Thursday Evening
12/20/07

Group,

We have the OP Technologies (now Aerosonic) EFIS and MFD in our IV-P, along with the Garmin AT avionics package.  For our backup system, we chose to use a vacuum pump operated attitude gyro, along with the altimeter and airspeed. Instead of using a dry pump, we opted to use a "wet pump" (old, old technology, but very reliable).  For the oily air discharge, we tapped into the crankcase vent air/oil separator with an additional pipe nipple welded in tangentially for the vacuum pump - just like the crankcase vent nipple.

We installed this identical system on another IV-P that now has about two years of operation - no problems to date.  Yes, there may be some additional oil on the belly that wouldn't normally be there, but cleans up easily. (crankcase vent still causes some oil film)  It is my opinion that this utilizes the "KISS" principle and certainly lighter than a second battery.

FWIW,

Ed Smith
Chesapeake, VA
IV-P Builder