Sponsor Message:
Aviation Technical / Operations Forum
My Starred Topics | Profile | New Topic | Forum Index | Help | Search 
If A Heavy Aircraft Has Winglets..  
User currently offlineLASOctoberB6 From Japan, joined Nov 2006, 2380 posts, RR: 1
Posted (6 years 5 months 4 days 8 hours ago) and read 2723 times:

A 757 for example, if it is equipped with winglets, then when a smaller aircraft like a 737 is holding position after the 757 takes off, does it have to wait as long for takeoff clearance as it would if the 757 wasn't equipped with winglets?


[NOT IN SERVICE] {WEStJet}
11 replies: All unread, jump to last
 
User currently offline2H4 From United States of America, joined Oct 2004, 8955 posts, RR: 60
Reply 1, posted (6 years 5 months 4 days 8 hours ago) and read 2716 times:
AIRLINERS.NET CREW
DATABASE EDITOR

Winglets don't necessarily reduce an aircraft's wake turbulence. Much (most?) of the 757s wake turbulence is a result of vorticies spilling off the outside trailing edges of the flaps.

2H4



Intentionally Left Blank
User currently offlineLASOctoberB6 From Japan, joined Nov 2006, 2380 posts, RR: 1
Reply 2, posted (6 years 5 months 4 days 8 hours ago) and read 2713 times:



Quoting 2H4 (Reply 1):
Winglets don't necessarily reduce an aircraft's wake turbulence. Much (most?) of the 757s wake turbulence is a result of vorticies spilling off the outside trailing edges of the flaps.

Ahh, okay. I thought it was the edge of the wing that created the vorticies..



[NOT IN SERVICE] {WEStJet}
User currently offline2H4 From United States of America, joined Oct 2004, 8955 posts, RR: 60
Reply 3, posted (6 years 5 months 4 days 8 hours ago) and read 2709 times:
AIRLINERS.NET CREW
DATABASE EDITOR



Quoting LASOctoberB6 (Reply 2):
Ahh, okay. I thought it was the edge of the wing that created the vorticies..

The wingtips do indeed create vorticies, but as I understand it (and I'll gladly stand corrected), those vorticies are not necessarily the ones that create the biggest hazard for following aircraft.

2H4



Intentionally Left Blank
User currently offline2H4 From United States of America, joined Oct 2004, 8955 posts, RR: 60
Reply 4, posted (6 years 5 months 4 days 8 hours ago) and read 2704 times:
AIRLINERS.NET CREW
DATABASE EDITOR

Here are some visual examples of what I'm talking about:

757:

View Large View Medium
Click here for bigger photo!

Photo © Steve Morris - AirTeamImages
View Large View Medium
Click here for bigger photo!

Photo © Steve Morris - AirTeamImages





MD-11:

View Large View Medium
Click here for bigger photo!

Photo © Tim de Groot - AirTeamImages



2H4



Intentionally Left Blank
User currently offlineLegoguy From United Kingdom, joined Jun 2006, 3313 posts, RR: 39
Reply 5, posted (6 years 5 months 4 days 7 hours ago) and read 2692 times:

Theoretically would little end plates on the edge of the flaps help reduce the vortices such as the wing tip fences on the a320?


Can you say 'Beer Can' without sounding like a Jamaican saying 'Bacon'?
User currently offlineSaab2000 From Switzerland, joined Jun 2001, 1610 posts, RR: 11
Reply 6, posted (6 years 5 months 4 days 7 hours ago) and read 2691 times:

Those are impressive pics!! I have on a couple of occasions flown through some wakes and I can assure anyone who cares that I don't mind that waiting period one bit. I take off in PHL a lot after heavies and know that these can be hazardous. ATC sometimes try to rush things, but I will normally add a few seconds after T/O clearance just for safety's sake.

Wake turbulence can be a real hazard, more than most people recognise.



smrtrthnu
User currently offline2H4 From United States of America, joined Oct 2004, 8955 posts, RR: 60
Reply 7, posted (6 years 5 months 4 days 7 hours ago) and read 2682 times:
AIRLINERS.NET CREW
DATABASE EDITOR



Quoting Legoguy (Reply 5):
Theoretically would little end plates on the edge of the flaps help reduce the vortices such as the wing tip fences on the a320?

I suspect so, but given the extra weight, expense, and (presumably) drag in flight, I don't think it warrants reducing wake for such a tiny fraction of the flight. I could very well be wrong, but that's my gut feeling.

2H4



Intentionally Left Blank
User currently offlineTdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 8, posted (6 years 5 months 3 days 20 hours ago) and read 2499 times:



Quoting Legoguy (Reply 5):
Theoretically would little end plates on the edge of the flaps help reduce the vortices such as the wing tip fences on the a320?

Yes, but little end plates will have a little effect. To have any real benefit, winglets need to be relatively large (a 737 winglet is about 6 feet tall).

On top of that, a flap is essentially a very low aspect ratio wing. It's got horrible induced drag characteristics but that's OK because it's main purpose in life is high lift, not high lift:drag ratio. I agree with 2H4...I can't see how the benefit would outweigh the cost.

Tom.


User currently offlineLASOctoberB6 From Japan, joined Nov 2006, 2380 posts, RR: 1
Reply 9, posted (6 years 5 months 2 days ago) and read 2285 times:

Why is it that the edge of the T/E flap creates the vortex and not so much as the wingtip?

Quoting 2H4 (Reply 4):
Here are some visual examples of what I'm talking about:

I knew what you were talking about from a memory of:

Quoting Saab2000 (Reply 6):
I take off in PHL

in line up for takeoff on US Airways in 2000. That was all I can really remember from that flight was seeing the vorticies from the landing aircraft. But thanks, 2H4, for your detailed answer and research for the pictures.



[NOT IN SERVICE] {WEStJet}
User currently offlineSpeedbird128 From Pitcairn Islands, joined Oct 2003, 1648 posts, RR: 2
Reply 10, posted (6 years 5 months 9 hours ago) and read 2126 times:



Quoting LASOctoberB6 (Reply 9):
Why is it that the edge of the T/E flap creates the vortex and not so much as the wingtip?

The flaps are what increase the lift of the wing, so it's only expected they also cause the vortices.



A306, A313, A319, A320, A321, A332, A343, A345, A346 A388, AC90, B06, B722, B732, B733, B735, B738, B744, B762, B772, B7
User currently offlinePrebennorholm From Denmark, joined Mar 2000, 6461 posts, RR: 54
Reply 11, posted (6 years 4 months 4 weeks ago) and read 1922 times:



Quoting LASOctoberB6 (Thread starter):
A 757 for example, if it is equipped with winglets, then when a smaller aircraft like a 737 is holding position after the 757 takes off, does it have to wait as long for takeoff clearance as it would if the 757 wasn't equipped with winglets?

In this thread two different things have been confused:

1. Wake turbulence

2. Wing tip (and flap end) vortices.

When a few hundred thousand lbs of a/c is airborne, then it is the result of enormous amounts of air being accelerated downwards over the entire wing span. Equal amounts of air will rise outside the wing span creating two enormous rotors in opposite direction. That is wake turbulence.

Wake turbulence is a function of weight and wing span. More weight = more powerful wake turbulence. Greater span = reduced wake intensity by spreading the energy over more air masses.

Tip vortices, or lift spills over the wing tip, are far less powerful and do not influence clearance distances. They are tiny rotors inside the huge wake rotor.

In addition: Winglets do not necessarily reduce the intensity of the tip vortices at take-off or landing. They are carefully shaped and angled to intercept the tip vortices at cruising speed and convert some of the vortex energy into forward thrust much like a sail on a sailboat. Their influence on the danger of wake turbulence at slow speed is negligible.

Incidentally, the best thing to reduce the intensity of wake turbulence is drooped ailerons. The reason is that they create a more even distribution of the lift over the entire wing span. It isn't much, but it is measurable. Even if drooped ailerons INCREASE the intensity of tip vortices.

Drooped ailerons also reshape the tip vortices in such a way that winglets, optimized for cruise conditions, become even more useless at slow speed.

Please notice that in the text above I wrote about winglets, not tip fences as seen on A320 and A380 planes. Tip fences are a slightly different story, even if the purpose is the same. They are way less efficient at cruising speed, but on the other hand they work at all speeds, also with drooped ailerons. But like winglets they don't reduce wake turbulence in any measurable way.



Always keep your number of landings equal to your number of take-offs, Preben Norholm
Top Of Page
Forum Index

Reply To This Topic If A Heavy Aircraft Has Winglets..
Username:
No username? Sign up now!
Password: 


Forgot Password? Be reminded.
Remember me on this computer (uses cookies)
  • Tech/Ops related posts only!
  • Not Tech/Ops related? Use the other forums
  • No adverts of any kind. This includes web pages.
  • No hostile language or criticizing of others.
  • Do not post copyright protected material.
  • Use relevant and describing topics.
  • Check if your post already been discussed.
  • Check your spelling!
  • DETAILED RULES
Add Images Add SmiliesPosting Help

Please check your spelling (press "Check Spelling" above)


Similar topics:More similar topics...
If An Aircraft Was Unable To De-pressurise... posted Sat Feb 25 2006 20:38:47 by TupolevTu154
Question For Heavy Aircraft Pilots posted Mon Dec 8 2003 13:04:57 by MCPILOT
What Happens If An Aircraft Over Flies 40,000? posted Tue Jun 3 2003 21:40:22 by Airmale
What Makes An Aircraft "Heavy"? posted Tue Mar 8 2005 03:42:56 by Skywatch
You Might Be An Aircraft Mechanic If: posted Mon Jan 26 2004 17:26:57 by Air2gxs
How Many Winglets Aircraft Does WN Have posted Mon Jan 26 2004 07:14:58 by Paulinbna
Has An Aircraft Just Ever Collapsed While Parked O posted Thu Jan 3 2002 03:01:59 by ATA L1011
Which Aircraft Type Has Carried The Most Pax? posted Fri Oct 5 2001 00:06:06 by DC10Tony
Changing Feel Of An Aircraft: Pilots Perspective? posted Mon Apr 28 2008 03:15:03 by Hypersonic
Heavy Twin Engine Aircraft posted Sun Apr 20 2008 18:08:20 by KC135TopBoom
You Might Be An Aircraft Mechanic If: posted Mon Jan 26 2004 17:26:57 by Air2gxs
How Many Winglets Aircraft Does WN Have posted Mon Jan 26 2004 07:14:58 by Paulinbna
Has An Aircraft Just Ever Collapsed While Parked O posted Thu Jan 3 2002 03:01:59 by ATA L1011
Which Aircraft Type Has Carried The Most Pax? posted Fri Oct 5 2001 00:06:06 by DC10Tony
CT-4 Aircraft Wings Refinement posted Mon May 12 2008 01:02:40 by SteveS
Beginner's Question - Aircraft's Economics posted Thu May 1 2008 18:28:30 by WunalaYann

Sponsor Message:
Printer friendly format