Layman question on U2 | FerrariChat

Layman question on U2

Discussion in 'Aviation Chat' started by ND Flack, Jun 26, 2009.

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  1. ND Flack

    ND Flack Formula 3

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    So I just watched this clip of the James May in a U2 BBC program - http://www.youtube.com/watch?v=1PmYItnlY5M&feature=related - and I noticed two things as they were landing the thing.

    1) It seems like the pilot had to almost fly the nose into the ground to get the damn thing to lose altitude rather than the nose-high attitude you usually see in an airliner about to land, which I assume is a product of the ludicrous amount of lift generated by the wings.

    2) The a/c had a significant amount of flaps dialed in while landing

    Now, if the pilot is having a difficult time overcoming the amount of lift being produced by the aircraft, why would he increase the lift produced by extending flaps? Is it just a matter of increasing drag to slow the thing down? Or is the difficulty landing a matter of some sort of ground effect?
     
  2. SilverF20C

    SilverF20C Formula 3

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    From a layman perspective:

    I would imagine that as speed decreased, so would his initial lift going in for a landing. Therefore, the flaps would add any needed lift as he pitched upwards at the slower speeds in case the pilot needed to touch and go.

    BTW, here's a pretty cool video of a chase car describing the landing procedure.
    http://www.youtube.com/watch?v=-ELjCkG4Gl0
     
  3. SilverF20C

    SilverF20C Formula 3

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  4. solofast

    solofast Formula 3

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    It has to do with the landing gear....

    If you didn't have flaps you would have had a higher nose up angle of attack as well as a higher speed at landing. Since they didn't want to put tall landing gear on it (to save weight and make it possible to use the wing tip outrigger system), then it had to land at a flat AOA. Hence the flaps... Also flaps are a good way to add drag as well as decrease the landing speed, so you get a slower landing and shorter roll out....

    All part of finding the best compromise without going over the edge of the envelope. Something that Kelly Johnson was very good at...
     
    Last edited: Jun 26, 2009
  5. SilverF20C

    SilverF20C Formula 3

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    Yet again, thank you for your insight!
     
  6. tazandjan

    tazandjan Three Time F1 World Champ Lifetime Rossa Owner

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    ND- Like solo said, flaps and slats are high lift, high drag devices. They slow an aircraft down by providing drag and lower stall speeds by providing low speed lift. The touchdown on a U-2 is so sensitive they use a chase vehicle to follow it down the runway and call out altitudes because the aircraft wants to float forever until the squat switches are activated and the spoilers pop up. Every landing is video taped for review. The U-2 is really a high performance sailplane with a jet/turbofan engine.

    Remember you have no outrigger gear on landing and really want to make sure the final touchdown of one wingtip is gentle so you do not ground-loop the aircraft. A balancing act requiring a really good stick and rudder pilot. All the landing gear is on the centerline of the aircraft, unlike the tricycle configuration of most aircraft, but with no permanent outriggers like a B-52 or the old B-47, so you want to land in a near level attitude.

    A challenge to land, especially after 10-14 hours in a pressure suit. The U-2s flew out of Taif with my F-111Fs during Desert Storm, and they were usually really hurting after a long mission. We got in trouble for delaying one's landing when he came down during a mass F-111F recovery.


    Taz
    Terry Phillips
     
  7. ND Flack

    ND Flack Formula 3

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    As always, thanks to all!
     
  8. James_Woods

    James_Woods F1 World Champ

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    Do not absolutely know if true, but one rumor had it that the AF had a Camaro Z-28 on at least one base to run along with the U2 as it landed and call out touchdown altitudes down to zero.
     
  9. ND Flack

    ND Flack Formula 3

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    Watch the video in the link that I posted above -- it's a GTO at that base :D
     
  10. James_Woods

    James_Woods F1 World Champ

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    Must have been quite a few years before the Z-28 of my rumor - which brings up another question; wonder if they did this (and what they used) back in the Eisenhower days before even the GTO? FI Corvette? Chrysler 300?
     
  11. ND Flack

    ND Flack Formula 3

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    Sorry - meant the shortlived GTO of recent vintage - though you have to wonder what they used back in the day when they first flew...
     
    Last edited: Jun 29, 2009
  12. TooTall

    TooTall Karting

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    Yes they did. I used to work for Rockwell on the B-1 program and one day was out at the assembly plant in Palmdale, Ca., known as Air Force Plant 42. While getting the nickel tour of the grounds a U2 rolled out for launch. There was a (then) current generation Z-28 and an AF pickup truck in trail. We watched the launch from alongside the runway and the Z-28 paced the U2 until liftoff. And yes, the climb out was spectacular! At least 45 degree angle of attack. The pickup trailed a bit behind to pickup the outriggers that drop off when the aircraft lifted off. I was told that the Z-28 was driven by a qualified U2 pilot who acted as a safety officer. The pilot had limited visibility on the runway due to the nose-up attitude of the U2 while on the ground and the bulky pressure suit.

    As I recall, the Z-28 was painted black and white like a cop car and had a police style light bar and an array of radio antennas.

    Cheers,
    Kurt O.
     

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