26/02/2013 'First Hop' of Project Skyflash

The Tests began with a detailed briefing after the weather clearance on 25/02. We discussed the procedures and what problems might appear. Most dangerous would be a sudden lift-off without me beeing prepared for this event. To prevent this we decided once again not to use the V-tail, thus taking my ability to climb out of ground below speeds of 100kph. Second critical factor was the proper function of the gear with running engines. Or, more detailed, can the gear cope with the ground when pushed by engines and can the engines run without problems when in vibration due to the bumpy ground. In theory the big wheels and the suspension would eliminate most of the bumps. The low center of gravity would make the control for the pilot easy and prevent a flip-over or ground loop. Tests with the plane beeing towed by a car seemed to confirm this. But to be absolutely safe we decided to begin the day with a slow run to about 25kph down the runway.

On the early morning of February 26th we arrived at the airport and build up the base station right at the end of the runway. After checking the airplane I was warmed up by our physiologist. Right after this I was connected to airplane for the first time this day. The checklists were completed, the engines fired up and after a five minute warm-up I carefully began to taxi down the runway. Noticeable is the extreme resistance that 15 - 20cm long grass creates at the tires especially at low speeds. The chase car assistant indicated me after about 200m of runway that I´d reached 25kph. I kept this speed, made a 180° full turn and rolled the 1300m back to start-point. It was like driving on grassland with a suspensed bike – except the aspect that you don´t need to power it.

After this run I was inspected in my original flying position. Wheels, Suspension, Plane and Engines had no problems with the vibrations and forces. After this I was separated from the plane and the plane was checked in detail - Again without finding problems. The plane was now refueled while I was having breakfast.

With the refueled plane ready for beginning the tests I was again strapped to the plane. After running up the engines we were making several runs accelerating to reach our hovering speed of 54kph. The faster the plane got the easier it was to control and the less did the bumpy ground stress me. In fact at 52kph I felt that my motion was more like jumping from bump to bump. During a heavier crosswind-gust from my right the planes heading was going to the right, but I could correct it by body motion - During video analyzation we found out that when going over 46kph without pulling the elevator a bit upwards, the planes rear-wheels lift-off before the front. When a crosswind catches the plane it of course turns on the front-wheel axis, if this is not aloft as well. Without knowing this, at that point, I dealt with the effect by pulling the elevator a bit while concentrating my steering impulses on the front-wheels.

After some successful runs at hovering speed I decided to do two more runs after lunch. Lying in the plane is quite comfortable in fact since the lots of stabilizers, protectors and the plane itself is keeping my body in a stable position. We looked at our results until that point and I felt that I could give the plane a go and take the front wheels up next time. The team decided to do one full-speed run before my try. We´d like to see if the gear is capable of landing at higher speed in case I accelerate too much when aloft. With one additional neck protector I accelerated down the runway while giving just enough elevator to keep all wheels down. Shortly before the ‘Half Runway’ mark I let the rear-wheels go and took my chest up a bit to let the plane come into a state of hover. The gear vibration reduced and I was touching the higher grass-bumps while beeing aloft between them.

After 800m I stopped the ride and was towed back to base by the chase-car. From the spotter in the chase car I got the information that my wings were bending upwards as planned. They couldn´t see anything potentially dangerous, I was speeding down the runway perfectly.

Because of these results we decided to go for the 'First Hop'. I was taking up speed not holding the rear-wheels down so they came up indicating me my speed. I was waiting a short moment more before I took my chest up and bended my legs into the jet - The heat was absolutely no problem at this point due to the aluminum-protectors and the surrounding 1°C airstream -. Although I had no elevator mounted I could feel how the plane reacted. An upcoming breeze from the side was easy to compensate at this point. The vibration of the tires was totally gone and the plane was hovering – What an incredible moment!

With the wind from the side and the plane accelerating while shifting slightly left with the wind, I decided not to correct the steering but set it down again. Later we found that the traces in the ground were totally gone for a distance of about 15 meters. I touched down with all four wheels at a time. Brakes weren´t needed due to the rolling resistance in the grass.
The spotters, both from the chase car and the base point could see the wings bending into flight position and my light shift to the left - which would not have been possible with one axis still on the ground.

The next tests will be done with V-tail attached and at warmer temperatures. Since flying this aircraft is all about my body and feeling I need to have a warmer environment for more mobility and control.


Pilot - Team Skyflash
Hanover, 28/02/2013


16/01/2013 Experiences of the first high-speed taxi runs

Putting the Skyflash together was very easy. First the wingbody is fueled up and connected to power supply. After finishing with the checklists the engine is fired up and tested carefully from 10 - 100% power. While this is happening the pilot puts his flight suit on. With running flight-computer the warmed up, ready to run wingbody is then strapped to the pilot. Hereafter the team plugs the wings on the wingbody and secures them. The skyflash is now ready to run.
Next step is the pilot laying down on his 10" offroad gear. When the gear had been fixed to the pilot the pre-start checklists are done, cameras are beeing mounted, arm-computer is put on and finally the thrust-controller is handed over to the pilot. After preparing the runway and doing a last checkover the computers are set to start and the engine is fired up by the pilot.
While the start-up process the rear-wheels are standing on a starting block to secure a horizontal align of the turbine.

The pilot maximizes the thrust to 100% and begins acceleration. With growing speed the pilot has to correct his course to the left because of the asymmetric thrust-moment of the single engine. At about 10m/s the plane begins to react on gusts and sidewind. Crosswind seems to be a problem due to the rear-wheels hovering up at about 11m/s - thus creating a hard to control configuration because of the still rolling front-wheels. At about 14 - 15m/s the front-wheels are finally hovering up as well. The behavior of the plane, according to the pilot, doesn´t change at that point.

Pilot is controlling the plane as follows:
Left arm out, right arm bodyaligned, left foot up = Left-turn (Can be supported by left arm in front of leading edge)
Right arm out, left arm bodyaligned, right foot up = Right-turn (Can be supported by right arm in front of leading edge)
Feet up, chest up = Elevator up (Can be supported by keeping arms body aligned)
Foot neutral, chest down = Elevator down (Can be supported by arms in front of leading edge)

Reducing the thrust the plane touches the ground, front-wheels first, and reduces speed. Climb could be achieved by using the elevator which isn´t installed at this point, or accelerating much further (not planned).
The distance that is needed to reach hovering-speed, single engined, is about 100m (300ft) and inside the expected range.

Next steps will be the exact reading of all recorded data by the GPS, accelerometer, cameras and team members. After this the mounting of the second engine will follow.

Team Skyflash
Hanover, 01/16/2013