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Why No Wing Fences On Tailplanes?  
User currently offlineFaro From Egypt, joined Aug 2007, 1620 posts, RR: 0
Posted (6 years 11 months 3 weeks 3 days 22 hours ago) and read 4159 times:

Admittedly winglets would seem to be too heavy for horizonal stabilisers, but what about fences or raiked wingtips? Would they make economic sense on some of the bigger widebodies?

Faro


The chalice not my son
19 replies: All unread, jump to last
 
User currently offlineHAWK21M From India, joined Jan 2001, 31712 posts, RR: 56
Reply 1, posted (6 years 11 months 3 weeks 3 days 21 hours ago) and read 4136 times:

Would the 1900D qualify.
regds
MEL



Think of the brighter side!
User currently offlineOldAeroGuy From United States of America, joined Dec 2004, 3598 posts, RR: 66
Reply 2, posted (6 years 11 months 3 weeks 3 days 20 hours ago) and read 4107 times:

The point of tip devices is to reduce induced drag due to lift. Horizontal tail lift loads are usually rather low in cruise, slightly up, slightly down or zero. Therefore there isn't much h. tail induced drag to reduce.

Since h. tail induced drag improvement potential is low, I doubt the improvement would overcome the form drag and weight penalties that adding h. tail tip devices would entail.

[Edited 2008-01-03 12:18:34]


Airplane design is easy, the difficulty is getting them to fly - Barnes Wallis
User currently offlineTdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 3, posted (6 years 11 months 3 weeks 3 days 19 hours ago) and read 4095 times:



Quoting Faro (Thread starter):
Admittedly winglets would seem to be too heavy for horizonal stabilisers, but what about fences or raiked wingtips? Would they make economic sense on some of the bigger widebodies?

In addition to what OldAeroGuy said, which I agree with, why wouldn't you just expand the span? The horizontal stab isn't span limited and increasing span is the most efficient way to reduce induced drag. That's why you see gliders with huge spans, not winglets.

Tom.


User currently offlineJRadier From Netherlands, joined Sep 2004, 4722 posts, RR: 50
Reply 4, posted (6 years 11 months 3 weeks 3 days 17 hours ago) and read 4052 times:



Quoting Tdscanuck (Reply 3):
That's why you see gliders with huge spans, not winglets.

Plenty of gliders out there with winglets, from the raked wingtips on the Duo Discus

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Photo © Phil Vabre


to full winglets on the Discus B and DG-808 (and plenty of others).

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Photo © Andrei Bezmylov
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Photo © Michael Priesch - Spotterteam Graz




For once you have tasted flight you will walk the earth with your eyes turned skywards, for there you have been and ther
User currently offlineKELPkid From United States of America, joined Nov 2005, 6428 posts, RR: 3
Reply 5, posted (6 years 11 months 3 weeks 3 days 17 hours ago) and read 4038 times:

So sure about that?

How about this guy:


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Photo © Mike Freer - Touchdown-aviation

 Big grin

Sea planes seem to have fences on the tail plane, too:


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Photo © Parr Yonemoto

 Wink



Celebrating the birth of KELPkidJR on August 5, 2009 :-)
User currently offlineOldAeroGuy From United States of America, joined Dec 2004, 3598 posts, RR: 66
Reply 6, posted (6 years 11 months 3 weeks 3 days 16 hours ago) and read 4025 times:



Quoting KELPkid (Reply 5):
How about this guy:



Quoting KELPkid (Reply 5):
Sea planes seem to have fences on the tail plane, too:

Directional stability band-aids.



Airplane design is easy, the difficulty is getting them to fly - Barnes Wallis
User currently offline2H4 From United States of America, joined Oct 2004, 8956 posts, RR: 60
Reply 7, posted (6 years 11 months 3 weeks 3 days 16 hours ago) and read 4020 times:
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Quoting OldAeroGuy (Reply 2):

So why have winglets never been installed on canards? I'm thinking of the Starship, Avanti, etc. Heck, even homebuilts.

The combination of being highly-loaded and short in span seems to make them ideal candidates for winglets.

2H4



Intentionally Left Blank
User currently offlineOldAeroGuy From United States of America, joined Dec 2004, 3598 posts, RR: 66
Reply 8, posted (6 years 11 months 3 weeks 3 days 16 hours ago) and read 4006 times:



Quoting 2H4 (Reply 7):
So why have winglets never been installed on canards? I'm thinking of the Starship, Avanti, etc. Heck, even homebuilts.

The combination of being highly-loaded and short in span seems to make them ideal candidates for winglets.

Tdscanuck has the correct answer.

Quoting Tdscanuck (Reply 3):
In addition to what OldAeroGuy said, which I agree with, why wouldn't you just expand the span?

With the exception of the VariViggen, all the modern canards (fighters not included) I can think of are already high aspect ratio with relatively high spans in an attempt to minimize their induced drag. Besides, adding winglets to a canard would force you to add more wetted area to the v. tail and/or wing winglets to recover directional stability.

Sounds like a poor trade to me.



Airplane design is easy, the difficulty is getting them to fly - Barnes Wallis
User currently offline2H4 From United States of America, joined Oct 2004, 8956 posts, RR: 60
Reply 9, posted (6 years 11 months 3 weeks 3 days 15 hours ago) and read 3998 times:
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Quoting OldAeroGuy (Reply 8):
all the modern canards (fighters not included) I can think of are already high aspect ratio with relatively high spans in an attempt to minimize their induced drag. Besides, adding winglets to a canard would force you to add more wetted area to the v. tail and/or wing winglets to recover directional stability.

Interesting points. Thanks for the input.

2H4



Intentionally Left Blank
User currently offlineTdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 10, posted (6 years 11 months 3 weeks 2 days 22 hours ago) and read 3889 times:



Quoting JRadier (Reply 4):

Plenty of gliders out there with winglets, from the raked wingtips on the Duo Discus

A raked wingtip is a span extension...that was my point.

Quoting JRadier (Reply 4):

to full winglets on the Discus B and DG-808 (and plenty of others).

Now that's interesting...I'm a bit stumped as to the aerodynamic reasoning behind that. Are there situations were a glider is span limited?

Tom.


User currently offlineKELPkid From United States of America, joined Nov 2005, 6428 posts, RR: 3
Reply 11, posted (6 years 11 months 3 weeks 2 days 22 hours ago) and read 3880 times:



Quoting HAWK21M (Reply 1):
Would the 1900D qualify.

MEL, in the Beech 1900D's case, the "winglets" on the tail are there specifically to give the aircraft enough vertical stabilizer area...this was done so that a stock Beechcraft King Air 350 tail could be used and save lots of money on production costs (of course, as we all know, it's not quite stock when you have to hang "taillets" of the horizontal stab...  Wink ).



Celebrating the birth of KELPkidJR on August 5, 2009 :-)
User currently offlineHAWK21M From India, joined Jan 2001, 31712 posts, RR: 56
Reply 12, posted (6 years 11 months 3 weeks 2 days 20 hours ago) and read 3837 times:



Quoting KELPkid (Reply 11):
the Beech 1900D's case, the "winglets" on the tail are there specifically to give the aircraft enough vertical stabilizer area...this was done so that a stock Beechcraft King Air 350 tail could be used and save lots of money on production costs

Thats Educational.Never knew that.Thanks.
regds
MEL



Think of the brighter side!
User currently offlineRwessel From United States of America, joined Jan 2007, 2412 posts, RR: 2
Reply 13, posted (6 years 11 months 3 weeks 2 days 16 hours ago) and read 3786 times:
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Quoting Tdscanuck (Reply 10):
Now that's interesting...I'm a bit stumped as to the aerodynamic reasoning behind that. Are there situations were a glider is span limited?

Absolutely. Any glider hoping to compete in a 15m or 18m class, for example. Probably a significant majority of single seat gliders being built have 15m wings. Those with flaps can compete in the 15m class, those without flaps can compete in the standard class (which still has a 15m wingspan limit).

There's also a 20m class for two-seaters, several one design classes (formal and otherwise), an Open class, and a couple of handicapped classes.


User currently offlineTdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 14, posted (6 years 11 months 3 weeks 2 days 15 hours ago) and read 3772 times:



Quoting Rwessel (Reply 13):

Quoting Tdscanuck (Reply 10):
Now that's interesting...I'm a bit stumped as to the aerodynamic reasoning behind that. Are there situations were a glider is span limited?

Absolutely. Any glider hoping to compete in a 15m or 18m class, for example. Probably a significant majority of single seat gliders being built have 15m wings.

Fascinating! I had no idea (gliders aren't really my area of expertise, as I'm aptly demonstrating). This explains winglets on gliders perfectly...the canonical case for winglets is to reduce drag when you're span-restricted.

Tom.


User currently offlineRwessel From United States of America, joined Jan 2007, 2412 posts, RR: 2
Reply 15, posted (6 years 11 months 3 weeks 2 days 14 hours ago) and read 3760 times:
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Quoting Tdscanuck (Reply 14):
Fascinating! I had no idea (gliders aren't really my area of expertise, as I'm aptly demonstrating). This explains winglets on gliders perfectly...the canonical case for winglets is to reduce drag when you're span-restricted.

Somewhat off topic historical tidbit:

The desire for a bit more span caused quite a ruckus in the late eighties and early nineties. Before the rules were tightened up, there was a period when a large number of new composite designs with very flexible wings were first being introduced. A few builders tried to take advantage of the lack of precision and measured 15m (or whatever) for the glider in level flight (IOW, with the wings supporting 1G worth of glider), with a significant upwards bend in the wings.

Endless acrimonious debate arose over whether "15m" did, or did not, include the actions of a pair of burly wing benders.

Interestingly the rules took a bit of a compromise that did not disqualify the milder offenders (which included the vast majority of offending gliders). The nominal wingspan is now calculated with the wings in the zero G position (which means you can use stands to lift up the wing enough to make it match that shape), and you have an inch (2.5cm) of slack.


User currently offlineDEVILFISH From Philippines, joined Jan 2006, 4952 posts, RR: 1
Reply 16, posted (6 years 11 months 3 weeks 2 days 12 hours ago) and read 3735 times:



Quoting OldAeroGuy (Reply 6):
Directional stability band-aids.



Quoting OldAeroGuy (Reply 8):
Besides, adding winglets to a canard would force you to add more wetted area to the v. tail and/or wing winglets to recover directional stability.

Quite interesting then that installation of the dish for the Hawkeye did not necessitate adding any more fins to the four stabs on the Greyhound's already crowded tail? Aren't those based on the same airframe?.....

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Quoting KELPkid (Reply 11):
the "winglets" on the tail are there specifically to give the aircraft enough vertical stabilizer area..

And equally intriguing that small and very large aircraft such as these both required (only) two proportionally sized vert stabs.....

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"Everyone is entitled to my opinion." - Garfield
User currently offlineOldAeroGuy From United States of America, joined Dec 2004, 3598 posts, RR: 66
Reply 17, posted (6 years 11 months 3 weeks 1 day 20 hours ago) and read 3689 times:

Quoting DEVILFISH (Reply 16):
Quoting OldAeroGuy (Reply 8):
Besides, adding winglets to a canard would force you to add more wetted area to the v. tail and/or wing winglets to recover directional stability.

Quite interesting then that installation of the dish for the Hawkeye did not necessitate adding any more fins to the four stabs on the Greyhound's already crowded tail? Aren't those based on the same airframe?.....

And neither did the E-3A when the radome was added to the 707-320BAdv/C.

http://www.airliners.net/open.file?i...hoto_nr=1&prev_id=&next_id=1314053

http://www.airliners.net/open.file?i...=6&prev_id=1313315&next_id=1312820

The reason appears to be the same in both cases. The center of pressure (CP) of the radome and its supports appears to be at or aft airplane CG, thus the radome and its mounting would have a neutral impact on directional stability (Hawkeye) or might even improve it (E-3A).

Adding something like floats to a Beaver requires additional v. tail area because the float CP is forward of the airplane CG. Compare a Beaver on floats to a Beaver on wheels.

http://www.airliners.net/open.file?i...=6&prev_id=1308841&next_id=1308103

http://www.airliners.net/open.file?i...11&prev_id=1305794&next_id=1304557

You now need the additional vertical area provided by the verticals at the tips of the h. tail.

Obvioulsy, adding winglets to a canard surface would cause their CP to be in front of airplane CG. Restoring directional stability would require additional v. tail area.


Finally, the An-225 and the 747 Space Shuttle Carrier point out a different issue.

For the 747 Space Shuttle Carrier, the wake of the Shuttle lowered dynamic pressure at the v. tail, reducing its effectiveness. The verticals on the h. tail were required to restore directional stability.

The An-225, with an extensive design change, avoided the Buran wake issue by moving the v. tails out of the Buran wake.

[Edited 2008-01-05 11:56:43]


Airplane design is easy, the difficulty is getting them to fly - Barnes Wallis
User currently offlineMir From United States of America, joined Jan 2004, 21865 posts, RR: 55
Reply 18, posted (6 years 11 months 3 weeks 1 day 13 hours ago) and read 3625 times:



Quoting DEVILFISH (Reply 16):
Quite interesting then that installation of the dish for the Hawkeye did not necessitate adding any more fins to the four stabs on the Greyhound's already crowded tail? Aren't those based on the same airframe?.....

Isn't one of those four stabs not necessary, but there because it would look wierd if they left it off?

-Mir



7 billion, one nation, imagination...it's a beautiful day
User currently offlineDEVILFISH From Philippines, joined Jan 2006, 4952 posts, RR: 1
Reply 19, posted (6 years 11 months 3 weeks 17 hours ago) and read 3546 times:



Quoting OldAeroGuy (Reply 17):

Thank you very much for the explanations. Much appreciated.



"Everyone is entitled to my opinion." - Garfield
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