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1. 07:48 AM - Re: Trouble Shooting N912RV (Myron Truex)
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| Subject: | Trouble Shooting N912RV |
Adding my two cents. I found my original fuel pump holding back fuel flow. I
had an inline fuel filter just past the tank switch and fuel pump so I could
see if fuel was actually getting through. I had many issues in the beginning
due to fuel starvation. Never a dead engine but one it would almost go dead
on a steep climb out. Long story is I ran the fuel pump always during
takeoffs and landings and most often just let it run. I changed my fuel
filters every 25 hours. So little fuel flows that the slightest obstruction
will starve these carbs. The other item to check very frequently is the carb
bowls. With a cool engine I carefully pulled the bowls off and inspected for
anything. A piece of junk the size of a coffee ground can put you out of
business when it gets into the thimble size area and then acts like a check
valve. One drop of water in the carb bowl might be there for some time and
then you do a steep turn or climb out and the water then gets slurped into
the thimble .
I had a gascolator on mine in the beginning and I found it contributed to
fuel starvation. I tied my plane to a truck, ran it full tilt until it went
very rough and shut it off. After cooling I could see air in the gascolator
and the fuel bowls were starving. The gascolator is in the field next to my
hangar. I had a pretty good right arm in those days.
It took a long time for me to trust hard climb outs. I would climb out at
about 500 fpm and when a safe altitude was reached I would nose up and push
the throttle and fly right on the edge of a stall trying to pull as much
fuel as possible. That is a steep attitude as all of you know.
Another item that could have caused the issue. If you had a hard landing
before refueling the carb could have been jarred loose and decided to come
undone at the worst possible time.
I lost an exhaust tip once and had to buy one locally that was kept in place
by a clamp. The angle was not great and the pipe bumped my firewall on a
hard climb out. After waiting out a storm on the very last leg of our trip
to Lawrence I hit the throttle and went nose high. The vibrations in the
cockpit were annoying but not causing any issues or so I thought. The engine
went rough, I made a turn and leveled out and made a nice landing with the
engine running smooth as silk. Rex Miller and I were flying our planes and
he came back and helped me diagnose the issue. It seems the hard vibration
probably foamed the fuel in the one carb. I know it sounds crazy but it is
the only thing we could come up with. I moved the exhaust extension to the
best angle it would go and off we went. I didn't do any more hard climbs
during that trip and didn't have any more problems.
Many folks built inspection ports on their cowling but I decided it was just
better to remove the cowling during pre-flight. I could see any tiny leaks
and shake the mufflers to check for any issues.
_____
From: owner-pulsar-list-server@matronics.com
[mailto:owner-pulsar-list-server@matronics.com] On Behalf Of GREGSMI@aol.com
Sent: Thursday, May 17, 2012 8:55 AM
Subject: Re: Pulsar-List: Trouble Shooting N912RV
Bob, did you check the tank vent to see of it was plugged? How about the
breather pipes on the carbs, did you change anything with them? An early
builder decided to extend these to the bottom of the cowl and had engine
failure at 100 feet.
In a message dated 5/17/2012 10:15:46 A.M. Central Daylight Time,
w7ikt@fly-web.us writes:
Trouble Shooting N912RV
Group,
Looking for your experiences or ideas as to why the Rotax 912uls in my
Pulsar failed on takeoff.
Event Description:
I added fuel to N912RV's right tank to bring the total fuel in the tank to
about 6 gallons. I ran the 12v electric fuel pump for about 20 seconds
before starting the engine. I taxied to the runway (about 2 minutes)
checked the mag's at 4000 rpm and left the engine running at 4000 rpm to
bring the oil temperature up to 120 degrees (another 2 minutes). I took off
and climbed to about 50' and the engine ran rough for 3 or 4 seconds then
died completely. Fuel selector was on the right tank and the 12v electric
fuel pump was off. Also the temperature and dew point eliminate the
possibility of carb ice.
Trouble Shooting
With permission from the NTSB and the help of my son and I trouble shot the
loss of power. Note: The N912RV has since been picked up by the insurance
company.
<!--[if !supportLists]-->* <!--[endif]-->Mechanical Fuel Pump was
removed from engine, put in vice and pumped fuel from jar A to jar B.
<!--[if !supportLists]-->* <!--[endif]-->The 6 gallons of fuel in the
Right Tank was lost due to crash damage. However we removed the quick drain
and were able to catch about 1 OZ of fuel, no water in the fuel. Also the
lawn mower has been operating on the same gas both before the accident and
after.
<!--[if !supportLists]-->* <!--[endif]-->We opened up the right tank
above the fuel pickup and found no debris or obstructions by the fuel pickup
elbow. The tank coating was not pealing of flaking off.
<!--[if !supportLists]-->* <!--[endif]-->A clear glass fuel filter
above the engine near the mechanical fuel pump was empty of fuel after the
accident. We were able to blow thru the fuel filter in both directions and
the filter was clean and contined no debris. Also the mechanical fuel pump
when removed from the engine had little fuel also indicating a fuel
starvation problem.
<!--[if !supportLists]-->* <!--[endif]-->We pulled the engine thru 4
compression strokes after the accident.
<!--[if !supportLists]-->* <!--[endif]-->All the fuel lines removed
looked in great shape.
<!--[if !supportLists]-->* <!--[endif]-->We removed the wings to get
access to the fuel selector and 12v. Fuel pump.
<!--[if !supportLists]-->* <!--[endif]-->The fuel selector was
removed tested and operated normally.
<!--[if !supportLists]-->* <!--[endif]-->We were unable to blow from
the fuel filter back thru the 12v fuel pump and fuel selector into the right
tank. Thought we had found a problem, we later found out there is a check
valve in the 12v fuel pump. However after removing the 12v fuel pump (it
got bumped around during removal) we were able to blow thru it in either
direction, check valve was not working. I sent the 12v fuel pump to the
NTSB and they tested the pump and it pumped normally and the check valve was
working normally.
Note the Facet 12v fuel pump was supplied in the Aero Designs Kit. There is
no part number on the fuel pump, only a UL number, 574A, US patent numbers
and the voltage 12v. The instillation instructions describe it as a "Solid
State Electronic Fuel Pump". It is turned on for 15 seconds prior to engine
start. There were early reports of the electric pump and mechanical pump
both on flooding the carburetors, therefore I used 12v electric pump only
before starting and emergencies.
--
God Bless
Bob Heiser W7IKT
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