TechRep From , joined Dec 1969, posts, RR:
Reply 1, posted (12 years 5 months 4 days 22 hours ago) and read 2364 times:
Ok this is completly from memory so here goes:
DC-8 Hydraulic system:
Flaps (largest hydraulic user)
Spoilers (flight and ground)
Ailerons (bad leaker)
Slots (2 actuators per side, bitch to change)
Rudder (hell hole name says it all)
Horizontial Stab/Alt Stab (hydraulic/electrical)
Thrust reversers LONG DUCT(hydraulic actuated/ 12 PSI pneumatic assisted)
Thrust Reversers SHORT DUCT (Pneumatic)
Cargo Door (Douglas Door/Skydrol)
Cargo Door (Rosenbalm/5606)
So in fact all the primary and secondary flight controls are hydraulic. I think the complete Hydraulic system is 21.9 gallons and 12 gallons down to the stand pipe, with 9.9 gallons in reserve. The DC-8 uses a priority valve at 1750 PSI of reducing pressure a valve closes and only primary flight controls are available off the hydraulic manifold.
A large weakness on the DC-8 is the bogie trim compensator. It has no hydraulic fuse and the hydraulic line is under the landing gear bogie. If ruptured it will drain the Hydraulic system down to stand pipe in 3 seconds. It was always said, if you see the DC-8 taxiing with gear doors down your going to have a long day. The controls for hydraulic selection is on the Cash Register which includes 3 positions. Hydraulic pump can be selected from F/E position or Capt's position, however on some models no Capt's position is available.
As far as the B707, I have no idea about that aircraft other than the DC-8 is a better airplane.
727pfe From , joined Dec 1969, posts, RR:
Reply 3, posted (12 years 5 months 4 days 10 hours ago) and read 2345 times:
The 707 had cable operated ailerons and elevator. The rudder was hydraulic with a manual reversion. The T. E. flaps, L.E. flaps/slats and spoilers were hydraulic. The stabilizor was electric. The stab actually had two motors, the primary controlled by the yoke switches or with manual handles on the center pedestal stab trim wheel, and the alternate motor used by the autopilot and mach trim system.