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?
1 KYIPpilot: 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 th
2 Skywatch: I have not heard 757's refered to as heavies. Are you sure? Also, is a DC-8 a heavy?
3 2H4: The 757-300 exceeds 255,000 lbs max gross weight, as do DC-8's. 2H4
4 Klaus: 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 w
5 2H4: Klaus, Think the upcoming winglets on 757's will alleviate that wake turbulence, or is it mainly a result of the trailing edge flap configuration? 2H4
6 Klaus: 2H4: Think the upcoming winglets on 757's will alleviate that wake turbulence, or is it mainly a result of the trailing edge flap configuration? I can
7 N766UA: We need to have a FAQ section for this particular question... Anything over 255,000 lbs MGTOW. ATA flies the only heavy 752s.
8 QantasA332: Keep in mind that a large portion of winglet operation is the production of thrust through a forward vectoring of the resultant freestream-vortex flo
9 WakeTurbulence: 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 tha
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.
OPNLguy From , joined Dec 1969, posts, RR: Reply 25, posted (7 years 2 months 2 weeks 4 days 19 hours ago) and read 4182 times:
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 whether the aircraft was actually loaded up to that weight. It was based upon what MGTOW the aircraft was -capable- of.
Later, the threshold was changed from 300,000 lbs. to 255,000 lbs.
In a nutshell,
-There are some 757-200s that have MGTOWs -below- 255,000 and are NOT considered "heavy" (officially).
-There are some 757-200s that have MGTOWs -above- 255,000 and ARE considered heavies.
-There is no way to tell (by looking) which 757-200 is <255,000 and which is >255,000. Some airlines may have some of each in their fleets.
-The 757-300 is definitely >255,000 and IS considered a heavy.
-For wake turbulence separation purposes, ATC treats ALL models of the 757 as heavies, whether they technically are or not. In FAA training manuals, they refer to "heavy aircraft/757" and the "757" in that statement refers to the <255,000 757-200s which are not tecnically heavies, but must still be treated as one.
-Occasionally, it's possible that a controller or crew might slip and inadvertently refer to a <255,000 757-200 as a "heavy" even though it technically isn't one. Anyone hearing this on a scanner (or UAL's channel 9) might then get the erroneous idea that a particular aircraft is a heavy when it might not be.
Bri2k1 From United States of America, joined Dec 2004, 988 posts, RR: 4 Reply 26, posted (7 years 2 months 2 weeks 4 days 19 hours ago) and read 4175 times:
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 not afraid of being lonely, and does nothing to meet other air in public places.
Skywatch From United States of America, joined Mar 2005, 922 posts, RR: 6 Reply 27, posted (7 years 2 months 2 weeks 4 days 19 hours ago) and read 4171 times:
Would some 752's have greater takeoff capacities than other 752's because of different engine manufacturers?
OPNLguy From , joined Dec 1969, posts, RR: Reply 28, posted (7 years 2 months 2 weeks 4 days 18 hours ago) and read 4165 times:
>>>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 those, but I guess it's possible.
Airlines can order different weight ratings/limits on the same aircraft type. For example, the old 737-200 ADV was available with MTOGWs of 115,000, 117,500, 119,500, and 124,500, and I think the corresponding engines were the JT8D-9, the -15, the -17, and the -17R. Some 737-300s are maxed at 130,000, and some are maxed at 135,000. It's all what one is willing to pay Boeing for...
Starlionblue From Greenland, joined Feb 2004, 15105 posts, RR: 69 Reply 29, posted (7 years 2 months 2 weeks 4 days 16 hours ago) and read 4158 times:
Quoting Skywatch (Reply 23): 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
CRJ200Mechanic From United States of America, joined Feb 2005, 204 posts, RR: 2 Reply 30, posted (7 years 2 months 2 weeks 4 days 15 hours ago) and read 4147 times:
Okay that article just threw everything I learned in school out the window.
Always remember the responsibilies you hold with an A&P license
Skywatch From United States of America, joined Mar 2005, 922 posts, RR: 6 Reply 31, posted (7 years 2 months 2 weeks 4 days 9 hours ago) and read 4129 times:
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.
Sprout5199 From United States of America, joined Feb 2005, 1673 posts, RR: 2 Reply 32, posted (7 years 2 months 2 weeks 4 days 1 hour ago) and read 4113 times:
Quoting CRJ200Mechanic (Reply 30): Okay that article just threw everything I learned in school out the window.
Same here. I guess its just PFM. (pure F$%king magic)
Bri2k1 From United States of America, joined Dec 2004, 988 posts, RR: 4 Reply 34, posted (7 years 2 months 2 weeks 3 days 8 hours ago) and read 4073 times:
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 about the world in which we live. It's sufficient to know there is lift, and essentially how to produce it.
Sir Isaac Newton, and Daniel Bernoulli (working from a theory of Leonhard Euler), have found ways to explain most of what we're seeing using math and science. But as you have seen, the conventional application of either of them fails to offer a 100% complete explanation for everything related to aerodynamic lift. We can change their application as our understanding improves, but what does that say about our understanding?
In fact, it was just a few years ago that scientists finally discovered how bees and birds are able to fly. The power-to-weight ratio required seemed to be far too great for the amount of energy a small bird or insect could store, but yet we see them flying all the time. Just like airplanes.
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