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Why No Winglet On Horizontal Stabilizer?  
User currently offlineA380900 From France, joined Dec 2003, 1118 posts, RR: 1
Posted (1 year 6 months 2 weeks 3 days 9 hours ago) and read 5656 times:

Obvious reply is, I guess, that the cost outweigh the benefits but now these winglets are well understood and cannot be that costly. So since for the A380 for instance, the "wingspan" of the horizontal stabilizer is as big as a 737 wing, why not put some winglet on?

26 replies: All unread, showing first 25:
 
User currently offlineA380900 From France, joined Dec 2003, 1118 posts, RR: 1
Reply 1, posted (1 year 6 months 2 weeks 3 days 7 hours ago) and read 5605 times:

Well, now that I think of it, I guess you want this part of the plane to take positive and negative loads so you want it to be symmetric or something like that...

User currently offlineKlaus From Germany, joined Jul 2001, 21521 posts, RR: 53
Reply 2, posted (1 year 6 months 2 weeks 3 days 7 hours ago) and read 5605 times:

As far as I'm aware, winglets or related wingtip devices are largely a second-best option relative to just extending the wing span as far as desired, which is not always possible due to airport operational restrictions. That restriction doesn't apply to the stabilizer, so it's just extended as far as needed without any added complexity.

User currently offlineRoseflyer From United States of America, joined Feb 2004, 9817 posts, RR: 52
Reply 3, posted (1 year 6 months 2 weeks 3 days 4 hours ago) and read 5468 times:

Winglets are used to reduce lift-induced drag. The horizontal stabilizer is not a lifting surface on most conventional airplanes. In cruise, the horizontal stabilizer is not producing significant wingtip vorticies. Therefore, winglets wouldn’t help. With proper CG constraints, the horizontal stabilizer produces very little force in cruise. The horizontal stabilizer produces significant force on climb and some force on landing, but that is not enough to justify winglets.

[Edited 2013-06-06 13:50:56]


If you have never designed an airplane part before, let the real designers do the work!
User currently offlinesaafnav From South Africa, joined Mar 2010, 287 posts, RR: 1
Reply 4, posted (1 year 6 months 2 weeks 3 days 4 hours ago) and read 5459 times:

I might be off base this late at night, but isn't the vortices created by lift-dependent drag?
Thus, for most of the flight when the elevator is not creating lift, the advantages of having wing lets would be offset by the cost and complexity.



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User currently offlinerwessel From United States of America, joined Jan 2007, 2412 posts, RR: 2
Reply 5, posted (1 year 6 months 2 weeks 2 days 22 hours ago) and read 5327 times:
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Quoting Roseflyer (Reply 3):
Winglets are used to reduce lift-induced drag. The horizontal stabilizer is not a lifting surface on most conventional airplanes.

On almost all conventional aircraft, the horizontal stabilizer produces a significant amount of lift - but downwards. Most aircraft have their CG ahead of the CP, and so need a firm shove down on the tail to keep the nose up.

A few aircraft have had trim tanks in the tail, which allowed the CG to be shifted aft during cruise, reducing the downforce the tail needs to produce.

That needed downforce is the prime reason people find forward horizontal stabilizers (canards) perpetually interesting, as the canard would need to produce upwards lift to keep the nose up (and thus be more efficient).

But the main reason you don't see winglets on horizontal stabs is as has been mentioned already: anything you can accomplish with a winglet, you can do better with an increase in span. And the width of the horizontal stabilizers is simply not an issue in most cases, given that they're following, by a few dozens of feet, the much wider wing.


User currently offlineSkydrol From Canada, joined Oct 2003, 983 posts, RR: 10
Reply 6, posted (1 year 6 months 2 weeks 2 days 21 hours ago) and read 5309 times:

It has been done...


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On B1900D the horizontal stabilizer winglets are called 'toilets'. Have no idea if their benefit significantly overcomes their added weight, especially on the short-haul flights the B1900D is used. Of course the B1900D has almost every type of fin in existence anyway... so why not have some on the h-stab too?




LD4



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User currently offlineN243NW From United States of America, joined Jul 2003, 1640 posts, RR: 20
Reply 7, posted (1 year 6 months 2 weeks 2 days 21 hours ago) and read 5287 times:

Quoting Skydrol (Reply 6):
Have no idea if their benefit significantly overcomes their added weight, especially on the short-haul flights the B1900D is used.

I did a search and according to a different A.net post some 13 years ago, the tail-lets ("toilets"?) were added to lower Vmca (minimum control airspeed with an engine failure) rather than increase efficiency. Presumably these devices produce a keel effect that in essence increases the overall area of the vertical stabilizer.

Another reason the 1900D is one of the ugliest aircraft plying the skies today...  



B-52s don't take off. They scare the ground away.
User currently offlineSkydrol From Canada, joined Oct 2003, 983 posts, RR: 10
Reply 8, posted (1 year 6 months 2 weeks 2 days 20 hours ago) and read 5274 times:

Quoting N243NW (Reply 7):
tail-lets ("toilets"?)

How dare Microsoft's spellcheck not recognize ''tailets''! At least it got one thing right with ''toilets'': they're both at the back of the plane.  


Quoting N243NW (Reply 7):
Another reason the 1900D is one of the ugliest aircraft plying the skies today...

Looks strange, but fun to fly in.




LD4



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User currently offlineKELPkid From United States of America, joined Nov 2005, 6428 posts, RR: 3
Reply 9, posted (1 year 6 months 2 weeks 2 days 19 hours ago) and read 5256 times:

NASA tried it:


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  Apparently, with some succes...   Although I'm not sure exactly why...I don't think it was to decrease induced drag produced by the horizontal stab. Probably because the tail needed more vertical area to do the job (just like the taillets on the Beech 1900D...).



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User currently offlineStarlionblue From Greenland, joined Feb 2004, 17173 posts, RR: 66
Reply 10, posted (1 year 6 months 2 weeks 2 days 18 hours ago) and read 5241 times:

As mentioned, the purpose of winglets is to reduce drag. The horizontal stabilizer produces downward lift, but given the relatively small amount of that lift winglets on the stabilizer are not worth the extra weight.

The surfaces on the Beech 1900 and the Shuttle Sransporter are for stability/control and not for drag reduction. In the case of the Shuttle Transporter the Shuttle masked the vertical fin so the additional surfaces were needed to ensure stability. On the Beech 1900 you can see that it also has a large ventral fin for the purpose.



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlinebohica From United States of America, joined Feb 2004, 2749 posts, RR: 0
Reply 11, posted (1 year 6 months 2 weeks 2 days 18 hours ago) and read 5238 times:

Quoting Skydrol (Reply 6):
Of course the B1900D has almost every type of fin in existence anyway... so why not have some on the h-stab too?

All those fins on a 1900D was the result of having a taller fuselage as opposed to the 1900C. That way they didn't have to enlarge the horizontal and vertical stabilizers. Yes, it's fugly.

Quoting KELPkid (Reply 9):
NASA tried it:

The space shuttle on top of the 747 created a lot of turbulent air on the 747's vertical stabilizer. The fins on the horizontal stabilizer were meant to keep the 747 stable when the space shuttle was mounted on top.


User currently offlineMir From United States of America, joined Jan 2004, 21864 posts, RR: 55
Reply 12, posted (1 year 6 months 2 weeks 2 days 17 hours ago) and read 5210 times:

I'd have to imagine that putting winglets on the horizontal stabilizer might create some tailstrike risk, since they'd be pointing downward.

-Mir



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User currently offlineCitationJet From United States of America, joined Mar 2003, 2469 posts, RR: 3
Reply 13, posted (1 year 6 months 2 weeks 2 days 11 hours ago) and read 5076 times:

I think most HTs have a symmetrical airfoil, so winglets don't make much sense. The 747 shuttle carrier's are for directional stability, due to the large "blob" sitting on top of the aircraft that increases the area ahead of the CG.


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User currently offlinerwessel From United States of America, joined Jan 2007, 2412 posts, RR: 2
Reply 14, posted (1 year 6 months 2 weeks 2 days 10 hours ago) and read 5043 times:
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Quoting bohica (Reply 11):
The space shuttle on top of the 747 created a lot of turbulent air on the 747's vertical stabilizer. The fins on the horizontal stabilizer were meant to keep the 747 stable when the space shuttle was mounted on top.

The Soviet's replaced the conventional vertical stabilizer of the An-124 with an H-tail when they stretched it into the An-225, for the same reason.

Quoting Mir (Reply 12):
I'd have to imagine that putting winglets on the horizontal stabilizer might create some tailstrike risk, since they'd be pointing downward.

Winglets don't have to be pointed "up" (in the direction the airfoil is lifting), they just need to be in the rotational flow off the end of the wing.


User currently offlineGAIsweetGAI From Norway, joined Jul 2006, 934 posts, RR: 7
Reply 15, posted (1 year 6 months 1 week 6 days 17 hours ago) and read 4646 times:

Quoting Skydrol (Reply 6):
It has been done...

Also:

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"There is an art, or rather a knack to flying. The knack lies in learning how to throw yourself at the ground and miss."
User currently offlineStarlionblue From Greenland, joined Feb 2004, 17173 posts, RR: 66
Reply 16, posted (1 year 6 months 1 week 6 days 15 hours ago) and read 4609 times:

The Liberator doesn't have winglets. Those are fins and rudders.


"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlineGAIsweetGAI From Norway, joined Jul 2006, 934 posts, RR: 7
Reply 17, posted (1 year 6 months 1 week 6 days ago) and read 4428 times:

Quoting Starlionblue (Reply 16):

Indeed, but the airflow doesn't really care what they're called... To it, they're just another pair of things that damp vortices.



"There is an art, or rather a knack to flying. The knack lies in learning how to throw yourself at the ground and miss."
User currently offlineStarlionblue From Greenland, joined Feb 2004, 17173 posts, RR: 66
Reply 18, posted (1 year 6 months 1 week 6 days ago) and read 4410 times:

Quoting GAIsweetGAI (Reply 17):
Quoting Starlionblue (Reply 16):

Indeed, but the airflow doesn't really care what they're called... To it, they're just another pair of things that damp vortices.

Well.  

In my opinion winglets are defined as devices whose primary purpose is to damp vortices, wihle fins are devices whose primary purpose is to provide longitudinal stability.



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlineBMI727 From United States of America, joined Feb 2009, 15831 posts, RR: 27
Reply 19, posted (1 year 6 months 1 week 5 days 21 hours ago) and read 4362 times:

Quoting KELPkid (Reply 9):
Probably because the tail needed more vertical area to do the job (just like the taillets on the Beech 1900D...).

   As far as I know such things have only ever been used for lateral stability.



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User currently offlineSSTeve From United States of America, joined Dec 2011, 733 posts, RR: 2
Reply 20, posted (1 year 6 months 1 week 5 days 20 hours ago) and read 4354 times:

Quoting rwessel (Reply 5):
That needed downforce is the prime reason people find forward horizontal stabilizers (canards) perpetually interesting, as the canard would need to produce upwards lift to keep the nose up (and thus be more efficient).

So canards could find use for winglets?

Bring on the mustachioed airplanes.


User currently offlinePC12Fan From United States of America, joined Jan 2007, 2466 posts, RR: 5
Reply 21, posted (1 year 6 months 1 week 5 days 9 hours ago) and read 4261 times:

Quoting bohica (Reply 11):
Quoting KELPkid (Reply 9):
NASA tried it:

The space shuttle on top of the 747 created a lot of turbulent air on the 747's vertical stabilizer. The fins on the horizontal stabilizer were meant to keep the 747 stable when the space shuttle was mounted on top.

A little tongue and cheek response there.

IIRC, another big reason for the SCA tail configuration was a "safety backup" during the shuttle drop tests. Initially, the NASA folks weren't sure how the shuttle would behave after separation. They were afraid the shuttle would go directly back into the vertical stabilizer. The additional surfaces would act as the backup in case the unthinkable happened.



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User currently offlineGAIsweetGAI From Norway, joined Jul 2006, 934 posts, RR: 7
Reply 22, posted (1 year 6 months 1 week 5 days 6 hours ago) and read 4195 times:

Quoting Starlionblue (Reply 18):
In my opinion winglets are defined as devices whose primary purpose is to damp vortices, wihle fins are devices whose primary purpose is to provide longitudinal stability.

Eh, fair enough - I usually consider any end plates to fit under the definition of winglets, simply because they damp wingtip vortices.

On a related note, does anyone know why the B-24 design team went for twin vertical stabs? (Survivability, tail volume, 3D drag, or something else?)



"There is an art, or rather a knack to flying. The knack lies in learning how to throw yourself at the ground and miss."
User currently offlineairmagnac From Germany, joined Apr 2012, 321 posts, RR: 52
Reply 23, posted (1 year 6 months 1 week 5 days 5 hours ago) and read 4167 times:

Quoting GAIsweetGAI (Reply 22):
any end plates to fit under the definition of winglets, simply because they damp wingtip vortices.

I guess that's a reasonable definition ; but I'd agree with Starlionblue, maybe it's better to define winglets as devices which were specifically designed for the purpose of reducing drag due to tip vortices, and not count devices which just happened to be located on wing tips for some reason(s).
I'm not even sure the overall drag was reduced by the fins of the B24 by any measurable amount

Quoting GAIsweetGAI (Reply 22):
does anyone know why the B-24 design team went for twin vertical stabs?

**Speculation alert**  

Could be something to do with minimising yaw effects due to the propeller slipstreams affecting the vertical stab.

And/or a way to reduce the fin heights, to fit the aircraft into hangars. The B24 fuselage was rather bulky and short, which would require a large vertical surface. Also, the Liberator had a nose landing gear, so the aft section would already be higher than that of a plane with a tail wheel, like the B17 (which had a relatively huge tail in its E/F/G versions). I think that was one of the reasons for the triple-tail of the Constellation (or so I was told when I worked at the Smithsonian).
It may also have been a useful in combat, presenting smaller targets and providing redundancy



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User currently offlinerwessel From United States of America, joined Jan 2007, 2412 posts, RR: 2
Reply 24, posted (1 year 6 months 1 week 4 days 23 hours ago) and read 4110 times:
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Quoting SSTeve (Reply 20):
So canards could find use for winglets?

Bring on the mustachioed airplanes.

Aerodynamically not really any more or less than a conventional (rear) horizontal stabilizer. Just because one lifts up, and the other lifts down doesn't really change the nature of the wingtip vortices (except in direction, of course). In practical terms, canards have issues because the h-stab is now very inconveniently placed, both structurally (invariably they need to go through a very busy part of the airplane - the tail section, by comparison, is mostly empty), and in terms of ground handling (just think, you now have to snake the air bridge around the canard). Perhaps the later case might lead to a use of winglets on a shorter than ideal canard as a compromise. Although the darn thing is still going to be very much in the way.


25 GAIsweetGAI : Indeed, it probably increased drag. But the vertical stab *is* in the propeller slipstream, pretty much... Hadn't thought of it, and it does make qui
26 Post contains links and images moriarty : *lets On Tailplane? (by moriarty Nov 23 2012 in Tech Ops)
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