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In the chapter AoA versus the lower range of speed/Mach at high level, there have been already some divergent opinions. But I came across some interesting piece of information by the manufacturer :
FCOM 3 SUPPLEMENTARY TECHNIQUES FLIGHT CONTROLS STALL PROTECTION http://i65.servimg.com/u/f65/11/75/17/84/aoa_0011.gif We might now agree that the AoA figures produced by HN39 in his earlier post are pretty much in the ball park, and that anything above 5 degrees of pitch attitude for a level flight is highly suspicious … This leads me to think that the MEMORY ITEM which request to take 5 degrees up and CLB thrust in case of UNRELIABLE SPEED INDICATION is not adapted therefore not applicable for a high level situation. Definitely, such event should be trained in the simulator, and a concise and adapted procedure should be put in place. Another big question mark is how the protections could come into play and eventually interfere in the overall process ... The scenarios are multiple and some are scary. Airbus is absolutely silent on that matter. I’m not too surprised that very early after June the first, the main idea of the monster thunderstorm has been widely and conveniently disseminated, enough that people take it for granted :
Originally Posted by Smilin_Ed
In any event, whether a direct reading AoA gauge would have saved AF447 remains to be seen, but when you get right down to it, they broke one basic rule, "Never, ever fly through a thunderstorm!"
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rgbrock1...
You have posed a most interesting question. In terms of the official investigation, with or without the recorders it will continue. As part of that, more research will be done into the aircraft's systems and equipment. More extensive analysis will be done on the recovered parts (these things are already being done, no doubt). Two other points: 1 People think mostly of the recorders, but finding the main portions of the aircraft (even without the recorders) will be of immense value to the investigation. 2 In this day of private enterprise, and adventurers with buckets of money, I think (IMO) it is highley likely that someone other than the responsible "authorities" would endeavour to locate the aircraft if the official search is unsuccessful. grizz |
What's likely left of the wreckage at 2000m+?
This has been bugging me for a while now and I don't have nearly enough understanding of the effects of deep water pressure on an aircraft structure to be confident on my thoughts - but... having worked on a number of simulators for various submarines in my past career I do have some (limited) knowledge on the result of exceeding the crush depth on a submarine structure. It's not pretty.
So what could anyone reasonably expect to find if the aircraft found itself heading for an ocean bed of depth of say 2000m+? My math puts the pressure at around 2900lbs/sqr inch. If that is anywhere near correct, there's not going to be much left that is going to be anywhere near recognizable is there? And secondly, assuming it is found, how would recovery of such wreckage help? Surely the crush forces will have so greatly distorted the structure as to lend it near useless in telling the tale we so hope it might? - GY :confused: |
Remains of the Aircraft at Ocean Depth
The aircraft fuselage would have opened up at impact with the water so I doubt that the individual pieces would have been been further distorted by sinking to great depths.
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GarageYears
It has to be unlikely that after impacting the water the pressure cabin was totally intact. If was intact it would float. If it it leaked it would gradually fill with water on the way down. I don't see where the crush forces are coming from. JF |
Update - "Anne Candies" & "Seabed Worker"
As I reported a couple of days ago, the "Seabed Worker" berthed Recife at 2010-03-22 1110z, and the ETA of "Anne Candies" was 2010-03-24 1100z.
Well the "Seabed Worker" is berthed at Quay 09/10 and the allocated berth for the "Anne Candies" is the same. I currently do not have any information on the whereabouts of the "Anne Candies", but find that since departing Grand Isle, Louisiana on 02 March 2010 that the vessel has called at Trinidad & Tobago. "Anne Candies" was last tracked via the marine Automatic Information System (AIS) on 01 March when in Flotation Canal, Port Fourchon, Grand Isle. Since then, there has been no AIS positions found for her at either Trinidad & Tobago or at Recife. The assumption is that the vessel's AIS has been turned off - not a good look. Piracy is becoming more of a problem, particularly for slow and low free-board vessels, in which case turning off the AIS is a valid form of self protection. The Recife press is reporting "Anne Candies" is due today UPDATE:- "Anne Candies" has berthed at Port Suape (8 24S 38 57W), about 30NM southwards along the coast from Recife. It seems that there is a logistical reason for doing so - possibly bunkers. The BEA also has a press conference schedule to keep. Tomorrow, from 1400, the director of the Bureau d'Enquêtes et d'Analysis (BEA), Bureau of Investigations and Analysis for the Safety of Civil Aviation, Jean-Paul Troadec, will give a press conference on the proposed search. |
Tomorrow, from 1400, the director of the Bureau d'Enquêtes et d'Analysis (BEA), Bureau of Investigations and Analysis for the Safety of Civil Aviation, Jean-Paul Troadec, will give a press conference on the proposed search.
Maybe this will inform us of what is happening. |
The only aircraft I have flown with AOA is the Citation 500. It worked well for LRC in still air and on approach. I wish it was installed in airliners but it isn't. If they had AOA on Air France with a pitot/static failure it might have helped if they were familiar with it. I haven't missed it in the last 30 years but AOA was a nice back up. Don't expect it to ever be an airline display. Anybody know how the search is going? Are any of our advanced submarines searching the area?
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RE: Pressures on pieces at the ocean floor, just look at the Titanic (3,800 metres) and SAA Flight 295 (4,900 metres), of which both were fairly deep and large pieces remain.
I really hope they find the fuselage and the recorders this time. There is a good chance that at least something will be found now. 3rd time lucky. |
p51guy
Anybody know how the search is going? Are any of our advanced submarines searching the area? The pressure at 4,000m is 397.815 Atmospheres (5846.27 psi). The French Nuclear Attack Submarine "L'Emeraude" was used in the Phase 1 search in an attempt to locate the ULB pinger - without success. Its safe operating depth will have been much less than the depths to be currently surveyed, and no similar type of military sub has capabilities that are required for this search. mm43 |
Update - "Seabed Worker" & "Anne Candies"
The "Anne Candies" is now berthed at Recife, and is alongside the quay immediately to the north of the "Seabed Worker". The information has been obtained from the marine AIS at 0840z 2010-03-25.
Both vessels are now available for the BEA press conference that will take place at 1700z on the 25th. mm43 |
Originally Posted by CONF iture
(Post 5592450)
Another big question mark is how the protections could come into play and eventually interfere in the overall process ... The scenarios are multiple and some are scary. Airbus is absolutely silent on that matter.
That means the protections drop out in this event, by design. I can't see any better way to design it really - if the sensors are giving known-bad data then the system shouldn't fly, or restrict the flight of, the plane based on that data. |
Hi,
every one of the 30+ unreliable airspeed incidents documented included swtich to alternate law. That means the protections drop out in this event, by design. The wanabee like Wikipedia :) Flight control modes (electronic) - Wikipedia, the free encyclopedia Alternate law The are four reconfiguration modes for the Airbus fly-by-wire aircraft, two Alternate Law (1 and 2), Direct Law and Mechanical Law. The ground mode and flare modes for Alternate Law are identical to those modes for Normal Law. Alternate law 1 (ALT1) mode combines a Normal Law lateral mode with the load factor, bank angle protections retained. High angle of attack protection may be lost and low energy (level flight stall) protection is lost. High speed and high angle of attack protections enter alternative law mode.[5] ALT1 maybe entered if there are faults in the horizontal stabilizer, an elevator, yaw-damper actuation, slat or flap sensor, or a single air data reference fault.[4] Alternate law 2 (ALT2) loses Normal Law lateral mode (replaced by roll direct mode and yaw alternate mode) along with pitch attitude protection, bank angle protection and low energy protection. Load factor protection is retained. High angle of attack and high speed protections are retained unless the reason for Alternate 2 Law mode is the failure of two air-data references or if the two remaining air data references disagree.[5] ALT2 mode is entered when 2 engines flame out (on dual engine aircraft), faults in two inertial or air-data references, with the autopilot being lost, except with an ADR disagree. This mode may also be entered with an all spoilers fault, certain ailerons fault, or pedal transducers fault.[4] |
To re-quote the ALT2 laws with particular reference to AF447-see highlighted words.
Alternate law 2 (ALT2) loses Normal Law lateral mode (replaced by roll direct mode and yaw alternate mode) along with pitch attitude protection, bank angle protection and low energy protection. Load factor protection is retained. High angle of attack and high speed protections are retained unless the reason for Alternate 2 Law mode is the failure of two air-data references or if the two remaining air data references disagree.[5] ALT2 mode is entered when 2 engines flame out (on dual engine aircraft), faults in two inertial or air-data references, with the autopilot being lost, except with an ADR disagree. This mode may also be entered with an all spoilers fault, certain ailerons fault, or pedal transducers fault.[4] |
Machinbird
This area of the discussion wants some clarification, imo. Perpignan had a load defeated pitch command at the last, so could you clarify the relationship between "load protection" retention in Alt Law and the apparent "ADRdisagree" (447) "lack of AoA prot."? Is Speed prot lost with dual ADRdiscrep? What about lateral protections? Is the RTLUfail related to loss of these additional (retained) protections with uA/S? When the autopilot drops out, what happens to its Roll limit of 45degree? Is this factored into load limit, or is "load" in this case only a function of AoA? In other words, are there load limits in Roll, Yaw? With manual handling after loss of a/p, how is the handling cued? bear |
Bearfoil,
I'm not an Airbus Pro and I'm at work without my references. I just read the system law descriptions and apply them in a particular context. The following is based on recollection, and may not be exactly accurate. As I understand it, load protection is sensed by an accelerometer which would not be affected by the loss of airspeed information. Load protection would come from biasing the elevator control signals to relieve the g load and would be available in all but mechanical law. In Alternate Law, AOA protection reverts to an airspeed basis (instead of the angle of attack sensor) so that is why loss of reliable airspeed indications causes loss of AOA protection. With regard to the lateral protections-I will defer to the input of others for the moment. I don't feel I understand that part of the system well enough to speak to it. Machinbird |
BEA Press Conference - Recife
The Brazilian press has given a brief report, which reveals nothing that hasn't been said before. The search area is to be 2,000km^2, which is less than the area they showed in one of their previously published graphics.
An initial 32 day search is planned, and two the vessels involved will depart Recife on Sunday with an ETA in the search area 3 days later. Including the vessels crews, there will be around 200 persons involved in the search - according to Jean-Paul Troadec. I suspect there will eventually be the photo opportunity shots etc.. and a fuller report published in the usual sources in the next day or so. ----------------------- edit:: For those interested in the equipment being utilized, this page Sea Search Operations and its associated links should be useful. mm43 |
AOA Protections
In Alternate Law, AOA protection reverts to an airspeed basis (instead of the angle of attack sensor) so that is why loss of reliable airspeed indications causes loss of AOA protection. In the case of the quote above, the reason Machinbird gives is clearly recorded in the BEA Interim Report No.1 - Code:
o FLAG ON CAPT PFD SPD LIM and FLAG ON F/O PFD SPD LIM (2 h 10)I agree with BOAC on this one. All that is required is a separate AOA indicator - nothing more, and with some basic numbers displayed to allow the PF to establish stable flight using attitude, power and AOA. The Pitots have been blamed (at this stage) for causing the problems mentioned above, but no one knows whether the static ports were also involved, and if so what barometric functions also became suspect. mm43 |
mm43, machinbird;
In re Alternate 2 Law, some time ago on the 2nd thread I posted the schematic below: http://i277.photobucket.com/albums/k...06-07_1518.jpg * Only in case the AOA, of the remaining ADRs, disagrees with the AOA (as computed by the PRIMs). (1) Protection is totally lost, in case of VS1g computation failure (loss of weight, or slat/flap position). (2) Protection is lost, in case of a dual ADR failure (or ADR DISAGREE). (3) Protection is lost, in case of a triple ADR failure (or ADR DISAGREE). (4) Bank angle limitation remains effective in ALT 1, which uses roll normal. However, since ALT 1 is in generally an unprotected law, all protection marks on the PFD are in amber for simplicity. (5) When both elevators have failed, only pitch mechanical backup is available, by using the manual pitch trim control (THS). “MAN PITCH TRIM ONLY” is displayed in red on the PFDs. |
BEA - Press Reports
The following by the Atlanta Journal Constitution appears to provide a reasonable summary of the BEA press conference in Recife. Even has some photos of the two vessels alongside the quay.
New search starting for Air France black boxes | ajc.com mm43 |
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