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B737NG TE Flap

Fri Mar 12, 2004 11:34 pm

Why was the Fore flap deleted from the B737NG TE Flap.
I may not win often, but I damn well never lose!!! ;)
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RE: B737NG TE Flap

Fri Mar 12, 2004 11:56 pm

While I said in my profile that I was not going to address any more questions that start with "why" I will note that the NG aircraft has a wing that is completely different from the earlier 737s. It is nearly 18 feet longer, of much greater chord, smoother, and possibly different in other ways as well. I have never seen the shockwave on this wing while it is visible on the earlier models much of the time.

Perhaps there is something here (lighter wing loading maybe) that permits the use of a simpler flap design.

Happiness is not seeing another trite Ste. Maarten photo all week long.
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RE: B737NG TE Flap

Sat Mar 13, 2004 12:44 am

So Slamclick, do you want all questions asked in the form of any answer like Jeopardy?  Big thumbs up
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RE: B737NG TE Flap

Sat Mar 13, 2004 12:58 am

CdfMxTech Well, I guess that does sort of limit my choices here doesn't it?.

Seriously, I might be qualified to lecture on a number of topics, like high-lift devices used on jet transports, but to presume to answer "why" the manufacturer chose not to use triple slotted flaps ignores the fact that I was not present when the decisions were made. I did not hear the alternatives.

A while back I gave some answers that were accurate enough for pilot groundschool at the airline level. I had an engineer lurking on the forum sharpshoot me. What I said was not exactly wrong but his education was better than mine in this area and I realized that I had probably said more than I could back up. Not wrong, just overextended.

"I'll take 737NG for a thousand, Alex"

Happiness is not seeing another trite Ste. Maarten photo all week long.
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RE: B737NG TE Flap

Sat Mar 13, 2004 3:11 am

To put it simply, "save weight". The triple vs. double slotted flaps weight considerably more. Also there is not really a need for a triple slotted flap for the 737NG mission, so why add the mechanical complexity. Part of this stems from the new airfoil cross-section that the 737NGs use. As to how the specifics of all of this came about, I don't have too much insight. I do know the none of the other supercritical era wings of Boeing use triple slotted flaps. The wing loadings for the 737-400 and 737-900 are actually similar.
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RE: B737NG TE Flap

Wed Mar 17, 2004 6:51 am

And as a result, the B737NG has a higher approach speed than the Classics, and is less stable. B737 is not known for its good behaviour inflight, she can be quite a bit to handle, especially after an engine severe damage after V1.
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RE: B737NG TE Flap

Wed Mar 17, 2004 9:20 am

Why no triple slotted flaps on 737NG?

Since (I presume) none of us were NG wing designers, then it is of course all guesswork.

But in addition to various reasons such as weight saving, manufacturing cost saving, maintenance cost saving, not really needed due to greater wing area etc, let me propose one more reason:

Lower noise during approach.

Any views on that last guess?

Happy landing, Preben Norholm
Always keep your number of landings equal to your number of take-offs
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RE: B737NG TE Flap

Wed Mar 17, 2004 10:29 am

...Lower noise during approach...Any views on that last guess?

"Smaller" ("less-than-triple-slotted") flaps certainly would reduce approach noise, but the question remains...was this the reason Boeing dropped a triple-slotted design? As you said, Prebennorholm, none of us were on the 737NG design team, and without some facts/insider knowledge we can't know for sure why they weren't used. Sure "smaller" flaps reduce noise and weight but, along with more positives, there are of course negatives, too. One major negative is that, because the potential lift/lift coefficient of the wing is being decreased, stall speed increases. Many other pluses and minuses present themselves, and 737NG designers obviously factored all those in and concluded that "smaller" flaps would be better for the intended use of the aircraft.


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