We're obliged to Linus Penzlien (seen above in boffin pipe mode) and Andrew Tridgell for all their hard work last week working on the custom APM:Plane parameters/commands for our Vulture 2 spaceplane.
We were finally able to get the aircraft strapped to the van roof and out for a systems test, and to run the MAV_CMD_NAV_ASCEND_WAIT command, while makes control surfaces "wiggle" every X seconds. This is to prevent the servos freezing up as the Vulture 2 ascends to launch altitude.
The Pixhawk worked fine, and here's a fetching graph of GPS and airspeed sensor speed during our 20 minute test run:
We do, however, have battery issues, and we're certainly going to need more juice. Full details on the test run can be found right here.