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  • 747/767 questions

    Hello AJ,

    had a few questions about both aircraft. First, correct me if I'm wrong, but it seems like the 744 doesn't need full flaps that often for landing like the classics do. Is that right? Or if it does, the full flaps setting doesn't deploy them as much as on the classics or so it seems. Also, is the trailing edge flap system different or a bit modified from previous versions of the 74'?

    Also, does the 744 takeoff at a shallower angle than the classics do? I've seen many a video (and from personal expereice as well) where it seems like the 744's takeoff angle isn't as steep as say, a 742's. Thanks, I know I'm asking a lot of questions here.

    Foxtrot

  • #2
    Foxtrot,

    The B747-400 was designed with an all new more efficient wing. Now I cant confirm or deny the questions that you have, having little experience on the classic.
    However All of them could be attributed to a more efficient design of aircraft and better design of engines.

    -Myriad

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    • #3
      Hi Foxtrot.

      The 747-400 has two flaps setting certified for a normal landing, '25' and '30'. Flap 30 is the Boeing preferred method, giving the lowest Vref and shortest landing roll. Flap 25 has become popular due to the lower fuel burn and noise on final, however the aircraft is not as speed stable. Qantas used a policy of Flap 25 and idle reverse thrust after landing to meet Sydney and Heathrow noise abatement and improve carbon brake usage (carbon brakes are more efficient at higher temperatures). It was abandoned as SOP after an unfortunate overrun of Runway 21L in Bangkok. My understanding is the trailing edge flap system was taken directly from the classic, however some composite compnents were substituted.

      As for rotation angle I'm not sure as I never flew the classic, however, as Myriad says, it's comparing apples and oranges due to the lengthened wings on the -400. To my knowledge nobody has tried a -400ER's 415,000kg MTOW on a Classic wing, I'm sure the Vmu would be a little too high!

      Cheers,

      AJ.

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      • #4
        Re:

        Ahh, thanks for the replies guys! And yes, I completely forgot to ask the question I had about the 767. Have you flown the -200 variant and if so, ever done a no-flaps takeoff? I think you mentioned that the 762 can do a no-flaps takeoff w/ only the leading edge slats being deployed.

        Foxtrot

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        • #5
          The 762 can do as you said, but the 763 cant do that due to the COG I believe, AJ could perhaps expand on that.

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          • #6
            Originally posted by chrisburns
            The 762 can do as you said, but the 763 cant do that due to the COG I believe, AJ could perhaps expand on that.
            #1 reason why I think its a good idea for everybody who doesn't have years and years of experience (myself included) to post some kind of source backing their information up.

            If we get nothing but people going "well I heard this....but I dunno" this forum is going to be absolutely useless.

            Any plane can do a 0 flap takeoff, its just a matter of runway length. The purpose of flaps on takeoff is they allow the aircraft to take off at a lower airspeed than required if the wing were 'clean'.
            Last edited by screaming_emu; 2005-11-09, 22:55.

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            • #7
              Foxtrot, I did fly both the -200 and -300. Our -200s have now been retired.

              Flap 1 (slats only takeoffs) are only available on the -200 series due to the geometry limit on the -300. You simply could not achieve the required pitch attitude on the -300 before striking the tail on the ground.

              At Qantas we kept a standard flap setting of 5 for almost all departures. Flap 15 is used on short runways (like Narita B or Wellington) at high weights, or during windshear conditions.

              As the flightless bird has said flap zero takeoffs are achievable, but runway length and tire limit speeds prohibit their use!

              Cheers.

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              • #8
                As the flightless bird has said flap zero takeoffs are achievable, but runway length and tire limit speeds prohibit their use!
                I have been on small aircraft which have used 0-Flap takeoffs, An F100 flight about 3 months ago springs to mind...

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                • #9
                  I was talking the 767 as asked Myriad!

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                  • #10
                    Originally posted by AJ
                    I was talking the 767 as asked Myriad!
                    Of course, i wonder what the largest type of aircraft is that can safely execute a 0-flap takeoff?

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                    • #11
                      Originally posted by Myriad
                      Of course, i wonder what the largest type of aircraft is that can safely execute a 0-flap takeoff?
                      The only other large widebody that routinely uses only leading edge devices for takeoff is the A300.

                      As AJ and Emu said, any airplane can theoretically accomplish a no flap takeoff. The wing just has to be going fast enough to have sufficant lift.

                      But things like fuse. length, maximum tire speed, and runway length are all limiting factors. You're also more prone to tail strikes, as the wing needs a greater angle of attack to acheive the desired lift.

                      When we do Flaps 5 takeoffs in the 727, the airplane will sit on the mains after rotation for what seems like an eternity. And the tail-skid will come very very close to the ground.

                      Hope that helps a bit more.
                      Anybody can fly a round airplane....

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                      • #12
                        Last couple of times I deadheaded on 767-200ERs, they were flaps 0 takeoffs. Slats extended only. Both were on flights where the a/c was light.
                        Bite me Airways.....

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