Topic Author
Posts: 1484
Joined: Wed Feb 09, 2005 7:37 am

### 777 Wake Tubulence Question

While returning to IAD on Sunday aboard a UA 777, I was listening to channel 9. There was an RJ second in line to land behind us, and ATC warned them of the wake turbulence from the 777 in front of them.

My question is this:

How long does the wake turbulence last? Must the separation be farther in this scenario?

Russ
My glass is neither 1/2 empty nor 1/2 full, rather, the glass itself is twice as big as it should be.

Starlionblue
Posts: 17965
Joined: Fri Feb 27, 2004 9:54 pm

### RE: 777 Wake Tubulence Question

 Quoting 777DadandJr (Thread starter):While returning to IAD on Sunday aboard a UA 777, I was listening to channel 9. There was an RJ second in line to land behind us, and ATC warned them of the wake turbulence from the 777 in front of them. My question is this: How long does the wake turbulence last? Must the separation be farther in this scenario?

The normal separation is about two minutes. This varies widely depending on the conditions. Wake vortices sink and dissipate slowly.

In this particular case, you have a huge disparity in size between the planes. The effect of wake turbulence (and any other kind of turbulence) is dependent on the mass of the object affected and the intensity of the turbulence. If you have a large aircraft with big wings generating lots of lift, the wake vortices will be correspondingly large. Another 777 following after it could ride it out easily since its mass can absorb the bumps (inertia is your friend), but a much lighter RJ might face serious problems.

That's one of the reasons ATC cares about the plane type. So they can adjust out the separation accordingly.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo

skyman
Posts: 484
Joined: Wed May 24, 2006 5:10 am

### RE: 777 Wake Tubulence Question

Here is a wake turbulence seperation list from Germany:
Heavy to Light 6NM
H to Medium 5NM
H to H 4NM
M to M 3NM
M to L 3NM
L to L 3NM
Otherwise aircraft are effected when flying less than 2 min behind the aircraft at ssame level or less than 1000ft below.

IAHFLYR
Posts: 3957
Joined: Sat Jun 25, 2005 12:56 am

### RE: 777 Wake Tubulence Question

In the US here is what the controller handbook requires unless the second aircraft is on a visual approach following the preceeding:

WAKE TURBULENCE APPLICATION

e. Separate aircraft operating directly behind, or directly behind and less than 1,000 feet below, or following an aircraft conducting an instrument approach by:

NOTE-
Consider parallel runways less than 2,500 feet apart as a single runway because of the possible effects of wake turbulence.

1. Heavy behind heavy- 4 miles.

2. Large/heavy behind B757- 4 miles.

3. Small behind B757- 5 miles.

4. Small/large behind heavy - 5 miles.

WAKE TURBULENCE APPLICATION

f. TERMINAL. In addition to subpara e, separate an aircraft landing behind another aircraft on the same runway, or one making a touch-and-go, stop-and-go, or low approach by ensuring the following minima will exist at the time the preceding aircraft is over the landing threshold:

NOTE-
Consider parallel runways less than 2,500 feet apart as a single runway because of the possible effects of wake turbulence.

1. Small behind large- 4 miles.

2. Small behind B757- 5 miles.

3. Small behind heavy- 6 miles.

The vorticies are supposed to sink at around 1,000' per minute but most US approach controls with RADAR don't use the minutes for separation they use the mileage rule.
Any views shared are strictly my own and do not a represent those of any former employer.

EssentialPowr
Posts: 1646
Joined: Wed Sep 06, 2000 10:30 pm

### RE: 777 Wake Tubulence Question

IAHFLYR knows his stuff...so my question, what 737 model causes you guys the most problems?

(your guys' label, our namesake!!)

skyman
Posts: 484
Joined: Wed May 24, 2006 5:10 am

### RE: 777 Wake Tubulence Question

 Quoting EssentialPowr (Reply 4):what 737 model causes you guys the most problems?

Was that question for me? If so I don`t quiet get it. In Germany approach also allmost only uses milage seperation due to the high traffic. Other things wouldn`t be practicable. So IAHFLYR must be an approach controller since he noes everything so good by heart. Or he had the handbook around.
We don`t really have big problems with the B737 but if you want to know the B737-200 allmost doesn`t fly here anymore due to the old engines. For noise abaitment rules and high fuel flow as well. Personally I like the B737-800 the best . A modern aircraft with a very good climbing performance.

IAHFLYR
Posts: 3957
Joined: Sat Jun 25, 2005 12:56 am

### RE: 777 Wake Tubulence Question

 Quoting EssentialPowr (Reply 4):IAHFLYR knows his stuff...so my question, what 737 model causes you guys the most problems?

I know nothing and can prove it....just watch your TCAS for abit!!!
.65 is always available but thanks for the kudos, and after that comment what you think you're gonna get direct REDOC or something special?

Hey he says the rackar is excellent and I will pass along a howdy to him today when I see him.

That model question for me or for SKYMAN??
Any views shared are strictly my own and do not a represent those of any former employer.

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