Severe (or more) turbulence... how common?

Flying from Palo Alto to Santa Monica yesterday, we hit (I think) a rotor
coming over the mountains north of LA. We'd had some fairly strong
up and downdrafts, though nothing really unpleasant, when suddenly
we were going DOWN - about 2000' in 10 seconds or so, everything
stuck to the roof for maybe 5-10 seconds. It was an interesting ride...
most things landed shortly afterwards (and I even found a flashlight that
had disappeared) although my E6B remained lodged somewhere
and fell on my head on final.

Afterwards, my wife asked me how often this happens... once per
flying lifetime, much less, every few years. I couldn't answer... for sure
the first time in my 600 hours, but that's not much.

So here's my informal sample... how many people here have had a
similar experience? Anyone care to guess how unlikely this it?

(And to forestall, or try to, the people who tell me I should know something
about mountain flying, yes I HAVE read Sparky Iverson's book, and
anyway living in the Bay Area it's hard to go anywhere much without
overflying mountains. I was over 2000' above terrain too, 9500'
over a ridgeline at about 6000').

John

Could be? What were the winds at, when you were flying over the mountains
(I assume you were actually flying through the pass?) ?

One day, early in my primary training (way back when I was still at the
'evil' FBO grin, my instructor and I, were flying out along the coast,
headed to Half Moon Bay Airport to practice some t/o & landings at another
airport. Just as we were passing over the water (with the plan of flying
along the coastline with highway one on our right) without any warning the
plane just 'dropped' in the manner you described. The funny part about the
whole thing is that my instructor had, moments earlier in the flight, been
explaining how there is smooth laminar flow over the ocean. I really wasn't
scared (I was probably at my 9th or 10th hour by then) when it happened,
mainly because my instructor took it right in stride. I do remember he
called in a PIREP for CAT (clear air turbulence) as he told me that it
should be something that some other pilots be made aware of.

By the way, have you seen the Sparky I's video on mountain flying - some
great footage and visual instruction aids - since you mentioned the book.

--
--
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Good Flights!

Cecil
PP-ASEL

Check out my personal flying adventures complete with pictures and text at:
www.bayareapilot.com

"I fly because it releases my mind from the tyranny of petty things."
- Antoine de Saint-Exupery -

"We who fly, do so for the love of flying. We are alive in the air with
this miracle that lies in our hands and beneath our feet"
- Cecil Day Lewis -
"John Harper" wrote in message
news:1075704296.323452@sj-nntpcache-5...
Flying from Palo Alto to Santa Monica yesterday, we hit (I think) a rotor
coming over the mountains north of LA. We'd had some fairly strong
up and downdrafts, though nothing really unpleasant, when suddenly
we were going DOWN - about 2000' in 10 seconds or so, everything
stuck to the roof for maybe 5-10 seconds. It was an interesting ride...
most things landed shortly afterwards (and I even found a flashlight that
had disappeared) although my E6B remained lodged somewhere
and fell on my head on final.

Afterwards, my wife asked me how often this happens... once per
flying lifetime, much less, every few years. I couldn't answer... for sure
the first time in my 600 hours, but that's not much.

So here's my informal sample... how many people here have had a
similar experience? Anyone care to guess how unlikely this it?

(And to forestall, or try to, the people who tell me I should know
something
about mountain flying, yes I HAVE read Sparky Iverson's book, and
anyway living in the Bay Area it's hard to go anywhere much without
overflying mountains. I was over 2000' above terrain too, 9500'
over a ridgeline at about 6000').

John

flying out along the coast,
headed to Half Moon Bay Airport to practice some t/o & landings at another
airport.

same thing happened to me with 2 friends doing a Bay tour last week.
Beautiful calm and unlimited visibility with no bumps whatsoever.
Then we're flying down the coast just north of Half Moon Bay just
outside the 7nm ring of the SFO Class B and a couple of miles (?)
out over the ocean when we hit a medium bump. Just a quick
short one but it came from no where.

then also into 20 hours or so of my flying life near OSI VOR,
plan dropped quite hard, engine paused for a second and everything
continued.

That stuff is scary for a few minutes.


Where was the rotor (?) that you experienced between LA and SF?

Gerald

In article .net,
Gerald Sylvester wrote:
flying out along the coast,
headed to Half Moon Bay Airport to practice some t/o & landings at another
airport.

same thing happened to me with 2 friends doing a Bay tour last week.
Beautiful calm and unlimited visibility with no bumps whatsoever.
Then we're flying down the coast just north of Half Moon Bay just
outside the 7nm ring of the SFO Class B and a couple of miles (?)
out over the ocean when we hit a medium bump. Just a quick
short one but it came from no where.

In that area, it is quite possibly wake turbulence from planes
departing SFO. A friend cracked his head on the ceiling after a
wake turbulence encounter. He saw the plane's path, and was above
it, but the wind was out of the west, and the wake turbulence blew
into his flight path.

John
--
John Clear - http://www.panix.com/~jac

"John Harper" wrote in message

Flying from Palo Alto to Santa Monica yesterday, we hit (I think) a rotor

John.....
IIRC, the standard for severe turbulence includes near total inability to
control the aircraft while in its effect.

For me, that happened once in 26 years.

Regards,

John Gaquin
B727, B747

Are you sure about those figures? If the acceleration was constant. 2000'
in 10 seconds is a vertical speed of zero increasing to 24,000fpm (270mph+)
in five seconds and then back to zero in another five seconds. I have never
heard of anything like it and certainly never experienced anything similiar.

I have experienced vertical speeds of 5000fpm in mountan waves systems on
the east side of the Sierra near Minden, but those were with 100kt+ winds at
ridge level (trees knocked down, semis turned over, planes beaking tie down
ropes ect)

Mike
MU-2

"John Harper" wrote in message
news:1075704296.323452@sj-nntpcache-5...
Flying from Palo Alto to Santa Monica yesterday, we hit (I think) a rotor
coming over the mountains north of LA. We'd had some fairly strong
up and downdrafts, though nothing really unpleasant, when suddenly
we were going DOWN - about 2000' in 10 seconds or so, everything
stuck to the roof for maybe 5-10 seconds. It was an interesting ride...
most things landed shortly afterwards (and I even found a flashlight that
had disappeared) although my E6B remained lodged somewhere
and fell on my head on final.

Afterwards, my wife asked me how often this happens... once per
flying lifetime, much less, every few years. I couldn't answer... for sure
the first time in my 600 hours, but that's not much.

So here's my informal sample... how many people here have had a
similar experience? Anyone care to guess how unlikely this it?

(And to forestall, or try to, the people who tell me I should know
something
about mountain flying, yes I HAVE read Sparky Iverson's book, and
anyway living in the Bay Area it's hard to go anywhere much without
overflying mountains. I was over 2000' above terrain too, 9500'
over a ridgeline at about 6000').

John

Yes, that's pretty much what my math came up with too. But for sure
I lost 2000' (I couldn't believe it when I looked at the altimeter after
recovering the plane - I'd been pretty focussed on the ASI since I
was close to redline). And I don't think the whole thing lasted more
than 10 seconds, although of course I wasn't timing it. Maybe it
was longer, but usually these things seem to last longer than they
really do, not less.

The terrain there is a bit special - there's a first ridgeline which is
at 6000-7500', then after a couple of miles there's a lower ridge
at around 4000', with a valley in between at about 2000'. I think
the only reason I recovered (much though I'd like to take credit for
my excellent airmanship :-) ) is that we flew through the downdraft.

I don't know whether this was "severe turbulence" according to
the definition. It was actually quite smooth, except that we were
going down at something around -1G. I did keep the plane under
control - my main concern being to avoid hitting Vne. We came out
about 30 degrees off heading. My wife says we did bank quite
steeply - she was looking out of the windshield, I was focussed on
the instruments. Whether it was "severe" or not, it was certainly quite
an experience, one I'm not in a big hurry to repeat.

John

"Mike Rapoport" wrote in message
ink.net...
Are you sure about those figures? If the acceleration was constant. 2000'
in 10 seconds is a vertical speed of zero increasing to 24,000fpm
(270mph+)
in five seconds and then back to zero in another five seconds. I have
never
heard of anything like it and certainly never experienced anything
similiar.

I have experienced vertical speeds of 5000fpm in mountan waves systems on
the east side of the Sierra near Minden, but those were with 100kt+ winds
at
ridge level (trees knocked down, semis turned over, planes beaking tie
down
ropes ect)

Mike
MU-2

"John Harper" wrote in message
news:1075704296.323452@sj-nntpcache-5...
Flying from Palo Alto to Santa Monica yesterday, we hit (I think) a
rotor
coming over the mountains north of LA. We'd had some fairly strong
up and downdrafts, though nothing really unpleasant, when suddenly
we were going DOWN - about 2000' in 10 seconds or so, everything
stuck to the roof for maybe 5-10 seconds. It was an interesting ride...
most things landed shortly afterwards (and I even found a flashlight
that
had disappeared) although my E6B remained lodged somewhere
and fell on my head on final.

Afterwards, my wife asked me how often this happens... once per
flying lifetime, much less, every few years. I couldn't answer... for
sure
the first time in my 600 hours, but that's not much.

So here's my informal sample... how many people here have had a
similar experience? Anyone care to guess how unlikely this it?

(And to forestall, or try to, the people who tell me I should know
something
about mountain flying, yes I HAVE read Sparky Iverson's book, and
anyway living in the Bay Area it's hard to go anywhere much without
overflying mountains. I was over 2000' above terrain too, 9500'
over a ridgeline at about 6000').

John

But for sure
I lost 2000' (I couldn't believe it when I looked at the altimeter after
recovering the plane...

[...]

I don't know whether this was "severe turbulence" according to
the definition. [...] I did keep the plane under
control - my main concern being to avoid hitting Vne.


Unless you intended to lose 2000 feet, I'd say the plane was not under control.
The wings may have been level, but two thousand uncommanded feet of altitude
loss qualifies to me as severe turbulence. And whether it was smooth or not is
irrelevant - bumpy air is "chop", altitude deviations are "turbulence". Sort
of.

Jose

--
(for Email, make the obvious changes in my address)

Well, I was about to start descending, and it was quite handy to lose
2000', but I certainly wasn't planning to lose it THAT quickly!
In any case I reported it as severe turbulence at the time.

I forgot to mention that I had a 25kt tailwind - nothing remarkable -
at 9500'. It sped up to 40kt or so over the ridge, I was briefly
showing ground speed over 200kt.

John

"Teacherjh" wrote in message
...

But for sure
I lost 2000' (I couldn't believe it when I looked at the altimeter after
recovering the plane...

[...]

I don't know whether this was "severe turbulence" according to
the definition. [...] I did keep the plane under
control - my main concern being to avoid hitting Vne.


Unless you intended to lose 2000 feet, I'd say the plane was not under
control.
The wings may have been level, but two thousand uncommanded feet of
altitude
loss qualifies to me as severe turbulence. And whether it was smooth or
not is
irrelevant - bumpy air is "chop", altitude deviations are "turbulence".
Sort
of.

Jose

--
(for Email, make the obvious changes in my address)

Smooth air does not consitute turbulence, nor does an altitude
excursion in smooth air. Mountain wave often causes uncommanded
altitude excursions of substantial magnitude but the air is absolutely
smooth. That is not turbulence. The airplane is under control, it is
just in an air mass that is rising or descending faster than the
airplane has the performance to overcome.

In general turbulence is defined as the force you feel as you are
thrown against the seat belt. So, it isn't even light until you are
being tossed against the belt. Severe is where control of the
airplane is in doubt and there may well be some question as to whether
the airplane will hold together. It is truly no fun at all when you
get into a condition where you cannot cause the airplane to return to
wings level flight due to the frequency and violence of the
displacements that are occurring. You also may face the risk of being
rendered unconscious due to striking the ceiling of the cabin.

Fortunately, it is rare.

If I recall correctly, a severe turbulence encounter in a transport
category aircraft requires a full airframe inspection. It's a good
idea in an FAR 23/CAR 3 airplane as well as a good friend bent the
wings of his Meridian last summer while avoiding thunderstorms when he
encountered severe turbulence.

All the best,
Rick

(Teacherjh) wrote in message ...

But for sure
I lost 2000' (I couldn't believe it when I looked at the altimeter after
recovering the plane...

[...]

I don't know whether this was "severe turbulence" according to
the definition. [...] I did keep the plane under
control - my main concern being to avoid hitting Vne.


Unless you intended to lose 2000 feet, I'd say the plane was not under control.
The wings may have been level, but two thousand uncommanded feet of altitude
loss qualifies to me as severe turbulence. And whether it was smooth or not is
irrelevant - bumpy air is "chop", altitude deviations are "turbulence". Sort
of.

Jose