Sunday, March 25, 2012

Mountain Climbing in a Greenhouse

We can never quite tell how a day will shape up for soaring. I went to Crystalaire this Saturday not even sure if I would fly, wondering if the weather would turn out like the forecasts, had a long wait for a tow, and ended up having one of my best flights ever!

Winds in front of an approaching Pacific storm were forecast to be from the south. If other conditions are right, this can cause mountain wave lift between the gliderport and the San Gabriel Mountains. The RASPtable forecast for 13:00 at 500 millibars (about 19,000 feet MSL) looked like this. The gliderport is somewhere near the word "Llano". The reddish area would be the strongest lift. But would it really happen?

At the field, lenticular clouds were clearly visible to the east. The senior instructor said the wave was working and had been for several days. The temperature on the ground was much warmer than I expected, and the wind was warm, indicating a foehn effect. I had some tasks to take care of earlier in the day, so I did not get fully ready to fly until about 13:30, by which time there was a line of 5-6 gliders waiting to take off. Then one of the two working towplanes was grounded with an electrical problem, so I didn't actually take off until 14:33. I almost canceled because the southwest wind was 15 knots gusting to 18, which exceeds the PW5's maximum demonstrated crosswind component (a guideline, not a hard limit). But there is a short crosswind runway which aligns very nicely with that wind direction, which would turn a strong crosswind into a great headwind for landing. So up I went.

There was a lot of turbulence on tow, much of which was no doubt wave rotor. I let off tow at 4,100' AGL (7,500' MSL) when we flew into smooth wave lift. I don't remember the exact sequence of climbs and loss of lift (I may update this after I peruse my flight trace), but I easily got up to 13,000 MSL, higher than I had ever been in wave. Most of the time I was heading southwest directly into the wind. The best speed for climbing seemed to be about 48 knots, which is Best L/D speed for the PW5... I expected it to be down around Minimum Sink, so I'll have to think about that. (Comments, anyone?) At times my groundspeed appeared to be nearly zero (though I did not have GS shown on my PDA/GPS... I'll have to add that number to the display) so my airspeed of 48 must have been very close to the wind speed. Look back at the forecast map above: the wind barbs show 45 knots, though that was for 19,000'

Having reached 13,000', my thoughts turned to overflying Mt. Baldy (actually named Mt. San Antonio, about 10,000', and visible as the highest oval in the map above), which has been one of my goals for a while now. That would be challenging, because the wave was 4-5 miles north of the mountains, and I would need extra altitude to fight non-lifting headwinds to get there. The wave lift pretty much paralleled the ridge, so I was able to maintain and even gain as I headed east. By the time I was adjacent to the peak, I was at 16,600'! My previous personal record had been 15,100' over the southern Sierras. Even if I did not make it to Mt. Baldy, this was already a great day!

So I headed toward the peak, but as I mentioned, the winds were strong... my 48kt Best L/D wasn't going to get me there. I had to speed up to 70-75 knots to make any headway, and then of course the glide ratio gets really bad. At times I was seeing 800 to 1000 feet per minute down - not what I needed! By the time I got to the peak - frequently looking over my shoulder at the gliderport getting further away - I was down to 13,000'. SeeYou Mobile was telling me I had plenty of altitude to get back (it's only 14.7 nautical miles), and the look-down angle was good... but I'm really not that comfortable getting far from a landing site. and I have not personally scouted the landout options in this area. And I'm very aware SYM does not know about actual wind conditions, so one always needs to be more conservative than SYM's guidance. If the wind shifted from southwest to west, I would have a big headwind component on the way back. So it did make me nervous. Just as soon as I was over the peak, I turned back to a heading halfway between "direct to Crystal" and "directly back to the wave".

On the way back, I got more of that 1000 fpm sink. By the time I reconnected with the wave, I was down to 9,xxx feet. Back in the wave, I headed west again and by the time I was adjacent to the gliderport I was back to 13,000' again! I had been up for about an hour and a half.

People ask me if it's cold up there. It is and it isn't. I occasionally checked the Outside Air Temperature display, and the lowest I saw at 16,xxx feet, was -10 Celsius, which is +14 Fahrenheit. Yet I was very comfortable in a short-sleeved, lightweight shirt. After about an hour and a half, my feet started to get cold, and there are a few air leaks around the canopy (need to replace some weatherstripping) so there's an occasional draft to the neck. but that's all. The big bubble canopy on the PW5 truly acts as a greenhouse and traps the sunlight, keeping it nice and warm. (Good in the winter, not so good in the summer.) So yes, I went mountain climbing in a greenhouse!

I lost nearly no altitude getting back, and looked directly down on the gliderport from 13,000'. I headed north to lose some altitude, and lost a couple thousand feet or so, but guess what - I contacted the secondary wave (where the senior instructor had reported it hours earlier). Clearly THIS was not the way down. So I headed back south and pulled my spoilers out... and got into some of the worst rotor turbulence I've ever seen, the kind that bounces my head on the canopy and sends radios and stuff flying out of the cabin pockets. I slowed down my airspeed a bit and it was not too bad, and only lasted a couple of minutes. After that I flew with full spoilers, and at times I saw -1250 fpm on the digital display.

As expected, the wind at ground level had not abated, and the tetrahedron showed that the direction had not changed, so I opted to land on the crosswind dirt runway. It's only about 330 feet long before it intersects the dirt approach area of the main runway, and 450 feet to the centerline, but with a strong headwind that should not be a problem. We got lots of practice landing short at Hemet-Ryan! I was quite aware of another glider in the pattern behind me, so I turned off as soon as I could, and was concerned I was in his way as he landed on the main runway, but I was about a hundred feet off the centerline so it was not a problem at all. Total flight time: 2 hours and 2 minutes.

Sorry, no pictures of the beautiful snow on top of Mt. Baldy or the Mountain High ski resort, but I didn't take my camera along this time... and I was kinda busy! I may be able to update this with my flight trace.


Paul said...

Congratulations on a great flight, Roger!

I got my first taste of mountain wave soaring in West Virginia a few weeks ago--what an amazing experience. I had numb feet but was otherwise comfortable flying with a fleece at 23k ft.


Roger Worden said...

A couple of updates after reviewing my flight trace:

- GPS shows my maximum altitude at 16,963' MSL

- The SSA web site shows the California altitude record for World Class (i.e. the PW5) at 13,015' But that category is closed to new records, so who knows what the record would actually be by now.

- My minimum groundspeed was 6 knots.

- My vertical speed ranged from +18 knots to -20.4 knots (when my spoilers were out)