Wake Turbulence
 

Dear Learned Aviators,

Please could you provide your views on the issue of (B737, A319, etc.) taking 2 minutes behind a 757? Most of the Captains I fly with ask me to advise ATC that we require 2 Mins separation. Some, Pilots operating aircraft as small as an RJ100, just line up and hoon off in our place. :eek:

Personally, I think it is a very sensible request given the danger of a, low level, low energy, wake vortex encounter.

Any advice and information would be much appreciated. It is causing problems at busy airports like Gatwick.

Surely someone could give me a sound over view of this issue? Having searched the history, I have found little information on the 757 question.

If the RJ100 is able to rotate before the point where the 757 rotated, and is able to climb steeper (or turn on another heading in time), there's not a lot of chance that it will encounter the 757 wake, I'd say.

Wake
 

I was always led to believe the problem with 757's was following them on approach with their landing flap out. In the UK you get an extra mile, 4 as opposed to 3. Take off behind still only requires 1 minute, (medium behind medium) as far as i know.
I've encountered wake from a 757 on approach but never on departure.

Thanks for the feedback Guys,

An interesting point; the RJ departed from an intersection a long way down the runway. The 757 has a bad reputation for wake on departure as well as arrival.

Although a 757 is in the medium category (cut-off is 300,000lbs / 136T MTOW), the advice is that it's treated as heavy due to it's particalurly powerful wake vortex. The same applies to the B707, VC10 and IL62. I can personally vouch the VC10 has a very powerful wake vortex, and is in the heavy category anyway.

I'm not sure where this is written officially, but it appears in the AERAD supplement.

If the RJ did use an intersection, three minutes delay should have ben applied.

http://www.airliners.net/open.file?id=0856005
Steve Morris has some graphic proof of this :ouch:

The only additional seperation needed is on approach, 4nm if your in a 737 following a 757. Nothing special required for take off.

My company mentions this specificaly in its Gatwick brief.

Ashling - what airline do you work for?

As things stand, things at Gatwick need to be clarified for all operators. Is the full 2 minutes separtion between a 757 and other mediums required?? If not where is the proof?

Wake created at the point of take off is greater than at the point of landing.

UK CAA AIC 17/1999 (Pink 188) para 2.5.1 refers to this issue.

It refers to the 757 specificaly in the approach phase alongside other types and states the seperation needed on approach is 4nm. No reference is made to it in the departure phase and we can therefore take it that standard medium v medium rules apply.

My company rules follow this official guidance and are perfectly clear. No additional seperation required on departure. As a commander I can choose to add an additional safety factor to any limit if I consider it necesary, that is an individual choice and supported by the company.

As this is a public forum and I do not know the origin of posters or their motive I'll politely refrain from revealing the company in question as we are not permitted to quote on its behalf publicaly. Sorry.

For what it's worth, in the UK medium behind a mediun doesn't require any wake vortex spacing. Not sure what ICAO says though.

Wake
 

Spitoon, You are 100% correct. I suppose i do make a conscious effort not to rush on take off behind a 757 when i'm in a "medium"
Also out of interest i notice that German ATC regard the 757 as "Heavy" for wake turbulence purposes.

Same thing in Canada. 757 considered Heavy for wake turbulence.

Thanks Guys and Girls,

I am starting to think the Skippers that request 2 minutes are wise.:D

two minutes...!!!:eek:

you try training in a PA 38 Tomahawk behind a 757 also in the circuit...that is fun trying to get the sequencing right...:}

i did it for many years...and when we also had a 747 in the circuit as well....heavies to the right...PA 38 to the left...:eek:

apart for sequencing ...you get a pretty good idea of wake turbulance avoidence procedures....and hope..!!!

the dean.

So in Canada & Germany you apply 5 nms on approach and 2 mins for same point departure ?

Could you give me a ref for that ?

Ta

Danish rules say the same. Ref.:
"GEN 1.7 Differences from ICAO
Standards, Recommended
Practices and Procedures
Para 16.1.1. Wake Turbulence Spacing.
Boeing 757
In addition to Doc 4444 Part V item 16.1.1 the
Danish rules of the air contains the following provision:
Boeing 757 is categorized as a Wake Turbulence
category Medium aircraft. However, operational
experience indicates that the Boeing757 creates
more severe vortices than originally expected.
Consequently, Danish ATC-units will apply separation
to aircraft following or passing behind a
Boeing 757 as if the Boeing 757 was categorized
Heavy.
Issuing Wake Turbulence cautions to aircraft following
or passing behind a Boeing 757 ATS will
indicate that the preceding aircraft is a Boeing
757."

Yes, any official ref from Canada, Gremany, etc. would be appreciated!

N.R.B - Thanks for the Danish ref, if I follow, the 757 is treated like a heavy for all Wake Turb issues?

At home right now. This was from the VFR Guide. But correct as far as I remember: Considered as a "Heavy" for following (or crossing behind the 757) traffic? If a 757 "follows", it's "medium".

Thanks for the refs NRB, I'll check it out.