SpaceShipTwo is nestled between the twin fuselages of WhiteKnightTwo during a flyby at Spaceport America in New Mexico on October 17.

On September 29th, SpaceShipTwo made its 16th glide flight, and first in three months, in the skies above Mojave Air and Space Port in California. The SpaceShipTwo test flight log at Scaled Composites indicates that the flight did not go exactly as planned:

Test card called for releasing the Spaceship from WhiteKnightTwo and immediately entering a rapid descent. Upon release, the Spaceship experienced a downward pitch rate that caused a stall of the tails. The crew followed procedure, selecting the feather mode to revert to a benign condition. The crew then defeathered and had a nominal return to base. Great flying by the team and good demo of feather system.

Earlier this week, SPACE.com’s Leonard David provided a little more information about that glide test. That discussion makes the flight sound a little more harrowing than the writeup in the official log, with one observer claiming that the vehicle “dropped like a rock and went straight down”.

Scott Ostrem, chief engineer at The Spaceship Company, the Scaled-Virgin Galactic joint venture that will be manufacturing SpaceShipTwo and WhiteKnightTwo, offered an explanation at the International Symposium for Personal and Commercial Spaceflight (ISPCS) in Las Cruces, New Mexico, on Wednesday. “You come off the WhiteKnight and quickly going into a pitch-down attitude by design,” he said. “We pitched down a little too steeply on that flight and experienced a tail stall.”

There are several options to recover from such a stall, he said, one of them being using the vehicle’s unique feathering mechanism, designed to provide stability during reentry. “Our pilot chose to feather it. It’s an incredible testament to the feather design: instantly the vehicle stabilized at about 20, 30,000 feet,” Ostrem said. “We just then de-feathered and glided back down safely. It was a unique opportunity for us to prove out the feather design ata point where we weren’t necessarily intending to do it.”

That, however, has not stopped a series of rumors, whispered during breaks at the ISPCS and on the Internet, that the incident was more serious than what the companies have reported. Those include rumors that they were testing a maneuver in order to perform a drop test at the Spaceport America terminal dedication event held Monday. No such drop test took place, of course, but whatever happened did not prevent Virgin and Scaled from ferrying SpaceShipTwo from Mojave to the spaceport for the event.