In wave, in blue hole at cloud level, hole closes, in IMC, then what?

On Wednesday, April 8, 2015 at 7:08:36 AM UTC-7, son_of_flubber wrote:
So I'm flying in a blue hole in wave lift of 5 m/s, trimmed to 50 knots, in clear air with a cloud layer upwind and downwind, cloud top above and cloud base below. Suddenly I find myself in IMC. What are my options?

My glider is capable of benign spiral. I open the spoilers, (already trimmed to 50 knots) and let go of stick and rudder. Then I mentally rehearse my bail out procedure and expect to come out below the cloud (or possibly above). It seems like I should decisively and without hesitation initiate the spiral ASAP, while the glider is still relatively level and at cruising airspeed.

Suggestions?

I wonder if entering clouds during wave flight in the Sierras would pose a risk of entering icing conditions ? If so would the benign spiral still be recommended ? Flying slow and dirty ?

Thanks, not an experienced wave pilot, Brian

With the understanding that a spin is a 1-G maneuver, and responding to the original post, with sufficient clear air below and after slowing down, are there any comments about leaving the cloud using an intentional spin?

I do have a comment about coming out of the cloud in a spin. How many times have you tried to sustain a spin in your glider? I would do this before I tried spinning out of a cloud. The reason is in some aircraft a spin will turn into a spiral dive. They look the same but spin recovery technique will not work recovering from a dive and the airspeed builds very fast in a spiral dive. First time this happened to me was a real eye opener, just because I have never considered the glider would transition from spin to spiral dive. I did recognize it right away and recovered no problem, but it got my attention as I had never considered this before. I was in very clear smooth air with lots of altitude. I know the POH for an ASG-29 says spins will turn into spiral dive in a few turns. Just know what your gliders does. When practicing spins I do not remember ever letting the spin go more than 2 revolutions, what if it takes 10 revolutions and on the 3rd revolution your glider spirals.

Good thread though with lots to think about.

On 4/9/2015 9:51 AM, Jonathan St. Cloud wrote:
I do have a comment about coming out of the cloud in a spin. How many
times have you tried to sustain a spin in your glider? I would do this
before I tried spinning out of a cloud. The reason is in some aircraft a
spin will turn into a spiral dive. They look the same but spin recovery
technique will not work recovering from a dive and the airspeed builds very
fast in a spiral dive. First time this happened to me was a real eye
opener, just because I have never considered the glider would transition
from spin to spiral dive. I did recognize it right away and recovered no
problem, but it got my attention as I had never considered this before. I
was in very clear smooth air with lots of altitude. I know the POH for an
ASG-29 says spins will turn into spiral dive in a few turns. Just know
what your gliders does. When practicing spins I do not remember ever
letting the spin go more than 2 revolutions, what if it takes 10
revolutions and on the 3rd revolution your glider spirals.

Good thread though with lots to think about.


Indeed...lotsa good stuff to contemplate, and ideally practice beforehand,
against the time you might (willingly or unwillingly) need to use any of it.

Spinning - what could possibly be surprising in a bird with an Approved Type
Certificate, rated for spins? Ignoring the certification fact that an explicit
number of turns was tested (usta be 3 in the U.S.), and if you go beyond that
you're now officially an unpaid test pilot, and ignoring the fact that spins
are sufficiently complex aerodynamically as to be still "inexactly
predictable" via computational methods, and nodding in the direction that
flight testing of spins and flutter are two things even professional test
pilots still pay Serious Respect to, many years ago I opted intentionally to
become an unpaid test pilot in my 1-26A (still airworthy today!), building my
skills and confidence by exploring spinning behavior. Over the course of a
summer, on days with about 10,000 vertical feet of spin-worthy airspace, I
incrementalized my way into extended spins in both directions...entries,
partial rotations, single turn spins, 2-turn spins, 3-turn spins, etc.

By the time I was up to 3-turn spins, it was becoming clear the ship had
distinctly different behaviors between left and right spins. One direction (I
forget which after all these years), the spin was "textbook classic" - nose
well down, spin rate constant, only full aft stick w. "the correct" (neutral?)
aileron and into-turn rudder convinced the ship to remain in the spin. Similar
control conditions the other direction showed considerable up-and-down
oscillation of the nose throughout each turn, in concert with variable spin
rate, slowing as the nose rose, and increasing again as it dropped. Had I not
seen before in college a US Navy film of A4 Skyhawk spin testing displaying
similar behavior, ALL of the varying-spin behavior would have been 100% new to
me (as a possibility, I mean), though I *was* also aware of the concept of
unrecoverable "flat spins."

Before I sold that 1-26, I'd convinced myself that example would spin "all day
long" the one direction in a stable, unchanging manner...at least up to 17
turns, which was the most I ever did. I also convinced myself it would NOT
ever remain in a stable spin the other direction, never being able to get more
than 5 turns from it before it staggered out from the nose-high condition.
Further, depending on how I positioned the ailerons (against the turn,
neutral, into the turn) the variable spin behavior ranged from "mostly an
'instant' uncoordinated spiral dive" through variable-over-time spinning
behavior followed ultimately transitioning into some form of uncoordinated
spiral dive. Arguably, in the absence of that knowledge, had I ever "needed to
spin through the clouds" I'd'a had a 50:50 chance of doing so in an intact
airframe.

I found it all very instructive and thought-provoking, one obvious conclusion
being not to expect consistent spin behavior just because a ship has an ATC
and is approved for spins! I'm not bashing the 1-26 or certification
procedures. The 1-26 is a wonderful ship for pilots of all skill levels,
allowing all manner of hamfistedness with relatively low risk to Joe
low-time-or-incautious Pilot. Certification procedures have necessarily
defined-before-the-fact conditions which must be met, and it's up to Joe
Pilot to decide how meaningful to him are those limits.

One other conclusion was, I really hoped/planned never to put myself into a
position where I seriously had to consider using my 1-26's spinning
capabilities to bail my butt out of cloud-coffin-corner! Flight in "wet waves"
to my way of cowardly thinking would be really tweaking the tiger's tail more
than I was ever comfortable with as a generic concept...though the devil is
always in the details, ground-to-cloud clearance and terrain beneath being two
obvious considerations...

In the Colorado Rockies (site of most of my soaring), we pretty much never
have to be concerned with wet waves of the sort relatively common in the
eastern U.S. mountains (where I grew up and got into soaring). Nevertheless
the most ice I ever picked up was when I fell out the bottom of a "somewhat
wet" Rockies' wave into a mild band of rotor-cu, beneath/ahead of which I'd
climbed to get into the wave. Being in a 90-degree flapped ship, in a known
location with known ground-to-cloud clearances, I was mostly aggravated at
losing the wave (I was sidling XC, and non-wave flight would slow my
progress). I simply put on flaps and resigned myself to having to re-thermal
my way back into the wave once I dropped below the cloudband. As I recall, the
clouds were ~2k feet thick, and in the time I was in them, I picked up about
an inch of rime ice on the main wing leading edge (and presumably on the
all-flying stabilator, though flying qualities weren't obviously affected).
The accretion rate thoroughly impressed me. Once in the (above freezing)
clear, it sublimated/slid off about as rapidly as it had accreted.
(Considerably chastened, I re-thought that day's XC plan!)

Bob W.

I've never spun a glider more than about one or so turns and I've read
that most gliders will not stay in a spin by themselves. They tend to
transition to a spiral which, in cloud, without instruments and
training, will likely result in a broken glider. Recall that, in a
spin, the indicated airspeed will stabilize near the stall speed. I'd
suggest you try spinning your glider in gentle air and trying to lose a
thousand feet or more while in the spin. That is, if you really think
it's a viable maneuver.

On 4/9/2015 9:42 AM, wrote:
With the understanding that a spin is a 1-G maneuver, and responding to the original post, with sufficient clear air below and after slowing down, are there any comments about leaving the cloud using an intentional spin?

--
Dan Marotta

On Fri, 10 Apr 2015 08:08:09 -0600, Dan Marotta wrote:

I've never spun a glider more than about one or so turns and I've read
that most gliders will not stay in a spin by themselves. They tend to
transition to a spiral which, in cloud, without instruments and
training, will likely result in a broken glider. Recall that, in a
spin, the indicated airspeed will stabilize near the stall speed. I'd
suggest you try spinning your glider in gentle air and trying to lose a
thousand feet or more while in the spin. That is, if you really think
it's a viable maneuver.

Always reading the POH before trying prolonged spins would seem to be a
good idea. Two different behaviours I do know:

- an SZD Junior has three different behaviours depending on pilot weight
* it auto-recovers after 2.5 turns with a light pilot
* maintains the spin with a medium weight pilot
* may go flat after several turns with a heavy pilot
I'm quite light: I can confirm that they self-recover after 2.5 turns
at my weight (72-75kg + parachute) even with the controls fully
crossed. I don't remember the transition points or (for heavy pilots)
how many turns they take to go flat, so if you fly one, read that
part of the pilot's manual before spinning it.

- ASK-21s tend to oscillate after around 3 turns (reported by Edwards test
pilots after the USAF Academy asked them to check the ASK-21 spin
characteristics).
Accession Number : ADA213513
Title : Schleicher ASK - 21 Glider (TG-9) Stall and Spin.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

Using high-drag configurations or spins to escape IMC is a desperation move fraught with unpredictable and uncontrollable hazards. There's enough data in the accident record to say it often doesn't work.

If one planes to fly in wave close to lenticulars, there's a chance of becoming enveloped in IMC. To me that says having an attitude indicator and enough skill using it to keep the glider upright in turbulent air is an absolute necessity.

although the spin may not increase the load factor, after you recover from a fully developed spin, you will find yourself 30 degrees (or more) nose down. the pullout from the dive is a high-G maneuver. Pull out too quickly, and you risk an accelerated stall (or worse). Pull out too slowly, and you risk exceeding max dive.

On Thursday, April 9, 2015 at 11:42:03 AM UTC-4, wrote:
With the understanding that a spin is a 1-G maneuver, and responding to the original post, with sufficient clear air below and after slowing down, are there any comments about leaving the cloud using an intentional spin?

"Its also worth mentioning that Vne is not based on load factor, like Va, but on flutter, which is why its True and not Indicated. "

Actually flutter is dependent on equivalent airspeed not true airspeed. There was an interesting article in Soaring magazine way back where Stan Hall brought in a NASA aerodynamic expert specializing in aeroelasticity and had his work peer reviewed by other experts to try and get a definitive answer on a flutter question arising from a flutter accident that led to several months of "argument by letter to the editor."

"In my glider, the placard VNE is 146 knots IAS but at 18,000 ft this is reduced to 122 knots IAS" Which brings up a question I've never been able to get a good answer to: what methodology do they use to determine reduced VNE with increasing altitude? Many gliders specify just IAS and the gliders I've dealt with which do specify lower VNE's with increasing altitude don't have those speeds match up with TAS at those altitudes. Calculate what TAS at 18,000 for an IAS of 122 knots actually is. It's higher than 146 knots.

As for the original question: where I fly the clouds are filled with granite up to 7000 feet or more, the valleys are narrow and the valley floors are not much above sea level. I don't have a turn and slip or AH and I have only had minimal training on those instruments over a decade ago in a Piper Cherokee. Being caught in cloud where I fly I would probably opt for the parachute pretty damn quick. That however is just the best of a bunch of bad options really.

On Friday, April 10, 2015 at 9:02:23 PM UTC-7, wrote:
"Its also worth mentioning that Vne is not based on load factor, like Va, but on flutter, which is why its True and not Indicated. "

Actually flutter is dependent on equivalent airspeed not true airspeed. There was an interesting article in Soaring magazine way back where Stan Hall brought in a NASA aerodynamic expert specializing in aeroelasticity and had his work peer reviewed by other experts to try and get a definitive answer on a flutter question arising from a flutter accident that led to several months of "argument by letter to the editor."

"In my glider, the placard VNE is 146 knots IAS but at 18,000 ft this is reduced to 122 knots IAS" Which brings up a question I've never been able to get a good answer to: what methodology do they use to determine reduced VNE with increasing altitude? Many gliders specify just IAS and the gliders I've dealt with which do specify lower VNE's with increasing altitude don't have those speeds match up with TAS at those altitudes. Calculate what TAS at 18,000 for an IAS of 122 knots actually is. It's higher than 146 knots.

As for the original question: where I fly the clouds are filled with granite up to 7000 feet or more, the valleys are narrow and the valley floors are not much above sea level. I don't have a turn and slip or AH and I have only had minimal training on those instruments over a decade ago in a Piper Cherokee. Being caught in cloud where I fly I would probably opt for the parachute pretty damn quick. That however is just the best of a bunch of bad options really.

In a cloud, it would be best to observe the max maneuvering airspeed which reliably tracks IAS but is usually considerably below Vne.

As I understand it, the flutter dynamics do not change at the same rate as dynamic pressure which is proportional to air density and V^2 therefore TAS is proportional to delta density^0.5. The coefficient for flutter in somewhere between 0.5 and 1 so the flutter speed increases, but not as fast as TAS increases with falling density. A lot of flutter has to do with dampening, I suppose in thinner air there is less.

I don't think many modern gliders are actually tested to flutter, I believe you are allowed to use computed numbers now for cert.