lml@lancaironline.net Mailing List Archive

<<<<<<<<<<<<<<<<--->>>>>>>>>>>>>>>> << Lancair Builders' Mail List >> <<<<<<<<<<<<<<<<--->>>>>>>>>>>>>>>> The few responses so far have had a common thread but missed the point. They all focused on the pump and how Oildyne can fix the problem, service the pump, etc. I have installed a brand spanking new Oildyne pump in my 320, the same vintage of the one I just received for my Legacy and the problem persists. Let me try to re-state the problem specifically for the gear up operation: 1. The Hi pressure switch must be set higher than the pressure required to keep the gear up because extra force is required to overcome gas-spring locked over-center links (nose gear 320, all gear Legacy). Some small leak back (cross over, etc.) will occcur whether its because of system ageing, manufacturing variance, system construction variance, temperature, day of week, phase of the moon, etc. But, not much leak back occurs since I have noted that the gear will remain up for more than three days whilst the aicraft sat on jacks. Even the spring loaded doors didn't come all of the way down! If the master switch is left on, the pressure quickly drops enough to have the pressure switch activate the pump for just a blip to restore the max pressure. For me, this occurs every 15 seconds or less. 2. We are on the third generation of crummy pressure switches -- Lancair would be happy to replace my current defective one with another. Note that this "new" type slowly closes the contacts as the pressure builds so that electrical static is produced (and heard in the radio) ahead of activating the pump relay and which will eventually degrade the contacts. I know, I know. There are ways to fix the noise by applying another band-aid or I could replace the switch and cross my fingers. 3. The problem is not unique to Lancairs. My old Skymaster would activate the pump in flight every 20 minutes or so. This was totally acceptable and hardly noticeable. The Skymaster had, arguably, the most complicated hydraulic gear system on any aircraft with a very high parts count. After being left alone in the dark for several days the gear leg doors would sometime sag down a bit, other times not at all. There are variances in all systems. The solution to these problems that some of us are having, and others will have, lies in the pressure switch. The most desireable adjustable switch would have a dead band of several hundred psi, just like the pressure switch that automatically controls your air compressor -- shuts off the pump at 120 psi, doesn't start the pump again until the pressure drops to 90 or 100 psi. Surely, there is an engineer, scientist, or tinkerer out there that perhaps knows a source of such switches. Help! Scott Krueger _________________________________________________________________ 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.