We lost and luckily found our Shrike this week! So what happened? Long story, but we believe the following occurred to create the situation:
1.) We were flying from inside a car (Tx only, vRx was mounted on top of the car) which was no doubt reducing the range of our Tx.
2.) APM was set for a 45% throttle cruise speed for Auto & RTL, which for our airplane, was not enough to safely return it home in the 20mph head wind we were facing during RTL.
3.) When the airplane was at it's furthest point, it lost signal from our Tx, causing it to kick into Failsafe, which is to Loiter once, and then RTL.
4.) The airplane went into loiter, gained a little connection from our Tx, returned to back to Auto (the mode we were in), then lost connection, when to loiter, gained signal return to auto, etc. all the while a 15-20 mph wind is carrying it further and further away.
5.) When we finally turned the Tx off to allow the APM to only RTL, it was too late, the battery was too weak and the wind too strong for it to RTL.
It eventually lost enough power to safely land with stabilization carefully returning it to level and controlled decent.
What did we learn & what are we doing to fix it? A ton. We literally have over 50 tasks to make prevent this from happening and to aid it recovery. A few of the main ideas:
1.) Get the Tx out of the car to improve range
2.) Set failsafe to skip the loiter and go straight to RTL
3.) Increase RTL throttle rate to allow for headwind recovery
4.) Place a buzzer on the plane to assist in recovery
5.) OSD/Telemetry to assist in navigation
6.) Elevate vRx to increase signal quality
and many, many more.