AVSIG: New (to me) Wake Issue wwswsigarch.jpg (7236 bytes)

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Scott Dyer [HPN/NY]
Top Gun


Reged: 01/11/03
Posts: 20065
New (to me) Wake Issue
      #386069 - 02/09/14 09:30 AM

I had some time yesterday afternoon to extract the 210 from the ice, pry the wing covers off and do a quick 17 min. night currency run.

On the last landing, an E190 was ahead of me for the runway, I turned a 1/2 mile base from downwind when he was abeam. I stayed high, intending to land beyond the jet's touchdown point (which was about 1,000-1,200' feet from the threshold). The jet turned off prior to reaching the end (C/D for those familiar with HPN) so it couldn't have landed long.

I crossed the threshold at about 150-200' AGL, slowed nicely, looking to touch about 2,000' ahead. At the threshold, I got a strong rolling moment to the right, correctable with a good dose of rudder and some aileron, and nose-down input to keep flying speed. It lasted about 5 seconds, I guess. From then on down to the runway, all was normal.

Winds were light, 270/3 for runway 34, not a burble in the pattern, and the arrival prior to the E190 was a CRJ 5 mins before I was over the threshold. Not sure where the CRJ landed but I doubt it was as high as I was over the threshold.

I'd thought I had the wake thing knocked. But I didn't and that was surprising. Wakes are usually described as either hugging the ground with a light crosswind, or descending. This one climbed?


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James Peters (BAK)
AVSIG Member


Reged: 04/28/04
Posts: 1108
Loc: Indiana USA
Re: New (to me) Wake Issue [Re: Scott Dyer [HPN/NY]]
      #386082 - 02/09/14 12:57 PM

Scott, while I was still living in Scottsdale, AZ, I attended a refresher course prior to refreshing my single engine land pilot's license...and a film was shown that dealt with Wake Turbulence...the film stated that wake turbulence persisted for at least 15 minutes.. sometimes longer.

Later while on a commercial flight, I have experienced a bump in clear air at altitude.. and I attributed it to a previous aircraft ahead.

The film showed a DC-10 landing with smoke generators showing the wake turbulence. Very interesting and informative.

The film stated that the roll recovery of a DC-9 was 13 degrees/second while a 747 generated a roll of some 45 degrees/second...that is one reason for a 5 mile separation on landing, for a DC-9 if landing behind a 747.

Jim

Edited by James Peters (BAK) (02/09/14 01:02 PM)


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Ralph Jones
Top Gun


Reged: 08/31/01
Posts: 21214
Loc: 4CO2
Re: New (to me) Wake Issue [Re: Scott Dyer [HPN/NY]]
      #386089 - 02/09/14 02:57 PM

What was the sky cover like? If it was a day with snow on the ground, the sun out and the runway clear, I'd think about thermal lift coming off the runway.

--------------------
Ralph Jones
LS-4a N49LS 6R


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Scott Dyer [HPN/NY]
Top Gun


Reged: 01/11/03
Posts: 20065
Re: New (to me) Wake Issue [Re: Ralph Jones]
      #386092 - 02/09/14 04:19 PM

Ralph - CAFB, night. Essentially calm.

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B. Butler (Oregonian)
Top Gun


Reged: 05/15/04
Posts: 9760
Loc: Ashland, Oregon
Re: New (to me) Wake Issue [Re: Ralph Jones]
      #386093 - 02/09/14 04:22 PM

Quote:

I'd think about thermal lift coming off the runway.




Spoken like a glider pilot. <g>

--------------------
"Why not be a nihilist? A man has to believe in something."
-Bernie Gunther


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Russell Holton
AVSIG Member


Reged: 07/07/05
Posts: 14136
Re: New (to me) Wake Issue [Re: B. Butler (Oregonian)]
      #386110 - 02/09/14 08:10 PM

Question: What causes the wake to drift downward?

I tried googling for a answer, but didn't find one. I did find this from avweb: "The air curling up around the wing tip forms a horizontal tornado that trails behind the airplane and tends to sink somewhat below the producing aircraft's flight path -- if that aircraft is in level flight. The vortices produced during a descent are somewhat less predictable."


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Ralph Jones
Top Gun


Reged: 08/31/01
Posts: 21214
Loc: 4CO2
Re: New (to me) Wake Issue [Re: Russell Holton]
      #386113 - 02/09/14 08:21 PM Attachment (111 downloads)

Quote:

What causes the wake to drift downward?



Newton. A wing generates lift by imparting downward momentum to the air, so the "inside" part of the vortices is moving downward faster than the "outside" part is moving up, and the core moves down at the average velocity.



--------------------
Ralph Jones
LS-4a N49LS 6R


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Randy Sohn
Gradn Exlated Ordre of teh Fyling Fingres


Reged: 08/31/01
Posts: 23187
Loc: Savage, MN - U.S.A.
Re: New (to me) Wake Issue [Re: Russell Holton]
      #386114 - 02/09/14 08:26 PM

Quote:

curling up around the wing tip forms a horizontal tornado that trails behind the airplane




Yup, interesting stuff, I used to watch Frank Sanders in his SeaFury put on a show with the smoke generators on each tip at OSH. Remember standing there one day watching and noticed the crowd around us looking AT the airplane as Frank flew past, I told them "Don't look at the Sea Fury, watch way behind the plane cuz that's where the show is!" Wish we could'a gotten a copy of a video there to show in recurrent training on the airline.

best, randy


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Randy Sohn
Gradn Exlated Ordre of teh Fyling Fingres


Reged: 08/31/01
Posts: 23187
Loc: Savage, MN - U.S.A.
Re: New (to me) Wake Issue [Re: Scott Dyer [HPN/NY]]
      #386117 - 02/09/14 08:57 PM

Quote:

or descending. This one climbed?




Scott, color me really puzzled over this one! Unmentioned in the analysis is any mention (that I can see) of the traffic preceding that E190? Wondering if anyone there who could've affected you with his wake? I spent a whole career making sure I landed just PAST the "touchdown point" of the preceding traffic and never had it not work. This is one of the situations that I'd previously discussed/described here on Avsig when Chris Manno had talked about having a definite touchdown target in the runway's beginning I do the same except I am a little different in that I "name my poison" as regards the touchdown target being at a certain marker on the runway's side which again is just past the point at which the preceding traffic touches down, puts his nosewheel on the ground and ceases generating lift.

best, randy


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Scott Perdue (50F)
Top Gun


Reged: 05/01/04
Posts: 1126
Loc: Texas
Re: New (to me) Wake Issue [Re: Scott Dyer [HPN/NY]]
      #386121 - 02/09/14 09:10 PM

Scott-

Winds like that are enough to stall one of the vortices from clearing the runway.... it can easily remain there for 5 min or more.

gunny

--------------------
Gunny
www.eagleflyingmuseum.org


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