Open447
 

I'm quite dubious about crowdsourcing in the pure sense, because the problem is too much like screening bags - people aren't very good at detecting significant rare events in a large number of insignificant ones. Further, as a lot of the seabed is going to be quite different oceanographically, most of the variation in it will be rocks and the reviewers will lock on to the rocks because they're what's available (anchoring; target fixation).


But there might be some role for it as part of a semiautomatic process - for example, if some kind of statistical model has thrown up x number of probables, there could be value in having the crowd work through them, as the targets probably aren't very amenable to automatic detection. If we were looking for the fin, for example, that would have some nicely defined corners, but we're looking for "stuff that looks engineered, but has been smashed" and that's quite subjective.

There are some interesting methodologies for this sort of thing; one would be pairwise comparison (a.k.a kittenwar). Rather than "is there an aeroplane here?" or worse "here are 100 very similar sonar images, can you spot a piece of wreckage?", this presents the user with 2 randomly selected probables and asks them to pick one - eventually, you should end up with the images sorted by the totality of the users' preferences, which should be a valid Bayesian search. There's a more formal version called the Analytical Hierarchy Process, where you make the pairwise comparison on the basis of parameters you choose in advance.

As well as kittenwar and Am I Hot Or Not, this has been used for quite a few hard problems - like examining British politicians' expenses claims, and making technology decisions in big companies.

Alternatively, if you were trying to build a statistical method of identifying targets on the seabed, you might use something similar to classify the seabed into different topographies, or to confirm that a zone was clear of wreckage so that you could use it to calibrate the model.

Depending how self-similar the seabed topography is at the relevant scale, it might be possible to use a Fourier analysis to compare similar areas of seabed - the answer to my assumption looks to be "not very", but it might be possible to classify it into relatively self-similar zones.

HN39:
In fact, this is not knew to us. We all know that a smaller cell, may hide a bigger one. Sometimes, this smaller cell, may appear to the crew, as not threatening the path we are flying. However, when the radar gets a first cell, and if it appears to be "blocking" the "view", the radar will display a continuous solid band at the further end of that same display, as wider as the shadowed angle, to alert pilots for that possibility.

GPS does not track accelerations. It is a tool for calculating positions. Differentiating position with respect to time gives velocity to relatively poor resolution. Differentiating velocity with respect to time gives acceleration "sort of". The intertial units provide the acceleration. Neither directly gives velocity. Both GPS and the intertial units are combined with other data sources in Kalman filters to give reasonably good estimates of position, velocity, and acceleration.

None of them know squat about the surrounding air mass.

{^_^}

Alternate airspeed measurment
 

It seems that an alternative air speed measurement is needed to augment the pitot tubes, something that would be affected differently by environmental effects and other failure modes. I'm not suggesting replacing pitot tubes, because that would just introduce a different, but still single, failure mode, rather than introducing redundancy. What comes to mind is Doppler measurement of back-scattered energy, either EM or acoustic. A quick search reveals that an optical version of this is already being developed in the UK (though they seem to want to replace pitot tubes):

Emerald: Article Request - New optical airspeed sensor poised to cut airline costs

Likely other groups are working on this also.

Not a lot of use when it is IAS you need.

Alternate airspeed measurment
 

If you are responding to the use of Doppler measurement for air speed, that is an excellent point. It would be necessary to measure air density to go along with the velocity measurement. I don't know how the UK team plans to do that, though it could be derived from temperature, static pressure and humidity (any other significant factors?).

Redundancy is a siren on the rocks when one is up against common fault. BA038 had redundancy, but at some stage a system must be parallel, hence the dual rollback. The closer the rubber gets to the road, a system folds into unity, up only against the odds.

Unreliable airspeed became common on this type, hence the acronym, and the training focus. Because three separate pitot static systems generate discrepant airspeeds does NOT necessarily mean they have all iced, together or in some aberrant sequence.

Sailing in the doldrums one experiences no "wind". The mass is expanding around you and rising. Slowly at first, then as this warmth gains altitude, it increases in velocity.

Had 447 entered the mother of all cells? Most likely not. An average one will do nicely relative to upset and airspeeds that rocket up and down. Was any of the Alert/warning/alarm prompts singled out and addressed/cured? Shall we use the RTLU as an impromptu altimeter, by its demonstrated limit after falling out of the sky? The fuselage of the 330 is massive, and the pitots are well away from each other. This attacks the theory of Ice/turbulence, and entertains the discrepant/local theory. 1/2, 1/3, 2/3? Look at the numbering of the Tubes and the ACARS.

Again the autopsies are mentioned. The Captain's remains do not suggest a position in the a/c. Neither do the other peoples' remains who are of necessity assumed to be unseated, mobile, and not just at impact. Specifics of trauma are limited to the determination by BEA that these were seated. Belted? An easy conclusion given the facts? Evidently not. I say again the trauma focussed on by BEA is patent in trauma exhibited by human beings in CAT or upset historically; in this case the posture of each victim is concluded to be known. Mistake?

HN39,
Perhaps more a function on how the radar was being used and less on whether cells were being hidden. From the first BEA interim report,

Similar narrative detail is not provided for the actions of the pilots on the Iberia and Lufthansa flights, who also deviated.

bearfoil, there were 50 bodies identified through autopsy. The second interim BEA report says this:
Whether from deliberate or imprecise phrasing, the above language read literally suggests the 43 victims so described were passengers, with the results of the five crew autopsies omitted.

JD-EE,

That might need a little clarification. http://images.ibsrv.net/ibsrv/res/sr...s/confused.gif

While gps is primarily a system to calculate position, it can also be used to provide fairly accurate heading and ground speed data, in conjunction with appropriate software.

For example, if gps position is sampled at a constant, known rate, it only needs a bit of trig to calculate heading and for ground speed, a bit of arithmetic using sample rate (time) and change in position + scale accordingly. Not exactly rocket science.

Of course, ground speed != air speed, but in a typical flight, with small changes in wind force and direction, there would be a measurable relationship between the two, which could be used as an added data input to the various system filters. It may be "poor quality data", but still usable within it's limitations...

Regards,

Chris

air speed check
 

Just an idea, or two...:

Could variations of the air flow, measured at the engine's intake at a given rpm, give a clue about pitots' malfunction ?

Would air speed measurments at the engine intake, compared against the tremendous engine's thrust, be reliable ?

Sorry, I'm not an engineer... :{

Already exists - BUSS. Not fitted on AF airbuses. There seem to be some widely varying opinions of how well it works. AF rationale for not fitting it is here:

Air France - Corporate : The BUSS or "Backup Speed Scale"

I believe BUSS is standard on A380, where it was optional on earlier models.

Preface: I have 250H+ TT and study for my ATPL exams at the moment.

syseng68,

I can tell you from my limited experience that it would not be very useful. The relationship between TAS and GPS GS would be the wind, and then between IAS and TAS temperature, ambient pressure, altitude and humidity.

The only way to know the wind vector is to compare GPS vector with airspeed and heading information. If you have lost airspeed, you have lost all information about winds.

Winds do change, especially around convective activity. If the margin between stall and overspeed is small, GPS groundspeed is just about useless.

In my opinion, using optics or engine pressure readings sounds more promising as an ASI backup, because it tries to *measure* airspeed rather than deduce it.

One for the conspiracy theorists:-

When the 1st BEA interim report was issued on 2nd July 2009 the English language version was only 72 pages long, it didn't have all the appendices in the French version. The version with the same filename f-cp090601e1.en.pdf (created 28th July 2009) now on the BEA website is complete and is 128 pages long, but doesn't include the exact final position ACARS message, which is in the earlier version

This is the same location described elsewhere, but was it removed because

a) They missed the fact that this position was slightly off-track (see takata post earlier re eurocockpit analysis)

or

b) The position is more likely to be @2:10:30 (higher priority messages inserted into sequence), which puts it some 20 seconds or so after the cascade of errors started, not just before. I'm pretty sure mm43 posted before about positions quoted at half-minutes, but maybe that was based on Brazilian Air Force extrapolation data - they also had a position at 02:14z.

or

c) It just wasn't supposed to be there in the first place (wasn't in the first TV leak),

Can't say its very important, but I was sure I'd seen the #02:10 position report, but no obvious revision marks to the document...

For all the AF447 positions from 00:10 in ACARS 2 dp precision use in

Flight Paths of Flight AF 447 and of the flights that crossed the zone around the same time

see

http://www.bea.aero/en/enquetes/flig...data/AF447.txt

Alternate airspeed measurment
 

The description of BUSS does not make it sound very appealing. I was thinking of something that would be a precise speed measurement, as valid as the pitots, a few of which would provide more inputs to the voting logic and the Kalman filter.

The idea is to add a speed sensor based on different physics that would not be subject to the same failure modes as pitots. I agree about "parallel" redundancy, like multiple pitots, where a common fault is possible, or the case of "series" redundancy where the pre-existing failure of a backup is not evident until the primary fails (double pressure seals come to mind).

Agreed that the cage or depressor weight (2-body launch and recovery) is the usual configuration for a deep ROV. However, it is not so that the ROV has to return to the cage to move the ship. When the ship moves, additional scope must be payed out from the ship to keep the depressor at the right altitude, and the ROV can tow its neutral tether as the depressor moves. When the ship stops, the additional scope is retrieved as the depressor settles under the ship. With a rough bottom, it is necessary to ensure that the neutral tether is not dragging on the bottom, lest it fetch up on something. I don't know if this is attempted with more than one ROV/ship; that would surely be more tricky. Agreed though, for reasons already discussed, that ROVs are not the right tool for a wide area survey.

Alternative Air speed sensor
Hot-wire anemometer, hot film anemometer? Would need a filtered air feed (which might ice uip, unless it was designed like a Dyson bagless vacuum), but they last for ages in windtunnels and engine Air Flow Meters
With temp can give dyamic head fairly well I believe (Ptot)

Hello!

Maybe I am missing something, but since airspeed is essentialy neded for assesment of the lift produced by the wings, would'nt be more straightforward to measure/calculate the lift? It should be possible at least by measurement of the stresses in the wing structure. Or by measurement of the pressure on a section of the wing and by integrating the pressure on that closed curve.
Had anybody heard of such an approach?

engine P1
 

Not a bad idea at all. Very likely each engine has its own probes for measuring intake total pressure P1 and intake total temperature T1, which are used by the engine electronic control system (FADEC). The difference between Pitot pressure and P1 is engine intake total pressure loss, which is quite small in cruise. I don't know if the engine's P1 probes have ever experienced similar icing problems as the airplane's pitots.

HN39

With processing accelerometers provide you with distance covered despite their primary data being acceleration. Similarly you can differentiate GPS location (and time) information to get velocity and a second differentiation gives acceleration.

Note that with GPS you are differencing two quantities that have significant error dimensions relative to the difference obtained. So the error band on velocity is large. The error band on acceleration is even larger.

I have a pair of GPS receivers a few feet to my right. They are for precision time keeping rather than navigation. But I note the wandering of their time signals relative to each other with stationary antennas. "A few feet" is the translation I get on errors at about 1ns per foot. (That is accurate within a three percent.) If a plane is proceeding at a ground speed of say 300mph that's about (mumble 88*6 feet per second or about 440'/second.. If you take a reading once a second you have a speed range of perhaps 430'/second or 293 MPH to 450'/second or about 307 MPH. That may be accurate enough if the plane is not in distress. If the plane's dynamics change on a second by second basis, as with turbulence, it might not tell you quite as much. At a tenth second you have 23% error bands without some smoothing rather than 2.3%.

I'm not sure what speed accuracy is needed for being happy within a cockpit. I suspect 2% is acceptable and 10% is not. GPS is perhaps marginal. Over a 10 second interval GPS velocity determination is, of course, much better than my bogey numbers.

Another detail to remember, if you are dealing with high dynamics or simply high speeds, is that GPS tells you where you were at the time of measurement not where you are at the time you read it. To the extent that the distance traveled during that interval matters this detail is important to keep in mind. Fortunately the various filters in the system "take up the slack" on this detail.

She knows more about GPS than she would like to bother with. You guys have, for more than a couple decades, been relying on some work I performed while at Rockwell International in Anaheim on the satellites as designed in the late 70s. At that time it was a pasttime of mine to "annoy" AF officers over their silly "dithering" pointing out differential techniques render it pretty much moot. It does provide a nice way to gain precision from the oscillators, though.

auv-ee
I was concerned with that towing scenario and potentially snagging the ROV to cage tether on rocks given the mountainous terrain.

{^_^}

All this techno-babble about GPS/INS etc. All we need are:

1) Multiple (3?) probes with adequate heating

2) Instruments which provide basic attitude and engine settings WITH NO COMPUTER INTERFACE for use in any failure of 1)

3) Crews trained to use 2) if 1) happens.

So simple.:ugh:

It's all about situational awareness. With lights, cameras and maybe an altimeter (acoustic range to bottom) on the cage/depressor, this can be done. Remember that 1knt is only 0.5m/sec horizontally, and the winch rate is typically 1-1.5m/sec; it's manageable. Doing this depends on the tools available to the operator (tether management between depressor and ROV, adequate visibility, ...), the operator's skill, and the severity of the terrain/currents. Certainly there are times and places where the ship can move with the ROV deployed, and others where it cannot.

Salute!

Thank you, BOAC. Well said, IMHO.

The current crop of "Playstation" pilots and crew are beginning to scare me.

Fer chrissakes, point the plane best you can using the ADI or stby gyro and keep power where it would normally be. NO AUTOPILOT in turbulence. Let the jet fly as it was designed to and she'll prolly do just fine.

Seems we had a "bus" Delta crew with a loss of IAS and such and they did just fine holding attitude and normal power setting ( inbd to Tokyo?). Sheesh

Gums sends ...

Can't fly pitch and power w/o AH and throttles, though. The AH is an option, only luddites would want one.

bear

Yes the engine probes in the A330 fitted with Roller engines did suffer this problem. RR engines have a P1 probe to measure pressure ratio as the thrust is measured as EPR.

Quite a few years back I had a pax visit to the fight deck of my A330 and who was an engineer from RR Derby. I (actually the a/c) was able to demonstrate this problem as we negotiated TS's over the Philippines and each engine was affected in turn by icing as the supercooled water at cruise altitude exceeded the heating capability of the probes. The effect of the icing of the P1 probes was to reduce maximum allowable EPR (blue triangle in the EPR gauge) in each engine as it was affected by icing. The RR man was excited to access the data from the MCDU (under supervision of course).

I subsequently learned that RR first knew of this problem from experience on the B747-400 but they were reasonably unconcerned as the consequential P1 error from icing was temporary in time and reduced the max allowable EPR and therefore was considered to be safe.

BEA Phase 3 Update
 

BEA has updated their Phase 3 Search page to briefly describe the results of the search. I don't see any new information, other than an updated search coverage map.

Sea Search Operations

Given that the need for true backup airspeed is rare here is another possible option:

Deploy the RAT (ram air turbine) emergency generator and use the RPM and generated power to compute air speed.

This would also require air temperature and static pressure for decent accuracy, although even without those a usable estimate might be possible.

I don't know if this is at all practical (max speed etc) but it would certainly be an alternate method.

(I created a similar message yesterday but appear to have not actually submitted it, so pardon in advance if this shows up as a dupe.)

AoA in gust encounter
 

For whom it may interest - How AoA changes when encountering an upward gust:
25 fps gust
35 fps gust

HN39

Murphy Sez
 

The rat will also accrete ice and given that it (probably) isn't heated will ice up pretty quickly.

As an old f@&t, I have to say that if you really get into icing and turbulence (which you should avoid anyway), the way to survive it is to keep the power at cruise settings and fly attitude. Ignore altitude fluctuations. Turn the autopilot OFF or you'll be fighting it constantly. You will move up and down with the air mass but as long as you are stabilized within the air mass, you will get through it.

HazelNuts39;

Very interesting.

Looking at the graphs in post #1467, I sense that the relationships between AoA, vertical gust velocity and "g" are fairly linear, and riding a 50fps gust is going to give an AoA of 5.6 degrees and 1.72g. Does using a fixed mixing zone figure, e.g. 300 feet, produce a higher "g"?

It follows that loss of an effective CL is a given.

mm43

mm43;
thanks for your reply. The 35 fps gust with 300 ft mixing zone will result in a peak AoA of 5,0 degrees and 1,55 g. At higher AoA's the cL-alpha will become non-linear and "g" will be limited by cLmax (stall).

35 fps 300 ft

regards,
HN39

DECONSTRUCTING the BBC Treatment in the Search for alternative explanations
 

To assist an author looking at the entire vista of AF447 plausible scenarios, I've deconstructed the BBC transcript to as much as possible offer one alternative explanation.
.
The first file is the unexpurgated BBC transcript and the second is a commentary on certain aspects of that (with the line numbers in the 2nd file relating directly to the BBC transcript's line numbers).
.
RIGHT-CLICK save as ......
.
Please feel free to comment upon either/both (seeking validation/verification).
.
a. BBC Transcript
..................link one
.
b. Comments upon the BBC program's treatment of the AF447 mystery
..................link two
.
..................

If the underlying problem is that there can be both too little and too much pitot heat, then it seems that the logical approach is the direct one: to embed a thermistor in the pitot head and regulate the heat (for example, by duty cycle) to maintain a safe temperature at any speed/altitude. Someone likely knows a good temperature to use for the core of the probe that would keep the whole probe ice-free, possibly 40-60C?

@UNCTUOUS

What is your mechanism for a pitot to slightly under-read?

If the ram-port blocked the the indicated flow will fall to zero if the drain open - guess you are looking for partial blockage of ram with drain open? If the drain also blocked the total pressure locked and indicated flow will vary with static pressure (known danger during take-off climb). I fear drain holes blocking at similar rate on more than one pitot could lead to small over-read before all 3 disagree, but as Takata has already pointed out still unlikely.

What are the real speed margins before or after a reduction in speed for turbulence entry?, and what is magnitude of drain hole blockage effect? If ice detected/suspected how much engine power will be used on wing anti-icing measures?

@auv-ee

Its going to be very difficult to maintain the temperature of pitot tube in 500 mph wind at much above the ambient air temperature - monitoring the power needed would turn it into a "hot-wire anemometer". If melting out ice the surface in contact with the ice will be at the freezing point of the water - a principle you could use to detect ice! You do need temperature control when on the ground to avoid turning the probes into soldering irons.

Hi,

UNCTUOUS
Thank you .. good job.

@UNCTUOUS

In your section 173: "An ACARS message from the airplane recorded the sudden onset of critical Mach and the autopilot disconnecting due to the high aerodynamic trim loads it was holding (and no longer could)."

There were no ACARS messages recording "the sudden onset of critical Mach." The AUTO FLT AP OFF message arrived at 02:10:10 quickly followed by AUTO FLT REAC W/S DET FAULT (unavailability of the reaction to wind shear detection function), then F/CTL ALTN LAW (PROT LOST) and the others.

Overspeed/underspeed/stall as part of the upset sequence has been discussed at length on this and the prior thread, and remain still in the realm of whatIfs. MachCrit is but one of the possibles. Need the black boxes to work out the sequence.

I'd be interested in your expert opinion and description of the politics that might be influencing the science of the "researches" so far. Who are the interested parties and national and international stakeholders; what are the lawers looking for (and why); what are the truths that would be favorable or unfavorable to these groups and why. Can the truth be bent in such investigations? How? That description would in many human ways define our times...

GB

The following linked input (for the same author) may answer that:
.................link
.
One of three likely events precipitated the upset:
a. BBC Scenario - Pilots neglected to add power (i.e. left throttles in CLB) after dial-selecting a slowdown to turbulence penetration speed and this led to an autopilot kick-out and stall/LoC following the airspeed indicators winding back to zero (the pure precipitation instant pitot freeze-over theory). Considered an unlikely confluence of events in comparison to (b. below) - a more insidious development during a relatively smooth cruise in the dense CirroStratus cloud to be found in the ITCZ areas (i.e. crew ennui/lethargy/surprise more likely to be a player than when alert and roughing it in the grip of a storm).
.
b. Favoured Scenario - Autothrust quietly adds power incrementally as supercooled ice crystals overcome the limited pitot-heating abilities and gradually accumulate as a granular filter inside each pitot (clogging drain and tube equally). Pilots fail to notice power adds or fuel flow increases as it's common to monitor the fuel management synoptic in long-haul (vice the engines page). In fact it's probably SOP to do so - as any engine fault will be separately annunciated, whereas fuel transfer discrepancies or leaks will only show up latterly). Aircraft hits Mach crit and mach tucks (autopilot disconnects and a/c pitches down violently).
.
c. Possible Scenario - As per b., however autopilot kicks out prior to Mach crit, due to one of:
(i) Holding too much pitch force due to THS being incorrectly trimmed by invalid airspeed data (...and a/c pitches them down into Mach Crit)
(ii) Airspeed splits becoming large enough to trigger a system-detected discrepancy..... and A/P kick-out occurs
.
In any of these three cases, particularly if the THS was in an out-of-trim state at A/P disconnect, the crew would be without airspeed info and therefore prone to hitting either an aerodynamic stall or Mach Crit. This would quickly lead to an "upset" as the Airbus Flight Control system protections in Normal or a degraded Law (ALT 1/2) would not be able to prevent an unusual attitude developing. Any misinterpretation of their predicament would put them in a world of greater hurt.
.
e.g. Max power and stick forward as a result of an assumed stall would embed them in Mach tuck. Rolling the wrong way in an attempted roll-out from an autorotative flick-roll would be an entry into an unrecoverable unusual attitude. Large bank angles always involve steep nose-drops - which lead to rapid acceleration of a heavy jet at height.
.
Finally, GreatBear said: "There were no ACARS messages recording "the sudden onset of critical Mach." Well think it through. Why would there be in any airspeed pitot compromised scenario? It's not a missing message, it's a disabled capability. That's one of the issues that I have with the cascade failures typical of (and endemic to) interdependent and integrated automation.
.

- excuse a dumb q from a non-AB chap - isn't the A/T supposed to do that?

Unctious- I am now totally confused as to what you are presenting regarding BBC/ACARS. First you 'present' "An ACARS message from the airplane recorded the sudden onset of critical Mach" with no comment and then you tell GB "Well think it through. Why would there be in any airspeed pitot compromised scenario? It's not a missing message, it's a disabled capability."

Thanks, BOAC, my point exactly.

UNCTUOUS. I'm still having trouble picturing the auto throttle creep necessary to your "favoured" Mach tuck scenario when, by measuring ground speed until the upset (A/P disconnect, ten seconds after the last position report), the A/C seemed to be traveling at a constant cruise speed... see diagram. Perhaps creep towards the upper right of the coffin corner (+20kts? +40knts? +more? to a flick-roll) occurred in a very short timespan? Short enough not to influence the 0200 to 0210 distance traveled segment?

GB

/Quote GreatBear
Hmm, without change in attitude this seems technically not feasible to me given the SEP of an A330 @210t at FL350.
That will take 'ages' to get it to Mcrit given a constant level attitude (>10min).
Had it left that level attitude before than something was pear shaped anyway.
Or they pushed the nose down due to a perceived risk of a stall.
Either way you see it a subtle Mcrit encounter without preceding event seems not very likely (at least to me).
However, an Mcrit encounter after an initial LoC seems absolutely possible.