Air France plane missing?

[Leightman]

From several posts it appears the relationship between velocity and acceleration is not always understood......

Velocity is simply how fast something is moving relative to some reference point (i.e. a car travels at 30 mph with respect to the road surface, an aircraft descends at a rate of 30 ft/second relative to the ground)....For AF447 the vertical acceleration at impact would be related to initial vertical velocity at impact and the impact travel distance. ..... 155 Gs (or sufficient to break up an aircraft).

I don't know the posts to which you refer. We have vertical and a horizontal velocity components and I am looking at both via the range of probable descent profiles. From that could come a guestimating of g loads. The horizontal velocity was much higher than the vertical velocity because the plane nearly had to be flying for the size of debris that survived. It doesn't take much vertical velocity at all to break the back of an airliner. AF447 was of course more fragmented than simply a broken back or three, but the pieces that survived don't suggest anything like 155 g's. That many g's combined with the abrasion potential of the forward speed would leave a smear, not big parts. For 447 it appears the forward velocity component lengthened the impact distance, but the vertical acceleration was great enough to break apart the fuselage. Exactly how fragmented we don't exactly know because we aren't familiar with all the debris found. Picking a couple values out of a hat, there could have been a combo of 60 fps of vertical speed and 230 mph, favoring horizontal more than 4 to 1. That would fragment the plane into some small and some large pieces, and the disintegration sequence might be slow enough that the fuselaqe initially (before more abrasion damage occurs) breaks into subsections and spills or ejects contects. If I reverse the velocity components ratio to 1 to 4, as in nose down with a vertical velocity of 230 mph, the debris is mostly all little teensy pieces, with a few big chunks. What do you guess the vertical speed and overall deceleration g's might have been to cause the kind of damage we have seen on 447?

[Leightman]

G's whiz

In the late '50s, before I started driving, my father took the family to see the wreckage of a car where two drinkers managed to dead center the end of a low concrete bridge side, the kind that don't give at all (no, they didn't survive, but they did crack the concrete). I think the tour was supposed to be instructive about what not to do. The speedo was stuck on 110. Both doors had been ripped off, and one was found a quarter mile away. In the case of 447 we are probably looking at at least twice that velocity, and maybe quite a bit more, which may go a long way toward explaining the east-west dispersion of debris and bodies. The Hudson ditching was a smooth deceleration with very little vertical speed. AF447 may have been more like skipping a fragile but heavy stone on a pond.

[Highkeas]

I don't know the posts to which you refer. We have vertical and a horizontal velocity components and I am looking at both via the range of probable descent profiles. From that could come a guestimating of g loads. The horizontal velocity was much higher than the vertical velocity because the plane nearly had to be flying for the size of debris that survived. It doesn't take much vertical velocity at all to break the back of an airliner. AF447 was of course more fragmented than simply a broken back or three, but the pieces that survived don't suggest anything like 155 g's. That many g's combined with the abrasion potential of the forward speed would leave a smear, not big parts. For 447 it appears the forward velocity component lengthened the impact distance, but the vertical acceleration was great enough to break apart the fuselage. Exactly how fragmented we don't exactly know because we aren't familiar with all the debris found. Picking a couple values out of a hat, there could have been a combo of 60 fps of vertical speed and 230 mph, favoring horizontal more than 4 to 1. That would fragment the plane into some small and some large pieces, and the disintegration sequence might be slow enough that the fuselaqe initially (before more abrasion damage occurs) breaks into subsections and spills or ejects contects. If I reverse the velocity components ratio to 1 to 4, as in nose down with a vertical velocity of 230 mph, the debris is mostly all little teensy pieces, with a few big chunks. What do you guess the vertical speed and overall deceleration g's might have been to cause the kind of damage we have seen on 447?

I agree with your message genearlly. If the nose did not dig into the water then longitudinal deceleration forces could be much lower than vertical impact forces. My 155 Gs was intended to show that deceration distance has a big effect on deceleration loads (as indicated by your car/bridge impact post). Somewher I have a report on water impact forces for aerospace vehicles but I can't locate it (it's in a box somewhere in my 130 F temperature garage). I've worked on water impact of air vehicles (including man rated) for many years and know that the water wave height, pitch, and speed also effect impact deceleration together with vertical and horrizontal velocities.
I can believe that the AF447 could break apart in sections just as this 747 did: http://forums.jetphotos.net/showthre...47+crash+cargo

[Leightman]

..... My 155 Gs was intended to show that deceration distance has a big effect on deceleration loads.... (I) know that the water wave height, pitch, and speed also effect impact deceleration together with vertical and horrizontal velocities.

Yes I knew you were making an exaggerated point about the rate of deceleration and should have acknowledged that. Thanks also for bringing up wave height, pitch, and speed. Given the weather at the time that is an issue that should have gotten more attention. But the media idea that the A/C "plunged" (and even some graphic representations as such) has been so strong, and the mere fact that the plane did crash, are such a suggestive combination that the idea of a fairly normal attitude, albeit at higher speed and with a higher sink rate than normal landings, just hasn't been part of the conversation. That combination plus waves could result in the debris we have.

I was hoping the 30' piece found yesterday by a fisherman would be part of 447, but was too far from the debris field and south, so it appears more likely to be booster rocket debris. I haven't seen any mention of that today.

[Gabriel]

I seriously doubt that they were trying to make a controlled ditching. If they had two good engines (as it seems they had) and any minimal degree of control over the plane, they would have tried to reach somewhere rather than ditching in a storm hundreds of miles from the closest trace of civilization or help.

Unless... there was an in-flight fire (from which there is zero evidence so far). In that case, if you think the airplane or yourself are going to be dissabled soon, it is advisable to put the plane down right here right now while you still have control.

So, if it was an uncontrolled ditching with a high descent rate, as it seems it was, the state of the sea would not be a large factor in the final outcome (plane destroyed, everybody died), while I agree it could be significant for the type of debris resulting from the impact.

(Note: I'm not saying that anybody suggested any of the above)

[Spad13]

I seriously doubt that they were trying to make a controlled ditching. If they had two good engines (as it seems they had) and any minimal degree of control over the plane, they would have tried to reach somewhere rather than ditching in a storm hundreds of miles from the closest trace of civilization or help.

Tell Schlossberg.

[Leightman]

I seriously doubt that they were trying to make a controlled ditching. If they had two good engines (as it seems they had) and any minimal degree of control over the plane, they would have tried to reach somewhere....So, if it was an uncontrolled ditching ....the state of the sea would not be a large factor in the final outcome (plane destroyed, everybody died), while I agree it could be significant for the type of debris resulting from the impact.

I agree with what you are saying, that the best outcome would always be the pilots' choice. And also agree that IF there was a high vertical descent rate, the state of the sea would not be very important. Maintain control and altitude, if not then maintain control, if not then maintain spatial orientation, avoid impacting the surface, avoid impacting the surface at an unsurvivable angle, in that order. Presuming the plane impacted nose-up, it was either because it just happened to be at that attitude at the instant of impact, or because the pilots had placed it into that attitude, if even only temporarily, as in a pullout from a dive begun at too low an altitude. AF447 lost 35000' of altitude in about 4.5 minutes so it either had to have its nose pointed down for most of that 4.5 minutes, or be in some state of stall (fairly level attitude, but high vertical descent).

There are a lot of causes that have not been ruled out at this point: full or partial incapacitation of the crew, bird strikes on the pitots (yes don't bother), alien interference or midair, midair with a drug runner, mouse in the works, anaconda in the overhead, coffee on the console, space junk, sabotage, meteor, suicide, some arcane airframe, computer, or electrical failure. The causes vary from possible to pretty slim. Compared to all of them, temporary loss of flight data, a gradual loss of control, a departure from controlled flight, and a attempted regaining of control fits the scenario and evidence as well as anything and better then most.

Nothing new on the Guyanan fisherman.

[Highkeas]

............ the idea of a fairly normal attitude, albeit at higher speed and with a higher sink rate than normal landings, just hasn't been part of the conversation. That combination plus waves could result in the debris we have.
.......................

To get an idea of what an out-of-envelope fwd and vertical landing speed can do to an aircraft debris dispersion look at Figure 6 of this report where the aircfat fuselage broke into three sections (plus it lost its vertical stabilizer):
http://libraryonline.erau.edu/online-full-text/ntsb/aircraft-accident-reports/AAR90-06.pdf
Although this crash landing was on solid ground similar forces would be prevalent landing on water.

[scottkin]

tell schlossberg.

lmao!!!

[Leightman]

Thanks for the 232 link Highkeas. I want to note that 232 touchdown to farthest debris was about 3500-4000', and that in the last 20 seconds airspeed averaged 215 KIS and the sink rate was 1620 fpm or 27 fps. That is a horizontal to vertical ration of about 13:1. After initial impact no part of the aircraft lost contact with the ground. There is a strong asumption that AF447 (or any sections of it save perhaps the vertical stab) similarly never lost contact with the sea, particularly given the apparently much higher sink rate. On the theory that just about anything will "fly" if going fast enough, I would be interested to know if anyone thinks the combination of a higher sink rate--say 3000 or 4000fpm--in conjunction with a higher forward speed--say 300 kts--would allow any possibility at all that a portion of the plane or its contents could have gone airborne some distance again after the inital impact.

Relative to that possibility, I am simultaneously hypothesizing another possibility--that the aft fuselage broke off first and impacted heavily, but that the center fuselage section then broke off angling "up" relative to the aft section; and that the nose section broke off due to the bending moment along the fuselage, with the nose angling down. In other words in the instants just after tail impact, the aft fuselage was at, say, at 20 degree AOA, the forward end of the center fuselage section was rotating upward and therefore at a 30 degree AOA and increasing, and the nose tip was angline downward, say at a 15 deg AOA. It helps to visualize this instant by instant as a series of independent breaks. If this were possible given some unique combination of AOA, forward, and vertical speeds, then the fuselage sections might have spent more time in the air than the tail. The purpose would be to explain debris dispersion and help predict whether and how much the airframe sections were seperated. This also supports the idea that the area where the FDR was located suffered a lot of damage, perhaps to the FDR too.

If the aircraft simply smacked the sea once, then the previous paragraph is obviously not accurate. But I do want to address the prevalent assumption that impact was just a one time affair.

[Gabriel]

If the aircraft simply smacked the sea once, then the previous paragraph is obviously not accurate. But I do want to address the prevalent assumption that impact was just a one time affair.

Some around here are speculating that the distribution of the debris can be related to the way the plane and its parts "bounced" at impact.

Let's exagerate a bit with the folowing scenario:

Vertical speed at impact: 10,000 fpm
Horizontal speed at impact: 300kts
The total plane's speed would be the vectorial sum of both components, but it's not needed for what I'm doing.

Some debris hit the water and just stay there, they don't move one inch beyond the point of impact (infinite desceleration).

Some other debris "bounce" with restitution coefficient 1 (a perfect bounce).
With that the horizontal speed of those debris after the impact will remain at 300kts, while the vertical speed will "reverse" to 10,000 fpm up.

The "bouncing" debris then fly at free fall, neglecting any effect from the air (that means that a chunk of aluminium at 300+ kts doesn't makes any drag).

Do you agree that that's a lot of exageration, and that any debris that bounce after the initial impact would not fly anythig comparable with this scenario? And that no debris would just skim the watter and stop in no distance?

Well, even in this highly unrealistic scenario the maximum distance between debris remains below 1 NM. That hardly helps explain the 40NM+ distance that they were found. Obviously, the scattering of the debris is the result of the winds and currents, and the way the plane broke up is insignificant, unless....

Unless the plane did not hit the water in one piece, but broke up in flight in 2 or 3 large parts that crashed at some distance one from the other, and what we see now is the superposition of 2 or 3 debris fields after the winds and current scattered them and mixed their boundaries. I have no reason to think that this is what happened.

[Leightman]

Some around here are speculating that the distribution of the debris can be related to the way the plane and its parts "bounced" at impact.
... I have no reason to think that this is what happened.

If "some" around here have been speculating, I'd like to know who the other one was....

Thank you Gabriel. It may not seem so, but that was exactly what I was looking for because it sets an outer limit on a credible estimation. Even using an exaggerated scenario it's hard to get a bounced or skipped impact debris spread of over one NM. As you note (without conclusion) that's a big problem for the plane-intact-at-impact concept because the June 6 east-west spread is so large.

Exactly why the BEA interim report concluded the plane was intact when it impacted was not spelled out, but it appears to be assumption due to the evidence of compressive deformation. An intact impact could be easily and quickly confirmed if multiple items from both ends of the aircraft were discovered 40 km apart from another such set on the same day. Or if debris were found from both ends of the A/C that showed the same kind and amount of compressive deformation. But the interim report did not specify that the compression was uniform.

The east west spread of bodies (which are not as prone to wind drift) is only about 20% of the E-W spread of all other debris. With a single exception, all bodies recovered June 6 through June 10 were found in an E-W corridor only 15-20 km wide (E-W) but spread over about 175 km along the N-S axis. The single exception was found June 8 about 25 km from the N-S centerline of all the bodies, or about 20 km east of the other two bodies found (close together) the same day. (That is quite a large variance to be consistent with a single crash site.)

Wind seems an insufficient reason for the June 6 40 km spread because even though five days had elapsed since the crash, it seems unlikely that winds would blow opposite directions in a small area consistently enough for very much drift to accumulate both E and W.

I think further progress on the flight path of the last several thousand feet of descent and impact of 447 via a public forum will be unlikely unless a more accurate debris map becomes available. There are competing and equally possible scenarios. We would need a day by day debris map with an ID on the location in the A/C and damage report for each piece. The investigators will get that, but I don't think we will.

[NewGuy]

Happy to find this blog

Off and on for the past couple of days I have been catching up on the many insightful posts in this blog. It took me some time to find it. I don't know if it's the only one of its kind but I am glad to find a community of people with aviation expertise who have scoured the available facts and continue to question the official interim report of AF447, because as an otherwise educated layperson with little specific expertise in issues of aviation, the preliminary report made absolutely no sense to me. The distribution of the wreckage and the bodies found only a few days after the crash seems impossible to reconcile with an intact airplane hitting the water. At some point during the descent there must have been an aircraft disintegration into a number of pieces, it seems to me.

There are five issues on which I would welcome thoughts from this group because it doesn't seem that any answers are available or forthcoming anywhere else, and in the absence of the black boxes the rest of the world has moved on to other issues substantive (revolution in Iran) and trivial (forty days of mourning for Michael Jackson).

One is whether it can be completely ruled out that the tail fin didn't rip off in the air due to the extreme turbulence (like with the American Airlines flight of November 2001). I understand that the theory is that the evidence shows that the tail fin ripped off in a motion that was "forward and slightly to the left" which suggests coming off due to inertia when the plane hit the water and stopped suddenly, but if the plane was malfunctioning and the rudder was perhaps swinging wildly, couldn't the wind forces likewise have torn the tail fin off in a motion that was ultimately "forward and slightly to the left"?

The second is that I'm not convinced that the evidence of pancaking (bowlegged galley carts, etc.) rules out a breakup of the aircraft at altitude. It seems at least possible that one or more chunks of the aircraft which broke up at altitude eventually hit the water in a position which would create the same pancaking forces as if the whole aircraft were intact.

The third is that I don't understand why the pilots, if they were still in command of a wounded aircraft and trying to replicate the miracle on the Hudson, didn't at least squeeze out some sort of mayday distress call or signal so that rescuers would know where to look. No distress call at all also suggests to me as a layperson that whatever happened immediately incapacitated and quickly killed everyone on board -- this is also consistent with disintegration at altitude as well as the reported fact that the victims "didn't drown."

Fourth, in the first days after the accident there was a lot of attention given to the pitot tubes on Airbus aircraft. What about Boeing aircraft? Do Boeing aircraft also use pitot tubes, or do Boeing aircraft employ some other system for measuring speed?

Fifth, what if any official dissent has there been towards the interim report? I have followed these issues fairly closely and unless I missed something I haven't seen a single public figure or significant organization come out and say that the interim report leaves quite a great deal to be desired, which the other posts on this blog clearly demonstrate.

--NewGuy
Los Angeles, CA

[swissair]

Thank you NewGuy

Off and on for the past couple of days I have been catching up on the many insightful posts in this blog. It took me some time to find it. I don't know if it's the only one of its kind but I am glad to find a community of people with aviation expertise who have scoured the available facts and continue to question the official interim report of AF447, because as an otherwise educated layperson with little specific expertise in issues of aviation, the preliminary report made absolutely no sense to me. The distribution of the wreckage and the bodies found only a few days after the crash seems impossible to reconcile with an intact airplane hitting the water. At some point during the descent there must have been an aircraft disintegration into a number of pieces, it seems to me.

There are five issues on which I would welcome thoughts from this group because it doesn't seem that any answers are available or forthcoming anywhere else, and in the absence of the black boxes the rest of the world has moved on to other issues substantive (revolution in Iran) and trivial (forty days of mourning for Michael Jackson).

One is whether it can be completely ruled out that the tail fin didn't rip off in the air due to the extreme turbulence (like with the American Airlines flight of November 2001). I understand that the theory is that the evidence shows that the tail fin ripped off in a motion that was "forward and slightly to the left" which suggests coming off due to inertia when the plane hit the water and stopped suddenly, but if the plane was malfunctioning and the rudder was perhaps swinging wildly, couldn't the wind forces likewise have torn the tail fin off in a motion that was ultimately "forward and slightly to the left"?

The second is that I'm not convinced that the evidence of pancaking (bowlegged galley carts, etc.) rules out a breakup of the aircraft at altitude. It seems at least possible that one or more chunks of the aircraft which broke up at altitude eventually hit the water in a position which would create the same pancaking forces as if the whole aircraft were intact.

The third is that I don't understand why the pilots, if they were still in command of a wounded aircraft and trying to replicate the miracle on the Hudson, didn't at least squeeze out some sort of mayday distress call or signal so that rescuers would know where to look. No distress call at all also suggests to me as a layperson that whatever happened immediately incapacitated and quickly killed everyone on board -- this is also consistent with disintegration at altitude as well as the reported fact that the victims "didn't drown."

Fourth, in the first days after the accident there was a lot of attention given to the pitot tubes on Airbus aircraft. What about Boeing aircraft? Do Boeing aircraft also use pitot tubes, or do Boeing aircraft employ some other system for measuring speed?

Fifth, what if any official dissent has there been towards the interim report? I have followed these issues fairly closely and unless I missed something I haven't seen a single public figure or significant organization come out and say that the interim report leaves quite a great deal to be desired, which the other posts on this blog clearly demonstrate.

--NewGuy
Los Angeles, CA

I think a bit like you in your direction and question a lot the same way. It is my opinion that this aircraft fell victim to a sudden brutal event and, yes, I do also have the opinion that it most probably fell apart at altitude. Lastly, some posts suggested that there we no traces of fire or explosives, But then, hey, they only recovered 2 to 3% of the Airbus. Food for thought.

[CockpitCat]

No distress call at all also suggests to me as a layperson that whatever happened immediately incapacitated and quickly killed everyone on board -- this is also consistent with disintegration at altitude as well as the reported fact that the victims "didn't drown."

Some have suggested that no (HF) distress call was received due to the electrical storm. The storm would only have affected HF reception on AF447, transmissions from AF447 should have been unaffected. Also, surely satellite comms could also have been used by the pilots? Plus, there were probably some creditcard satphones in the cabin, which pax could have used if they were able to...

The BEA report does not seem to indicate where on the A330 the recovered debris (and pax) were located, probably because the Brazilians have not handed over the recovered debris to the BEA personnel by the time the report was compiled...this should give an indication whether the recovered debris and pax were confined to a specific part of the a/c or not.