At the summer 2013 Colorado FPV meet in South Park, near Hartsel, Colorado, a group of us did a special project. We did a one-way, point-to-point FPV flight from the top of a hill next to our campsite to the far side of a reservoir 8.6 miles away, handing off control from the pilot at the launch site (myself) to a pilot at the landing site halfway through the flight. We accomplished this using the multimaster mode on the Rangelink UHF Long Range System, which allows two (or possibly more) radios to be bound to a single receiver.
Here is the video combining footage from the onboard HD camera (a Contour Roam2) and ground recordings from both sites, along with ground audio from both sites. We coordinated the flight via cell phone, and you can hear the running dialog in the background.
The plane used for the mission was my Crash Test Hobbies Deep Reaper XL flying wing, equipped with Rangelink 433 mhz control and a 1280 mhz video link. The OSD onboard is a Cyclops Breeze Pro. The power system is a 1250kv Turnigy SK3 motor, 10x6 prop, 80A Detrum ESC, and 2x 4000mah 4S Zippy lipos. It also has an FY-30A stabilizer.
Here is an overview of the flight on Google Earth:
The mission was not without its challenges. We were originally planning to use a different plane, but it was crashed in a test flight which busted its motor. After several unsuccessful repair attempts, we decided to switch to my Deep Reaper at the last minute. Since the destination team was already in position, we had to talk them through the settings for their radio over the phone, made easier since the control radios were a Turnigy 9XR and an older Turnigy 9X, both running the ER9X firmware.
We had also originally planned to do a two-way flight, changing batteries at the lake and flying back to the launch site. Since the other team did not have fresh batteries for my plane, and because of the lack of a clear landmark for the return flight, we decided to only do it one way. It was also pretty windy, which made keeping the plane level and flying in the right direction challenging. Multiple ground stations equipped with high-gain antennas were set up at each site for redundancy.
In the future we would like to experiment with doing a three-plus radio handoff, depending on the capabilities of the Rangelink multimaster mode and how many radios it can synchronize. And while on this flight, both teams had line of sight to the plane the whole way (the team at the lake was actually able to control the plane even before launch), this would enable flights up and over a mountain, which would be impossible for a single pilot to accomplish without breaking line of sight and losing radio contact.
All in all it was a very fun experiment, and I am very happy it was successful.