Skywatch From United States of America, joined Mar 2005, 922 posts, RR: 6 Posted (7 years 2 months 3 weeks 21 hours ago) and read 4835 times:
I have heard some educated guesses, but have never had a sure answer about what makes an aircraft a Heavy? Is it weight, fluid displacement, ect....
If it is weight, is it based on empty weight or total payload weight? If it is based on payload weight, can an aircraft take off of the runway as a heavy
and land without the heavy status because of burned fuel?
KYIPpilot From United States of America, joined Oct 2003, 1383 posts, RR: 9 Reply 1, posted (7 years 2 months 3 weeks 21 hours ago) and read 4811 times:
It is considered heavy if its max gross weight is 255,000 thousand lbs or greater.
It can still be called heavy even if it isn't at that weight for the actual flight. It goes by max certified weight, not weight per flight.
757's fall under "heavies", as well as all widebodies.
[Edited 2005-03-08 03:56:16]
"It starts when you're always afraid; You step out of line, the man come and take you away" -Buffalo Springfield
Klaus From Germany, joined Jul 2001, 20147 posts, RR: 57 Reply 4, posted (7 years 2 months 3 weeks 20 hours ago) and read 4787 times:
Skywatch: I have not heard 757's refered to as heavies. Are you sure? Also, is a DC-8 a heavy?
It was discovered that the 757 produces much stronger wake turbulence than other narrowbody aircraft, so it enforces separation distances comparable to "heavy" widebodies. It´s a special exemption primarily due to aerodynamic effects, not actual weight.
QantasA332 From Australia, joined Dec 2003, 1500 posts, RR: 41 Reply 8, posted (7 years 2 months 3 weeks 18 hours ago) and read 4684 times:
Quoting 2H4 (reply 5): Think the upcoming winglets on 757's will alleviate that wake turbulence, or is it mainly a result of the trailing edge flap configuration?
Keep in mind that a large portion of winglet operation is the production of thrust through a forward vectoring of the resultant freestream-vortex flow at the wingtips, an effect which doesn't relate directly to wake turbulence strength at all. The reduction of vortex strength is the other (sometimes smaller) part of winglet operation, which does affect wake strength, but it is probably not major enough to significantly reduce the 757's wake turbulence strength. Having said that, the main source of the 757's disproportionately strong wake is indeed its general wing-flap geometry (as Klaus correctly stated), anyway, so with that in mind winglets would have an even smaller overall effect on the wake strength.
Whether the 757's wake really is so grossly out of proportion to its size and weight is another much-debated question...
WakeTurbulence From United States of America, joined Apr 2004, 1279 posts, RR: 21 Reply 9, posted (7 years 2 months 3 weeks 16 hours ago) and read 4663 times:
I have heard in this forum that UA also has or had some 752's that qualify as heavies over 255,000 lbs, in addition to ATA. I agree with Qantas332 that winglets won't reduce the 752's wake that much. I have read winglets help reduce it, but by minimal amounts.
Quoting QantasA332 (reply 8): Whether the 757's wake really is so grossly out of proportion to its size and weight is another much-debated question...
In 1993 a 757 caused a private jet to crash with the founder of In N Out on board during final to SNA, killing all on board. Separation was a key factor, but so was the 752's wake.
-Matt
Skywatch From United States of America, joined Mar 2005, 922 posts, RR: 6 Reply 11, posted (7 years 2 months 3 weeks 11 hours ago) and read 4601 times:
Does the aircraft's payload weight increase wake turbulence, or is that solely caused by the size of the aircraft and the shape of it?
Starlionblue From Greenland, joined Feb 2004, 15105 posts, RR: 69 Reply 13, posted (7 years 2 months 3 weeks 9 hours ago) and read 4576 times:
Does the aircraft's payload weight increase wake turbulence, or is that solely caused by the size of the aircraft and the shape of it?
One follows the other. While the shape, size and speed are the only direct effects on the strength of the wake, a heavier plane will have larger surfaces=more wake.
What are the Heavy's around presently.
Limiting myself to A and B currently in common use:
747
757-300
767
777
330
340
Tact Is For People Who Aren't Witty Enough To Be Sarcastic
Dw747400 From United States of America, joined Aug 2001, 1238 posts, RR: 1 Reply 14, posted (7 years 2 months 3 weeks 9 hours ago) and read 4573 times:
To add to Starlion's list,
Frequently spotted heavies (around here) can include:
A300
A310
DC-8 (normally only F's these days)
DC-10
MD-11
There are also several Russian airliners that are heavies which visit the US East Coast.
Geedo From United States of America, joined Feb 2004, 364 posts, RR: 0 Reply 16, posted (7 years 2 months 2 weeks 6 days 23 hours ago) and read 4489 times:
I often hear Paul Allen's ride flying out of PDX. The radio operator always calls themselves "7 alpha fox heavy". Its a 757.
Newark777 From United States of America, joined Dec 2004, 9348 posts, RR: 38 Reply 17, posted (7 years 2 months 2 weeks 6 days 23 hours ago) and read 4473 times:
Quoting Skywatch (Reply 11): Does the aircraft's payload weight increase wake turbulence, or is that solely caused by the size of the aircraft and the shape of it?
Thenoflyzone From Canada, joined Jan 2001, 1704 posts, RR: 11 Reply 18, posted (7 years 2 months 2 weeks 6 days 2 hours ago) and read 4375 times:
The B752 is considered a heavy when IN FRONT of another airliner, and a medium plane when BEHIND another airliner.
Therefore, you need 5 nautical miles separation when a 752 is following a heavy, but you need 4 nautical miles separation when the heavy is following the 752!
AK
us Air Traffic Controllers have a good record, we haven't left one up there yet !!
Skywatch From United States of America, joined Mar 2005, 922 posts, RR: 6 Reply 19, posted (7 years 2 months 2 weeks 5 days 19 hours ago) and read 4310 times:
I will ask yet again: Does the payload weight increase wake turbulence? Likewise, can, for example, 747A be full of pax, and 747B empty, and they still generate the same amount of wake turbulence?
2H4 From United States of America, joined Oct 2004, 8937 posts, RR: 65 Reply 20, posted (7 years 2 months 2 weeks 5 days 19 hours ago) and read 4306 times:
AIRLINERS.NET CREW HEAD DATABASE EDITOR
Quoting Skywatch (Reply 19): I will ask yet again: Does the payload weight increase wake turbulence? Likewise, can, for example, 747A be full of pax, and 747B empty, and they still generate the same amount of wake turbulence?
No. The heavier an aircraft is, the more lift it has to produce to remain airborne. The more lift it produces, the stronger the wingtip vorticies become. Stronger wingtip vorticies create stronger wake turbulence.
The only part I'm not totally clear on is how the trailing-edge flap design contributes to the wake turbulence. Perhaps someone more knowledgeable than myself can explain things further.
Sprout5199 From United States of America, joined Feb 2005, 1673 posts, RR: 2 Reply 21, posted (7 years 2 months 2 weeks 5 days 18 hours ago) and read 4301 times:
Skywatch From United States of America, joined Mar 2005, 922 posts, RR: 6 Reply 22, posted (7 years 2 months 2 weeks 5 days 7 hours ago) and read 4260 times:
2H4: Flaps generate wake turbulence by a process called the Bernoulli Principle. This can be defined as "the sideward pressure exerted by a moving fluid decreases as the fluid's velocity increases." This is the reason for the airfoil design on wings. The reason this produces lift is because the air traveling over the top of the wing has to travel faster than the air on the bottom of the wing to meet up with the air from the bottom side of the wing. If you add flaps to this, you can imagine how this would upset this process. Lots of miniature vortices resembling whirlpools are formed, causing the extra wake. And, the faster it is going, with the given degrees of flaps, the more wake turbulence there will be.
Skywatch From United States of America, joined Mar 2005, 922 posts, RR: 6 Reply 23, posted (7 years 2 months 2 weeks 4 days 19 hours ago) and read 4190 times:
Wait a minute everyone! I looked up some stats on the 757 and 767, and their gross empty weights are below 255,000 lbs by a long shot! So what is the real weight criteria for a heavy? It can't be 255,000lbs! Or does that MGTOW mean something that I don't know about?
Newark777 From United States of America, joined Dec 2004, 9348 posts, RR: 38 Reply 24, posted (7 years 2 months 2 weeks 4 days 19 hours ago) and read 4182 times:
Quoting Skywatch (Reply 23): Wait a minute everyone! I looked up some stats on the 757 and 767, and their gross empty weights are below 255,000 lbs by a long shot! So what is the real weight criteria for a heavy? It can't be 255,000lbs! Or does that MGTOW mean something that I don't know about?
I'm pretty sure MGTOW stands for Maximum Gross Take Off Weight, which is quite different than empty weight.
Harry
Why grab a Heine when you can grab a Busch?
25 OPNLguy: In the begining, a "heavy" was defined as any aircraft that was capable of a max gross takeoff weight MGTOW) of 300,000 lbs. or more, irrespective of
26 Bri2k1: Please do a thorough search of this forum before posting anything like "the air has to travel faster to meet up with the air on the bottom." Air is no
27 Skywatch: Would some 752's have greater takeoff capacities than other 752's because of different engine manufacturers?
28 OPNLguy: >>>Would some 752's have greater takeoff capacities than other 752's because of different engine manufacturers? Can't say, as I'm not familar with tho
29 Starlionblue: As Bri2k1 says, this explanation for lift is flawed. Try this instead (keep reading a few pages on): http://travel.howstuffworks.com/airplane3.htm
30 CRJ200Mechanic: Okay that article just threw everything I learned in school out the window.
31 Skywatch: What the article said is basically what I had in mind, but I did not want to type that much! Thanks for keeping me in check.
32 Sprout5199: Same here. I guess its just PFM. (pure F$%king magic) Dan in Jupiter
33 Starlionblue: Yes, for example AAs RB211 powered 752s have higher MTOW than the Pratt powered ones. Isn't life fun
34 Bri2k1: It IS fun. Flying requires faith, because you certainly can't "see" lift - just it's effects. Humans don't necessarily understand every single thing a
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