lml@lancaironline.net Mailing List Archive

<<<<<<<<<<<<<<<<--->>>>>>>>>>>>>>>> << Lancair Builders' Mail List >> <<<<<<<<<<<<<<<<--->>>>>>>>>>>>>>>> Even the simple fuel transfer system and original 320/360 header tank design is better than a low wing/wing feed one at a time only system. Using an accurate fuel monitoring/warning system and any of the automatic fill methods, the header tank systems is far superior. Here is an example of one and the reasons why: I use Vision Microsystems EPI800 (like VM1000) fuel monitoring system which is very accurate (when properly calibrated at installation) for digitally indicating fuel quantity it each of the three tanks. It gives a warning for low fuel in each of the tanks. The float switch in the header drives my automatic keep-the-header-full system that maintains between 8 and 9 gallons in the header at all times by running both transfer pumps together. There are individual pump switches also. Benefits: 1. I need only to monitor the system - no other activity is required. 2. Under the worst scenarios, such as total power failure, I have 8 gallons @ say, 170 KTAS at 8.5 GPH or conservatively, 45 minutes and 130 NM to find a place to set down. 3. Wings are pumped out equally - no trim issues. 4. Wings are pumped out in level flight (cruise) and, on long trips, are sometimes emptied. I know this when the wing quantities indicate zero and the header tank won't fill up after it indicates 8 gallons, at which time the system is shut off. The pumps are not damaged by running almost dry for a few minutes and an examination of the wing tanks has shown only a cup or two of unusuable fuel, just enough to keep the diaphragm pump's innards moist. 5. The header tank is deep (about 9 inches) with a nice sump at the bottom. In level flight, almost all the fuel is usable. In gentle ascent or descent, probably down to the last gallon because the tank is short from front to back. In turns of any quality, you only have about 3 feet and baffles to work with, not the length of the wing. I once had to avoid a storm by running on the front side of it and landed with only 4 gallons in the header. No problem, but I was nervous. 6. In aerobatic flight, the wings are empty and the header is close to most centers of rotation. If the wings are empty, there are less problems with rotational momentum and none with unporting - just the time to try that flat spin you always wanted to do. Because of this discussion however, I will do thorough testing of the fuel system in my Legacy (no header tank in my lap) -- such as where the fuel goes in 15 degree ascents and descents. How long it takes to get it back and what the real usable is in that plane. I have contemplated obtaining a "lipstick" video camera and examining the interior now that the wing is closed, but before all the hardware is installed. I want to see if the squeeze-out plugged anything up. Scott Krueger LNC2 N92EX Legacy Kit #2 _ LML website: http://www.olsusa.com/mkaye/maillist.html LML Builders' Bookstore: http://www.buildersbooks.com/lancair Please send your photos and drawings to marvkaye@olsusa.com.