Web500sjc
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### Why Is 757 A "Heavy"?

I realize the topic of whether a 757 is a heavy has been talked to death.

What i would like to know what causes the 757 wake turbulence to be so strong that it is classified as a heavy, and do winglets soften the wake turbulence?
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tdscanuck
Posts: 8572
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### RE: Why Is 757 A "Heavy"?

 Quoting web500sjc (Thread starter):What i would like to know what causes the 757 wake turbulence to be so strong that it is classified as a heavy

The vortex (wake turbulence) strength is, roughly, a function of weight and span. More weight increases vortex strength, more span decreases it. The 757 happens to live in a realm where its combination of weight and span results in enough turbulence to meet the "heavy" classification. It's at the low end of heavy, obviously.

 Quoting web500sjc (Thread starter):and do winglets soften the wake turbulence?

Yes.

Tom.

Mir
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### RE: Why Is 757 A "Heavy"?

 Quoting web500sjc (Thread starter):What i would like to know what causes the 757 wake turbulence to be so strong that it is classified as a heavy

A relatively short span in comparison to the size of the aircraft. That will make the vortices bigger.

And, just to make it clear, not all 757s are "heavy" - those with MTOWs under 255,000lbs are "large", with separation befitting a "heavy" given to aircraft following them.

-Mir
7 billion, one nation, imagination...it's a beautiful day

747400sp
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### RE: Why Is 757 A "Heavy"?

I think it mostly 757 200Es, and maybe 757 300s with the heavy call sign.

Mir
Posts: 19269
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### RE: Why Is 757 A "Heavy"?

 Quoting 747400sp (Reply 3):maybe 757 300s

All 757-300s are heavy. It's the 757-200 where some are and some aren't.

-Mir
7 billion, one nation, imagination...it's a beautiful day

Web500sjc
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### RE: Why Is 757 A "Heavy"?

So if it is the small size of the wing that is the root of the problem, why does the 757 have good hot and high performance?
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tdscanuck
Posts: 8572
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### RE: Why Is 757 A "Heavy"?

 Quoting web500sjc (Reply 5):So if it is the small size of the wing that is the root of the problem, why does the 757 have good hot and high performance?

It's specifically small *span* relative to weight. Vortex strength doesn't care about wing area (much), just span. The 757 still has lots of wing area and thrust, which is where the good hot/high performance comes from.

Tom.

Starlionblue
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### RE: Why Is 757 A "Heavy"?

 Quoting web500sjc (Thread starter):Why Is 757 A "Heavy"?

Have you ever tried to lift one?
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo

KingFriday013
Posts: 879
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### RE: Why Is 757 A "Heavy"?

 Quoting Starlionblue (Reply 7):Have you ever tried to lift one?

With that logic, a Dash 8 is heavy (at least for me!)

-J.
Tho' I've belted you an' flayed you, By the livin' Gawd that made you, You're a better man than I am, Gunga Din!

Fabo
Posts: 1154
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### RE: Why Is 757 A "Heavy"?

 Quoting kingFriday013 (Reply 8):With that logic, a Dash 8 is heavy (at least for me!)

Why stop at Dash 8, most single Cessnas are heavy
The light at the end of tunnel turn out to be a lighted sing saying NO EXIT

Fly2HMO
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Joined: Sat Jan 24, 2004 12:14 pm

### RE: Why Is 757 A "Heavy"?

 Quoting Fabo (Reply 9): Why stop at Dash 8, most single Cessnas are heavy

Hardly. A fully loaded C172 is barely heavier than a VW Beetle.

2H4
Posts: 7960
Joined: Tue Oct 19, 2004 11:11 pm

### RE: Why Is 757 A "Heavy"?

Past discussions have shown how the 757s strong wake turbulence can be attributed more to its wing flap geometry than the general size and shape of the wing. Wake imaging photos revealed very strong vorticies being shed from the edges of the flaps. These vorticies were noticeably stronger than those shed from the wingtips.
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seabosdca
Posts: 5159
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### RE: Why Is 757 A "Heavy"?

The "heavy" classification starts at 255,000 lbs MTOW. The heaviest of several possible MTOW options for the 757-200 is 255,500 lbs. (The 757-300 tops out at 272,500 lbs.)

That said, you will hear "heavy" used inconsistently by 752 pilots.

Caryjack
Posts: 312
Joined: Tue May 08, 2007 9:45 am

### RE: Why Is 757 A "Heavy"?

 Quoting tdscanuck (Reply 1):The vortex (wake turbulence) strength is, roughly, a function of weight and span. More weight increases vortex strength, more span decreases it.

I understand that wing tip vortices cause drag and are a target for design engineers. Innovations such as air dams and winglets limit air flow off the wing ends which increases air flow over the wings, thereby increasing lift, and reducing vortices and drag. Raked tips diminish the wing until an insignificant amount of airflow travels off the tip thereby minimizing the vortices. At least that's how I see it.

 Quoting Mir (Reply 2):And, just to make it clear, not all 757s are "heavy" - those with MTOWs under 255,000lbs are "large", with separation befitting a "heavy" given to aircraft following them.

Thanks for the effort.    So if the 757 is under 255,000 lbs and classified as "large", it’s just best to give a separation as if the 757 were a "heavy", right?
And while you're at it,    we’re dealing with three classifications, "large", "heavy" and "super" for commercial traffic, right? Are the big, twin turboprops considered "large"?

 Quoting SeaBosDca (Reply 12):That said, you will hear "heavy" used inconsistently by 752 pilots.

Who calls it, the pilots or ATC? Once called, does this set seperations?

 Quoting 2H4 (Reply 11):Past discussions have shown how the 757s strong wake turbulence can be attributed more to its wing flap geometry than the general size and shape of the wing.

This is my understanding. I would guess that flap tip vortices are tolerated because they only show up during takeoffs and landings so there are no efficiencies to be gained by eliminating them.

 Quoting 2H4 (Reply 11):Wake imaging photos revealed very strong vortices being shed from the edges of the flaps. These vortices were noticeably stronger than those shed from the wingtips.

These noticeably stronger vortices are only an issue during takeoff and landings, right?

Thanks,
Cary

Starlionblue
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### RE: Why Is 757 A "Heavy"?

As I understand it, ATC isn't this blunt anyway. They don't just lump heavies into one category and "diets" into the other. Different planes get different separation, even within "heavy" and such.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo

KELPkid
Posts: 5247
Joined: Wed Nov 02, 2005 5:33 am

### RE: Why Is 757 A "Heavy"?

 Quoting Fabo (Reply 9):Why stop at Dash 8, most single Cessnas are heavy

You have an interesting definition of the word, then   A 152 or 172 can be easily moved around the ramp by hand by a single human being (and I used to do that for a living). I wouldn't want to lift one, though, but you can easily manipulate their position on the ground using towbars, the prop, wing struts, and even pushing the tail down (word to the wise-don't try pushing the tail down unless you know what you are doing. You can damage the plane easily if you don't).

The 182 is a little harder to move around the ramp in this manner, the 206 even worse, and the 210 is pretty darned hard for one person to move (if you are going to move a 210 for a significant distance, I would recommend the use of a ramp vehicle with an appropriate towbar...).
Celebrating the birth of KELPkidJR on August 5, 2009 :-)

jgarrido
Posts: 258
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### RE: Why Is 757 A "Heavy"?

 Quoting Caryjack (Reply 13):Thanks for the effort. So if the 757 is under 255,000 lbs and classified as "large", it’s just best to give a separation as if the 757 were a "heavy", right?

It's not just a good idea. There are specific separation requirements for those 757-200's MTOW is under 255k lbs.

 Quoting Starlionblue (Reply 14):As I understand it, ATC isn't this blunt anyway. They don't just lump heavies into one category and "diets" into the other. Different planes get different separation, even within "heavy" and such.

Separation on final is based on weight class (small, large, heavy, super), the non-255k MTOW 752 is the only aircraft which has special separation rules.

2H4
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### RE: Why Is 757 A "Heavy"?

 Quoting Caryjack (Reply 13):These noticeably stronger vortices are only an issue during takeoff and landings, right?

My understanding is that they are an issue whenever the flaps are lowered.

 Quoting KELPkid (Reply 15):The 182 is a little harder to move around the ramp in this manner, the 206 even worse, and the 210 is pretty darned hard for one person to move

This time of year, getting them stopped is the larger concern.
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Fabo
Posts: 1154
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### RE: Why Is 757 A "Heavy"?

 Quoting KELPkid (Reply 15):A 152 or 172 can be easily moved around the ramp by hand by a single human being (and I used to do that for a living). I wouldn't want to lift one, though

Yes I know it is a pretty easty plane to move around, but talk was about lifting

About sitting on the tail thing - been there, done that. It is amazing how many planes can people on Kladno airfield fit into their little hanger
The light at the end of tunnel turn out to be a lighted sing saying NO EXIT

IAHFLYR
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### RE: Why Is 757 A "Heavy"?

 Quoting Mir (Reply 4):All 757-300s are heavy. It's the 757-200 where some are and some aren't.
 Quoting Mir (Reply 2):those with MTOWs under 255,000lbs are "large", with separation befitting a "heavy" given to aircraft following them.

All the above is correct. Tis the MTOW that classifies the aircraft category, not the wake turbulence a particular aircraft may or may not leave behind. I've heard the B738's leave a pretty nasty wake and they are not even close to a MTOW in the 200,000 lbs area.

 Quoting SeaBosDca (Reply 12):you will hear "heavy" used inconsistently by 752 pilots.

That is very interesting since I very rarely hear (and I hear quite a few) a crew of a B752 mistakenly use "Heavy" in their call sign.....even with operators that have both the 200 and 300 in their fleets.
Any views shared are strictly my own and do not a represent those of any former employer.

Mir
Posts: 19269
Joined: Mon Jan 05, 2004 3:55 am

### RE: Why Is 757 A "Heavy"?

 Quoting FLY2HMO (Reply 10):A fully loaded C172 is barely heavier than a VW Beetle.

Still, have you tried to lift one?
 Quoting Starlionblue (Reply 14):Different planes get different separation, even within "heavy" and such.

Not as I learned it. There is no requirement to give a 747 any more separation than a 777.

 Quoting Caryjack (Reply 13):So if the 757 is under 255,000 lbs and classified as "large", it’s just best to give a separation as if the 757 were a "heavy", right?

Not if it is the trailing aircraft. Remember that not only is wake turbulence about how bad the wake of an aircraft is, it's also about how easily that aircraft can be affected by the wake of other aircraft. If you've got a heavy following another heavy, the minimum separation is 4 miles. If it's a large following a heavy, the minimum separation is 5 miles, because it's assumed that a smaller airplane will have a worse reaction should it encounter the wake generated by the heavy. And since a 757 is technically a large, you need to give it 5 miles instead of 4. And before you ask, a 757 following another 757 needs 4 miles.

To explain it better:

- Heavy behind a heavy: 4 miles
- Small or large behind a heavy: 5 miles
- Large or heavy behind a 757: 4 miles
- Small behind a 757: 5 miles

EDIT: I should add that there are further separations given to small aircraft when following a non-small aircraft on final approach:

- Small behind large: 4 miles
- Small behind 757: 5 miles
- Small behind heavy: 6 miles

Note that the term "757" means a 757 that is not over 255k. If it were over 255k, it would be a "heavy", and treated as such.

Confused yet?

-Mir

[Edited 2010-02-17 06:20:41]
7 billion, one nation, imagination...it's a beautiful day

Starlionblue
Posts: 17578
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### RE: Why Is 757 A "Heavy"?

 Quoting Mir (Reply 20):Quoting Starlionblue (Reply 14): Different planes get different separation, even within "heavy" and such. Not as I learned it. There is no requirement to give a 747 any more separation than a 777.

I stand corrected.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo

seabosdca
Posts: 5159
Joined: Sat Sep 01, 2007 8:33 am

### RE: Why Is 757 A "Heavy"?

 Quoting IAHFLYR (Reply 19):That is very interesting since I very rarely hear (and I hear quite a few) a crew of a B752 mistakenly use "Heavy" in their call sign.....even with operators that have both the 200 and 300 in their fleets

I'm more thinking of the other way around... crew of 255,500 lb. 752s, like all of the ones in the CO fleet and Delta's 75Es, failing to use "heavy" sometimes. Given the special procedures for non-heavy 757s I'd imagine this makes little difference.

IAHFLYR
Posts: 3946
Joined: Sat Jun 25, 2005 12:56 am

### RE: Why Is 757 A "Heavy"?

 Quoting SeaBosDca (Reply 22):I'm more thinking of the other way around... crew of 255,500 lb. 752s, like all of the ones in the CO fleet and Delta's 75Es, failing to use "heavy" sometimes. Given the special procedures for non-heavy 757s I'd imagine this makes little difference.

Well I don't hear that mistake much at all either. Almost without fail the crew uses the correct "Heavy" or not for the aircraft they are flying.
Any views shared are strictly my own and do not a represent those of any former employer.

XFSUgimpLB41X
Posts: 3961
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### RE: Why Is 757 A "Heavy"?

 Quoting SeaBosDca (Reply 22):I'm more thinking of the other way around... crew of 255,500 lb. 752s, like all of the ones in the CO fleet and Delta's 75Es, failing to use "heavy" sometimes. Given the special procedures for non-heavy 757s I'd imagine this makes little difference.

No one at Delta in a 752 is failing to use heavy. No Delta "75E's" are certified for above 255,000 pounds, therefore they do not use "heavy." Same with the "75A."

The only Delta 757's that would use "heavy" are the 757-300s.
Chicks dig winglets.

Web500sjc
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### RE: Why Is 757 A "Heavy"?

at SNA as far as I know every time there is a 757 its always "XXX YYY heavy, cleared to land runway 19R". but then again that is the only thing close to heavy we get at SNA.
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XFSUgimpLB41X
Posts: 3961
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### RE: Why Is 757 A "Heavy"?

 Quoting web500sjc (Reply 25): at SNA as far as I know every time there is a 757 its always "XXX YYY heavy, cleared to land runway 19R". but then again that is the only thing close to heavy we get at SNA.

That's not correct. Only if the aircraft is certified as a heavy will you hear it.

It's not a term that is applied to something that is relatively heavy to the usual traffic.
Chicks dig winglets.

IAHFLYR
Posts: 3946
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### RE: Why Is 757 A "Heavy"?

 Quoting web500sjc (Reply 25):at SNA as far as I know every time there is a 757 its always "XXX YYY heavy, cleared to land runway 19R". but then again that is the only thing close to heavy we get at SNA.

I've never known any operator of a B753 to be used at SNA! So what are you actually hearing on the radio???
Any views shared are strictly my own and do not a represent those of any former employer.

Max777geek
Posts: 159
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### RE: Why Is 757 A "Heavy"?

 Quoting Mir (Reply 4): All 757-300s are heavy. It's the 757-200 where some are and some aren't.
 Quoting Starlionblue (Reply 7):Have you ever tried to lift one?

Mir can lift some. You guys make my forum, yuk

 Quoting SeaBosDca (Reply 12):The "heavy" classification starts at 255,000 lbs MTOW. The heaviest of several possible MTOW options for the 757-200 is 255,500 lbs. (The 757-300 tops out at 272,500 lbs.) That said, you will hear "heavy" used inconsistently by 752 pilots.

very proud to be heavy. Are the wake turbolence so different from a 757 which weights 254.500 lbs and one that weights 255.500 lbs ? if it's heavy at 255.500 it's at 254.500 too

XFSUgimpLB41X
Posts: 3961
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### RE: Why Is 757 A "Heavy"?

 Quoting Max777geek (Reply 28):very proud to be heavy. Are the wake turbolence so different from a 757 which weights 254.500 lbs and one that weights 255.500 lbs ? if it's heavy at 255.500 it's at 254.500 too

"heavy" is not used off of actual weight. It is only based on certified max takeoff weight. Certified to 255,000 pounds or less? Not a heavy.

Certified to 255,001 pounds or more? heavy.
Chicks dig winglets.

seabosdca
Posts: 5159
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### RE: Why Is 757 A "Heavy"?

 Quoting XFSUgimpLB41X (Reply 24):No one at Delta in a 752 is failing to use heavy. No Delta "75E's" are certified for above 255,000 pounds, therefore they do not use "heavy." Same with the "75A."

I've read in multiple places that the Delta 75Es are certified to 255,500. Is this incorrect?

XFSUgimpLB41X
Posts: 3961
Joined: Fri Aug 25, 2000 1:18 am

### RE: Why Is 757 A "Heavy"?

That is incorrect.

256,000 max taxi weight.

255,000 max takeoff.

Not a heavy!
Chicks dig winglets.

Max777geek
Posts: 159
Joined: Wed Mar 07, 2007 6:20 pm

### RE: Why Is 757 A "Heavy"?

 Quoting XFSUgimpLB41X (Reply 29):"heavy" is not used off of actual weight. It is only based on certified max takeoff weight. Certified to 255,000 pounds or less? Not a heavy. Certified to 255,001 pounds or more? heavy.

tought that wasn't about weight but to inform followers of possible close turbolence ingenerated by the wings. So I was wondering why such a specific limit, the turbolence isn't any different one pound below the limit right ?

tdscanuck
Posts: 8572
Joined: Wed Jan 11, 2006 7:25 am

### RE: Why Is 757 A "Heavy"?

 Quoting Max777geek (Reply 32):tought that wasn't about weight but to inform followers of possible close turbolence ingenerated by the wings.

It is. The turbulence generated is related to the weight, and you need some way to distinguish the light variants from the heavy ones.

 Quoting Max777geek (Reply 32):So I was wondering why such a specific limit, the turbolence isn't any different one pound below the limit right ?

You need to draw the line somewhere. The turbulence is a little different one pound below (but not much, obviously). The alternative would be some kind of pro-rated following distance with weight, which would be more technically correct but a horrible pain in the rear for ATC to actually use.

Tom.

Web500sjc
Posts: 665
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### RE: Why Is 757 A "Heavy"?

 Quoting IAHFLYR (Reply 27):Quoting web500sjc (Reply 25): at SNA as far as I know every time there is a 757 its always "XXX YYY heavy, cleared to land runway 19R". but then again that is the only thing close to heavy we get at SNA. I've never known any operator of a B753 to be used at SNA! So what are you actually hearing on the radio???

People say xxx yyy heavy to land/ ready for take off and they are not fedex or ups, and considering those are the only widebodies at SNA I assume the heavies also refer to 757, also I have heard SNA twr reply xxx yyy heavy cleared to land/ takeoff, again not a ups or fedex. If you have any other ideas as to what those aircraft are please reply.
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bond007
Posts: 4425
Joined: Mon Mar 14, 2005 2:07 am

### RE: Why Is 757 A "Heavy"?

 Quoting web500sjc (Reply 34): If you have any other ideas as to what those aircraft are please reply.

Well, perhaps you just tell us what they were!
Then we won't be guessing and questioning, right?

Jimbo
I'd rather be on the ground wishing I was in the air, than in the air wishing I was on the ground!

ednovak
Posts: 13
Joined: Wed Mar 07, 2007 10:45 pm

### RE: Why Is 757 A "Heavy"?

This just in...as of April 8, the B757 is no longer considered a heavy by the FAA, regardless of weight or model. See FAA Notice JO 7110.520.

IAHFLYR
Posts: 3946
Joined: Sat Jun 25, 2005 12:56 am

### RE: Why Is 757 A "Heavy"?

 Quoting ednovak (Reply 36):This just in...as of April 8, the B757 is no longer considered a heavy by the FAA, regardless of weight or model. See FAA Notice JO 7110.520.

Yeah I learned of that about a month back, but till it came out in the press I was not sure if true or not. Can't wait to find the NOTICE and see how gooned up this will turn out.
Any views shared are strictly my own and do not a represent those of any former employer.

jgarrido
Posts: 258
Joined: Thu Mar 08, 2007 4:40 pm

### RE: Why Is 757 A "Heavy"?

The faa simplifying things? I don't believe it!!!

http://www.faa.gov/regulations_polic...ment.information/documentID/215069

seabosdca
Posts: 5159
Joined: Sat Sep 01, 2007 8:33 am

### RE: Why Is 757 A "Heavy"?

Kind of surprised they included the heavier 757-300 in the decision.

To summarize, all 757 regardless of MTOW or model are now "large" when following and "B757," neither large nor heavy, when leading.

avioniker
Posts: 1100
Joined: Tue Jan 01, 2002 5:38 am

### RE: Why Is 757 A "Heavy"?

History, kids:

The 57 fleet got the heavy designation put on them after a number of incidents involving wake turbulence at extended distances relative to the aircraft weight.
The defining incident was in Dec 1993 when a southbound L1011 was batted around to the tune of 5000 feet when crossing the wake of an eastbound 757 out of SFO. The 57 was more than five miles ahead of the wake that the 1011 went through. A number of passengers and a couple of flight attendants (or was it still stewardii then?) were rather severly injured.
After the normal FAA "soul searching" and wailing and gnashing of teeth it was decided to call 757's heavy until a better fix could be put in place. In tests performed at the Atlantic City FAA labs and in the air it was found that the 757's produced significant wake turbulence at as far behind the aircraft as 15 miles when they were accelerating. That caused the FAA to increase the following distances and, hopefully, made the skys safe from the whirling spinning air behind the 57 aircraft, especially when they were accelerating.
The new spacing, approach control, and slot system has pretty well done away with the need for this designation.

Jeeze I'm starting to feel old when everyone else seems to have forgotten or not known about events from less than 20 years ago.

One may educate the ignorance from the unknowing but stupid is forever. Boswell; ca: 1533

IAHFLYR
Posts: 3946
Joined: Sat Jun 25, 2005 12:56 am

### RE: Why Is 757 A "Heavy"?

 Quoting avioniker (Reply 40):History, kids: The 57 fleet got the heavy designation put on them after a number of incidents involving wake turbulence at extended distances relative to the aircraft weight. The defining incident was in Dec 1993 when a southbound L1011 was batted around to the tune of 5000 feet when crossing the wake of an eastbound 757 out of SFO. The 57 was more than five miles ahead of the wake that the 1011 went through. A number of passengers and a couple of flight attendants (or was it still stewardii then?) were rather severly injured. After the normal FAA "soul searching" and wailing and gnashing of teeth it was decided to call 757's heavy until a better fix could be put in place. In tests performed at the Atlantic City FAA labs and in the air it was found that the 757's produced significant wake turbulence at as far behind the aircraft as 15 miles when they were accelerating. That caused the FAA to increase the following distances and, hopefully, made the skys safe from the whirling spinning air behind the 57 aircraft, especially when they were accelerating. The new spacing, approach control, and slot system has pretty well done away with the need for this designation. Jeeze I'm starting to feel old when everyone else seems to have forgotten or not known about events from less than 20 years ago.

Please expand on your statements, I may require special handling on this.

The decision you refer to call 757's heavy until a better fix was put in place, exactly how many miles separation for another aircraft, say a B727 was required following this B757 heavy?

What was the MTOW of this 757 and did it cause the heavy category to be changed as well?

What new spacing, approach control, and slot system is now in place that has pretty much done away with this designation?

The history lesson continues!
Any views shared are strictly my own and do not a represent those of any former employer.

HAWK21M
Posts: 30002
Joined: Fri Jan 05, 2001 10:05 pm

### RE: Why Is 757 A "Heavy"?

The Wake produced by a B757 can be quite serious.

regds
MEL.
I may not win often, but I damn well never lose!!!

Caryjack
Posts: 312
Joined: Tue May 08, 2007 9:45 am

### RE: Why Is 757 A "Heavy"?

 Quoting Mir (Reply 20):Not if it is the trailing aircraft. Remember that not only is wake turbulence about how bad the wake of an aircraft is, it's also about how easily that aircraft can be affected by the wake of other aircraft.

Thanks. I had thought of trailing and following but I after going in a few circles I thought of something else.

 Quoting Mir (Reply 20):Note that the term "757" means a 757 that is not over 255k. If it were over 255k, it would be a "heavy", and treated as such.

According to JO 7117.52 as posted by ednovak above, certain Boeing B752s and B753s capable of takeoff weights of more than 255,000 pounds will be in the "Large" category. B-757s that had been considered "Heavy" as lead aircraft will now be considered "B757s" but I don't see a specific category for them.

http://www.faa.gov/documentLibrary/media/Notice/N7110.520.pdf

 Quoting ednovak (Reply 36):This just in...as of April 8, the B757 is no longer considered a heavy by the FAA, regardless of weight or model. See FAA Notice JO 7110.520.

This notice says that a heavy aircraft is one that is capable of a takeoff weight of more than 255,000 pounds, whether or not they are operating at this weight during a particular phase of flight. It also differentiates between B752, B753 and B757 with the B757 having previously been considered "Heavy". This notice is subject to JO 7110.65, par 5-5-4 which was spelled out by Mir in his post #20. http://www.faa.gov/air_traffic/publications/at_orders/media/ATC.pdf

 Quoting Mir (Reply 20):If it's a large following a heavy, the minimum separation is 5 miles, because it's assumed that a smaller airplane will have a worse reaction should it encounter the wake generated by the heavy. And since a 757 is technically a large, you need to give it 5 miles instead of 4. And before you ask, a 757 following another 757 needs 4 miles. To explain it better: - Heavy behind a heavy: 4 miles - Small or large behind a heavy: 5 miles - Large or heavy behind a 757: 4 miles - Small behind a 757: 5 miles

This indicates that B757s can be given special separation. Also from JO 7110.65: "heavy aircraft and the Boeing 757 are permitted to participate in the separation as trailing aircraft only." This is another indication that heavies and the B757 are still considered the same under certain conditions.

Yes, I'd say so.    It does seem clear that the B757 can be considered a heavy when leading and is a large when following.

Just curious, would a new weight category for the A-380 show up in 7110.65?

Thanks,
Cary

jgarrido
Posts: 258
Joined: Thu Mar 08, 2007 4:40 pm

### RE: Why Is 757 A "Heavy"?

 Quoting Caryjack (Reply 43):According to JO 7117.52 as posted by ednovak above, certain Boeing B752s and B753s capable of takeoff weights of more than 255,000 pounds will be in the "Large" category. B-757s that had been considered "Heavy" as lead aircraft will now be considered "B757s" but I don't see a specific category for them.

To be clear notice 7110.520 does not go into effect until April. So in an official sense it has no merit yet.

 Quoting Caryjack (Reply 43):This is another indication that heavies and the B757 are still considered the same under certain conditions.

This is all semantics, but because of the fact that it is listed separately means it is not considered a heavy. Otherwise it would be listed as a heavy and there wouldn't' need to be a special mention.

 Quoting Caryjack (Reply 43):Yes, I'd say so. It does seem clear that the B757 can be considered a heavy when leading and is a large when following.

That's another oversimplification. First off "can" is a bad word. It implies something that's optional. There are required additional separation requirements for a 757 that are greater that that of a large. Secondly if you notice that a large behind a heavy requires 5 miles separation, but a large behind a 757 only requires 4. The separation on final shows another exception. Small behind a 757 is 5 miles, whereas if it were simply considered a heavy when leading it would be 6.

[Edited 2010-02-27 17:39:25]

[Edited 2010-02-27 17:43:15]

Caryjack
Posts: 312
Joined: Tue May 08, 2007 9:45 am

### RE: Why Is 757 A "Heavy"?

 Quoting jgarrido (Reply 16):Separation on final is based on weight class (small, large, heavy, super), the non-255k MTOW 752 is the only aircraft which has special separation rules.

Just curious, where does "super" show up? I haven't notice that classification in the FAA documents plastered about.

 Quoting jgarrido (Reply 44):To be clear notice 7110.520 does not go into effect until April. So in an official sense it has no merit yet.

Fine, but what happens when it does go into effect? Certainly the vortices depicted in HAWK21M's post #42 aren't going away.
As far as I can see 1710.520 changes the "Heavy" label to "B757" on on certain 757s in 7110.65. It also adds or changes a "Heavy" weight class to Appendix A of that document to 255,000 pounds. Any B-757 with a TOW over 255,000 pounds is a heavy, right?

 Quoting jgarrido (Reply 44):fact that it is listed separately means it is not considered a heavy. Otherwise it would be listed as a heavy and there wouldn't' need to be a special mention.

I understand that B757s maybe considered heavy as far as spacing is concerned. "B757 aircraft that had previously been considered "Heavy" as the lead aircraft ... will now be considered "B757s." This from the Explanation of Policy Change section of 7110.520. Thanks for the link.

 Quoting jgarrido (Reply 38):The faa simplifying things? I don't believe it!!!    http://www.faa.gov/regulations_polic...15069
 Quoting jgarrido (Reply 44):Secondly if you notice that a large behind a heavy requires 5 miles separation, but a large behind a 757 only requires 4. The separation on final shows another exception. Small behind a 757 is 5 miles, whereas if it were simply considered a heavy when leading it would be 6.

Not to oversimplify but It depends on the situation.

 Quoting Mir (Reply 20):To explain it better: - Heavy behind a heavy: 4 miles - Small or large behind a heavy: 5 miles - Large or heavy behind a 757: 4 miles - Small behind a 757: 5 miles EDIT: I should add that there are further separations given to small aircraft when following a non-small aircraft on final approach: - Small behind large: 4 miles - Small behind 757: 5 miles - Small behind heavy: 6 miles

I'd guess that Mir pulled the first set from 7110.65-5-5-4-g-2 and most likely got the second set from nearly the same location. I'll say that situations can occur where B-757 are given spacing as if they were a heavy.

Thanks,
Cary

jgarrido
Posts: 258
Joined: Thu Mar 08, 2007 4:40 pm

### RE: Why Is 757 A "Heavy"?

 Quoting Caryjack (Reply 45):Just curious, where does "super" show up? I haven't notice that classification in the FAA documents plastered about.

Super is another weight class, not an exception like the 757. It just so happens that there is only one type of A/C in that weight class.

 Quoting Caryjack (Reply 45):Fine, but what happens when it does go into effect? Certainly the vortices depicted in HAWK21M's post #42 aren't going away. As far as I can see 1710.520 changes the "Heavy" label to "B757" on on certain 757s in 7110.65. It also adds or changes a "Heavy" weight class to Appendix A of that document to 255,000 pounds. Any B-757 with a TOW over 255,000 pounds is a heavy, right?

I don't know a lot about 757's but I didn't see any way to tell if the 757's in MAWK21M's pictures where -200, -200 w/ MTOW >255k lbs or -300's. However there will still be extra separation for 757's after April, but all 757's will be treated the same. To recap: Boeing built an airplane which fit into the large weight class, but who's wake necessitated increased spacing so an exception to the the rule was made. Then they made new models of that same plane which fit into the heavy weight class making them exceptions to the exception. Come April the FAA has decided to consolidate the exceptions. Don't ask me why or how they justify can lumping 757's who's MTOW is > 255k lbs back into the large weight class, because that's beyond both my expertise and care level.

 Quoting Caryjack (Reply 45): "B757 aircraft that had previously been considered "Heavy" as the lead aircraft ... will now be considered "B757s."

That quote is taken from the Explanation of Policy Change which is just an explanation it isn't regulatory. In the .65 (which is regulatory) there are two area's where the 757 is not the same as a heavy when being followed. No where in the .65 does it say the "in section x-x-x consider the 757 a heavy" or similar. It only says to apply special handling to them in certain wake turbulence applications, but this can "largely" (bad pun?) be boiled down to semantics. "Considered" a heavy or merely "share" certain heavy rules?

 Quoting Caryjack (Reply 45):I'd guess that Mir pulled the first set from 7110.65-5-5-4-g-2 and most likely got the second set from nearly the same location. I'll say that situations can occur where B-757 are given spacing as if they were a heavy.

Like I said it's semantics. There's two ways to think about it. You can consider the 757 a large, except when leading. When leading it's a heavy: except when it's leading A: a large or B: a small on final. When leading a large or small on final it's neither a large nor a heavy. Or just think of the 757 a special a/c with it's own set of separation requirements. I prefer the to limit the number exception's I have to deal with and just remember the rules. Even after the April notice goes into effect there's still a ton of exceptions to apply. I'd be even happier if they just said "consider all 757's heavy." I'd be 5 miles large behind 757, 6 for smalls on final. I could just say heavy in traffic calls, wake turbulence advisories, communications with terminal facilities when providing approach services, etc.

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