Weird Windshear

[Bravo8500]

I thought this was interesting so I'll share it. I hit some unusual
windshear I suppose last night going into St. Simmon's Island, GA
(BQK) in an A36 Bonanza. Here we were, me flying and the non-pilot
owner (my brother-in-law) in the right seat cruising at 3000 over the
top of a broken layer about 25 south of the localizer to runway 7,
about 9:30 EST. We were in moderate to occasionally severe turbulance
and I had been warned by the FSS briefer about a windshear at 1000 agl
- I think it was the fact that there was a 180 degree diff in wind
direction between the surface and 1000 agl that was causing it. Oh
yeah, a big fat low pressure was sitting right on top of BQK, more or
less, as I could determine from the duats graphical current analysis in
the motel room an hour later. The pressure had been dropping since
Atlanta and the altimeter was down to 29.68 I believe. Anyway, here we
are in flat out cruise, I look up and notice I'm only indicating 140
or so when I should see 165, and dropping a couple of knots per second.
As the airspeed goes through 110, I bring in full RPM and manifold and
we continue to lose airspeed down to 80 knots. I'm wondering what the
heck is going on, we're now in a climb attitude and get one blip of
the stall warning. By this time I've disengaged the ap and now am
allowing the airplane to drop to maintain around 80. I'm just about
to call ATC when we start picking up airspeed, slowly. Man, that was
weird.

[Marco Leon]

Were there any mountains or hills around? It could have been a mountain
wave. I had experienced the same exact thing in upstate NY/Massachusettes
border heading northbound with a wind coming from the northwest. Did you
start picking up speed afterward? After I had experienced the downdraft
where I had full power in to maintain 80kts and my altitude, I then needed
to keep a descending profile to again maintain the altitude with a
corresponding 135kt IAS.

Everyone I talked to that had experienced this said it was very weird the
first time they encountered it.

Marco Leon

"Bravo8500" > wrote in message
oups.com...
>I thought this was interesting so I'll share it. I hit some unusual
> windshear I suppose last night going into St. Simmon's Island, GA
> (BQK) in an A36 Bonanza. Here we were, me flying and the non-pilot
> owner (my brother-in-law) in the right seat cruising at 3000 over the
> top of a broken layer about 25 south of the localizer to runway 7,
> about 9:30 EST. We were in moderate to occasionally severe turbulance
> and I had been warned by the FSS briefer about a windshear at 1000 agl
> - I think it was the fact that there was a 180 degree diff in wind
> direction between the surface and 1000 agl that was causing it. Oh
> yeah, a big fat low pressure was sitting right on top of BQK, more or
> less, as I could determine from the duats graphical current analysis in
> the motel room an hour later. The pressure had been dropping since
> Atlanta and the altimeter was down to 29.68 I believe. Anyway, here we
> are in flat out cruise, I look up and notice I'm only indicating 140
> or so when I should see 165, and dropping a couple of knots per second.
> As the airspeed goes through 110, I bring in full RPM and manifold and
> we continue to lose airspeed down to 80 knots. I'm wondering what the
> heck is going on, we're now in a climb attitude and get one blip of
> the stall warning. By this time I've disengaged the ap and now am
> allowing the airplane to drop to maintain around 80. I'm just about
> to call ATC when we start picking up airspeed, slowly. Man, that was
> weird.
>



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[W P Dixon]

"Marco Leon" <mleon(at)optonline.net> wrote in message
...
> Were there any mountains or hills around? It could have been a mountain
> wave.

I don't think he had problems with mountains or hills at St Simons
Island,...it's a island off the coast of Georgia. A tool bridge away from
Brunswick , GA . Really flat land. Maybe winds coming ashore?

Patrick

[W P Dixon]

That's a toll bridge..sorry for the typo!

"W P Dixon" > wrote in message
...
>
> "Marco Leon" <mleon(at)optonline.net> wrote in message
> ...
>> Were there any mountains or hills around? It could have been a mountain
>> wave.
>
> I don't think he had problems with mountains or hills at St Simons
> Island,...it's a island off the coast of Georgia. A tool bridge away from
> Brunswick , GA . Really flat land. Maybe winds coming ashore?
>
> Patrick

[Bravo8500]

Oops, I said 25 south, I ment 25 north. It was flat as a cracker. I
didn't have the increase like you were saying ... I've felt smaller
up/down drafts going in and out of cumulous before, but this occurred
over a lenghty perdiod of time relatively, like 30 seconds or so. We
had had a strong head wind all the way down, but when we were doing 80
indicated, I now remember seeing 97 on the GPS. I was on the localizer
a few minutes later and so I didn't get a chance to see how strong the
tail wind was. After we landed, driving to the motel, we noticed the
smoke from a paper mill descending after it left the stack. I wondered
if that was somehow related ... descending air? Low pressure, hmm.

[W P Dixon]

"Bravo8500" > wrote in message
oups.com...
After we landed, driving to the motel, we noticed the
> smoke from a paper mill descending after it left the stack. I wondered
> if that was somehow related ... descending air? Low pressure, hmm.
>
Oh man the dreaded stinking papermill! I do mean stink too! There's one in
Jesup , GA that will just turn your stomach within 30 miles of it! The one
there in Brunswick never bothered me much, I guess I got lucky and coastal
winds blew the funk the other way! ;) Brings back memories,..ah to be home
on the banks of the Ogeechee in good old Georgia.

Patrick

[Morgans]

"W P Dixon" > wrote

> Oh man the dreaded stinking papermill! I do mean stink too! There's one in
> Jesup , GA that will just turn your stomach within 30 miles of it!

The locals say that that is the "smell of money." It is fermentation,
breaking down the pulp.

This windshear was all related to the passage of the developing storm, a
Nor'easter, now headed up the east coast. Lots of complex things going on.
A cold front was in the area, so you have warm air from the south rising
over it, air from the north blowing and being trapped under the rising warm
air, and changing directions along the frontal boundary. Now add to that a
developing low pressure system, and a good bit of convection activity, and
you have a ......well, a mess! ;-o

That there is some 'o those tecqicquanal wather terminiiligy!

I'm about half surprised there was not some of that solid h2o mixed in there
somewhere, too.
--
Jim in NC

[Bravo8500]

>Lots of complex things going on.<

I think you're exactly right. That sounds right on with the warm air
from the south and the cold from the north underneathe. I thought it
was interesting how the briefer got it right on too with his warning. I
heard one controller tell someone up high that there was strange
jetstream pattern or something. They were all getting beat up. There
was a tornado reported a couple of hours before we arrived. The forty
mile an hour winds and rain had moved offshore about that time, a
couple of hours before. This gives me new respect for
windshear/downdrafts. My bro-in-law told me he has heard of trees being
flattened by downdrafts. If they can flatten a tree, they can take an
airplane and plant it, no doubt. I went down the ILS into Huntsville
one night when they were giving Low Level windshear alerts .. next time
that happens I'll have them vector me around some before attempting it,
having experienced it.

[Nathan Young]

On 28 Feb 2005 18:19:31 -0800, "Bravo8500" >
wrote:

>I thought this was interesting so I'll share it. I hit some unusual
>windshear <snip>

> By this time I've disengaged the ap and now am
>allowing the airplane to drop to maintain around 80. I'm just about
>to call ATC when we start picking up airspeed, slowly. Man, that was
>weird.

Why were you going to call ATC? Declare an emergency?

[Montblack]

("Bravo8500" wrote)
> heard one controller tell someone up high that there was strange
> jetstream pattern or something. They were all getting beat up.


http://www.weatherimages.org/data/imag192.html


Montblack

[Bravo8500]

For one, I was going to tell them I wasn't able to hold altitude, I was
already 200 below assigned. Also, I was thinking about turning around,
changing directions or something, I was kind of at a loss for what to
do next.

[Morgans]

"Nathan Young" > wrote

> Why were you going to call ATC? Declare an emergency?

Naah. With stuff like that goin' on, I'd tell him I was gonna go ahead and
crash, and quit fightin' it! ;-)
--
Jim in NC

[Roger]

On 28 Feb 2005 18:19:31 -0800, "Bravo8500" >
wrote:

This is just the way wind shear works. Yes, it's an extreme example,
but I've stalled in level flight at Va on a beautiful clear day.

The first clue to extreme shear conditions is the large change in
direction in a relatively small change in altitude. If you cruise at
165 into a 40 knot head wind and abruptly enter a 40 knot tail wind
you are going to lose 80 knots. If you have the altitude it will
eventually end up at the original cruise. OTOH if you went from a 40
knot tail wind to a 40 knot head wind abruptly, can you imagine what
that would do to the plane. You not only would have some extreme
turbulence, but would temporarily hit close to 240 knots which is well
above Vne.

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com

>I thought this was interesting so I'll share it. I hit some unusual
>windshear I suppose last night going into St. Simmon's Island, GA
>(BQK) in an A36 Bonanza. Here we were, me flying and the non-pilot
>owner (my brother-in-law) in the right seat cruising at 3000 over the
>top of a broken layer about 25 south of the localizer to runway 7,
>about 9:30 EST. We were in moderate to occasionally severe turbulance
>and I had been warned by the FSS briefer about a windshear at 1000 agl
>- I think it was the fact that there was a 180 degree diff in wind
>direction between the surface and 1000 agl that was causing it. Oh
>yeah, a big fat low pressure was sitting right on top of BQK, more or
>less, as I could determine from the duats graphical current analysis in
>the motel room an hour later. The pressure had been dropping since
>Atlanta and the altimeter was down to 29.68 I believe. Anyway, here we
>are in flat out cruise, I look up and notice I'm only indicating 140
>or so when I should see 165, and dropping a couple of knots per second.
>As the airspeed goes through 110, I bring in full RPM and manifold and
>we continue to lose airspeed down to 80 knots. I'm wondering what the
>heck is going on, we're now in a climb attitude and get one blip of
>the stall warning. By this time I've disengaged the ap and now am
>allowing the airplane to drop to maintain around 80. I'm just about
>to call ATC when we start picking up airspeed, slowly. Man, that was
>weird.

[Casey Wilson]

"Roger" > wrote in message
...
> On 28 Feb 2005 18:19:31 -0800, "Bravo8500" >
> wrote:
>
> This is just the way wind shear works. Yes, it's an extreme example,
> but I've stalled in level flight at Va on a beautiful clear day.
>
> The first clue to extreme shear conditions is the large change in
> direction in a relatively small change in altitude. If you cruise at
> 165 into a 40 knot head wind and abruptly enter a 40 knot tail wind
> you are going to lose 80 knots. If you have the altitude it will
> eventually end up at the original cruise. OTOH if you went from a 40
> knot tail wind to a 40 knot head wind abruptly, can you imagine what
> that would do to the plane. You not only would have some extreme
> turbulence, but would temporarily hit close to 240 knots which is well
> above Vne.
>
> Roger Halstead (K8RI & ARRL life member)
> (N833R, S# CD-2 Worlds oldest Debonair)
> www.rogerhalstead.com

Roger, your experience and mine are pretty much the same, but reversed.
I dropped through the turbulence of the shear from a 40+ tailwind into calm
air in just a matter of a few seconds. The result was an almost instant
increase in airspeed. The increased lift jammed me back up through the
shear -- It was almost like I had bounced off of something. The plane didn't
stall when it went back to the upper level, but thinking back it could have,
if I'd've lost enough forward speed. In any case it was a hell of a ride
for a bit.
I still had to go through the shear to get down to pattern altitude. On
the next trip down, I throttled back to just above stall. When I went
through the shear, I shoved the nose down and cut the throttle all the way
back -- then recovered into normal flight when things settled down.
What I should have paid more attention to was when my whiz-wheel told me
I had a ground speed of 155 knots. In a C-150. I dismissed it at the time as
manipulating the dials wrong.
I wasn't going to quarrel with the original poster over his assessment
of his conditions, but his was more like flying into a severe sink than into
a shear. Especially with his description of the airspeed bleeding off over
minutes while the autopilot tried to compensate. He did a good job of coping
with it in any case. I'm just picking on calling it a shear.

Casey Wilson
Freelance Writer and Photographer

[Bravo8500]

Felt like a sink, but I've never heard that term, only windshear.

[Casey Wilson]

"Bravo8500" > wrote in message
oups.com...
> Felt like a sink, but I've never heard that term, only windshear.
>
We use it mostly in gliders -- sometimes referred to as a downdraft
by power pilots. Glider guiders call updrafts "lift." Typically measured on
a vario(meter) in fps or knots. The only difference between a vario and an
VSI is the vario usually beeps. The pitch and period of the beeps sort of
indicate the velocity. Lift and sink work together -- somewhere in the
vicinity there was a rising volume of air. You were unlucky enough to fly
into the negative half.
Sorry if that seems patronizing or pedantic.
That brings up an autopilot question you might answer for me. If you
had not disconnected the autopilot, could it have taken you into a stall?

[Bravo8500]

Downdraft, shear, microburst - bad! The ap I use (kfc200) only knows to
hold altitude, it doesn't care about airspeed, so it will gladly stall
it for you.

[Bravo8500]

I say that, but in reality it may just apply so much back pressure, or
trim, and then it would simply fail to hold altitude. I've never tested
it.

[Roger]

On Fri, 04 Mar 2005 01:53:44 GMT, "Casey Wilson" <N2310D @ gmail.com>
wrote:

>
>"Bravo8500" > wrote in message
oups.com...
>> Felt like a sink, but I've never heard that term, only windshear.
>>
> We use it mostly in gliders -- sometimes referred to as a downdraft
>by power pilots. Glider guiders call updrafts "lift." Typically measured on
>a vario(meter) in fps or knots. The only difference between a vario and an
>VSI is the vario usually beeps. The pitch and period of the beeps sort of
>indicate the velocity. Lift and sink work together -- somewhere in the
>vicinity there was a rising volume of air. You were unlucky enough to fly
>into the negative half.
> Sorry if that seems patronizing or pedantic.
> That brings up an autopilot question you might answer for me. If you
>had not disconnected the autopilot, could it have taken you into a stall?

That depends on the AP, but mine (IF set to altitude hold) will just
keep pulling the nose up until it quits flying. That means you need
to know your power settings when doing a step down approach,.Altitude
hold off, power back (by the numbers), gear down (depends), flaps
(maybe), lead the altitude with power, with the power back to the
proper setting for the approach, turn the altutude hold back on.

BTW, the FAA defines wind shear as *any* abrupt change in wind
direction or speed. That includes up and down.

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com
>

[Dave Butler]

W P Dixon wrote:
>
> "Marco Leon" <mleon(at)optonline.net> wrote in message
> ...
>
>> Were there any mountains or hills around? It could have been a
>> mountain wave.
>
>
> I don't think he had problems with mountains or hills at St Simons
> Island,...it's a island off the coast of Georgia. A tool bridge away
> from Brunswick , GA . Really flat land. Maybe winds coming ashore?

Here in NC you can get mountain waves a few hundred miles downwind from the
Appalachians, though I've never experienced anything as severe as the OP
describes. I think St Simons is too far south for Appalachian mountain waves,
though.

[jsmith]

I cannot personally speak for the "a few hundred miles", but I have
experienced mountain wave within ten nm of the lee side of the
Appalachians in both North Carolina and Georgia.

Dave Butler wrote:
> Here in NC you can get mountain waves a few hundred miles downwind from
> the Appalachians, though I've never experienced anything as severe as
> the OP describes. I think St Simons is too far south for Appalachian
> mountain waves, though.

[Roger]

On Fri, 04 Mar 2005 22:16:49 GMT, jsmith > wrote:

>I cannot personally speak for the "a few hundred miles", but I have
>experienced mountain wave within ten nm of the lee side of the
>Appalachians in both North Carolina and Georgia.
>
>Dave Butler wrote:
>> Here in NC you can get mountain waves a few hundred miles downwind from
>> the Appalachians, though I've never experienced anything as severe as
>> the OP describes. I think St Simons is too far south for Appalachian
>> mountain waves, though.

Some where around here I have some photos of lenticular clouds over
the Michigan, Ohio border taken from the company King Air.

The Pilot and copilot were remarking that was something you just don't
see around here, but there they were.

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com

[Dave Butler]

jsmith wrote:
> I cannot personally speak for the "a few hundred miles", but I have
> experienced mountain wave within ten nm of the lee side of the
> Appalachians in both North Carolina and Georgia.

Maybe I shouldn't say "mountain wave". There is a definite vertical component to
the air movement where I live, about 200-300 miles east of the Appalachians in
NC, when the wind blows perpendicular to the ridges. If you're flying east-west,
you are alternately pulling and pushing to maintain altitude as you pass from
crest to trough of the waves. I'm *guessing* the time from push to pull is a
minute or so, so that would make the wavelength about 5 nm at Mooney speeds.

[Before someone else says it, yes, I know, efficiency can be improved by
allowing altitude to vary and just staying trimmed for your airspeed.]

Dave

>
> Dave Butler wrote:
>
>> Here in NC you can get mountain waves a few hundred miles downwind
>> from the Appalachians, though I've never experienced anything as
>> severe as the OP describes. I think St Simons is too far south for
>> Appalachian mountain waves, though.