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# Hydraulic restrictor

## Hydraulic restrictor

(OP)
I am calculating the extension and retraction times of a Fokker 50 landing gear. I found some restrictors in the hydraulic scheme of the Fokker 50. I know the flow before and after the restrictor. Is it then possible to calculate a certain factor or relation between the hydraulic flow and the restriction? Or are there some formulas to calculate this? I hope that I can calculate the hydraulic flow after the restrictor if the flow before the restrictor varies! Who can help me solving this problem? According to me; the bigger the flow the more the restrictor pinches the flow.

Before restrictor            After restrictor

7.9 gal/min                  2.43 gal/min
1.5 gal/min                  ??????????

### RE: Hydraulic restrictor

Some of the factors that can affect flow across a flow control are size of orifice, differential pressure across the orifice and temperature of the fluid. Pressure and temperature are compensated for in some controls and size of orifice is adjustable in some. The flow vs. pressure is not linear.

Often in gears there are resistors to prevent the gear from coming down too fast.  In order to accurately measure flow, I think you would have to remove it and put it on a flow bench, where you can control the variables.  Fokker or the gear manufacture (Dowty I believe) may have the flow rate in their component overhaul manuals. Otherwise, swapping out with a known good valve for troubleshooting may be easier.

BTW There are several other causes, both hydraulic and mechanical, that can cause retraction times to be wrong.

Cheers

### RE: Hydraulic restrictor

(OP)

Cheers

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