Jim, and tibits for the rest of us:
After the tire failure and the subsequent off roading mud and dirt
experience while cross country, I commend you for your pursuit of the
problem which cost you much time, and money. You knew you had a mud
plugged vent, but an experienced guy like you missed the kinked vent
line cause. So what's a normal guy to do?
I had to ponder that we (really me), are always quick to assume an
engine related problem is causing the power loss. You told me about
finding the kink but I still assumed that you had a carb problem. You
cleared the clogged vent, but who would have thought about the rest of
the vent system and a possible kinked line when the plane has been
flying for years. I am anal about fuel system install and operation,
but once installed, I rarely look beyond making sure there is not
chaffing or leaks.
Added for all of us:
Recently I just finished an extended annual and another fuel tank
replacement / annual in a couple aircraft that I helped customers build
back in 2002 and 2004. Interesting to note that on both aircraft, that
they were past the 5 year hose replacement timeframe (we all dread
that). In both aircraft I found that the vent line was kinked or
compromised. In one of the aircraft when the upholsterer forced the
fabric around the fuel cover he had forced the fuel cover over one of
the polyurethane vent lines and over time the cover pushed on it nearly
flat so it barely vented properly, and on the other, the vent line was
perfect looking, but the hose was horribly brittle because the vent tube
was made from clear Tygon tubing. Tygon is supposed to be completely
impervious to fuel related problems. Duh, maybe not...
In my old Europa Operators Manual there was the requirement to pull the
fuel bosses off and flush the tank annually, which is quite tough, but
never to check our vent system, and in the new ops manual, it only
indicates to check and inspect for leaks. The 5 year recommendation for
changing hoses is still there, but not the vent lines. Vent lines never
get checked.
As far as I know, you are the first with an underside vent that ever got
plugged, however, you are the only mono I know of with the vent on the
bottom and operate off of grass a lot. In the trigear the vent on the
bottom is always clean, but your point of the oil overflow on the right
side of the cowl exit and a centrally located vent will be a potential
problem for oil, grime and dirt. I'll have to admit I will make sure my
annual checklist is changed to check the vents.
I prefer not to vent out of the top because with the motor glider in
turns when trying to soar, the fuel sprays out of the vent in right
turns. It also will vent fuel out if overfilled on a hot day in Florida
and let set in the sun (especially a mono), which of course can ruining
the paint.
Inspecting an aircraft is not an exact science. Manufacturers and
regulating agencies give only vague guidance. We are the manufacturer
as the builder, so we set the guidelines for inspections of our
aircraft, and if the kit manufacturer gives guidance, we the
manufacturer of the aircraft should be more specific, not less to
include info on our added systems, changes, modifications, and
additional wear areas or time change items due to all the above. I'm in
the US, and have my A&P use the FAA FAR 43 Appendix D as well as the
engine 100 hour checklist and I insist on him using the Kit
Manufacturers guidelines such as the Appendix E of the build manual and
Section 8 of the Ops manual when inspecting an experimental aircraft.
Now, I have been accused of doing a complete rebuild instead of an
annual inspection, but I am anal so that is my excuse, but on an
experimental aircraft (especially one I didn't help build or maintain) I
have found that there are many non standard items, routing conflicts
between wiring, fuel lines, brake lines and control cables, as well as
poor installation of equipment and structural construction mistakes that
the builder and final FAA inspector missed on the initial Airworthiness
Inspection. The FAA actually requires us, as US Experimental Aircraft
Manufacturers, to have established maintenance and operations
procedures.
I am attaching my personal annual inspection checklist out in the open
to show what we the builder can do to improve the inspections on our
aircraft. I only just added an item to inspect the fuel vents since you
called me about the problem weeks ago. I developed this checklist long
ago, before becoming a Europa owner and just tailored it to include
items in the Europa Section 8 inspection, the FAA and LAA recommended
guidelines etc. I am preparing to submit some of this info in a
condensed fashion in an updated Tech Support section of Europa's Website
as well as some other notes we all should know when maintaining the
Europa. Now this is my personal checklist, not for general
dissemination as a Europa Directive, but provided for others to see that
an annual inspection is not a walk around. But then again, it is not an
IRAN (Inspect and Repair as Necessary) like the military does by
completely disassembling every panel, inside and out, instruments,
wings, engine, etc. and inspect, refurbish, service and repair all the
above, it is however, more than a quick check for wrinkles in the skin,
change the oil and sign it off.
Great job of troubleshooting and thanks for the report Jim. Your
findings and my recent observations have changed my annual checklist for
sure...
Regards,
Bud Yerly
---- Original Message -----
From: h&jeuropa<mailto:butcher43@att.net>
To: europa-list@matronics.com<mailto:europa-list@matronics.com>
Sent: Monday, December 31, 2012 2:55 PM
Subject: Europa-List: Re: 914 surging/loss of power
<butcher43@att.net<mailto:butcher43@att.net>>
An update, fuel tank vent restriction.
We trailered our Europa home from Colorado and commenced with the
annual condition inspection. As part of that, we sent out the carbs for
overhaul - no problems noted. We replaced all the 4mm turbo control
hoses per the 5 year requirement - no defective hoses were found. The
carb sockets were updated to the latest specification 2 years ago and
inspection showed no cracks. A few hours prior to this trip we had
inspected all fuel filters including the ones in the electric pumps. No
debris was found - we haven't had debris in the filters in several
years.
What we did find were restrictions in the fuel tank venting system.
The result of these restrictions is that the fuel flow was limited to
the amount of air that could get by the restrictions which was way less
than 5 to 6 gallons per hour that we normally use at cruise!
We have a modified fuel vent system, similar to that described on
Custom Flight Creations website. The tank vent (Tygon SE 200 fuel line
tubing) leads to the top of the cobra where it is connected to the
cobra. From the top of the cobra, a vent line (more Tygon SE200) goes
over the head of the cobra to the belly of the fuselage. The sight gauge
vent and long range tank vent join together and go over the top of the
cobra independent of the fuel tank vent. All three vents join together
a foot below the top of the cobra and then a single tube goes to the
belly vent. The vent on the belly is fabricated similar to the build
manual instructions for the original factory vent on the top of the
fuselage - it is a piece of 1/8" tubing bent to face forward into the
airstream and has two 1/8" bypass holes in the rear in case the main
opening gets clogged.
In Colorado we discovered the belly vent was packed full of debris.
There was even debris sticking out of one the bypass holes. We managed
to clear and clean that vent tube using carb cleaner in an aerosol can.
We did this before the test flight. It was really plugged because it is
difficult to access on preflight and difficult to tell if it has debris.
In our case we hadn't blown it out in several years and between a
little oil from the engine and operating mostly off grass strips a oily
mess accumulated. We have added cleaning the belly vent with aerosol
cleaner to our condition inspection checklist!
In Colorado we also noticed that the Tygon tubing going over the cobra
looked a little kinked, but figured it hadn't changed or gotten more
kinked during this trip. But now we think that it did. On this trip we
filled the tank all the way up into the neck of the cobra to have the
maximum amount of fuel on board. We also added a quart of oil about 10
hours before all these problems - but that actually overfilled the oil
tank and caused it to blow by and out the oil tank vent onto the belly
of the airplane helping plug the fuel tank vent. With the belly vent
blocked or nearly so, there was very little air available to replace the
fuel being drawn from the tank, so the air space in the top of the tank
and in the vent line was being put under vacuum which caused the tygon
tubing to kink more.
We did one test flight in Colorado and the engine ran normally.
However that was after using a few gallons of fuel doing all kinds of
ground tests, so there was more air space in the fuel tank and the tank
walls could collapse a little. But we topped up into the cobra again
before our last departure and subsequent precautionary landing.
So we have replaced the tygon tubing with aluminum tubing over the
cobra head to prevent kinking in the future. We also moved the return
line from the fuel regulator from the bottom of the fuel tank to the top
of the tank because our tech adviser advised that certificated aircraft
do not return fuel to the bottom of the tank.
We've only made a couple test flights since (runway is snow covered
now) but they were normal.
The big learning experiences: be sure the fuel tank vent on the belly
is clear, be sure there are no kinks or restrictions in the fuel tank
vent system and clean the belly tank vent thoroughly every condition
inspection.
Funny how we always thought about the fuel tank vent system in terms
of space for fuel to expand while sitting in the sun and in terms of
letting air out of the tank during refueling, but we never thought about
it's most important job of letting air into the tank to replace fuel
consumed!
Jim & Heather
N241BW
XS Mono, 914, Airmaster
425 hours
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