Wake turbulence drift

sweeps

Undercarriage Actuator
Anyone have any info on the rate at which wake turbulence will drift on the ground? I found this http://www.faa.gov/training_testing/training/media/wake/04SEC2.PDF that has some info on the drift at altitude. I ask because I'm flying out of KSNA and the runway used by the singles is only about 500 feet from the main runway(centerline to centerline). Prevailing winds are always blowing from the large runway to the small, and we have to offset our final approach and upwind legs 15 degrees away from the main one for separation. I'm trying to ballpark how long it would take for the landing airliners wake to reach the parallel runway, especially when they touchdown halfway down the length of the short runway. Any input or direction to other sources would be awesome. Thanks.
 
2-3 knots lateral drift


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I haven't personally flown there, but I would think it best to just apply normal wake turbulence separation (light following large or light following heavy) since the runways are so close. Wake turbulence can ruin your day.
 
2-3 knots lateral drift


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Thanks. Where did you find that? Any idea of how long it takes to dissipate? Correct me if I'm wrong but any crosswind component will help break up the downwind side turbulence right?
 
I haven't personally flown there, but I would think it best to just apply normal wake turbulence separation (light following large or light following heavy) since the runways are so close. Wake turbulence can ruin your day.

Yeah the problem is when you have a bunch of planes in the pattern or when the airline will touch down halfway or more down your runway, you end up going around more times than you can get landings in it seems like.
 
Thanks. Where did you find that? Any idea of how long it takes to dissipate? Correct me if I'm wrong but any crosswind component will help break up the downwind side turbulence right?

Usually ATC mandates 3 minutes for wake avoidance. I'd imagine that time is based on the absolute worst case scenario.

Wakes begin to weaken as soon as they are created. They will remain active for a while but the threat they pose diminishes proportionally with their duration. I don't know for sure if the downwind wake is hindered but it is pushed away faster due to its general movement away from the runway at the 2-3 knots.




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Usually ATC mandates 3 minutes for wake avoidance. I'd imagine that time is based on the absolute worst case scenario.

Wakes begin to weaken as soon as they are created. They will remain active for a while but the threat they pose diminishes proportionally with their duration. I don't know for sure if the downwind wake is hindered but it is pushed away faster due to its general movement away from the runway at the 2-3 knots.




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Cool thanks for the help.
 
The wake is part of the air mass and moves at the speed of the crosswind component. If there is no crosswind, it is going to have a slight lateral drift. On days with heavy crosswinds, you need to adjust accordingly. Do some homework. There is tons of training on this subject on different websites about this phenomena. Sounds like you are thinking along the right lines, but you can easily get yourself into a heap of trouble if you get caught in wake turbs, especially in a light aircraft. I have been twisted up pretty good in a 707 following a C-5 on departure and have personally witnessed a Cherokee go over 60 degrees AOB about 100 feet in the air. Not good. The smart thing to do is either wait the allotted time (3 minutes following a heavy) or just go somewhere else. It isn't worth bending a plane or hurting someone.
 
Beware Chinooks hovering! One of my cousins was doin a friends' BfR in his Grumman Tiger with a Chinook hovering good distance away from his runway when his left wing dropped. Dirty diaper as he took controls and recoved- still damaged left wing when struck Runway.
 
Beware Chinooks hovering! One of my cousins was doin a friends' BfR in his Grumman Tiger with a Chinook hovering good distance away from his runway when his left wing dropped. Dirty diaper as he took controls and recoved- still damaged left wing when struck Runway.

I used to ride in chinooks in the army and man those things have some rotor wash :) hooking up a sling load while they were hovering a few feet over your head was always fun.
 
I used to ride in chinooks I'm the army and man those things have some rotor wash :) hooking up a sling load while they were hovering a few feet over your head was always fun.

My Cuz was a Huey pilot in Nam and was familiar with Chinooks- he just couldn't believe how far it travelled and how severe the wash was.
 
Helicopters are no joke. I was once on a ladder fueling a Champ and some genius in a little chopper decided to hover-taxi to the self-serve on the other side of my pump. I was hanging onto that airplane for dear life. But then I got to watch the resident old crotchety airport guy go tear them a new one. Good times.
 
In the south jax practice area (just south of CRG and north of SGJ) we always contend with P-3s, P-8s, and sometimes C-130s flying through from offshore at anywhere from 1500 to 3500 ft. I once got in some nasty wake turbulence from a P-3 that nearly left me upside down. He was already a couple miles away and I was about 500 ft be beneath his flight path so I didn't think much of it... Boy was that a surprise.
 
Sterling at KCRG... Only part time now though. Built up about 500 dual given in the past 8 months and I just landed another job.
 
In the south jax practice area (just south of CRG and north of SGJ) we always contend with P-3s, P-8s, and sometimes C-130s flying through from offshore at anywhere from 1500 to 3500 ft. I once got in some nasty wake turbulence from a P-3 that nearly left me upside down. He was already a couple miles away and I was about 500 ft be beneath his flight path so I didn't think much of it... Boy was that a surprise.

We have to contend with that and the occasional E-3 Sentry or E6B coming to hog the pattern at our airport too. Sometimes I end up just telling tower I want to leave to head to a less busy nontowered airport. As a side note, that's why it's a good reason to check weather and NOTAMS/TFRs for other airports before hand so you have options. It's annoying having to extend downwind... extend upwind.... do a left/right 360. "Caution wake turbulence" etc. etc. Sometimes the military will be there for 2-3 hours doing instrument approaches then pattern work.
 
Yea... The USN heavies love using KVQQ (Cecil Field) for pattern work and practice approaches around here so we pretty much avoid the area unless we have to. Although it is cool to go over there and be in the pattern with a Superhornet, P-8, and one of the new Ospreys all at the same time.
 
As one of those Navy heavies, I can tell you that we are restricted by a lot of things in choosing airports to do pilot training at. Distance, runway length, bearing strength, traffic density, etc all come to mind. If you are taking your light single or twin to do pattern work at an airfield with an 11,000 ft runway, you are running the risk of having to deal with us being there. By the same token, if I take the E-6 to do low approaches at a 6,000ft field, I expect lots of light civil traffic.
Here in OKC, Tinker tower is horrible at handling multiple aircraft in the pattern (extend downwind to follow heavy E-3 on 14 mile final). It is much easier for us and the E-3s to to over to Rogers if there are more than 2 airplanes working Tinker. They have 2 well separated parrallel runways and the guys in the tower there are absolute pros.
There is no lack of airports here, and if you are in a light airplane, just go over to Wiley Post or OU.
We may have 4 or 5 pilots on board who need currency or other training. That is why we stay so long.
 
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