a380900
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Why No Winglet On Horizontal Stabilizer?

Thu Jun 06, 2013 4:02 pm

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?
 
a380900
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RE: Why No Winglet On Horizontal Stabilizer?

Thu Jun 06, 2013 5:26 pm

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...
 
Klaus
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RE: Why No Winglet On Horizontal Stabilizer?

Thu Jun 06, 2013 5:26 pm

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.
 
roseflyer
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RE: Why No Winglet On Horizontal Stabilizer?

Thu Jun 06, 2013 8:49 pm

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]
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SAAFNAV
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RE: Why No Winglet On Horizontal Stabilizer?

Thu Jun 06, 2013 8:55 pm

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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rwessel
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RE: Why No Winglet On Horizontal Stabilizer?

Fri Jun 07, 2013 2:57 am

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.
 
Skydrol
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RE: Why No Winglet On Horizontal Stabilizer?

Fri Jun 07, 2013 3:22 am

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?




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N243NW
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RE: Why No Winglet On Horizontal Stabilizer?

Fri Jun 07, 2013 4:06 am

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...  
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Skydrol
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RE: Why No Winglet On Horizontal Stabilizer?

Fri Jun 07, 2013 5:02 am

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.




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KELPkid
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RE: Why No Winglet On Horizontal Stabilizer?

Fri Jun 07, 2013 6:03 am

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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Starlionblue
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RE: Why No Winglet On Horizontal Stabilizer?

Fri Jun 07, 2013 6:27 am

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.
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bohica
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RE: Why No Winglet On Horizontal Stabilizer?

Fri Jun 07, 2013 6:30 am

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.
 
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RE: Why No Winglet On Horizontal Stabilizer?

Fri Jun 07, 2013 7:46 am

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

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citationjet
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RE: Why No Winglet On Horizontal Stabilizer?

Fri Jun 07, 2013 1:14 pm

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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rwessel
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RE: Why No Winglet On Horizontal Stabilizer?

Fri Jun 07, 2013 2:48 pm

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.
 
GAIsweetGAI
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RE: Why No Winglet On Horizontal Stabilizer?

Mon Jun 10, 2013 7:57 am

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

Also:

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Starlionblue
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RE: Why No Winglet On Horizontal Stabilizer?

Mon Jun 10, 2013 10:07 am

The Liberator doesn't have winglets. Those are fins and rudders.
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GAIsweetGAI
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RE: Why No Winglet On Horizontal Stabilizer?

Tue Jun 11, 2013 12:20 am

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.
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Starlionblue
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RE: Why No Winglet On Horizontal Stabilizer?

Tue Jun 11, 2013 1:04 am

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.
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BMI727
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RE: Why No Winglet On Horizontal Stabilizer?

Tue Jun 11, 2013 3:59 am

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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ssteve
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RE: Why No Winglet On Horizontal Stabilizer?

Tue Jun 11, 2013 4:41 am

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?

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PC12Fan
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RE: Why No Winglet On Horizontal Stabilizer?

Tue Jun 11, 2013 3:27 pm

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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GAIsweetGAI
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RE: Why No Winglet On Horizontal Stabilizer?

Tue Jun 11, 2013 6:32 pm

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?)
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airmagnac
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RE: Why No Winglet On Horizontal Stabilizer?

Tue Jun 11, 2013 7:57 pm

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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rwessel
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RE: Why No Winglet On Horizontal Stabilizer?

Wed Jun 12, 2013 1:58 am

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.
 
GAIsweetGAI
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RE: Why No Winglet On Horizontal Stabilizer?

Wed Jun 12, 2013 7:45 am

Quoting airmagnac (Reply 23):
I'm not even sure the overall drag was reduced by the fins of the B24 by any measurable amount

Indeed, it probably increased drag.

Quoting airmagnac (Reply 23):
Could be something to do with minimising yaw effects due to the propeller slipstreams affecting the vertical stab.

But the vertical stab *is* in the propeller slipstream, pretty much...

Quoting airmagnac (Reply 23):
to fit the aircraft into hangars

Hadn't thought of it, and it does make quite a bit of sense.

Quoting airmagnac (Reply 23):
It may also have been a useful in combat, presenting smaller targets and providing redundancy

I thought I read somewhere that the B24 empennage ended up being quite fragile, and that quite a few of them were lost due to empennage failure...
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moriarty
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RE: Why No Winglet On Horizontal Stabilizer?

Wed Jun 12, 2013 1:41 pm

*lets On Tailplane? (by moriarty Nov 23 2012 in Tech Ops)

 
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