Boeing 757 wake turbulence separation criteria

[Centaurus]

I understand there are some Boeing 757 freighter aircraft operating in Australia. These aircraft have unusually severe wake turbulence output despite the 757 being in the Medium category for wake turbulence. So much so I believe ATC in UK increase separation of aircraft behind 757's on final approach from 3 miles to 4 miles. Does anyone know if Australian ATC apply the same criteria?

[Una Due Tfc]

Originally Posted by Centaurus

I understand there are some Boeing 757 freighter aircraft operating in Australia. These aircraft have unusually severe wake turbulence output despite the 757 being in the Medium category for wake turbulence. So much so I believe ATC in UK increase separation of aircraft behind 757's on final approach from 3 miles to 4 miles. Does anyone know if Australian ATC apply the same criteria?

ICAO SARPS are for the 757 to be treated as a medium when following and a heavy when being followed, so they can be 3nm behind a 737 on finals but that 737 would need to be 5nm behind the 757. The UK is non standard with ICAO when dealing with the 757, in that IIRC correctly they have a "small medium" and "large medium" category, possibly as a fudge to accommodate the large BA fleet of 757s that were at LHR with as little impact on movement rate as possible.

[krismiler]

Some places treat the B757 as a heavy for the traffic behind it, and as a medium for the traffic that it is following.

[le Pingouin]

Just the one 757 on the Australian register. It's treated as a heavy when leading and a medium when following - so 5 miles needed with the medium following it.

[Capn Bloggs]

AIP ENR 1.4 Section 9.1.1 refers:

Originally Posted by AIP

Note: B757 and H47 (Chinook) and H53 (Stallion) 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).

[Miles Magister]

The UK National Air Traffic Service (NATS) did some work on this a while ago and published the revised wake turbulence separation criteria for the UK in AIC P 3/2014 which is no longer published but I think I have attached a copy if anyone is interested.
This was quickly adopted by EuroControl and labeled ReCat (re-categorisation). You can find a 2015 EuroControl brief here Eu ReCat Briefon this and the current information here on SkyBrary. Worth a read.

MM

[Centaurus]

Thanks, chaps
I should have read the AIP first before posting. if I recall correctly it all started several years ago when a light jet was approaching to land behind a 757 somewhere overseas. The light jet stayed a dot high on the ILS thinking he would be above the 757 wake turbulence. But what he didn't know was the 757 had come in at a steeper angle than 3 degrees on a low drag approach at idle thrust. So despite the light jet staying higher than normal on the glide slope the 757 had also descended higher still on glide slope and planned to be on glide slope when much closer to the runway.
The light jet hit the 757 wake when both were close to the runway and flipped inverted.

[Dan Dare]

B757s within 4 nm often slow down a lot more than the following B738 etc. and I've often wondered whether the catch-up causes as many of the wake turbulence reports as the wing. In recent years many B757s have been retrofitted with winglets but I've never seen any research as to whether these have any benefit in wake turbulence reduction. As there are ever fewer B757s flying around I won't lose much sleep over it.

UK MATS Part 1 can be found www.caa.co.uk/cap493 Appendix B gives our current 6 category groupings although it has been updated by SI 2020/04 and further tweaked by some MATS 2s