Wake Turbulence Question

I was level at 1500' MSL and ATC announced a Gulfstream bizjet crossing from my
right to left, 3000' MSL less than a mile lateral distance. I had my
instrument student do a 360 for wake turbulence separation and dissipation.
ATC questioned my actions and told me the 360 wasn't necessary.

BTW: I was in Class Echo airspace in southern Maine.

I havent been instructing all that long but this did seem to me to be a classic
wake turb encounter in the making. I am interested in hearing from other
pilots and CFII's on this subject. Was I over cautious ? Or prudent.....


Hank

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HankPilot2002 wrote:
I was level at 1500' MSL and ATC announced a Gulfstream bizjet crossing from my
right to left, 3000' MSL less than a mile lateral distance. I had my
instrument student do a 360 for wake turbulence separation and dissipation.
ATC questioned my actions and told me the 360 wasn't necessary.

BTW: I was in Class Echo airspace in southern Maine.

I havent been instructing all that long but this did seem to me to be a classic
wake turb encounter in the making. I am interested in hearing from other
pilots and CFII's on this subject. Was I over cautious ? Or prudent.....


Hank

I'll take a crack at it...

Let's say the Gulfstream was IFR, and was level. Judging by
your level altitude, you were VFR. Either way, you still have the
1000ft vertical separation, regardless of lateral separation, so doing
a 360 wouldn't have mattered for separation. As long as you had him in
sight, and being (assumed) VFR, you could maintain visual separation.
In that instance, the 360 wouldn't have been needed.

Let's now say that the Gulfstream was climbing. He was going to
be crossing your path above you, which may mean that you would catch
the underside of his wake before the tail end of it after his climb. In
that instance, you could have done a 360 to avoid the wake altogether,
then continue. But once again, It wouldn't have been needed, as you had
vertical separation of over 1000ft.

Overcautious? yes. But better to be over than under. You would
have been fine, but as CFII, you would have been in the best position
to make the call. Judging that this post happened after your flight,
you walked away from the flight. Which means you lived. Therefore,
your call was a good one.

BL.
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I was level at 1500' MSL and ATC announced a Gulfstream bizjet crossing from my
right to left, 3000' MSL less than a mile lateral distance. I had my
instrument student do a 360 for wake turbulence separation and dissipation.
ATC questioned my actions and told me the 360 wasn't necessary.

BTW: I was in Class Echo airspace in southern Maine.

I havent been instructing all that long but this did seem to me to be a classic
wake turb encounter in the making. I am interested in hearing from other
pilots and CFII's on this subject. Was I over cautious ? Or prudent.....


The "classic" wake turbulence encounter is flying up the funnel and being
turned over. To do that, your courses would need to be fairly well aligned.
Your encounter sounds like it was more at right angles. You'd get a bump bump
and be through it. By doing a 360, you allowed your course to parallel the
other aircraft's course, and if you didn't know where he was, you risked the
classic encounter as you passed 90 degrees or 270 degrees of your turn.

If it was indeed crossing right to left, I'd have just proceeded on course.

Jose

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

On 13 Jul 2004 00:37:45 GMT, (HankPilot2002) wrote:

I was level at 1500' MSL and ATC announced a Gulfstream bizjet crossing from my
right to left, 3000' MSL less than a mile lateral distance. I had my
instrument student do a 360 for wake turbulence separation and dissipation.
ATC questioned my actions and told me the 360 wasn't necessary.

BTW: I was in Class Echo airspace in southern Maine.

I havent been instructing all that long but this did seem to me to be a classic
wake turb encounter in the making. I am interested in hearing from other
pilots and CFII's on this subject. Was I over cautious ? Or prudent.....


Hank

Maybe because I haven't been bitten, yet, but I would not have been
concerned about a Gulfstream in that circumstance. I would be concerned
about a "heavy" that close, though. Winds may also be a factor.


Ron (EPM) (N5843Q, Mooney M20E) (CP, ASEL, ASES, IA)

I'd have to research the study.. but most wake turbulence only drops about
500ft.. if I remember correctly.. if you were 500ft it would not be an
issue..

also.. wake turbulence is the worst if the heavier aircraft (bizjet) is
configured for landing, flaps and gear etc.. if he was still gear up.. and
in level flight... the bumps would not be so bad even if you had 500ft. It's
the wing tip vortices that are the worst, and yes you may get some vortices
from the flap end at mid span.

We've rendezvoused for refueling, 1000ft below a heavy tanker (KC-10/DC10)
and moved into refueling position and not feel his wake until we are
practically on the boom.. at near cruise speeds

BT


"HankPilot2002" wrote in message
...
I was level at 1500' MSL and ATC announced a Gulfstream bizjet crossing
from my
right to left, 3000' MSL less than a mile lateral distance. I had my
instrument student do a 360 for wake turbulence separation and
dissipation.
ATC questioned my actions and told me the 360 wasn't necessary.

BTW: I was in Class Echo airspace in southern Maine.

I havent been instructing all that long but this did seem to me to be a
classic
wake turb encounter in the making. I am interested in hearing from other
pilots and CFII's on this subject. Was I over cautious ? Or prudent.....


Hank

"BTIZ" wrote in message
news:2fHIc.23345$r3.6120@okepread03...

also.. wake turbulence is the worst if the heavier aircraft (bizjet) is
configured for landing, flaps and gear etc.. if he was still gear up.. and
in level flight... the bumps would not be so bad even if you had 500ft.

A quote from a popular primary text:
"The greatest vortex strength occurs under CLEAN configuration, high weight,
and slow speed." (emphasis mine)

(... and high air density) Their contention appears to be that flaps and
gear help break up the vortex pattern. The clean configuration at slow
speeds results in the highest AOA, supposedly the primary culprit.

Thank you.. roger on the slow and high weight.. which equals high AOA which
create stronger vortices... fist time I've heard about gear and flaps
breaking up vortices..

as I said MY original response.. I'd have to go back and find the article I
read it from

BT

"Icebound" wrote in message
gers.com...

"BTIZ" wrote in message
news:2fHIc.23345$r3.6120@okepread03...

also.. wake turbulence is the worst if the heavier aircraft (bizjet) is
configured for landing, flaps and gear etc.. if he was still gear up..
and
in level flight... the bumps would not be so bad even if you had 500ft.

A quote from a popular primary text:
"The greatest vortex strength occurs under CLEAN configuration, high
weight,
and slow speed." (emphasis mine)

(... and high air density) Their contention appears to be that flaps and
gear help break up the vortex pattern. The clean configuration at slow
speeds results in the highest AOA, supposedly the primary culprit.

"BTIZ" wrote in message
newsK_Ic.259$gQ2.161@okepread03...
...snip...

as I said MY original response.. I'd have to go back and find the article
I
read it from



Since the post, I did a little googling, and found the FAA AIM has basically
the same quote:

http://www.faa.gov/ATpubs/AIM/Chap7/aim0703.html

7-3-3. Vortex Strength

a. ...snip... The greatest vortex strength occurs when the generating
aircraft is HEAVY, CLEAN, and SLOW.

(this time the emphasis is theirs)

"BTIZ" wrote:
also.. wake turbulence is the worst if the heavier aircraft (bizjet) is
configured for landing, flaps and gear etc..

According to the latest edition of the Aeronautical Information Manual
(effective 19 February 2004), paragraph 7-3-3:
"The greatest vortex strength occurs when the generating aircraft is
HEAVY, CLEAN, and SLOW." [emphasis present in original document]

A clean aircraft generates stronger wake vortices than does one
configured for landing.

Ace Pilot wrote:
"BTIZ" wrote:

also.. wake turbulence is the worst if the heavier aircraft (bizjet) is
configured for landing, flaps and gear etc..


According to the latest edition of the Aeronautical Information Manual
(effective 19 February 2004), paragraph 7-3-3:
"The greatest vortex strength occurs when the generating aircraft is
HEAVY, CLEAN, and SLOW." [emphasis present in original document]

A clean aircraft generates stronger wake vortices than does one
configured for landing.

Not necessarily. When it is landing it will be SLOW, which is
much more important than the minimal effect of how it happens
to be configured.
CV