Daniel,
The 415-CD fuel system is identical to the 415-D. It has separate
lines from the header tank overflow to each wing tank.
It SHOULD NOT have vented wing tank caps. While this should be
corrected, I agree. it is NOT the cause of your RPM
drop.
Check that the engine air filter is passing air properly. Rapid
clogging can occur (from one landing or takeoff) when
grass is going to seed. Check that the throttle cable actually opens
the butterfly fully and is secure and positive in
operation. Have the mixture control plates removed and the holes in
them cleaned.
I would suggest your friend get some plastic tubing of about 3/8" ID
and a 6" piece of copper tubing that will slide into it
securely. Thread this into the header tank filler back as far as you
can and suction out the water and crap that frequently
collects along the bottom at the rear. Undrained condensation can fill
the gascolator and affect the flow of fuel.
Do you have Univair Service Bulletin No. 28 of 10/12/87? It states
that use of 100LL aviation fuel or STC approved auto
gas "may deteriorate the cork float coating and tend to dissolve
sloshing compounds" and that such dissolved coating
and/or slosh "may cause fuel system problems by plugging up strainer
screens and carburetor jets. In the air this can
partially block the header tank outlet flow of fuel to the engine and
dislodge when landing to recur again later.
I would check for debris plugging the finger strainer above the
shut-off valve in the line from the fuselage tank to the
gascolator. Make sure care is taken, as it has probably been a LONG
time since this was done and new valves are not
available. The valve should actually be disassembled, cleaned and
lubricated at least every several years, and operated
now and then to keep it free.
If such debris is the problem, be sure that the wing tank finger
strainers are pulled and cleaned, and the water, etc. is
suctioned out of them too.
When a power problem appears aloft, try carb heat. That bypasses the
air filter. Also try pumping the primer...in an
emergency, that should give bursts of power that can "make the
difference" in landing site choices.
Hope this helps,
WRB
--
On Apr 19, 2009, at 20:26, Daniel Arditi wrote:
William:
Thank you very much for such a detailed explanation.
You wrote:
Daniel...your picture (see below) appears to show a header tank cap
that once had a forward facing vent
hole that has been plugged. Is the gauge wire clean and smooth...no
accumulated deposits, and the hole
it moves up and down through free and clear?
I think so. Yesterday, when I took the photograph, I had the
opportunity to check if the wire moves smooth and free and it seemed
to be OK. As I wrote in a previous mail, a friend of mine has
experienced some problems in his coupe, the one I took the
photograph (a 415-CD) and nobody know what caused the problem. We
consider it a mayor issue as an important RPM fall occurred during
take off followed by an emergency landing. This happened in two
opportunities, after that, the plane was on ground. I personally saw
all the vents, and except that of the fuselage tank that as you said
is plugged, the two other are OK, with the vents oriented forward. So,
venting seems not to be the cause.
What we are trying to figure out, is why the engine experimented the
RPM drop when climbing, just after take off.
Another thing to consider is that after the emergency landing, once on
the ground, the engine worked well. What we are now thinking, is that
the fail appeared because of an steep angle of climb.
It will be very interesting to know if someone experienced the same
problem before, and if that is the case, why that happened.
I really appreciate all your time and interest in my questions and
problem.
Best regards to all of you.
Daniel Arditi
