DC9/MD80 Slats Flaps system
The DC9/MD80 is a very simple airplane. Like the DC-8 (from which many of it's systems are derived) most controls are cable operated.
The DC9 series (from the -20's on up to the -90's) have mechanically operated, hydraulically actuated leading edge devices. Both left and right hydraulic systems actuate a drum looking device that uses cables to extend and retract the leading edge devices on DC9 wings. Very simple, very reliable.
In 8,000+ hours of DC9/MD80 flying I've never had one fail.
The DC9 has two position slats, retracted or extended, both mechanically selected by the slat/flap handle. The MD80 has three position slats, retracted, mid-seal and fully extended. Retracted and mid-seal are mechanically selected with the handle, full extension is selected by the AutoSlat computer.
An AutoSlat test is normally observed with initial flap extension. A successful test is one without an illuminated AutoSlat fail light. A rare fail light can sometimes be reset by selecting flaps up/slats retract and reselecting desired flaps setting.
And no, you can't see the MD80 wings from the cockpit. With my face up to the window I can sometimes see the flash of the wingtip strobes, but that's about it.
That being said, I will be surprised if the cause of the crash is due to a mechanical failure of the flight controls.
My condolences to the families and friends of all involved with the accident.
Dave