The team has successfully tested two different platforms for the retrieval aircraft. The Gladiator and the Skywalker.
The retrieval aircraft must be capable of travelling a long distance at high speed and with potentially high winds to reach the target area. It must then land in a potentially confined space. This presents challenges as a conventional multi-copter platform would not have the endurance, and a conventional fixed-wing platform would not have the ability to land and take-off in a tight space.
We have chosen to develop two standard fixed-wing planes that are capable of taking-off on their bellies in a very short distance. The retrieval aircraft must be capable of taking off on rough surface, it must be able to steer itself on the ground, and it must have enough clearance of the prop to avoid the risk of breaking the prop on the ground.
Trialling some different configurations for the Skywalker and the Grim Reaper platform we were able to reliably perform belly-take offs. We were initially concerned that the Grim Reaper would not have enough prop clearance, and would not be able to steer on the ground. The raised motor mount and belly-skid works well to give enough prop clearance. The plane can steer itself on the ground quite well by as the aileron will push one of the wings on the ground and cause the plane to turn in the that direction. It is believed the Grim Reaper platform will be more efficient that the Skywalker.
The planes have a combination of flaps, airbrakes and reverse thrust to allow them to achieve a steep glide slope. They have an ultrasonic sensor that allows the plane to flare very close to the ground. This allows the planes to land in a very short distance.
The Grim Reaper is a smaller proof of concept platform, so the next step is to build the larger Gladiator XL platform with the same set-up. We will then test this to make sure it can carry the full weight of payload and batteries and meet the endurance and speed requirements.