gums,

Here in Europe on the morning after, looking at my previous post, I think something else needs to be said. For reasons we can easily understand, these AF447 threads have attracted a wide range of experts and/or enthusiasts whose combined contributions I doubt have been bettered on any other PPRuNe topic.

These discussions would have been very limited indeed if the only contributors had been airline pilots, Airbus or otherwise.

From the BEA, as quoted by HN39 above:
Les déformations des cadres montrent qu’ils se sont rompus dans un mouvement vers l’avant avec une légère composante en torsion vers la gauche.

HN39,
So, do you infer that the R/H side struck the water first?

Chris,

yes, my reasoning is that the V/S inertia tends to let it move forward without twisting. It is the fuselage violently veering to the right which 'twists' the frames.

infrequentflyer789,

This is not so straightforward. Some brazilian relatives already tried to sue Airbus in the USA, but the american judges refused that (link in portuguese). Besides, I think each jurisdiction is sovereign to accept or not accept the "official declaration" by BEA.

There is also a juridical thesis affirming that as most brazilians victims bought their tickets in Brazil, AF and AB must be sued under brazilian legislation. And here, if you can´t have a death certificate derived from the identification of a body, you must have a "presumed death certificate", that is a considerably longer and bureaucratic procedure.

PS: I´m not a victims´ relative.

auv-ee, the spreading or square law loss is about 20 log10( 1700 ) if we use 1700 meters as the ultimate range. That's only 65dB (pulling it off a calculator rather than my semi-memorized log tables.) Add in a generous 10dB for the extra attenuation of H2O at that frequency - as somebody else cited, and you get slightly less than 75dB. So gives about 86 dB above 1 micro Pascal. If the noise level is only 36dB give or take a few dB we still have about 50 dB more attenuation to cover. We are working one way rather than radar range calculations that raise exponents.

That extra 50dB comes from ???? Antenna loss and other properties are figured in already on the sensitivity and sound pressure at 1 meter figures.
That hints the range at noise floor is about 300 times 1700 meters.

Ah, I had not allowed for bandwidths. I presume the figures you gave are in the traditional 1Hz bandwidth. If we use 100Hz FFT that's 20dB of the 50 dB right away. If we use 100kHz bandwidth and simply look for an amplitude change that could account for the full 50 dB and why Thales may have figured post processing with say a 1kHz set of FFT windows should bring it right out.

(That was a stupid omission in my original analysis. Learning the actual measurement method would probably lead to better answers, too. I bet that would take a REAL lot of digging.)

For the onlookers:

It's called square law or spreading loss because the signal has to cover more area on the surface of a sphere as the signal expands out from the source. The area of the surface of a sphere is an r^2 or range squared function. So the power drops with the range squared.

Noise is usually figured in decibels, 10 log10( power ratio), and are a logarithmic ratio with no units. A very handy measurement when dealing with signals in noise is the amount of noise at the frequency you are operating in a known bandwidth, usually 1Hz. Since the noise is usually incoherent noise doubling the bandwidth doubles the power.

So we end up with a "20 log10( distance ratio) + 10 log10( power ratio) + incidental numbers" sort of calculation. I hope that filled in gaps for most people.

bearfoil, I have long contemplated an upset or intentional rapid dumping of altitude with the crew in control or back in control before the splash. They may have been trying to goose the engines hard enough to get them back flying after the altitude loss and simply ran out of sky. I'm not sure there is near enough data to fully support that scenario. I am not sure there is enough data to rule it out. That's why I've not harped on it.

HN39,

Just to clarify: you have the aircraft yawing to the right on impact, so the rear fuselage and VS swing left? When the APU detaches, it might be thrown to the forward-left even more than the fin?

We know about the THS screw-jack, but I wonder what happened to the THS itself. Or should we treat the L/H and R/H elements separately?

Centrosphere, under what theory would an accident that happened on a French plane, on a flight from Brazil to France, that happened over international waters in the Atlantic ocean fall under the jurisdiction of a US court? We're not THAT arrogant that we think we should have world wide court jurisdiction.

Chris;

All I wanted to say is that, if I have to choose between left wing low and right wing low, I vote right. At or after the impact of the rear fuselage, that's where the flight ends for me.

No question, these guys are very competent designers, but the more complex the design , the more chance something unexpected and/or foreseen will eventually present, sooner or later.
The flight envelope protection systems are reliable as long as the numerous sensors send the accurate and real information and also that this information is processed as designed by the different computers ...

Not at all.
Still trying to figure out why the BEA did omit the tracks of IB6024 and LH507 ?!
They have crossed the full red too, but as HN39 wrote much earlier : always keep in mind that the big systems seen by satellites don't necessarily show up like that on an aircraft's weather radar.

Salute!

Nuts is onto the original reason I joined the fray here two years ago.

Having flown the first "operational" full FBW system, I was a non-volunteer test pilot, as were all of us in those days ( 1979 and a few years thereafter). We only had a few hundred flights by then, and most were by Edwards "golden arms" and highly experienced fighter pilots. When we increased the sortie rate by an order of magnitude, we discovered flight conditions unforeseen by the engineers and the "golden arms". So we were flying several hundred flights a month versus the several hundred flown from 1974 to 1979 during F-16 development and testing.

We clever pilots can find ways to "beat the system". We can do things that the engineers and others never envision ( see Perpignan, for example, or the first crash with a high-time pilot making a low pass for public relations). Then there are actual flight conditions that the engineers have not planned for with all their control laws, limiters, reversion sequences.

Let's face it. The Viper has an operational envelope that waters your eyes compared to the 'bus. We had and have different priorities on our flight control logic, and gee was the easiest to implement. It was and still is the aero that causes problems. Our great engineers never envisioned us zooming up at extreme pitch attitudes, then trying to roll at max rate below 150 knots or so. NOBODY DID THAT!!! Simply because they couldn't until then. So now we have a jet that feels good, handles better than anything flying and we get spoiled. We "go where no man has gone before", heh heh. Hence, we discovered that exceeding the flight control laws wasn't all that hard. Especially with respect to the AoA protection. Then we discover that at 50 or 60 degrees AoA that we run outta nose down pitch authority. Well, hell Kemo Sabe, what are you doing at 50 deg AoA? The limiter was supposed to keep you from exceeding 25 degrees. So see the Code One article and read what we discovered and how to get outta a bad situation.

So my personal observation is that this accident will be found to be in the category of "unplanned flight conditions", possibly complicated by one or two sensor failures.

I also see a few modifications coming for the 'bus control laws. It's digital, right? So not a lotta hardware needed, just some good flight tests with modified control laws/reversion sequences.

JD-EE, seem to me your numbers about transmission losses are about right. However, since the source frequency is 37.5 ± 1 kHz, I think we can safely assume that the bandwidth of the TPL reciever is at least 2 kHz. Counting only sea state noise (7 to 10 kt, no rain) we have about 34 dB re 1 uPa / 1Hz wich gives a 67 dB noise level. Using your numbers for transmission losses this leaves 160 - 75 - 67 = 18 dB available for detection @ 1700 m, a value considered minimal for simple detection (learned from auv-ee).

By the way, I am wondering if the towed array the french navy submarine dragged was really a usefull asset. Theese things may not be efficient at all at 37.5 kHz even using DSP.

JD-EE,

Yes, it sounds like poor juridical reasoning to me also, but it was attempted. The "justification", it seems, was the fact that the plane had american components. :ugh: You must be aware that there is an indemnization industry, and in cases like that, lawyers try to seduce people to sue in america due to the widespread belief in Brazil that US courts are more though.

In any case I was just trying to say to infrequentflyer that despite his argument about the "wide international presence" of AB and AF, I think that from the point of view of the brazilian victims´relatives the "forum shopping" should be restricted to brazilian and french courts.

CONFiture said:
As a curious SLF, I wondered if satellite images of weather systems might be useful to pilots, as a supplement to what they can get from their own weather radars? Would it be prohibitive in terms of bandwith to download a localised image every couple of minutes? Or do the weather satellites track in a way that wouldn't be useful?

As a passenger, it would alarm me a little to know that the pilots were trying to pick their way through a maze with only an educated guess as to the layout.

Hi,

But exactly the same thing can be said about the human way of processing informations. Our brain is far more "complex" than computers at analysing those informations transmitted by our senses, and our senses can be abused exactly the same way by any false/distorded information.

Moreover, as far as flying an aircraft is concerned, those basic informations can not be acquired by our senses alone without relying on instrumentation (which may display good or wrong data in particular cases). Consequently, ergonomy (human-machine interface) and crew training are the most important factors as for retrieving any compromised situation where everyone (human and machine) can end confused by unexpected environmental factors.

The only false idea is if one will claim that we could make flying an aircraft "100% safe" in every possible situations. Automatisms would make them "safer" in most situations... but not extreme ones.

overthewing

Chris Scott explained it quite well. The time to avoid weather is well before one enters. Large commercial a/c are built (designed) to cruise, not to manouver. As gums has said, his a/c has a different mission, and it is not his personal comfort or peace of mind.

Radar has been discussed already, and the volume of opinion affirms the perception that much is left to guesswork. Any technology that is admittedly improving over time is an admission that the current kit is insufficient.

The auto pilot disconnects when it cannot keep up with the a/c. Turbulence and airstream impacts cause the slow to react airframe to lose "response", ie, it doesn't have sufficient time to complete an aspect change before the environment comes up with a new and different challenge.

I would board an A330 from Rio tomorrow. There is no increase of worry. What happened to AF447 will become known, and there will likely be no "new" gremlins to fear, only old ones to re-assess. My fear has to do with gum's eloquent statement. It is likely the FlightCrew will be burdened with the lion's share of responsibility. My hope is that in this new world of intercomm, those who have traditionally owned the forum will be fearful of appearing less than forthcoming, or even sly.

Where do you sit?? Since I left the cockpit, I sit Port abeam the engines.

happy skies,
bear

But takata, you speak of the solution in your post, one I think may never change. A computer can calculate, extremely accurately, and super fast. It cannot, as yet, display judgment, a "balance" of inputs, an abstract weighting of data, and a trained reaction to an uncommon situation.

For auto flight, abstract thought is a negative, it consumes energy and creates ennui. In the corners, where dwell the demons, the box is out of its domain. Here comes the seasoned pilot(s) to assess, entrain, and command. Your word, interface, plus an exhaustively trained segregation of appropriate domain, has been, and will remain the solution, No?? Further, I would not mind flying behind two sleeping pilots, with a tested system that allocated rem sleep to each, and had a sense of what may be ahead, sufficiently to collect a safe "get" and alertness. It is flight envelope that commands the choice of PIC, not simply the passage of time airborne. With this accident, I have the insistent feeling there was "surprise". Surprise is bull goose demon, imo.

Tracks & Pitots
 

CONF iture said:

Tracks: My understanding is that LH507 was on the exact same track (UN866) as AF447 except they were at least 30 minutes ahead (20 minutes difference at TO from Rio). I don't know what track IB6024 was on. However, in some manner LH507 recognized a weather situation ahead and altered their track ~12 miles to the West. By the time AF447 got to the weather, the storm cells congealed into one with the worst part being towards the Eastern end. Originally, it was four separate cells. I am wondering if LH507 approached in time and picked their way through before the storm congealed? Also, by altering their course Westward, did they passed through a more mundane area? On the other hand, AF447 approached a congealed storm and turned Westward only 3 miles off track, timing of turn unknown but perhaps late?

Pitot tubes: I read somewhere about other A330/A340 problems relating to speed errors, i.e., pitot tube abnormalities. What I remember (not from the BEA reports) was that one crew thought the pitots might be icing, and at some point through the episode, switched the pitot tube heating setting from "automatic" to "on". Then everything settled back down and the flight proceeded normally. What exactly is the difference between the automatic setting and the setting regarding pitot tube heating?

Hi,

The “testability issue” in complex designs is a big, complex and crescent challenge.

"Accurate and real information" : Again a testability issue

"processed as designed" : The loss of IR1,2 and 3. Could a system like this one be designed to afford faults of this type? Or was a "black swan" like event, for EADS evolution?

But our brain can “invent a new algorithm” and immediately apply it when required. And succeed, despite CRM issues during "extreme" situations.

"but not extreme ones": Mostly if your design is highly optimized. And at extremes can present an unexpected "toll" for the operator. Just to remember us optimization is not "free".

Hi,

RR_NDB, if I were you, I would refrain from the use of bold/colors in my postings as it doesn't make them either more sensical and/or authoritative this way. Where the hell did you see "the loss of IR1, 2 and 3" in AF447 case?

In auto mode, the amount of heat provided by the heaters is modulated following what the "probes" themselves are sensing. When anti-ice is selected ON, full heating is provided, whatever the "probes" are sensing. It makes sense if you are considering that the "probes" are freezing because the heaters were not delivering the correct amount of heat at the first place.

In fact, it seems that those probes freezing at cruise are not related to temperature (really) changing but to those specific (very small) ice particles melting when such conditions are encountered (mostly in tropical weather). Hence, TAT will increase very fast and reach a level close to 0°C (iced particles temp melted on the TAT probes). The drawback is that you can not fly with anti-ice ON all the time as it can also damage all the systems by overheating the probes. Hence, it should be selected on purpose.

Not a "graceful degradation" after 02:13:08
 

takata,

As i understood after 2:13:08 ACARS show the a/c "resources" further degraded and the crew no longer "could use" ISIS and IR´s. It is not true?

post #1343 was edited as suggested by you.

HN39;
I had refrained from making a comment, following your much earlier post where you considered the bank was to starboard rather than my posited port. The reason for my delay centers around the term "yaw" and its interpretation when related to the BEA's use of it in the end of flight events.

My interpretation was that the term "yaw" was being used to describe the aircraft rotating clockwise in a near horizontal plane about a fulcrum nominally near its CoG while airborne - (spin?).

Your interpretation (I believe), is that the "yaw" was introduced by the #2 engine digging in and creating the "tail yawing to port" event which resulted in the damage described and allowed the safe departure of the Vertical Stabilizer as the empennage dug deep into the water - probably collapsing and shearing off at the aft pressure bulkhead. The high CoG of the V/S and its own inertia then completed its final disengagement, allowing it to flop into the water on its port side. The APU, having being punched from its mounts gave a glancing blow to the rudder (as it swung hard to port following the loss of the hydraulics), then commenced its journey to the bottom.

I can go along with the above, but when introducing the "en ligne de vol" business plus the high RoD, the time between #2, the tail and #1 digging in, was in the order of milliseconds. Not enough time to overcome the moment of inertia already committed to the "en ligne de vol". As an after thought, and to just muddy the waters some more; - if the horizontal component of the aircraft's trajectory was say 30° to port of the "heading" at time of impact, the same damage would most likely occur.

It is rather academic at this time, but the actual rationale used by the BEA in making their interim conclusions would be interesting to know.

gums, Quote:
"Having flown the first "operational" full FBW system, I was a non-volunteer test pilot, as were all of us in those days ( 1979 and a few years thereafter)."
The first year of ops on the A320 (1988) was a bit like that, in a low-key way.

Quote:
"We clever pilots can find ways to "beat the system". We can do things that the engineers and others never envision ( see Perpignan, for example, or the first crash with a high-time pilot making a low pass for public relations)."
Yes, flew with one or two guys who aspired to be test pilots. (Why don't we switch off an ELAC and one/two SECs, and get some useful practice in Direct Law? Not today, thanks.) We managed to avoid a Habsheim.
There was a subtle "trap", though, involving the A/THR and FD. In descent in OPDES, the A/THR is in idle mode, and the selected IAS is controlled by elevator (i.e., conventional). If you come into the circuit and elect to go visual, you may elect to dispense with the AP & FD, but retain A/THR. If you level off a bit at (say) 3000ft when the FMGC thinks you still want descent in idle thrust to (say) 2000ft, the speed will naturally fall below target. In those days, the first intervention from the A/THR would be Alpha-Floor (TOGA thrust) as the stall protections kicked-in. Good way to mess up your visual approach... We soon learned to switch both FDs off: to tell the A/THR we wanted it to control the speed for us (and avoid conflicting FD pitch-commands). That had not been originally established as an SOP.
Word did not filter through to one Asian operator, however, and it lost an aeroplane on the approach at Bangalore. The crew had wound the ALT selector down to zero, I think, retaining OPDES, so the thrust needed at about 500ft never materialised. (Bit like the B777 at LHR; reason totally different.)
Post-Bangalore, one of gums's software changes ensured that the A/THR automatically comes out of idle mode if the speed falls below Vls.

Airbus FBW architecture is now a mature system, with tens of millions of flight hours behind it, so simple surprises like that are highly improbable in the case of AF447. But airline pilots do not generally explore the boundaries of the flight envelope, so the learning process is not as brutally quick as on the F-16.

Quote:
"So my personal observation is that this accident will be found to be in the category of "unplanned flight conditions", possibly complicated by one or two sensor failures.
I also see a few modifications coming for the 'bus control laws. It's digital, right? So not a lotta hardware needed, just some good flight tests with modified control laws/reversion sequences."

gums, you could be proved right.

Auto throttle authority
 

Salute!

Well, Chris, I pray that I am close to the scenario, and that we let the crew, et al rest in peace after their efforts to get the plane under control. We shall see.

The Hornet has auto-throttle, but it is not tied as closely to the overall control laws and autopilot modes. 'bird can explain better, but the Navy troops liked an approach that used AoA to control speed and throttle to control descent rate. We airdales normally pointed at the end of the runway and used throttle a lot more than AoA for speed. I used more of the "squid" approach procedure after getting bit in the butt one night in the SLUF, and flew at best AoA, using throttle for whatever it took. In short, I didn't worry about a grease job.

Something bugs me when I can't "push it up" with those levers and command more thrust.

I only flew one jet with a good autopilot approach mode, and it did not have an auto-throttle. It had good AoA/pitch rate protection and followed the ILS like a dream. Would watch the stick move back and forth as "we" came down the glide path ( F-101B, so it was a family jet. Heh heh). Runway environment in sight? Voila! Hit paddle switch and land the sucker.

Make no mistake. I do not want to see complete control of the control surfaces in a FBW jet. The things are designed with different aero considerations than "conventional" designs.

So I await the data plots, as most do.

Mac,
Well, thank you for taking my remark into account.
My answer to your question will be no, as per the BEA "interim conclusion" from their ACARS study:

F-GZCP - 1st June 2009, BEA report #2 p.41

1.16.2.4.5 Partial conclusion on the analysis of the messages:
At this stage of the investigation, analysis of the messages makes it possible to highlight an inconsistency in the speeds measured just after 2 h 10 which in that minute generated ten of the twenty-four maintenance messages. Eleven other messages generated between 2 h 10 and 2 h 14 can also be linked to anemometric problems (inconsistencies in the speeds, low speeds and/or erratic speed values).

* The aircraft switched to alternate 2 law in the minute at 2 h 10 and remained in that law until the end of the flight..

* No message present in the CFR indicates the loss of displays or of inertial information (attitudes).

Note: in addition, as the ATSB mentions in its second interim report(3) on the incident to the A330-300 that was performing flight QF72, in relation to problems with ADIRU’s, the maintenance messages relating to the events on flight AF447 and fl ight QF72 show significant differences, both in their sequence and in their content.

takata

Thanks for your response regarding the pitot tube heating question.:ok:

HazelNuts39
( From the 1st interim report)
One of the aspects of your argument that bug me is the association of a *slight torsion component to the left* with a violent *veering to the right*

The second interim report explains the stresses involved thus :
"The vertical stabiliser’s side panels did not show signs of compression damage.
The breaks seen at the level of the lateral load pick-up rods were the result of the backwards movement of the attachments and centre and aft frames. The observations made on the vertical stabiliser are not consistent with a failure due to lateral loads in flight.
The observations made on the debris (toilet doors, partitions, galleys, cabin
crew rest module, spoiler, aileron, vertical stabiliser) evidenced high rates of
compression resulting from a high rate of descent at the time of impact with
the water.
This high rate of compression can be seen all over the aircraft and symmetrically on the right- and left-hand sides.
High levels of loading would be required to cause the damage observed forward of the vertical stabiliser (compression failure of the forward attachment).
These observations are not compatible with a separation of the aft part of the fuselage in flight.

The damage found at the root of the vertical stabiliser was more or less
symmetrical, as were the deformations due to the high rate of compression
observed on the various parts of the aircraft. This left-right symmetry means
that the aircraft had low bank and little sideslip on impact.(which shoots down the sideslip theory, too )
The deformations of the fuselage frames at the root of the vertical stabiliser
were not consistent with an aircraft nose-down attitude at the moment of
impact".

All the above makes me think that the slight torsion to the left component of the stress forces on the frame came from a yawing moment to the left, therefore a slight left wing low attitude at impact.

I'm sure I will be corrected if wrong, but I believe the issue with pitot tube heating is only when on the ground - no problem dissipating 300+ W when exposed to cold flight-speed air, but they'd glow red hot if left on on the ground! So the auto control will be very simple - as all safety critical systems should - to be easily testable, and surely a cut-off temperature would be near +40 degC than near ice-point?

I am not a big fan of the super-cooled icing theory, I suspect the current issue still subject to research is due to the way certain distributions of micro-fine ice particles (i.e. what makes up different clouds) pack acting as an insulator so there is poor heat transfer from the heated metal to the ice blockage. If it is the type of cloud - then I don't like the odds when identical probes pointing into the same one, that any 2 out 3 may be adversely affected in exactly the same way. If I was responsible for the pitot-tube detail design I would pay most attention to the drain hole and make sure that is always kept clear - meaning the most likely failure mode would be for value to fall to zero - easily detectable. Early Thales pitot tubes had poorly manufactured drain holes, burrs left which encouraged solid deposits and blocking, but sure this not now an issue.

As discussed many times drain hole blocking on its own would cause a small over-read, both ram and drain blocked could lock an old speed value in, but may be difficult to detect because speed reading still live - varies with static pressure reading/altitude. Worst time for this to happen would be during a commanded climb or speed change.

The pitots may only all disagree only when they melt out differently, so what was happening just before 02:10?

Resources degradation after 2:10:10
 

Takata,

Looking to my bookmarks i found:

http://www.iag-inc.com/premium/acars2.pdf

I read both BEA´s I and II.

I was always considering a very serious degradation as a fact.

Another crucial point we must wait for FDR contents.


As i understand now the analysis of the link above is at least, "baseless" or even worse.

mm43;

In my mental 'model' the right wingtip digs in at about the same time as engine #1. Due to the difference in moment arm, the yawing moment imparted by the wing tip may well be greater than that of engine #1.

lemurian;
From page 27 of BEA's #2:

"In auto mode, the amount of heat provided by the heaters is modulated following what the "probes" themselves are sensing. When anti-ice is selected ON, full heating is provided, whatever the "probes" are sensing. It makes sense if you are considering that the "probes" are freezing because the heaters were not delivering the correct amount of heat at the first place."
That is not how I read 1.30.50 p1/2.There are two heating modes with Airbus,low heat on the ground and high heat when airborne for the pitots.There have been numerous incidents where this changeover has not occurred giving the crew lots of problems.I have also seen where the pitots have cooked in the sun of the Indian Ocean to a threshold above the warning causing nuisance ecam.

Hi,

I wonder whether it is thanks to these automatisms that the aircraft most often is near extreme situations
If the pilot do not have the FBW and an autopilot ... I wonder if by themselves they would go at altitudes and speed close to the coffin corner (extreme situation) to make their cruise if they have to handle their plane manually

There isn't an auto mode on the ground [edit, until one engine is running], only manual mode [for test if one engine is not running]. Auto mode [is always set] once the aircraft is airborne. Probe heating is then monitored and computed, by those three independant PHC (Probe Heat Computer). What do you think that will feed the PHCs with curent air data beside those probes themselves?
Nonetheless , if any probe icing is suspected during the flight => in auto anti-ice mode, you may ask for more heat (than computed) by pressing the anti-ice buton.
You'll need to refer to the "icing" part on the manual as I'm answering from memory without a single look at it.

Advanced Systems
 

Hi,

The reason to use all this new solutions (FBW, complex control laws, etc.) is to "optmize" the performance (less weight, more resources, more profit margins, etc.) and last but not least, to have a safer machine ("protected", with good human-machine interface, etc.).

Naturally these "Advanced Systems" would operate in "regions" not usable by "conventional designs

When for any reason you have a problem i understand the "Advanced System" (the crew and the "super bird") will be closer to the limits (the mentioned extremes).

The reason for the recovery of the China 747 upset probably is related to the "lack" of optimization (in several aspects) of the a/c.

The toll always must be paid. And after paying it we "upgrade" the original solutions. (sometimes just by a new "software release"). EADS is paying the toll ahead of the competitors IMO simply because introduced "Advanced Systems" earlier, for the airlines. An "inexorable" trend.

Erroneous air data
 

Salute!

PLZ look at the B-2 crash at Guam

No icing.

Tubes with moisture and actual water - yep!

Loss of control at WoW? Yep.

I would not trust a sensor that has its own logic to determine if it is unreliable. Anybody else here think that way?

Granted, we can have only so many sensors to check on the other sensors. So maybe we should look at sensors that can stand zillions of degrees of temperature, but still measure vital dynamic and static pressure within some zone of accuracy. We don't need +/- 1 degree of temperature, +/- 100 feet of altitude, or even +/- 5 knots of speed.

There are major aero considerations determining favorable flight characteristics than a few degrees here, a few knots there, a few feet of altitude there. GASP!!

P.S. Getting too chatty here, so I shall chill for a bit.

Redundancy always benefit
 

Hi,

When possible i aways use a redundant "info source! (with a different working principle) for my decision making. With 3 (odd)* much better.

* Allowing a voting scheme

HzelNuts39
Yes !
Just imagine a loop with an axis that goes top to bottom and someone turns the loop around that axis. The only movement that will cause a deformation as described above is a counter-clockwise rotation, i.e. a yaw motion to the left, and that's what I've been seeing for the past 17 months.

mm43

...I see your point, a "Yaw" is a rotation, "nose right" is merely a crab. Whichever engine "digs in", the a/c has little time to accelerate around its "anchor" horizontally, the vertical is too fast. If the impact was mostly vertical, (BEA), the fuselage may have ruptured in classic form, fore the wing and aft, perhaps the tail separating at the Aft Bulkhead, the cockpit at the forward door. (The cockpit was close to, but separated from, the forward door, number one on the sea bed).

The VS hoops were deformed in a manner suggestive of a vertical exit with a slight twist to port (BEA), and relative to the fuselage.

I suggest it is not indicated that the tail hit first, number one, the Deck angle for tail strike is 17 degrees, and then only the belly portion at the break, up toward tail cone.

For the Empennage to hit first requires a deck angle of more than 17 degrees, and when adding that to the airflow, we approach rather closely to an AoA in excess of 90 degrees. Not supportable, unless in the rather wide parameterds of the Bear.

mm43..........
"....resulted in the damage described and allowed the safe departure of the Vertical Stabilizer as the empennage dug deep into the water - ...."

Hazelnuts39....

"In my mental 'model' the right wingtip digs in at about the same time as engine #1. Due to the difference in moment arm, the yawing moment imparted by the wing tip may well be greater than that of engine #1."

Hmmm..... How can right wing tip and #1 both be in the water and #2 DRY???

Redundant air speed sensor/measurement principle (Laser based)
 

Hi,

Link

Is this sensor operational today?

It would seem likely that they are at a resonant frequency for one of the constituent bonds, likely N-N or O-O bond (N2 or O2) and thus able to get an absorbtion and re-radiation of the emitted energy. ie. a return that does not require dust, water droplets, or any other reflective constituent in the atmosphere. Pitot tubes-move over. Now we will just have to figure out how to keep the bugs off the "window".