My plane came with a large venturi on the passenger side and a small one on the pilot's side. The large one was driving a HUGE, OLD, HEAVY (4 pound) horizon. The small one was connected to the DG and did not generate enough vacuum to run it. I removed the large-old-heavy horizon, in order to reduce gross weight for my checkride and to make room for a yet-to-be-installed smaller, newer horizon. I connected the large venturi to the DG and replaced the small venturi with another large one, which is meant to drive a yet-to-be-installed horizon. So, I should end with one large venturi driving just the DG and another large venturi driving just the horizon. I know I am paying a drag penalty with that second large venturi, but I want a horizon, just in case I run into a tight spot... Eliacim
> I had the same setup on my last Ercoupe and had the same problem. I > sent the horizon to the shop three times before I finally got the > attention of someone there that understood venturi systems. He told > me that the 3.5 inch instruments require more volume of air the the > old 5 inch ones. I was getting plenty of vacuum but not enough volume > to run both instruments. I discussed this with him and our region 13 > tech guy and was told that if I moved the venturi to the passenger > side I would probably get enough volume to run them both. I elected > to remove the horizon since I didn't look at it enough to justify > drilling new holes in the side of the plane. I had an electric turn > and bank that gave me wings level info and that was sufficient for me > and this is what I have in the present Ercoupe.. > > Kevin > > --- In [email protected], "Randy Hougham" <[EMAIL PROTECTED]> > wrote: >> >> I have a DG and an attitude indicator on the same venturi. It's the > biggest >> Wag-Aero venturi that is supposed to run 3 instruments. In flight > my vacuum >> gauge usually shows 2 1/2 to 4" of mercury. Sometimes, the attitude >> indicator will act strangely, rolling over or doing other odd > things. The DG >> is always working fine. I'm trying to figure out what the problem > might be. >> >> My venturi is mounted on the pilot side, just aft of the engine > cowling, on >> the part of the fuselage that is angled as it widens for the > cockpit. So the >> venturi is parallel to the fuselage, but not pointing straight > ahead. Could >> this be a problem? Where do most people mount a venturi on an > Ercoupe? This >> set up has been on my plane since I got it, and I'm not sure that > it ever >> worked 100% all the time. Before I send my attitude indicator in > for a >> re-build, I'd like to figure out what the problem might be. >> >> If any one can help, I'd appreciate it. >> Randy Hougham >> Grandpa's Ercoupe >> NC87384 >> > > >
