hydraulic power pack filter?

P

planebones

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The cruisemaster owners manual stated that there is a filter in the power pack that should be serviced annually.....Where is it? I had the dome off and still didn't see it...thanks Ken
 
Ken, If I recall there is no filter on the power pack but a finger screen located on the reservoir feed line to the engine driven hyd pump. The screen on mine looked like the fuel tank screen on a Cessna. I was into that system years ago and have not needed to touch it since. Don't mess with something working well. The Piper Aztec has a very similar power pack and I used their parts manual picture breakdown to replace O rings. Lynn the crate :D
 
Ken, you will not find anyone more knowledgeable and helpful than Lynn on this forum. I suspect he has touched every last component on a -2 Cruisemaster, probably including every nut and bolt. His response about the finger screen is correct based on my experience as well. So why does the Cruisemaster POH make reference to the "filter screen" in the Powerpak reservoir? Here is my speculation... as Lynn mentioned the Powerpak used in the -2 Cruisemaster (Electrol 750N) is very similar to that used in the Piper Apache and Aztec (Electrol 750P). The Piper unit does have a filter screen attached to the side of the big reservoir on the Powerpak itself (see attached view from the Piper manual). Perhaps the prototype -2 Cruisemaster used this Piper unit and the POH was written based on this - just a wild guess but sort of makes sense. Your question has prompted an additional question on my part which I will post as a separate topic. Please keep us up to date on your restoration work... Rob
 
Thank you for your knowledgeble responses. Since my aircraft has suffered two gear incidences in its recent past I am trying to discover the likely failure modes. My present assumption is that a leak (o-ring of the powerpack resivoir dome was the obvious leak) lost enought fluid that the engine driven pump did not have enough oil to get the gear all the way down. The hand pump, fed at a lower level than the standpipe in the power pack could have been used to get it down and locked. Please confirm a couple more assumptions: 1. when the handle pops back to neutral the retract cylinders are locked in the position they were pushed, but the hydraulic pressure guage will drop to 100 psi or so? 2. If the engine driven pump was to run out of fluid or fail mid cycle and not build up pressure and pop the handle back to neutral, the retract cylinders would not be hydraulicly locked?
I finished spraying my rebuilt flaps yesterday, working on carb air box repair (unless you guys have a spare you would part with). I have a prop being built, and am chasing a mid time takeout 0-470L, have landing gear torque link parts on order.......almost ready to fly!!!
 
Very impressed to hear about your progress! In response to your questions, here is my feedback based on a careful study of the Piper manual and my own experiences...
1) The gear handle pops into neutral as a result of the valve piston (they call it the "camshaft") returning to neutral based on the pressure build up when the actuators reach their stop. This seals off the hydraulic circuit preventing the return of the fluid from the actuator cylinder. Of course this locking action is only as good as the o-ring seal and some leak-down will occur over time. Once the handle and valve are in neutral there is no system pressure applied to the actuating cylinders and the pressure gauge is not reading the pressure out to the cylinders. The gauge is reading only the system pressure which is no longer doing any work and is bypassed back to the reservoir, thus the pressure drop-off on the gauge.
2) you are correct, if the system pressure from the pump fails and the gear handle is not in the neutral position the cylinders are not locked from a fluid flow perspective. You would need to return the handle to neutral manually. If your kick-down springs are working and the gear extends without the assistance of the hydraulic pressure, I am "assuming" that the cylinders would suck whatever fluid or air is available in the powerpak and allow the cylinders to reach the end of their travel. But you know what "assuming" means and I have not validated this behavior under the circumstances you describe.
The Piper Aztec manual is filled with good diagrams, operational sequence explanations and part lists so if you don't already have it go find it. If you have trouble finding it let me know and I will send you a download link. Looking forward to your report on the first flight! --Rob
 
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