DC-8-71 Flight Control System

[durbin]

I have posted this thread in other forums, but have placed it here also in order to get some more responses.

I am currently writing a report on the DC-8 flight control system for university. I have searched google for the answers and numerous books but have come up short on the following questions:

1. I know that the ailerons are power operated, but how is the actuator connected to the cockpit controls, cables, rods, electric?
2. I know that the rudder is also power operated but once again how is it connected to the cockpit controls?
3. How are the flaps connected to cockpit controls?
4. Is everything that is power operated connected to only a single hydraullic system or several?

Any other additional information that may be pertinent is also welcomed. In advance thank you for any replies.

Matt Durbin

[Fropilot]

The DC 8 be it a 60 or 70 series has a number of hydraulic subsytems that will function independently in case of failure of the main systems. I believe that that there are 8 such subsystems. But it is 7 years since I last flew the type. So you need to get hold of a manual.

Most items on the DC 8 are cable operated. There are levers in the cockpit for almost everything.

Quote " Works well and lasts a lifetime"

[CV880]

The DC8 flight controls were all connected to the cockpit by mechanical cables as was just about everything else including a few items that might surprise those not familiar with the DC8. Douglas loved cables; in the gyro compartment just fwd of the front spar it looked like you were inside a harp there were so many cables.
Regarding hydraulic systems-
The utility system (2 engine driven pumps and an auxiliary electric pump) operated everything except the spoilers but could power the spoilers via an interconnect valve.
The independant spoiler system had an electric pump and could be connected to the utility system in the event the pump failed.
The rudder standby system powered by an electric pump could be manually turned on to power the rudder in the event of a utility system failure.
I think that's it but it has been many, many years since I touched an 8.

[Halfnut]

DC = Direct Cable

DC = Direct Connect

DC = Douglas Cablecar

On the DC-9 and the DC-8 if it moves it was moved by a cable.

[CV880]

Durbin,
Since you specifically mentioned DC-8-71 there may be one more hydraulic system which I overlooked. I am not familiar with the 70 series with CFM56 engines but the DC8-62/63 had a Thrust Reverser hydraulic system powered by an electric pump which I think acted as a back up to the utility system which normally operated the reversers. The reversers were hydrualically powered on the DC8-62/63 and since they are used for in-flight speedbrakes on DC8's I guess a back up was needed in the event the utility system was lost. Possibly the reversers on the CFM56 used a similar actuation and back up system.