Glider Performance Limitations or Requirements

Discussion in 'Aircraft Design / Aerodynamics / New Technology' started by jedi, Sep 24, 2018.

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  1. Sep 26, 2018 #61

    jedi

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  2. Sep 27, 2018 #62

    lr27

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    How many Tee Dee .010's does it take to make a sailplane take off. ;-)

    Also, how long to clean off the wings after the flight?
     
  3. Dec 13, 2018 #63

    Starflight

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    Don't laugh...I have eight Mitsubishi TL-43 "Viper" two strokes waiting to 'commit' aviation on a Canadian legal UL. Bought brand new @ $159 each on sale (43cc roto-tillers).
     
  4. Dec 13, 2018 #64

    lr27

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    Somewhere, I've seen a picture of a sailplane with 8 or 12 electric model airplane motors installed, albeit crudely. I can't remember the name, but I think it was British and made from a bunch of honeycomb panels, possibly intended as a kit. The motors were just an experiment, I think. The sailplane is a green color, which ought to help distinguish it from all the white ones.
     
  5. Dec 13, 2018 #65

    mcrae0104

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    It was on the NASA website.
     
    Last edited: Dec 13, 2018
  6. Dec 13, 2018 #66

    lr27

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    Pretty sure it WASN'T anything to do with NASA, but one guy's experiment. Not sure why NASA would be interested in a rare (or maybe one off?) British sailplane as an experimental subject. Definitely not the X-57 or anything like it, but an actual sailplane.
     
  7. Dec 13, 2018 #67

    Pops

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    Local man built this for Bellanca in the 1970's along with all the factory tooling. NASA leased it for about a year for testing. I did a little work on it putting it together before the test flying started. Had a one off engine build for this airplane by Cont.
    Picture of the SkyRocket ll taxing out for one of the test flights. Tail of my Ercoupe got in the way of the picture.
    Set some world records and taken to OSH and the EAA ignored it.
    https://en.wikipedia.org/wiki/Bellanca_Skyrocket_II
     

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  8. Dec 13, 2018 #68

    Topaz

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    Coming back to a point in this discussion, I'd like to confirm my interpretation of the regs. I've bolded a few key items.

    The two posts above outline an interesting potential conflict for my project. It seems that there is distinction made between "glider" and "powered glider" in the LSA definition, however that distinction is not defined at all. "Powered glider" appears only these two times - sub-sections (7) and (8) - in the entirety of §1.1, and nowhere else.

    "Powered gliders" can have auto-feathering props, but not otherwise in-flight adjustable by the pilot. A "glider" (but not a powered glider?) can have retractable landing gear.

    If we presume that, for purposes of LSA and like Part 23, "powered glider" = "glider" in all meaningful terms, one could have a motorglider with retractable landing gear (subsections 11 and 13) and an auto-feathering prop (subsection 8) but its V[SUB]NE[/SUB] will be limited to 120 kts (subsection 3). Under normal ways of defining V[SUB]NE[/SUB], that would limit V[SUB]max[/SUB] to rather well below 120 kts and be a definite performance limitation in powered cruise.

    If we presume that "powered glider" != "glider" under §1.1, but instead "powered glider" = "airplane", you could have an "airplane" that can have a V[SUB]max[/SUB] of 120 kts, but it must also have fixed landing gear (subsection 11) and cannot have an auto-feathering prop (subsection 7), regardless of how long the wings are.

    I'd really like to have an LSA "powered glider" with an auto-feathering prop, retractable landing gear, and a V[SUB]max[/SUB] of 120 kts. If I'm reading the regs right, it doesn't seem like that's possible, but then there's so much left unsaid in §1.1 and definitions are not clear.

    Does anyone know of an AC or other publication that clarifies this situation?
     
  9. Dec 13, 2018 #69

    BJC

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  10. Dec 13, 2018 #70

    Topaz

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    Sounds like they're taking the "powered glider" = "glider" definition, and accepting the 120 kt V[SUB]NE[/SUB]. That would be consistent with how the rest of US type certification standards handle the situation.

    Interesting, then, that their Specifications page lists cruise at 110 kts. They have to be "gaming" the V[SUB]NE[/SUB] definition to make that work. It's just a "placard" value, not the actual structural limitation of the aircraft. You normally wouldn't want a 10 kt spread between normal cruise and V[SUB]NE[/SUB].
     
  11. Dec 13, 2018 #71

    BJC

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    That also is one of my conclusions; the aircraft’s Vne is set to meet the classification, not as 0.9 Vd. Would also note that lots of E-AB advertise, and achieve, cruise speeds right at Vne.


    BJC
     
  12. Dec 13, 2018 #72

    Hot Wings

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    (13) - To me since a powered glider is a subset of glider anything allowed for a glider is also allowed for a powered glider, unless specifically exempted. Using this reasoning I would think a retractable gear would be allowed for a powered glider - Certified, LSA or EAB.

    The 120 kt speed limit? That is just paper work, much like the 1320# weight limit. I can't believe the FAA would enforce infractions of the speed limit any more than they do the weight limit. We all know there are LSAs with a paper limit of 1320 that can easily handle more safely.

    Is there any real advantage to having an LSA motor glider over an EAB motorglider. other than not having to get a conventional motorglider rating?
     
  13. Dec 13, 2018 #73

    Topaz

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    So, hypothetically speaking, of course, I could be within "giggle factor" range of "legal" if I have a "powered glider" LSA with retractable gear, an auto-feathering prop, and a V[SUB]c[/SUB] in the 100-105 kt range, provided the POH says V[SUB]NE[/SUB] is 120 kts.

    That's what I'm hoping, of course.
     
  14. Dec 13, 2018 #74

    Topaz

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    For some of us, yes. I've never had a denial of a medical certificate, but it's been more than ten years since I've held one. Despite the fact that I firmly believe that I am quite capable of safely operating an aircraft in this performance range and that my regular medical doctors concur, one or more of my medical conditions is on the FAA list of things that makes a special issuance a mountain of paperwork heavier than my projected motorglider, possibly with re-checks annually. For the amount and kind of "under-power" flying I want to do, it's just not worth it to get a special issuance. So I'm stuck out in the cold on the new PPL "medical" regs.

    Also, the oddities of Sport Pilot and LSA mean that it seems unlikely a self-launch endorsement is needed for an LSA motorglider. Still trying to check on that.

    The airplane I'm designing (and I need to get my design thread caught up with this) falls neatly into LSA with really no effort or compromise. Might as well take advantage of the freedom from paperwork that LSA and Sport Pilot provide.
     
    Last edited: Dec 13, 2018
  15. Dec 13, 2018 #75

    BJC

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    I’m not clear on how to legitimize the retractable gear.


    BJC
     
  16. Dec 13, 2018 #76

    Hot Wings

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    So if I'm getting this all straight your plan is to get the Sport Pilot and then lateral to your EAB the motorglider and fly it under SP regulations and limitations? I can see the advantage of that path. It may be cheaper and quicker than adding a motorglider endorsement to a glider license.

    Once you have some time in your motorglider as an LSA how much trouble would it be to use that to get the motorglider endorsement as a glider pilot? This would remove all of hte LSA restrictions. My read of the regulations indicates if you could find a CFIG that would sign you off for solo after observing you - legally - flying your LSA motorglider you would then have a very inexpensive path to getting the motorglider endorsement to your glider license.

    Edit:

    Lock the gear in the down position until you get the motorglider endorsement. Once that is in hand simply remove the locking mechanism and go fly your retractable gear motorglider. This method removes all doubt about the legality of a retractable gear LSA motorglider.
     
  17. Dec 13, 2018 #77

    Topaz

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    If, for LSA, "Powered Glider" = "Glider", as it does with Part 21.17 (CS-22), then since LSA "gliders" are allowed to have retractable gear, LSA "powered gliders" should also be allowed to have retractable gear. The example of the Phoenix shown earlier suggests that this identity of definitions is likely the way things are being interpreted. (Although I do wish I had a more-extensive reason for believing that!)

    Exactly. I don't want to derail this thread any more than I already have, but suffice it to say that while finding a CFI-G to do the training and endorsement around here isn't hard or expensive, finding an actual motorglider in the area that can be rented out for the purpose is both hard and very expensive. The only one of which I know between Santa Barbara and San Diego is a Stemme S-10 that rents out for this purpose at $250/h, plus fuel. Instructor time is additional. Assuming the FBO in question demands the full extent of the required endorsement training, that's about $1,500 before you get into the "Well, I think you need a little more practice at..." additional hours. Unsubstantiated rumor has it that the FBO involved is "like that."

    The other thing that was really the deciding factor is that having an SP cert also lets me go beyond motorgliders into regular sportplanes. I couldn't do that PPL-SEL, because of the level of work I'd need to expend to get a special issuance on a 3rd class. My current project is a motorglider because of the synergy between really liking soaring, and the need for span with the small installed power. Having an SP cert means I can rent LSA's from the area FBO for sport flying, and build a non-motorglider sportplane someday when I get that itch.
     
    Last edited: Dec 13, 2018
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  18. Dec 13, 2018 #78

    proppastie

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    Items I have read on this thread I am ignorant of. I thought glider pilots do not need a medical, and even if they have been denied can "self certify"......A person can take lessons in his own EAB aircraft.....so once you have your powered glider built you can get your power launch endorsement/sign-off in that .
     
  19. Dec 13, 2018 #79

    Topaz

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    Glider pilots (including powered-glider pilots) do not need a medical certificate. A person can take lessons in his own two-seat E-AB, and could get a self-launch endorsement in that E-AB, presuming its Airworthiness Cert identifies it as a "Glider."

    My project does not have two seats, and having a self-launch endorsement to a PPL-G certificate does not allow me to fly sportplane LSA's without a 3rd class medical cert.

    There's also the chicken-and-egg problem of flying off the test period for the E-AB motorglider before one can take up a CFI (as a passenger) in order to get lessons in it. Paying someone else to fly off the 40h for you could get very spendy.
     
    Last edited: Dec 14, 2018
  20. Dec 14, 2018 #80

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    Here, in their own words, is the FAA’s rational:

    BJC
     
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