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Thread: Attn: Gabriel

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    Senior Member Evan's Avatar
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    Default Attn: Gabriel

    Can you work out the approximate angle-of-attack here:
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    Senior Member 3WE's Avatar
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    Relentless pull ups can have hazards.

    AOA not really measurable from a still pic.
    Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

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    Senior Member Gabriel's Avatar
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    Quote Originally Posted by Evan View Post
    Can you work out the approximate angle-of-attack here:
    The angle of attack is negative a couple of degrees. The zero-lift AoA. Because 0G.

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    Do you think for an aircraft like that that "sustains" 0G, special pickups for fuel and oil are required? Actually when I wrote "oil" I meant in the engines, but the same question probably applies to the hydraulic systems?
    Be alert! America needs more lerts.

    Eric Law

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    Senior Member Gabriel's Avatar
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    Quote Originally Posted by elaw View Post
    Do you think for an aircraft like that that "sustains" 0G, special pickups for fuel and oil are required? Actually when I wrote "oil" I meant in the engines, but the same question probably applies to the hydraulic systems?
    Yes, that kind of thins would be required. I don't know exactly for what systems, but yes. Aerobatic airplanes and fighter jets have that kind of stuff. The Piper Tomahawk doesn't and the engine would stop receiving fuel when you perform zero G parabolas. Been there, done that.

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    Member ATLcrew's Avatar
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    Quote Originally Posted by Gabriel View Post
    Yes, that kind of thins would be required. I don't know exactly for what systems, but yes. Aerobatic airplanes and fighter jets have that kind of stuff. The Piper Tomahawk doesn't and the engine would stop receiving fuel when you perform zero G parabolas. Been there, done that.
    Would a special coffee maker for the crew also be required? Asking for a friend.

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    Quote Originally Posted by ATLcrew View Post
    Would a special coffee maker for the crew also be required? Asking for a friend.

    Now that, is really funny!

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    Senior Member BoeingBobby's Avatar
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    Quote Originally Posted by Gabriel View Post
    Yes, that kind of thins would be required. I don't know exactly for what systems, but yes. Aerobatic airplanes and fighter jets have that kind of stuff. The Piper Tomahawk doesn't and the engine would stop receiving fuel when you perform zero G parabolas. Been there, done that.
    Sorry Gabe, no special stuff on the vomit comet. They do short 20 - 30 second arcs, and it isn't necessary. I have a couple of friends that used to fly them over at Amerijet (727's). I think Elaw was thinking about inverted fuel and oil systems installed on aerobatic aircraft.

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    Senior Member 3WE's Avatar
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    Quote Originally Posted by ATLcrew View Post
    Would a special coffee maker for the crew also be required? Asking for a friend.
    Tomahawk or an Airbus?
    Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

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    Senior Member Evan's Avatar
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    Quote Originally Posted by Gabriel View Post
    The angle of attack is negative a couple of degrees. The zero-lift AoA. Because 0G.
    Well. not yet. We are somewhere between a 1.8G pull up toward a 0G(ish) parabola.

    While I'm 99.99% sure this is a fake image, the angle isn't so far from reality. The actual flight pulls up to 45° of pitch. I make this to be about 53°.

    I actually would love to know what the AoA is at that point before they begin pushing it over into the parabola.

  11. #11
    Senior Member 3WE's Avatar
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    Quote Originally Posted by Evan View Post
    I actually would love to know what the AoA is at that point before they begin pushing it over into the parabola.
    Approximately 1.8 times the 1G AOA.

    A fundamental principle that I never learned from the 172M nor 172P POH, nor type specific training in said aircraft.
    Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

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    Senior Member Evan's Avatar
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    Quote Originally Posted by 3WE View Post
    Approximately 1.8 times the 1G AOA.

    A fundamental principle that I never learned from the 172M nor 172P POH, nor type specific training in said aircraft.
    Ok, since you always take it back there, this one is for you:

    https://airfactsjournal.com/2016/07/...na-172-pilots/

    "The moral to that story might be that the simplest airplane can have complicated moments if flown by a pilot who is unfamiliar with it."

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    Senior Member Gabriel's Avatar
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    Quote Originally Posted by 3WE View Post
    Approximately 1.8 times the 1G AOA.
    Only if your reference 0 deg AoA line is the zero lift AoA.

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    Senior Member Gabriel's Avatar
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    Quote Originally Posted by BoeingBobby View Post
    Sorry Gabe, no special stuff on the vomit comet. They do short 20 - 30 second arcs, and it isn't necessary. I have a couple of friends that used to fly them over at Amerijet (727's). I think Elaw was thinking about inverted fuel and oil systems installed on aerobatic aircraft.
    How do they prevent flame-outs?

    --- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
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    Senior Member LH-B744's Avatar
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    Quote Originally Posted by 3WE View Post
    Relentless pull ups can have hazards.

    AOA not really measurable from a still pic.
    Hello my friend. I can second what you say. Only by chance, I know a little bit more. If we ask female German astronauts who sometimes appear on German TV, and who regularly are passengers in jets which are flown during so called "Zero G" flights,

    the AoA is +45°, during climb, and, -45° (mathematics..) during descent (!). This is the reason why in German these flights are called "Parabelflüge". Now, I don't know how good you are at mathematics.. imho, the English word is "parabola".

    Eine Kurve die bis zum unteren Totpunkt sowohl auf dem absteigenden als auch auf dem darauffolgenden aufsteigenden Ast dieselbe mathematische (dynamische/veränderliche) Steigung aufweist. Die einfachsten Funktionsgleichungen für Parabeln haben den unteren Totpunkt bei den Koordinaten x=0/y=0.
    An den beiden oberen Totpunkten, wo jede Parabel auf gleicher Höhe beginnt und endet ist die potentielle Energie maximal.

    That's what I know from my last mathemathic/physics lessons at high school.. 20 years ago! And when Brazil is through the Carnival weekend, I could try to translate that. Or you are faster.. Very dear greetings.

    PS: My dictionary doesn't have a word for "Parabelflug". But I think I've mentioned the definition: the AoA is 45°, during climb, and also during...
    Are there men on the planet who are paid for 1 hour on the best rollercoaster? - Yes. Jet pilots who perform Parabelflüge. Must be fun on board a LH-B744, of course with female astronauts on board only..
    Potential engergy (cp. kinetic energy), the dictionary knows at least one word, that's what every good glider pilot is able to use, and only a hand full of famous jet pilots, cp. Flight Captain Chesley Sullenberger III.
    -
    3WE.. Mathematics always was a monster, at school, wasn't it. My very last maths lesson must have been something like "Let's calculate the volume of a given chess figure. The function is f(x)= ..., logarithm ... "
    And I wasn't aware that so much has survived in me during the decades, holy s*oul.

    The next step would be "curve sketching part II, bilingual" on a living example, with Kristen Stewart and Blake Lively. But my English isn't good enough for those excursions...
    Last edited by LH-B744; 02-10-2018 at 07:51 AM. Reason: Stupid High school ideas during a Carnival weekend.
    LH also has a intercontinental history, the Hamburg - Düsseldorf - Shannon - NYC route, open since June 1st, 1955.
    A/C type: Lockheed Super Constellation.

    Aviation enthusiast since more than 30 years. Almost a decade here on this platform.

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    Senior Member BoeingBobby's Avatar
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    Quote Originally Posted by Gabriel View Post
    How do they prevent flame-outs?
    Short duration and there are positive pressure boost pumps.

  17. #17
    Senior Member 3WE's Avatar
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    Quote Originally Posted by Evan View Post
    Ok, since you always take it back there, this one is for you:

    https://airfactsjournal.com/2016/07/...na-172-pilots/

    "The moral to that story might be that the simplest airplane can have complicated moments if flown by a pilot who is unfamiliar with it."
    Cool article.

    Are you referencing the Cirrus dude taking off with 40 degrees of flaps?

    For this incident seems like sloppy fundamentals. The one time I flew a Cherokee, I clearly remember searching out the flap indicator. Since even on a 737-236A I think the FCOMQRHPOH calls for checking & confirming flap settings/positions...A321 too?

    PS: Article by "Daddy Rich", former head of Obscure Aviation Typists, ATL crew's top unofficial mentor...
    Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

  18. #18
    Senior Member 3WE's Avatar
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    Quote Originally Posted by Gabriel View Post
    Only if your reference 0 deg AoA line is the zero lift AoA.
    "Only" is your word..."Roughly" is mine.

    I know trig functions are not linear and I assumed not too much airspeed change for the few seconds at push over

    BUT

    at low angles (like less than 16 degrees), angles and 'rise' and lift are ROUGHLY 1:1...yes?

    I anticipate 'the' equation...

    Oh, and I would ALSO guess that the AOA just before push over was slightly less than 16 degrees...
    Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

  19. #19
    Senior Member 3WE's Avatar
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    Quote Originally Posted by 3WE View Post
    ...I anticipate 'the' equation...
    https://en.wikipedia.org/wiki/Angle_of_attack

    Errrrr straight enough that I stand behind my statement....curved enough that Gabeee will stand behind his...
    Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

  20. #20
    Senior Member Evan's Avatar
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    Quote Originally Posted by Gabriel View Post
    Only if your reference 0 deg AoA line is the zero lift AoA.
    This does throw a rock into your theory that an airplane can be stalled at any airspeed and attitude...

    At approximately 225 KT IAS (360 KT TAS, 185 m/s, Mach 0.61), when the aircraft is pitched nose-up 45°, the pilots commence the 0 g parabola. They push forward on the control yoke ("push over") to lower the angle of attack of the wings, which reduces wing lift, and simultaneously reduce power to a level just sufficient to overcome drag. At this point the aircraft's movement approximates that of a ballistic mass rather than that of an aerodynamic craft. The airspeed when the aircraft reaches the top of the parabola, at approximately 34000 ft (10000 m), is 140 KT IAS (245 KT TAS, 130 m/s, Mach 0.43). This is approximately 20 KT below the unaccelerated stall speed of the aircraft, the speed below which the wings cease to produce lift in 1 g flight, because as speed decreases the required angle of attack increases, causing separation of the airflow from the wing. The actual stall speed is equal to the unaccelerated stall speed scaled by the square root of the load factor (load supported by the wings divided by total aircraft weight), which means that in 0 g a stall does not occur at any speed since the wings are not supporting any weight.
    https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2598414/

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