Crash of a...ah...airplane(?) at Willow Run

Discussion in 'Hangar Talk' started by tawood, Dec 14, 2018.

  1. kyleb

    kyleb En-Route PoA Supporter

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    With a short coupled unorthodox configuration like that, compounded by the prop pulling air under the vertical stab, I can see how it might be difficult to predict some of the aerodynamics - particularly pitch stability. We have a business here locally that spent much of the summer two years ago fast taxiing their three surface prototype up and down the runway. They couldn't get the thing to rotate - it was full speed up the runway, brake hard, lather, rinse, repeat, make a minor change, repeat. It took them several iterations before they made a significant change to the incidence angle of the horizontal stab and turned the ground hugging monster into a flightworthy aircraft.
     
    Last edited: Dec 15, 2018
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  2. AKBill

    AKBill Pattern Altitude

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    I imagine the person flying was a test pilot, and was very experienced. Something went trebly wrong, I'm guessing a mechanical failure of some sort. Hope the pilot recovers fully.
     
  3. DaleB

    DaleB En-Route

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    I hope the pilot recovers fully and quickly. And I'm sure the videographer has a promising career in fog machine design. How do you even get a video with everything out of focus, I wonder? Quite a feat.
     
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  4. 3393RP

    3393RP Pattern Altitude

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    I respectfully disagree. No "experienced test pilot" would attempt to fly something that was so obviously unstable.

    I think the thing had an extreme aft cg, and completely inadequate pitch control authority. The pilot got the nose up, and it looks like it gained altitude for the same reason your hand does when its stuck out a car window, not because of aerodynamic lift.
     
    Last edited: Dec 16, 2018
  5. 3393RP

    3393RP Pattern Altitude

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    If trying to keep it on the ground is the reason the pilot cut the throttle, he really needs to work on his reaction time. :eek::rolleyes:
     
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  6. Scott@KTYR

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  7. RJM62

    RJM62 Touchdown! Greaser!

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    Too much Newton. Too little Bernoulli.

    Rich
     
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  8. Kenny Phillips

    Kenny Phillips Pattern Altitude

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    Actually, both of us made the same assumption: that the airplane was designed so that the front wing stalls first. It may not have been the case. Still, the thing zoomed, so the "taxi test" certainly was above any taxi speed I've ever used.
     
  9. Cap'n Jack

    Cap'n Jack Final Approach

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    If the vehicle was configured for driving, maybe the driver couldn't operate the flight controls.
    However, with the wings and canard extended, you'd think it would go into flight mode automatically.
     
  10. jkgoblue

    jkgoblue Pre-takeoff checklist

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    I'd be surprised if there would be some aerodynamic flaw here. In this day and age, there are some many computer aerodynamic design software out there ( heck even X-Plane has a design program) that I find it hard to believe that they missed something so important that would cause the crash. Maybe weight and balance issues or some mechanical issue but not the design of whether the thing could fly.
     
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  11. SkyDog58

    SkyDog58 Touchdown! Greaser! PoA Supporter

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    Interesting thought. I'd like to know the answer to that.
     
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  12. RyanShort1

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    It looks like those canards are a bit asymmetrical, too. Wonder if that would contribute to the roll.
     
  13. Zeldman

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    Well, looks like it is not a flying car....
     
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  14. RJM62

    RJM62 Touchdown! Greaser!

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    Well... I can't imagine why that wouldn't be at least the intended behavior.

    Rich
     
  15. Hank S

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    It may have been designed to stall canard first, but was it built that way? Or did something fail? Or maybe the pilot gave "typical" control inputs rather than more unusual control inputs appropriate for this unusual design?
     
  16. Zeldman

    Zeldman Touchdown! Greaser!

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    Maybe the gust lock was still in place....
     
    Last edited: Dec 17, 2018
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  17. flyingcheesehead

    flyingcheesehead Touchdown! Greaser!

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    I dunno, to me it looks about like someone attempting a soft field takeoff in an Arrow IV (T tail) for the first time!

    Your hand gains altitude when you stick it out of a car window because of aerodynamic lift.

    Or, drag and a vector through your arm if you're doing it wrong. ;)
     
  18. 3393RP

    3393RP Pattern Altitude

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    I'm talking about lots of moving air hitting an angled flat surface. That's not aero lift as I define it.
     
    Last edited: Dec 17, 2018
  19. flyingcheesehead

    flyingcheesehead Touchdown! Greaser!

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    It's a lot of Newton and little or no Bernoulli, but it is most certainly aerodynamic lift.
     
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  20. PaulMKE

    PaulMKE Pre-takeoff checklist

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    There once was a guy named Wilbur...

    Maybe we’re still repeating the learnings of the past 115 years.
     
  21. 3393RP

    3393RP Pattern Altitude

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    I forgot to allow for pedantic dissection of my observations.
     
  22. Hank S

    Hank S En-Route

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    :nono:
     
  23. RJM62

    RJM62 Touchdown! Greaser!

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    That was my observation, especially given the difference in the angles of incidence between the canard and the wing (the latter of whose actually looks slightly negative), assuming the still picture is accurate. Unless the entire canard is movable, the incidence difference alone practically guarantees that Newton would lift the canard long before Bernoulli could catch up on the wing. The main wing's high profile and low aspect ratio further complicates the equation.

    I suspect someone a lot smarter than me put some thought into this, so I feel a bit guilty about second-guessing them. But as an armchair observer with a bit of training in aerodynamics and a bit more in physics in general, I find it hard to understand how that configuration could have produced any result other than what happened in the video -- unless the entire canard is movable, in which case it could have been a combination of operator error and an inherently touchy pitch-control system.

    Rich
     
  24. Capt. Geoffrey Thorpe

    Capt. Geoffrey Thorpe Touchdown! Greaser! PoA Supporter

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    Except that Benoulli's equation is nothing but a special case of Newtons law's and can be derived from Newton's laws given the assumptions of an ideal fluid. If you have one, you have the other.

     
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  25. SkyDog58

    SkyDog58 Touchdown! Greaser! PoA Supporter

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    Ideal fluid? What does beer have to do with it?
     
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  26. RJM62

    RJM62 Touchdown! Greaser!

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    Fair enough. So to be more precise, the deflection lift produced by the canard would occur before the lift due to pressure differential resulting from equal transit time of the air flowing past the wing. Either way, the canard, to me, seems to be providing lift long before the wing can.

    Rich
     
  27. Capt. Geoffrey Thorpe

    Capt. Geoffrey Thorpe Touchdown! Greaser! PoA Supporter

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    Equal transit is a myth. A stupid myth. Airplanes couldn't fly if it were true. Also, the idea that an airfoil is flat on the bottom and curved on the top is a myth. Just go look at any Cherokee. So, any fairy tail that starts out by claiming that the curve on top somehow is different than the flat side on the bottom has to be horsepucky because so many airfoils are not flat on the bottom.

    I'm not sure what you mean by "deflection lift" but the same laws of motion (Newton) and fluid flow (Bernoulli (given the assumptions of non-accelerated,inviscid flow in an ideal gas)) apply to both the upper and lower surfaces of an airfoil
     
  28. RJM62

    RJM62 Touchdown! Greaser!

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    The air flowing past the canard is deflected downwards because of the angle of incidence, thus pushing the canard upwards. Newton's third law, I believe; but you would know better than I. Consequently, long before lift is generated by the main wing's airfoil, by whatever magic of physics it happens, the canard is already providing lift by virtue of its angle of incidence deflecting the air downwards, irrespective of the airfoil itself.

    Rich
     
  29. TFulwider

    TFulwider Pre-takeoff checklist

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    It looks like the canard is trying to fly but the main wing is at/near stall
     
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  30. Capt. Geoffrey Thorpe

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    Not really. The wing and canard will start developing lift as soon as air flow starts moving past. The relative angle of incidence just changes the relative lift distribution. And, yes, all airfoils work by generating a net acceleration of air downward at the trailing edge from the flow over the top and bottom of the wing.
     
  31. Sac Arrow

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    I'm thinking that the plane was intended to be some sort of modified delta wing arrangement where the ailerons also serve as the elevator, e.g. Mirage except for two fixed wings instead of one. But... the plane is still a canard in the sense that the front wing is there to provide some lift. The elevator surfaces probably did not have enough control authority to overcome excessive front wing lift by bad design or improper W/B.

    But I'm also sitting in an arm chair holding a football.
     
  32. tawood

    tawood Pattern Altitude

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    I don't think so...I think it just zoomed upwards, the front wing (or maybe both wings) stalled, and then it did a stall/spin downwards.
     
  33. Capt. Geoffrey Thorpe

    Capt. Geoffrey Thorpe Touchdown! Greaser! PoA Supporter

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    Apparently not. On the news this morning, they mentioned that the pilotish was the company founder Sanjay Dhall.
     
  34. RJM62

    RJM62 Touchdown! Greaser!

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    MS in engineering, private pilot, and has built at least one finished aircraft.

    Rich
     
  35. Kenny Phillips

    Kenny Phillips Pattern Altitude

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    According to a post on their Facebook page, the FAA granted their Special Airworthiness certificate in July.

    "Now we can start testing its flying characteristics. But we will be approaching it cautiously," the post reads.
     
  36. DGlaeser

    DGlaeser Pre-takeoff checklist

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    It is supposed to be designed so that the canard stalls first. Not the easiest thing to do, and this shows what happens when you don't!
     
  37. TFulwider

    TFulwider Pre-takeoff checklist

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    The initial climb looked pretty steep but you'll notice a point where the nose continues upward and the main wing falls through. I believe the canard was producing more lift than expected which caused the sharp pullup and then the main wing stalled before the canard. Once that happened it started to pivot and stalled the canard as well. Just my amateur eyeball though.
     
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  38. Stingray Don

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    I canardly wait for the NTSB report :D
     
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  39. SoCal RV Flyer

    SoCal RV Flyer Pattern Altitude

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    ...and has finished at least one built aircraft. :)
     
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  40. Sinistar

    Sinistar Pattern Altitude

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    I think the Aztek also has wings...but everyone is so fascinated by the fact it can be a campertentsleeperthingy that the wings have not been discovered yet.