"Mid-Air Collision"

Sometimes things happen during testing. On this mission the Phantom 4 "Nemesis" experienced a mid-air collision with another Phantom 4 during joint flight testing. This was a one-in-a-million collision where there was no crash, no damage, nor even a visible sign an impact had even occurred were it not for the video evidence.

We first noticed something was amiss while reviewing video from the second P4. Seeing a video "hiccup" we initially thought it had experienced a gimbal glitch as occasionally occurs with a P4. It wasn't until reviewing the video from "Nemesis" that we realized there had been contact.

"Nemesis" engaged RTH after recovering, narrowly missing the railing & antennae atop the World Trade Center. The other P4 continued on &, if you look very carefully, you can see it off in the distance completing its spiral as "Nemesis" climbs to RTH altitude.

What happened: The chase bird is flying the identical Litchi mission, only the start point has been moved back 25', each waypoint altitude has been increased +10', & the bird is generally pointing straight ahead to keep the lead bird in view. Meanwhile the lead bird was flying the normal mission panning towards POIs along the route. Two things conspired to cause this "bump." First panning & spinning slows down the aircraft. This allowed the chase bird, flying straight ahead, to catch up. Second I inadvertently missed adjusting +10' on ONE of the 75 waypoints. It just happened to be the one where the birds met up! At any other waypoint this probably wouldn't have become an issue.

Learned from this for future "chase" missions were:

1) All birds must be doing the same yaws to keep speed consistant.
2) DOUBLE-CHECK ALL WAYPOINTS!