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.

With you, 'Diversification' - post 363 says it all. Possibly 'Red Herring' rather than 'Red Ring'? 36g arrived from 'mm43' at post 377

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

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

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).

Diversification,
Yo have a link to the full report?
My Norwegian isn't perfect, but I can read it.

CJ

Diversification

Welcome. Are you ex PA? PM me if you wish, I am curious. :ok:

bear

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.

Delay
 

CJ and Bear, my answer is delayed because for some unknown reason, the administrator wanted to check it first.

SOP, my friend, let them come to know you. It is brief, and just caution on their part.

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

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

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?

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.

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.

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".

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.

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.


http://img4.imageshack.us/img4/2629/aa58709.jpg

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.

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 :ok:), 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…

LN-PAA again
 

Try this link to get the report; 1993/03 | sht
My previous post apparently disappeared somehow.

PJ2

I think a picture is worth at least a thousand words. Given that the shackles and pins look as they do, reasonably untouched, and the hoops have broken away, burned, and exposed the Hardy mounting bed, I can't understand why these metallic beds are "Battleship engineered" bomb proof, and the Stabiliser is "frangible". Composites and two phase materials are ill equipped for concentrated bearing points, especially when considering there is a metallic and polymer join to fail. One or the other, but merging them is something that may never be mastered.

bear

I agree on the composites - I suspect we still have much to learn there. It took some painful lessons before we figured out how to make aircraft (safely) out of aluminium...

I agree on the rudder attachment vs. VS attachment as well - seems like a good fail-safe has been missed there in favour of "strong enough" (and probably right across the industry - a few 737s would have been better off without the rudder). I do wonder why this is, since the extra strength (of the rudder hinge) implies extra weight which is rarely there without reason. Is it possible that as a moving part the rudder hinge has a cycles-to-failure requirement that leads to it being stronger in static load than the VS attachment ?

Now those VS attachments - again are they much stronger and hence heavier than required ? Maybe they were originally designed to hold a heavier metal VS - possible I suppose. Or maybe they aren't so much different in strength to the composite VS (after all, the overloaded joint always has to fail one side first) ?

A couple more thousand words:

http://img3.imageshack.us/img3/8127/lugso.jpg http://www.3news.co.nz/Portals/0-Art.../airnz_320.jpg

First one is those same attachment lugs (I believe) from AF447. This time the composite didn't break, and the mountings were ripped out of the fuselage - by the VS. If the composite strength was a lot lower than the mounting, then we'd expect the same failure mode under the same loading.

Second image is the VS from the NZ airbus at Perpignan. It looks as though, again, the VS took attachment & some fuselage with it (I admit there isn't enough detail in the image to be sure - best image I could find). Now, in this case we know that the VS was from a high speed water impact and an intact aircraft that disintegrated on impact.

Conclusions:

• It is definitely possible for the VS to float away in one piece and good condition from a high speed water impact of an intact a/c
• The failure mode was different to 587 (different model, but I believe the attachment design is the same)
• If (and this may be your bias and mine) the metal attachment points are stronger than the composite VS, then the forces leading to VS failure must have been significantly different in 587 and 447.

My thoughts are that the metal attachments are stronger in normal circustances, but the fuselage was already being crushed, by impact with the water, as the VS departed.

Flying Without a VS
 

Actually, a B-52 flown by a Boeing test pilot lost its vertical stabilizer in rough weather and landed safely at an Air Force Base in Arkansas.

SmilinEd

I've seen the pic, but can't find it at the moment. I recall seeing some residual structure on the Dorsal spine of the Fuselage, very scant, but not flush, I think it also had the old turret, good for a little Longitudinal stability, still an impressive RTB.

bear

I saw the B-52 pic only recently. Yes, it had a small bit of VS sticking up, but more importantly, #1 and #8 engines were well outboard and could be modulated for yaw stability much better than a twin.

GB

Fun: A fighter called for priority landing due to bingo fuel. ATC told him to hold, as they had a B-52 coming in with an engine out.

"Ah, the dreaded seven engine approach.."

Here it is:

Enjoy.

Lloyd.

http://www.aero-farm.com/public/242636-B52.jpg

Fuel calculations
 

There is one thing I really would like to understand.. Der Spiegel, as known, says:

A loophole allows him to enter Bordeaux -- which lies several hundred kilometers closer than Paris -- as the fictitious destination for his fuel calculations. "Major deviation would therefore no longer have been possible anymore," says Gerhard Hüttig

What are your comments, as professionals, about the idea that the plane entered an area of severe turbulence because of the above?

Did it really?

How do you know that?

That's what Der Spiegel says ("strong turbulence" thick ice crystals etc..). You imply we (still?) can't know, I assume.
And anyhow I do remember having seen this (recontruction of flight path)
Air France 447 - AFR447 - A detailed meteorological analysis - Satellite and weather data

Lomapaseo, PMFJI...

wizele;
Please take the time to read through this thread for some information on your point.

The "shortage of fuel" and inability to execute a diversion around weather due to a shortage of fuel is nonsense and has been dealt with by those who do airline flying for a living.

Characterizing standard flight planning techniques as a "loophole" is incorrect and misleads readers who may not know any better. It is a statement made in ignorance of how airline flight planning is done.

There are those in the world who make money by sensationalizing accidents at the expense of the victims and their families. They do not appear to be interested in finding out what happened or telling readers something new about the accident.
In my view, Der Spiegel is the last source of information someone should read to get accurate, reliable information on aviation accidents.

We cannot know, in a way that explains the accident, what happened because the flight data recorders have not been located. The data recorders are the best source of information which can tell us what happened and even then we may not know all the details.

All else is pure speculation; anything offered by public media cannot be taken seriously.

This has been discussed here before:
a) It is not a 'loophole' but common practice and an approved procedure on long-range flights
b) WX avoidance is not normally a MAJOR diversion and would almost certainly have been considered.

BOAC;
To put a bit of flesh to your comment, for an A330 on such a flight, a 30nm to 50nm lateral diversion (to the left or right of course, for others), around enroute weather would burn between 200 and 500kg of fuel. In effect, (it can be worked out mathematically, and some here have done so), such diversions add perhaps 40nm or about 5 minutes to the flight plan distance/time. The A330 burns about 100kg per minute in cruise.

The arrival fuel was, if I recall either from a comment here or from the BEA report, about 6.5T which is pretty standard for an A330. Even a major diversion costing 1000kg would not compromise arrival fuel seriously. Minimum fuel for the A330 (the point at which the "low fuel caution" comes on) is about 2.7T depending upon a/c pitch attitude.

I bow to your 330 experience, PJ, but I'm surprised it is even that much if an early turn and a slow return to track is made? Anyhow, we are agreed it is certainly not 'major'.

BOAC - Yes it's small; - the original argument, (that the crew may not have felt that there was sufficient fuel, due to filing short of destination and later dropping "the alternate", such that diverting around weather was not possible and therefore did not), is moot; there is no basis for the argument, or the point, whatsoever.

A large deviation that would add perhaps 40nm/5minutes/500kg to the flight plan is a lot, given the "geometry" of such diversions done early, as you say. (Sometimes, (obviously), it is best to wait until closer in to ensure clear down-stream pathways and avoid cells attenuated/blanked by closer, larger cells). But the figures are indeed in the ballpark for the A330. For a ten hour flight it would not be unusual to board 1T of Wx Fuel for pos. diversion, on top of contingency, alternate and min.fuel.

I obviously can't comment on theoretical diversion-planning around the weather that AF447 and seven or eight other flights faced but a "larger slice" at a diversion, (longer distance) may have been considered given the relative proximity of cells and the length of the line.

But the evidence that the line was successfully negotiated, as are such ITCZ lines negotiated every day by many airliners, is evidence for the fact that it is done successfully all the time and fuel "emergencies" remain rare and therefore flight planning techniques are working as intended. Even at a full 1T of fuel, there was plenty of reserve fuel left to complete the flight to CDG without concern.

While not intending to draw any more attention to the Der Spiegel op-ed, one point is important to clarify regarding the captain. Der Spiegel states:
suggesting that there was a question as to "who was controlling the plane", and that "not wearing a seatbelt" somehow "contributed". Again, ignorance and sensationalism at its worst. Stating that "in emergencies it [placing 'inexperienced First Officers in the left seat - as if there was some 'magic' associated with that position!] can increase the likelihood of a crash." is just plain stupidity and irresponsible writing.

My earlier response to bearfoil deals with this point and also deals with how crew breaks are usually decided. But it is worth repeating, that because the accident occurred just over 3hrs into the flight which is very close to when crew change would be occuring, we do not know whether the captain was just leaving the flight deck or returning. Arguments can be made for both scenarios. Though I think we can be certain that the captain was not in his seat, we can draw absolutely no conclusions or posit any speculations from this; there are just too many if's.

PJ2

PJ2 is right about the crew rest. It's the CC Rest that has been found, and is indeed located in the belly, about mid-section (sleeps 7)
The Cocpit Crew Rest (bunks) is indeed behind the cockpit, starboard side. But it is not in front or anywhere near a galley. In the 330 and 340 the Business Class galley is between the doors 2, not 1. It's perhaps the quietest place in the aircraft.

Arm 36 g
 

I have been looking a lot at the right photo in IRep-2 of arm 32 g and manipulated the photo in various ways. The washer under the bolt-head seems browned by corrosion. None of the other similar bolts/nuts have any visible discoloration of their washers in any of the photos I have seen. Also the metal piece to which arm 36 is attached seems like it was corroded. Finally, I can't make up my mind if the break on the arm which is visible is showing signs of fatique or not. The photographic quality is simply not good enough. Has anybody else seen and thought about this?

PJ2:

So it is possible that the Captain set the course and left the cockpit for his break. And that the 1st officer remained on that course, not deviating to avoid the cells.

Arm 36 g
 

Bearfoil; Diversification; BOAC; et al

Well, having made a fool of myself in misinterpreting the BEA's statement - see AF 447 Search to resume - Page 21 - PPRuNe Forums, 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. http://images.ibsrv.net/ibsrv/res/sr...ons/icon14.gif

mm43

Razoray;
Of course it is possible.

However, having done this many times before retiring and knowing, with variations on the theme because the problems we are confronting are the same no matter the airline or airplane, that these things have much in common, the captain in his or her changeover briefing would not "set the course" and leave the cockpit expecting blind obedience. Nor does such a notion make sense.

If circumstances were such that this kind of directive were required, the captain would, and should, remain in the cockpit until the anticipated threats were handled and passed.

So while it is possible, it is almost certainly not the case. The flight deck crew must remain free to make operational decisions "in the moment" when/if circumstances require. Part of the briefing would include the requirement to call the captain to the flight deck if any operational matter out of the ordinary which, for example, required a significant change to the flight plan or required an emergency drill.

If the captain is uncomfortable leaving the crew for whatever reasons, he or she remains on the flight deck and assigns breaks as necessary, until such time as conditions permit a break for the captain. Such a situation would be very rare and as such is always complex and difficult to define. It could involve someone not feeling well for example; it happens and crews deal with these matters as they arise.

If you need a metric, I would not leave the flight deck in the hands of a First Officer who was brand new on the airplane, who had never been overseas before, and who had never dealt with complex weather systems in the ITCZ or demonstrated to me his/her ability to read and use radar information to navigate same, while in the company of a new, MCP-licensed Relief Pilot. Others will define their personal judgement of comfort differently. I have never had to alter rest schedules for such reasons.

PJ2