No tank sump or drain

I?m in the process if building my tank and it puzzles me that there is no tank sump or drain fitting. I?m not criticising the vans design, but I would like to better understand the reasoning for the RV-12 setup.
The questions that come to mind are:
What if you get a bad batch of fuel, with water in it? Normally that would be found straight away with the usual post refuelling fuel sample.
If you have contaminated fuel, how do you drain it off without putting it through your pump, valve, and flow rate sender and gascolator?
Simply draining the tank for removal means getting a funnel and tube into position as you undo the connection. How easy is that?
I?m sure other builders have asked the same questions. But what are the answers? Does real life experience show a sump and drain are unnecessary? Is the RV-12 setup today?s standard and I just missed the reading about the evolution of design?

Rod

The gasolator is where you sump fuel to check for contamination and flush the screen under pressure. When you are filling from hand containers you really should be using a "Mr. Funnel" to filter the fuel a final time before putting it into your tank. Finding contamination in your gasolator means (to me anyway) you have failed "Keeping Your Mogas Fuel Clean 101".

To drain the tank, position a funnel and a container under the gasolator, remove the gasolator drain valve, and turn the pump on. I have had to de-fuel a couple of times. The in tank baffle holes cannot drain the tank fast enough to keep up with the free flowing pump so be patient. Van's supply a cap for the supply line in the tank pressure test kit, so keep it handy so you can cap off the tank after it has drained. I have yet to spill one drop in the cabin.

My 2 C

Since the fuel line has to go up hill to get into the shutoff valve, there is a potential problem. A small amount of water could likely get into the tank line, and maybe stay there for a while. If you get enough, it will get into the gascolator. To me, that would indicate you have a fair amount since I feel the line behind the shutoff valve could still have more in it. If you ever see water in the gascolator, I'd tip the nose down and try to get more out of it.

John Bender

Thanks for your response, Larry and John, This is a topic that should not easily be dismissed

There are 4 fl Oz of fuel in the line between the tank and the Gascolator. I oz of that is between the gascolator and the on/off valve. 3 oz between the valve and the tank.

I measured the vertical profile of the fuel delivery pipe relative to the top longeron. Relative to the inlet of the gascolator, the electric pump is 1? below, the on/off valve outlet is 2 1/2? below and the inlet 4 5/8?below, the flow scan is 2 7/8? below.

The RV-12 will be the first Vans aircraft expected to be fuelled by a variety of methods using various fuels from various suppliers. In my view this makes this aircraft particularly vulnerable to contaminated fuel. Not everyone will be using a Mr Funnell. Much of the fuel will go from gas station bowser to jerry can to fuel tank. Contamination from condensed moisture is a serious risk.

Now for the what ifs.
1 You get water contaminated fuel at a stopover on a trip, You drain check the gascolator without switching on the fuel valve. Will water show up?
2. You land at home field, taxi to near the hangar and shut down. You refuel your aircraft from your jerry cans, not knowing it has water in it. You sample the fuel at the gascolator. You have the fuel valve on, but you only take a sample of 3 oz of fuel. No water shows because the water in the tank has not filled the pipes and reached the gascolator. You put the aircraft away and don?t fly for a few months. In that time the fuel pump, shut/off valve and slow scan are filled with water. Is that ever likely?

Thinking through these and other scenarios, I believe Vans has an issue here.
There are practically no precautions listed in the POH about refuelling.
I could not find in the POH any direction to turn on the fuel valve when you take the fuel sample.
I could not find in the POH any advice to take a minimum 4 oz fuel sample from the gascolator. Even that size sample may not be enough if fuel also drained back down from the FWF pipework.

I would like to be able to refuel my RV-12 and check the fuel for contamination before it gets into the fuel line. If there is just a little water I can drain it off. If there is a lot of water I can drain it off and pump clean fuel through the pump, valve and flowscan before I put it away. How do I do that without a tank sump and drain valve?

One good thing is that fitting a sump looks fairly achievable. You may not even have to take the top off the tank. Getting to the drain valve could be quite a stretch, but I would do it.

I?m not expecting a response from Vans. If they follow their usual policy they will stay out of any debate and the first I will know they agree with me will be when they make and publish a design or POH change. I would probably do the same if I were them.
Please don?t be too long about it though.
Rod

Not official answers but I will try and comment on your well thought out questions...

Ausflyer said:

Now for the what ifs.
1 You get water contaminated fuel at a stopover on a trip, You drain check the gascolator without switching on the fuel valve. Will water show up?
2. You land at home field, taxi to near the hangar and shut down. You refuel your aircraft from your jerry cans, not knowing it has water in it. You sample the fuel at the gascolator. You have the fuel valve on, but you only take a sample of 3 oz of fuel. No water shows because the water in the tank has not filled the pipes and reached the gascolator. You put the aircraft away and don?t fly for a few months. In that time the fuel pump, shut/off valve and slow scan are filled with water. Is that ever likely?

Click to expand...

Question 1 - I don't think the POH ever tells the pilot to turn off the fuel valve. The only reason I know that it should ever be turned off is if you have a fuel related emergency (fire or suspected leak) or doing maintenance.

Question 2 - If the pilot does a proper preflight inspection (in my opinion even more critical if it has sat unused for a few months), I believe the water in the fuel system would be detected.

The system as designed does have a low spot prior to the inlet of the gascolator but the low point is only about 12" behind it. There could only be a very small amount of fuel between the water and the gascolator if there was water in the low portion of the line. I should take very little fuel being drained from the gascolator before the water was detected.

If we can agree that the low point in the system is near the fwd end of the fuel system (right behind the firewall), my con tension is that even if a pilot did not do a proper pre-flight inspection, he would never get to the runway for takeoff unless he also skipped doing any engine warm up and he started the engine already sitting at the end of the runway.

Ausflyer said:

Thinking through these and other scenarios, I believe Vans has an issue here.
There are practically no precautions listed in the POH about refuelling.
I could not find in the POH any direction to turn on the fuel valve when you take the fuel sample.
I could not find in the POH any advice to take a minimum 4 oz fuel sample from the gascolator. Even that size sample may not be enough if fuel also drained back down from the FWF pipework.

I would like to be able to refuel my RV-12 and check the fuel for contamination before it gets into the fuel line. If there is just a little water I can drain it off. If there is a lot of water I can drain it off and pump clean fuel through the pump, valve and flowscan before I put it away. How do I do that without a tank sump and drain valve?

Click to expand...

It would seem to me that anyone who has concerns about the cleanliness (and lack of water) of their fuel, would take proper steps to assure the fuel they are pouring in is free from these contaminants. This has been pretty much standard practice for decades by ultralight operators and the procedures are well known. This would remove most of the opportunity for it to get in there in the first place.

Rod has a very valid concern...

.....as far as I can see. Any uphill running of the fuel line without sumping capabilities is worrisome to me.

Here's why: In the early '80's, during the cold winter, a friend had his Skyhawk quit around 10 minutes after takeoff, with a subsequent pasture landing and a flipover without serious injuries. The cause...an uphill fuel line in the wing root with trapped, frozen water (it was in the 20 deg F range).

His airplane was tied down at his farm strip, outside and it had rained quite a bit during the preceding days.

Is there any way to install the fuel line in the -12 with a continuous downhill grade?

Best,

rvbuilder2002 said:

It would seem to me that anyone who has concerns about the cleanliness (and lack of water) of their fuel, would take proper steps to assure the fuel they are pouring in is free from these contaminants. This has been pretty much standard practice for decades by ultralight operators and the procedures are well known. This would remove most of the opportunity for it to get in there in the first place.

Click to expand...

Rod, Your concerns are certainly valid, but I 100% agree with Scott. The place to stop fuel contamination is before you put it in the tank. I never pour fuel from a hand held can unless the fuel has gone through a strainer. IMHO, Mr. Funnel is a good choice to keep contamination out of your fuel system. The fuel wagon I have has a 12v pump and dual filters on it down to 10 micron, and a water blocker filter. Either way, no fuel enters my airplanes unless it is filtered. The chance for contamination is just too great.


http://www.mrfunnel.com/Mr._Funnel/Home.html

Another maybe

I have thought about putting a "T" below the tank outlet, and have a test port straight down from the tank outlet. You could cut a hole in the inspection plate, and take samples straight below the tank outlet. Would not require a lot of work and would help with testing for contaminates.

John Bender

A Word of Caution!

JBPILOT said:

I have thought about putting a "T" below the tank outlet, and have a test port straight down from the tank outlet. You could cut a hole in the inspection plate, and take samples straight below the tank outlet. Would not require a lot of work and would help with testing for contaminates.

Click to expand...

If you build E-LSA, you may NOT do this before certification. Any deviation from the plans will make the aircraft ineligible for E-LSA certification.

Ausflyer is absolutely correct

All your points are valid.
To assume you will always hand fill your aircraft is short sighted.
If you fly to Oshkosh this year I assume some of you will refuel cross-country.
I know I will.
I have taken the approach that once certified - it will become necessary to correct the myriad modifications to the RV12 to make it a perfect, and perfectly safe aircraft.
I must make this point. Having owned many real aircraft - I will never
consider the RV12 an ultralight. One reason is to overcome the slights I have heard that I am not a real pilot because I had to become a sport pilot.
Guess I kinda got my hackles up...sorry 'bout that!
But I like it when someone stops to think out the possible solutions to problems. I'm not that good - and so depend upon all the help I can get.

Dick

sportkid said:

All your points are valid.
To assume you will always hand fill your aircraft is short sighted.
If you fly to Oshkosh this year I assume some of you will refuel cross-country.
I know I will.
I have taken the approach that once certified - it will become necessary to correct the myriad modifications to the RV12 to make it a perfect, and perfectly safe aircraft.
I must make this point. Having owned many real aircraft - I will never
consider the RV12 an ultralight. One reason is to overcome the slights I have heard that I am not a real pilot because I had to become a sport pilot.
Guess I kinda got my hackles up...sorry 'bout that!
But I like it when someone stops to think out the possible solutions to problems. I'm not that good - and so depend upon all the help I can get.

Dick

Click to expand...

Dick,
I am not sure if your statement about the RV-12 not being an ultralight was related to my comment about ultralight fueling procedures or not...
My statement was not meant to imply I thought it was. I meant it in the context that ultralight operators/pilots have established very effective procedures to prevent fuel contamination and these same procedures can (and should be) used when fueling an RV-12.

As for your statement of "correct the myriad modifications to the RV12 to make it a perfect, and perfectly safe aircraft."

Since the definition of Myriad is...
a large indefinite number; "he faced a myriad of details"
ten thousand: the cardinal number that is the product of ten and one thousand
countless: too numerous to be counted; "incalculable riches"; "countless hours"; "an infinite number of reasons"; "innumerable difficulties";

I think saying a myriad of things need to be corrected is a bit over the top.
No airplane designer (or designer of anything for that matter) is going to make choices that 100% of the users will agree with. The RV-12 is no different.

I also think that you are mistaken to think that with some changes you can make the RV-12 perfect, and perfectly safe. I don't think that is possible.
I don't mean to imply that it is a design that can't be improved upon, but I caution people about making changes. RV builders have proven over and over that there is often hidden factors that do not get detected until long after the modification was made. Something to keep in mind.

Could one of the mathematically-inclined among you please post the number of ounces of fuel that would have to be drained from the gascolator pre-flight to insure there is no water in the low spot? Then the sample can be put back in tank via funnel filter or in the lawn mower.

The same problem

The water would stay in the low spot regardless of how much you sampled. Unless the amount of water increases to the point it will flow past the low spot, you will not get it out unless the plane is nose down, then it will move into the gascolator. I sometimes sample check AFTER flying also for that reason.

John Bender

JBPILOT said:

The water would stay in the low spot regardless of how much you sampled. Unless the amount of water increases to the point it will flow past the low spot, you will not get it out unless the plane is nose down, then it will move into the gascolator. I sometimes sample check AFTER flying also for that reason.

John Bender

Click to expand...

I would think the volume the pump puts out would flush any water / debris out, the problem is using a container with the volume needed to accept the "tube full" of fuel. The standard fuel tester would not be enough if you sampled it just once. IMHO.

Another comment

I would guess that during landing, the nose is low enough that any water in the low points would move forward into the gascolator. That is why I suggested a sample check AFTER flying also. That water should now be in the gascolator I would say. When you first put in fuel, a small amount of water LIKELY would not get into the gascolator. Checking before and after would not be a bad idea I suggest. Should have an idea as to when the water got into the system. Since we have lots of ETHANOL in the midwest, small amounts of water get absorbed and you never see any.

John Bender

suggested POH ammendment

Hello Scott,
Thanks for your comprehensive reply on 22/3
I certainly agree that there is a low spot in the fuel line between the fuel scanner and the on/off valve. But that is just after an even lower and much longer section of the fuel pipe where it is retained by the System Blocks. Plenty of capacity to retain water there.
I do take your point that water missed in a quick fuel drain check at daily inspection will become apparent by the time taxying and runups are done.
I hope you will take my point that a relatively large fuel sample needs to be taken to detect post fuelling water contamination


Scott, I agree experienced ultralight flyers will be on guard for contaminated fuel. But many RV-12 builders are coming from GA ranks, or with no prior building/flying experience, judging from this forum?s contributors. IMHO, the POH should take this into account. I would like to see a POH section along these lines:

?Fuel contamination minimisation , detection and removal
Issue
The RV-12 can use a specified range of fuels. Some fuels, particularly non-avgas from some auto suppliers, or stock from jerry cans, may be contaminated with water and foreign matter.
Contaminated fuel placed in the fuel tank goes through a coarse filter only, and water will not be trapped before it enters the fuel pipes, pump, control valve and flow scanner.
Proper sampling of the aircraft?s fuel requires a particular procedure for the RV-12, as does removal of water discovered in the process.

Fuelling precautions
Fuel should be obtained from suppliers familiar with aircraft fuel purity requirements where possible.
Jerry cans and mobile trailers must be kept clean and in-line filters used where practicable. An aviation grade fuel filter funnel (eg Mr Funnel) should be used in the fuel tank filler neck when any doubt exists about fuel quality.
Fuel should be sampled at the gascolator daily before first engine start-up, and after each refuelling. Fuel should be sampled when the aircraft is refuelled before being left idle.

Fuel sampling procedure;
Fuel tap to ?on? position
Drain a 5 ounce (150 ml) sample of fuel from the gascolator
Examine sample for water or other contamination

Removal of water from the fuel system:
Small amounts of water in the fuel line, up to 2 oz, should be cleared by the sampling process.
If more water is detected or suspected, position a funnel and a container under the gasolator, remove the gasolator drain valve, and turn the fuel pump on. Turn the pump off when about 8 oz of fuel have been captured in the container. Then take another sample of fuel at the gascolator drain hole and examine it for purity. Continue the process till a clear sample is obtained. Clean the thread on the drain valve and reinstall it using thread sealant.?

Scott, for you the issue might seem too obvious to be written this up in this manner, But I think it worthwhile considering the broad appeal of the RV-12. I hope Vansaircraft team will give it serious consideration.

Thanks to the others who contributed to this thread (and whose ideas I might have borrowed)

Rod

Ausflyer said:

Hello Scott,

Scott, I agree experienced ultralight flyers will be on guard for contaminated fuel. But many RV-12 builders are coming from GA ranks, or with no prior building/flying experience, judging from this forum?s contributors. IMHO, the POH should take this into account. I would like to see a POH section along these lines:

Rod

Click to expand...

That sounds like me. GA ranks, low time, new builder and always looking for useful tips like this one. Thanks Rod.

Robert