While I worked for the Boeing company I built literally thousands of those drive shafts. The little "dents" in the end where the coupling goes are made by a process called electromagnetic pulse forming (EMF) for short. It was first used in the 777 program then to others. The spline ends are inserted in the tube then it is loaded into a "field shaper" and the EMF charge is applied forcing the annealed tube into the spline locking it into place. No mechanical fasteners are used. A sealant is applied at the joint after forming to prevent corrosion in addition to the spline ends being cadmium coated. They can range from a few inches to several feet in length and one inch diameter to two inch diameter depending on the application.
Those are technically not slats, but variable camber leading edge flaps. They are pneumatically powered which is what makes that noise. It’s loud enough to be heard over the engines running.
Flaps are to increase the surface area of the wing thus creating more lift. When the aircraft slows down it must increase lift to stay airborne. The least amount of flaps are used in takeoff while the most flap is used in landing.
@@davidoriordan1393 These tubes connect the gear boxes that turn the jackscrews that extend and retract the main flaps. I built thousands of them in my career with Boeing.
It’s the flap to fuselage seal, it’s there to seal the flap against the fuselage. This makes it more aerodynamic. Aircraft could fly without it but they will get performance/fuel penalties for that.
