Kit Aircraft Modifications

Hello Fellow Modifiers,

I would like to touch base on the importance of being able to check your fuel for water and foreign contamination.

As we all know you have to be vigilant when it comes to checking for water in our fuel systems. This has had an influence on the design of the header tank that is mounted on the cockpit side of the firewall in my RV-10.

I designed the tank such that there was a sloped reservoir at the bottom 2 inches of the cylinder that makes up the tank. The dual high pressure pumps draw fuel from bungs welded an inch or so up the side of the tank. The drain bung was welded on the small flat on the bottom.

This gives me a system where any contaminant has a place to settle below the bungs that supply fuel to the engine. The sloped bottom of the tank directs sediment towards the bung on the bottom.

I have installed an aluminum tube that goes from the drain fitting on the bottom of the tank to a bulkhead fitting at the firewall originally purposed as the fuel supply line to the Lycoming  IO-540. From there, a fire-sleeved braided steel hose attaches to a spring-loaded check valve at the bottom corner of the  firewall on the co-pilot side. I installed it beside the gascolator so that both could be covered by a single access door. This allows an easy check of the fuel system during your walk around.

I have to give Ross Farnham  the credit for most of the design of my fuel supply system. He is installing a twin turbo 6 cyl Subaru in his RV-10 and had already designed a similar system for his RV-6. I like to be able to draw on well proven ideas and installations such as he has.

I have also been working lately on building myself a couple of headsets. I like the in-ear units sold by Clarity Aloft but do not like their prices. I stumbled across some do-it-yourselfers  on the net that have built their own. I will chronicle my experience in building one of these headsets in a future installment.

Keep your wings level!

Dave

Good Morning,

Today I am going to talk about how fuel flow is measured when you install an engine that uses a circuit type fuel system. By saying circuit type I am describing a system that supplies fuel to a pressurized fuel rail then sends unused fuel back to the supply tank after going through a pressure regulator.

In my RV-10, I have low pressure Facet pumps that supply fuel to a header tank. From this header tank the fuel gravity feeds to the high pressure pumps. The high pressure pumps supply the engine fuel rail and the unused fuel is depressurized and sent back to the header tank.

The header tank has an overflow fitting at the top which directs the unused fuel back to the supply tank via the return fuel tank selector valve.

So now we have to be able to accurately determine how much fuel is actually being consumed by the engine.

I approached this by looking at the low pressure side only. I placed the supply  fuel transducer after the fuel supply tank selector valve and before the Facet low pressure fuel pumps. The distance between these two connection points was fairly long which was recommended by the transducer manufacturer. I have the little red cubes.

I then placed the return fuel flow transducer in the header tank over flow line between the tank and the fuel return tank selector valve. Advanced Flight Systems supplied me with a little box that both the flow transducers plug into. The box electronically resolves between the supply and return flows to give an accurate usage.

Both of the fuel transducers were mounted on pieces of aluminum angle and then mounted to the inside of the centre tunnel at a 45 degree angle. They were mounted at an angle to assist any possible fuel vapor bubble in moving past them.

Tomorrow I will discuss the importance of the drain valve in the header tank.

Keep pounding those rivets!

Dave

Good Morning All,

This morning I am going to continue with the articles on the fuel system development. My last article on this subject regarded the gascolator  placement.

Today, I will go through the decision process and design of the fuel valve(s).

In my RV-10 there are the usual two wing tanks as well as an auxiliary tank that I placed in the baggage compartment. This results in three feed lines running to an Andair fuel selector valve mounted to the top of the centre tunnel between the two front seats.

The tricky part of the whole affair though is the fact that Andair doesn’t make a duplex style valve for three tanks. I would have been able to get away with one valve had I not added the auxiliary fuel tank in the baggage compartment.

The fuel system for the LS1 engine requires that the fuel run in a continuous loop with unused fuel from the fuel rails being directed back to the originating fuel tank.

After a few phone calls and pondering how I might get the giant octopus of a triple tank duplex valve in the narrow centre tunnel anyway, I decided on putting dual ordinary simplex valves in place of a more complex duplex valve.

This adds some complexity and unorthodoxy to the operation of the fuel system but in the end, I think that it is not so foreign that it cannot be incorporated into standard cockpit operating procedures.

In essence, the two identical fuel valve handles will always have to be placed in the same orientation. Each handle will be identified. One being supply and the other being return.

I have them both located along the longitudinal axis of the plane and they fall to your  hand on the top of the centre tunnel.

Installation of the fuel piping was actually made easier because of the two locations and in all it made for a very neat installation.

Here is a picture of the two valves as installed.

In the next segment I will talk about the location and installation of the fuel flow transducers.

Have a great flight!

Dave

Hi Everyone,

I bet you all thought that I have fallen off the edge of the Earth! I am sorry that I have not posted in almost a year. That is hard to believe! I have been messing about with a couple of business ideas as of late and between that and my family commitments I have let this blog fall off my radar.

In this post I am going to give you an update as to where I am in the process of building my RV-10 as well as fill you in on the LS1 installation progress.

Today, I cut a huge hole in a perfectly good and completed fuel tank. I needed to do this so that I could gain access to the back side of the inner most rib of the fuel tank. the fuel system for the LS1 requires a return line to the fuel tank so I needed to install a bulkhead fitting in the inner rib.

I purchased a spare set of inner tank ribs a while ago in an anticipation of doing this job.  To gain access to the tank I cut out the middle of the embossed lightening hole. The centre is not punched out of the tank ribs for obvious reasons. I took the largest hole saw I have which is about 3 inches in diameter and cut a hole in the middle of the area I wanted to remove. I then took a smaller hole saw and went around the edge of this circle making holes that went out to the outline I drew on the rib before hand.

I trimmed out as much of the waste material as possible with tin snips and removed the rest of it with a die grinder. Then I filed the hole out to the marked line and sanded the edges and the front of the rib outwards from the hole about an inch.

I took the purchased rib and cut out the whole embossment about 1/2 inch larger than the raised portion. This gives me a lot of surface area for the ProSeal to bight into. This part will be the cover for the hole I made to gain access to the inside of the tank.

I then found a flat spot close to the large hole and drilled a 1/2 inch hole. This is undersized to the fitting which is just under 9/16 of an inch. I then filed out the hole until the fitting just fit through. I did this because I am using an Earls gasket on the outside under the hex head of the bulkhead fitting. This will give me a good outside seal. Inside, I installed the washer and nut to secure the fitting.

Time to mix up the ProSeal. I slathered it all over the washer and nut and onto the inner side of the inner tank rib. This gives an effective double seal of the fitting. I then buttered the ProSeal onto the outer edge of the hole and outboard till I hit the line I drew outlining the cover plate. The cover plate went on after it had been roughed by sand paper and a thorough inspection of the tank was completed. I needed to remove a large amount of drill filings from the inside which was somewhat difficult due to the fact that the ProSeal in the tanks stays somewhat tacky. I had to use a tooth brush to get them out to where the vacuum would pick them up.

After installing the cover and pushing on it until ProSeal oozed out from behind, I applied another layer over the exposed joint effectively giving it a double seal. I had some mixed ProSeal left over so I installed the Andair locking gas cap latch ring in original opening. These caps are beautiful and with the price of fuel they have become a necessity.

My friend Charlie came over this morning and we loaded the wing I completed yesterday onto my trailer and took it to my our hangar for safe keeping. Previous to this I had been storing them in the basement. Another check mark in the long list that is building your own airplane.

The RV-10 has been making steady progress as of late with the lower cowl modifications almost complete and the muffler/header modifications nearing completion. I am planning to have it completed sometime in March or April.

I have been impressed and humbled with the statistics from this blog. I have been consistently getting 5000+ visits per month and this is in spite of my noticeable lack of posting over the past year. I have a whole sheet of bullet points that I need to touch on as well as my daily stuff to post so I have a lot of catching up to do.

Let’s see if I can get something posted a couple of times a week from now on. I would love to hear back from my readers in the future and would like to thank the ones who have posted comments and waited months to hear back from me. I will do better and will try to provide some good information on modifications to any kit aircraft that you may have.

This could be a very informative site for those who choose  to stray from the plans.

See you soon.

Dave

Hello Everyone,

I have been working on the cooling system over the last few weeks and we have made some solid progress. This is probably one of the most important check off items on the road to installing a liquid cooled engine in my RV-10.

Since I last posted we have had an engine test stand constructed and have the engine mounted in it. This is going to serve a couple of purposes. One is the ability to transport the engine to outside shops where work can be performed on it. This means that work can go on in my absence and as I am working 6 days a week right now in my day job it is a tremendous help in keeping the project moving along.

The first thing that needed to be looked at in the cooling system design was the failure analysis of the system as it was designed in the automobile. I did an engine to engine risk comparison looking at specific systems and more specifically sub-systems. In the cooling system as well as the electrical system the serpentine belt was a single point failure mode that needed to be addressed.

To address the failure mode of the single belt it was determined that a dual electric water pump system would be developed. This would be an either/or system where the secondary pump would be switched on if the primary pump failed. Failure of the pump could be gauged through current monitoring or temperature monitoring of the engine. The pump usage would also be alternated to make sure that the secondary would perform when called upon.

After much head scratching and conversation with GM engineers as well as the people from the aftermarket water pump manufacturer it was  determined that the dual electric pumps would be mounted to a manifold that has internal flapper valves to restrict recirculation of coolant when one pump is running.

This manifold has been built and we are now fabricating the mounting brackets for it. It will be mounted low on the firewall on the pilot’s side of the engine compartment.

In conjunction with this dual pump/manifold system we had a good long look at the old pump to make sure that we totally understood its functions before making the decision to remove it. The first thought was that we would remove it and replace it with fittings that attached directly to the engine block.

The more we dug into the pumps functions the more we found that it wasn’t so easily eliminated. The pump performs a number of functions. Temperature regulation via the thermostat,  coolant recirculation to help the engine get to temperature quickly and distribution of coolant to the cabin heat exchanger.

We would have had trouble maintaining these functions if we had removed the OEM water pump so we decided to modify the pump instead. We have removed the impeller and pulley from the water pump housing and by machining entrance and exit ports have converted the water pump into a coolant distribution manifold that retains the functions of the manifold portion of the pump while removiing the actual pumping of the coolant to a remote location where the twin pumps can be mounted.

All of this had to be researched and a plan put together before any effort was put toward fabrication of the actual cooling system components. Fabrication is the easy part! Luckily I have some top notch people working on this system for me and now that the majority of the engineering is out of the way I hope to have the engine back and available for the next chapter in this firewall forward development effort which is getting the dual custom engine management computer system designed, manufactured and tested.

I’ll talk to  you later.

Dave

Hi Everyone,

First off, I would like to hear back from all of those who are following this thread. Drop me a quick e-mail or leave a comment if you are enjoying this topic.

The engine is now being fitted to a spacial test frame that will eventually allow me to run the whole engine/gearbox/propeller system on my trailer. This is going to be very helpful in dialing in the engine and to catch any problems with the system before it is mounted in the plane.

It will also allow us to put a load on the engine during testing to see how the custom ECM set up performs. I should have the basics of the test frame done near the end of the week and I hope to have the whole set-up back to the ECM designer’s shop by the end of October.

Dave

Hi Everyone,

 Well, I managed to get the engine through customs and back home without any troubles. I have taken it to a friend’s shop where he has a forklift and could take it off of my trailer. He is also going to be the guy who builds my engine test stand.

Engine test stand you say! You betcha! I am going to be installing a newly developed dual Engine Control Module in my airplane and I am not going to be testing it in the air. We are going to put some hours on this system to ensure that all of the parameters are set correctly. As well, we are going to get the gearbox installed and put some load on the engine.

I am going to do this by designing the engine test stand to be mounted in my trailer such that the prop has sufficient ground clearance to be run with the engine. We will attach the test stand with bolts to the frame of the trailer and then hook the trailer to the van. I will also put in some stakes and tie the trailer down to them to keep it from hopping around.

I have decided to emulate the aircraft forward of the firewall as closely as possible so that the components used in the test stand will be able to be transferred directly to the aircraft. I purchased the steel for the engine mount yesterday and have begun the process of measuring the mount in my plane so that we can approximate it in the test stand.

I’ll give you more as I get it done and in the mean time I will keep on with the posts describing the work I have already completed.

Dave

Well I did it. I purchased the LS1 crate engine last Monday. I purchased a FAST intake and Nick Williams 92mm throttle body as well and had them shipped to Michigan where I am going to go in a couple days to pick it up. I saved a bundle by purchasing it in the states even though I have a GM discount. I got it for $900 less there. Amazing!!

Here at home I have started constructing an engine test cell. I am doing this because I have a couple of things I want hashed out before I install the engine in my airframe.

The ignition is the primary reason that I want to put some time on the engine in a test cell. We are planning to develope a dual ECM set-up and I want to get some hours on the system before installation in the airframe.

The cooling system is the second reason. I am going to go with a dual electric water pump set-up that will require some engine test time to determine whether a thermostat is required. As well, we need to determine how effective the electric fan will be on the cooling when the engine is operating at various loads and speeds.

All of this is better tested on the ground under controlled conditions rather than in the air. I am determined to improve upon the set-up that Bud Warren is using at Geared Drives. I have decided not to go with the OEM computer, water pump and Bud’s cooling system. All of this will require some validation and I am going to do this the right way.

Dave

I have been spending a lot of time lately thinking through the cooling system and specifically the water pump. On a liquid cooled engine the water pump is a single point of failure. A pump failure means that you are coming down and sooner than you would like.

The other thing that needs to be considered when choosing an automotive engine for an aircraft is that a pulley driven water pump is optimized for a very specific RPM range and that is usually around 1000-2200 RPM. This is where the automotive engine spends most of its operational life.

You want a liquid cooled aircraft engine to flow as much coolant as possible at its cruise RPM and for the LS1 married to a Geared Drives psru that turns out to be about 3300 RPM. This is much higher than the optimized speed of the OEM water pump. If you turn that pump faster you end up simply wasting horsepower and not getting an equivalent increase in coolant flow.

There are a couple of ways around this problem. The first has been used in racing circles for years and that is to under drive the pump by changing its pulley size. This works well when running at cruise speed but unfortunately means reduced flow at idle. This doesn’t bode well for the long taxi on 104 deg. F afternoons in Texas.

The second is to install an electric motor driven water pump in lieu of  the OEM water pump. Meziere makes a  number of bolt on replacement pumps that have an idler pulley built in to maintain your existing belt geometry.

The electric pump accomplishes a couple of things that are positive for automotive engines in aircraft. First, it eliminates the need to physically drive the coolant pump using a belt. This will net you 15-20 horsepower at the propeller. Second is the smoothing out of coolant flow over the entire range of engine RPM. This means that you are getting optimum cooling flow when you are taxiing down to the end of the 12,000 foot runway as well as when you are throttle to the firewall.

There have been numerous instances of automotive engines over temping on the ground while taxiing and I have to wonder whether this inefficiency of the coolant pump at idle RPMs is a contributing factor.

The last bit I am going to talk about today is in regard to redundancy and failure modes as mentioned earlier. I am going to be installing dual electric coolant pumps in my RV-10. The main pump will be mounted to the engine in place of the stock unit. The aftermarket unit from Meziere duplicates all of the hose connections of the stock unit and maintains the belt path and operation. The secondary unit will be run in series with the main unit and will be mounted onto the radiator where the bottom rad hose bung would normally be located.

This will eliminate a major failure mode in the installation of a GM LS1 engine in my RV-10 and give me the peace of mind that I need for the  future flights into IMC that I plan to make after getting my instrument rating.

 Have a great time building and modifying!

Dave

Greetings,

Here in Canada we have to install a gascolator in our aircraft to establish a low point for fuel on the engine side of the firewall. I decided to install one of the Van’s Aircraft designed Gascolators as it wasn’t expensive.

It was challenging to find a place low on the firewall of my RV-10 because of the design of the  engine mount. The mount I am using for my LS1 installation as well as Vans original design have a tube that runs the perimeter of the lower firewall. This meant that I had to devise some sort of standoff that would allow me to mount the unit and at the same time have the drain clear the mount tubing.

What I did was take a chunk of aluminum the same size as the base of the gascolator and deep enough to allow the drain valve extension to clear the mount. I then drilled the block to accept a threaded brass extension which was then threaded into the gascolator. The threaded brass extension was then fed through a hole in the firewall and the gascolator was bolted through the firewall as well.

On the inside of the firewall I threaded an aluminum 90 deg AN fitting on to the brass extension and clocked it to be parallel to an angle brace that runs diagonally across the firewall. I secured rigid flared tubing to this brace and ran it between the output of the high pressure Walbro pumps and the 90 degree fitting on the firewall.

I now have a low point for fuel in the engine compartment and have the drain valves for both the gascolator and the header tank side by side so they can be easily checked for water contamination during the pre-flight inspection.

Thanks for taking this in. I would appreciate your comments on this blog. Please feel free to drop me a line or two.

Dave