After a long flight in good conditions, Shmulik Dimenstein yesterday died in the crash of his HpH Shark glider, near his home airport at Rifle, Colorado. The cause of the crash is under investigation; possibly relevant is a singular gust of 43 kts (recorded by the airport ASOS near the time of the crash) on an otherwise benign day.

Even a quick look at OLC results over the past several years will show Shmulik’s skill at – and love for – long flights among the mountains of western Colorado (and neighboring states). Less apparent will be his extraordinary hospitality to those who came to fly gliders at Rifle. He was a valued friend not only to glider pilots but also to the Rifle airport staff and the local FBO.

On Friday, June 10, 2022 at 10:09:44 AM UTC-4, John Good wrote:
> After a long flight in good conditions, Shmulik Dimenstein yesterday died in the crash of his HpH Shark glider, near his home airport at Rifle, Colorado. The cause of the crash is under investigation; possibly relevant is a singular gust of 43 kts (recorded by the airport ASOS near the time of the crash) on an otherwise benign day.
>
> Even a quick look at OLC results over the past several years will show Shmulik’s skill at – and love for – long flights among the mountains of western Colorado (and neighboring states). Less apparent will be his extraordinary hospitality to those who came to fly gliders at Rifle. He was a valued friend not only to glider pilots but also to the Rifle airport staff and the local FBO.
Very sad to see. Condolences to his family and friends.

This is a shocker. He was highly experienced and I hope the riddle is answered so that I (we) can learn from it.
I had the privilege of joining the regulars at Rifle last June for a short visit to learn and experience mountain flying and Shumlik was the Host and a mentor.

R

Hard to believe. Even harder to stomach. He was a great guy.

RIP Schmulie

Oh no! Terrible news!

On Friday, June 10, 2022 at 8:38:24 AM UTC-7, MNLou wrote:
> Hard to believe. Even harder to stomach. He was a great guy.
>
> RIP Schmulie

Very sad to hear. I myself had a narrow escape from a vortex / downburst encounter that I was able to identify with data supplied by my Air Glide S to my Oudie.

Key items were TAS and GS at one second intervals.

If anybody has access to the recorder(s), methodology is available at:

https://drive.google.com/drive/folders/0B1NeKc6B2S3XeDY0Q1Z6NXdsd2s?resourcekey=0-HMr9FEeYd1ZUuNPA7qlLRg

I'll add that Shmulik's ability to make friends with and relate well to all he met were quite remarkable, and had a lot to do with the good experience that visiting glider pilots consistently enjoyed at Rifle.

He lived for a good while in Charlotte NC and was of course friends with another Charlotte resident: Charlie Spratt. I can pay him no higher compliment than to note that his interpersonal skills were "Spratt-level".

On Friday, June 10, 2022 at 10:54:13 AM UTC-6, John Good

https://www.weather.gov/wrh/timeseries?site=KRIL

On this chart it shows at 5:40 the wind at Rifle AP going from a mild W- NW day to South at 30 G43
RIP Shmulik Dimenstein
Nick
T

On Friday, June 10, 2022 at 1:15:59 PM UTC-4, nickkennedy...@gmail.com wrote:
> On Friday, June 10, 2022 at 10:54:13 AM UTC-6, John Good
>
> https://www.weather.gov/wrh/timeseries?site=KRIL
>
> On this chart it shows at 5:40 the wind at Rifle AP going from a mild W- NW day to South at 30 G43
> RIP Shmulik Dimenstein
> Nick
> T

I am seriously bummed-out by this sad news! When Shmulik did come to visit the Carolinas, he typically did show up at the airport in Spartanburg and we would have dinner together. He even offered to tow for us while here.
In 2017, we met in Montrose, CO and he did give me some pointers on flying that part of the Rockies.
We would sporadically chat about his latest great flight in the Rifle area.
He was truly a great pilot and individual.
Rest in Peace, my friend!

Uli
'AS'

He was a current member of the Piedmont Soaring Society near Winston-Salem NC and last flew here in April with his friend Gidi.
He was always keen to help out whether it was flying the tow plane or instructing but really enjoyed cross country flying the most.

There will be a Celbration of his Life in Charlotte on Wednesday 15th from 5:00pm .t.o 9:00pm
7209 Graybeard Ct
Charlotte
NC 28226

R.I.P Shmulik

Bob 7U

This is a first-hand account of the crash, by Rick Roelke (who also flew from Rifle CO on June 9):

------------------------------------------------

I originally wrote this to be read by glider pilots. But it became apparent it would also be of interest to non-pilot friends and relatives wishing to better understand how this accident could happen to such a talented and experienced pilot. To aid that understanding I will preface the report with a glossary of pertinent terms. To my pilot readers: feel free to skip this section. I also ask forgiveness for abbreviated explanations: this is not intended as a textbook, but merely to provide context for laypersons.

Virga

Virga is snow/rain falling from a cloud, that evaporates before it hits the ground. It is a common phenomenon in the western US. We do not see it as often in the east as it takes dry air and a high cloud base to cause the evaporation. It can cause clouds to take on the appearance of a jellyfish, with rounded tops and dangling tentacles.

Stall Speed

Aircraft fly by having air pass over the wings. If the speed of the aircraft falls below a certain minimum the wings can no longer provide the lift required to support the aircraft. That event is called a stall. This moment of stall can be (often is) abrupt. With adequate altitude the aircraft pitches down, regains flying speed and returns to controlled flight. All pilots are trained and practice stall recovery regularly. Stall speed is the minimum speed the aircraft can be flown controllably.

Sink

Gliders fly long distances by locating rising air and climbing in that air. What goes up must come down: descending air is called sink.

Microburst

Microbursts are narrow columns of rapidly descending air. They are associated with thunderstorms but can be caused by other sources. The one featured in this report was likely caused by the virga. The snow/rain falling from the clouds above start cool and then further cool by evaporation. This cold air is more dense than the surrounding air and starts to sink. Given favorable conditions this air can accelerate. When this rapidly descending air meets the ground it spreads out to become a sudden horizontal wind: a gust. The best kitchen analogy is water flowing from your tap and hitting a plate in the sink. The falling water splashes out sideways.

ASOS

Automated Surface Observing System. This is an automated weather reporting system that continually broadcasts the local (on airport) conditions.

---- End glossary ---------------------------------------------------------------------------------------------------

Four gliders flew out of Rifle on June 9th 2022. We all launched around 11:00 and moved to the north side of the valley. It was tough to find that first good climb, but Shmulik found one, leaving the rest of us floundering low. Eventually we did get away. Long story short we all ended up going in different directions, all having great flights. They were not without challenges but nothing spooky, just enough work to be rewarding. In a flight of about 600 km, Shmulik made his goal of Duchesne UT, and was happy about that. We made plans to be on the ground at 6:00 and all converged on the Rifle area in time for that.

There was virga in the area, and it got my attention as Shmulik had warned me on a previous trip to be careful with local virga. I was listening intently to the ASOS for wind or gusts, letting it repeat 5 or 6 times with the exact same report: 9 kts straight down the runway; no gusts. Later, as we got ready to land, the same benign report. OK I thought - the virga is clearly a non-issue. As we will learn, it was the whole issue.

There was virga over the airport (elevation 5537 ft) and to the north of the valley, and northeast as well. None of the wisps extended below 11,000 ft (cloud base was approximately 19,000). Cloud cover was scattered. The clouds producing virga were not towering - they were perhaps a bit bigger than non-producing clouds, but not much. It was a point of interest to me as we don't see a lot of it in the eastern US - I was wondering what drove the difference.

Shmulik and I discussed the landing order: as he was a bit lower we agreed he would go first. After we decided this, we heard a Challenger jet announce “Taxiing to 26 for takeoff”. That was the runway we would use to land.

Rifle has a moderate amount of bizjet traffic; not constant but present. We always try to accommodate and be polite citizens. Shmulik called the Challenger and offered to delay but got no reply. I was still high so it was no problem for me. He tried again, with no reply. It’s worth noting that Shmulik had a close call in the past: a jet pulled onto the runway in front of him with no radio call. This near miss was avoided only by the jet taking off immediately in front of him. I am sure he did not want to repeat that. I speculate that the Challenger was on a different frequency temporarily, perhaps the ASOS.

As he descended, he called that he was in heavy sink and was going to make left traffic for Runway 26 (for which the normal traffic pattern is right). Shortly after this a call came from the Challenger that there was a glider crash.

I was not sure I’d heard it correctly so I asked for clarification. “There has been a glider crash and we see no movement.” They truly had a front-row seat, as moments before they were hit by a gust so strong that they had rotated their jet to avoid a compressor stall.

I then asked if the runway was clear, was told yes, then landed uneventfully into the 9 mph headwinds. I am not sure of the time between our landings - I would guess it was 5 min. The other glider pilots landed without problems, though all could see the wreckage of our friend’s aircraft which left no doubt as to the outcome.

The last moments of the crash were recorded by an airport security camera. We were allowed to view the footage (but not record it). It showed Shmulik in a moderately steep turn, apparently carrying a lot of speed. In the background you can see dust and gravel being blown by the gust. Then at 90 deg to the runway and 150 to 200 ft you can see the inside wing start to drop and the nose go down. There was no opportunity to recover and it hit the ground hard, thankfully just out of camera view.

The Rifle ASOS recorded a gust of 43 mph from the south: a 100-degree shift in direction, putting it right on his tail.

My analysis and proposed scenario are as follows:

The virga produced a microburst directly over Shmulik as he was waiting for the jet. He expedited his landing trying to fly out of what was likely epic sink. While his base leg was low it looked high enough to make the runway with plenty of energy to flare and roll out. But he then got hit from behind or descended into winds in excess of 40 kts and perhaps as much as 50, stalling the aircraft and removing any opportunity for control.

One of the most difficult aspects of this accident is that, given the information available to the pilot, it is hard to picture what anyone would have done differently. This truly seems like the hand of God. There is discussion in another thread about the yellow triangle. Here is a case that would require 60 over stall speed to maintain even a narrow margin. How many people do you know that would plan to come over the numbers at 100+ on a day that is blowing steady 9 straight down the runway?

As has been noted, Shmulik was a very experienced and skilled pilot. He had more flights and time in gliders from Rifle than anyone. We all want to learn from accidents, especially what were the pilot errors we might avoid. This is a hard one to gain insight from other than this: Some atmospheric events are bigger than our plastic airplanes.

RR

On 6/13/22 22:31, John Good wrote:
> This is a first-hand account of the crash, by Rick Roelke (who also
> flew from Rifle CO on June 9):
>
> ------------------------------------------------
<Highly informative write-up snipped, for this-post's-brevity>

A big, "Thank you!" to Rick Roelke and John Good for generating this
information, and for conveying it via RAS (and, so I infer, to other
interested folks).

This tragic and sad situation was - so it seems to me - almost certainly
one of those rare instances where "fate targets a person." (By "rare" I
mean at an individual level, of course...)

Having been in "fate's sights" at least twice that I know of while at
the controls of a sailplane, such an event makes a person think harder,
it does, it does. I certainly did, and (for what it's worth), concluded
after both incidents that the personal rewards flowing my direction from
indulging in the sport of soaring outweighed the imponderable risks of
atmospheric physics. If anything, those imponderables influenced me to
strive even more diligently to control the things *directly* in my
control such that if I did happen to die while piloting a sailplane, I
wouldn't be embarrassed in hindsight by the circumstances surrounding my
crash. (Funny, the motivations a person can rationalize!)

May Mr. Dimentstein rest in peace and may his family and friends be able
to take some comfort from the circumstances of his death.

Bob W.

When I was flying with the Black Forest Soaring Society at Kelly airpark, I'd read the NWS forecast discussions and they would often mention "virga bombs" associated with high based thunderstorms. The virga starts falling, the water evaporates which cools the air and accelerates. By the time it reaches the ground it could be going 50-100 knots!

In the early 2000's, sometime after a storm had passed Kelly, there was still some mid level crud overhead but it was mostly clear and sunny. I flew crosswind to the west directly overhead at well over 1000' AGL when the bottom fell out below me. As I pushed the nose of my ASH-26E down into what felt like at least a 45 degree dive the airspeed was still barely 50 knots. I was aiming for a field just outside the fence to the west for a crash landing if the sink didn't abate. As I got down to 100' or so, the airspeed suddenly jumped to over 100 knots and the glider started flying again. I turned right and pulled up to gain a little altitude for an abbreviated downwind to land. As I was on a 3-400' high base leg and turning final, I hit the outflow of that downburst and found myself back at nearly 1000' and a 90 degree crosswind on the runway. So I allowed myself to drift east and landed in the grass at 45-60 degrees to the runway. By the time I opened the canopy, the wind on the ground was calm.

5Z

On Tuesday, June 14, 2022 at 12:31:08 AM UTC-4, John Good wrote:
> This is a first-hand account of the crash, by Rick Roelke (who also flew from Rifle CO on June 9):
>
> ------------------------------------------------
>
>
> I originally wrote this to be read by glider pilots. But it became apparent it would also be of interest to non-pilot friends and relatives wishing to better understand how this accident could happen to such a talented and experienced pilot. To aid that understanding I will preface the report with a glossary of pertinent terms. To my pilot readers: feel free to skip this section. I also ask forgiveness for abbreviated explanations: this is not intended as a textbook, but merely to provide context for laypersons.
>
> Virga
>
> Virga is snow/rain falling from a cloud, that evaporates before it hits the ground. It is a common phenomenon in the western US. We do not see it as often in the east as it takes dry air and a high cloud base to cause the evaporation. It can cause clouds to take on the appearance of a jellyfish, with rounded tops and dangling tentacles.
>
> Stall Speed
>
> Aircraft fly by having air pass over the wings. If the speed of the aircraft falls below a certain minimum the wings can no longer provide the lift required to support the aircraft. That event is called a stall. This moment of stall can be (often is) abrupt. With adequate altitude the aircraft pitches down, regains flying speed and returns to controlled flight. All pilots are trained and practice stall recovery regularly. Stall speed is the minimum speed the aircraft can be flown controllably.
>
> Sink
>
> Gliders fly long distances by locating rising air and climbing in that air. What goes up must come down: descending air is called sink.
>
>
> Microburst
>
> Microbursts are narrow columns of rapidly descending air. They are associated with thunderstorms but can be caused by other sources. The one featured in this report was likely caused by the virga. The snow/rain falling from the clouds above start cool and then further cool by evaporation. This cold air is more dense than the surrounding air and starts to sink. Given favorable conditions this air can accelerate. When this rapidly descending air meets the ground it spreads out to become a sudden horizontal wind: a gust. The best kitchen analogy is water flowing from your tap and hitting a plate in the sink. The falling water splashes out sideways.
>
> ASOS
>
> Automated Surface Observing System. This is an automated weather reporting system that continually broadcasts the local (on airport) conditions.
>
> ---- End glossary ---------------------------------------------------------------------------------------------------
>
>
> Four gliders flew out of Rifle on June 9th 2022. We all launched around 11:00 and moved to the north side of the valley. It was tough to find that first good climb, but Shmulik found one, leaving the rest of us floundering low. Eventually we did get away. Long story short we all ended up going in different directions, all having great flights. They were not without challenges but nothing spooky, just enough work to be rewarding. In a flight of about 600 km, Shmulik made his goal of Duchesne UT, and was happy about that. We made plans to be on the ground at 6:00 and all converged on the Rifle area in time for that.
>
> There was virga in the area, and it got my attention as Shmulik had warned me on a previous trip to be careful with local virga. I was listening intently to the ASOS for wind or gusts, letting it repeat 5 or 6 times with the exact same report: 9 kts straight down the runway; no gusts. Later, as we got ready to land, the same benign report. OK I thought - the virga is clearly a non-issue. As we will learn, it was the whole issue.
>
> There was virga over the airport (elevation 5537 ft) and to the north of the valley, and northeast as well. None of the wisps extended below 11,000 ft (cloud base was approximately 19,000). Cloud cover was scattered. The clouds producing virga were not towering - they were perhaps a bit bigger than non-producing clouds, but not much. It was a point of interest to me as we don't see a lot of it in the eastern US - I was wondering what drove the difference.
>
> Shmulik and I discussed the landing order: as he was a bit lower we agreed he would go first. After we decided this, we heard a Challenger jet announce “Taxiing to 26 for takeoff”. That was the runway we would use to land.
>
> Rifle has a moderate amount of bizjet traffic; not constant but present. We always try to accommodate and be polite citizens. Shmulik called the Challenger and offered to delay but got no reply. I was still high so it was no problem for me. He tried again, with no reply. It’s worth noting that Shmulik had a close call in the past: a jet pulled onto the runway in front of him with no radio call. This near miss was avoided only by the jet taking off immediately in front of him. I am sure he did not want to repeat that. I speculate that the Challenger was on a different frequency temporarily, perhaps the ASOS.
>
> As he descended, he called that he was in heavy sink and was going to make left traffic for Runway 26 (for which the normal traffic pattern is right). Shortly after this a call came from the Challenger that there was a glider crash.
>
> I was not sure I’d heard it correctly so I asked for clarification. “There has been a glider crash and we see no movement.” They truly had a front-row seat, as moments before they were hit by a gust so strong that they had rotated their jet to avoid a compressor stall.
>
> I then asked if the runway was clear, was told yes, then landed uneventfully into the 9 mph headwinds. I am not sure of the time between our landings - I would guess it was 5 min. The other glider pilots landed without problems, though all could see the wreckage of our friend’s aircraft which left no doubt as to the outcome.
>
> The last moments of the crash were recorded by an airport security camera.. We were allowed to view the footage (but not record it). It showed Shmulik in a moderately steep turn, apparently carrying a lot of speed. In the background you can see dust and gravel being blown by the gust. Then at 90 deg to the runway and 150 to 200 ft you can see the inside wing start to drop and the nose go down. There was no opportunity to recover and it hit the ground hard, thankfully just out of camera view.
>
> The Rifle ASOS recorded a gust of 43 mph from the south: a 100-degree shift in direction, putting it right on his tail.
>
> My analysis and proposed scenario are as follows:
>
> The virga produced a microburst directly over Shmulik as he was waiting for the jet. He expedited his landing trying to fly out of what was likely epic sink. While his base leg was low it looked high enough to make the runway with plenty of energy to flare and roll out. But he then got hit from behind or descended into winds in excess of 40 kts and perhaps as much as 50, stalling the aircraft and removing any opportunity for control.
>
> One of the most difficult aspects of this accident is that, given the information available to the pilot, it is hard to picture what anyone would have done differently. This truly seems like the hand of God. There is discussion in another thread about the yellow triangle. Here is a case that would require 60 over stall speed to maintain even a narrow margin. How many people do you know that would plan to come over the numbers at 100+ on a day that is blowing steady 9 straight down the runway?
>
> As has been noted, Shmulik was a very experienced and skilled pilot. He had more flights and time in gliders from Rifle than anyone. We all want to learn from accidents, especially what were the pilot errors we might avoid. This is a hard one to gain insight from other than this: Some atmospheric events are bigger than our plastic airplanes.
>
> RR
Thank you very much for making this information available and these accidents are difficult to understand. OBTP

On Tuesday, June 14, 2022 at 2:01:02 PM UTC-5, youngbl...@gmail.com wrote:
> On Tuesday, June 14, 2022 at 12:31:08 AM UTC-4, John Good wrote:
> > This is a first-hand account of the crash, by Rick Roelke (who also flew from Rifle CO on June 9):
> >
> > ------------------------------------------------
> >
> >
> > I originally wrote this to be read by glider pilots. But it became apparent it would also be of interest to non-pilot friends and relatives wishing to better understand how this accident could happen to such a talented and experienced pilot. To aid that understanding I will preface the report with a glossary of pertinent terms. To my pilot readers: feel free to skip this section. I also ask forgiveness for abbreviated explanations: this is not intended as a textbook, but merely to provide context for laypersons.
> >
> > Virga
> >
> > Virga is snow/rain falling from a cloud, that evaporates before it hits the ground. It is a common phenomenon in the western US. We do not see it as often in the east as it takes dry air and a high cloud base to cause the evaporation. It can cause clouds to take on the appearance of a jellyfish, with rounded tops and dangling tentacles.
> >
> > Stall Speed
> >
> > Aircraft fly by having air pass over the wings. If the speed of the aircraft falls below a certain minimum the wings can no longer provide the lift required to support the aircraft. That event is called a stall. This moment of stall can be (often is) abrupt. With adequate altitude the aircraft pitches down, regains flying speed and returns to controlled flight. All pilots are trained and practice stall recovery regularly. Stall speed is the minimum speed the aircraft can be flown controllably.
> >
> > Sink
> >
> > Gliders fly long distances by locating rising air and climbing in that air. What goes up must come down: descending air is called sink.
> >
> >
> > Microburst
> >
> > Microbursts are narrow columns of rapidly descending air. They are associated with thunderstorms but can be caused by other sources. The one featured in this report was likely caused by the virga. The snow/rain falling from the clouds above start cool and then further cool by evaporation. This cold air is more dense than the surrounding air and starts to sink. Given favorable conditions this air can accelerate. When this rapidly descending air meets the ground it spreads out to become a sudden horizontal wind: a gust. The best kitchen analogy is water flowing from your tap and hitting a plate in the sink. The falling water splashes out sideways.
> >
> > ASOS
> >
> > Automated Surface Observing System. This is an automated weather reporting system that continually broadcasts the local (on airport) conditions.
> >
> > ---- End glossary ---------------------------------------------------------------------------------------------------
> >
> >
> > Four gliders flew out of Rifle on June 9th 2022. We all launched around 11:00 and moved to the north side of the valley. It was tough to find that first good climb, but Shmulik found one, leaving the rest of us floundering low. Eventually we did get away. Long story short we all ended up going in different directions, all having great flights. They were not without challenges but nothing spooky, just enough work to be rewarding. In a flight of about 600 km, Shmulik made his goal of Duchesne UT, and was happy about that. We made plans to be on the ground at 6:00 and all converged on the Rifle area in time for that.
> >
> > There was virga in the area, and it got my attention as Shmulik had warned me on a previous trip to be careful with local virga. I was listening intently to the ASOS for wind or gusts, letting it repeat 5 or 6 times with the exact same report: 9 kts straight down the runway; no gusts. Later, as we got ready to land, the same benign report. OK I thought - the virga is clearly a non-issue. As we will learn, it was the whole issue.
> >
> > There was virga over the airport (elevation 5537 ft) and to the north of the valley, and northeast as well. None of the wisps extended below 11,000 ft (cloud base was approximately 19,000). Cloud cover was scattered. The clouds producing virga were not towering - they were perhaps a bit bigger than non-producing clouds, but not much. It was a point of interest to me as we don't see a lot of it in the eastern US - I was wondering what drove the difference.
> >
> > Shmulik and I discussed the landing order: as he was a bit lower we agreed he would go first. After we decided this, we heard a Challenger jet announce “Taxiing to 26 for takeoff”. That was the runway we would use to land.
> >
> > Rifle has a moderate amount of bizjet traffic; not constant but present.. We always try to accommodate and be polite citizens. Shmulik called the Challenger and offered to delay but got no reply. I was still high so it was no problem for me. He tried again, with no reply. It’s worth noting that Shmulik had a close call in the past: a jet pulled onto the runway in front of him with no radio call. This near miss was avoided only by the jet taking off immediately in front of him. I am sure he did not want to repeat that. I speculate that the Challenger was on a different frequency temporarily, perhaps the ASOS.
> >
> > As he descended, he called that he was in heavy sink and was going to make left traffic for Runway 26 (for which the normal traffic pattern is right). Shortly after this a call came from the Challenger that there was a glider crash.
> >
> > I was not sure I’d heard it correctly so I asked for clarification. “There has been a glider crash and we see no movement.” They truly had a front-row seat, as moments before they were hit by a gust so strong that they had rotated their jet to avoid a compressor stall.
> >
> > I then asked if the runway was clear, was told yes, then landed uneventfully into the 9 mph headwinds. I am not sure of the time between our landings - I would guess it was 5 min. The other glider pilots landed without problems, though all could see the wreckage of our friend’s aircraft which left no doubt as to the outcome.
> >
> > The last moments of the crash were recorded by an airport security camera. We were allowed to view the footage (but not record it). It showed Shmulik in a moderately steep turn, apparently carrying a lot of speed. In the background you can see dust and gravel being blown by the gust. Then at 90 deg to the runway and 150 to 200 ft you can see the inside wing start to drop and the nose go down. There was no opportunity to recover and it hit the ground hard, thankfully just out of camera view.
> >
> > The Rifle ASOS recorded a gust of 43 mph from the south: a 100-degree shift in direction, putting it right on his tail.
> >
> > My analysis and proposed scenario are as follows:
> >
> > The virga produced a microburst directly over Shmulik as he was waiting for the jet. He expedited his landing trying to fly out of what was likely epic sink. While his base leg was low it looked high enough to make the runway with plenty of energy to flare and roll out. But he then got hit from behind or descended into winds in excess of 40 kts and perhaps as much as 50, stalling the aircraft and removing any opportunity for control.
> >
> > One of the most difficult aspects of this accident is that, given the information available to the pilot, it is hard to picture what anyone would have done differently. This truly seems like the hand of God. There is discussion in another thread about the yellow triangle. Here is a case that would require 60 over stall speed to maintain even a narrow margin. How many people do you know that would plan to come over the numbers at 100+ on a day that is blowing steady 9 straight down the runway?
> >
> > As has been noted, Shmulik was a very experienced and skilled pilot. He had more flights and time in gliders from Rifle than anyone. We all want to learn from accidents, especially what were the pilot errors we might avoid. This is a hard one to gain insight from other than this: Some atmospheric events are bigger than our plastic airplanes.
> >
> > RR
> Thank you very much for making this information available and these accidents are difficult to understand. OBTP

I note that he was on base leg at 150-200' which is well below standard spin recovery altitude.

On Tuesday, June 14, 2022 at 8:53:31 PM UTC-5, Barbara & Anthony Way wrote:
> On Tuesday, June 14, 2022 at 2:01:02 PM UTC-5, youngbl...@gmail.com wrote:
> > On Tuesday, June 14, 2022 at 12:31:08 AM UTC-4, John Good wrote:
> > > This is a first-hand account of the crash, by Rick Roelke (who also flew from Rifle CO on June 9):
> > >
> > > ------------------------------------------------
> > >
> > >
> > > I originally wrote this to be read by glider pilots. But it became apparent it would also be of interest to non-pilot friends and relatives wishing to better understand how this accident could happen to such a talented and experienced pilot. To aid that understanding I will preface the report with a glossary of pertinent terms. To my pilot readers: feel free to skip this section. I also ask forgiveness for abbreviated explanations: this is not intended as a textbook, but merely to provide context for laypersons.
> > >
> > > Virga
> > >
> > > Virga is snow/rain falling from a cloud, that evaporates before it hits the ground. It is a common phenomenon in the western US. We do not see it as often in the east as it takes dry air and a high cloud base to cause the evaporation. It can cause clouds to take on the appearance of a jellyfish, with rounded tops and dangling tentacles.
> > >
> > > Stall Speed
> > >
> > > Aircraft fly by having air pass over the wings. If the speed of the aircraft falls below a certain minimum the wings can no longer provide the lift required to support the aircraft. That event is called a stall. This moment of stall can be (often is) abrupt. With adequate altitude the aircraft pitches down, regains flying speed and returns to controlled flight. All pilots are trained and practice stall recovery regularly. Stall speed is the minimum speed the aircraft can be flown controllably.
> > >
> > > Sink
> > >
> > > Gliders fly long distances by locating rising air and climbing in that air. What goes up must come down: descending air is called sink.
> > >
> > >
> > > Microburst
> > >
> > > Microbursts are narrow columns of rapidly descending air. They are associated with thunderstorms but can be caused by other sources. The one featured in this report was likely caused by the virga. The snow/rain falling from the clouds above start cool and then further cool by evaporation. This cold air is more dense than the surrounding air and starts to sink. Given favorable conditions this air can accelerate. When this rapidly descending air meets the ground it spreads out to become a sudden horizontal wind: a gust. The best kitchen analogy is water flowing from your tap and hitting a plate in the sink. The falling water splashes out sideways.
> > >
> > > ASOS
> > >
> > > Automated Surface Observing System. This is an automated weather reporting system that continually broadcasts the local (on airport) conditions.
> > >
> > > ---- End glossary ---------------------------------------------------------------------------------------------------
> > >
> > >
> > > Four gliders flew out of Rifle on June 9th 2022. We all launched around 11:00 and moved to the north side of the valley. It was tough to find that first good climb, but Shmulik found one, leaving the rest of us floundering low. Eventually we did get away. Long story short we all ended up going in different directions, all having great flights. They were not without challenges but nothing spooky, just enough work to be rewarding. In a flight of about 600 km, Shmulik made his goal of Duchesne UT, and was happy about that. We made plans to be on the ground at 6:00 and all converged on the Rifle area in time for that.
> > >
> > > There was virga in the area, and it got my attention as Shmulik had warned me on a previous trip to be careful with local virga. I was listening intently to the ASOS for wind or gusts, letting it repeat 5 or 6 times with the exact same report: 9 kts straight down the runway; no gusts. Later, as we got ready to land, the same benign report. OK I thought - the virga is clearly a non-issue. As we will learn, it was the whole issue.
> > >
> > > There was virga over the airport (elevation 5537 ft) and to the north of the valley, and northeast as well. None of the wisps extended below 11,000 ft (cloud base was approximately 19,000). Cloud cover was scattered. The clouds producing virga were not towering - they were perhaps a bit bigger than non-producing clouds, but not much. It was a point of interest to me as we don't see a lot of it in the eastern US - I was wondering what drove the difference.
> > >
> > > Shmulik and I discussed the landing order: as he was a bit lower we agreed he would go first. After we decided this, we heard a Challenger jet announce “Taxiing to 26 for takeoff”. That was the runway we would use to land.
> > >
> > > Rifle has a moderate amount of bizjet traffic; not constant but present. We always try to accommodate and be polite citizens. Shmulik called the Challenger and offered to delay but got no reply. I was still high so it was no problem for me. He tried again, with no reply. It’s worth noting that Shmulik had a close call in the past: a jet pulled onto the runway in front of him with no radio call. This near miss was avoided only by the jet taking off immediately in front of him. I am sure he did not want to repeat that. I speculate that the Challenger was on a different frequency temporarily, perhaps the ASOS.
> > >
> > > As he descended, he called that he was in heavy sink and was going to make left traffic for Runway 26 (for which the normal traffic pattern is right). Shortly after this a call came from the Challenger that there was a glider crash.
> > >
> > > I was not sure I’d heard it correctly so I asked for clarification. “There has been a glider crash and we see no movement.” They truly had a front-row seat, as moments before they were hit by a gust so strong that they had rotated their jet to avoid a compressor stall.
> > >
> > > I then asked if the runway was clear, was told yes, then landed uneventfully into the 9 mph headwinds. I am not sure of the time between our landings - I would guess it was 5 min. The other glider pilots landed without problems, though all could see the wreckage of our friend’s aircraft which left no doubt as to the outcome.
> > >
> > > The last moments of the crash were recorded by an airport security camera. We were allowed to view the footage (but not record it). It showed Shmulik in a moderately steep turn, apparently carrying a lot of speed. In the background you can see dust and gravel being blown by the gust. Then at 90 deg to the runway and 150 to 200 ft you can see the inside wing start to drop and the nose go down. There was no opportunity to recover and it hit the ground hard, thankfully just out of camera view.
> > >
> > > The Rifle ASOS recorded a gust of 43 mph from the south: a 100-degree shift in direction, putting it right on his tail.
> > >
> > > My analysis and proposed scenario are as follows:
> > >
> > > The virga produced a microburst directly over Shmulik as he was waiting for the jet. He expedited his landing trying to fly out of what was likely epic sink. While his base leg was low it looked high enough to make the runway with plenty of energy to flare and roll out. But he then got hit from behind or descended into winds in excess of 40 kts and perhaps as much as 50, stalling the aircraft and removing any opportunity for control.
> > >
> > > One of the most difficult aspects of this accident is that, given the information available to the pilot, it is hard to picture what anyone would have done differently. This truly seems like the hand of God. There is discussion in another thread about the yellow triangle. Here is a case that would require 60 over stall speed to maintain even a narrow margin. How many people do you know that would plan to come over the numbers at 100+ on a day that is blowing steady 9 straight down the runway?
> > >
> > > As has been noted, Shmulik was a very experienced and skilled pilot. He had more flights and time in gliders from Rifle than anyone. We all want to learn from accidents, especially what were the pilot errors we might avoid. This is a hard one to gain insight from other than this: Some atmospheric events are bigger than our plastic airplanes.
> > >
> > > RR
> > Thank you very much for making this information available and these accidents are difficult to understand. OBTP
> I note that he was on base leg at 150-200' which is well below standard spin recovery altitude.

On Tuesday, June 14, 2022 at 8:53:31 PM UTC-5, Barbara & Anthony Way wrote:
> On Tuesday, June 14, 2022 at 2:01:02 PM UTC-5, youngbl...@gmail.com wrote:
> > On Tuesday, June 14, 2022 at 12:31:08 AM UTC-4, John Good wrote:
> > > This is a first-hand account of the crash, by Rick Roelke (who also flew from Rifle CO on June 9):
> > >
> > > ------------------------------------------------
> > >
> > >
> > > I originally wrote this to be read by glider pilots. But it became apparent it would also be of interest to non-pilot friends and relatives wishing to better understand how this accident could happen to such a talented and experienced pilot. To aid that understanding I will preface the report with a glossary of pertinent terms. To my pilot readers: feel free to skip this section. I also ask forgiveness for abbreviated explanations: this is not intended as a textbook, but merely to provide context for laypersons.
> > >
> > > Virga
> > >
> > > Virga is snow/rain falling from a cloud, that evaporates before it hits the ground. It is a common phenomenon in the western US. We do not see it as often in the east as it takes dry air and a high cloud base to cause the evaporation. It can cause clouds to take on the appearance of a jellyfish, with rounded tops and dangling tentacles.
> > >
> > > Stall Speed
> > >
> > > Aircraft fly by having air pass over the wings. If the speed of the aircraft falls below a certain minimum the wings can no longer provide the lift required to support the aircraft. That event is called a stall. This moment of stall can be (often is) abrupt. With adequate altitude the aircraft pitches down, regains flying speed and returns to controlled flight. All pilots are trained and practice stall recovery regularly. Stall speed is the minimum speed the aircraft can be flown controllably.
> > >
> > > Sink
> > >
> > > Gliders fly long distances by locating rising air and climbing in that air. What goes up must come down: descending air is called sink.
> > >
> > >
> > > Microburst
> > >
> > > Microbursts are narrow columns of rapidly descending air. They are associated with thunderstorms but can be caused by other sources. The one featured in this report was likely caused by the virga. The snow/rain falling from the clouds above start cool and then further cool by evaporation. This cold air is more dense than the surrounding air and starts to sink. Given favorable conditions this air can accelerate. When this rapidly descending air meets the ground it spreads out to become a sudden horizontal wind: a gust. The best kitchen analogy is water flowing from your tap and hitting a plate in the sink. The falling water splashes out sideways.
> > >
> > > ASOS
> > >
> > > Automated Surface Observing System. This is an automated weather reporting system that continually broadcasts the local (on airport) conditions.
> > >
> > > ---- End glossary ---------------------------------------------------------------------------------------------------
> > >
> > >
> > > Four gliders flew out of Rifle on June 9th 2022. We all launched around 11:00 and moved to the north side of the valley. It was tough to find that first good climb, but Shmulik found one, leaving the rest of us floundering low. Eventually we did get away. Long story short we all ended up going in different directions, all having great flights. They were not without challenges but nothing spooky, just enough work to be rewarding. In a flight of about 600 km, Shmulik made his goal of Duchesne UT, and was happy about that. We made plans to be on the ground at 6:00 and all converged on the Rifle area in time for that.
> > >
> > > There was virga in the area, and it got my attention as Shmulik had warned me on a previous trip to be careful with local virga. I was listening intently to the ASOS for wind or gusts, letting it repeat 5 or 6 times with the exact same report: 9 kts straight down the runway; no gusts. Later, as we got ready to land, the same benign report. OK I thought - the virga is clearly a non-issue. As we will learn, it was the whole issue.
> > >
> > > There was virga over the airport (elevation 5537 ft) and to the north of the valley, and northeast as well. None of the wisps extended below 11,000 ft (cloud base was approximately 19,000). Cloud cover was scattered. The clouds producing virga were not towering - they were perhaps a bit bigger than non-producing clouds, but not much. It was a point of interest to me as we don't see a lot of it in the eastern US - I was wondering what drove the difference.
> > >
> > > Shmulik and I discussed the landing order: as he was a bit lower we agreed he would go first. After we decided this, we heard a Challenger jet announce “Taxiing to 26 for takeoff”. That was the runway we would use to land.
> > >
> > > Rifle has a moderate amount of bizjet traffic; not constant but present. We always try to accommodate and be polite citizens. Shmulik called the Challenger and offered to delay but got no reply. I was still high so it was no problem for me. He tried again, with no reply. It’s worth noting that Shmulik had a close call in the past: a jet pulled onto the runway in front of him with no radio call. This near miss was avoided only by the jet taking off immediately in front of him. I am sure he did not want to repeat that. I speculate that the Challenger was on a different frequency temporarily, perhaps the ASOS.
> > >
> > > As he descended, he called that he was in heavy sink and was going to make left traffic for Runway 26 (for which the normal traffic pattern is right). Shortly after this a call came from the Challenger that there was a glider crash.
> > >
> > > I was not sure I’d heard it correctly so I asked for clarification. “There has been a glider crash and we see no movement.” They truly had a front-row seat, as moments before they were hit by a gust so strong that they had rotated their jet to avoid a compressor stall.
> > >
> > > I then asked if the runway was clear, was told yes, then landed uneventfully into the 9 mph headwinds. I am not sure of the time between our landings - I would guess it was 5 min. The other glider pilots landed without problems, though all could see the wreckage of our friend’s aircraft which left no doubt as to the outcome.
> > >
> > > The last moments of the crash were recorded by an airport security camera. We were allowed to view the footage (but not record it). It showed Shmulik in a moderately steep turn, apparently carrying a lot of speed. In the background you can see dust and gravel being blown by the gust. Then at 90 deg to the runway and 150 to 200 ft you can see the inside wing start to drop and the nose go down. There was no opportunity to recover and it hit the ground hard, thankfully just out of camera view.
> > >
> > > The Rifle ASOS recorded a gust of 43 mph from the south: a 100-degree shift in direction, putting it right on his tail.
> > >
> > > My analysis and proposed scenario are as follows:
> > >
> > > The virga produced a microburst directly over Shmulik as he was waiting for the jet. He expedited his landing trying to fly out of what was likely epic sink. While his base leg was low it looked high enough to make the runway with plenty of energy to flare and roll out. But he then got hit from behind or descended into winds in excess of 40 kts and perhaps as much as 50, stalling the aircraft and removing any opportunity for control.
> > >
> > > One of the most difficult aspects of this accident is that, given the information available to the pilot, it is hard to picture what anyone would have done differently. This truly seems like the hand of God. There is discussion in another thread about the yellow triangle. Here is a case that would require 60 over stall speed to maintain even a narrow margin. How many people do you know that would plan to come over the numbers at 100+ on a day that is blowing steady 9 straight down the runway?
> > >
> > > As has been noted, Shmulik was a very experienced and skilled pilot. He had more flights and time in gliders from Rifle than anyone. We all want to learn from accidents, especially what were the pilot errors we might avoid. This is a hard one to gain insight from other than this: Some atmospheric events are bigger than our plastic airplanes.
> > >
> > > RR
> > Thank you very much for making this information available and these accidents are difficult to understand. OBTP
> I note that he was on base leg at 150-200' which is well below standard spin recovery altitude.

Thanks for sharing the accident info. I have learned that having no explaination can create wild speculation. Condolences to Shmulik's friends and family.

Paul
9P & IMO

On 6/10/2022 10:09 AM, John Good wrote:
> After a long flight in good conditions, Shmulik Dimenstein yesterday died in the crash of his HpH Shark glider, near his home airport at Rifle, Colorado. The cause of the crash is under investigation; possibly relevant is a singular gust of 43 kts (recorded by the airport ASOS near the time of the crash) on an otherwise benign day.
>
> Even a quick look at OLC results over the past several years will show Shmulik’s skill at – and love for – long flights among the mountains of western Colorado (and neighboring states). Less apparent will be his extraordinary hospitality to those who came to fly gliders at Rifle. He was a valued friend not only to glider pilots but also to the Rifle airport staff and the local FBO.

Terrible news. Shmulik was a great guy and always friendly to all. We
met and flew together back at Chester, IIRC way back before the
good-ole-buys let Charlie CD, and other sites since. Shmulik just
recently called and encouraged me to come visit Rifle, sadly I didn't
manage to do so.
RIP Shmulik, we'll miss you.

PS: What we do is dangerous. Shmulik was my 26th friend to die gliding.

Dave, you would be better served to shitcan that 'PS'.

R

On Monday, June 13, 2022 at 9:31:08 PM UTC-7, John Good wrote:
> This is a first-hand account of the crash, by Rick Roelke (who also flew from Rifle CO on June 9):

Thank you for posting and my condolences to the friends and family of Schmulik. While I didn't know him, I saw his many great flights on OLC.

Many of us have seen microbursts from a distance or even been in them such as 5Zs account and they've always been a concern to all aviators.
I found this illustration particularly insightful. Even though it shows a Cessna, imagine a glider at position 2 in the landing pattern/slowed for the pattern.
With a strong enough outflow of 40 kts or more there is technically no way out in any direction. I'm not saying this is what happened precisely in this case but something to consider as the strong summer conditions are upon us in the northern hemisphere.

https://www.gleimaviation.com/2020/07/10/microburst-hazards/

Darren

I had just completed my turn to final and was putting down landing flap when it suddenly went very quiet. Nose and wing dropped before I went to negative flap and forward on the stick. Came out the bottom with 65 kt TAS and 15' and had to climb to clear obstacles.

This chart shows wind in the x and z axes along with altitude and distance in one second intervals:

https://drive.google.com/file/d/0B1NeKc6B2S3XQzlZWjBZY2JvNEE/view?usp=drivesdk&resourcekey=0-i1znGTz912WvAoscv73RhQ

Some similarities to the Gleim diagram referenced by Darren, but no big clouds.

Sometimes it's appropriate to act in a non-standard way.

I was running from a thunderstorm in Colorado decades ago and, after
overflying the airport, turned downwind and base when the outflow hit.
On base I was at maximum speed for flaps and landing gear and, rather
than turn final and accept that humongous cross wind, I simply landed
straight ahead, across the runway, infield, taxiway, and apron. I then
flew the glider on the ground until the storm passed.

I'm not saying that Schmuel had any chance of saving himself, just a
reminder that there is more than one way to get safely on the ground.

Dan
5J

On 6/15/22 13:30, George Haeh wrote:
> I had just completed my turn to final and was putting down landing flap when it suddenly went very quiet. Nose and wing dropped before I went to negative flap and forward on the stick. Came out the bottom with 65 kt TAS and 15' and had to climb to clear obstacles.
>
> This chart shows wind in the x and z axes along with altitude and distance in one second intervals:
>
> https://drive.google.com/file/d/0B1NeKc6B2S3XQzlZWjBZY2JvNEE/view?usp=drivesdk&resourcekey=0-i1znGTz912WvAoscv73RhQ
>
> Some similarities to the Gleim diagram referenced by Darren, but no big clouds.
>
>

On Wednesday, June 15, 2022 at 5:03:43 PM UTC-4, Dan Marotta wrote:
> Sometimes it's appropriate to act in a non standard way.

To that end, Shmulik had briefed us on landing on a field adjacent to 26 if the winds were cross and strong. Walked the field with me, and explained the approach. In this case the outflow was the wrong way to use it, but more importantly I dont think there were signs of the outflow until he descended into it.

I've stood on the ground at Rieti and watched thunderstorms over mountains to the west. Then the downdraft from these crossed the site and not long later fired off new storms over the nearer mountains to the east. Then those too produced downdrafts, creating about 30 or 40 knots crosswind on the airfield, coinciding with arrival of the earliest finishers.

When people are coming in at maybe 120 knots or more, maybe they don't notice quite how strong the wind is, and only a couple elected to turn gently right, let the wind drift them out a bit, then left and land across the usual runway direction. For a while I was worried one of the world's most experienced coaches was going to either spin from his 210 degree final turn, or undershoot and land on a hangar. Not much airbrake.

On Wednesday, 15 June 2022 at 22:03:43 UTC+1, Dan Marotta wrote:
> Sometimes it's appropriate to act in a non-standard way.
>
> I was running from a thunderstorm in Colorado decades ago and, after
> overflying the airport, turned downwind and base when the outflow hit.
> On base I was at maximum speed for flaps and landing gear and, rather
> than turn final and accept that humongous cross wind, I simply landed
> straight ahead, across the runway, infield, taxiway, and apron. I then
> flew the glider on the ground until the storm passed.
>
> I'm not saying that Schmuel had any chance of saving himself, just a
> reminder that there is more than one way to get safely on the ground.
>
> Dan
> 5J

On Thursday, June 16, 2022 at 2:55:51 AM UTC-6, andy l wrote:
> I've stood on the ground at Rieti and watched thunderstorms over mountains to the west. Then the downdraft from these crossed the site and not long later fired off new storms over the nearer mountains to the east. Then those too produced downdrafts, creating about 30 or 40 knots crosswind on the airfield, coinciding with arrival of the earliest finishers.
>
> When people are coming in at maybe 120 knots or more, maybe they don't notice quite how strong the wind is, and only a couple elected to turn gently right, let the wind drift them out a bit, then left and land across the usual runway direction. For a while I was worried one of the world's most experienced coaches was going to either spin from his 210 degree final turn, or undershoot and land on a hangar. Not much airbrake.
> On Wednesday, 15 June 2022 at 22:03:43 UTC+1, Dan Marotta wrote:
> > Sometimes it's appropriate to act in a non-standard way.
> >
> > I was running from a thunderstorm in Colorado decades ago and, after
> > overflying the airport, turned downwind and base when the outflow hit.
> > On base I was at maximum speed for flaps and landing gear and, rather
> > than turn final and accept that humongous cross wind, I simply landed
> > straight ahead, across the runway, infield, taxiway, and apron. I then
> > flew the glider on the ground until the storm passed.
> >
> > I'm not saying that Schmuel had any chance of saving himself, just a
> > reminder that there is more than one way to get safely on the ground.
> >
> > Dan
> > 5J

Microbursts are extreme cases of wind shear, which have taken down heavy airliners (L1011 at DFW, for example, https://en.wikipedia.org/wiki/Delta_Air_Lines_Flight_191). This AC was issued by the FAA as a response, in part, to this accident:
https://www.faa.gov/documentLibrary/media/Advisory_Circular/AC00-54.pdf
While it is now 34 years old, all the info in it is still very relevant. Microbursts can occur anywhere but are much more prevalent in Colorado and Florida. The time duration of microbursts is short, 10 to 20 minutes, so just because the guy in front of you had normal winds doesn't mean that you will. We fly in conditions during which convection is present, and land most often when dissipation is occurring, the most likely time for microbursts.

You have three primary tools at your disposal to deal with microbursts:
1. Avoidance
2. Airspeed
3. Reaction
Since the lifetime of microbursts is relatively short, if you have ANY suspicion that it is happening, or about to happen, wait it out. Microbursts likely will kick up dust on the ground, so any indication of blowing dust is a tell. Once you commit to land and the conditions for microburst MAY be present, carry extra airspeed in the pattern, A LOT of extra airspeed (fly the pattern at 90 kt - that speed can be bled off quickly on short final). It would take a tail gust of 50 kt to stall you at this airspeed.

If such a tail gust DOES hit you, it is vital that you push the nose down and dive at the ground. This will feel VERY uncomfortable but is the one thing maneuver you have at your disposal. Failure to do this WILL result in a stall/spin low to the ground, which is non-recoverable, so avoiding this outcome is the top priority (this happened to Shmulik). Note that you will already be dropping fast when this happens and the ground will be rushing up at you, so your instinct, which must be fought, will be to pull up on the stick. An important thing to remember is that close to the ground the vertical air motion will flatten out and your vertical down rate will cease, although you will still have a tailwind. You will also have ground effect in your favor (if you are within a wingspan of the ground). The area of a microburst is small, and you have a good chance of flying out of it.

Tom