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  • 748F icing incident

    Russian authorities are investigating an serious icing incident in cruise during which three engines on a Boeing 747-8 freighter sustained damage and two...


    Russian authorities are investigating an serious icing incident in cruise during which three engines on a Boeing 747-8 freighter sustained damage and two suffered a loss of thrust.

    Federal air transport authority Rosaviatsia identifies the aircraft involved as an AirBridge Cargo 747-8F, registered VQ-BGZ. The 747-8F is powered by four General Electric GEnx-2B engines.

    It had been operating between Moscow Sheremetyevo and Hong Kong on 31 July, and was cruising at 41,000ft at the time.

    The incident occurred at night in the vicinity of Chengdu, about 1.5h before landing, as the aircraft deviated to the right of its intended flightpath in order to avoid a thunderstorm.

    At about 18:00UTC the aircraft entered a veil of cloud not displayed on the weather radar. The crew noticed a rise in air temperature but did not see evidence of ice deposit.

    Flight-recorder data showed the static air temperature increased from minus 54C to minus 34C for 86s. The crew switched the engine ice-protection system from automatic to manual, and the aircraft flew for around 10min in this mode, Rosaviatsia states, before reverting to automatic.

    Some 22min after the cloud encounter the aircraft's inboard left-hand engine underwent a surge and automatic restart. Two minutes later the neighbouring outboard engine experienced a speed reduction to 70% of N1, while the inboard remained at idle thrust.

    Rosaviatsia says the aircraft landed at Hong Kong and inspection found damage to the first-stage high-pressure compressor blades of both left-hand engines as well as the outboard right-hand powerplant.

    In a bulletin to carriers the authority says the aircraft was caught in a region of "unexpected" and "unpredictable" weather conditions, leading to ice deposit on unheated parts of the high-pressure compressor. Rosaviatsia notes that the lack of comprehensive knowledge about crystal icing, and the difficulty of detecting the phenomenon, constitutes a continuing hazard.

  • #2
    How do you defend against something like this?

    Comment


    • #3
      Originally posted by Evan View Post
      How do you defend against something like this?
      I have no idea. I'm sure it warrants further study.

      Comment


      • #4
        I wonder why they did not do a precautionary landing (unless HK was the nearest airport). Loss of power in certain engine combinations could result in a crash.

        By the way NASA is doing a lot of research on engine icing at Ames.
        How does ice accumulate inside hot turbofan jet engines during flight? NASA scientists, working with engine manufacturers, are closer to answering that

        Comment


        • #5
          Less than a year old, VQ-BGZ is the registration.
          "The real CEO of the 787 project is named Potemkin"

          Comment


          • #6
            Originally posted by Evan View Post
            How do you defend against something like this?
            1) With design of robust engines that can survive the event, and 2) installing more engines per plane than required to sustain flight, in case one fails to survive the event.

            All in all, it seems to have work in this case. It didn't even go to the second line of defense.

            --- 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


            • #7
              Originally posted by Gabriel View Post
              1) With design of robust engines that can survive the event, and 2) installing more engines per plane than required to sustain flight, in case one fails to survive the event.

              All in all, it seems to have work in this case. I didn't even go to the second line of defense.
              No conceivable sensor to tell you it is occurring?

              Comment


              • #8
                Originally posted by EconomyClass View Post
                No conceivable sensor to tell you it is occurring?
                Probably yes. I can also think of sensors to tell the pilot that he had their eyes closed for more than 15 seconds, to measure the O2 saturation in the pilots' blood, to detect birds ahead, to measure the wight and balance of the plane before take-off, to measure the plane's acceleration during the take-off roll to see if it matches the expected performance (actually this sensor exists on planes, it just takes writing the appropriate lines of software), and I could go on.

                All of the above would have saved more planes than a sensor for this incident.

                I've never heard of an event exactly like this before, and in this only datapoint that I know the plane landed at its intended destination with all the 4 engines running and providing adequate thrust (albeit damaged). It could save lives someday but, with the info we have so far, I have the impression that more lives can be saved investing that time and money (scarce resources) in other places of the system.

                But there is little info yet and I can be wrong. Let's wait to see what the investigators find.

                --- 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


                • #9
                  Oh yeh. I'm sure there are lots of sensors that might be added to a plane. And problems that would come with them.

                  Comment


                  • #10
                    Originally posted by EconomyClass View Post
                    No conceivable sensor to tell you it is occurring?

                    O.K. This is the same model with the same GE GenX engines on one of the aircraft that I fly regularly. There is an auto position for the engine anti-ice system, and that is normally the position that system is left in. It has a whisker type probe on the forward side of the fuselage. When there is an ice build-up on the probe enough to make it vibrate, the system is activated. There is of course an on position as well. The letter that was sent out by Boeing to all operators of the -8 yesterday explain that the damage was done in a section of the engine that is not protected by the anti-ice system. Also, the weather phenomena that they encountered is probably a 1 in a million occurrence. E.C., if they put all the sensors on the airplane you want they will be able to fly a half dozen passengers across the pond. (Well that is a slight exaggeration).

                    Comment


                    • #11
                      Originally posted by EconomyClass View Post
                      Oh yeh. I'm sure there are lots of sensors that might be added to a plane. And problems that would come with them.
                      Exactly, that's the point. So better prioritize where a sensor is more a solution than it is a problem.

                      --- 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


                      • #12
                        Originally posted by Evan View Post
                        How do you defend against something like this?
                        Several years ago I read a couple of articles in the Boeing Aero magazine that talked about high-altitude icing.

                        The books will tell you that if the OAT is -40C or less than any moisture you run into will be ice crystals. My personal technique, however, is to turn ice protection any time I'm in clouds in a convective area, regardless of OAT--my theory being that water droplets being thrown up from lower altitudes may not have time to freeze.

                        Here's some interesting reading:
                        Engine Power Loss in Ice Crystal Conditions

                        Avoiding Convective Weather and Ice-Crystal Icing Engine Events
                        The "keep my tail out of trouble" disclaimer: Though I work in the airline industry, anything I post on here is my own speculation or opinion. Nothing I post is to be construed as "official" information from any air carrier or any other entity.

                        Comment


                        • #13
                          Originally posted by snydersnapshots View Post
                          My personal technique, however, is to turn ice protection any time I'm in clouds in a convective area, regardless of OAT--my theory being that water droplets being thrown up from lower altitudes may not have time to freeze.

                          Mine too! I always say anti-ice and continuous ignition are free!

                          Comment


                          • #14
                            Originally posted by BoeingBobby View Post
                            Mine too! I always say anti-ice and continuous ignition are free!
                            Hmmm, not exactly free, even the "fasten your seat belts" sign is not free, but ok

                            I think that some airplanes have a limit on how much time continuous ignition can be used continuously. For example, I think that the MD-80 has a 10 minutes limit.

                            --- 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


                            • #15
                              Originally posted by snydersnapshots View Post
                              Several years ago I read a couple of articles in the Boeing Aero magazine that talked about high-altitude icing.

                              The books will tell you that if the OAT is -40C or less than any moisture you run into will be ice crystals. My personal technique, however, is to turn ice protection any time I'm in clouds in a convective area, regardless of OAT--my theory being that water droplets being thrown up from lower altitudes may not have time to freeze.

                              Here's some interesting reading:
                              Engine Power Loss in Ice Crystal Conditions

                              Avoiding Convective Weather and Ice-Crystal Icing Engine Events
                              Great links, thanks.

                              Comment

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