lml@lancaironline.net Mailing List Archive

<<<<<<<<<<<<<<<<--->>>>>>>>>>>>>>>> << Lancair Builders' Mail List >> <<<<<<<<<<<<<<<<--->>>>>>>>>>>>>>>> Last week I flew over to Romeo Michigan and visited with Ed de Chazal (he has pressure gauges installed)- With his plane on jacks, the outback main gear is raised with 400 psi, the nose gear (against the gas spring) with 500 psi and the pump stops after hitting 1200 psi. In ten minutes, the pressure had dropped to 1100 psi and he noted that the pump won't start again until about 800 psi. In cracking the dump valve, the doors didn't start to open until the pressure dropped to about 500 psi and the gear began to drop down at about 400 -- note that the nose gear door had not quite opened completely when the nose gear began to drop. By this time the sequence valve stem extended, probably influencing the rate at which fluid is returned to the high pressure side. The door was brushed aside by the wheel. This may be why we get scratches on the door from the wheel - it could be the wheel is also turned by having to push the door out of the way. Think about the guy (like me) who installs a new gas spring -- more pressure to raise the nose against the spring and a snappier powered extension of the nose gear - maybe so fast it starts to beat the door and "closes" the sequence valve which slows the return fluid. Or it may be that the return fluid from the nose gear is under higher return pressure than the fluid from the door. Think about it (remember the sequence valve is marked for in and out). Additionally, I had a conversation with Mike Reinath (also has pressure gauges) and he had a problem with the pump internal relief valves -- He pointed me to Oildyne and I got a fax copy of how to adjust them -- they must be set 200 psi higher than the pressure switch. Imagine if the springs weaken with age or are set low enough to allow the hydraulic circuit to reach its shut-off pressure, but then the relief valve quickly drains the pressure off! My next experiment will to set the relief valve to a higher value. I also flew to Florida and back pulling the center console mounted 50 amp pump/relay breaker and running a timer. If I closed the breaker in 5 minutes, the merest blip restored the pressure (remember that the pressure switch would have already closed in the absence of any current across the contacts) with no radio noise. If I ran to ten minutes, the blip was longer and I felt a change in cabin pressure (ears). I think a relaxation on the doors had the famous Mister Bernoulli trying to suck me out the door gaps! I am going to try and find my Lagacy pressure switch and swap that in for the next test. Scott Krueger LNC2 N92EX Lagacy Kit #2 PS. Remember the North Central Lancair Fly in at KJOT - 23,24 June - Contact Doug McCallister at Mcgoose@mediaone.net _________________________________________________________________ Get your FREE download of MSN Explorer at http://explorer.msn.com LML website: http://www.olsusa.com/Users/Mkaye/maillist.html LML Builders' Bookstore: http://www.buildersbooks.com/lancair Please send your photos and drawings to marvkaye@olsusa.com.