Originally Posted by
DrivingRain
Isnt the real question this?
Upon landing why arent flap angles reduced from a high amount to 5 degrees (or 10...whatever the most likely flap retraction angle at takeoff) instead of going all the way to 0?
I think the OP understood their role in flight...but not this specific procedure.
The amount of flap needed for takeoff will vary. Things that come into play include weight of the aircraft, DA, winds, length of runway used for departure. (DA=Density Altitude)
Edited to add: As far as weight of aircraft, not only do you have the passenger and cargo load, but you have
fuel. If you're at CVG - is the aircraft going to Los Angeles next or is it going to Louisville?
FWIW: The amount of flap needed on arrival (flaps help provide lift and stability of aircraft at lower speeds) will also vary depending on several factors. Depending on winds, you may need to come in faster. For example, what happens if you have a loss of 10 on final? (hopefully you'll be at a faster approach speed should this happen) -- it takes engines time to spool up should you need an immediate increase in airspeed or conduct a go around.
Unlike smaller GA planes (which you can stall over the runway), commercial jets will always stay well above the stall speed when landing.