Ultralight from scratch, knowledgable and reasonable input requested

Discussion in 'Aircraft Design / Aerodynamics / New Technology' started by P65F001, Sep 22, 2018.

Help Support HomeBuiltAirplanes Forum by donating:

  1. Sep 24, 2018 #61

    P65F001

    P65F001

    P65F001

    Member

    Joined:
    Sep 22, 2018
    Messages:
    12
    Likes Received:
    0
    Location:
    Oregon/USA
    Well, what are some of those rules of thumb? Im just looking to get this angle kinda close to reality after all. Enough ground clearance so that it shouldn't touch the ground during mostly normal operations, that kinda stuff.
     
  2. Sep 24, 2018 #62

    proppastie

    proppastie

    proppastie

    Well-Known Member

    Joined:
    Feb 19, 2012
    Messages:
    3,710
    Likes Received:
    1,077
    Location:
    NJ
    Get Faa Glider Criteria
     
  3. Sep 24, 2018 #63

    lr27

    lr27

    lr27

    Well-Known Member

    Joined:
    Nov 3, 2007
    Messages:
    3,216
    Likes Received:
    465
    Clearly, your design should have as many well streamlined wheels as possible. Keep in mind that one wheel right behind the other has less drag and can bridge holes. With tri gear, that would give you six wheels! (and, by 103-7, more allowable horsepower) Then, you could have a couple of struts that are just over four feet long. This might not look entirely like rule beating, if your design has long wings. Some sailplanes have had short struts. Careful study of 103-7 will reveal other things you can do. For a glider, you could have a fairing over the engine that had to be opened, exposing the engine, before the ignition would work. Careful design would be required to make it safe. I THINK that would be legal.

    At some point you'll need to sit down, consult relevant textbooks, and do a bunch of calculations.
     
  4. Sep 24, 2018 #64

    jedi

    jedi

    jedi

    Well-Known Member

    Joined:
    Aug 8, 2009
    Messages:
    1,759
    Likes Received:
    395
    Location:
    Sahuarita Arizona, Renton Washington, USA
    Sorry, off topic again and in reviewing prior posts I have no idea why the above comment was made. This has hit one of my buttons and I need to reply. If anyone has a follow on comment, please start a new thread with details and a heads up as a reply to this post.

    Show me where you find "FAA Glider Criteria". As far as I can tell FAA Glider Criteria do not exist except to reference Part 23 standards. There are no specific certification requirements applicable only to gliders.

    The FAA references European standards but does not require compliance. They (the FAA) leave the field wide open. If I remember right Rutan's Space Ship One was listed as a motor glider. It is difficult to find references to glider in EAB aircraft. The airworthiness certificate only says experimental. The category is hidden in the supporting paperwork. IMHO many EABs should be motor gliders. No medical required. LSA can have retractable gear and variable pitch prop. On a ramp check the FAA inspector can not tell what he is looking at.

    Let's not all go crazy less the world learns the secret and "fixes" things as happened with EAA and ultralights.

    Seriously, I want to know what FAA glider limitations others have found, not options but specific requirements.

    FAR Part 1 Definitions. Glider means a heavier-than-air aircraft, that is supported in flight by the dynamic reaction of the air against its lifting surfaces and whose free flight does not depend principally on an engine.

    If any single engine plane I fly does depends principally on an engine for support, I get extremely nervous and uncomfortable unless I have a parachute. I want the wing to be my principle means of support. The engine just lets me go a little farther from a landing site.

    There is additional guidance available but it is mostly left over from the 30's since no "modern" gliders have been certified for manufacture in the US. Schweizer was smart enough to not mess with old regulations.
     
    Last edited: Sep 24, 2018
  5. Sep 24, 2018 #65

    lr27

    lr27

    lr27

    Well-Known Member

    Joined:
    Nov 3, 2007
    Messages:
    3,216
    Likes Received:
    465
    Try "Basic Glider Criteria". A web search will find it right away. Actually, the other search terms find it quickly also, but maybe that's a recent upload by proppastie. Be nice to him.
     
    jedi likes this.
  6. Sep 24, 2018 #66

    pictsidhe

    pictsidhe

    pictsidhe

    Well-Known Member

    Joined:
    Jul 15, 2014
    Messages:
    6,720
    Likes Received:
    1,770
    Location:
    North Carolina
    The pdf of the FAA Basic Glider criteria that I have is dated 1962. It's as good a guide as any for designing a 103. The European CS-22 is another document worth looking at and is up to date. There is also the FAA part 23 pre-2017 you could use for guidance. a 103 doesn't need to meet any of those standards. But I'm not the only one here who is following one of these standards to try to ensure that wings won't snap off... HBA has lost one extremely prolific builder to TLAR engineering, We are hoping not to repeat that.
     
  7. Sep 24, 2018 #67

    jedi

    jedi

    jedi

    Well-Known Member

    Joined:
    Aug 8, 2009
    Messages:
    1,759
    Likes Received:
    395
    Location:
    Sahuarita Arizona, Renton Washington, USA
    Thanks, useful info but advisory, not regulatory. Many references are made to European requirements of span loading and weights for gliders. I do not believe these limitations apply in the US.

    My search turned up the Basic Glider Criteria Handbook.The "Basic Glider Criteria Handbook" deals with guidance for design and structural issues. My concern was with regulations and requirements as has been discussed with regards to FAR 103. The Basic Glider Criteria Handbook does not refer to regulations nor contain minimum specifications for gliders such as sink rate, L/D, stall speeds, wing loading, or span loading. I'm cool here. Apparently we were discussing two different topics.

    This reply is copied to a new thread titled "Glider Performance Limitations or Requirements" for those who wish to make additional comments.
     
  8. Sep 24, 2018 #68

    BJC

    BJC

    BJC

    Well-Known Member

    Joined:
    Oct 7, 2013
    Messages:
    9,499
    Likes Received:
    6,262
    Location:
    97FL, Florida, USA
    The Glider, by Stelio Frati, is a good introduction into the basics of glider aerodynamics and structure. It was published in 1946, so it focuses on wooden structures.


    BJC
     
    proppastie and mcrae0104 like this.
  9. Sep 24, 2018 #69

    radfordc

    radfordc

    radfordc

    Well-Known Member

    Joined:
    Feb 5, 2008
    Messages:
    1,223
    Likes Received:
    490
    Interesting technique. I would have thought that lugging the engine with increased prop load would lead to high CHTs. I never flew with an in-flight adjustable prop...only ground adjustable. Increasing prop pitch usually led to lower EGTs and higher CHTs.
     
  10. Sep 24, 2018 #70

    jedi

    jedi

    jedi

    Well-Known Member

    Joined:
    Aug 8, 2009
    Messages:
    1,759
    Likes Received:
    395
    Location:
    Sahuarita Arizona, Renton Washington, USA
    At WOT (Wide Open Throttle) the engine is running on the the full throttle enrichment feature. Reducing the throttle setting would increased EGTs. CHT was not an issue in that instillation at cruise speed and Sun N Fun temperatures.
     
  11. Sep 24, 2018 #71

    BBerson

    BBerson

    BBerson

    Well-Known Member HBA Supporter

    Joined:
    Dec 16, 2007
    Messages:
    11,859
    Likes Received:
    2,254
    Location:
    Port Townsend WA
    Basic Glider Criteria does list performance criteria, sink (5fps) and Minimum climb angle (17 to 1) for a motorglider. This criteria is for Type Certification. A person applying for Type Certification can use Basic Criteria or other Criteria as they wish to propose to the FAA.

    For EA-B it is useful as guidance.
     
    Last edited: Sep 24, 2018
  12. Sep 24, 2018 #72

    jedi

    jedi

    jedi

    Well-Known Member

    Joined:
    Aug 8, 2009
    Messages:
    1,759
    Likes Received:
    395
    Location:
    Sahuarita Arizona, Renton Washington, USA
    Found it on page 129, thanks. Again this is advisory, not regulatory.

    The 17:1 reference is not L/D glide ratio. It is the minimum "power on" climb angle.

    Note: 5 ft/sec. converts to 300 ft/min. and applies as advisory only to motor gliders.
     
    Last edited: Sep 24, 2018
  13. Sep 24, 2018 #73

    BBerson

    BBerson

    BBerson

    Well-Known Member HBA Supporter

    Joined:
    Dec 16, 2007
    Messages:
    11,859
    Likes Received:
    2,254
    Location:
    Port Townsend WA
    Corrected, thanks.
    I thought there was requirement of 7 to 1 landing angle with dive brakes, but couldn't find it.
     
  14. Sep 24, 2018 #74

    Topaz

    Topaz

    Topaz

    Super Moderator

    Joined:
    Jul 30, 2005
    Messages:
    13,628
    Likes Received:
    5,279
    Location:
    Orange County, California
    Moderator Note: Gentlemen, please return this thread to the original topic of the OP's design and design questions. This side-bar discussion about certification standards, etc. has no bearing on the discussion at hand. Jedi has started a new thread on this topic, and you should continue your side-bar there, please.

    Further off-topic replies in this thread will be moved or deleted.

    Thank you.
     
    jedi likes this.
  15. Sep 25, 2018 #75

    P65F001

    P65F001

    P65F001

    Member

    Joined:
    Sep 22, 2018
    Messages:
    12
    Likes Received:
    0
    Location:
    Oregon/USA
    Hey guys,

    So this week I plan to put together a test tail boom if that length shown in my renderings looks about right. Assuming it is, around what weight should I be able to hang off the tail end of it while rigidly supporting the side that attaches to the plane? I dont doubt that there is specific calculation that could be done; I am just looking for ballpark number however.
     
  16. Sep 25, 2018 #76

    proppastie

    proppastie

    proppastie

    Well-Known Member

    Joined:
    Feb 19, 2012
    Messages:
    3,710
    Likes Received:
    1,077
    Location:
    NJ
  17. Sep 25, 2018 #77

    P65F001

    P65F001

    P65F001

    Member

    Joined:
    Sep 22, 2018
    Messages:
    12
    Likes Received:
    0
    Location:
    Oregon/USA
    17.5 sq ft area times 12 lb/sqft gets me 210 lbs. Two booms, so 105 lbs each. An 11 foot beam supporting 105 lbs on the end seems very doable, just need to reinforce the root a bit.
     
  18. Sep 25, 2018 #78

    jedi

    jedi

    jedi

    Well-Known Member

    Joined:
    Aug 8, 2009
    Messages:
    1,759
    Likes Received:
    395
    Location:
    Sahuarita Arizona, Renton Washington, USA
    The assumption here is that the load is split evenly between the two booms. This is not always the case. There are many reasons this may not be true. Propeller effects and turbulence are good examples. Boeing lost a B-52 and crew by not looking at the asymmetry in flight test data*. A 1.5 safety factor may be wise in this case.

    * High speed low altitude test. Average of horizontal stabilizer loads were within limits. Testing continued to failure. Review of the test data showed right side and left side loads were frequently over design limits. HS departed the aircraft.
     
  19. Sep 25, 2018 #79

    proppastie

    proppastie

    proppastie

    Well-Known Member

    Joined:
    Feb 19, 2012
    Messages:
    3,710
    Likes Received:
    1,077
    Location:
    NJ
    calculation wise yes....testing no, unless you plan on to market it, in which case you should test to destruction to CYA. There is an A-symmetric spec/test but I forget what it is or where it is at this point. However testing the moment of the vertical tail at the same number 12#/sq ft, will give you a good torque test.
     
  20. Sep 25, 2018 #80

    pictsidhe

    pictsidhe

    pictsidhe

    Well-Known Member

    Joined:
    Jul 15, 2014
    Messages:
    6,720
    Likes Received:
    1,770
    Location:
    North Carolina
    part23 appendix A specifies 100% loading one side, 65% the other side as an asymmetric load. I have a vague memory of seeing something like it in CS-22, too.
    If you are going to design your own ultralight, you really should consider chewing all the way through one of the standards/guides. You don't have to follow them, but, you are almost certain to find stuff that you haven't thought of. It's worth doing just to see what you need to be thinking about.

    I rceently paid $5 delivered on Amazon for a copy of FAR AMT 2015 which has the 'good' part 23 as well as a lot of other parts. So does 2016, but I think that was over double the price! I have CS-22 and glider criteria in pdf. But I like to work from paper books.
     
    mcrae0104 and BJC like this.

Share This Page

arrow_white