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  • #46
    Originally posted by mfeldt View Post
    P.S. Could anybody supply information about the angular field of view and possibly the range of the on-board weather radar?
    Onboard weather radars can range in excess of 100nm and as far as I know the angular view is about 3 up and down from the centerline of the antenna (which of course can also be tilted up and down)...

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    • #47
      Originally posted by Evan View Post
      Light collision might have sheared off the pitots. That's all I've got for this one.
      Well - the pitots are located all around the forward fuselage so a light collision could damage at maximum only half of them.

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      • #48
        I speculate that a non-catastrophic collision might have severely damaged the front of the A330, including the pitots, resulting in the ACARS messages that were received. The second plane might have flown a bit further and then disappeared in the ocean (although I would expect something to be recovered). I'm sure there is a reason why this theory can be refuted (other than the remote odds of course), and I'm counting on the forum to let me know what that is.
        This is an interesting theory. It is certainly one to be considered. I am still having a hard time understanding how a modern jet just falls out of the sky. You guys are much smarter than me, but it just seems like even if the pitots failed that they could have followed some type of procedure to get them to safety, and at least had the time to notify the company if they couldn't reach ATC. Personally I believe that they probably tried to contact ATC but weren't able to get through. They really need to find the CVR and FDR!
        I do work for a domestic US airline, and it should be noted that I do not represent such airline, or any airline. My opinions are mine alone, and aren't reflective of anything but my own knowledge, or what I am trying to learn. At no time will I discuss my specific airline, internal policies, or any such info.

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        • #49
          And they never change flight level if they are out of contact with ATC unless in an emergency, right?
          Correct, and there are laid down procedures for how to go about it if you do need to in an emergency, and they involve turning a certain amount off track, and choosing levels that are unlikely to conflict with traffic.

          I really don't like the use of the weather radar picture. It does not give an accurate enough depiction of if there were safe ways to traverse the weather band, and it is really making huge assumptions to say that it does.

          Even if they flew right into the middle of a large storm, it is STILL very unlikely (although technically possible) that the aircraft could break up. It doesn't explain the manner in which they crashed. They don't need to be in a storm to pick up icing.

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          • #50
            That plane that caught the windshear in Texas and slammed into the ground [DL 191]didn't break up till it hit the ground. [ir maybe till it hit water tanks] So I don't see the need for the assumption that the storm broke up the plane. All that was needed was to hit an irresistible downdraft. I think after that crash, pilots stopped heading straight into thunderstorms.

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            • #51
              I think I mentioned this in the old thread, but if those thunderstorms are anything like we have here in TX, there might have been nothing there on one sweep, and the by the next sweep something nasty is forming or formed. I would guess that planes that travel through the ITCZ are probably prepared for crazy weather, and have pre-flight plans for what to do if they need to divert? Please?
              I do work for a domestic US airline, and it should be noted that I do not represent such airline, or any airline. My opinions are mine alone, and aren't reflective of anything but my own knowledge, or what I am trying to learn. At no time will I discuss my specific airline, internal policies, or any such info.

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              • #52
                Originally posted by MCM View Post
                I really don't like the use of the weather radar picture. It does not give an accurate enough depiction of if there were safe ways to traverse the weather band, and it is really making huge assumptions to say that it does.
                Are there any radar depictions? The images I have been going by are infrared satellite images. They show cold air masses at the troposphere. The colder the air mass, the more convective power lies beneath it. Convection = turbulence. AF447 seems to have flown directly into the coldest portion of the air mass. The 2nd interim report also mentions this:

                 An additional meteorological analysis shows the presence of strong
                condensation towards AF447s flight level probably associated with convection phenomena.
                 The precise composition of the cloud masses above 30,000 feet is little known, in particular with regard to the super-cooled water/ice crystal diving, especially with regard to the size of the latter
                .

                But I agree that this alone does not show us the real nature of what was happening there at FL350. This is more revealing...

                 Several airplanes that were flying before and after AF 447, at about the
                same altitude, altered their routes in order to avoid cloud masses.


                You have to wonder why these flights chose to divert. I wish there was a way to locate the flight plans and fuel loads of these other flights, and to know if they made their intended destinations without a refuel stop.

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                • #53
                  Which ways did they alter their routes?

                  Weather moves. The first few might have deviated to avoid some weather, and then 10 minutes later it might have been off the route so that a diversion wasn't necessary. Later flights might have had more weather to avoid. How far were they deviating?

                  It happens.

                  I still think you are barking up the wrong tree regarding flying into a storm because of low(er) variable reserve figures. I've never once even DISCUSSED minimising weather deviations to avoid a diversion. If it happens, it happens.

                  I understand where you are coming from, but the point is that weather isn't necessarily dangerous to penetrate and that crew, no matter what the fuel load, would not fly into dangerous weather. If they choose to go through "marginal" weather, as long as they do it with the seatbelt sign on, it is not unreasonable.

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                  • #54
                    Originally posted by EconomyClass View Post
                    That plane that caught the windshear in Texas and slammed into the ground [DL 191]didn't break up till it hit the ground. [ir maybe till it hit water tanks] So I don't see the need for the assumption that the storm broke up the plane. All that was needed was to hit an irresistible downdraft. I think after that crash, pilots stopped heading straight into thunderstorms.
                    DL191 was on final approach to DFW at that time and encountered a microburst - a wind phenomenon that is associated with the bottom of Cb. AF447 was at cruising altitude so whatever brought the A330 down - if it was t-storm-related it was NOT a microburst like the one that hit DL191.

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                    • #55
                      Originally posted by MCM View Post
                      I understand where you are coming from, but the point is that weather isn't necessarily dangerous to penetrate and that crew, no matter what the fuel load, would not fly into dangerous weather. If they choose to go through "marginal" weather, as long as they do it with the seatbelt sign on, it is not unreasonable.
                      With regard to the development of the CB cluster, the report concludes:

                      Analysis of infrared imagery does not allow any conclusion as to the exceptional character of the storm activity in the area where flight AF447 disappeared, but it shows, on the planned flight route, the existence of a cluster of powerful cumulonimbus, identifiable from 1 h 30 UTC. This cluster resulted from the merging of four smaller clusters and its extension from west to east over around 400 kilometres is quite noticeable.
                      If the analysis of the imagery leads one to think that, towards 2 h 00 UTC, the cumulonimbus that made up this cluster had for the most part already reached their stage of maturity, it is very likely that some were the seat of notable turbulence at the flight level.

                      If that's true, it seems reasonably cautious to divert. But we'll never know for sure what they actually encountered.

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                      • #56
                        Originally posted by Evan View Post
                        If that's true, it seems reasonably cautious to divert. But we'll never know for sure what they actually encountered.
                        Which is why "we" can't say whether or not a deviation (not diversion) was reasonable.

                        Comment


                        • #57
                          Originally posted by Evan View Post
                          This is more revealing...

                           Several airplanes that were flying before and after AF 447, at about the
                          same altitude, altered their routes in order to avoid cloud masses.

                          You have to wonder why these flights chose to divert. I wish there was a way to locate the flight plans and fuel loads of these other flights, and to know if they made their intended destinations without a refuel stop.
                          The plane was out of radar coverage.
                          The black boxes have not been found.
                          The exact place of the crash is not known.

                          How would one know whether AF 447 did or did not divert?

                          --- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
                          --- Defend what you say with arguments, not by imposing your credentials ---

                          Comment


                          • #58
                            Originally posted by Gabriel View Post
                            How would one know whether AF 447 did or did not divert?
                            Good point, Gabriel. Maybe AF447 were diverting when they went down.

                            Originally posted by Evan View Post
                            If the analysis of the imagery leads one to think that, towards 2 h 00 UTC, the cumulonimbus that made up this cluster had for the most part already reached their stage of maturity, it is very likely that some were the seat of notable turbulence at the flight level.

                            If that's true, it seems reasonably cautious to divert. But we'll never know for sure what they actually encountered.
                            Well, Evan - airborne weather radar does have its limitations. Maybe they didn't see what was coming or maybe they even tried to divert.

                            Comment


                            • #59
                              Originally posted by Gabriel View Post
                              I will present this "exhibit" that I prepared with no other comment by now but that something looks odd.

                              (Sorry for the crappy quality. I prepared a pdf that barely weights 1/5 of this jpg and has much better quality, but the forum would only accept 19 KB of pdf while several MB of jpg. If someone wants the pdf please PM your e-mail)
                              I'll come back to this now. There are a lot of things that I don't understand or that I am not sure about, so please help me with this. If there is a flight dispatcher, his/her input would be very much appreciated. Pro pilot too, please.

                              1- To begin with, and as I've said before, as far as I know the regulations regarding fuel requirements don't know or care about whether there are other suitable airports along the route. They just mention the destination and the alternate. That's at least for non-stop (not RIF) flights.

                              2- This flight from Rio to Paris was how much, 9 hours? So 10% of that would be 0.9 hours, or 54 minutes. 10% of the trip fuel is what the FARs require for route reserves. I know that this plane was not flying under the FAR, but I'd expect other regulations to be similar.

                              3- The FAR requires fuel for the trip (taking into account the weather forecast along the route) plus a 10% (route reserves), plus enough fuel to miss the approach at the destination and fly to the alternate, plus 30 min at holding speed at 1500ft.

                              4- In general (that is, when an alternate is required), you are supposed to land at your destination still with the fuel to fly to the alternate plus the 30 minutes, so if you have to go around at the last minute you still have enough juice to fly to the alternate and land there with the 30 min reserve.

                              5- In this way, the fuel you have when you start the take-off minus the fuel the you plan for the trip minus the fuel to fly to the alternate minus the 30 min reserve that you shouldn't use except in an emergency is the fuel you plan as available for "normal" contingencies along the flight, such as headwinds that are stronger than forecast (or tailwind that are lighter), additional flying around weather, increased fuel consumption due to ATC not clearing you as high as filed, etc... This amount of fuel should be at least the required route reserve (10% of the trip fuel), but the plane can also have "extra fuel" in excess of that.

                              6- In a RIF (re-clearance in flight) flight plan, you take-off with all the trip fuel, the fuel to the alternate, and the 30 minutes that's required, but less than the required route reserves. However, you file an optional fuel stop at an alternative destination (together with its own alternate airport) where you have all the required fuel, including all the required route reserves. At some point during the flight, if you have not used the route reserves you can legally decide to skip the optional fuel stop and go for the intended destination, because the untouched route reserves that were then not enough for the direct flight are enough now that the remaining flight is much shorter (are, say, 10% what remains of the flight).

                              Now let's move to the jpg:



                              For this flight, the dispatcher expected a given payload that didn't leave enough "room" (i.e. useful load) for enough fuel for a non-stop flight plan to Paris.

                              They presented to the pilots two options (there was a third one but not shown here): They either take less payload than the expected one (leaving off the plane passengers or luggage or cargo if necessary) and added just enough fuel or they used a RIF flight plan with an optional (and hopefully avoidable) fuel stop at Bordeaux.

                              The RIF plan had fuel reduced enough that it allowed a payload of even more than what they expected for this flight.

                              Finally the RIF plan was filed, but for some reason the plane took even less payload than what would have been required to enable the non-stop flight, and then the useful load was maxed adding as much fuel as would fit. This means that the flight, while flying under a RIF flight plan, depart with more fuel than required for a non-stop flight where the optional fuel stop would not be considered.

                              The charts have 4 columns.
                              The first column, Plan 1 (RIF) is the "second option" mentioned above, and is the plan that was finally filed.
                              The second column, "Expected", show the conditions (especially the amount of fuel) had the payload been the expected one.
                              The third column, Plan 2 (DTC), is the other option presented by the dispatcher (and then discarded) and corresponds to the max payload and min fuel that would make it legal to file a non-stop flight.
                              And the fourth column shows the actual condition of the flight, with a payload that is even less than expected and a fuel that is even more that required of the non-stop flight plan (but remember, they still filed the RIF plan).

                              Now let's focus on the bottom-right chart, that shows the amount of fuel in excess of what was required that the plane would have had when landing at CDG had it used exactly the trip fuel as planned. That fuel is the reserve that was available for, as said, stronger headwinds, weather detours, etc. that might make the actual fuel used for the trip greater than the planned trip fuel. This fuel includes the required route reserve and any extra fuel that the plane might be taking beyond what's required.

                              The plane had 20 minutes of fuel. That is that the flight, at the same fuel burn, could have lasted 20 minutes more than planned and still made it to CDG with the required fuel in the tanks when landing there.

                              20 minutes is under no way 10% of the trip, but I'm Ok with that in the sense that, after all, they were in a RIF flight with an optional stopover in Bordeaux which is about 30 minutes short of Paris, so they had some 50 minutes of fuel over what was required to fly from Rio to Bordeaux, and that's probably about 10%.

                              HOWEVER: (and now the odd part starts)

                              Since the plane had essentially the same take-off weight than the Plan 2 (DTC), but less payload and more fuel, that 20 minutes reserve would have been good to go even in non-stop (not RIF) flight plan. Now 20 minutes is NOT EVEN ONE HALF of 10%.

                              Not only that, but the proposed non-stop flight (Plan 2) was legal to go non-stop with ONLY 12 MINUTES OF ROUTE RESERVE FUEL.

                              And not only that, but had they have the expected payload, they would have had just 10 minutes of route reserves over Paris, and the RIF plan (Plan 1) still was good to go with only 3 minutes of reserve over CGD.

                              Now, I'm not judging the safety aspect of this given that they had suitable places to land short of Paris, (basically anywhere from Casablanca to Bordeaux and then some).

                              But what I don't understand is:

                              - How this DTC flight plan matched the fuel regulations.

                              - The "economical soundness" of choosing a strategy that would leave only 10 minutes of reserve. I don't know what's the distribution of actual fuel vs planned, but based in my limited passenger experience I'd say that a 9 hours flight arriving at its destination 10 minutes or more sooner or later than expected at take-off happens more often than not, so they were seriously risking an expensive fuel stop, probably much more expensive than leaving a couple of tons of payload off the plane. (or, they were willing to land at CDG with less than the required alternate plus 30 minutes fuel and not tell anyone? Now that WOULD be a very serious safety breech). I'm not insinuating that that was the case, and I wouldn't expect that from Air France.

                              But as said, things looks odd at least. And probably that' because there's something flawed in my logic or my understanding, in which case help is very much appreciated.

                              --- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
                              --- Defend what you say with arguments, not by imposing your credentials ---

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                              • #60
                                Originally posted by Gabriel View Post
                                But as said, things looks odd at least. And probably that' because there's something flawed in my logic or my understanding, in which case help is very much appreciated.
                                Gabriel - check out the thread on "Reclearance in flight". Most of your questions are covered there, especially the question about the 10%.

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