DC ATE and CAPT AIRCLUES
You two are the only people on this thread worth reading.
Ouch!...
Quote:
and given a choice between descending and getting my pitot tubes back and using more fuel or NOT getting my pitot tubes back and dying...what is wrong with this question.
I haven't left North America in my flying. But I have had to fly below the Flight Levels in jet transports for various reasons...the fuel penalty isn't that great...it is doable,manageable etc.
In setting aside the fuel penalty for flight at substantially lower altitudes with turbine-powered aircraft, which engine-type are you referring to, the PW1's or the high-bypass PWs or Trents? I don't know what the fuel flows are for the smaller engines but I think the differences would be among the factors affecting the decision-making process to descend. A descent to say, 10,000ft for "warmer" air could increase the burn such that one is burning into all contingency fuels and possibly the MFOB. It's a very big decision. Of course, (as DC-ATE points out), diversion fuel should be in the plan, and of course it is - in this case, a diversion, say, to Recife, in a serious emergency, would be a possible choice. Of course, we do not know what this crew faced.
That isn't to say a descent to clear ice buildup is unwise or questionable - the captain must do what s/he must do to ensure safety and survival, but as you would know, the decision is not a simple nor a straightforward one.
I tend to think that in the emergent circumstances faced by the AF cockpit crew, the time and therefore the availability of such a decision was perhaps not there. What do you think?
Quote:
GEE GUYS (not dc8 and clues) ...what happens if you lose pressurization...and have to fly at 10,000feet!
Planning for these kinds of contingencies by overseas long-haul carriers is a matter of routine policy including pressurization loss and engine-out descents. - quick example, YVR - HNL, a plan involving a diversion at 10,000ft with engine ice ON would use SEA, PDX or SFO then HIL/OGG depending upon winds/temps.
Diversion routes from anywhere along the flight-planned route as well as at either the equal time points or equal fuel points are analyzed for potential icing at 10,000ft. Where indicated, fuel is added to handle the additional burn. In these cases, the emergency plan is to arrive at the diversion airport having burnt into the MFOB.
ClippedCub;
Quote:
A classical spin entry into the water could explain a lot if the debris dispersion can be explained by wind and currents. Reviewing the 3-view, the rudder would be blanketed by the horizontal and with the wing sweep it would wind up pretty tight. The pitots wouldn't agree due to yaw rate and the rudder would be left in limited travel. Would be a tough recovery if it was even possible with the rudder limit. Would require a fluke (500 year?) warm air column with a sideslip at the stall break tough.
The notion that AF447 possibly entered a "flat spin" has been broached a few times.
I am not an engineer nor a mathematician so my question is informed by a bit of reading...always a dangerous thing! Please bear with me as I had never asked the question as to whether a transport category aircraft could "flat" spin:
Given some distance between the two points round which any aircraft, but in this case a jet transport, would be theoretically rotating in a spin, namely the forward point or center of gravity, (weight?) and the aft point, center of lift and given a normal CofG position (about 4k kg of fuel would be in the tail at that point), and intact vertical and horizontal stabilizers, could these two points produce a flat spin under specific circumstances?
I have always perhaps laboured under the understanding that a transport category aircraft in a fully-developed stall would produce a substantial nose-down pitch attitude, possibly with spiral characteristics if roll angles were high and which would take an enormous amount of sky from which to recover.
I realize that any mass can "spin" and any aircraft with a narrow CofG, CofLift relationship could be made to flat-spin, but the development of same given usual characteristics of a high-altitude full stall do not seem to me to be conducive to the development of a flat spin.
There is precious little in the literature. D.P.Davies covers it but there is no discussion about "flat" spins, just the spiral dive stability and of course the various stall conditions including the "super-stall".
The question is "out there" and has been asked, so I think it is important to understand the nature of the stall, the spiral dive and the propensity to spin (or not) of this kind of airframe/airfoil.
If the mods deem this "Tech Forum" stuff, so be it - see you there. I think however it is "in context".
I'm sure the Brazilian/French team has spent hundreds, more likely thousands, of navigator man-hours best-guessing the "Ultimo Reporte" location and the debris drift.
they did not "best guess" the "Ultimo reporte"
This is the last VHF transmission of reporting point by the crew before leaving the Brazilian controllers. It is established that this report was made at 01:33 estimating TASIL at 02:23.
Though I agree, the search was initially launched by applying current/wind drift patterns.
- Most newspapers are today saying that the plane broke up in mid air. How is this possible? I always thought that airplanes could withstand all kind of punishements even fly inside the meanest cells (after all C130's do fly inside hurricanes) without breaking apart.
- Why did the crew decide to proceed inside a cell/storm that by looking at Tim Vasquez analysis for example, looked like a monster?
- There is ABSOLUTELY NO EVIDENCE that the plane broke up in the air. Media are picking up info, among other sources, on forums like this one !!!... where all kinds of pros and not so pros make comments, speculate, emit possibilities, pretend they are experts etc...
It is majorly BOGUS !!
C130 and other hurricane chaser airplanes are structurally MODIFIED to withstand extreme turbulence stresses. That's why they can fly inthere !
A civil airplane is not so modified and possibly could exceed its structural limits under certain circumstances, which are linked to LOSS OF CONTROL in flight.
An Airbus has Load factor protection in normal flight, and only looses this protection when Flight controls systems are severely degraded.
Load factor will however not protect them from other structural exceedance such as flying too fast (ie the never exceed speed)
Without going into too many details here....of course.
- There is absolutely NO EVIDENCE that the crew flew into a cell.
- There is absolutely NO EVIDENCE that there was any monster cell (typhoon type)
Even Tim Vasquez is being careful with his model.
Weather analysts report that the Convective weather pattern that night in that area did not present anything out of the ordinary, everyday equatorial storm system.
Found an interesting discussion in the Tech Log forum on spin recovery in a 737 - theoretical I hasten to add - but spooky as the message is dated 20 May!
Quote:
The last position message from the airplane was broadcast by the ACARS automatic system at 2 h 10 UTC.
- any link to the 'press release', preferably in English? What do we have here? Runaway journalistic mis-interpretation of a statement? A previously unreleased ACARS message or part of? Just a spoof - or have I simply missed this pos report? If so, apologies - there's a lot of static here.
If true, and we ASSUME things went badly wrong at 0214Z, we have a circle of only 4 mins or so of flight to fix the initial crash site.
OK, captainflame and Finn47, "best-guessing" (not second-guessing) the seabed location of the AF447 hull is a PROCESS based on probabilities and a pot full of known and inferred datapoints. Debris locations and "Ultimo Reporte" are datapoints in that pot... Perhaps I should have said "best-guessing from the known and estimated flight path of the A/C and the location of found debris;" all are datapoints. Sorry for the confusion. Likely at play here is Bayesian search theory.
The most interesting search in similar circumstance to AF447 was conducted in 1968, for the nuclear submarine USS SCORPION, where Dr. John Craven, the Chief Scientist of the U.S. Navy’s Special Projects Division, successfully used Bayes’ Theorem of subjective probability to ultimately locate the wreck far from where many thought it should be found. The pot of data available in the AF447 case is eerily familiar:
"On May 27, 1968 USS SCORPION was reported missing with ninety-nine men on board. Nobody had any idea where SCORPION was or what had happened to her. All they knew was that the 3,500 ton nuclear attack submarine was due back in Norfolk, VA and had failed to arrive... The site of the first explosion – codenamed Point Oscar - marked where the search would begin. The water at Point Oscar was 2 miles deep. The SCORPION would have stopped imploding about 7,000 feet before she hit bottom, cutting off the acoustic trail. Depending on how fast she had been traveling, and in what direction, and depending on the force of the implosion and the position of her stern planes as she fell, she could have been thrown miles further... [Craven] asked a group of submarine and salvage experts to bet on the probability of each of the different scenarios being considered to explain SCORPION's loss. Once the bets were completed Craven sat down to draw a probability map... Years later mathematicians would write a book based on their work with Craven entitled "Theory of Optimal Search," the U.S. Coast Guard would adopt the method for search and rescue, and the Navy would use Craven’s interpretation of Bayes’ Theorem to locate sunken ordnance in the Suez Canal." (A good read at http://en.wikipedia.org/wiki/USS_Scorpion_(SSN-589))
This PPRuNe thread has been helpful, I should think, in providing expert data points and scenarios. As I said in my last post, likely thousands of expert hours have been invested in answering the best-place-to-search question. Certainly a lot of assets have been deployed to search "somewhere."
"Bayesian search theory is the application of Bayesian statistics to the search for lost objects. It has been used several times to find lost sea vessels, for example the USS SCORPION. The usual procedure is as follows:
1. Formulate a number of hypotheses about what happened to the vessel.
2. Corresponding to each hypothesis construct a probability distribution for the location of the vessel.
3. Construct a probability distribution for actually finding an object in location X if it really is in location X. In an ocean search, this is usually a function of water depth — in shallow water your chances of finding an object are good if you are looking in the right place. In deep water your chances are reduced.
4. Combine the above information coherently to produce an overall probability distribution. (Usually this simply means multiplying the two distributions together.) This gives the probability of finding the vessel by looking in location X, for all possible locations X. (This is like a contour map of probability.)
5. Construct a search path which starts at the point of highest probability and 'scans' over high probability areas, then intermediate probabilities, then the low probability areas.
6. Revise all the probabilities continuously as you search, i.e. if you have searched location X then the probability that the vessel is there is greatly reduced (though not usually zero) and the probabilities of all other locations must be increased. The revision process is done using Bayes' theorem."
Press release 12 June 2009
Flight AF 447 on 01 june 2009
A330-200, registered F-GZCP
During the third Press Conference that was held on 17 June on the progress of the investigation into the accident to flight AF 447, the BEA presented the sea search operations that are under way. It contains a map of the locations of the airplane debris, including the fin, that were recovered from the surface of the sea. This debris field corresponds to a relatively small area with a drift towards the north.
A targeted undersea search area has been established based on the position of the parts recovered – more than four hundred items have been referenced – and on the flight path of the airplane reconstituted from data transmitted by the ACARS. Exploration began on Wednesday 11 June with an increase in the means deployed until 16 June 2009.
During this press conference, the few validated facts available at this time were set out and detailed:
The airplane was in cruise at flight level 350 (about 10,500 metres).
No messages indicating problems were received on the air traffic control radio frequencies.
Close to the planned route of the airplane above the Atlantic there were significant convective cells characteristic of the equatorial regions;
The last position message from the airplane was broadcast by the ACARS automatic system at 2 h 10 UTC.
Between 2 h 10 and 2 h 14 UTC, 24 maintenance messages were transmitted by the ACARS, including 14 between 2 h 10 and 2 h 11.
Analysis of these messages shows inconsistencies between the various speeds measured. Most of the messages appear to result from these inconsistencies; they correspond to the loss of several flight assistance systems.
49 bodies were recovered between 6 and 11 June 2009.[/
I realize that any mass can "spin" and any aircraft with a narrow CofG, CofLift relationship could be made to flat-spin, but the development of same given usual characteristics of a high-altitude full stall do not seem to me to be conducive to the development of a flat spin.
Wasn't referrig to a flat spin, a regular nose low spin would explain a lot.
Spins occur when one wing is stalled and the other is unstalled. The Bucker Jungmiester and Jungman are legendary for snap roll and spin performance and the primary reason is because both upper and lower wings are swept 11 degrees or so. Pull into a stall, yaw, increasing sweep on one side and decreasing sweep on the other. The outer unswept wing produces more lift because it is now unswept and traveling faster. The inner wing is now effectively swept 20 degrees and is moving through the air slower than the outside wing.
Visualize this same dynamic starting with 25, 35 or even 45 degrees of wing sweep. It would be almost like effectively losing the entire wing on one side. The aircraft would spin like a top.
Once entered, since the engines are underslung, power would tend to flatten the spin out. Would imagine the engines being slung off in short order, since the spin would be violent once it was well developed. Would take a turn or two to really wind up and stabilize. Then the cg would travel aft which could promote flattening.
The assertion wasn't whether it was flat or not, either type of spin could explain a lot, long as it were upright.
Re the comments on weather radar. It shouldn't be forgotten that radar cannot see through cells. It may be that AF avoided a cell only to find a massive cell hiding behind it.
WHAT is going on here?! Someone posted a very good explaination of aircraft radar in response to the above post. Because of that, I did not respond to save an 'extra' post being displayed. There were NO bad remarks or speculation in that response. It was deleted either by mistake or intentionally. Wish I would've saved it along with the persons name. Anyway.....my response was going to be something like:
I do not know what weather radar systems are in use today in 'modern' aircraft, but we had C-Band radar that COULD "see" through storm cells with NO problem, thereby enabling one to navigate through and around storms.....IF one chose to fly that way. I personally used the weather radar for its intended purpose. And that was to AVOID the weather, not find your way through it.
We do NOT know what the situation was with AF447 and their use of their weather radar at this time, and perhaps will never know. While it appears as though they were too close to the 'bad' weather, we really do not know.
I do not understand why someone is allowed to make a remark on here that is false and have their post remain only to have the rebuttal post deleted.
Thanks, DC-ATE. I re-posted it over at Tech, where it has already passed the good censor.
UAL used to say the other airlines avoided storms, while they co-existed with them. You may have got a rougher ride on UAL, but they always made it.
UAL was known for exceptionally good WXR training, whereas it was sadly lacking nearly everywhere else in the US. Astute airlines sent their pilots to UAL for Wx training.
GB
Last edited by Graybeard : 18th June 2009 at 14:42.
Reason: More info
BEA .pdf detailing locations of debris and corpses
From the June 17, 2008 BEA press release quoted above by OleOle, there is a link to this .pdf that answers lots of the questions asked repeatedly about the investigation, including:
ships deployed
data exchange between French and Brazilian authorities
day-by-day maps of the locations of debris and corpses found
undersea map of area
how the beacons on the FDR and CVRs work including a sample of the sound
how the undersea searches are organized
Last edited by Not_a_pilot : 18th June 2009 at 16:32.
Reason: linked the June 17 press release on the BEA site
Public communication about aviation accident in France is strictly controlled.
There are very few people that will be allowed to speak through any media.
Almost only two:
Gérard Feldzer is one of them. Former Airbus pilot and instructor on Air France. He is retired and is now the Director of the Musée de L'Air et de l'Espace at le Bourget (very nice museum by the way).
François Grangier is the second one. Presented in all the Media as an Airline pilot and aviation accident expert at the BEA. It is almost impossible to know more about FG and particularly what airline employs him. Last time I saw him on TV he said he was just coming back from HKG but no journalist would be impolite enough to ask him on which airline. On some French forum there are (sarcastic) members saying that FG was driving the FGZCP when, while taxiing, it unfortunately cut an A320 horizontal stabilizer. I would therefore tend to think that FG is an AF pilot that is detached to the BEA if needed. Grangier has his own site that you can easily find.
These two persons are allowed to speak about airline crash and especially when it happens to a French airplane.
Because things are going fast and these two can't be everywhere, we can see others members speaking of the accident aircraft on various media. Always AF pilots and always members of the SNPL (syndicat National des Pilotes de Ligne) Union. All these AF employees can speak freely and say what they want about a disaster involving a (their) company aircraft.
FG at the end of a recent French TV talkshow on the 2nd of June ("C dans l'air" on France5 ) said something astonishing but very revealing of his state of mine. At the end of the emission some selected questions from the audience are sent by SMS. One question was about the ability of the submarine's sonar to get an echo from the bottom of the sea. FG sharply answered "Dead bodies doesn't make noise."
Unfortunately the broadcasting is not available in its integrality now. But you can see the latest one here (with GF of course, see below please).
My personnal feeling and I'm very sorry to say that, is that some people within official bodies in France are praying that these boxes shall never be found.
The "C dans l'air" talkshow of the 16th of June was titled : AF447 corpses are "speaking" (still watchable in its integrality but not for long I'm fraid because it's reduced after a while)
Well only the fact that bodies were found 80km apart was discussed but nothing else interesting and, rather amazingly no doctors expert in autopsy were present. At the very last seconds of the talkshow there's a SMS question : Is the BEA independant from manufacturers, economic pressure or Grandes Ecoles? Answer by GF ( not FG this time...): No.....the BEA is (people starting to smile) influenced by nobody...heu yes it's the contrary, it's independant. Phew!
About the BEA. Some months ago their internet address was Bienvenue sur le site du Bureau d'Enquêtes et d'Analyses (yes .org !)to underline their total and absolute independancy from any States, Authorities and lobbies whatsoever.
This address/URL has changed (redirected) but if you still type it like this (or follow the link) you will reach the site. For how long? The BEA is depending of course of the Civil Aviation General Direction (DGAC) subsidiary of the French Ministry of Transport. We do not know the exact constitution of the investigation team. Who they are is a mistery. BEA is not the NTSB. Nothing on its site about that. Is there any member(s) of Airbus and/or AF, the answer is yes or very likely no, but normal ordinary French citizen still don't know about that. But the BEA is independant. Like in any modern western countries.
BEA has announced that it will try to publish a report before the end of June. It simply forget to mention that it is ICAO mandatory to publish an "intermediary" one within one month of an aviation accident.
What we know is that Paul-Louis Arslanian is the Chairman of the BEA. There was a press conference yesterday hold at the BEA office at Le Bourget. Nothing special happens except that BEA is saying that they know nothing about the bodies recovered. It can't be serious because we read these informations via the internet from Brazilian side. PLA is very displeased because the Brazilian medical team has forbidden to a BEA expert to enter their forensic laboratory at Recife. There are already 3 French experts in the place who are working with the Brazilian specialists but the BEA wanted their one to participate.
When a Brazilian journalist asked a question (+5mn47sec). We can hardly hear the question (in French) of the journalist but PLA said that he doesn't speak Brazilian (this journalist spoke a perfect French) and somehow abruptly give the parole to another journalist. This new journalist (female) questionned PLA on something ( I could not understand because journalists did not have a microphone) and he became irritated again.
At +2'34'' he said something about bodies "Tous les corps qui sont ou seront trouvés seront récupérés."
"all bodies that are found or will be found will be recovered" We can then hear some people starting to laugh.
Later on (+5'00) he said that "May be we are effectively approaching a little bit more of the goal" : "on se rapproche peut-être effectivement un peu du but" (with a restrained smile).
Many of us come here to read, learn and see what is happening in the aviation business. Its very interesting and not locked away as a private forum.
So PLEASE, would all the armchair pilots and those asking questions that break up the threads, please stop posting. Its pretty obvious that those users in the know (real pilots and technicians) are gradually working through a process of elimination and while it might not be used directly in the investigation, you can bet that there are people browsing the site in order to either jog their memory or examine other avenues that are mentioned.
Google is there, if you want to find out how systems work, google it, but please don't wear down the patience of the pilots, we don't want them to stop posting, the topics go stale or the board become exclusive.
Thank you for your time and the professionals for having us non-flyers here!
Way back in this thread (or was it in the locked thread?) I expressed my opinion that more was known about the cause of this accident than was being said publicly.
Nothing new really. It's been suspected from the very begining. let's suppose for one second they went through the same incident Qantas did in the kind of weather they were flying. You're toast. The fact that AF shows full confidence in the Airbus is quite understandable. Imagine what trough we'd be in if the fleet was grounded. That would be the death of us.
DC-10 fleet was grounded on less evidence than we have so far on the A-330. L-188s kept flying despite two in-flight shreddings because a California-based airline had only Electras in their fleet. Economics dictate safety policies.
they did not "best guess" the "Ultimo reporte"
Linear Mode
