737-900 airfoil

[underfire]

Heres one for you wing design folks...

Was just on a flight with a brand new 900. I was noticing some interesting things about the new airfoil.

The 'flipper' is rather large (and there is another smaller one. note the bump next to the engine mount as well)

http://i44.tinypic.com/2ci6ye1.jpg

The winglet is a bit of a different configuration..

http://i41.tinypic.com/2ebz4o6.jpg

I noted tubulence tabs down about 3/4's of the wing... (stall issues?)

EDIT: btw, we were heavy, but a short hop with likely little fuel in the wings...notice the amount of flex?

http://i42.tinypic.com/noyr81.jpg

Let the conversation begin! :}

[barit1]

The "flipper" is known as a "strake". DC-10's had them both inboard and outboard sides of the #1 and #3 engines.

[lomapaseo]

How big a deal are these strakes

can the cowls be interchanged, thus reversing what side (inner or outter) the strakes are on ?

[underfire]

Its is one of the largest strakes I have seen. (thx barit for the correct term)

loma, strakes are used to improve airflow at high levels of attack. Noting the configuration of the cowling (the detent on the upper left corner), these are not reversible

I understand the concept, and this combined with the large number of vortex tabs, seems to be significant in regards to stall issues with the airfoil.

[Yeelep]

Thanks for flying my favorite airline.:ok: That first picture looks like gate D3 or D4 at SEA.

The strake, or vortex control device (VCD) in Boeing speak has always been on the inboard side of the engine.

The bump that looks like a ski jump is the krueger door seal fairing that creates a seal against the k-flap when extended. Just inboard of the fairing is the krueger flap deflector(the short thick strake). The purpose of this is to force the krueger flap door to hinge aft when the thrust reverser translates aft.

Don't see any obvious visual difference between that winglet and any other winglet on the Alaska Airlines NG's. There is a similar version that uses a single lense for the strobe/position lights.

The strakes (VCD) are a big enough deal that they cannot be CDL'd, so they must be present. Yes the fan cowls can be interchanged between positions. The strake has to be added or removed depending on position. For example, you could remove the no.1 outboard fan cowl, attach a strake and install it at the no.2 inboard position.

[underfire]

Yee,

Yes it was D3! In talking with the Boeing guys, they told me the airfoil on the 900 is a new design, and the winglet leading edge is different...I was asking about all of the vortex tabs on the wing, but all they would say is for low level stall conditions.

To me, it looks like the winglet begins back from the leading edge much more than before...not just a rollup.

EDIT: did you see the carefully planned Mt Rainer in the background?

[Yeelep]

I took a quick look and the winglets for all the AS -800's and -900ER's are interchangeable, so I would be surprised if they were any aerodynamic differences. I didn't check the -700's and -900's.

Makes sense about the vortex generators, but I am not a Engineer or Aerodynamicist.

Yes on Mount Rainier. The second pict. has the Tacoma Narrows bridge with the Tacoma Narrows Airport in the foreground, nice.

[tdracer]

I don't believe there are meaningful aerodynamic differences between the wings on the different versions of the 737NG. There are structural differences however - turned out they could put the winglet on the -800 and -900 without updating the structure, but the -700 needed structural changes.

The strake on the side of the engine is to address a very specific condition. With an engine inop and the high angle of attack during approach, the spillage air from the inlet would cause separation of airflow over that part of the wing. The strake is basically a big vortex generator to re-energize that air spilling out of the inlet and keep it attached.

Inboard strakes have become pretty common on the large, high-bypass wing mounted engines (they're even on the 747-8). On the DC-10 (where the strakes were on both side of the cowling), we used to refer to them as the "Engine Ears" :E

[TURIN]

A medium size Boeing was discovered to have been flying around with strakes missing on both engines quite recently. Wrong cowlings fitted apparently. No one noticed for quite some time as the a/c "looked" symmetrical.

[Gas Bags]

Retro fitting winglets to the NG and structural changes required had nothing to do with the series (-700 as mentioned)...Structural changes were required prior to a certain line number aircraft if fitting winglets.

[tdracer]

Gas Bags, unless my memory is failing me (a distinct possibility :}) that came out of a Boeing press release - they were able to start fitting winglets on new production -800s immediately, but need to design structural changes before they could put them on new production -700s. Note this was specifically referring to new production, not retrofit, although I'm not sure why that would make a difference.

BTW the BBJ was an exception - although it has the -700 fuselage, the wing is off a -800 (to give it a higher MTOW and more range). As a result the BBJ was among the first to get winglets.

[ImbracableCrunk]

If that was a new AS -900, then it was a -900ER ETOPS bird.

Since we didn't get any of the extra fuel tanks put in, the joke is that the "ER" stands for Extra Row.

[flyboyike]

loma, strakes are used to improve airflow at high levels of attack.


I presume a high level of attack would be when a rather large number of tanks are coming at you from all directions.

[underfire]

ooops...high angle of attack!

[ImbracableCrunk]

I noted tubulence tabs down about 3/4's of the wing... (stall issues?)

Those would be vortilons.

[underfire]

Sorry IC, but I was talking about these:

http://i44.tinypic.com/n2miad.jpg

not these:

http://www.b737.org.uk/images/wing_ng.jpg

[ImbracableCrunk]

Nope, that's an alula, or a bird thumb-slat in that pic of the mallard. Cool pic.

The NG actually has fewer VGs than the classics.

[underfire]

You may find this interesting...

http://i40.tinypic.com/28synph.jpg

[lomapaseo]

You may find this interesting...


Needs some smoke for realism

[underfire]

The duck has since claimed patent infringement on the split scimitar and max x winglets... :rolleyes:

[ImbracableCrunk]

Messerschmitt stole from sharks, Boeing is stealing from ducks, airbus steals from whales, Sukhoi from platypii, Embraer from Combinacion No. 2 con mas arroz y frijoles. :}

[BARKINGMAD]

And I thought the 600-900 series 737NGs were the same wing with a different SLF tubular container hung in between the flappy bits?

"There has been an alarming increase in the number of things I know nothing about!" to quote Ashleigh Brilliant.

Thanks for the info folks, and that after 9 years driving the beasts viz 700s + 800s.

Thankfully I didn't have to wrestle with the peculiarities of the -900, with all its MAC% versus T/O thrust problems?

It's still a good craft, especially the -800 with 26k engines, it does what it says on the tin...............:)

[underfire]

Bark, I would agree, the 800 hit the sweet spot...the combo with 26K was about the best. :ok:

The Boeing winglet design has especially transitioned models over time...the leading edge is the clue. It used to simply rollup, but then the issues led to the leading edge of the winglet, being set back further from the leading edge of the wing section.

Actually, the Airbus winglet has addressed the discontinuty from the beginning...