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I saw this video and was wondering how he is controlling the plane:
It looks like he only has ailerons. It does look like he is shifting his body weight. Is that the answer? If so, that's pretty surprising! But I guess it's like a hang glider?
Does anyone know how you should shift your body to increase/decrease pitch, and increase/decrease yaw?
The ailerons in most flying wings can also move together up and down, then working as an elevator. This is called an "elevon", combining both words as the device is combining both functions. Since flying wings mostly use reflex airfoils, loads on the rear part of the wing tend to be small and the force to keep elevons at their right deflection is small, too. In case of the SB-13, they are pre-loaded by a small, adjustable spring but otherwise free-floating. In this case, however, it could be that they only work as ailerons.
When used for pitch control, elevons must move up and down together on both sides. This means they will be freely floating and must be held in position by some force. It would be easier to cross-link them so they only can move against each other, and then they only work as ailerons.
The airplane, called OpenSky M-02, is the brainchild of Tokyo University of the Art professor Kazuhiko Hachiya and has been built by Aircraft Olympos of Japan. OpenSky M-01 was a lighter, unpowered version.
As Louise Hose writes on Kitplanes:
Hachiya designed the project and is the only pilot to fly the resulting “Open Sky M-02J”. He started with a hand-launched, scale model to test the airfoil characteristics. Once he was satisfied with the basic design, he partnered with aeronautical engineer Tota Ueno of Olympos Company in Tokyo to scale up to a glider capable of carrying one person…Hachiya himself. The glider, first flown in 2006, was launched from the ground by teams of people pulling a bungee cord. Once satisfied with its flight characteristic, Hachiya and Ueno worked to find the “right” engine to add as the powerplant. Between 2010 and 2013, they were doing high-speed taxi tests and working through issues…particularly powerplant and regulatory issues. They ultimately decided to use the NIKE jet engine made by AMT Netherlands which produces 176 pounds force. The jet was designed and mostly used in target drones.
At least the model couldn't be steered by weight shifting, and looking at the harness of the pilot, his capacity for weight shifting is rather limited. My impression is that weight shifting is primarily used for ground control. If you watch the YouTube movie, it becomes apparent that he is barely capable of controlling the direction on the ground, and has to lean to the left on take-off to prevent it to escape the runway. Also, his movements are more sideways than back-and-forth. The control surfaces hardly move, but show linkages on the bottom side, so they are moveable. If you look closely, you can see pulleys on the left and right of the pillow Hachiya-san is lying on, and as @quietflyer says, they should control the elevons, but he adds his weight to help controlling both pitch and roll.
Louise Hose of Kitplanes again:
To date, Hachiya has made about 150 “jump” flights and 70 circling flights. He has flown it up to nearly 500’ agl but believes it can fly much higher. (Airspace restrictions in Japan have prevented him from trying to fly higher.)
This is the M-02J, a jet plane modeled after the Mehve "glider" (actually a futuristic antigravity plane) from "Nausicaä of the Valley of the Wind". And, yes, the pilot controls pitch primarily by shifting his weight forward and back, while the ailerons are only used for roll control.
You can control any airplane through weight shift, that's not limited to hang gliders. It's just not practical for larger aircraft, but for little one-man planes, it's perfectly reasonable.
To answer the last question, it works just like a hang glider. The plane's pitch and roll can be controlled by shifting your weight in the direction you want to turn. Yaw isn't controlled, you just have to rely on the natural aerodynamics of the aircraft to keep your nose pointed in the direction of flight.
The Kitplanes article suggests that the pilot's left-right (and fore-and-aft?) body movements shift the small platform or cradle that he is lying on, which pull on the control cables that actuate the ailerons or elevons, whichever they are. No joysticks appear to be involved. We lack an authoritative answer as to whether pitch control is primarily/ partially via elevons or solely weight-shift, but the former seems more likely. Even if pitch control is mainly through elevons, the effect of even a slight fore-and-aft shifting of pilot's shifting body weight may not be negligible on a tailless aircraft with little or no wing sweep.
Note that the system is reminiscent of the hip cradle used in the Wright brothers' earliest aircraft, at least as far as roll control goes.
Yaw control is a non-issue with many well-designed aircraft. For example, very few hang gliders have had yaw control surfaces.
I think I see how the elevon controls are designed. The pulleys by the pilot's waist look independent, except for being connected to the sides of the "pillow" the pilot rests his torso on. So that creates linkage between controls for side-to-side or forward-backward movement.
The pilot moving his body (and thus the pillow) left or right will pull on one and create slack in the other, creating opposite changes in elevon position. This gives roll control.
Near the end of the video, after landing (e.g. at 5:00) we see a good angle of the "pillow" positioned so the cord attachment points are as close as they can get to the pulleys. So the pull on each cord is at a minimum. This is presumably downward deflection of both elevons since the pilot moved to this position after touchdown. Moving left or right could probably lower one a bit further (while raising the other). (In that same shot, we can see the elevons in frame as well, and it looks like they're not far down, but this is a bad angle. Maybe they simply don't go very far down, or there's some kind of internal linkage, or I'm missing some other control input.)
But in flight, I think the pilot generally keeps his body position farther back, so both ropes are pulled out some. This pulls the elevons up to a neutral or higher position, leaving room for pitch up or down by moving the pillow back or forward, respectively. (Along with the pilot's weight, which also provides some pitch control directly, apart from moving the elevons).
In this position, moving left and right will still slacken one and tighten the other, creating the opposite movements you want for roll control.
During landing (4:22), we have a camera angle from above/behind the pilot that shows both ropes and pulleys while he's moving, controlling pitch while maintaining some right-roll. Note how he pushes backward (tensioning the ropes) to flare a bit just before touchdown.
To make roll control work in the correct orientation, I think the right rope must be connected to the left elevon, and vice versa. Because moving your body (including bodyweight) right slackens the right rope. But to roll right, you need to deflect the right elevon up. If it was right rope => right elevon, either roll or pitch control would have to work against the pilot's weight shifts, depending on whether pulling deflected upward or downward. That would be terrible and unintuitive, and we can see from the video that he's moving and/or leaning right to roll right, and back to pitch up.
This is my explanation of how I think it's designed, not based on any statements from the designer. (But thanks to the other answers for their observations that shaped my thinking, especially @quietflyer for spotting the pulleys.) I think it's a plausible design for the controls, compatible with sanity and all the observations I could make from the video, but possibly not the actual design.
Certainly body-weight shifts are part of the controls; as @quietflyer says we can't be sure how much of the control authority comes from body-weight vs. elevons. But it looks like there is good control of the elevons for both pitch and roll.
2:50 in the video is a decent side view of exercising some pitch control (near the ground so it provides a good reference). We definitely see the pilot shift his body forward and back.
It's hard to see the far elevon. I can't tell whether it's moving as much (in the opposite direction) as the left aileron goes up and then down. If not, that would prove that these are elevons which can also do pitch control, not just linked ailerons. I think that's the case from what would make sense for the rope/pulley design, but I'm not 100% sure.
