On August 7, 2018 while attempting a landing at the end of a mission on the Graves Fire in Oregon, an Insitu ScanEagle X200 unmanned aircraft came in too low resulting in a low capture on the suspended rope. The payload and the left wing sustained visible damage.
According to the preliminary report, the flight crew believes the failure of the aircraft to correct the errant glide path was caused by turbulence generated by terrain at the recovery site.
After the incident the ground control software was upgraded to improve the glide path tracking. In addition, the site lead reemphasized the decision making process for initiating a timely go-around.
An article by Gareth Corfield in The Register describes how a newer model of the aircraft, an Insitu ScanEagle3, is recovered after a mission:
“Insitu craft are recovered from the air by the simple process of commanding them to fly at a rope suspended from a crane-type contraption fitted with a hydraulic damper system;
the aircraft’s swept wings are both fitted with titanium carabiners at their tips that grip the rope tightly, suspending the Scaneagle in mid-air until the ground crew lowers it. An onboard accelerometer senses the violent yaw when the wing is caught by the rope (the aircraft cartwheels sideways when it hits) and cuts the engine. The process was described as “very dynamic” by Insitu personnel, an assessment El Reg agreed with.
“The unmanned aircraft flies itself autonomously to the point where it returns back to its Skyhook (Insitu’s trade name for the crane-rope capture affair) using differential GPS with the ground beacon being placed under the rope. All human involvement is limited to pressing the required buttons to start the landing sequence and getting the UAV off the rope afterwards. Though the craft can be flown on barometric altitude (as manned aircraft typically use), it is launched and recovered on GPS altitude. We were told that the UAV is programmed to approach the rope at a height of 33 feet with a two-foot lateral offset to increase the chances of a wing meeting the rope rather than the nose.”