Need some help here. I have never had a engine want to quit on the down lines. The set up is a Tartan Twin on gas. (I know I will call Jim Cline when home). When flying any average to long down line the engine just dies, as the plane rotates back to level flight it restarts. (you can hear the ignition cutting off and then back on). All lines are o.k. with great draw, vent line is clear. However when tipped toward nose fuel runs out of the vent line. I am thinking maybe it is causing a suction problem when the fuel shifts forward.
Any suggestions?
V-Snap

I used to fly a Tartan twin on a Byron Pitts. The way I solved the problem was to close the hole in the cowl where the air came in to the carb. My tartan had a yellow air scoop which pointed into the air stream. When I went to idle on a down line or from full throttle to idle in level flight, the sudden change would cause air to be rammed into the scoop causing the engine to go lean and die. This may or may not be your problem.

Ken

I have a carb extension pointing down so it is not getting ram air like the yellow scoops provided.
Another idea I am pondering is that for some reason the fuel is not being picked up while in the down line causing the it to starve itself. I don't know what kind of fix would work for the pick-up or maybe the carb isn't drawing the fuel.
V-Snap

How is your idle set? I would recommend that you make it a little rich.

Are you using a foam clunk in your tank? I get mind from a chain saw shop(Stihl) and they work great! They will actual hold fuel and keep delivering fuel to the carb while the clunk is above or out of the fuel.
It does sound like a fuel problem.

Doug

Does the foam clunk work as a filter and a clunk?

Yea I believe I have what you are talking about. It is a heavy clunk with a thick piece of felt attached around it. I have used this type of set up for years on my gas engines without problems.

I will richen the low end more and see, trial and error I guess till I find something.

Sure does suck though when you get a nice down-line and you hear the engine start to wind down as it starts to shut down.

Thanks for the input.

V-Snap

V-Snap, I don't think it would be the vent line. Example, we had a guy leave his vent line plugged the other day on a Fox 3.2, after flying for over 5 minutes it deadsticked. You should have seen the way it had the tank sucked in.
Ed M.

My new ZDZ80 was doing the same on downlines, couldn't hear anything but the prop spinning. The blubbering in the eventual transition when level was the clue, it was way too rich. Only leaning the low end needle saved me. My first 2 flights were dead-sticks due to this.

Talked to Jim Cline (Tartan Guru) and he said that it sounds like the engine is idling lower than the force of the air windmilling the propeller causing it to sound like it wasn't running.
The clue was that the prop was still turning and it didn't burble on transition to level flight.
IT sounds like it might be the problem as it dosen't pick up any speed on the down lines at all. You really have to resist the urge to get on the throttle early to avoid a wing drop on the pull.
Time will tell, Thanks all
V-Snap