Spitz1 Newcomer

Couldnt find the answer for this big debate which is going on between a few of us....
Scenerio:
A twin cessna is getting ready to depart from an intersecting runway. On short final is a B737. The twin gets put into position and hold and the B737 touches MAIN gears down right before the intersection portion of the runway and crosses the the remainder of the intersection portion nose gear up. Is the cessna able to depart right away once the B737 crosses?
The debate on this is that some say that wake turbulence ends once an aircraft touches down (.65), however, others argue that wake turbulence is still being generated until ALL landing gears touch down. Ive tried to research this online, but have come up empty handed. Could anyone help me out with this question? If you find the answer online, please include the link with the answer. Thanks,

Max561 Rookie Tampa

The majority of the wake would end as soon as the main gear hits the ground. The aircraft will still create some wake until shortly after the front gear is on the ground. The small about of wake created after the main gear is on the ground is not relevant as it would be far less than the turbulent air that a 140,000 lb 737 rolling down the runway shortly after landing would create.

It’s been almost 3yrs since I worked intersecting runways operations but if I remember right, wake turbulence is not relevant in this situation. If you have a twin cessna in position and a 737 lands on the intersecting runway and crosses the intersection the cessna can begin departure roll. Again it’s been a while since I had this situation.


7110.65 3-9-8
b. Separate departing aircraft from an aircraft
using an intersecting runway, or nonintersecting
runways when the flight paths intersect, by ensuring
that the departure does not begin takeoff roll until one
of the following exists:
2. A preceding arriving aircraft is clear of the
landing runway, completed the landing roll and will
hold short of the intersection, passed the intersection,
or has crossed over the departure runway.

atcguruaf Rico Suave AZ

wake turbulence ends as soon as the aircraft touches down. I'm sure there may be some "residual" turbulence, but not enough to cause any worries.

AIM, 7-3-4, FIG 7-3-3

http://www.faa.gov/air_traffic/publi...7/aim0703.html

Wponcho Junior Member Orlando

Your answer needs to be a sticky! I can't count how many times I've seen people post a wake turbulence question that is answered by your response.

atcguruaf Rico Suave AZ

hahahaha..

djmodifyd Senior Member

there is only wake turbulence for crossing flight paths when a heavy/757 is involved also

FM_Weasel Senior Member

Agreed. The OP's scenario has no wake turbulence application in the first place. Intersecting runway WT separation is only for Heavy/B757.

The rules for intersection departures are Same Runway, same OR opposite direction. Doesn't say anything about intersecting runways.

Intersection departure != Intersecting RUNWAY departure. Two different things.

atcguruaf Rico Suave AZ

please read the .65. It does talk about WT for intersecting runways.

whegner Junior Member

As has been stated, the WT effectively ends when the main gear touches but there is still residual wake until all the gear is down. Remember wake rotates away and behind the a/c (Think of a boat wake in the water) so by the book you can run the Twin Cessna with no problem but it's not a bad idea to issue a cautionary advisory with the clearance since there is a chance he will roll or rotate through some of the residual wake.

It's not a catch all and it doesn't shield you from utilizing the hard and fast WT separation rules, but you can never really go wrong issuing a wake turbulence advisory if in your judgement there may be an impact on another a/c. Heck, I've even issued it to small fixed wing a/c interacting with large helo's (i.e. H-53). Began doing that after I saw a C-172 get lifted off the ground while holding short as an H-53 was landing on the numbers of a runway.

atcguruaf Rico Suave AZ

Absolutely! What's wrong with being safe? Afterall, it's not like we're in a profession where safety is paramount. I agree with you whole-heartedly. If in doubt, it's better to be safe than sorry. We all know what can happen when you gamble.

It's kind of weird because, for example, had the controller at Lexington (for example only) scanned or kept his eye on the plane, we'd have never heard about anything. As a matter of fact, he wouldn't have so much as a story to tell.

It's the little things we do every day that actually matter. Scanning, cautionaries, waiting for 1 more arrival before departing the next aircraft, asking for ANOTHER readback of hold short instructions (even though you know the pilot will probably hold short), etc. We don't think about these things we do. But that one time you miss it, or don't caution on the side of safety, can turn into a grave situation. Then you're stuck with the rest of your life wondering "why didn't I just have the pilot readback the runway again?" or "why didn't I just issue a cautionary?" or "why didn't I have him maintain visual separation?"

It seems like the up and coming air traffic force is heavily reliant on technology to do their jobs (i.e. safety logic), not to mention I've seen a lot of disservice because the controller was too lazy to do anything, perhaps not realizing that it's our job to serve the pilot and expedite the flow. Rather than trying to provide a service, it's like "screw him, he should've known to slow down/exit sooner" etc.

Sorry for the rant, but I think the system is getting worse, not better, especially now when you have the blind leading the blind. No, I'm not an old folk, I was just taught by old folks. (Bare in mind that this is not all-inclusive of all new controllers)