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Acceleration
I have seen the value 36g mentioned as the acceleration on impact. I think this mat be based on a misunderstanding of a text in one of the photos in the accident reports. I have assumed that "36g" in a red ring i a kind of part number only. Please check.
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Diversification;
The BEA have used 36g to describe the Rudder Vertical Load Arm fracture point. The relevant text from Interim Report #2 states:-
Clearly, it is an unfortunate use of "36g" as a name, but the text is quite clear on how the acceleration of 36g was derived, i.e.the the vertical movement between the V/S, along the hinge axis, and the Rudder had an acceleration of 36 times the force of gravity at the fail point.
EDIT
Well, having made a fool of myself in misinterpreting the BEA's statement above, I decided to go and get an independent translation by a person born in the UK, educated both there and in France, and who has lived in France for over 40 years. Their translation of the offending sentence. i.e.
finishes up using succinct English words in place of the arrays often used in French, and the result is:-
The ambiguity has been nicely removed.
mm43
The BEA have used 36g to describe the Rudder Vertical Load Arm fracture point. The relevant text from Interim Report #2 states:-
1.12.3.5.4 Examination of the vertical stabiliser – rudder attachments
The vertical load pick-up arm in the rudder’s hinge axis (arm 36 g) broke at the
level of the attachment lug on the rudder side.
The size of this arm is calculated to withstand a maximum load of 120,000 N, corresponding to a relative acceleration of 36 g of the rudder in relation to the vertical stabilizer.
The vertical load pick-up arm in the rudder’s hinge axis (arm 36 g) broke at the
level of the attachment lug on the rudder side.
The size of this arm is calculated to withstand a maximum load of 120,000 N, corresponding to a relative acceleration of 36 g of the rudder in relation to the vertical stabilizer.
EDIT
Well, having made a fool of myself in misinterpreting the BEA's statement above, I decided to go and get an independent translation by a person born in the UK, educated both there and in France, and who has lived in France for over 40 years. Their translation of the offending sentence. i.e.
The size of this arm is calculated to withstand a maximum load of 120,000 N,
corresponding to a relative acceleration of 36 g of the rudder in relation to the
vertical stabilizer.
corresponding to a relative acceleration of 36 g of the rudder in relation to the
vertical stabilizer.
Ce bras est dimensionné par calcul pour résister à un effort maximal d’environ 120 000 N, correspondant à une accélération relative de 36 g de la gouverne de direction par rapport à la dérive.
'Arm 36 g' is designed to withstand a maximum load of 120,000 N, corresponding to a relative acceleration of the arm by the rudder in relation to the vertical stabilizer.
'Arm 36 g' is designed to withstand a maximum load of 120,000 N, corresponding to a relative acceleration of the arm by the rudder in relation to the vertical stabilizer.
mm43
Last edited by mm43; 8th Mar 2010 at 03:06.
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mm43
The vertical movement of the Rudder is not "upwards and downwards". Here, "vertical" refers to the sweep of the Rudder (Loading) as a vector 90 degrees to the Vertical Stabiliser measured spanwise. The "designed for" load is "sideways". ("vertical") Hold a model of the a/c level, then roll it 90 degrees. As the Rudder articulates "up and down", this is your "vertical". (relative to the VS.)
This is why the member is called an "arm"; the two arms support the pivot hinge of the Rudder, but their purpose is to transfer pivot stress outboard of the axis of the Rudder Pin into the aft vertical spar of the VS.
They work "independently" of eachother, as the rudder expresses side loading alternately as a compression or a tension.
The failure of R36g is in tension, evidenced by the "breaking off" of the tip of the thru-bolt mount. This is indicative therefore of an unsustainable load while the Rudder is deflected to the Right, Starboard side of the a/c centerline. If intentional, it would be evidence of an attempt to mitigate left Yaw.
I'm in no position to critique the esteemed engineers of the aircraft, but I have at least two questions.
Is there not a "saddle" washer between the Pin/Tube and the load face of the thru-bolt/arm? I would expect one, since to load a flat arm to a round tube without spreading the point stress would not be a good thing.
Finally, and this thus far only applicable to the AB300-AA587:
Has the designer of the Rudder been apprehended? Likewise the VS team members? What about the "fusion" team?
The Rudder loaded the VS to its catastrophic breaking point, and the Rudder remained attached to depart the VS after the VS/Rudder system was torn away. Forget the F/O and his alleged "bicycling". Had the Rudder failed and torn away, they would have landed almost certainly. Plenty of time to lease a flat bed Truck and retrieve the Rudder from the Orphanage.
I would only repeat, an aircraft can fly reasonably well with no Rudder at all, it is after all, only a "trimming" device. Without a VS, it will not fly.
At all.
What's wrong with a picture of a Rudder attached to a Vertical Stabilizer, but the Vertical Stabilizer is unattached to the Aircraft?
Fatal or no, Hull loss or no, procuring cause of the Accident or no?
It cannot be ruled out that the VS separated after the a/c's impact with the Sea. However, it is too pristine to have occurred that way, imo.
Was it thrown clear (completely) then? Because if it was floating with other debris, to include heavier parts that subsequently sank, there is no abrasion, dimples or punctures, and in a rough sea (!) at that.
In the scheme of things, 36g acceleration is not much at all. Lap belts are stressed to perform through 40g's, since stronger than that, people are sliced in two, and it becomes a moot specification. (sorry to be blunt).
At 36 g's the crew rest capsule, the galley, and the lav door would be accordioned to the size of a briefcase, imo. These structures are simply not built to withstand crushing, twisting, or frankly, to support their own (unattached) weight.
The VS. If I was a responsible party in this tragic accident, and the VS was found unattached but especially with the Rudder yet attached, I would pray for the conclusion of "lost at impact". For if it failed prior to, I would consider it a suspicious thing, perhaps related to the outcome. I certainly wouldn't say the a/c landed "En ligne de Vol" and intact. The two must be sustainable in the evidence.
bear
The vertical movement of the Rudder is not "upwards and downwards". Here, "vertical" refers to the sweep of the Rudder (Loading) as a vector 90 degrees to the Vertical Stabiliser measured spanwise. The "designed for" load is "sideways". ("vertical") Hold a model of the a/c level, then roll it 90 degrees. As the Rudder articulates "up and down", this is your "vertical". (relative to the VS.)
This is why the member is called an "arm"; the two arms support the pivot hinge of the Rudder, but their purpose is to transfer pivot stress outboard of the axis of the Rudder Pin into the aft vertical spar of the VS.
They work "independently" of eachother, as the rudder expresses side loading alternately as a compression or a tension.
The failure of R36g is in tension, evidenced by the "breaking off" of the tip of the thru-bolt mount. This is indicative therefore of an unsustainable load while the Rudder is deflected to the Right, Starboard side of the a/c centerline. If intentional, it would be evidence of an attempt to mitigate left Yaw.
I'm in no position to critique the esteemed engineers of the aircraft, but I have at least two questions.
Is there not a "saddle" washer between the Pin/Tube and the load face of the thru-bolt/arm? I would expect one, since to load a flat arm to a round tube without spreading the point stress would not be a good thing.
Finally, and this thus far only applicable to the AB300-AA587:
Has the designer of the Rudder been apprehended? Likewise the VS team members? What about the "fusion" team?
The Rudder loaded the VS to its catastrophic breaking point, and the Rudder remained attached to depart the VS after the VS/Rudder system was torn away. Forget the F/O and his alleged "bicycling". Had the Rudder failed and torn away, they would have landed almost certainly. Plenty of time to lease a flat bed Truck and retrieve the Rudder from the Orphanage.
I would only repeat, an aircraft can fly reasonably well with no Rudder at all, it is after all, only a "trimming" device. Without a VS, it will not fly.
At all.
What's wrong with a picture of a Rudder attached to a Vertical Stabilizer, but the Vertical Stabilizer is unattached to the Aircraft?
Fatal or no, Hull loss or no, procuring cause of the Accident or no?
It cannot be ruled out that the VS separated after the a/c's impact with the Sea. However, it is too pristine to have occurred that way, imo.
Was it thrown clear (completely) then? Because if it was floating with other debris, to include heavier parts that subsequently sank, there is no abrasion, dimples or punctures, and in a rough sea (!) at that.
In the scheme of things, 36g acceleration is not much at all. Lap belts are stressed to perform through 40g's, since stronger than that, people are sliced in two, and it becomes a moot specification. (sorry to be blunt).
At 36 g's the crew rest capsule, the galley, and the lav door would be accordioned to the size of a briefcase, imo. These structures are simply not built to withstand crushing, twisting, or frankly, to support their own (unattached) weight.
The VS. If I was a responsible party in this tragic accident, and the VS was found unattached but especially with the Rudder yet attached, I would pray for the conclusion of "lost at impact". For if it failed prior to, I would consider it a suspicious thing, perhaps related to the outcome. I certainly wouldn't say the a/c landed "En ligne de Vol" and intact. The two must be sustainable in the evidence.
bear
Last edited by bearfoil; 5th Mar 2010 at 00:07.
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LN-PAA
I once lost a friend who was pilot in command on LN-PAA when they lost the fin and rudder over the sea between Norway and Denmark. According to the accident analysis the aircraft then behaved in a quite unusual fashion, e.g making at least one roll which the pilots recovered from (according to the mechanical FDR) before losing control again and spinning into the sea. Wikipedia has part of the story, but to get the whole correct (and awful) picture you have to read the full accident report (in norwegian).
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Yes CJ. Here is the link. 1993/03 | sht
Bear: I am now retired, but spent much of my life on research regarding nuclear reactor safety. I am also still trying to learn lessons from aviation accidents.
I chose my name to remind everyone of the importance to have diversification and not only replication in parallel safety critical systems.
Bear: I am now retired, but spent much of my life on research regarding nuclear reactor safety. I am also still trying to learn lessons from aviation accidents.
I chose my name to remind everyone of the importance to have diversification and not only replication in parallel safety critical systems.
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Bearfoil
I now agree with your above reasoning. The description provided by the BEA must have lost its meaning in translation.
I did some numbers around the 120000 newtons and they didn't compute, no 36g to be found there.
mm43
The vertical movement of the Rudder is not "upwards and downwards". Here, "vertical" refers to the sweep of the Rudder (Loading) as a vector 90 degrees to the Vertical Stabiliser measured spanwise. The "designed for" load is "sideways". ("vertical") Hold a model of the a/c level, then roll it 90 degrees. As the Rudder articulates "up and down", this is your "vertical". (relative to the VS.)
I did some numbers around the 120000 newtons and they didn't compute, no 36g to be found there.
mm43
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I do have other theories. One involves the tail strike @ ~100knots but in additive to horizontal, perhaps the same 100 knots. The VS keeps descending (!) as the tail stops, and pierces, extends into, the HS, where the lower corner of the Rudder is trapped between longerons (not for long) as the assembly "rebounds" (?) the Fuse keeps the skin, strips off the filleting and fairing as the VS ends up rotating slightly backwards, free and clear of the debris field.
Or, without ASI, no RTLU, and a sinister Ruddering as the pilot tries to correct for the last Yaw by increasing the next one, with Power and Pitch screaming at his skilled Brain, and loss, gain of thrust in asymmetric result, the VS and Rudder are torn away. We know how robustly the Rudder is designed and built, we see the "Failure" which isn't actually a failure. The VS? We see destroyed "Hoops". What is a Hoop? I have no idea.
bear
Or, without ASI, no RTLU, and a sinister Ruddering as the pilot tries to correct for the last Yaw by increasing the next one, with Power and Pitch screaming at his skilled Brain, and loss, gain of thrust in asymmetric result, the VS and Rudder are torn away. We know how robustly the Rudder is designed and built, we see the "Failure" which isn't actually a failure. The VS? We see destroyed "Hoops". What is a Hoop? I have no idea.
bear
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Bearfoil, it's time for another thought experiment.
Note that at a typical falling object's terminal velocity, about120 MPH, hitting water is pretty close to hitting a farmer's field. Both are effectively a solid immovable object. The land and the water cannot get out of the way of the moving object fast enough to appear materially different from a perfect solid.
With that in mind hitting the water at a small angle with a mostly downward and somewhat forward velocity vector with a small rotational component about at least the plane's Z axis. Mostly downwards and "typical terminal velocity" means the plane does not so much cut the water as it flattens out on the water.
I'm not sure if that's what you meant by the flat plate. A pure flat plate will behave much like a playing card in a hurricane. (grin - feel free to experiment {^_-}) It's not likely to land flat. A plane's configuration, on the other paw, seems to make a more or less flat encounter with a surface far enough below one of the two stable states, as I understand it. Pure nose down may be stable or merely meta-stable. I don't know. It works for bombs, though. But they don't have wings designed to make the bombs (metaphorically speaking) want to fly. Planes do. So for a plane the horizontal plane is one of its most likely orientations, even when falling. Graybeard posted an excellent example, lost plane, punch out, followed by a long flat furrow in a farmer's field and an F-106 that flew again.
So as I see it I am not boggled at the plane hitting nearly flat despite all the WW-II spin videos out there on the web. Nor am I boggled by the concept that it was not spinning at all fast. The VS is still there to prevent a rapid spin. But, for one reason or another the plane lost enough forward velocity that it lost engines (at least for a minute or so). That could lead to a sink out of which they had no escape. Or, the transmission gap may mean no engines, recover, too low, plane encounters water and it's all over. (I suspect that if they were conscious the pilots did not see the water until it was thoroughly too late - dark, stormy, rain, ground? What ground?
Note that at a typical falling object's terminal velocity, about120 MPH, hitting water is pretty close to hitting a farmer's field. Both are effectively a solid immovable object. The land and the water cannot get out of the way of the moving object fast enough to appear materially different from a perfect solid.
With that in mind hitting the water at a small angle with a mostly downward and somewhat forward velocity vector with a small rotational component about at least the plane's Z axis. Mostly downwards and "typical terminal velocity" means the plane does not so much cut the water as it flattens out on the water.
I'm not sure if that's what you meant by the flat plate. A pure flat plate will behave much like a playing card in a hurricane. (grin - feel free to experiment {^_-}) It's not likely to land flat. A plane's configuration, on the other paw, seems to make a more or less flat encounter with a surface far enough below one of the two stable states, as I understand it. Pure nose down may be stable or merely meta-stable. I don't know. It works for bombs, though. But they don't have wings designed to make the bombs (metaphorically speaking) want to fly. Planes do. So for a plane the horizontal plane is one of its most likely orientations, even when falling. Graybeard posted an excellent example, lost plane, punch out, followed by a long flat furrow in a farmer's field and an F-106 that flew again.
So as I see it I am not boggled at the plane hitting nearly flat despite all the WW-II spin videos out there on the web. Nor am I boggled by the concept that it was not spinning at all fast. The VS is still there to prevent a rapid spin. But, for one reason or another the plane lost enough forward velocity that it lost engines (at least for a minute or so). That could lead to a sink out of which they had no escape. Or, the transmission gap may mean no engines, recover, too low, plane encounters water and it's all over. (I suspect that if they were conscious the pilots did not see the water until it was thoroughly too late - dark, stormy, rain, ground? What ground?
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Bearfoil, "At 36 g's the crew rest capsule, the galley, and the lav door would be accordioned to the size of a briefcase, imo. These structures are simply not built to withstand crushing, twisting, or frankly, to support their own (unattached) weight."
Would it? Or would it merely fracture in every weak place in the structures? That largely depends on how much energy was dissipated in the structures, that would be conditional on both the acceleration and the duration of the acceleration.
I've been envisioning a short sharp (36g +/-?) slap and it's over. I get the impression you see a sustained 36g. If it was sustained the plane would have reached the Moon on the rebound. (exaggerating for effect, of course.) That is a good argument for a low speed along its velocity vector when it hit. Even at 120 MPH we're talking a fraction of a second to bring the portions of the plane that took the most acceleration to a halt. So the trash compactor effect doesn't have time to kick in.
As I muse on it this may be another argument for the tail slapping in first. The belly may have come down with less acceleration. The report, here, of bodies sliced in two by seat belts belies this idea, though.
Would it? Or would it merely fracture in every weak place in the structures? That largely depends on how much energy was dissipated in the structures, that would be conditional on both the acceleration and the duration of the acceleration.
I've been envisioning a short sharp (36g +/-?) slap and it's over. I get the impression you see a sustained 36g. If it was sustained the plane would have reached the Moon on the rebound. (exaggerating for effect, of course.) That is a good argument for a low speed along its velocity vector when it hit. Even at 120 MPH we're talking a fraction of a second to bring the portions of the plane that took the most acceleration to a halt. So the trash compactor effect doesn't have time to kick in.
As I muse on it this may be another argument for the tail slapping in first. The belly may have come down with less acceleration. The report, here, of bodies sliced in two by seat belts belies this idea, though.
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Bearfoil, "What is a Hoop?"
That's a good question. There's probably a nice technical term for the fool tabs, hoops, whatever. At each fastening point for the VS there are U shaped piece attached at the bottom of the U to the spar. The VS has a hoop, or tab, that fits in between the legs of the U. A honking big "pin" goes through all three pieces when the VS is installed to the plane. SOMEWHERE in that old thread there is a fine picture of the assembly process that might clear up this question. If its poster still has it reposting it here might be a good idea, moderators permitting.
I hope the description helps. That also explains why I built the index card experiment the way I did.
That's a good question. There's probably a nice technical term for the fool tabs, hoops, whatever. At each fastening point for the VS there are U shaped piece attached at the bottom of the U to the spar. The VS has a hoop, or tab, that fits in between the legs of the U. A honking big "pin" goes through all three pieces when the VS is installed to the plane. SOMEWHERE in that old thread there is a fine picture of the assembly process that might clear up this question. If its poster still has it reposting it here might be a good idea, moderators permitting.
I hope the description helps. That also explains why I built the index card experiment the way I did.
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Now there is a spirited homily. Flat, slowly rotating aspect, check.
100knots vertical? Check.
The galley looks like one I saw that had fallen off a loading dock. The tray cabinet had trays and shelving piled up at the bottom, and was teetering on one leg. These are damages created by stoned ramp rats, not interior fixtures pinned in a Very fragile Aluminum tube that splats on concrete at high velocity. I ask you, honestly, you believe these fixtures were salvaged but the intact airframe was utterly destroyed?
These are not consistent results. They demand too high a suspension of disbelief.
Building an a/c, one has pretty much three solid walls.
Strong, Light, and Cheap. The "Cheap" is of a higher value than pants at Tesco's, but it is nonetheless a ruthless master.
The fixtures, imo, did not reach the Sea with the a/c, They had been ejected, with far more precious Cargo, at higher altitudes. Light, strong, and cheap, they essentially floated down. Big, flat, light structures falling into the sea. Reasonably undamaged, along with the VS.
The crew rest capsule the same. This is difficult, for we assume it was holding the Captain, and perhaps one or two rest FA's. How did it come to be found?
The Sea tore the Fuselage into bits, but somehow the ridiculously underbuilt capsule escaped with a crushed floor only? If the Fuselage basically landed on top of the capsule (after the Belly had 'stopped'), well, there is an amazing piece of work.
The fuselage is a wonderful structure, as a whole it is remarkably strong torsionally, and is a robust pressure vessel. It is not resistant to bending, to bearing, or haphazardly allocated weight, pressure, puncture, etc.
Is this a fiction? I cannot say, I will tell you this is a puzzle. Reading and rereading the other accounts of unreliable air speed and recovery therefrom, This accident seems to have started with a train of prior and even multiple repetitions of very bad airplane behaviour.
Given the struggles confronting prior crews, and the conditions on the First of June last, the simple position is to presume upset, and that due to any of several results possible with loss of critical instrumentation.
bear
JD- Thanks. "What is a Hoop?" Rhetorical question. "tongue in cheek".
100knots vertical? Check.
The galley looks like one I saw that had fallen off a loading dock. The tray cabinet had trays and shelving piled up at the bottom, and was teetering on one leg. These are damages created by stoned ramp rats, not interior fixtures pinned in a Very fragile Aluminum tube that splats on concrete at high velocity. I ask you, honestly, you believe these fixtures were salvaged but the intact airframe was utterly destroyed?
These are not consistent results. They demand too high a suspension of disbelief.
Building an a/c, one has pretty much three solid walls.
Strong, Light, and Cheap. The "Cheap" is of a higher value than pants at Tesco's, but it is nonetheless a ruthless master.
The fixtures, imo, did not reach the Sea with the a/c, They had been ejected, with far more precious Cargo, at higher altitudes. Light, strong, and cheap, they essentially floated down. Big, flat, light structures falling into the sea. Reasonably undamaged, along with the VS.
The crew rest capsule the same. This is difficult, for we assume it was holding the Captain, and perhaps one or two rest FA's. How did it come to be found?
The Sea tore the Fuselage into bits, but somehow the ridiculously underbuilt capsule escaped with a crushed floor only? If the Fuselage basically landed on top of the capsule (after the Belly had 'stopped'), well, there is an amazing piece of work.
The fuselage is a wonderful structure, as a whole it is remarkably strong torsionally, and is a robust pressure vessel. It is not resistant to bending, to bearing, or haphazardly allocated weight, pressure, puncture, etc.
Is this a fiction? I cannot say, I will tell you this is a puzzle. Reading and rereading the other accounts of unreliable air speed and recovery therefrom, This accident seems to have started with a train of prior and even multiple repetitions of very bad airplane behaviour.
Given the struggles confronting prior crews, and the conditions on the First of June last, the simple position is to presume upset, and that due to any of several results possible with loss of critical instrumentation.
bear
JD- Thanks. "What is a Hoop?" Rhetorical question. "tongue in cheek".
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Perhaps it's a misperception on my part to view the fuselage as a composite structure rather than an aluminum tube. I was envisioning the fuselage taking the most damage and fracturing rather than tearing or bending like the more traditional aluminum tube structure. This possible misperception on my part was reinforced by discussions of possible lightning damage some time ago. For an aluminum tube that's not much of a problem. The currents travel in the skin. I'm still not sure how a composite aircraft protects its relatively delicate electronics when there is a lightning strike to the aircraft.
So for the record perhaps determining if the fuselage and pressure vessel were composite or metal would be a good point. They fail quite differently. (The VS joints were quite plainly composite structures based on what they looked like in failure.)
(I also note that the half second or so for a 36g deceleration means that envisioning the tail cone being flexed upwards applying more forces to the joints than they could handle is not as robust a concept as it should be. What DID make the VS break away with tears that look like it was pulled mostly upward and forward? Maybe it hit the ocean rather slowly, tail cone bent up, VS was "pinched off", and the sudden drag of the water pivoted the plane down into its belly flop. The composites ripped, fractured, and mostly sank. That will require finding enough critical pieces to reassemble. And it tells us nothing about the proximate cause of the disaster. It's the first 3 or 4 minutes of this disaster that are important, not the last few seconds.)
Boy howdy I can understand the problems the BEA is having trying to come up with theories. Nothing fits together neatly. Key puzzle pieces are simply not there.
So for the record perhaps determining if the fuselage and pressure vessel were composite or metal would be a good point. They fail quite differently. (The VS joints were quite plainly composite structures based on what they looked like in failure.)
(I also note that the half second or so for a 36g deceleration means that envisioning the tail cone being flexed upwards applying more forces to the joints than they could handle is not as robust a concept as it should be. What DID make the VS break away with tears that look like it was pulled mostly upward and forward? Maybe it hit the ocean rather slowly, tail cone bent up, VS was "pinched off", and the sudden drag of the water pivoted the plane down into its belly flop. The composites ripped, fractured, and mostly sank. That will require finding enough critical pieces to reassemble. And it tells us nothing about the proximate cause of the disaster. It's the first 3 or 4 minutes of this disaster that are important, not the last few seconds.)
Boy howdy I can understand the problems the BEA is having trying to come up with theories. Nothing fits together neatly. Key puzzle pieces are simply not there.
JD-EE;
Photo of AA587, "top of the hoop" if I have that right, with the ears and the place for the pins. The BEA Report also has a good cross-section showing the hoop, again, if I have that right.
bearfoil;
Very difficult.
The structure found is the Cabin Crew Rest Module. It is in the belly of the a/c, mid-section and sleeps about six if I recall depending upon the installation. Some F/A's would have been on break as 3+hrs in, the first service would be finished.
(added comments re breaks)
The calculation of break time and who goes when is left up to the individual crew. Break time begins at top-of-climb and ends about an hour before landing, (about half hour before top of descent). This permits the last crew member on break to shake off the sleep and be alert for descent preparation, briefings and the landing. On an 11hr ramp-to-ramp flight, each break would be just over 3hrs apiece, (11 - 1.5hrs / 3 = 3:20 each).
Because the accident occurred at just about the time for crew change, it is a guess as to whether the captain had just left the cockpit for his break or whether he was just returning from the first break, (I'm assuming a total flight time of 11hrs).
Long breaks are discouraged to avoid falling into deep REM sleep which is more difficult to wake up from. Everything equal, my experience is, usually the PF gets first choice, the RP last choice.
The cockpit crew rest module, depending again upon installation, (how the airline ordered it), is either behind the cockpit on the starboard side just in front of the Business Class Galley, with two bunks laterally mounted and about 18" width between the bunks and the cockpit wall to stand and change in, or the crew member takes a business-class seat reserved for the purpose, usually a single window seat, puts up a velcroe-mounted tent which fastens around the seat and from the overhead bin structure, (and tries to sleep through the flourescent overhead lights which aren't blocked, and/or the cabin service. Best break time is the middle one when no service is being done).
Sorry for the pithy remarks but crew "rest" is an oxymoron in such an arrangement. A dropped wine-bottle next to the cockpit crew rest facility is like a rifle-shot. The B777 cockpit crew rest upstairs behind the cockpit is a palace by comparison. The A340-500 and 600 F/A crew rest area is underneath the rear galley and is also a superb installation. it was also an option for cockpit crew but being the entire length of the aircraft away from the cockpit and having to get by trolleys and passengers was viewed as unacceptable, at least by our committee.
Photo of AA587, "top of the hoop" if I have that right, with the ears and the place for the pins. The BEA Report also has a good cross-section showing the hoop, again, if I have that right.
bearfoil;
The crew rest capsule the same. This is difficult, for we assume it was holding the Captain, and perhaps one or two rest FA's. How did it come to be found?
The structure found is the Cabin Crew Rest Module. It is in the belly of the a/c, mid-section and sleeps about six if I recall depending upon the installation. Some F/A's would have been on break as 3+hrs in, the first service would be finished.
(added comments re breaks)
The calculation of break time and who goes when is left up to the individual crew. Break time begins at top-of-climb and ends about an hour before landing, (about half hour before top of descent). This permits the last crew member on break to shake off the sleep and be alert for descent preparation, briefings and the landing. On an 11hr ramp-to-ramp flight, each break would be just over 3hrs apiece, (11 - 1.5hrs / 3 = 3:20 each).
Because the accident occurred at just about the time for crew change, it is a guess as to whether the captain had just left the cockpit for his break or whether he was just returning from the first break, (I'm assuming a total flight time of 11hrs).
Long breaks are discouraged to avoid falling into deep REM sleep which is more difficult to wake up from. Everything equal, my experience is, usually the PF gets first choice, the RP last choice.
The cockpit crew rest module, depending again upon installation, (how the airline ordered it), is either behind the cockpit on the starboard side just in front of the Business Class Galley, with two bunks laterally mounted and about 18" width between the bunks and the cockpit wall to stand and change in, or the crew member takes a business-class seat reserved for the purpose, usually a single window seat, puts up a velcroe-mounted tent which fastens around the seat and from the overhead bin structure, (and tries to sleep through the flourescent overhead lights which aren't blocked, and/or the cabin service. Best break time is the middle one when no service is being done).
Sorry for the pithy remarks but crew "rest" is an oxymoron in such an arrangement. A dropped wine-bottle next to the cockpit crew rest facility is like a rifle-shot. The B777 cockpit crew rest upstairs behind the cockpit is a palace by comparison. The A340-500 and 600 F/A crew rest area is underneath the rear galley and is also a superb installation. it was also an option for cockpit crew but being the entire length of the aircraft away from the cockpit and having to get by trolleys and passengers was viewed as unacceptable, at least by our committee.
Last edited by PJ2; 5th Mar 2010 at 04:15.
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Yaw-dampers
I’m sorry if this has already been mentioned, but just to be sure:
On the B747-400 we have frequently practiced the volcanic-ash scenario losing not only (all of) our engines (possibly explains the RAT on the B748
), but also our IAS indications (due clogged Pitot-Static lines). As a result, flying the aircraft becomes a bit challenging; not as much due to the lack of airspeed indication (you can always use GS or AOA [MCDU] as a fair replacement) or the lack of engines (although that does pump up the adrenaline a bit); the main problem is the yaw-damper(s): since rudder deflection of the yaw-damper (both function and max; rudder ratio changers) is IAS related, an IAS near zero will result in max rudder deflection ... and I don’t know whether the rudder/vertical-stabilizer can take that kind of punishment at Mach .8x (the B744 might .. since it is still a heavy-metal aircraft; the A330 though …). Not hard to see the analogies of blocked PS lines due volcanic-ashes and severe icing.
As bearfiol rightfully put it: the rudder may be allowed to shear of, the design of the vertical stabilizer should be such that it won’t ... indeed, no aircraft will fly without vertical stabilizer.
Not only check the design of the VS-rudder; also check the logic of the yaw-dampers…
On the B747-400 we have frequently practiced the volcanic-ash scenario losing not only (all of) our engines (possibly explains the RAT on the B748
), but also our IAS indications (due clogged Pitot-Static lines). As a result, flying the aircraft becomes a bit challenging; not as much due to the lack of airspeed indication (you can always use GS or AOA [MCDU] as a fair replacement) or the lack of engines (although that does pump up the adrenaline a bit); the main problem is the yaw-damper(s): since rudder deflection of the yaw-damper (both function and max; rudder ratio changers) is IAS related, an IAS near zero will result in max rudder deflection ... and I don’t know whether the rudder/vertical-stabilizer can take that kind of punishment at Mach .8x (the B744 might .. since it is still a heavy-metal aircraft; the A330 though …). Not hard to see the analogies of blocked PS lines due volcanic-ashes and severe icing.As bearfiol rightfully put it: the rudder may be allowed to shear of, the design of the vertical stabilizer should be such that it won’t ... indeed, no aircraft will fly without vertical stabilizer.
Not only check the design of the VS-rudder; also check the logic of the yaw-dampers…