Page 1 of 6 123 ... LastLast
Results 1 to 20 of 117

Thread: A photograph of Boeing Bobby discovered on the WWW

  1. #1
    Senior Member 3WE's Avatar
    Join Date
    Jan 2008
    Posts
    4,996

    Default A photograph of Boeing Bobby discovered on the WWW

    It's inappropriate to put personal stuff like this up- but his face is obscured, BUT his aircraft is not.- hopefully the mods won't mind.

    Is this suitable for uploading to the photo database?

    PS- Do not over think this, the intent is light humour.

    Click to see full size.
    Click image for larger version. 

Name:	Boeing Bobby.JPG 
Views:	325 
Size:	35.6 KB 
ID:	21966
    Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

  2. #2
    Senior Member Gabriel's Avatar
    Join Date
    Jan 2008
    Location
    Buenos Aires - Argentina
    Posts
    6,893

    Default

    Quote Originally Posted by 3WE View Post
    It's inappropriate to put personal stuff like this up- but his face is obscured, BUT his aircraft is not.- hopefully the mods won't mind.

    Is this suitable for uploading to the photo database?

    PS- Do not over think this, the intent is light humour.

    Click to see full size.
    Click image for larger version. 

Name:	Boeing Bobby.JPG 
Views:	325 
Size:	35.6 KB 
ID:	21966
    Yeah, I know, it is a joke.
    But back to Earth, some pilots could benefit from such kind of reading.
    (And no BB, I am not talking of you or any pilot in particular, remember I am a pilot too)

    --- 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 ---

  3. #3
    Senior Member BoeingBobby's Avatar
    Join Date
    Jun 2009
    Location
    MIA
    Posts
    1,408

    Default

    Quote Originally Posted by 3WE View Post
    It's inappropriate to put personal stuff like this up- but his face is obscured, BUT his aircraft is not.- hopefully the mods won't mind.

    Is this suitable for uploading to the photo database?

    PS- Do not over think this, the intent is light humour.

    Click to see full size.
    Click image for larger version. 

Name:	Boeing Bobby.JPG 
Views:	325 
Size:	35.6 KB 
ID:	21966
    Don't quit your day job just yet there 3. I don't think SNL is looking for you.

  4. #4
    Senior Member 3WE's Avatar
    Join Date
    Jan 2008
    Posts
    4,996

    Default

    Quote Originally Posted by BoeingBobby View Post
    Don't quit your day job just yet there 3. I don't think SNL is looking for you.
    Indeed.

    Better chances of driving a 747.
    Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

  5. #5
    Senior Member Evan's Avatar
    Join Date
    Jan 2008
    Posts
    6,588

    Default

    Quote Originally Posted by Gabriel View Post
    But back to Earth, some pilots could benefit from such kind of reading.
    Truly. How many pilots could accurately describe why a wing generates lift?
    I wonder if you could?
    I read a NASA lesson for 4th graders that decribes the Bernoulli Principle. It taught me that the low pressure on the upper wing surface is the result of both the upper and lower airstream needing to leave the trailing edge of the wing at the same time.
    That has been debunked in wind tunnels however. The upper flow departs the wing far sooner than the lower.
    Then I was taught that the pressure differential is caused by the introduction of the airfoil shape compressing the airflow above the wing, causing it to speed up and the pressure to drop.
    But that has also been challenged. The reasons for that compression have not been convincingly explained.
    So, does anybody actually know what makes an airplane fly...

  6. #6
    Member
    Join Date
    Jan 2008
    Location
    MA, USA
    Posts
    865

    Default

    Quote Originally Posted by Evan View Post
    How many pilots could accurately describe why a wing generates lift?
    Well I think in many people's opinion (myself included), to be a good pilot you do not need to know why a wing generates lift. To be a good pilot, you need to know when a wing generates lift... and when it does not.
    Be alert! America needs more lerts.

    Eric Law

  7. #7
    Senior Member Gabriel's Avatar
    Join Date
    Jan 2008
    Location
    Buenos Aires - Argentina
    Posts
    6,893

    Default

    Quote Originally Posted by Evan View Post
    Truly. How many pilots could accurately describe why a wing generates lift?
    I wonder if you could?
    I read a NASA lesson for 4th graders that decribes the Bernoulli Principle. It taught me that the low pressure on the upper wing surface is the result of both the upper and lower airstream needing to leave the end of the wing at the same time.
    Which is incorrect and can be proven incorrect using fluid-dynamic formulas (not even numeric simulation), fluid-dynamic simulation or wind tunnel testing.
    What did I say about experts not always being right?

    On the other hand, I did read a NASA article debunking the myths about lift generation, and this was one of them.

    Then I was taught that the pressure differential is caused by the introduction of the airfoil shape compressing the airflow above the wing, causing it to speed up and the pressure to drop.
    But that has also been challenged. The reasons for that compression have not been convincingly explained.
    What? Compression above the wing? You obviously need less pressure above than below, compression is increasing pressure, by definition. Where did you see such a thing?

    So, does anybody actually know what makes an airplane fly...
    Yes.

    If you want to look at it macroscopically, the wing accelerates the air down, by the 2nd Newton's law of motion that requires a downward force than the wing effects on the air, and by the 3rd Newton's law of motion that requires that the air makes an equal but opposite force on the wing, that we then call lift.

    If you want to look at it an the level of differentials of volume (that is very very small but still assuming that the fluid is a continuum), then you have the complete Naviere-Stokes equations, which is F=ma applied to a differential volume of fluid, and many simplified versions of Naviere-Stokes where you choose different assumptions (constant viscosity, incomprehensibility, laminar flow, adiabatic compression and expansion, etc...) and get simplified forms of the equation. Bernoulli is one of them.

    Next step is at a molecular level, and then elementary particles. But I will not go into that because I have no idea what equations are used there.

    But yes, we know the physics of the fluids quite well, to the point where we can use the formulas, introduce imaginary objects (boundary conditions) and initial conditions and predict with a surprising accuracy how the fluid will move and what forces will the objects in it be subject to due to the fluid.

    Does a pilot need to know how to do that? No. Does a pilot needs to know the CONCEPTS, the interactions, the cause-effect mechanisms and their consequences? No, you can operate a plane in the same manner that most people operate a car or an iPhone: with zero idea of how it works. But I sustain that pilots that know better are better pilots.

    --- 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 ---

  8. #8
    Junior Member
    Join Date
    Jul 2013
    Posts
    91

    Default

    Isn't this how planes work?

    https://www.youtube.com/watch?v=JYAq-7sOzXQ

  9. #9
    Senior Member 3WE's Avatar
    Join Date
    Jan 2008
    Posts
    4,996

    Default

    Quote Originally Posted by Evan View Post
    How many pilots could accurately describe why a wing generates lift?
    It accelerates a mass of air downward in a rather direct relationship to the AoA.

    I read that somewhere.

    Oh yeah, the Wright Brothers did a bunch of work and found that a little curvature and the hump shape increase things a little over s simple flat wing AND reduce parasite drag...but that's icing on the cake.
    Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

  10. #10
    Senior Member Evan's Avatar
    Join Date
    Jan 2008
    Posts
    6,588

    Default

    What? Compression above the wing? You obviously need less pressure above than below, compression is increasing pressure, by definition. Where did you see such a thing?
    I guess the word is distortion, constriction, caused by the introduction of a shape into the airstream resulting in faster fluid movement across the top and thus lower pressure.

  11. #11
    Senior Member 3WE's Avatar
    Join Date
    Jan 2008
    Posts
    4,996

    Default

    Quote Originally Posted by Evan View Post
    I guess the word is distortion, constriction, caused by the introduction of a shape into the airstream resulting in faster fluid movement across the top and thus lower pressure.
    You have noted that there's a really big hump on the underside of the wing too? I did not learn that from reading.
    Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

  12. #12
    Senior Member Evan's Avatar
    Join Date
    Jan 2008
    Posts
    6,588

    Default

    Quote Originally Posted by 3WE View Post
    Oh yeah, the Wright Brothers did a bunch of empirical work and found that a little curvature and the hump shape increase things a little over s simple flat wing AND reduce parasite drag...but didn't have a frickin' idea why that was.
    Fixed.

    Honestly, I'm torn between Gabriel's up quark explanation and vastr magic one. However, I think the book every pilot should be reading is How Airplanes Don't Fly.

  13. #13
    Senior Member 3WE's Avatar
    Join Date
    Jan 2008
    Posts
    4,996

    Default

    Quote Originally Posted by Evan View Post
    Fixed.

    Honestly, I'm torn between Gabriel's up quark explanation and vastr magic one. However, I think the book every pilot should be reading is How Airplanes Don't Fly.
    Modifications noted...

    Why having something of a hump on top works...why those BIG ASS leading edge slats that shove air UPWARDS and over the wing work...Shoving air UP sure as hell doesn't make lift.

    I have read that 60% of lift is "suction" from the top of the wing...40% because the bottom side shoves air downward.

    Magic, indeed- but from reading Wolfgang Langewiesche, it really doesn't matter.
    Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

  14. #14
    Senior Member Gabriel's Avatar
    Join Date
    Jan 2008
    Location
    Buenos Aires - Argentina
    Posts
    6,893

    Default

    Quote Originally Posted by 3WE View Post
    It accelerates a mass of air downward in a rather direct relationship to the AoA.
    Correct but incomplete.

    F = m*a

    m:
    The mass of air accelerated is the volume times the density.
    The volume is proportional to how much air is flowing around the wing, hence speed.

    hence m = k1 * V * r (V= speed, r = density)

    a:
    The intensity of the acceleration is proportional to the angle that the air is deflected which is proportional to the AoA.
    But is also proportional to the speed: If you deflect air down from 0 degrees to say 10 degrees down, the vertical speed at 10 degrees will be 17% of the horizontal speed.

    Hence, a = k2 * V * AoA

    Finally, L = F = m * a = k1 * V * r * k2 * V * AoA = k * r * v^2 * AoA

    Lift = k * r *V^2 * AoA

    [/splitting-hairs geek]

    --- 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 ---

  15. #15
    Senior Member Evan's Avatar
    Join Date
    Jan 2008
    Posts
    6,588

    Default

    Quote Originally Posted by 3WE View Post
    I have read that 60% of lift is "suction" from the top of the wing...40% because the bottom side shoves air downward.
    So a little bit of Bernoulli, a little bit of Newton.

    L = B + N * V * AoA* ^ M (M= Magic)?

  16. #16
    Senior Member 3WE's Avatar
    Join Date
    Jan 2008
    Posts
    4,996

    Default

    Quote Originally Posted by Gabriel View Post
    F = m*a
    m:
    m = k1 * V * r
    a:
    a = k2 * V * AoA
    L = F = m * a = k1 * V * r * k2 * V * AoA = k * r * v^2 * AoA
    Lift = k * r *V^2 * AoA
    Please explain in plain English OR Espanol BUT NOT Engineer-speak how shoving air up over the front of a wing (and having a bigger hump on top) adds lift.

    As for now, I agree with Evan, the YouTube, the Wright Brothers and my rather flexible human hand held flat out the car window at 70 MILES per hour (and I don't care what that is in KPH, but it's roughly 60 knots).

    Thanks in advance.
    Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

  17. #17
    Senior Member Gabriel's Avatar
    Join Date
    Jan 2008
    Location
    Buenos Aires - Argentina
    Posts
    6,893

    Default

    Quote Originally Posted by 3WE View Post
    Please explain in plain English OR Espanol BUT NOT Engineer-speak how shoving air up over the front of a wing (and having a bigger hump on top) adds lift.

    As for now, I agree with Evan, the YouTube, the Wright Brothers and my rather flexible human hand held flat out the car window at 70 MILES per hour (and I don't care what that is in KPH, but it's roughly 60 knots).

    Thanks in advance.
    I will but later. Stay tuned.

    --- 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 ---

  18. #18
    Senior Member Evan's Avatar
    Join Date
    Jan 2008
    Posts
    6,588

    Default

    Quote Originally Posted by 3WE View Post
    Please explain in plain English OR Espanol BUT NOT Engineer-speak how shoving air up over the front of a wing (and having a bigger hump on top) adds lift.

    As for now, I agree with Evan, the YouTube, the Wright Brothers and my rather flexible human hand held flat out the car window at 70 MILES per hour (and I don't care what that is in KPH, but it's roughly 60 knots).

    Thanks in advance.
    Let me have a whack at this:

    Because something causes the airflow over the wing to speed up, resulting in a lower pressure above the wing, causing the higher pressure below the wing to LIFT the wing upward (That's the Bernoulli part).
    That something is either the shape of the wing itself being present there or a result of the shape of the wing itself resulting in something else that causes the airflow to speed up.
    One theory I've read is that the shape of the wing distorts the fluid tubes in which the air flows above the wing, causing them to constrict, and Bernoulli showed that when you constrict a tube, the fluid speed increases. Counter-argument: When looking out the overwing window, I've never seen a fluid tube and it sounds a lot like magic to me.

    I think Gabriel can solve this one for us.

  19. #19
    Member
    Join Date
    Jan 2008
    Location
    MA, USA
    Posts
    865

    Default

    Quote Originally Posted by 3WE View Post
    Please explain in plain English OR Espanol BUT NOT Engineer-speak how shoving air up over the front of a wing (and having a bigger hump on top) adds lift.
    Allow me: it's mágico.
    Be alert! America needs more lerts.

    Eric Law

  20. #20
    Senior Member BoeingBobby's Avatar
    Join Date
    Jun 2009
    Location
    MIA
    Posts
    1,408

    Default

    Quote Originally Posted by 3WE View Post
    Indeed.

    Better chances of driving a 747.
    Actually, just about the same.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •