Shadrach Posted September 18, 2019 Report Share Posted September 18, 2019 3 hours ago, carusoam said: While the engine sits for days... the prop’s oil system basically drains a pint of oil or so (estimate) back to the oil sump... To pressurize the system requires pulling the blue knob... (unless you fly a Missile or Rocket) The first time after start-up has a few things going on... The system is empty, and starts to fill when the knob is pulled... No pressure is generated until after the volume is filled... Once the pressure rises, the blades start to move... Pushing the blue knob back in, dumps the excess oil pressure, and the blades spring back to their flat pitch... If the oil is cold... things work slower... probably an OWT. Our oil pumps are gear type pumps... gear pumps deliver fluids from very thick to kind of thin... without any noticeable change in efficiency... so the same volume is being delivered hot or cold... Another thing to keep in mind... the oilP in the engine doesn’t really effect the oil pressure occurring in the prop... there are two gear pumps one for the engine, one for the prop... of course, if the engine isn’t supplying oilP, the prop, won’t have any to work with... when oil flows to the prop... the OilP for the engine does sense the pressure drop caused by the extra flow... that’s why we are looking for the oilP wiggle on the gauge... We have a gear pump in the accessory case, and one in the govenor... So the first pull of the blue knob does the same thing as the following ones each time... it just takes longer for the results to show... PP thoughts only, not a mechanic... Big question... the first pull of the blue knob is slow because the oil is cold...? Is this not an OWT for our engines? if it is an OWT... call it the Carusoam OWT... i’ll Clean up the explanation to help... Best regards, -a- Good description here but I have to say I have never found the prop circuit empty when removing a prop on a tricycle gear aircraft even if the plane has been sitting for weeks. Taildraggers with CS Props might drain because of the angle of the engine but I would not know. My PCU 5000 equipped IO360 A1A responds to the prop control quickly and at any RPM I’ve tried. My SOP is to pull it once at ~1000rpm during taxi or in the run up area. 1 Quote Link to comment Share on other sites More sharing options...
M20F Posted September 18, 2019 Report Share Posted September 18, 2019 You will hear the prop cycle, see oil drop, etc. so even if the tech is bad it is obvious if it is working or not (to trouble shoot, you still need to fix the broken parts). I don’t understand why when it isn’t functioning right you would fly it. I would look for differing CFI’s as well, not clear why they would depart with something amiss but not good judgment on their part. It is a run up item for a reason. I would have it looked at by an A&P/I prior to flying it again. 2 Quote Link to comment Share on other sites More sharing options...
RobertGary1 Posted September 19, 2019 Report Share Posted September 19, 2019 (edited) How long are you waiting? It may take a few second when cold. A lot of bush people set their gov'r slightly over red light for extra pull on short fields and otherwise take off with the prop control back to 2700. Maybe this guy was one of those. But you should just strobe test the speed. I'm wondering if there is something missing in your description. As a CFI I wouldn't fly with a student if there wasn't a change in RPM whenpulling the prop at runup. I assume most CFI's are the same. -Robert Edited September 19, 2019 by RobertGary1 Quote Link to comment Share on other sites More sharing options...
carusoam Posted September 20, 2019 Report Share Posted September 20, 2019 Many people exceed their redlines in certain experimental installations... A great way to develop extra HP for short T/O and stronger climb rates. And slightly faster speeds... There is costs associated with that... more fuel, more wear and tear, and plenty of sound and vibration.... To Get expected results... we are stuck following the expected red line. There are a few Mooneys that had so so red lines... find the Ovation and the Eagle for examples... The O1 has a redline of only 2500rpm. Bumping it up to 2700 rpm requires an STC... and you get 30 more hp to work with... The STC is the document to use that explains what you get when you use more rpms... and what you need to do to get the expected results... Accidentally getting more rpms is most likely not a blessing... There is a lot of support needed to go with them... PP thoughts only, not a mechanic... Best regards, -a- Quote Link to comment Share on other sites More sharing options...
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