2 aero questions about flaps please

Discussion in 'Aircraft Design / Aerodynamics / New Technology' started by cheapracer, Nov 18, 2019.

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  1. Nov 20, 2019 #21

    BJC

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    What changed nearly overnight? Training?


    BJC
     
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  2. Nov 20, 2019 #22

    cheapracer

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    Yup, me 2 wanna know please ...
     
  3. Nov 20, 2019 #23

    Doggzilla

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    Yes, they were trained in how dangerous the spoilers were after the Governor of South Dakota was killed by one in 1993.

    Hardly proof that they aren’t dangerous.
     
  4. Nov 20, 2019 #24

    Doggzilla

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    Oh yes, they also like to flip upside down when one engine fails, because without prop wash on one side it’s spoiler loses authority and controls become asymmetrical.

    Nothing unsafe about that at all.
     
  5. Nov 20, 2019 #25

    BJC

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    Doggzilla:

    All your pronouncements about dangerous designs and evil corporations have raised my curiosity.

    What aircraft have you, and do you, fly?

    Thanks,


    BJC
     
  6. Nov 20, 2019 #26

    Victor Bravo

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    The Helio Courier used spoilers for roll at very low speeds, probably because that airplane could fly at a high enough AoA to get itself into control reversal in some cases. Now before anyone jumps down my throat, I'm pretty sure the ailerons were used for primary roll control and the "spoilerons" were to augment the aileron function in the far nether regions of the flight envelope where the Helio made its living.
     
  7. Nov 20, 2019 #27

    Doggzilla

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    According to the FAA there have been 100 loss of control crashes in the Mu-2. There have been three special SCR reviews in order to improve pilot training involving dangerous control issues.

    38 crashes from losing control on landing and falling short, 24 crashes from loss of control during emergency maneuvers, and another 23 others from non emergency maneuvering. Oh, and 15 loss of control crashes on takeoff.

    https://www.faa.gov/aircraft/air_ce...l_airplanes/cos/mu2_foia/media/Appendices.pdf

    That is 1 out of 7 of all aircraft produced, and 50% of all accidents being caused by control issues.
     
  8. Nov 20, 2019 #28

    cheapracer

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  9. Nov 20, 2019 #29

    Tiger Tim

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    Exactly, a requirement for type-specific training as well as BFRs to be done on type.

    Thread drift alert:

    Doggzilla the Governor of SD died tragically, along with everyone else on board, due to a chain of events beginning when a Hartzell propeller hub failed and a blade was thrown through the cabin in cruise. The resulting imbalance tore up the engine mounts and twisted the nacelle sideways on the wing. The crew recognized the loss of pressurization before recognizing the engine (and structural) failure and were in a steep descent before recognizing that one engine wasn’t developing power. When they tried levelling off they discovered that due to the extensive damage the plane couldn’t maintain level flight. The weather at the time was IFR with embedded CBs and while ATC kept vectoring them direct to their destination they kept steering south to avoid cells (and before someone says it had to do with single engine controllability these turns were towards the good engine). Due to technological limitations at the time, ATC only had the weather in their sector which was equally bad everywhere and didn’t know that just a few dozen miles to the south it was VFR. The plane continued to slowly sink over what was essentially endless farmland and the radar track shows that just before reaching the ground it made a shallow turn of a few degrees before straightening and hitting a silo about fifteen feet above ground. It’s believed that the pilots saw the dark shape of the silo in the fog and believed it to be a road or other suitable landing surface. Ultimately it was the plane losing control after losing a wing to the silo that resulted in the deaths of all on board. Had the plane been forty feet to either side they would have landed in a field and at worst lost the one passenger who had been hit by the propeller blade. That’s what happened to the governor of SD, as told to me by one of the investigators.

    Interestingly, a short time later and certainly before the investigation of the above accident was concluded, there was another Hartzell hub failure but this time on a VFR day. Again a prop blade penetrated the fuselage and the nacelle was wrenched over far enough that the plane was slowly sinking. Never sit in the prop-adjacent seat of anything, I guess. Anyways, the pilots were able to land at a nearby airport and the plane was repaired and returned to service. There was also an AD issued for the propeller hubs that grounded the fleet until compliance.

    I’m not offended by discussing basic safety information, in fact the exact opposite. Misunderstanding or misidentifying a cause is in many ways as bad as ignoring the problem. That’s what I was seeking to inform on here.
     
  10. Nov 20, 2019 #30

    Tiger Tim

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    It seems I was writing while you were posting. Yeesh, who hurt you Dogg?
     
  11. Nov 20, 2019 #31

    wsimpso1

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    Stepping in as a Moderator:

    First - Tone it down immediately.

    Second - This is a thread on flap design. Stay on flaps or even make note that a particular flap scheme has had a troublesome past, you are good. Let's keep it civil and towards the topic.

    Billski
     
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  12. Nov 20, 2019 #32

    Tiger Tim

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    Never!! Just kidding, I said my bit and if anyone has any other questions on it feel free to start a new thread.

    More importantly, Cheapie:
    Perhaps, but I’d lean more towards a benign and predictable stall rather than chasing the lowest number. For that, flaps inboard effectively gives more washout the more flap you extend.

    Might be interesting to explore though I do question if filtering the airflow through all sorts of structure wouldn’t negate any benefits. Fowler flaps should be as easy as just designing your hinges so the pivot is a few inches below the wing.

    In any case, I’d be curious to know if any of this matters that much on a light, middle-of-the-envelope airplane built by a first-timer in a garage. Beyond marketing, of course.
     
    Last edited: Nov 20, 2019
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  13. Nov 20, 2019 #33

    mcrae0104

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    Wow, he got a promotion?
     
  14. Nov 20, 2019 #34

    cheapracer

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    Yes, as Topaz mentioned and others alluded to. That is a satifactory position on the subject, thanks again to all for their inputs.

    As for the flap idea, just brainstorming is all, gotta ask, gotta learn, they go hand in hand.

    Maybe simply take air from a high pressure source, base of the windscreen for example, and pipe it into the wing . A lot simpler than it might sound.
     
  15. Nov 20, 2019 #35

    Victor Bravo

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    Blown flaps probably need higher than just ram air pressure to do something useful. The F-4 and other airplanes use engine bleed air, which has farmore pressure and flow than just ram air.

    Using ram air alone, the ducting losses would be the issue. Slotted Fowler flaps have the "duct" right there, so there is little loss of pressure, flow, velocity, etc. A 6 or 10 foot tube from the cowling or windshield would be a different story IMHO.
     
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  16. Nov 21, 2019 #36

    Tiger Tim

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    Since we have a thread on flaps, how about the drawbacks of full span flaperons? As I recall there are some reasons not to but I seem to have forgotten what they were...
     
  17. Nov 21, 2019 #37

    Aesquire

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    If you have a proper nose radius on the flap and design of the cove you should have attached flow over the flap, increasing lift & effectiveness. Slotted flaps work fine. The wing probably ( except in very slick laminar wings ) has a fairly thick boundary layer that far back.

    Just leaking air between wing & flap just adds drag & hurts lift. So optimum is to seal the gap, or go to a proper slotted flap. No free lunch.

    Or you can always go with the Junkers style flapperons like a Kitfox. That simplifies wing construction, and increases the effectiveness of the flaperons, at the price of parasitic drag.

    The stall improvement with less deflection towards the tips, with a multi (2) section flap/aileron also improves folk control, as previously posted by smarter folk.

    Has anyone tried a flaperon that is allowed to twist, and to end, that is controlled at both ends for roll ( flap lever up ) and the flap lever biasing the flap down on the onboard end? Torsional twisting the flaperon to give effective washout?

    It seems feasible, but there's a little voice in the back of my head screaming about flutter and the need for a smarter engineer than me to design it. ??

    Has this been tried?

    Ok, now the voice is telling me to play Samantha Fish. :)
     
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  18. Nov 21, 2019 #38

    Victor Bravo

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    Yes, Samantha is pretty darn good, but I'm a Susan Tedeschi and Derek Trucks fan thru and thru.

    Derek's guitar slide looks like it would be juuust about the optimum leading edge radius for a slotted Fowler Flap.... :)
     
  19. Nov 21, 2019 #39

    Aesquire

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  20. Nov 21, 2019 #40

    cheapracer

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    The guy that invented Autocorrect died recently, he had been very I'll.
     

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