I took another shot at designing a fixed wing. I don't have any serious plans with it yet. Just a design experiment like my last one wich turned out to be all looks and no efficiency. This one is a flying wing design. And again, I have no clue and need some expert advice. As of now it has a 2.5 meter wingspan run by a 13" pusher prop. I think that may be too small? The cutout for the motor is 40mm, I thought that may cover all the size motors that it could run on. It has an internal front mounted tilt camera similar to my quad design. The slit in the front allows a 17° tilt up and 90° tilt down. I posted lots of pics because it's kinda hard to perceive its form due to its streamlined shape. But don't let the shape fool you, it has a payload bay thats 10cm at its deepest point, 20cm wide and 45 cm long.
One thing I'll give conventional airframes is "handling qualities". This is a bit of "amateur" aeroengineering analysis, but I believe the tail extension can help "hold" the aircraft orientation at slower speeds and hold off "stalls" for much longer. Look at the Kadet Sr. -- it is a trainer and has a HUGE tail and is impossible to stall or spin. Contrast that with a big high aspect ratio flying wing and if you get close to a stall with one of those you are snapping and going around at least twice before you can fly out of it.
I could see that in "full scale" aviation people being concerned about their personal margin of safety when they are on board. Also flying wings can be a lot "pitchier" which could affect your personal comfort level.
I can see quite a few engineering challenges with fitting a human in a competition size flying wing glider.
My only point is there are many many considerations in aircraft design beyond how long you can stay aloft on how much energy.
A spin is not something that a plane just enters, it has to be provoked. The typical scenario is that as the speed decrease you apply more and more elevator to keep the nose up, and after a while you also have to apply ailerons to keep the wings from tipping over. At some point this will not be possible any longer, and the plane will enter a deep stall/spin. The thing is that this is how many people (wrongly) try to do low speed landings with scale airplanes, and it's pretty much the worst time possible to get into a stall.
John: I don't disagree with anything you've said. But speaking from personal experience, I believe a high aspect ratio flying wing (efficient aspect ratio) will stall/snap quicker and with less provocation than a similar but conventional airframe with a tail. The existance of the tail helps hold the wing in place longer, thus requiring more provokation to get to a spin. UAV's tend to be high wing loading, and that combined with a high aspect ratio wing and no tail can lead to very small margins and a very violent and nasty snap that can take minimum of two 360 degree rotations to fly out of.
Thus most "successful" :-) aircraft are a balance of factors including safety and nice handling qualities -- even competition aircraft have some compromises.
Ahh.. We are in agreement. When I refereed to scale airplanes and spin in my previous post I was thinking of 3D airplanes that allows for some pretty 'creative' landing approaches. I totally agree that a wing will snap quicker and more brutally then a traditional taildragger.
A spin is obviously a stalled condition, an asymetrical stalled condition that persists due to poor design and/or pilot error.
Many "Flying Wings" have a swept and twisted wing. The sweep tends to cause the boundary layer at the tips to become thick and "Tired"... but the twist reduces the AOA of the tip. keep in mind, if a stall initiates at the tip, the lift center is moved forward thus causing an INCREASE in AOA!!
A flying wing with Vertical stabilizers at the wing tips can be more prone to getting "Stuck" in a spin, or at least more difficult to recover because the "Fins" are in a flow field that can be parallel to the local flow.... whereas a center fin (as is typical of a conventional configuration) is more directly impeding the autorotation via higher AOA relative to the spinning motion.. or at least a drag force (if the vertical is also stalled) opposing the rotation.
The horizontal tail, (though influenced by the downwash from the wing) is hardly large or effective enough to prevent a wing from dropping...(left or right)
Unless heavilly AP'd, the lack of a tail arm with a horizontal tail results in a plane with poor pitch damping.... It may be balanced, and it may be stable, but the damping is poor.... and it is high damping that make a plane feel benign (at at an extreme like the flippers are too small!!)
Stalling though is a function of AOA.. bottom line.... if a plane can unexpectedly change AOA to some extreme before the pilot/AP can correct.. there can be a stall....
hard to imagine a more benign spin/snap than this!! lol
Imagine being able to stop the autorotation, but keep it stalled and recover with the nose never dropping below the horizon!!
Great project please continue with it. I see it has created great discussion on the post regarding design type etc. These guys obviously know way more than me regarding type layout etc. all I can add is that they are all after different requirements.
I am from the UK, we are allowed to fly under licence (if you are charging for your services as apposed to hobby flying). Check out http://eurousc.com/ which has several links to regulatory requirements for EU countries. Generaly they all operate a VLOS requirement, staying within 500m radius and 150m altitude although it does vary from country to country, no doubt when the US gets over its paranoia it will be along similair lines.
Most of the commericialy avialable UAS systems available (i.e. offering airframes as opposed to offering services) offer flying wings. Now I dont know, but from former posts I can assume that this is because of ease of operation for none skilled pilots etc. here are but three examples:
http://www.gatewing.com/ (last time I checked (2011) cost of around €50,000)
http://www.sensefly.com/ (last time I checked cost (2011)of around €14,000)
http://www.smartplanes.se/ (last time I checked (2011)cost of around €20,000)
(prices were for fully operational turn key systems and include operator trainiing (but not licencing)).
Yes I know these are all sub 2m wingspan, but you get the gist. Stay with the wing for operator/transport/user ease of operation.
You need to define your requirements for the airframe first. Project requirements, payload, flight time, etc. I dont want to put my sub $10k flash lidar camera ( http://www.advancedscientificconcepts.com/) into a $800 airframe only to have some over enthusiastic FAA official confiscate it because I was flying it 2.5km from where I launched it.
The reality is most of us are going to stay within line of sight (ish) and be carrying a pretty light camera load, with a flight time of around 60 mins. I think what you have come up with so far fits that bill, please continue.
Beautiful design and rendering work, Eric. I for one appreciate the blending of the aesthetic and the functional, and think you've done an excellent job. Any progress on the design/build? I hope some of the comments here have not discouraged you from proceeding. Your planform is not overly exotic, meaning there are plenty of people around with experience designing and flying similar wings. It will certainly fly and probably very well once you incorporate some of the key features already mentioned earlier.
Does anyone know if this aircraft has been set into production?
I would consider buying one :)
@Trung Nguyen: The comments are very motivating and not discouraging at all. I'm currently working on the structural integrity. Things are moving slow because my day job consumes so much of me. And then theres the Agrion Quad Project. So I right now I'm just working away on design important points.
@Tommy Larsen: The plan is to finish the designs then find a partner or partners with the experience and know-how to collaborate on building the prototype. I may finance the prototype and first production with crowdfunding. I feel me sticking to what I do best (design and software development) is in the best interest of the project.
Thanks to all for your interest, insight and comments. Have a legendary 2014!!! ;-)