S

sowmach

I'm New Here
this saturday (may 8th, 2010) after an hour flying in my rv-12 i decided to do a second flight
with my son david, it's very hot in here about 31? C,

after the first flight i left the plane in sun light for about 20 min
then when we started the engine everything was just fine, we started takeoff run and
and about 3 seconds after full power (5100 rpm) we lost power to about 4200 rpm

the plane has logged 60 hrs, and this is the 3rd time this happens so i decide to abort takeoff
but keep the throttle wide open to see what happens

i discovered this:

1.-HIGH FUEL FLOW alarm (i have the limit on 7 gph)

2.-RIGHT EGT DROP to 600 degrees

3.-ENGINE SHAKES very bad and goes down to 2500 rpm

4.-REMOVING FUEL PUMP BREAKER engine recovers
but the fuel pressure drops to 2.1 (fuel pressure alarm)
i keep the engine full power for 2 min and runs ok (without the fuel pump breaker)

this failure ALWAYS happens only if i leave the plane after a flight
and do a second flight (15 to 25 min after)

my conclusion

the right carb floods... rotax service here checked the carb and it
seems to be OK they did this twice looking for dirt on the valve but found nothing

we are thinking of some problem with the heat induced from
the oil thank to the carb (which is very close to it)

Alberto Barba
 
We had a similar problem (the aircraft lost some power when the throttle was pushed all the way in after a practice stall and for a go around on a touch and go got a high fuel flow warning on the 180 and a fuel smell). In our case it was a sinking float in the left carb, when they were removed the good one weighed 2 grams and the bad 4 grams. We replaced both floats with new ones and are back to normal. Just another Rotax issue with no support from Rotax and poor quality parts.

Best regards,
Vern
 
I think the Rotax

Uses Bing Altitude compensating carbs just like my Soobie conversion had..These carbs are usually very reliable and support directly from Bing is pretty good.

FWIW

Frank
 
Very Hot

The "very hot" remark makes me wonder if your fuel is evaporating before it gets to the carb...vapor lock. The only way around that is to let it cool off. In Texas, we used to have to run hose water over the wing or wait till morning. Everything would start up fine, even run-up....but full power down the runway it would die.
 
Hi Frank,

The only Bing information was a web site from some US dealer who does not seem to sell parts or at least does not offer anything but overhaul kits on the web site and the only support provided is the offer to buy a $ 11 manual. The only floats we could find were the original part number and the current part is two numbers newer so not so impressed by Bing support from Bing or any of the so called Rotax dealers, as only the one in Calf. even had the old parts and it took 10 days to get them from them.

Van's had no ideas or parts and sent us to Lockwood who thought they may have some in a month or so perhaps.

Best regards,
Vern
 
Power Loss

We had the same problem last month and narrowed it down to the fuel pump. We replaced it and have had no problems since.
Meade and George
RV12N612RV
 
over pressure due to fuel tank vent not venting?? if the electric pump sees for example 1 psi at the inlet it will pump it to the pump spec +1 (i.e. 5 psi+1). Most of the time vent issues result in fuel starvation but it can result in the opposite problem in rare occasions like heat.
 
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