>Did the hydraulic pump run continuously? If so, I'd assume the centre position of the three position valve returned the pressure oil to the sump. The other two positions would guide the oil to either side of the cylinder.<
It would be more normal to put a pressure relief valve at the pump such that the whole circuit is held to a design pressure and the pump returned oil to the sump at that point.
As to did it run continuous ly... on the basis that it was a mechanical pump then it would seem the answer is yes..... yet with all Laggs and La's plagued with oil cooling problems generally, one would have thought that a continously running hydraulic pump was less than desirable.
>Since the valve was hand-operated, it would be standard procedure to let the piston run against the stop and then return it to centre position manually after a finite amount of time. Since oil is incompressible, a force-feeding pump might build up destructive overpressure during that delay. Hence the need for the bleed valve in the cylinder.<
The centre port did have a through port but it is shown going directly to the end of the piston valve assembly. In hydraulics to day this would be refered to as a manually operated/pilot (pilot valve not an aeroplane pilot) assisted valve. Whereby the oil pressure is used to lessen the force the operator must apply to push the slide across.
With this type of system the operator would be able to vary the flap deployment angle to suite his needs (between 0 and 60 degrees) but he could indeed push and leave the valve completely on one side or another for full or zero deployment with the pilot valve holding it in position positively.
We could speculate even further with respect to the publication which describes the by pass valve. A recent issue of "Aeroplane" magazine. The term actuator could have been lost in translation to mean the valve its self and not the cylinder actuator in the port wing. It could then be describing the pilot valve as this relief valve in error. (word plunger still applies)
However if we speculate potential error we can go in all sorts of directions.
All I can say is that where as once I was certain that La flaps stayed deployed until retracted or broken...........now I am not so certain.
Tilt
