DO winglets have effect on Vref when landing?
 

Hello everyone,
I fly many kinds of 737s including 737_800 with and without winglets . When landing at the same weight , the one which have winglets have a small Vref then the one without winglets , just about one or two knots.
Can anyone tell me why ,because what I learned is that winglets is for fuel saving when cruising .

738 without winglets?

This must be a simmer.:}

Winglets also reduce drag, thats why the Vref will be slightly different between winglet and non winglet aircraft.

Defo a simmer The rest of us just fly what the box tells us......

Vref is derived from the stallspeed. Just google on the effect that winglets have on stallspeed and you will find your answer.

Sorry don't feel like writing a thesis on winglets, amongst the just fly brigade. Think induced drag, which also explains the fuel saving....

Reading some of these answers though makes me despair....

As for 737-800 without winglets:

Photos: Boeing 737-8Q8 Aircraft Pictures | Airliners.net

OMG:eek:

I guess there are far more 800's without winglets than I thought...Ryanair, SAS, Delta, and a few others, seems it was common when the 800 first came out...

Realted/unrelated...The A320 with Sharklets is significantly different...

A320 with sharklets
 

Underfire,

No it's not! An A320, with or without sharklets has the same Vapp speed (equivalent to Vref on a Boeing, I think).

Yes, there are some performance, operational and limitation differences, but Approach Speed is not one of them! :-)

Plus, as far as I an am aware, the major savings made by winglets are in high AofA situations like climb and approach, less so in cruise.

I meant the performance of the wing, not the OP Vref (sorry)..the sharklets make it very, very slick compared to the A320 with the typical winglets....the pilots noted it was far more difficult to slow it down.

EDIT:

Does Vapp differ with sharlet vs non-sharklets? It is calc'd by the FMGCS, (Vls +5), but is it the same?

Opposite is true...

Edit: OT..just wondering..the drivers said they were not briefed on the difference, and didnt know they had a sharklet plane until they got there and did a visual. Is this typical? They even mentioned they had a tough time slowing it down, I noted lots of speed brake after config 1, and then almost right to full flaps, pretty far out...(good thing there were 10 pax instead of a full load...)

Underfire, Wiz,

This has been discussed before, and I'm too lazy to type it all again. There's a thread "A320 with Sharklets" in which I've made a couple of posts. Good detailed info there.

BTW, sounds like a suspect training & safety team if the pilots weren't briefed on the introduction of sharklet A320s in the fleet. There are fuel imbalance limitations, auto-land crosswind limitations, and a whole bunch of other stuff that the trainers love bringing up every 6 months! LOL!

I've never flown a 737, so I'm not going to pretend I know anything about that bird, but would be happy to talk about the A320 sharklets if you'd like.

RYR's first a/c did not have winglets and then were retrofitted as later deliveries came with them as standard.
Curious why the takeoff & landing cross wind limits were different with & without. Was told it was the usual 'demonstrated' figure. Given it was used as a limit I wondered why a demo was necessary for such a small mod. There is no ground clearance issue, and I'd be surprised with there was a roll handling issue. Why not just use the higher value for both variants?

JLS,

Thanks, will look at the thread.

I know the 737 series with winglets is really slick compared to the ones prior. I would guess that the reduced drag near te ends of the wings and improved airflow from the sharklets, that the A320 would have similar features.

In the training, is this something the pilots are made aware of, the increased speeds, and issues with energy management on final?

Rat5,

The exact limitation difference is for AUTOLAND WITH AUTOMATIC ROLL-OUT; 15kt vs 20kt for non-sharklets aircraft.

When you hand fly an approach in gusty crosswinds, you need to 'fight' a little more with the aircraft to keep it on the centerline. This is due to the added vertical surface area of the sharklets blowing the aircraft to one side.

I guess, Airbus felt that the NWS and flight control systems weren't up to the task once the aircraft was on the ground, hence the limitation reduction.

The 737-800 did not have winglets at EIS, in fact they were not certified until several years after the -800 entered service. I believe they are now baseline on all new production -800/-900 variations.


Retrofit of the winglets is pretty simple on the 737-800/-900 due to minimal structural modifications required. 737-700 requires significant structural changes hence retrofit is quite a bit more difficult and expensive.
The -700 BBJ uses the wing from the -800, and hence can take winglets with minimal structural mods.

It slows down slower, I wouldn't say the differences are dramatic for a a320 Sharklet.
It's a nice excuse though for an approach that would have been pretty much as bad in a non-sharklet a320.
yes I have flown both, and the most annoying thing about the sharklet variant is the wingstrobes that light up the flightdeck at night!

BTW...I posted pics of the wing and flap settings here..

http://www.pprune.org/tech-log/53747...sharklets.html

its a nice looking wing, too bad about the strobe effect...I have a meeting coming up with the design folks at AB, I will ask them if they are going to fix it.

According to the 744 DDG, one winglet may be missing. There is a performance penalty of 9435 kg, but no change in ref speeds.

Interestingly, you can't takeoff with both winglets missing...

...Due to lack of static wicks

Underfire,

sops say:
"Set the STROBE selector to ON, before entering the runway. The flight crew can switch off the strobe lights if the lights cause any visual trouble during the flight."

This is specific to A320s with sharklets, and is listed as a TDU (temporary documentary unit). I.e. It can be implied that Airbus knows about the issue and are working on a fix.

In the mean time, just pull the sunshades down. It's 90% effective. :)

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.

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!

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.

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...

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.

Do you also trim downwind rudder while enroute so that crosswind component doesn't affect the vertical stabilizer?

That's self-correcting, because it makes the nose point upwind when the tail is pushed downwind. :)

Wha? :confused: 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:
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.

A320 Winglets do not affect Vmca which means it doesn't affect Vs or Vs1g. So it shouldn't affect Vls or Vapp.

A320 Winglets do not affect Vmca which means it doesn't affect Vs or Vs1g

Might you elaborate a bit ?

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.

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.

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.

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.

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?

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...:E

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.

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.

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.

I was involved in getting winglets installed on the Flyglobespan -800s cost around $500K to get done but more expensive if factory fitted.

"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?