Tail mounted propellor

Discussion in 'Aircraft Design / Aerodynamics / New Technology' started by Staggermania, Aug 16, 2014.

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  1. Aug 19, 2014 #21

    autoreply

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    When max power is genset power, a hybrid is simply the worst compromise. More weight, more complexity, more cost.

    Size for 50 hp cruise, 250 hp take-off power and it starts to make a lot of sense.
     
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  2. Aug 19, 2014 #22

    DaveK

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    It did have a bunch of crashes. Someone I knew through EAA who was a test pilot was test flying one for another member of the chapter and was severely injured in a crash. Lost an eye and broke his back if I remember correctly. My recollection (this was 15 years ago) was there were issues with the horizontal tail size and interactions with engine power, but again this was a long time ago.
     
  3. Aug 19, 2014 #23

    Topaz

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    My understanding of the Seawind is that there's nothing inherently dangerous about the airplane but, like so many of the higher-priced homebuilts, it needs some specialized type-training, and is not at all forgiving of poor handling by the pilot. Pay attention to the airplane, or pay the price. We've seen the same issues with the Lancair IV, Questair Venture, and other high-performance aircraft. Pilots get into them without really having the necessary training and experience, and Bad Things ensue.
     
  4. Aug 19, 2014 #24

    autoreply

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    Don't fully agree. While the earlierst Lancairs might have been marginal, the IV, the Venture, Glasair SX200 etc are hot, but well within the grasp of a sharp pilot. The reports from experienced test pilots on the Seawind were borderline at the very best.
     
  5. Aug 19, 2014 #25

    Topaz

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    Huh. That's not what I recall, at least for the developed version. I remember the early protos definitely having some issues, but I'd thought they'd largely been resolved.
     
  6. Aug 19, 2014 #26

    Staggermania

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    True enough. But someday you could take that gen-set out for the last time, and drop in a a fuel-cell or the newest hyper-efficient batt-pack.

    Yeah, I agree. Perhaps not the most practical ideas, but
    throw enough spagettie at the wall, however, and some is gonna stick:)
     
  7. Aug 19, 2014 #27

    rv6ejguy

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    At some point, the Seawind Certification project was moved up to Canada to try to get approval here since we have a reciprocal agreement with the FAA. I recall reading an article by the test pilot involved a number of years back now. It's a bit fuzzy but I seem remember spin testing, elevator forces and longitudinal trim with power changes were areas they were working on. Here is a link to some info: ARCHIVED - NRC Aerospace Flight Research Laboratory assists Seawind with 300C certification flight-test program - News - NRC-CNRC

    Some more here: Archives

    It's been a long hard road as we've seen many times before.

    I scratch built a free flight model of this aircraft back in 1972. Thought it was cool. Flew very poorly but it flew.
     
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  8. Aug 20, 2014 #28

    plncraze

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  9. Aug 20, 2014 #29

    Topaz

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  10. Aug 20, 2014 #30

    rv6ejguy

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    The Spectra was the one I built the model of actually. The Seawind is virtually an identical layout (much better looking and larger) which came out many years later. The Spectra had to be the inspiration for the Seawind.
     
  11. Aug 20, 2014 #31

    plncraze

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    I figured that was what you had built. Every time you think somebody has a new idea you see a picture or drawing that shows there is not that much new in aviation.
     
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  12. Aug 20, 2014 #32

    BBerson

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    Britton-Norman Trislander
     

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  13. Aug 20, 2014 #33

    Dan Thomas

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    And it had several structural issues with the tail, too. As should have been anticipated, hanging a 600-pound engine and prop on the fin, making that fin absorb maybe 1000 pounds of thrust, shaking that fin with lots of vibration, bending it with torque reaction, twisting it with gyroscopic precession, and hard landings stressing the aft fuselage with all that weight back there.

    Looks cool? Not to me, as a mechanic and amateur engineer. No fun for the mechanics that have to keep it airworthy.

    Dan
     
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  14. Aug 20, 2014 #34

    BBerson

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    Yeh, but the Trislander only has one third of its total engine weight hanging from the tail.
    And one engine failure with three engines results in 66% thrust remaining and not as off center as a twin.
    I think the twin Islander was more popular.
     
  15. Aug 20, 2014 #35

    Himat

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    One drawback with the tail mounted propeller I haven’t seen raised this time is the weight and balance difficulties with a small aeroplane. With a tail mounted engine and propeller, the pilot and passenger must be moved forward relative the centre of gravity. A larger change in CG with the number and size of occupants then follow.
     
  16. Aug 21, 2014 #36

    Doggzilla

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    I dont think you've realized this, but a standard pusher prop would work much better with your chosen powerplant. The main disadvantage of most pushers is that they are in turbulent flow, and going from this huge engine to a small prop just mangles the flow behind the aircraft. With a hybrid powerplant... you can basically make it as aerodynamic as a sailplane... a nice slender rear fuselage with a vastly more laminar flow.

    Having laminar flow really does improve performance drastically. Many powered sailplanes have extremely small engines, and those engines wouldnt be even remotely as aerodynamic as a hybrid system. A hybrid pusher would probably have pretty impressive performance.
     
  17. Aug 21, 2014 #37

    bmcj

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  18. Aug 21, 2014 #38

    BBerson

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    Notice the Seawind prop is almost at the horizontal CG above the wing, it isn't really at a typical distant tail. The Seawind tail moment arm is sort of short. The fin is quite large to compensate.
     
  19. Aug 21, 2014 #39

    jedi

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    I do not recall the name, off hand, but there is an impressive sailplane (300 kt Vne) with a tail mounted Koneg engine. Problems were the limited provisions for increased porpeller diameter and inability to reengine due to weight limitations. The Konig is no longer being manufactured.

    Compact Radial Engines has the rights to the Konig but production is not economical. The sailplane had a three cylinder version and a four cylinder version was developed but with increased weight.

    One of the Sea Wind design issues is the excessively high thrust line. Sea Bee and many other designs have the fuseladge cutout to allow a lower thrust line. Thurston Duck/Teal and follow on designs, Colonial Skimmer, Lake etc. seem to have solved that problem to a successful degree. A part of the solution is to move the engine (and therefore the CG) forward and thus have a longer tail arm for increased tail volume. With a tail mounted engine you can not move the CG forward by making the Tail longer. This is where the twin boom option gets considered.

    An electric tail mounted engine with batteries mounted forward would be a game changer in this configuration.
     
  20. Aug 21, 2014 #40

    BBerson

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    Windex
     

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