PPRuNe Forums - View Single Post - Caribbean B738 at Georgetown on Jul 30, 2011, overran runway
Old 15th Aug 2011, 01:50
  #180 (permalink)  
westhawk
 
Join Date: Jun 2005
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I do not understand this procedure of retracting flaps on the landing roll as they will transistion from the gratest drag posistion to the greatest lift posistion on its way to a fully stowed posistion and adversely affect the weight on wheels for proper braking.
The rest of your post makes sense to me but the above quoted text doesn't.

While full flaps produces more drag, more lift per unit of airspeed is produced as well. Note the lower Vref speeds associated with increased flaps setting. On jet transports, ground spoilers increase the weight on wheels and produce additional drag. This is far more effective at dumping lift than retracting flaps and adds drag instead of reducing it.

Retraction of flaps during the landing roll reduces the amount of lift produced at any given airspeed, thus increasing weight on wheels. It is an accepted and even manufacturer recommended technique to reduce landing roll distance on some light aircraft. Especially handy in bush flying.

I'm not aware of any jet transport aircraft where flap retraction during the landing roll is a recommended or approved action though. Ground spoilers are far more effective anyway and the danger of inadvertently selecting gear up instead of flaps up is mostly eliminated.
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