B757 Wake cat?
 

Hello Ladies and Gents,

May I ask is the B757 classified as a Heavy or Medium with regard to
wake turb spacing. I fly a B737 and as far as I was aware we required 2
mins seperation from Heavy A/C. ( I was led to believe that the B757 was
classified as a heavy).

We asked for 2 mins spacing tonight at LGW and were told that in the UK
the B757 requires only 1 min spacing.

Sounds a bit strange to me, but I've been wrong before. We waited two mins just to be sure.

Best regards to all.

PMR

Although I'm sure someone more qualified than me will be able to elaborate further, the B757 is classified by ICAO as Medium (Source).

However, the FAA requires greater seperation due to increased wake vorticies from the 757. This Diagram shows this in a graphic, I do not have a text reference unfortunately.

anything above 136,000 KG MTOW is heavy. i think the 757 just comes into the heavy cat. (correct me if i am wrong)

None of you are correct, The B757 is classified as a "H" (heavy) for departure ahead of another aircraft and for wake turbulence intrail spacing in flight, and is categorised as a "M" (medium) when it is following preceding traffic, either on take off or in flight spacing.

So, a "H" departure (ie an A330) with a B757 to follow, then the 757 is considered to be an "M". If the B757 is ahead of a B737 (medium) then a wake turbulence spacing appropriate to a "H" leading is required.

I'm a Tower controller in Hong Kong.

757 preceding - heavy

757 following - medium


me thinks




bedder was a bit faster:ok:

At my last company the 757 & A310 were considered heavies, in my experience having flown a turboprop some years back even a fully laden 737 900 can give off some very nasty wake, so a 757 was going to be worse, a good call I think.

Bede believeit, what timing spacings are you using between heavy's on dept HKG ? Reason I ask is was queried by ctrlr in hkg when they cleared me for T/O and I told them I required longer due Wake seperation.

From The Boeing Company, MTOW of the:-

757-200 is 115,660 kilograms.
757-300 is 123,600 kilograms.

Which are both below the 136T threshold so are classified as a M. However, in the UK I believe the difference is that min spacing on approach is 4nm with a 757 ahead and a medium behind. No difference on departure.

As an aside, I have had worse wake from the old A320-100's (no winglets) than I have encountered from a 757!

Fire Wall
Technically there is no wake turbulence timing between two successive HEAVIES. Just sufficient distance to ensure that the aircraft are not closer than 4NM apart (with no closing) when the second aircraft gets airborne. However, here in Hong Kong - due to the fact that all SID departures are running for a considerable distance on the same track, and the DEPARTURES radar controller has little or no room to move, then we have our own in house ruling that we need 90 seconds (generally) between successive HEAVY departures. Once again, this is very much a generalisation. Under some circumstances we provide 2, and even 3 minutes separation for certain sets of HEAVIES. Normally it can be somewhat difficult to get much less than 90 secs between two large aircraft due to the fairly ponderous nature they exhibit in entering the runway and then taking off. Let's be honest, the aircraft doesn't roll until the crew advance the throttles (and if necessary - release brakes).

Having looked into it a bit further, it seems that in the UK the 2 minutes on departure with a 757 leading and a medium behind is not enforced, only for aircraft in flight (ie on approach). Therefore we go back to Pimp's original question, and it looks like ATC won't give the 2 minutes!!!!!!!!!!!!! Back to the olympics.

As mentioned before, most ATC units in Europe (my experience) handle the 757 as 'medium' when following, and as 'heavy' when preceeding.

On the other hand, I made the same experience as Pimp My Ride in LHR, so we always tell ATC that we need 2 mins seperation behind the departing 757 in front. That was never a problem, just have to tell ATC well in advance to keep them in the loop.

Regards

The B757 is a medium aircraft producing a heavy wake; two different things! Thus it is considered m when following and h when preceding.

Just to add to all the confusion.........by the way thank you for all the informative replies.

I've just checked out my company B737NG ops man. It states that for departure in the UK, only 1 min seperation will be provided and my company has accepted this policy. The commander should state if he/she requires more. So I've basically just shown myself up
as I didnt have a clue that this was there.

The issue really only arose as we had been cleared to line up after the departing B757. My switched on colleague pointed out that there was traffic on approach. We stopped well short of the active RW and clarified that we needed 2 mins spacing. Had we asked after line up a G/A would have probably have been required. I really thought that 2 mins was the minimum provided. The controller asked us in future to inform ATC earlier.

You learn something new every day in this game.

Thanks to you all!!

PMR

I'll throw this in as I remember reading it yesterday - straight from the Australian docs: "B757 and H47 (Chinook) are categorised Heavy (H) when the following aircraft is categorised either Medium (M) or Light (L) and categorised Medium (M) when the preceding aircraft is categorised Heavy (H)" (Jepp ATC AU-810 5.4.1.1).

Not that we have many, or any, B757s in Oz. Not sure if this is slightly different from other countries.

It is as simple as this. The 757 is a medium sized aircraft that is treated as a heavy due to the wake it produces.

Greetings
Indeed, I have encountered one, it is nasty :eek: and I was on a 767 300

Hello,

This topic appeared before.

http://www.pprune.org/forums/tech-lo...eavy-wake.html

I loooked at CAP 493 - Manual of Air Traffic Services also
AIC 17/1999 (Wake Turbulence)
and none seem to show this 1 minute limit.

These docs indicate a 2 minute separation should be given when
departing behind a Boeing 757.

Anyone know where (what publication) this 1 minute comes from ?

ASA87 I couldn't find this in either of the docs you mentioned - as far as I can see there is only a rule regarding 757 separation on approach.

I'm interested in this topic - our Ops manuals are basically worded as per AIC 17/99 (Pink 188) and no one has so far shown me a reference for a departure rule regarding 757 v a following M category, though there seems to be a wealth of anecdotal evidence supporting the "2min rule".

I'd appreciate any official references.

Jeppesen ERM, ATC page GERMANY-3 says that Germany has special B757 wake category. Basically Germans classify 757 as heavy, and provide medium-following-heavy (for 757 trailing heavy, that is) separation only upon pilots' request.

Thank you for bringing up this topic, Pimp my ride. I thought that 2 mins behind B757 was worldwide standard too.

Here in the states, for many years, 300,000 lbs was the seperation limit for heavies.
That included the 707's and the DC-8's, that went up to 355,000 lbs. That was the way it was for years, until the B-757 poked its ugly head out and turned a few aircraft up side down. When the federalies realised this, they lowered the "heavy" catagory down to 225,000 lbs to include the 757.

The company I worked for at the time, had one very odd DC-8 that had a MGTO weight of 293,000 lbs. Guess what? We had a few nutcases that insisted that we tell ATC that we were not a "heavy". I pitied the poor sod behind us that had to encounter our wake over a pidly 7000 lbs. I'm sure that was not in their daily program!

Bedder Believe it; I should be back in HKG soon. Put on your suds shoes!

P