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DO winglets have effect on Vref when landing?

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DO winglets have effect on Vref when landing?

Old 7th Apr 2014, 02:49
  #21 (permalink)  
 
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JL...you have sunshades on the flightdeck?

App is but a small portion of flight, so enroute must be a @#$%&

but thanks for the info...I am sure the drivers reading the thread will appreciate!

EDIT: No really JLS, I am not trashing AB in any way..I feel their wing design is first class...I have been dealing with them on many fronts from the initial A380 'winglet' design...the A320 wing is very, very good..and as noted, doesnt have the vortex tabs as standard equipment.
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Old 7th Apr 2014, 10:43
  #22 (permalink)  
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ok, thanks everyone! Still have few question , why the 737 700 is hard to install winglet compare to 737 800 , both of them have the same wingspan. Do u mean the wingspan is the same but the structure is different? And also, why the 700 and 800 have different app speed when in same weight? Because the length of fuselage? Need an expert!
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Old 7th Apr 2014, 15:11
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Sky - the 737-800 has a significantly higher max gross weight than the -700, and hence the wing is aerodynamically the same but structurally different.
As noted, the 737-700 based BBJ has a -800 wing to give it a higher max gross weight, which is normally used in combination with body fuel tanks to give it longer range relative to the run of the mill 737-700.
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Old 7th Apr 2014, 16:43
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td has it correct, the 700 and original 800 wings needed to have reinforcement added for the winglets...later 800 wings had it built in from the start.

Some 800's have the same approach speed as the 700...
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Old 8th Apr 2014, 01:45
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Planes with winglets struggle to stay in LNAV due to crosswind pushing on winglets.

Previous poster mentioned difficulty in tracking centerline e while hand flying.
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Old 8th Apr 2014, 10:07
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Do you also trim downwind rudder while enroute so that crosswind component doesn't affect the vertical stabilizer?
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Old 8th Apr 2014, 16:05
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That's self-correcting, because it makes the nose point upwind when the tail is pushed downwind.
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Old 8th Apr 2014, 16:46
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trim downwind rudder while enroute so that crosswind component doesn't affect the vertical stabilizer
Wha? Cross-wind doesn't affect anything with regards to trim. The airplane doesn't know what the wind is...

Edit: Oh I see you got it from this:
Planes with winglets struggle to stay in LNAV due to crosswind pushing on winglets
Again, the airplane doesn't know what the wind is. It just flies in the body of air, whether the body of air itself is moving or not. The idea that an airplane will struggle to stay in LNAV due to a cross wind is just plain silly.

The earlier poster mentioned gusts on approach. Gusts will change the aircraft's flight, due to inertia. That plus when you're on approach, you're flying relative to the ground.

While enroute, in a stable condition, wind doesn't affect how any airplane flies. You (without autopilot/FMS/etc.) just point it a little upwind to compensate for it.
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Old 8th Apr 2014, 17:03
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A320 Winglets do not affect Vmca which means it doesn't affect Vs or Vs1g. So it shouldn't affect Vls or Vapp.
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Old 8th Apr 2014, 18:56
  #30 (permalink)  
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A320 Winglets do not affect Vmca which means it doesn't affect Vs or Vs1g

Might you elaborate a bit ?
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Old 9th Apr 2014, 00:20
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winglets are a fad...and do nothing positive...

The most fuel efficient plane in the world today is the Boeing 787. It has no winglets at all. Why? Because winglets by themselves contribute nothing.
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Old 9th Apr 2014, 00:28
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Planes with winglets struggle to stay in LNAV due to crosswind pushing on winglets.
And misd-agin says he is an airline pilot!

I think I've heard it all on this site now. Still you have to try and maintain a sense of humour I suppose.

Last edited by exeng; 9th Apr 2014 at 00:32. Reason: extra detail
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Old 9th Apr 2014, 02:49
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John
Actually from Airbus document on sharklets the only speed affected by them is Vmcg by 1KT on CFM. There are some other limitations but not on speed. Everything else remains same. I was trying to work backwards. Since Vmca is 1.2 or some multiple of Vs1g so apparently Vs1g is not affected and Vls is also a derivative of Vs1g. Or simply since Vs1g is not affected all speeds remain same. particular reference to Vmca was not necessary.

Last edited by vilas; 9th Apr 2014 at 03:04.
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Old 9th Apr 2014, 03:03
  #34 (permalink)  
 
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rsiano
Winglets are not fads. On an aerodynamically efficient wing design winglet do not contribute much. Development of 787 wing design may have taken that into consideration. But all other aircrafts 747, 737 even A320 now, benefit in terms of fuel saving by reduction in drag.
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Old 9th Apr 2014, 03:07
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Originally Posted by rsiano View Post
The most fuel efficient plane in the world today is the Boeing 787. It has no winglets at all. Why?
It has raked wing tips instead. Effectively the same thing but doesn't look as cool.

Is the 787 the most aerodynamically efficient 'plane in the world though?
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Old 9th Apr 2014, 04:27
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Winglets reduce the effect of span wise flow, which increases the strength of wingtip vortices. Increased vortex = increased drag (vortex drag which is part of the induced drag ie drag which is induced by the aircraft's velocity. Not to be confused with form drag etc which is a zero-lift drag function. That said, winglets have a surface area and therefore produce some form drag but I digress....)

They certainly reduce fuel consumption in steady state flight (the cruise) because like for like an aircraft with winglets will have a lower total drag and therefore require a lower thrust setting for a given speed or will be able to cruise faster for less fuel if you like.

With regards to 787, 747-8 etc with so called raked wing tips is more to do with aspect ratio but as you will note have a large degree of sweep relative to the rest of the wing at the tip. This serves to minimize the effect of the dastardly vortex. Aspect ratio being a function of span2/area is enhanced by increasing the span. Aerodynamically perfect wings would be infinitely long (amongst other things) to prevent the wingtip vortex ever forming.

This would of course make it a sod to park...

In answer to the post. Winglets will affect vref, but only slightly. A wing with winglets will stall at a slightly different speed to one without but not more than by a couple of knots. Both lift and drag are directly proportional to surface area and winglets obviously increase both. Like anything, hopefully the benefits outweigh the negatives.

Last edited by Dirty Sanchez; 9th Apr 2014 at 04:41.
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Old 9th Apr 2014, 05:50
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Vilas,

Vmca has absolutely nothing to do with any brand of Vs. Nothing at all. Vmca is about control surface power and thrust lever arms, meaning how much force the deflected controls, mainly rudder, generate and how far from the centre line are the thrust lines of the engines.

All the big Boeings I know about have a Vmca below Vs by a comfortable margin. Perhaps you were thinking of Vlo or even V2.
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Old 9th Apr 2014, 09:59
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vmca, with a for air, is below vs? please explain

as far as I know vmca is the speed at which the aircraft can be controlled with the most critical engine failed and a maximum bank of 5 degrees into the live engine(s). which means it is in the air, not stalling. in fact its impossible to be less then stallspeed, might be equal.
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Old 9th Apr 2014, 12:13
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I was involved in getting winglets installed on the Flyglobespan -800s cost around $500K to get done but more expensive if factory fitted.
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Old 9th Apr 2014, 12:28
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"Planes with winglets struggle to stay in LNAV due to crosswind pushing on winglets. "

Statements like this give our PROFESSION a bad name!!

I hope you're not on the same planet as me?
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