Originally Posted by
Smurfjet
Why do wingtip vortices start at lift-off point, and not before during the t/o roll? Actually is that statement true?
As long as there is airflow, there is lift. As long as there is lift, there
is induced drag and vortex.
An airliner produces lift (and vortex) when rolling with all wheels on the
ground - even if the AoA is negative.
Below is a Boeing airfoil Cl diagram. You can see the wing produces lift
even at about -3 deg AoA. An airliner on all wheels will usually
have a slight negative deck angle, but the wing will also
have a positive incidence of maybe 2-3 deg. So, all in all
a normal loaded acf will produce alot of lift when rolling.
With flaps even more offcourse.
If the wing wasn't producing lift when rolling on
all wheels, you wouldn't need ground spoilers....
Cheers,
M