Quickie review of the XPlusOne VTOL aircraft (tl;dr avoid for now)

I was a Kickstarter backer of the XPlusOne VTOL aircraft, and I was able to get it for $199 as an early backer.  Now it's sold at the regular price of $1,549 for the version I have, which has no autonomy (it's got a simple MultiWii controller board), or for $2,199 for an autonomous version with Pixhawk. 

I haven't tried the second, more expensive, one, but have now flown the first enough to give a quickie review. 

The promise of VTOL aircraft is that they can take off and land in small space like a copter, but have the duration and lifting power of a plane. Sadly, this is usually more true in theory than in practice. VTOL aircraft like these are often called "sporks" for a reason. As copters they are hard to control, unmaneuverable, and prone to being blown around by the wind due to the sail-like cross-section.  As planes, they tend to be draggy due to the extra props and as a result also struggle with the wind. 

The XPlusOne is no exception. As a copter it tends to be blown about by the wind, as you might expect for something with four (!) wings. But the idea is that you keep it in copter mode just long enough to take off and and land, and do most of your flying in plane mode. Unfortunately, the XPlusOne is even worse at that mode. Since it has no control surfaces, all steering is done with differential thrust of the props, which is sluggish. And since it has no tail surfaces, it has to fly with a very high angle of attack at all but top speed, which means that it's always close to a stall and thus also prone to being affected by wind. 

But the main problem is that, as you can see in the video below, it's almost impossible to see its orientation. With four wings in a symmetrical configuration you just can't tell which side is up, or left from right. Combine that with very poor control authority and you'll be lost within seconds of going into plane mode. 

I just got a few flights in, and only one in plane mode, before this caught up with me. On a windy day, i went to a safe altitude to transition, went into plane mode and I immediately lost orientation. So I switched back into copter mode and the winds at that altitude just blew it away to parts unknown in seconds. I was never able to regain enough control to bring it home. Bye-bye XPlusOne. Had I paid $1,549 I would have been pretty annoyed. 

In short, I think the XPlusOne is unflyable in its base MultiWii configuration. That said, a proper autopilot might have done a much better job than me and the Pixhawk-based version with GPS might have been able to bring it back against the wind in a way that I, from the ground, could not.  But I'm not going to pay $2,200 to find out. 

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Comment by Tom Pittenger on January 2, 2016 at 4:38pm

but but but The Sharks loved it!

Comment by Joe Renteria on January 2, 2016 at 4:42pm
Too bad, for some reason I was feeling optimistic about that one...

3D Robotics
Comment by Chris Anderson on January 2, 2016 at 4:53pm

Here's an article about what the company is doing post-SharkTank

Comment by james sowell on January 2, 2016 at 5:12pm

glad ur mad about it should b the challenge of 2016 2 crack ta code ; )

Comment by Rob_Lefebvre on January 2, 2016 at 5:15pm

Funny, in the comments of that article is a guy promoting his perpetual batteries.


Comment by Ryan Beall on January 2, 2016 at 6:22pm

google gave up on this method and I suspect this will be more of the same.  quad shot etc.  

Comment by Gary Mortimer on January 2, 2016 at 9:22pm

Amazingly NG has just been awarded a $93 million deal to build a contra rotating version flying wing for DARPA. It does have control surfaces as well though which might help. Getting blown about when in the hover is always going to be an issue if you want a big enough wing in order to become super efficient in forward flight. Without that I think a helicopter is always going to win until those perpetual batteries arrive for multi's ;-)

I started down the Shark Tank Drone building path, and have built in a Kickstarter delay to my project (Christmas) So far I have built and flown a copy of the VertiKul 2 which I think has great potential and cleverly removes the need for funky transitions. It works but like Chris discovered the lack of conventional control surfaces is well, different. It unsettles me as the platform keeps the traditional quad copter whole heap of trouble if there's an engine out. Conventional surfaces would let it return in time for tea and medals in the event of issues. I'm sure code could handle it. As a side note I got my first KK2 board to try OpenAero VTOL with this game and I was amazed how big and by that heavy the board is.

My absolute favourite tailsitter that seems to be able to cope with wind at take off and landing is from Aerovel. Its a Tricopter....

Expect to see more of these this year as there are several under 333 exemptions now.

I'm going to try a copy of the NG Tern next as I have a contra rotating prop setup from HK to try exactly that. I still don't expect glittering performance. In the event of engine failure the thrust is along the same vector and the wing will just become a single instead of twin engined wing. I thought it might be fast for FPV racing.... Any flying wing that is over powered has almost vertical performance.  Is VTOL really worth all the faff...

Oh BTW Chris I thought you were going to dominate the current T3 with XPlusOne http://diydrones.com/profiles/blogs/t3-the-vertical-one

3D Robotics
Comment by Chris Anderson on January 2, 2016 at 9:50pm

Gary: I've been practicing with my FireFly6 instead. It's much better than the XPlusOne, mostly because it's actually a proper airplane. I'm optimistic that I can put in a decent entry. 

Comment by Michael Burmeister on January 3, 2016 at 4:53am

Hey Chris, Since you had to put your FAA number on your XPlusOne someone should find it and be able to return it to you....

Comment by Damian on January 3, 2016 at 5:04am

Seems like DARPA is not concerned too much with the wind resistance of tail sitters; Perhaps military GPS with cm resolution is good enough to maintain the static hover; this is TERN:



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