Hydraulic help?

[zorgs]

Anyone out there with similar experience or technical knowledge who can explain to me why I feel a "sticky patch" (no connotations intended)during left cyclic movement on a Mi-8 MTV helo? The cylic moves freely for approx 2-3 cm then there is a resistance for 1 cm then it moves freely again for the rest of its travel.I can relate it to a "ripple" effect on a dam rather than "mirror image" water. ???? Get my drift? This anomaly occurs with and without auto-pilot and on both primary and secondary hydraulic systems.Thanks.

[Angry Palm Tree]

Doesn't sound like hydraulics - either a control run restriction or a binding spot on a friction pad (if there's one fitted!!?)


stoke me a clipper!

[Desert Rat]

Hiya Zorgs, long time no hear!!! Last time was at a bikers pub in hillcrest!!!! Got you wondering now???? We got lost en route to Ruacana in 2 Alo's ...mail me
[email protected]

[This message has been edited by Desert Rat (edited 05 June 2000).]

[zorgs]

Hi again .....Angry Palm Tree - what a name???? and thanks. Tried that already.....checked freedom of movement and regreased entire control runs, disconnected electromagnetic trimming system, replaced hydraulic actuator and more but problem still persist. May try the test pilot forum.
We are now using a Russian approved MIL SPEC hydraulic fluid versus the Russian AMG 10 fluid. Is it possible there is a difference in viscosity causing the problem.

Chow for now.

Desert Rat.....Loooonnnnngggg time no hear. For the sake of protecting your identity from the countless fatherless Angolan pecinans undoubtedly trying to trace you I will reply to your e-mail. "Privately"

[Cyclic Hotline]

Remote troubleshooting offers some difficulties, due to the unknowns of previous operating conditions and prior maintenance and repair activities. It is also possible I am simply describing what you have alrady done.

Be sure to start the troubleshooting sequence from step 1, and not find yourself at step 99, realising that one of the preliminary steps was missed.

Start with a review of any recently accomplished replacement, maintenance or adjustment to systems directly or indirectly connected to the flight control system.

Next, the basics of your mechanical flight control system. (I am unfamiliar with any systems in the Mi-8, so ensure there is no reason stated in the Maintenance Manual to not perform these functional checks!)

This type of problem is consistent with worn spots on bearings and hardware in the control run.

Start with a mechanical check of the flight control run. (This check will run between servo's if you have more than one in the system.) Disconnect the flight control run at the servo input, it will now be possible to move the controls, downstream of the servo, through the range with little effort. Check for binding or flat spots. It is also worth disconnecting at the Cyclic and verifying the lateral cyclic moves normally. If there is more than one servo in the control run, repeat the process. This may allow you to isolate, with relative ease, which part of your control run is causing the problem.

Perform the following inspection on either an isolated part of the control run, or the entire control run if unable to isolate any problem.

Disconnect each section of the control run in turn and inspect the rod-ends, bell-cranks, bushings and hard-ware. Turn the bearings in each piece to ensure there are no flat spots. Ensure that no hardware is either bound in the bearings, bushings or supports. Ensure you systematically inspect EVERY part in the system. Check the bearings and housing supporting the lateral cyclic support, ensure these bearings are secured properly in the housing.

Inspect any mixing unit interconnects.

Verify rigging, stops, freedom and range of travel.

Many other possibilities, but start with these first. Keep us posted.

[Angry Palm Tree]

The name came from a visit to Kapstaad, long ago. A farmer, on being told what I did for a living, called me 'Angry Palm Tree Driver'. I liked that and stuck with it.

stoke me a clipper!

[zorgs]

To Cyclic Hotline. Thanks for your very detailed reponse and I will be sure to double check all that you mentioned. Our engineers have been through everything mentioned but the problem still persists so they can start at the begining again.
Cheers.