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Where?
Originally Posted by D Bru
Assuming that 447 @ 2:10 at LKP was still at its FL350, it took still four minutes of flight from there before the CVS + 1800 ft/min message.
I stand to be corrected, but wouldn’t that imply that the V/S of 447 from LKP until then could not have been as such to make it end up (very) close to LKP. It is some time ago that the CVS advisory was discussed. Although other explanations cannot be excluded, it was theorized that the message was probably triggered by the Negative Relief Valve opening. Since it opens at 1 psi negative cabin pressure differential, and assuming cabin altitude was still 7500 ft, that would put the event at around 5000 ft altitude. Just to throw out another arbitrary number, at 220 kTAS, 20 deg. bank, a 360 deg. turn takes about 3'20". Hoping that this qualifies for feedback, mm43; following your scenario, and thinking about the shape of the 'patch', could it be that the bulk of the fuel was lost at impact, to be spread by the northerly wind in one direction, while the rest released on the way down surfaced on another trail? sincerely, HN39 |
Hi,
All this is very beautiful .. but in practice (as we have seen several times) that leads nowhere ... It is still surprising that an aircraft like the A330 (the flagship of the aviation industry both from the point of view structure as avionics and automation) that is equipped distress beacon of a bygone age that even a ship flying the flag of convenience refuse ... Air France seems to be a company worthy of being classified in the companies called "third world companies" |
HN39 wrote:- mm43; following your scenario, and thinking about the shape of the 'patch', could it be that the bulk of the fuel was lost at impact, to be spread by the northerly wind in one direction, while the rest released on the way down surfaced on another trail? jcjeant; The aircraft was fitted to statutory requirements. The Fixed Automatic ELT could have been effective if someone had flicked the switch to ON once LOC had occurred. But that is not what happened, and following the crash, water intervened. mm43 |
The picture of this slick is really intreaguing.
Attention, the following is just hypothetical: If you would assume a flight path course of ~120° i.e. a 270° turn from the original route the part of the slick ranging from SW to NE could be the result of the impact. It has a larger spread than the part from SE to NW. This second part opens up from SE to NW which could indicate Kerosene still spilling out from a source SE of the slick given the general drift direction being roughly South -> North A left turn of 270° could be a theoretical way that the plane could be at 2:15 this close to the LKP. And given that this was close to the reported sighting of other debris early on in the 1st Search Phase there might be a non- negligeable chance this slick might have something to do with AF447. Admittedly this is a very hypothetical assumption but at least it can be made consistent |
Terminal Acceleration
At the end, 447 was not accelerating vertically, it was decelerating. If otherwise, the various velocities would have had to have had several different values, both positive and negative. Cabin pressure value at 1800 is a rate threshold, the actual rate could be much higher, and using this (hard point) datum can lead one astray, imo. His low value of vertical velocity is ~ 96 mph. The high is ~150 mph. With only a slight rotation (per BEA) the value should be at the high range. With radial energy the value would be less, more like the 90-100mph. Can't have it both ways, and BEA seems to have gotten it backward Likewise, 4:00 from cruise to impact means a cone of transmission that would need to be clear the whole four minutes. If spun, the ACARS would have been broken, perhaps for longer than mere loss of line, counting interrogation and recapture, No? stand to be corrected, bear. |
Center wing
The center wing section is perhaps the strongest structural element of a transport airplane, and in some versions of the A330 it contains the center fuel tank. Does anyone know if AF447 had one?
regards, HN39 |
A330-200 Fuel Tanks
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Hi,
The Fixed Automatic ELT How it's "automatic" when someone must activate a switch for the device be operational ? :) On many ships I sailed .. those devices were "really automatic" .. as when they contacted water they begin to send signal with no human intervention necessary ... (no need to activate any ON-OFF switch) Ironic that old rusted ships are equipped with such devices and a state of art technology like a A330 don't have it ... statutory requirements |
jcjeant wrote:- On many ships I sailed .. those devices were "really automatic" .. as when they contacted water they begin to send signal with no human intervention necessary ... (no need to activate any ON-OFF switch) The aircraft was also fitted with portable ELTs, but they were for use in survivable situations and required manual activation. Note: The big problem seems to be how to detect when a crash is imminent, and the costs involved with retro-fitting approved devices. Your marine environment float-free with water activation EPIRB, needs to be packaged differently for use in an aeronautical environment for obvious reasons.;) mm43 |
Cabin Vertical Speed : not that significant ?
Gentlemen,
may I suggest that many people here place way too much emphasis on that ACARS message regarding cabin vertical speed. What the BEA really says only really amounts to this : a 150 ft measured change of cabin pressure in less than 5 seconds. That change need not be real, only measured by the CPCs, the working details of which we have no notion. That might very likely be only a glitch as pressure measurements go bonkers while CPCs try to cope and decide if they have to quit just now or later. In essence, trying to derive aircraft altitude or vertical speed from this information alone goes against sound scientific reasoning. And that is what many do here. There is no proof that end of ACARS means end of flight. That cabin V/S message was likely acquired around 02:10, and could only be sent four minutes later. Thoughts ? |
Svarin wrote:- .... There is no proof that end of ACARS means end of flight. That cabin V/S message was likely acquired around 02:10, and could only be sent four minutes later. Put another way; the longer the aircraft stayed airborne, the stranger the radio silence becomes. There were three other Air France aircraft all within 121.5/123.45MHz radio range during the course of the ACARs sequence. It is a case where something needs to be made of little, yet a lack of precise timing makes interpretation all the more difficult.:sad: mm43 |
interesting
Interesting reference to the V/S article in support of a “deep stall” scenario. Thanks, mm43. On the face of it doesn’t sound as improbable as that. Having said that, I cannot really follow all the mumbo-jumbo calcs. And the FCOM I have states a 7350 ft reference for the cruise cabin altitude on + 2.5 hour flights, so 650 ft lower than the 8000 used in the Squaire’s calcs. This would theoretically lead to a 10 seconds longer presumed flight time. However, the point I guess is not so much to determine the flight time, but rather to fit a “deep stall” scenario with the presumed 4-5 minutes of flight after 2:10. It could be and a late realisation of the situation by the crew, and the flight deck workload once they realised, could indeed explain the absence of distress signals.
It could also fit with the “pollution spot”, in the sense that it would be the result of 447 going down. The implicit assumption of the Drift Group report that the spot could be the result of a “voluntary” release of fuel is quite amazing and even absurd, also taking into account that in accordance with FCOM fuel dumps in thunderstorms are forbidden. Anyhow, IMO even in a deep stall scenario 447 forward velocity is unlikely to have stopped completely and immediately from 2:10. On that basis I still believe she can’t be very close to LKP. That brings me again to the question of 447’s heading @ the 2:10 position report. I know it was discussed in one of the earlier 447 threads and I recall that the 3nm left offset from UN873’s centreline was not considered significant by most (also based on BEA reporting that 447 was until 2:10 following its intended track), although some (such as mm43) pondered that by then 447 could be in a left hand turn. I don’t remember if SLOP was ever discussed in that connection. The Strategic Lateral Offset Procedure over the Atlantic prescribes flight either on the airway’s centreline, or either 1 nm or 2 nm to the right (in this case to the east). So, in that respect 447’s position @ 2:10 should rather be marked as unusual. Dutch |
Originally Posted by D Bru
Interesting reference to the V/S article in support of a “deep stall” scenario. Thanks, mm43. On the face of it doesn’t sound as improbable as that. Having said that, I cannot really follow all the mumbo-jumbo calcs.
* hcbn = 7350 – 750 ft/min X 251/60 = 7350 ft - 3138 ft = 4212 ft Now as a 2.03625437 inHg pressure change gives approximately a 2036 ft altitude change, and as the external pressure is 1 psi more than the cabin pressure (3), the external or aircraft altitude (hacft) is simply: * hacft ≈ 4212 - 2036 ft = 2176 ft 2:14:21 - 2:15:14 = 53 sec rate of descent = 2463 fpm regards, HN39 |
I can't get that satellite image ("pollution") out of my mind.
Regardless of whether it was actually related to AF447, I find BEA's response and comments both puzzling and inadequate. First, this statement: "...this pollution spot may be the remnant of a kerosene release by the plane (be it voluntary or not)." The "voluntary or not" part simply does not make sense. For an international investigative agency like BEA to imply that what we see could be kerosene (jet fuel) from a fuel dump is simply mind boggling. I can envisage NO scenario where a voluntary (i.e. intentional) dump of fuel would result in such a detectable layer of kerosene on the surface. (And I will happily engage in a discussion with anyone who can suggest such a scenario.) The existence of that phrase in the report suggests that the appropriate experts were either not consulted or they didn't assert themsleves prior to that bit being published. Second, this statement: "We have been unable, however, to relate this pollution spot to any impact point of the plane as determined from the debris and bodies found and the velocity fields estimated...." The BEA themselves admit that there are NO specific facts known about ANY of the actual events from the time of last contact until the aircraft's impact with the ocean. NONE. Therefore their conclusion that this "spill" was of no further interest, based on their assumptions and estimates, is a clear example of one of the primary mistakes in any investigation: Ignoring what doesn't fit within your favourite scenario. I hope I'm wrong, but this item could turn out to be one of those infamous legacies discussed in future books and accident investigation courses. grizz |
Intentional fuel dump?
If you had the time to dump fuel mid-Atlantic would you not have better things to do? Surely we can rule out a fuel dump?
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paull
Indeed. Which is another reason that the BEA wording is so puzzling. |
Originally Posted by grizzled
The "voluntary or not" part simply does not make sense. For an international investigative agency like BEA to imply that what we see could be kerosene (jet fuel) from a fuel dump is simply mind boggling.
Are these persons the authors of Appendix 7? Was there a BEA person in the "Drift Group"? Was there any knowledge of flight operations among the members? Perhaps it helps to read the discussion of the 'pollution spot' in the main body of the report is on page 44, accompanied by figure 25 on page 45. |
HN39
Thanks for your adding to my confusion :) Actually, quite reassuring though.
As far as I can see no formal BEA membership in the Drift Group. According to the acknowledgements, BEA paid for some of the work of the group's members and there was a BEA administrator involved in keeping the Drift Group on "a focussed track" (p 144), which could be perceived as very funny were it not that it concerns such a serious occasion. Dutch |
HN39 wrote:- Was there a BEA person in the "Drift Group"? Was there any knowledge of flight operations represented in that group? mm43 |
Air France A330-206 - Fuel Dump?
Does anyone know if the aircraft in question was fitted with a fuel dump option?
mm43 |
You can rule out fuel dumping guys. Very little of what is dumped down to 1000 feet will make it to the surface. By the time AF447 was at 1000 ft, it was seconds from impact.
Trying to be at maximum allowed fuel weight for landing aboard ship, we always tried to save some fuel for contingencies which we dumped at the last practical moment, often on downwind and turning into the groove. The stuff almost completly vaporizes within seconds. Of course, if you stick your canopy into the flight lead's visible fuel plume, you will get a film on the canopy. :} (Don't want it down the intakes though.) |
HN39;
A misunderstanding of the sign of the pressure differential created the "error" in the Squair calculations! So the rational behind his argument fails. However, the damage reported and the BEA's determination of how the flight ended do not match the implied vertical speed. A closer look at when the CVS advisory may have been initiated, and some juggling of a flight termination time could give a v/s that fits with the BEA reports (high vertical speed, 'en ligne de vol', and 'arm 36 g' etc..). So, here is another look at what may have happened:- Two independent pneumatic safety valves prevent the cabin pressure from going too high (8.85 psi above the external ambient pressure) or too low (- 1 psi below ambient pressure). Therefore, a vertical speed in the order of 9,000 fpm looks like a possibility with a crash time close to 02:14:30. I know this has been raised before, but with Svarin raising the issue, another look was worthwhile. In fact, I believe Machinbird offered a similar v/s some time ago.* hcbn = 7350 – 750 ft/min x 251/60 = 7350 ft - 3138 ft = 4212 ft Now as a 2.03625437 inHg pressure change gives approximately a 2036 ft altitude change, and as the external pressure is 1 psi more than the cabin pressure (3), the external or aircraft altitude (hacft) is simply: * hacft ? 4212 - 2036 ft = 2176 ft 2:14:15 - 2:14:29 = 14 sec > rate of descent = 9326 fpm *matches BEA summary of crash. 2:14:21 - 2:14:29 = 8 sec > rate of descent = 16320 fpm *excessive The 9326 fpm rate uses the earliest time the Cabin Vertical Speed advisory could have originated, i.e. immediately following commencing transmission of the preceding fault report message with time of receipt 2:14:20. A further assumption is that the flight terminated 1 second after the Cabin Vertical Speed warning receipt confirmation by the aircraft [02:14:28]. NOTE: WRN messages take precedence over FLR messages. 2:14:20 FLR/FR0906010213 22833406AFS 1,,,,,,,FMGEC1(1CA1),INTERMITTENT 2:14:26 WRN/WN0906010214 213100206ADVISORY CABIN VERTICAL SPEED mm43 |
mm43;
As a general rule, the 332 is fitted with fuel dump, the 333 is not. That said, I agree with paull's and machinbird's comments. Further, the jettison rate is approximately 1180kg/min. There was approximately 42.6k kg of fuel on board, - (BEA 1rst Interim Report, P.20) at LKP. Even given a decision to dump fuel (which would have been both impractical (due time) and ineffective (there is no emergency in the QRH, and none I can think of that would require such action as an immediate need)), it is easy to calculate that there would have been a substantial amount of fuel on board at impact. PJ2 |
PJ2;
I agree with your comments, and had previously said that a fuel dump wouldn't have left evidence on the surface to be detected by the SAR satellite radar. It has been suggested to me in a PM that an attempt could have been made to dump the Trim Tank (if it was even thought about!), though a transfer to the center tank would possibly have yielded a better CG result. mm43 |
PJ2 (and others) have verified my contention that there is no scenario in which one would contemplate dumping fuel (if so equipped) in a mid-Atlantic ditching event. And even if fuel had been dumped at altitude (or otherwise released in a pre-impact break-up scenario) there is no way it would arrive at the surface, nor remain on the surface, in such a detectable form.
So let's agree to ignore the Drift Group's use of the phrase "voluntary or not" and simply deal with the "slick" or "pollution" or whatever it was that existed on the sea surface when the satellite took that shot. The "stain" (as I would prefer to call it because we don't know what it actually is) is approximately 1km in length at its longest point and perhaps half that in total width (widest point of separation of the two arms). Did it show in any other shots taken in the hours or days before or afterwards? Seems not, or that would have been reported, so all we know is that an anomaly existed that could have been kerosene at a time and in a location that generally corresponds with the disappearance of AF447. So my point is simply this: If that exact location was not surveyed thoroughly by the undersea location resources when they were available, it could turn out to be a major blunder. Discussion? |
mm43;
It has been suggested to me in a PM that an attempt could have been made to dump the Trim Tank (if it was even thought about!), though a transfer to the center tank would possibly have yielded a better CG result. The CG would move forward as you say. However, moving fuel forward from the trim tank to alter the CG, (the CG is thoroughly monitored by this and other systems and as such there shouldn't be a CG problem in any flight regime), can be accomplished without dumping if such is not required, (and given the dump rate, it is likely to be unhelpful in an emergency). The T.Tank selector switch can be used to OPEN the Trim Tank Transfer valve and all fuel will transfer forward to the center tank. The process of transfer seems to take a while but I've never directly observed/timed it. In any case, I think we've kind of beat this one up... PJ2 |
PJ2 wrote:- In any case, I think we've kind of beat this one up... Thanks grizzled wrote:- So my point is simply this: If that exact location was not surveyed thoroughly by the undersea location resources when they were available, it could turn out to be a major blunder. It may well prove to be a bad call, but we with 20/20 hindsight are left to argue and wonder about the spots relevance. In my original post on the subject, I indicated that further work may bring this Pollution Spot into sharper focus. On the other-hand it may turnout that the Drift Group were right. Either way, we are in the "know" and will be able to say, "We told you so!", or quietly merge into the background noise. mm43 |
Regarding the pollution spot it would be important to know how frequent the satellite crossed/pictured that area, i.e. if it took images the days before and after.
Having that information one could conclude from the preceding or succeeding images the relevance of this pollution for AF447. As a standalone information it is not sufficient to derive or rule out the relevance. Any one here knowing/having an idea in which intervals this satellite would take pictures of the same area ? But to be honest I'm a bit surprised BEA ruled out the relevance of this image/information so quickly and decidedly !? Ruling out information that does not match one's preconceived idea of how thimgs happened is not a good idea in investigations of any kind. And for sure not in the investigation of a still largely unexplained aircraft accident.... Maybe they have further information which allowed them to rule it out for good reason ?! But why not pass that information to the public then ??? |
mm43;
thanks for pointing out the wider range of possibilities. I was just addressing the 'bottom line' of mr. Squair's analysis. So, based on the ACARS messages alone, the ROD in the final seconds could have been anywhere between 2463 and 16320 fpm, while the average ROD in the preceding descent was of the order of 7850 fpm: 35000 (2:10:10) - 2176 (2:14:21). I also believe that the airplane probably stalled one or more times in those final minutes. Is it certain that it was stalled in the final seconds? some juggling of a flight termination time could give a v/s that fits with the BEA reports (high vertical speed, 'en ligne de vol', and 'arm 36 g' etc..). The Turkish 737 in Amsterdam impacted stalled at 3000 fpm, 100 kt, 22 deg. pitch, its fuselage broke into three sections. AF447's stall speed (Vs1g; V_alphamax) was 158 kCAS; 162 kTAS; 274 fps. The corresponding alphamax can be estimated as 14.5 degrees. Interpreting "avec une assiette positive, une faible inclinaison et avec une vitesse verticale importante" as 2.5 degrees nose-up, leaves an FPA of 12 deg. down, or 3418 fpm. So was it stalled? regards, HN39 |
HN39
Just a gut feeling at the moment, but I suspect there is another still higher angle of attack where drag+ lift will balance the aircraft weight in a nearly level attitude. Problem is, no one has published the data for A330 Cd & Cl at ridiculously high angles of attack. You may be able to find data for other type jet transport accidents and get meaningful data since at very high angle of attack the actual shape of the airfoil becomes less important than wing area, aspect ratio, and wing sweep angle. In a 40 degree AOA for example, wing twist factors will likely have minimal impact. If sufficient data from older accidents is not available, I suppose you could use NASA panel codes to come up with meaningful data. Unfortunately I am not sufficiently versed in Aerodynamics to produce a useful result in a useful time frame.:sad: |
Fuel dumping
Just to stop the fuel dumping speculation, Air France A330s are not fitted with a fuel dumping system.
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With great respect for all who post here, allow me to briefly summarize an area that has gotten little credence, perhaps understandably so.
The Industry, like others, is not without elements of other highly competitive and cutthroat endeavours at times. Betrayal is a part of modern commerce as it was in the days of the Silk Road and the Rum, molasses, and slave triangle. Financial? Tech? Airframe? Regulatory Agencies, and investigative Boards? Farming out highly critical aspects of a large and highly visible Investigation is par for the course, but comes with the possibility of failure (s), and inaccuracies. As the "Slick" was dismissed out of hand by BEA without evidence, followed by garbled and nonsensical language("Whether voluntary or not,") The fumbling of the Medical data, conclusions about structural evidence without "substantiating data", and the limitless hypothesizing about a flight path that is without evidence of any kind, What should have been a straightforward discussion of "Smoke on the Water" was ignored, actively, might I say, by the Trustees of Aviation safety, while 20 million was spent trying not to find the aircraft. oily film? bunker fuel dumped by an anonymous ship, Fuel? voluntary or not, which makes no Flight sense. En Ligne de Vol? Useless phrase, impossible to know, and misleading, of course. |
henra wrote:- Any one here knowing/having an idea in which intervals this satellite would take pictures of the same area ? The SAR feature also has a SPOT mode which utilizes doppler/chirp technologies to provide a 1m by 1m resolution. Unfortunately, timely prior requests are required to enable scheduling of this feature over a particular area. As a matter of interest, the French representative organization for the COSMO project were represented on the Drift Group. In 2009 there were 3 COSMO SAR capable satellites in polar sun synchronous orbit. I believe they were in the same orbital plane, equi-phased at 120° apart. mm43 |
Originally Posted by Machinbird
I suspect there is another still higher angle of attack where drag+ lift will balance the aircraft weight in a nearly level attitude.
regards, HN39 PS:: For example, taking the coefficient 1.1 for the resultant force of lift and drag (ignoring thrust); your AoA of 40 deg, and mm43's pitch of 5 deg. NU, would give a rate of descent of 10840 ft/min at 181 kCAS. |
The thing I find interesting about the Cosmo image was it was taken 30 hours after the event before any wreckage had been sighted by the search teams.
Now, understandably that satellite probably downloads thousands of images which there is little point in analysing, but it’s curious this one may have languished on a server until someone had a brainwave and checked it. Wonder when that was. |
HN39 wrote:- I also believe that the airplane probably stalled one or more times in those final minutes. Is it certain that it was stalled in the final seconds? "avec une assiette positive, une faible inclinaison et avec une vitesse verticale importante" BEA Reports provide some indicators that support the stall theory, but whether the descent was marked by a series of stalls and partial recoveries, is like everything we are dealing with, just conjecture. The tail yawing to port on impact provides (imo) a small clue as to how the "positive attitude", "low bank angle" and "vertical speed" were attained, i.e. in a "deep stall" where a clockwise rotation had a stabilizing outcome in the "lost lift" vortex. The ROD from your calculations with 5 degrees nose-up may be interesting. Damage to the Radome showed a significant upward moment, but the horizontal moment at impact failed to shatter the top section. So the GS at impact "en ligne de vol" would appear to be quite low - 60 knots? mm43 |
BackOffice;
At a guess, not until the Drift Group was set up, and those with the appropriate expertise knew where to go "fishing". mm43 |
The 320 ditched in the Hudson at 1500 fpm. Its fuselage received substantial damage but stayed in one piece. |
Drift re-analysed using a simple approach
The Drift Group did their analysis by calibrating their models to things like the drift buoys etc which were drogued relatively shallow compared to a deep ocean but relatively deep when compared to floating debris. If we just take the first 22 bodies (due to their improved consistency relative to other items and not too much time from the impact), calibrate the model to the pollution spot (or slick) and using a method of least squares (Excel) force the curves to go through this point then the potential point of impact extrapolates to 30.51W 2.62N.
(This is achieved by changing time to slick time and using a grid centred on the slick to force the curve through this origin, then converting back from slick time and slick co-ordinates ie using a slick method:ok:). The items in the analysis that appear furthest from the ‘true body line’ (when all items are considered) are the first sightings by the merchant vessel then by the navy. Also the VS recovery position and then (to a lesser extent) its sighting position. The first 2 bodies are also slightly north of the ‘expectation’. These bodies show a spreading out in an ever increasing wide ‘triangle’ (over this180 hours) from the extrapolated impact focal point as they head north which would be expected due to ‘randomness’. There is also a very slight ‘general’ easterly drift. The bodies are found with very little northerly spread (at one time period) but both this northerly and the easterly trends may not be statistically relevant and may simply be the way the retrieval was done considering only 10% of the bodies were recovered. So IMO the slick is statistically relevant and its position is useful. regards. Ian |
FluidFlow:
Wow. Thanks for that work and contribution. mm43: In light of all your incredible and insightful work I'd like very much to hear your comments on Ian's post. grizz |
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