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About pluessy

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    Well-known member
  • Birthday April 3

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  • Aircraft
    Tecnam P92 Eaglet
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  1. pluessy


  2. 2 blade vs 3 blade is comparing apples with pineapples unless you clearly specify what props are being compared. I changed a wooden 2-blade (GT) for a carbonfibre 3-blade (Bolly) and both my acceleration, climb and cruise have improved slightly (most consistent 1-2kts more speed at the same rpm and fuel burn). The carbonfibre blades are thinner and narrower than the wooden blades, off-setting the 3rd blade area and cross section. If you simply add a 3rd blade of the same thickness and planform, the result will be a less efficient prop.
  3. Hi, the specs that I have for the Sapphire LSA Mk2 show a MTOW of 320kg for the 447 and 350kg for the 503 powered units. The empty weight for the basic 447-powered aircraft is listed as 170kg to 201kg for a fully optioned 503. These specs are from the old RA-Aus website and the then manufacturer (Steven Dumesny).
  4. If you are still after a Bolly pitch gauge, mine is available?
  5. Negative to the last question. The Bolly pitch tool is graduated to 1/2 degree and very difficult to read. It also suffers from friction and is unstable when holding on the prop blade (needs to be kept accurate and still in 2 axis). I spent a long time adjusting my blades when I installed my new Bolly. Now I have made a precision tool that gives me repeatable results in a few seconds flat and found over 1/2 degree of variations. Preparation work is to have accurate station markings on your blades (I use 500mm from the hub, serves also as the pull-point for the engine friction test). Then set the trailing edge of the blade level through the spirit level (bubble), record the reading on the clinometer and go to the next blade. Pull the prop very slowly and from the top blade to minimise aircraft movement (this set-up is not sensitive to aircraft movement, unlike the stick/laser method). There is a bit more work involved if you are installing a new prop as you need to calibrate the 0 line first. For checking the pitch on each prop or to change the pitch from a known position, real quick and easy.
  6. Hi Scott, I used a small hammer and a rounded steel pin (ground it to the shape of the ball curve) to re-shape a couple of damaged ends. Then I used valve lapping compound to bed them in to their resp sockets. They are sealing properly again.
  7. Do the 100 hourly like an annual, record it as an annual and you are good for 100h or 12 months, whichever comes first.
  8. [ATTACH=full]62004[/ATTACH] I hope you finished this installation and fitted some drip trays (heat shields) under the carburetors? What size are your oil lines? They look smaller than mine.
  9. That's the whole problem wit this setup, there is no direct check. The only thing you can do is crank the engine with no load (spark plugs removed) until you have steady oil pressure. This way you at least know that the pump has been primed, and then hope for the best and keep an eye on the oil pressure gauge
  10. Sorry, need to correct you here. The oil pump is fixed displacement, the only control over the volume you have is the engine rpm. You actually throw oil away when you lower the PRV pressure as a portion of the oil leaving the pump is now being returned to the pump inlet and does nothing to lubricate or cool the engine.
  11. OK, defies logic. 45psi is 3 bar and that is well below the opening pressure of the PRV. Mine is on 4bar (5,000-5,200rpm) and changes ever so slightly with oil temp. I don't know what my relief pressure is, I have never revved the engine high enough with cold oil to see that pressure. One interesting fact with Rotax engines is that the running oil pressure actually increases with increasing oil temp. When I take off with 50deg C oil temp, the pressure is initially 3.6-3.7bar and then increases during climb to 4 bar when the oil temp reaches 80degC. This is a result of the diminishing suction line losses with decreasing viscosity, more than off-setting the increasing pressure loss in the post pump circuit.
  12. The relief valve is supposed to stay shut to 5bar. If there are pressure fluctuations that happen below that pressure, then an oscillating relief valve is a symptom and not the cause. Changing the relief valve in this case most likely "fixed" the issue as it would have a very different harmonic frequency (different spring and different plunger mass). Jabiru has that problem with oscillating pressure relief valves when the PRV is activated (high oil pressures). The pressure spikes are splitting oil coolers! It doesn't happen at oil pressures below the relief valve setting.
  13. To my knowledge, the oil is not affected in this application. The life of the oil is too short, 50-100h max compared to a hydraulic system (several thousands of hours). The most likely component(s) to cause cavitation (vapour) are also not oil components but fuel! When my oil temps wouldn't come up to 80-90deg C, I had over 2% of fuel dilution in the oil (most of the time it is under 1%). Cavitation is caused by a small part of the fluid experiencing a local pressure that is below the vapour point eg forming a tiny vapour bubble. Speeding up a pump that already struggles to get enough fluid supplied is not the fix. The usual remedy is the reduce the suction loss (reduce pipe length, increase dia and replace/remove fittings with low-loss versions). If that is not possible, increase the source pressure (elevated reservoir or pressurising it). I have a Tecnam P92 and Tecnam, in their wisdom, is installing the oil cooler with the inlet/outlet fittings down (contrary to Rotax installation requirement). After every oil change, I'm cranking the engine with spark plugs removed until I have steady oil pressure. When cleaning out the tank, I also drain the lines and then use a vacuum pump (oil sample pump) to bleed the suction lines and oil cooler at the oil pump inlet.
  14. There is a general misconception that the oil pressure relief valve REGULATES the oil pressure. All it does is LIMIT the maximum pressure at the location of the relief valve. Even the Rotax manual is wrong by saying "The oil pressure from 1.5 to 5 bar (22 to 72 p.s.i.) is controlled by the pressure relief valve (8). The surplus oil returns to the oil pump rotor via the channel (9)." The relief valve can't regulate the pressure below it's opening pressure. According to the Rotax manual that would be 5bar (the operations manual says max 7bar). Below the relief valve setting, the oil pressure is a function of volume (rpm), viscosity (oil temperature), pressure loss (filter, passages) and leakage (lube oil demand from all lube points). I had originally a thermostat fitted with very poor plumbing (90deg brass elbow, 180deg bend in the hose) and lower-than-ideal pressure and pressure fluctuations. Removed the thermostat and re-hosed the suction lines and now have rock-steady 4bar at 5,000-5,200rpm and 80-90deg oil temp. Oil temp control is not with an adjustable blank in front of the oil cooler (25-40% of the area summer-winter). The Rotax engine is the only engine I know of that has the oil cooler in the suction line. Any restriction will cause pump cavitation and erratic oil pressure, the relief valve is more likely a symptom rather than the cause.
  15. check out their history: 1400: abandoned VM 133 MK: abandoned JCV-360: abandoned
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