Go Back  PPRuNe Forums > Flight Deck Forums > Tech Log
Reload this Page >

Effect of Flaps on B737

Tech Log The very best in practical technical discussion on the web

Effect of Flaps on B737

Old 15th Oct 2019, 14:30
  #1 (permalink)  
tae9141
Guest
 
Posts: n/a
Effect of Flaps on B737

I read a phrase from B737 FCTM and it says as below:-
"The leading edge devices ensure that the inboard wing stalls before the outboard wing."
Is this because of how inboard lead egde flap is situated or is it different theory that supports aforementioned idea?

 
Old 15th Oct 2019, 15:08
  #2 (permalink)  
 
Join Date: Jun 2019
Location: VA
Posts: 210
Originally Posted by tae9141 View Post
I read a phrase from B737 FCTM and it says as below:-
"The leading edge devices ensure that the inboard wing stalls before the outboard wing."
Is this because of how inboard lead egde flap is situated or is it different theory that supports aforementioned idea?
While we tend to think of a wing stalling at a single AOA value, usually the stall begins in one area and spreads to other regions as the AOA is increased. It is desirable to have the stall begin in areas away from the roll control devices (usually the wing root) so lateral control can be maintained approaching and even into the the stall. That said, the stall characteristics of a clean wing can be significantly different than when in the landing configuration, particularly with swept-wing aircraft which have a tendency to stall at the wing tips. Leading (and trailing) edge devices changes the effective camber and chord line of the wing, and the amount of this change can vary along the cross section from wing root to tip. Effective design of these devices, sometimes with the addition of vortex generators, will ensure that roll authority is retained in the landing configuration in inadvertent high-AOA situations (e.g. windshear).

Last edited by Tomaski; 15th Oct 2019 at 16:29.
Tomaski is offline  
Old 15th Oct 2019, 15:22
  #3 (permalink)  
 
Join Date: Oct 2006
Location: Ankh Morpork, DW
Posts: 612
Couldn’t this simply be in reference to the inboard stall strips?
ImbracableCrunk is offline  
Old 15th Oct 2019, 16:12
  #4 (permalink)  
 
Join Date: Nov 2010
Location: Denver
Age: 53
Posts: 86
Originally Posted by Tomaski View Post
While we tend to think of a wing stalling at a single AOA value, usually the stall begins in one area and spreads to other regions as the AOA is increased. It is desirable to have the stall begin in areas away from the roll control devices (usually the wing root) so lateral control can be maintained approaching and even into the the stall. That said, the stall characteristics of a clean wing can be significantly different than when in the landing configuration, particularly with swept-wing aircraft. Leading (and trailing) edge devices changes the effective camber and chord line of the wing, and the amount of this change can vary along the cross section from wing root to tip. Effective design of these devices, sometimes with the addition of vortex generators, will ensure that roll authority is retained in the landing configuration in inadvertent high-AOA situations (e.g. windshear).
Yes, because of how inboard lead edge flap is situated ( as compared to the outboard flap) .

Tomaski is totally correct IMO, just trying to keep it simple.
hans brinker is offline  
Old 15th Oct 2019, 16:41
  #5 (permalink)  
 
Join Date: Jun 2019
Location: VA
Posts: 210
For further reading: Airflow Control

Excerpt:

Leading-edge devices did not come into vogue, however, until the advent of swept-wing, turbojet airplanes. Such wings have a particularly nasty trait: the wingtip stall. Instead of the stall's occurring near the wing root and propagating outboard (as with straight wings), the stall of a swept wing begins near the wingtip. This can result in strong nose-up pitching moments, sharp and uncommanded roll rates, and reduced aileron authority. Aircraft designers obviously go to great length to preclude the possibility of such a stall.

One solution is to install slats or — as in the case of the Boeing 727 — a combination of slats and leading-edge flaps. It is natural to wonder why Boeing uses inboard flaps and outboard slats on the "three-holer." The answer is both simple and clever. Because the leading-edge flap is less effective in delaying a stall than a slat, the inboard section of the wing is forced to stall first, thus preventing the possibility of a tip stall.
Tomaski is offline  
Old 15th Oct 2019, 23:14
  #6 (permalink)  
tae9141
Guest
 
Posts: n/a
Thanks everyone for your participation!
 

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information -

Copyright © 2021 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.