UA 787 returns to Narita 3 times for same mechanical issue | FerrariChat

UA 787 returns to Narita 3 times for same mechanical issue

Discussion in 'Aviation Chat' started by 11506apollo, Jul 5, 2020.

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  1. 11506apollo

    11506apollo Formula 3
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    #1 11506apollo, Jul 5, 2020
    This is an approximate translation from an article published in AEROIN.Net

    A United Airlines Boeing 787-9 was involved in an unexpected and unusual episode. After two days, the aircraft had to return three times to Tokyo's Narita International Airport, after problems with takeoff.

    The plane had arrived in Tokyo on July 2, at 7 hours and 45 minutes local time, coming from Chicago O'Hare International Airport, in the USA, after flying UA2821.

    After that, getting out of there became a challenge. Three times, between July 2 and 3, United Airlines' 787, with American registration number N27958, tried to leave Narita, but was forced to return to the departure airport.


    Records of the three aborted flights, after the aircraft arrived in Japan. Image: Flightaware.
    First try

    The 787 was to continue its mission, proceeding to Beijing International Airport in China, taking flight UA2822. Thus, at 9 hours and 12 minutes of July 2, the aircraft took off to the Chinese capital.

    However, after 50 minutes of flight, while on the FL400 (40,000 feet - 12192 m) and about 160 nautical miles (269 km) from Tokyo, the crew decided to return to Narita due to a problem with the devices on board left wing attack (also known as Krueger flap). An hour after departure, the aircraft landed safely in Tokyo, with a landing speed above normal.


    Registration of the first flight (Beijing) of the 787, on July 2nd. Image: Flightaware.
    Second attempt

    On the same day 2, three hours after returning from the first attempt to Beijing, the 787 took off from Narita at 13 hours and 47 minutes, this time bound for San Francisco International Airport, in the USA, to fly UA2770.

    When the aircraft was ascending, on the FL230 (23,000 feet - 7,010 m), the crew interrupted the procedure, again due to the problem with the flaps on the leading edge of the left wing. The aircraft returned to Narita again, landing safely about 90 minutes after departure, again with the landing speed above normal.

    This time, the aircraft remained on the ground for about 21 hours and 30 minutes.


    Registration of the second flight (San Francisco) of 787, on July 2. Image:

    Third attempt

    On July 3, everything was ready for departure and the 787 took off from Narita for a new attempt to fly UA2770 to San Francisco. The takeoff took place at 13 hours and 2 minutes, local time.

    Again, when the aircraft was in the ascension procedure, this time in the FL290 (29,000 feet - 8,839 m), the crew interrupted the procedure due to the same previous problem, related to the flaps on the leading edge of the left wing. Thus, the aircraft once again returned to Narita airport, landing safely, again with a landing speed above normal, about two hours after takeoff.


    Registration of the third flight (San Francisco) of 787, on July 3. Image: Flightaware.
    On the ground since then

    There were no reports of more serious problems in any of the three episodes. The aircraft, which carried out cargo transport flights, had only four crew members on board.

    Since the last of the three landings, the 787 has remained on the ground, with the schedule to leave Japan on July 5, 2020, this time as flight UA2787, also to San Francisco, USA.

    According to Narita authorities, the runway was closed for a total of 13 minutes, while airport inspectors inspected it for possible damage after emergency landings, reports Aerotime.


    Image: DAC - IAC - Aircraft Maintenance Mechanic - Cell.
    Landings of the aircraft at a speed above normal show the problem in the Krueger flaps, whose function, like that of the trailing edge flaps of the wing, is to increase the lift of the wing, by increasing its curvature and raising the coefficient of lift, which allows the aircraft to reach greater angles of attack and maneuver at lower speeds, being used only for takeoffs, approaches and landings.
     
  2. BMW.SauberF1Team

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    #2 BMW.SauberF1Team, Jul 5, 2020
    What's the advantage of using a Krueger flap design over a slat? Seems like the Krueger's design requires a longer range of motion and also more against the direction of airflow to reach its final position compared to other methods.
     
  3. Bob Parks

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    #3 Bob Parks, Jul 5, 2020
    What was the problem with the flap? Did anybody state that? What ever it was, it was beyond the mechanics to understand or to fix. After the second abort there should have been a test run, I think. That is operated by a mechanical linkage but there is an adjustment to get the flap to fair with the wing surface.
     
  4. 11506apollo

    11506apollo Formula 3
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    #4 11506apollo, Jul 5, 2020
  5. Bob Parks

    Bob Parks F1 Veteran
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    #5 Bob Parks, Jul 5, 2020
    The Krueger is used in the inboard portion of the wing because of the complexity of curvatures and wing shear, if I remember correctly. The flexible Krueger flap approximates and extends the curvature of the wing upper curve but lacks the more effective slot of the slat that maintains attached flow at higher AOA. Thus allowing the inboard wing to stall before the outboard does. Slats have to have a straight line configuration , like a venetian blind. I had a little trouble reading the captions on the flap drawing. Maybe that's why they are having so much trouble.
     
  6. Bob Parks

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    #6 Bob Parks, Jul 5, 2020
    I failed to mention that the original purpose of the Krueger flap was to block the reverse flow of air that came around the leading edge and produced a some times irreversible and fatal stall. The leading edge intercepted air that that caused the reverse flow and directed it over the upper surface. Those illustrations aren't totally correct. I have some that I did when I was instructing and will try to post if I can find them
     
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  7. Bob Parks

    Bob Parks F1 Veteran
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    #7 Bob Parks, Jul 5, 2020
    I just remembered that this deep stall problem that initiated the K-Flap design is what caused the crash of several Comets for which the pilots were blamed . It also caused the crash of a KC-135 in the New England area, Main if I remember. There wasn't enough power or elevator to get out of the stall.
     
  8. tazandjan

    tazandjan Three Time F1 World Champ
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    #8 tazandjan, Jul 5, 2020
    Bad news is that normally whenever an asymmetric condition is sensed when the flaps/slats are extended or retracted, they lock out to prevent adverse roll inputs. Then you are stuck with wherever they locked out. Hence higher than normal landing speed, even when fuel is dumped. Sounds like nobody was qualified to fix her.
     
  9. Bob Parks

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    #9 Bob Parks, Jul 5, 2020
    I should have said, " the leading edge of the FLAP" intercepted the air that caused the reverse flow. Picture if you can, a stagnation point just aft of the wing leading edge where the up-coming air splits with some flowing aft and some flowing forward. That forward flowing air is what causes the stall problem. The K-flap is wide enough to dip down into the upper level of the air that splits forward and directs it up and over the wing to prevent the stall. Slats actually rotate the wing leading edge downward to do the same thing while also forming a powerful slot that feeds high velocity low pressure flow over the wing upper surface that maintains attached flow and more lift at low speeds. Without it an approach will be at higher speeds. Please forgive me if I'm preaching to the choir and appear to be a know it all. I'm not. Wing stuff has always been interesting to me and I enjoy sharing the art of it.
     
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  10. Gatorrari

    Gatorrari F1 World Champ
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    #10 Gatorrari, Jul 8, 2020
    Those occurred when the pilots rotated at too low a speed, which stalled the wing and kept the aircraft from lifting off. Once that was determined, pilots were reminded to wait until V2 to rotate the airplane.

    Unfortunately, a Canadian Pacific crew that had picked up a new Comet 1 in England and was flying it back to Canada the long way around forgot that when taking off from Karachi and crashed on takeoff. For some reason, even though the aircraft was not at fault, C.P. immediately cancelled the rest of their order, which was probably a blessing in disguise when BOAC Comet 1s began disintegrating in flight.
     

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