Re: N275CH First Flight Q200 Revisited!
Peter Harris <peterjfharris@...>
Jim thanks for explaining how your vent was filled. Even without an aux tank the plans vent fills from time to time but not so bad as in your case so it seems as if the 0-200 setup is safe mainly because it has a fuel bowl. It is not safe with a Posa carb or throttle body with no bowl.
To me it is still a bad thing to spoil supply to the carb fuel bowl by using the plans vent which fills and then does not pass the flow test .The vent is an essential part of the fuel system and yet there is a design fault and no dual redundancy. A second vent would at least provide redundancy.
The fuel splash that I am getting happens only when the main is full and then only once in a while in turbulence and it is caused because I routed the pipe into the fuel return line, another plans fault. It would not be a concern if positioned away from the return pipe.
I agree that a fuel pump adds another level of safety.
<The second problem was my own fault and stupidity. I filled the
header, the main and then the aux. I mistakenly flipped the aux valve
on before take off and the only place fuel could get out was through
the vent/ram air line. This would have happened if this line was
installed in the top or bottom of the fuselage. So installing it on
the top would not have prevented this problem. As long as the aux was
being pumped into the header with the main full, the engine would
have quit. >
<I have no interest in spraying fuel all over my plastic canopy
everytime it overflows.>
<I think a new Q flyer should give serious thought to properly
installing a boost pump. Its during those early hours a lot of these
fuel problems surface. Getting a second chance is a good
Jim Patillo N46JP Q200>
"Peter Harris" wrote:
I had trouble with the plans type vent because it plugs with fuel
when air pressure is equal to gravity (at about 90mph climb). This
caused the Revmaster/Posa to almost cut out. That is why I fitted a
simple short up facing vent on top of the cowl to vent the header
This short vent clears immediately if ever it gets blocked with fuel.
Jim P has also reported a fuel starve problem with the plans vent
affecting the standard 0-200 set up with gravity feed so it must have
almost emptied the fuel bowl in that case. Others may not be aware
that their fuel supply is compromised and does not meet the flow test
when the vent is blocked, and it takes time to clear itself.If you
have a fuel bowl running low it affects the mixture and could cause
power surges as in Jim's case.
I believe the plans vent should be scrapped it is a bad design. It is
very easy to replace it with a short foolproof header vent pointing
I made the mistake of following plans advice to terminate the short
header vent inside the return pipe and therefore I get occasional
fuel blown onto the canopy. The short header vent should be
terminated clear of the return pipe preferably on the passenger side
of the cowl.
The addition of an in-line pump is further insurance in case of a
leak in the fuel cap.
Subject: Re: [Q-LIST] Re: N275CH First Flight Q200
Previous noted from Jim P.
Don't let this mishap deter you. I had a vapor lock at 60 hours
and the engine quit at about 150' off the ground in front of the
tower. I was able to get it around the pattern just as you did
by "pumping the throttle". I discovered the gascolator caused a vapor
lock, I shit canned it and the rest is history.
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