "redundancy" to zero. This is an industry wide element, not only Airbus. The redundancy built in may work for individual electrical or mechanical failure, but such events are arguably less frequent than adverse weather conditions, and thus a weak point in passenger A/C design industry wide.

Interesting....

I appreciate your post

rudderrudderrat

Hi airtren,

Simply use the air mass as your frame of reference. It may be moving horizontally over the earth's surface, but the conservation of KE + PE still holds.
IAS is just a measure of dynamic air pressure, it must be converted to TAS.

Hyperveloce

Thank you Takata for your patient answers. A last question: after the apogee at FL 380 of the quasi-ballistic trajectory, the AoA rapidly exceeded 30°, and the abnormal attitude law could have been triggered on this criteria (AoA>30°), but it has been said that it was inhibited since the airspeeds were invalid (below 60 kts) at that time (which is strange since IAS<60 kts is also an abnormal attitude criteria), and this also inhibited the stall warnings. But when the airspeeds became valid again, and when the stall warnings were allowed to sound again (after the ND inputs and thrust reduction), shouldn't the abnormal attitude protection law have triggered ? (since the AoA always remained above 35° according to the BEA)

Neptunus Rex

There have been many well thought-out and well explained hypotheses in this amazing thread. However, I still think that the basic problem was one that could have been solved by Power and Attitude.

Decades ago I flew an aircraft that had a beaut, coloured Standby Horizon, powered by a 28v DC battery, which was in turn kept charged by the aircraft's main electrical system. In the event of a Total Electrics Failure, the aforesaid 28v battery would provide power for a guaranteed 30 minutes. It was completely independent of any other power source, and would get you out of trouble when all else had failed.

Why can't we have such a simple and effective solution today?

KBPsen

To what problem?

Zorin_75

More effective than what?
There's no indication AI was ever lost...

wallybird7

JD-EE

wallybird7 said, "Apparently this crew didn't."

That is an assertion not in evidence. How do you know the storm showed on their radar? Was their radar working? Was it employed properly?

The weather forecast showed a line of thunderstorms about 100 miles wide over the equator. See AF447 Meteorological Analysis.

By the time the problem appeared on their radar any escape from the storm would have required extreme deviations from their flight plan with no communications to DAKAR.

They did note it at that time and made a deviation towards an area that appeared less risky than plowing on straight ahead.

Now, one might argue that they should have called Atlantico about this. But apparently this happens so often the pilots simply noted the fact and plowed onwards. I wonder what would have happened had they tried to check in at the follow-on control site after DAKAR since their flight plan was not properly forwarded.

Deviations happen all the time and you don't need clearance, just announce it on Guard Channel.

But the pesky detail stands - moving aside from the storm at the time they saw it would have required some serious course deviations. At the time they hit it the storm was a very wide solid band.

Agree. They should have deviated sooner. They knew the turbulence was coming.
Jcjeant
Hi,
Quote:
Was their radar working? Was it employed properly?

Again we return to the basic questions and answers ..
Radar working .. plane defect ?
Employed properly .. crew error ?
Again .. nothing between ...

Except a large build-up. And then all hell broke loose.

Bubbers44
The acars message said the pitot system failed causing AP and AT to disengage probably because of their recurring icing problem.
"Any speculation about weather other than icing taking the plane down needs to be proven."

Proven? How? Do you want a precise measurement of potential up and down drafts? What caused the ice build-ups? If not strong up and down drafts. Does turbulence exist in towering cumulous? Hell yes. Would it affect someone trying to hand-fly the plane?

So far there is no evidence of that being the problem since none of the other flights with normal deviations had a problem.

Just because the others skated through, is not "proof" that this one didn't get caught.

Those who insist it was turbulence and flying into a thunderstorm that caused the accident have absolutely no proof and are speculating. We know BEA knows exactly why they crashed by now. When they write the report we will know too. Be patient.

All of it is mere speculation. All the BEA has to come up with is "Probable" cause. Not "Exact" cause.

Dutch M

@cwatters
Yes, indeed, and it does look very strange.

Though, don't forget, in the main wing situation, the lift is destroyed because the airflow over the wing is not able to "carry" the weight of the airplane any longer and the boundary layer lets go.

In the HS situation, the weight is zero, because the direction of movement is already downwards.

And yes, in some situations the physics does look bizarre.

Dutch M

@sensor_validation
Yeah, suppose the windspeed goes from 100 knots back to zero, does this change the Ekin of the airplane ? If not, then you will need to take the groundspeed as speed reference.

The energy exchange Ekin vs Epot, is in general only valid for speeds in the direction of the change of Epot (ie Height) and not when trading speed between perpendicular axis.

henra

Dutch_M, you need to be aware that you have to determine the kinetic energy always with regard to the relvant reference system.
For an aircraft that is the air surrounding it.

To make it easier to understand let's take an example:

You have a wind speed of 200kts. Your aircraft is travelling at 250kts.
Minimum speed of your AC is 150kts.
How much speed can you trade for altitude now?

Correct ! You can trade 100kts.
You will be flying backwards then with regard to mother earth, but aerodynamically who cares ? You will still be flying.

If the relevant reference system changes its state beyond what the AC can bear, well then: bad luck. but you would have the same problem when you are flying at 100kts and suddenly a tailwind of 100kts hits you. Won't make a difference except for the horizontal component during impact with mother earth..

Dutch M

@henra
Hmmm, headwind, tailwind, airspeed, groundspeed ?

And yes, the speed bleed-off is limited by the aerodynamics to keep the airplane flying. Though speed bleed-off is not the same as loss in inertial Ekin.

Shadoko

Waouh!
If a/c weight was rero, then she didn't fall!
Weight can't be cancelled. Balanced, perhaps (when the a/c flies), but cancelled, not!
"Weight is the name given to the force on an object due to gravity." (Wiki). And excepted a gravity failure (), it can't be zeroed on Mother Earth

henra

Hmm, I don't want to sound rude, but did you really understand my example ?

And yes, the square of the speed before the bleed minus the square of the speed after the bleed is exactly the kinetic energy you can trade for altitude.
What is speed bleed if not redution of kinetic energy ???

Edit:
You really need to understand the concept of reference systems to get a grip on this.
Let me ask:
What do you think is the kinetic energy of the aircraft in my example after the speed loss of 100kts?
Please note: It is flying backwards now. Does that mean it has a negativ kinetic energy by now ?

Other question: Would the aircraft care if mother Earth instantly decided to change its sense of rotation by 180° from one second to the next?
You probably guessed it: It wouldn't give a sh't as long as the air around it keeps moving unchanged. The only force which the Earth itself applies to the aircraft is gravity and that is vertical.

Edit3:
Yes you can calculate the total kinetic energy of the AC with regard to the sun but that would be absolutely pointless. You can also calculate the kinetic energy with regard to the ground but for the question of how much altitude can I gain by giving up airspeed it is also irrelevant. It is only speed through the air which I can trade. When speed through the air is Zero there is excactly 0kts to trade. You can't get 'slower' than 0kts TAS/IAS/CAS. No matter what the surface below does. Or how the sun turns around this point.