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-   -   DO winglets have effect on Vref when landing? (https://www.pprune.org/tech-log/537417-do-winglets-have-effect-vref-when-landing.html)

sky-738 5th Apr 2014 14:43

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 .

underfire 5th Apr 2014 16:19

738 without winglets?

B737900er 5th Apr 2014 17:24

This must be a simmer.:}

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

RVF750 5th Apr 2014 17:49

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

737Jock 5th Apr 2014 18:08

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....

737Jock 5th Apr 2014 18:18

As for 737-800 without winglets:

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

OMG:eek:

underfire 6th Apr 2014 17:14

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...

J.L.Seagull 6th Apr 2014 18:17

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! :-)

Wizofoz 6th Apr 2014 18:22

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.

underfire 6th Apr 2014 19:18

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?


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.
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...)

J.L.Seagull 6th Apr 2014 19:48

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.

RAT 5 6th Apr 2014 20:11

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?

underfire 6th Apr 2014 20:36

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?

J.L.Seagull 6th Apr 2014 20:43

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.

tdracer 6th Apr 2014 20:44

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.

737Jock 6th Apr 2014 20:46

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!

underfire 6th Apr 2014 21:21

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.

Intruder 6th Apr 2014 22:10

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...

arn3696 7th Apr 2014 00:52

...Due to lack of static wicks

J.L.Seagull 7th Apr 2014 02:06

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. :)


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