Wednesday, June 20, 2012

Truckee to Byron via White Mountain Peak and Yosemite

16K over Yosemite park within sight of Yosemite valley
Crossing the sierra from Sonora Pass area
 I had an interesting flight on Saturday from Truckee. Thanks to Jim Alton (who also lives in San Ramon) who volunteered to drive my car and trailer back home if I fly to Byron, I decided to keep this an option in case I can get high enough over the Sierra crest. My plan was to go back home Saturday night anyway, so this sounded like an attractive option. The day started slow though, and I had to struggle to get out of Truckee, and to get to Patterson where the first clouds started, but once there, it was relatively straight forward to get to White Mountain Peak, and to cross from there to the Sierras near Tioga Pass. I got to near 18K and flew deep over Yosemite park within sight of Yosemite valley and Half Dome. Still crossing to Byron from there was not a sure thing, I needed to get further NW first, so followed the clouds over the Sierra crest to near Sonora Pass, but could only get to 15.5K or so there, which gave me marginal glide to Byron with 10 knots easterly tail wind.
There were more clouds further west of the crest, but they were not giving much, but I managed to gain some on glide also thanks to the easterly wind. But once over the western slopes of the Sierra, the 10 knots tail wind turned to 10 knots head wind due to NW wind aloft, and it stayed that way all the way down to landing. I also needed to crab some to the north to maintain heading to Byron. My flight computer did not pick up the change as I was not turning, but I started loosing on glide to Byron quickly. The only indication I had of the change was by comparing my ground speed  to my TAS. I wonder how many pilots looking at those 2 numbers side by side in their flight computer? If your flight computer provides TAS, I highly recommend this method, as it is the most instantaneously HW/TW info. Anyway, once I figured how to tell XCSoar that I actually had 10 knots head wind and not tail wind, most of my margin over Byron was gone, but by now I was already committed. Of course I had plenty of margin over the Sierra so it was a no stress, 100+ miles glide which took 1.5 hours.
Long story short, I barely made Byron.  Around 20 miles out I was only 500 over glide, but it didn't look right. The glide angle to Byron looked much more flat than it should until I realized I need to adjust for Byron pressure altitude which was 600 feet off! Once adjusted I lost all my margin and just had enough for base to final. The vario never beeped even once since I left the last cloud at around 15K. Still I managed 40:1 glide with 10 knots head wind and slightly sinking air. Not bad. One point less in glide and I would have landed short...
I was hoping to still find pilots at Byron since after all the forecast for the Diablo Range was great if someone took high tow. And indeed I found Yuliy who was still working on his glider when I landed around 6:30PM.
Special thanks to Yuliy for the ride home, and to Jim Alton for driving my car and trailer from Truckee Sunday night. 
This is BTW the second time I fly across the Sierra to Byron, the first time was nearly 10 years ago from Minden with my old LS4.
Flight is on OLC: