Originally Posted by
sniper9652
And here was I thinking DC stood for 'Douglas Commercial'
O'h well!
Yes, don't be affraid! Must have been a joke from the guy who answered! DC stands really for Douglas Commercial.
About the DC8 flight controls, as a former DC8 pilot I'm going to try to gather some of my reminds: the DC8 has only one hydraulic system, which is parted in two halves, that become automatically isolated from each other in case of a pressure drop. The half that remains powered energizes some important stuff like braking system, flap and gear extension, etc...
OK, but what about the flight controls which is the subject of your topic?
Well, the DC8's flight control have a dual way to operate:
-primary way, with hydraulic actuators like almost every airliner.
-and back-up: in case of an hydraulic pressure drop as I told higher the hydraulic system parts in two halves, the hydraulic actuators of the flight controls are matching the part of the hydraulic system that is no more powered and thus what happens? Loss of control? No, no, no!
The flight controls on this airplane are linked to cables and rods coming from the cockpit via a reversion system that automatically switches from normal to back-up (and the opposite in case of pressure increase):
-Primary way: direct link from cables and rods to hydraulic actuators,
-Back-up: the reversion system switches the cables and rods to servo-tabs that aerodynamically power the flight controls. Each flight control (each aileron, each elevator and the rudder) owns one of these servo-tabs and handling the airplane with them is not a matter. I remember of a loss of hydraulic pressure that occured 2 hours before arrival, at FL390...We carried out the procedure, disengaging the autopilot, shutting down the remains of hydraulics (the goal beeing to keep a little fluid to try flap extension at arrival - If you can't it will imply a 0 flap landing with a Vref increased by 70 kts - and normal gear extension + normal breaking and nose gear steering). I was then at the controls of what would have been a turbofan powered DC3!
(Well, it was one of my smoothest landing at the controls of this wonderful airplane!).
Hope this helps, sorry for maybe having had a little "thick" explaination!
Dom