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Old 02-14-2020, 11:46 AM
Rrhsch Rrhsch is offline
Join Date: Aug 2013
Location: Oconomowoc, WI
Posts: 62

Originally Posted by Felix1973 View Post
Hello fellow RV-12 pilots:

Yesterday I had an engine failure right after takeoff. I turned around, declared emergency and landed her safely. It was pretty scary though.

This happened at 300ft and all engine instruments were in green. I did do pre-flight and run-up and had no prior indication for that. Ambient temperature was 82 degrees with 70% humidity. I am running 93 auto-gas.

I uploaded a short video of that incident I would like to get your feedback, maybe anyone can determine from sound of the engine what kind of failure this may have been?

I had a similar problem on take off in my 12. I was able to return to the runway under a decreased power setting and level flight. This occurred in warmish weather and after doing a few touch and goes with the engine at full normal running temperature.

I retested the run up once on the ground. Standard run up was fine, however, full power showed the flaw and destroyed my fuel sensor. (High fuel pressure) My hose to the fuel pressure sensor was in contact with the radiator hose which caused the winter blend fuel to boil. I found fuel on the sensor ware the plastic and brass meet.

This may not be your problem or help you, but it is something to check.
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Old 02-14-2020, 12:49 PM
korbike korbike is offline
Join Date: Feb 2020
Location: Loudon, TN
Posts: 6

Originally Posted by arffguy View Post
First of all, a welcome to new member "korbike" as I see this is your first post.

At first Felix, I could not see your video as the number of playbacks were exceeded so I hit "download' and that worked.

Boy! Even knowing the outcome that gave me some pucker factor just watching it.
Thanks for the welcome arrfguy, great site and group, just starting to get the RV bug!
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Old 02-14-2020, 08:34 PM
scottmillhouse's Avatar
scottmillhouse scottmillhouse is offline
Join Date: Apr 2007
Location: Madison, AL
Posts: 324

You don't mention the age of the fuel. One time I filled for a trip that did not happen and with weather it was 3-4 weeks of rain until I flew. At 5000' I had one carb blocked and got in some glider time back to the airport. Flushed with 100LL to fix. I used 100LL for winter or when I would not be flying weekly from then on. Other possibility- a few have had starvation in climb out from having the tank overfilled. Fuel appeared to block the new style filler tube vent. Mine would show reduced pressure in climb out with Dynon Betty yelling about low fuel pressure. Drilling a hole in the filler cap (like the original) as a backup fuel vent took care of it.
Scott- 2020 donation
New RV-7A N579RV, finally over 40 hours... the leash is off
Built RV-12, 328 hours-sold, purchased RV-12 sold, Built RV-9A, 536 hours-sold, Not completed RV-7 sold, Built Kitfox sold
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Old 02-14-2020, 10:32 PM
NinerBikes NinerBikes is offline
Join Date: Dec 2018
Location: Granada Hills
Posts: 388

Originally Posted by PatrickW View Post
Your video was almost exactly what I faced a few years ago. Similar climbout, houses below. Passenger. Same turnback to land on the runway.

In my case it was a broken crankshaft.

Glad you're ok. Your video really creeped me out and brought back some memories.

- Pat

On a new motor E-LSA RV-12? How many hours on the engine? Or was it an E-AB motor not bought through Van's?
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Old 02-14-2020, 11:52 PM
Capt Capt is offline
Join Date: Feb 2017
Location: Australia
Posts: 476

Originally Posted by Sam Buchanan View Post
There are good reasons why mogas is recommended by the manufacturer for the Rotax engines. I've used mogas off and on in the RV-6 for over 15 years and ALWAYS use a Mr. Funnel when transferring mogas from the 5-gal can to the wing tanks. This funnel has a filter so fine it will capture water molecules and eliminates the possibility of contamination from the fuel can.

Highly recommended for our RV-12 pilots even though some ingenuity will be needed to adapt it to the RV-12 fuel filler.

I use a dual filter version on that funnel, I never put fuel in my RV's wings unless it's thru my funnel, peace of mind even though it's a pain and I get odd looks when fuelling!
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Old 02-15-2020, 02:12 PM
Felix1973 Felix1973 is offline
Join Date: Feb 2020
Location: Miami
Posts: 3
Exclamation Investigation part 1

Hello and thanks everybody for the input so far.

Today my mechanic did the first steps in the investigation:

1) Spark plugs: Dirty, we changed all of them.

2) We looked into the cylinder: No damage from potential detonation.

3) Gascolator: clean.

4) Carburetor:

Left side: One float was lower than the other.

Right side: Float bowl was connected with piece of rubber to the heat shield underneath (why?):

5) We then looked at the blackbox data at the time of the incident (at second 30) and observed EGR temperature on the right to plummet.

Does anybody have any thoughts on a root cause and the purpose of the rubber piece?

Last edited by Felix1973 : 02-15-2020 at 04:08 PM.
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Old 02-15-2020, 03:40 PM
HarryL HarryL is offline
Join Date: Jun 2015
Location: Woking UK
Posts: 53

The piece if rubber is fuel tank sealant which Vans specify to put between the float chamber and drip tray - presumably to damp vibration.

I think your problem is that the right cylinders have seen a very rich mixture (hence the black spark plugs) because you most likely have one heavy float which has allowed the carburettor to flood.
Harry Lees
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Old 02-15-2020, 05:17 PM
rjtjrt rjtjrt is offline
Join Date: Mar 2006
Location: Australia
Posts: 757

Originally Posted by aerofurb View Post
One of the Tecnam P2006T (twin Rotax) we had in the UK suffered one engine running rough in the climb. It was repeatable when in the climb attitude.

We found a very small piece of orange FOD in one carb float bowl which looked like it was possibly from the fuel line. Once the float bowl had been cleaned, the fault never reoccurred.

On a Tecnam P2002-JF (single), it suffered rough running at low to medium rpm on the ground, fine above medium rpm. Whilst I was running it, it cleared and I suspect that something was blocking the idle jet orifice in the float bowl but eventually got sucked through the system. Fault never reoccurred.

Whenever I had the float bowls of our 12, I checked to make sure they were scrupulously clean and that the idle jet feed was clear, by tilting the float bowl with fuel in watching that feed area filled and emptied.

One other thought that perhaps Scott may have experimented with. With a rough running 'fuel-starved' Rotax, has anyone eased the choke out to effectively richen the fuel mix and get it to smooth out? Just a thought.
In another thread in 2014 Cactusman referenced an article in RVator about this (use of Choke), but that article seems to no longer be available.
Post is below.

Last edited by rjtjrt : 02-18-2020 at 01:53 AM.
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Old 02-17-2020, 04:50 AM
Azjulian Azjulian is offline
Join Date: Dec 2015
Location: Scottsdale, Arizona
Posts: 169

This is mostly likely an indication that your carbs went out of sync at that point, given that one carb stayed at expected EGT I would say itís safe to say that you donít have a fuel system to the carbs problem. But that you most likely have a problem in the carbs.

I would check that you are getting unrestricted fuel flow through both carb fuel inlets - taking of the foot chamber cover and running the electric pump and measuring fuel flowed in the same amount of time (eg one minute) and comparing the carbs can give you a good understanding of that.

This is highly likely a restriction in fuel flow, which is either in the carb fuel inlet channel, between the seat and the needle valve. Or contaminants in the fuel bowls and/or in the main jet system.

I would also thoroughly clean and lubricated the pistons on each of the carbs and ensure that they are aligned properly ( the rubber gasket has alignment tabs, you and also feel alignment through the inlet throat of each carb.

Additionally I would ensure that you have no cracks in the rubber mating flange (carb to inlet manifold). And check that no leaks are possible on inlet side.

Itís also likely that you can replicate this behavior or at least see it in data you load to savvy analysis by running your engine at WOT on the ground. If a problem exists you will see the EGTs separate (a 40 F difference seems to be normal on most 912ULS I have seen).
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Old 02-17-2020, 09:13 AM
John-G John-G is offline
Join Date: Jan 2012
Location: Northeast Ohio
Posts: 619


If the right side EGT plummeted at the time of your incident, for sure the right side of the engine went rich.

There are only a few things that can contribute to one carb suddenly going rich while the other carb is seemingly just fine.

1. The most likely suspect - one or both of the floats in the right carb have absorbed fuel and are heavier than the published Rotax specification of 7 grams for the pair, causing high fuel levels in the carb bowl, which floods that side of the Rotax engine with fuel.

2. Issue with the needle valve/seat assembly. A piece of crud may have made its way to the needle valve and got stuck between the needle valve and brass seat at the fuel inlet to the carb bowl. Remove the float arm and needle valve and do a close inspection of the needle valve and brass seat. Turn on the master for a few seconds and flush fuel through the carb. Reinstall the needle valve and float arm assembly. Turn the master back on and verify that raising the float arm will easily shut off the fuel with very little pressure needed on the float arm.

3. The float arms are not level – this will contribute to incorrect fuel level in the carb bowl … can be checked by eye … but best to use the Rotax tool/gauge that is used in conjunction with feeler gauges for making an exact adjustment.

4. High fuel pressure - negating the needle valve’s ability to stop fuel from entering the carb bowl. (Unlikely in your case, I should think, because only one carb went rich).

5. A mis-adjusted carb choke on the right carb. Make sure the choke on the right carb is sitting firmly on the metal stop when the choke lever is full in and locked. Verify the choke lever actually locks and holds the choke lever assembly on the stop.

The above five potential issues are the most likely causes of a carb going rich.

Let us know what the outcome is.

Happy flying,
RV-12 Wings, Empennage, Fuselage, Finishing, Avionics and Powerplant kits all completed
Now Flying!!

Dues paid until September 2020

Last edited by John-G : 02-17-2020 at 09:16 AM.
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