Page 37 of 40 FirstFirst ... 27 31 32 33 34 35 36 37 38 39 40 LastLast
Results 541 to 555 of 587

Thread: Tailless Aircraft - Reflex and other design issues

  1. #541
    Registered User
    Join Date
    Oct 2005
    Location
    Evans Head Australia
    Posts
    621
    Likes (Given)
    5
    Likes (Received)
    203

    Re: Tailless Aircraft - Reflex and other design issues

    The autorotational moments are greater in high AR wings, in a condition where one wing is stalled and the other wing is unstalled or partly stalled, the forward component of lift (same force that drive autygyro blades) on the unstalled wing causes a rotation around the neutral axis, if the yaw control of the vertical tail is insufficient to counteract that autorotational component, the aircraft will enter a spin. Naturally the greater the AR the larger the rotational moment.
    This is not to say that all high AR aircraft enter irrecoverable spins, constructors do their level best to design this unwanted feature out of their aircraft. They are not all together successful because dozens of pilots are killed every year from stall/spin accidents.

  2. #542
    Registered User
    Join Date
    Jul 2014
    Location
    Rochester, NY, USA
    Posts
    2,195
    Likes (Given)
    33
    Likes (Received)
    857

    Re: Tailless Aircraft - Reflex and other design issues

    BBerson, I don't think LAR craft need long landing gear because of aspect ratio. It's prop clearance that drives gear length. A UFO, scaled up slightly for the weight, could use a direct drive VW derived engine, like the Sonex, with relatively shorter tricycle gear.

    The Sonex gear is also shorter than optimum, for high AOA landings, the designer accepted the compromise of lower drag & cheaper over lowest practical landing speed.

    That's on top of the compromise of lower static thrust with the smaller, direct drive prop, but better high speed performance.

    Tail gear flying wings tend to have high deck angles just because they are shorter than tailed aircraft of roughly the same wing area. LAR flying wings logically could be built with a lower deck angle than high AR flying wings, but other factors , like prop clearance in level attitude dominate in the choice.

    Also there are "That's just stupid looking" limits to deck angle. A plane that points up 60 degrees from horizontal while it's parked is obviously going to be less quick to accelerate on a take off run than one that has less drag and a better thrust vector. I

    The V-173 is a poor example for gear length, in that it had huge props for the installed power, rather like the WW1 fighter replicas with PSRU equipped VW engines. And was intended as the proof of concept for the V/STOL naval carrier fighter.

    The Arup series and most other LAR craft don't have such long gear. And while several claimed and achieved darn good take off performance, STOL wasn't the big selling point. Simplicity, cabin volume, cute factor, parking, etc. are usually the main bullet points in the sales flyer.

    Thanks for the links to previous LAR discussions. I'd forgotten one of my all time favorites! The deltoid pumpkin seed. ( I recommend the book )

    https://www.amazon.com/dp/B005EHQEWW...ng=UTF8&btkr=1

    https://en.m.wikipedia.org/wiki/AEREON_26

    The Aereon 26 did not use helium for lift, it was the proof of concept for the SHAPE & aerodynamics of the design. A blend/compromise between a sphere ( maximum volume for weight ) and a delta wing ( for stability and lift ) the lifting body was to be the father of practical airships. The mission, as is often the case, was for missionary organizations to haul heavy cargo ( like generators & farm equipment ) to primitive clearings in the jungle etc. ( the ecological niche now occupied by CH801 home builts, among others ) http://www.zenair.com

    The Aereon concept isn't dead!
    https://www.lockheedmartin.com/en-us...d-airship.html
    But the original is far prettier, and more efficient! Obviously lower drag.

    I wonder if B. Wainfan was inspired by the Aereon in his Facetmobile design? It's not in any way a copy, but form follows function, and a wing/internal volume optimization is going to evolve into a similar shape. I'd bet he was aware of the Aereon, and he has stated the facet approach was a simplified and aerodynamic test bed idea. ( vs. rounder, curved shapes )

    Likewise, the Lockheed airship seems inspired by Soviet missile submarines, which iirc, were inspired by Japanese submarine aircraft carriers. Or the Curtis C-46 & Boeing 377.

  3. #543
    Registered User Himat's Avatar
    Join Date
    May 2011
    Location
    Norway
    Posts
    2,737
    Likes (Given)
    1710
    Likes (Received)
    636

    Re: Tailless Aircraft - Reflex and other design issues

    And another long thread about slow deltas:
    http://www.homebuiltairplanes.com/fo...806&highlight=

    The Verhees delta thread:
    http://www.homebuiltairplanes.com/fo...ad.php?t=12923
    (Could be more than one, but this one I could find.)

  4. #544
    Registered User BBerson's Avatar
    Join Date
    Dec 2007
    Location
    Port Townsend WA
    Posts
    10,712
    Likes (Given)
    1621
    Likes (Received)
    1901

    Re: Tailless Aircraft - Reflex and other design issues

    If you want the full 45° braking then the landing gear must be capable and maintained on roll out.. Actually the higher aspect ratio Kasperwing video uses the 45° braking without the long gear because there is no tail. The UFO has a long tail.
    But I noticed from the Zimmerman graphs that after about 30°-45° the stall is sharp. Not good if the pilot stalls. With or without a spin if a sharp stall occurs on takeoff or landing then the radical pitch down may not have room to recover. I don't see safety in operating near a sharp stall at 45°. A soft stall at 25-30° makes more sense to me.

  5. #545
    Registered User
    Join Date
    Oct 2005
    Location
    Evans Head Australia
    Posts
    621
    Likes (Given)
    5
    Likes (Received)
    203

    Re: Tailless Aircraft - Reflex and other design issues

    I imagine that you would get a fair idea that something bad was going to happen as the angle of attack started to exceed 30deg.

  6. #546
    Registered User BJC's Avatar
    Join Date
    Oct 2013
    Location
    97FL, Florida, USA
    Posts
    8,309
    Likes (Given)
    4629
    Likes (Received)
    5309

    Re: Tailless Aircraft - Reflex and other design issues

    Quote Originally Posted by rotax618 View Post
    The autorotational moments are greater in high AR wings, in a condition where one wing is stalled and the other wing is unstalled or partly stalled, the forward component of lift (same force that drive autygyro blades) on the unstalled wing causes a rotation around the neutral axis, if the yaw control of the vertical tail is insufficient to counteract that autorotational component, the aircraft will enter a spin. Naturally the greater the AR the larger the rotational moment.
    This is not to say that all high AR aircraft enter irrecoverable spins, constructors do their level best to design this unwanted feature out of their aircraft. They are not all together successful because dozens of pilots are killed every year from stall/spin accidents.
    Do you mean AR or span?


    BJC

  7. #547
    Registered User
    Join Date
    Oct 2005
    Location
    Evans Head Australia
    Posts
    621
    Likes (Given)
    5
    Likes (Received)
    203

    Re: Tailless Aircraft - Reflex and other design issues

    Autorotation requires a stalled condition and an asymmetry of lift from one side of the wing compared to the other, it doesn’t matter what the span is. Zimmerman said there was little or no tendency for autoration in AR less than 3.

  8. #548
    Registered User
    Join Date
    Oct 2005
    Location
    Evans Head Australia
    Posts
    621
    Likes (Given)
    5
    Likes (Received)
    203

    Re: Tailless Aircraft - Reflex and other design issues

    Here are a couple of alternate LAR ideas I was playing with over 10 years ago, a “Facetedmobile” with folding wings and a “Smoothmobile”.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

Name:	F67B53FA-724B-4A91-89CE-B792943A8AE7.jpg 
Views:	29 
Size:	43.4 KB 
ID:	78368   Click image for larger version. 

Name:	ACA2AF0A-D255-4172-808B-D705D7A8CCBC.jpg 
Views:	29 
Size:	56.9 KB 
ID:	78369  

  9. Likes delta, Sockmonkey, Himat liked this post
  10. #549
    Registered User BBerson's Avatar
    Join Date
    Dec 2007
    Location
    Port Townsend WA
    Posts
    10,712
    Likes (Given)
    1621
    Likes (Received)
    1901

    Re: Tailless Aircraft - Reflex and other design issues

    The Sonex Onex is almost within inches of the same dimensions of the Facertmobile turned sideways.
    The Onex is 16' 5" x 20' 9" https://en.m.wikipedia.org/wiki/Sonex_Aircraft_Onex
    The Facetmobile is 15' X 19' 6" http://www.wainfan.com/pavreport.pdf
    So, just as compact with the wings out. Yet the Onex has folding wings and can reduce to 8 feet in seconds.

    The Onex could be fitted with wide chord wings to reduce the AR from 5.1 to AR4. This would reduce the stall speed and shorten the takeoff roll yet retain the high top speed mostly. With the flaps at 45°, the approach must be as steep as anyone could want, I think.
    Could be built much lighter in fabric like an early light Ercoupe with fabric wings.
    .

  11. #550
    Registered User
    Join Date
    Oct 2005
    Location
    Evans Head Australia
    Posts
    621
    Likes (Given)
    5
    Likes (Received)
    203

    Re: Tailless Aircraft - Reflex and other design issues

    If you were to re-engineer the Onex to build it from nature’s composite (wood), fabric covering, add vortex generators (may have to sacrifice a couple of knots), increase the length of the UC, you could land quite slowly. Unfortunately it would still stall at about 14deg AOA and if you had the controls a little bit crossed when it did stall it will probably spin. Never the less it would be closer to STOL. There are probably better candidates that have already been designed for wood construction that could be equiped with folding wings, VGs, more takeoff and landing rotation angle.
    Although it wouldn’t look ‘cool’ a Himax fuselarge and tail with a 12ft disk wing, a modern day Nemeth parasol, could fold down the 3’ of wing tip for transport and storage, bit longer sprung UC - powered by a 503 or equivalent would certainly be STOL, stall/spin resistant, cheap and easy to build.

  12. #551
    Registered User
    Join Date
    Oct 2005
    Location
    Evans Head Australia
    Posts
    621
    Likes (Given)
    5
    Likes (Received)
    203

    Re: Tailless Aircraft - Reflex and other design issues

    It may be possible to build a Part 103 ultralight version of a circular wing aircraft. 1st step would be to build a very light 12’ diameter wing frame using thin alloy tubing for rib frames, the spar could be very light if the wing was cable braced, a king post at the centre of the wing, a lightweigh frame similar to the frame under a Kasperwing for the pilot with attached lifting wires. The engine, either light 2 stroke or industrial Vtwin of about 30hp, attached to the front of the wing. Will attempt to draw a sketch.
    Would be novel, and stallproof and spinproof like the Kasperwing.

  13. #552
    Registered User
    Join Date
    Apr 2014
    Location
    Flint, Mi, USA
    Posts
    1,483
    Likes (Given)
    390
    Likes (Received)
    391

    Re: Tailless Aircraft - Reflex and other design issues

    Quote Originally Posted by rotax618 View Post
    Although it wouldn’t look ‘cool’ a Himax fuselarge and tail with a 12ft disk wing, a modern day Nemeth parasol, could fold down the 3’ of wing tip for transport and storage, bit longer sprung UC - powered by a 503 or equivalent would certainly be STOL, stall/spin resistant, cheap and easy to build.
    Heck, you could just make the whole disk removable.

  14. #553
    Registered User mcrae0104's Avatar
    Join Date
    Oct 2009
    Location
    Colorado / USA
    Posts
    2,692
    Likes (Given)
    3153
    Likes (Received)
    1770

    Re: Tailless Aircraft - Reflex and other design issues

    Quote Originally Posted by rotax618 View Post
    The idea that you can dive a conventional planform aircraft toward the ground and flare for a short landing completely ignores the laws of physics...
    Could you please explain this in a little more detail for everyone who had done precisely what you described above? Perhaps it it in your definition of dive?
    ​simplify.

  15. #554
    Registered User BBerson's Avatar
    Join Date
    Dec 2007
    Location
    Port Townsend WA
    Posts
    10,712
    Likes (Given)
    1621
    Likes (Received)
    1901

    Re: Tailless Aircraft - Reflex and other design issues

    I never dove at the ground before the landing flare but did something similar. Doing multiple glider tows with my Piper Cherokee, I would come over the threshold on the right side about 100 feet high to cut the tow rope loose without catching in the trees.
    With full flaps, engine at idle, and about 60 mph and with a quick side slip to the left and nudge forward and "fall" the 100 feet in a second. A quick flare and I was down and returning for another tow. Did it hundreds of times. I wouldn't need or want to "fall" any steeper than that. Just requires coming in slow with full flaps.

  16. #555
    Registered User
    Join Date
    Oct 2005
    Location
    Evans Head Australia
    Posts
    621
    Likes (Given)
    5
    Likes (Received)
    203

    Re: Tailless Aircraft - Reflex and other design issues

    If you turn height into speed you need some way of slowing down quickly to land short, it is usually not possible to pull full flap unless your Vfe is very high.

Similar Threads

  1. Discussion Thread: The design of a tailless flying wing
    By Aerowerx in forum Aircraft Design / Aerodynamics / New Technology
    Replies: 479
    Last Post: August 2nd, 2017, 02:37 PM
  2. X-4 Tailless Design
    By rv6ejguy in forum Aircraft Design / Aerodynamics / New Technology
    Replies: 9
    Last Post: January 25th, 2017, 12:25 PM
  3. Tailless Aircraft Configuration Poll
    By Aerowerx in forum Aircraft Design / Aerodynamics / New Technology
    Replies: 40
    Last Post: November 17th, 2015, 03:35 PM
  4. Tailless Aircraft and Crosswind Landings
    By Aerowerx in forum Aircraft Design / Aerodynamics / New Technology
    Replies: 11
    Last Post: July 23rd, 2015, 05:26 PM
  5. Tailless Design: Natureal Frequency and Stability
    By Aerowerx in forum Aircraft Design / Aerodynamics / New Technology
    Replies: 18
    Last Post: January 3rd, 2013, 09:45 AM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •