On 9/6/2020 7:39 AM, Frank Whiteley wrote:
On Saturday, September 5, 2020 at 10:49:25 PM UTC-6,
wrote:
On Tuesday, September 1, 2020 at 11:19:22 AM UTC-7, ProfJ wrote:
Typing this with my fireproof suit on...last weekend I tried to duck
between two rainy cumulus clouds on my glide back to home base. As I
went through the gap it became filled with virga and I was sucked
rapidly upwards, probably would have been about 10m/s if I had not had
the nose well down. This was not tranquil, but not terrifying either
(I was about 3000 ft below cloudbase) and added some useful height and
speed.

So here's the question: would you (do you?) deliberately head into
virga if you needed the boost, or is this a truly dumb thing to do?
Same for rain clouds (assuming you are in updraft not downdraft zone),
how close would you get?

Not looking for legal technicalities here, this was good VFR at all
times - just trying to calibrate risk.

I've flown a LOT in the Great Basin (Ely, Parowan) and the advice of one
of my more successful soaring mentors,Carl Herold, has proven to me far
more often true more than false. He advised to avoid Virga if the
temperature at your current altitude is warmer than freezing and fly
directly toward and through the snow virga where the temperatures at your
altitude is colder than freezing. That air will be rising! I have no idea
why this works, but it has proven to be a successful strategy far more
often than not.

I've picked up 1.5" of virga snow on the leading edges in July at FL170 in
Colorado. So flying across the band is a good idea to minimize
accumulation. Lift was fine and didn't seem to affect the stability of the
glider, LAK12, though I was concerned at the time. Sublimated after a few
minutes back in clear air.

IMO this is the sort of fundamental question/scenario every thoughtful
glider-guider should-oughta more-wisely ponder *before* encountering in the
wild than after, and in that sense RAS - with all the faults and virtues found
in humankind - can be a useful resource. As with all free inputs...chose
wisely your sources of perceived wisdom. :-)

For the record, 100% of my virga experience comes from above Colorado. Whether
or not it's "a lot" I really can't judge...but almost all of it has been some
combination of: fun, "fun", of considerable-knollich-gained content. While
it's difficult to make defensible sweeping generalizations about my
experiences, I distinctly remember a few instances.

I remember the first time I gained altitude while flying through a band of it
(of the fine mist sort, judging from the canopy) located between me and where
I wanted/"needed" to go. One working conclusion - me being from the
philosophical school of "If it happens it must be possible." - was along the
lines of: evidently air can be rising faster than "water-based-'stuff' can be
falling." (Duh!) The notion hadn't occurred to me, prior.

I remember the first time I had a "Frank's experience" (see above). I picked
up ~0.5" rime ice along both leading edges while descending through a rotor
cloud over the foothills as part of executing my version of moving from a
region of "reducing safety/WX margins" to one of "expanding safety/WX margins"
west of Fort Collins. Happened amazingly rapidly...and wasn't a serious
concern because I was in a landing-flapped-only ship (i.e. no concern about
IMC spiral diving issues), and knew that there were thousands of feet of
terrain clearance betwixt rotor and rocks. "For fun" and out of curiosity,
once beneath the rotor, I "de-flapped" and performed some stalls just because
I could...with no detectable effects upon nominal stall speeds/characteristics
- from which I concluded "not a darned thing in general terms!" The rime
sublimated within minutes of reaching clear air.

Perhaps more to the point(s?) of the original post/questions, it may be of
more enduring "takeaway interest" to ponder the "hows and wherefores" of
actually reaching a situation where Joe Glider Pilot might choose to seriously
consider an IMC descent as "desirable." CO's mountains between (say) Denver
and Fort Collins, while rising abruptly from the Great Plains, don't do so in
the manner of (say) the Sierras or those of Nevada's basin and range
mountains. They instead are crumply little things for tens of miles extending
westward in a disorganized, generally rising, mass to eventually become the
continental divide (between Gulf of Mexico/Pacific drainages), which in that
region is the primary wave generation source, generally some 25-40 miles west
of the mountains/plains interface.

On "non-hydraulic jump" days - by far more common than days of "single monster
waves" - such as this one was, it's not uncommon for the tertiary rotor to
still be located above the front range crumplies. I no longer remember if I
was wave soaring above the secondary or the tertiary rotor band, but because
the day was one of those CO days "of significant moisture" (not rare but not
uncommon, either), I'd intentionally decided to run N/S (from Boulder) above
the foothills rather than explore vertically - BTDT years before and got it
out of my system - by way of a) learning more about those sort of wave
systems, and b) cloud/terrain avoidance. In short, a nod toward WX/terrain
conservatism. The farther north I got, the cloudier it became, until I reached
my personal comfort/convenience limits, and my "what to do next?" choices
seemed to be: 1) execute the time-tested 180-degree turn; 2) push my
convenience limits by continuing north above the rotor (no pre-arranged
retrieve crew); 3) retreat east (to clearer skies and almost guaranteed
convective lift lower down).

What I chose to do was a flavor of option 3) (multiple flavors existed), the
one most interesting to me, then. Being off the descent routes into Denver'a
A/P just there and the day not being one where "general aviation types"
would've been out fun-flying (as opposed to IMC flight plan flying), I chose
the direct vertical descent over that of doing so either upwind/downwind of
the rotor band. (I hereby formally apologize to every gen-aviation pilot who
was put at risk by my callous disregard for their IMC safety, and note that no
evidence of my intentional FAR-busting exists in any of my logbooks. I think
some statute of limitation likely applies, anyway!) In hindsight, I considered
my choices Most Eminently Personally Satisfying and Suitably Educational. And,
no, I would NOT have made the same choice had I not've been flying a
landing-flap-only equipped sailplane.

In "Kentucky windage" terms, I'd guess more than half my virga encounters have
resulted in net altitude gains, with a few quite - QUITE! - the opposite.
Kinda-sorta related, none of my 3 microburst encounters involved any
obviously-nearby virga.

So how close do you get? Channeling Dirty Harry...how lucky do you feel, punk?

Bob W.

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