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Roger Mazengarb

Winglets optional?

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I flew on a Southwest 737-700 today and it was equipped with the longest winglets, at least 30-36 inches, I've ever seen. I never saw this on a 700 before and since I was one of the last off the plane I asked the pilot about them. He said SW has added them to about 30 of their 700 series planes and is planning to retro fit all their 700s with them. What is the benefit of the winglet?I never realized you can add these on after a plane is built but it does make me wonder why SW would go to the expense of adding them "in the field" and why Boeing doesn't see enough advantage to design them in.

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Perhaps you'll hear more responses in Hangar Chat, as this forum is really just specific to MSFS. I'll try to respond in case the thread gets moved. Basically, the winglets will offer SWA more range and will offset their costs in the fairly near future. I believe Boeing offers it as an option now on the 700 and 800... Obviously the BBJ has them. Why would an airline not want them? Not really sure, although I suspect it would have to do with the cost vs. the ROI vs. the time ROI is realized. A fleet with only a handful of 737-700's might not realize the cost savings as quickly... Who knows, only a guess...-John

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Hi,The winglets are actually supplied by Boeing, they are not an aftermarket item.The 737-700 and -800 are designed to accomodate these winglets and I actually thought that by default the -700 and -800 had them, although for whatever reason some carriers might not opt to have them on their aircraft.The fuel efficiency hence range is improved due to the lower drag (which is otherwise caused by the vortices that are generated, which increases induced drag).James

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I heard the Pilots of Airplanes with Winglets in the past (cough cough 747-400 cough cough) HATED THEM!! Boeing argued that they reduced drag but pilots said it increased drag.Who knows!?!?The one think that makes me wounder is How Do Winglets reduce Drag?? Konrad

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"How Do Winglets reduce Drag??"A lot of induced drag is created at the wingtips from the wingtip vortices. The wing ets reduce this vortice effect, giving you lower drag and increased fuel efficiency. Not sure at what point the winglet cost (approx $700k) outweighs fuel savings though. Airtran inially opted for the winglets on the NG's they ordered but then decided that they were not worth the extra cost. I'm sure the longer your routes are, the more cost effective they are.Eric

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The winglets save fuel in that the reduction of the induced drag allows the plane to climb to cruise altitude more quickly, thereby reaching an altitude where more efficient operations are possible sooner. This has more of an effect on longer hauls than on short trips wher you crusie at lower altides anyways. This is one reason why you will find that a lot of airlines that fly short distances (e.g. Ryanair, SAS, KLM, Easyjet) opted for no winglets or even removed winglets (ANA, JAL) from their aircraft. Those who fly longer hauls on the other hand chose to install winglets (AirBerlin, SWA, Hapag Lloyd).Misha

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Eric:>>Airtran inially opted for the winglets on the NG's they ordered but >>then decided that they were not worth the extra cost. I'm sure the >>longer your routes are, the more cost effective they are.Actually, I think it's the other way round. The winglets have a lot more effect in denser air. The big advantage is take-off and climb to cruise so carriers - like SWA - that do a lot of short haul will see more benefit than someone who does mostly long haul.Richard

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From my understanding, winglets in excess of 213ft made it difficult to maneuver aircraft around airports, so they were introduced on the 747-400 as a compromise between the extra lift required and maintaining parking bay and hanger clearances. The Airbus A340-500/600 also has them. The design improves cruise performance, producing extra lift with lower drag. They save about 3% in fuel costs. It's interesting though that the 777 has the most aerodynamically efficient wing shape ever developed for asubsonic aircraft, yet it does not use winglets. Robb

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From what I recall, this is my understanding of why winglets are considered a benfit. I'm not sure how accurate this is as I don't recall the source that I got it from, but as a CFI it makes sense to me. In-flight the wing of an aircraft is able to produce lift due to the airflow around the wing creating low pressure above the wing and higher pressure below. The higher pressure below tends to have an "attraction" to the lower pressure above, creating a lifting force. The stronger the lower pressure on top of the wing, the more lift that is created. However, some of this lower pressure can escape from the side of the wing, reducing the lift that could be created. Having a winglet on the end of the wing prevents some of the low pressure from escaping from above the wing's surface, therefore creating maximum lift. Hope this helps.

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"Actually, I think it's the other way round. The winglets have a lot more effect in denser air. The big advantage is take-off and climb to cruise so carriers - like SWA - that do a lot of short haul will see more benefit than someone who does mostly long haul."Richard, you may very well be correct on that. It makes sense since SWA does a lot of short-haul flights!Eric

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G'day Dean,Winglets increase the efficiency of a wing by1. reducing induced drag.Induced drag is caused by the high press airflow underneath the wing spilling over at the wingtip to the upper surface thus creating a vortex which is the cause of induced drag. The winglet creates two vortices that give a combined nett vortex that is smaller and therefore has less induced drag. Induced drag is dependant on angle of attack and therefore is greatest at low indicated airspeeds (high angle of attack). In cruise ( high airspeed ) angle of attack is low and induced drag is low.2. Winglet work just like sails on a sailing boat to produce thrust.The wig tip vortex affects the airflow outboard of the tip in such a manner as to cause the airflow to be drawn inwards towards the winglet and have an angle of attack to the winglet thus producing a basically horizontal lift on the winglet that is at right angles to the relative airflow. This means that the lift is acting slightly forward and thus there is a thrust vector.Boeing claim that they get up to 5% saving in fuel consumption on the built in (curved) winglets like on the BBJ for example. Bolt ons (747-400) are not quite as efficient and up to 3% saving is the claim.Winglet technology has been around for a long time. It's nothing new.Some propellors use "Q" tips which is a similar concept used on propellors.Cheers,Roger

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Hi Eric,Induced drag is a function of angle of attack ; not density!2 identical aircraft ( one at 10,000 and one at 40,000) at the same angle of attack would have the same induced drag ( but different IAS).SWA being a short haul carrier would benfit more from winglets because the aircraft are operating in a low airspeed high angle of attack flight regime where induced drag is greatest. Thus there is more saving to be made.Cheers,Roger

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Hi Eric,Induced drag is a function of angle of attack ; not density!2 identical aircraft ( one at 10,000 and one at 40,000) at thesame angle of attack would have the same induced drag ( butdifferent TAS).SWA being a short haul carrier would benfit more from wingletsbecause the aircraft are operating in a low airspeed highangle of attack flight regime where induced drag is greatest.Thus there is more saving to be made.Cheers,RogerSorry for the Freudian slip there Eric. I of course meant True Airspeed ( not IAS ). The IAS of both aircraft would be the same.

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