Flight #74 – Weak Wave
On August 30, 2023 the forecast wave conditions had improved marginally from dismal to merely difficult. But the support teams had worked hard on various squawks from the previous flight. Perlan 2’s wings were removed to check the full travel of air brakes.
Ground tests were successful but we needed to test under flight conditions of stratospheric cold and full pressurization. Cameras and heaters were replaced, software was modified, microphones were replaced. Then we had a 2 hour on the ramp, blustery, freezing, full-instrumentation rehearsal to hunt down the intermittent radio interference source.
Helmet mike pre-amps were replaced and their gains fine-tuned. It would be a shame to find out on a potential record day that something still needed tweaking. The good news: everything we worked on was vastly improved on Flight #74.
The bad news: the weather had not improved. Dan Gudgel has pointed out that the forecasting models depend on accurate start conditions. Unfortunately he can tell from satellite photos that the reality of the initial conditions vary from the forecast ones. For those of you with glider competition experience Dan says Perlan is the “sniffer.” When the weather is marginally soarable “throw Jim up there and see if he can stick.” Good thing Dan and Jim have been friends for decades.
On the flight morning we still found a few camera issues. We are incorporating a video stream from our tail camera, through a Thales communication device, to an Iridium satellite, using VideoSoft low bandwidth video expertise. Perlan 2 is definitely the most complicated glider ever built or flown. We are troubleshooting why the video stream shows on some monitors viewing our Virtual Cockpit website, but not all. We hope to have that wrinkle ironed out for the next flight.
In the morning briefing there was a hot spot around 45,000 feet that might provide enough lift to climb. The sink rate of the glider goes up with altitude. My rule of thumb is 1 knot worse for every 10,000 feet. So even though it’s a “floater” built to climb, it needs more lift at 50,000’ than at 20,000’ just to stay level. And lots more lift at 80,000’ before it can climb. By my unscientific estimate it needs 8-10 knots of lift at 80,000’ to stay level. These are the challenges of high altitude where gravity is still 99% but air density is only 4%. Note: this is a blog not a vetted scientific journal.
Jim and Morgan were the pilots on flight #74. Arne in the Egrett again pulled the 2,000 pound Perlan 2 off the ground in under 200 feet with a brisk head wind. Check the take off video footage! The con(densation) trail behind the Egrett started about 25,000’ and went just above 40,000’ as the flight day video below showed. No useable lift was encountered on the crisscross tow pattern. When the Perlan 2 released, Arne dived to the right with a shiny wing flash. Perlan 2 turned and the hunt for workable lift continued. CapCom vectored the glider to several promising waypoints but nothing useable was found. As Ivan (a CFIG on his own) observed, “Jim fights for every foot. He doesn’t give up.”
As the cirrus clouds were tracking eastward Jim decided it was time to get home. They actually went a bit east of the airport to be free of clouds for descent, then penetrated into the wind to be closer to the runway. That’s a challenge in a “floater.”
Another great landing with a double wing flash caught by Linda Warnock.
It was hard work by the ground support teams to get the ship ready, hard work by the meteorologists to find any chance to soar, and hard work by the pilots to fly safely. As a FCF (functional flight check) the airbrakes worked normally and the radio transmissions were normal. Now if we can just get a piece of normal stratospheric wave weather we will be set!
Each team member fulfills at least 2 critical roles and supports in other ways. It has been a fantastic experience to have enthusiastic support from such diverse talented people. We are unified by our love of soaring and exploration. On flight days I take very few pictures. But I can depend on photo support by others on the team. Thanks also to Mauricio for sharing video footage. Enjoy the flight day montage video with lots of spectacular aerial footage linked below.
Perlan soars! Jackie