Kit Aircraft Modifications

Hi there everyone. I would like to thank all of you who are tuning in to hear me talk about my favorite pass time. Modifying aircraft to make them more capable, more beautiful and more personal. I just came from my web statistics utility and I was pleasantly surprised at the increasing number of readers. Thank you. When I started this blog I was sure that I had an audience. I am consistently surprised whenever I check the page views.

I would like to ask that everyone out there who is reading this blog on a regular basis to please let one of your buddies know about the site. I would like to expand the readership to a broad base of pilots and owners. The more people we have reading means that there will be more and more input into the blog.

I would also like very much to hear about any kind of modification that you have made to your aircraft. It doesn’t have to be earth shattering or flashy. It just has to be something that you are passionate about. I will have it on the blog in a flash and you will have that 15 minutes of fame that you have always yearned for.

OK, enough about that stuff. Lets get into today’s topic.

Over the weekend I had the opportunity to work on a couple of things. First is Van’s wonderful, high quality, ready to install (NOT!!!!) fiberglass canopy. The second is a modification I’m making to address a weight and balance with the RV-10.

The RV-10 is a four place aircraft. This is an indisputable truth. As such, there has to be a large CG range to accommodate the range of loads from single pilot with full fuel to all seats occupied with baggage. Van’s built the compromise into the aircraft and in my opinion did a fairly good job. Every aircraft is a flying bundle of compromises.

It has been observed that the RV-10 that Van’s uses for demonstration flights usually has a bag of shot located in the baggage compartment when flying with only two pilots up front. The reason for this is that the CG is right up at the forward limit when in this configuration. It has been noted by a number of RV-10 pilots as well as Van’s itself that the aircraft tends to run short on elevator trim authority in this configuration.

Many pilots have resigned themselves to traveling with some weight in the baggage compartment when traveling light. I got to thinking about this and I just couldn’t resign myself to carrying around extra dead weight. At the same time I was reading about many pilots of RVs that have added wing tip tanks or extra cells in the leading edge of the wing. I’m not a big fan of adding extra tanks to the wing without having them re-tested.

So, one day I started thinking about putting in an auxiliary tank in the baggage compartment. Something that weighs in at about 60 to 70 pounds full would be ideal. The extra fuel weight would be beneficial when traveling with just the pilot and passenger. Something that I think I will be doing quite often.

I thought about my typical missions which will be flying the wife and kids to the cottage and using the plane to travel on business. When we are traveling as a family the tank stays empty. When I am traveling on business in an IFR environment the tank will be full.

Now, how do I do it? I decided that a tank that is in the baggage compartment would have to fit forward under the cross brace and up against the rear passenger seats. In this position, I would be able to tie the tank into the cross brace as well as the floor. I decided that there would be NO tank filling within the cabin so I designed the tank to be filled from the Right wing tank.

I initially was going to have the aux. tank filled from the Left tank. That is until I invited Tom Martin, one of my technical advisers to have a look at the concept drawings and diagrams. The first thing out of his mouth was, “Why the left tank?” I said ” I just picked it.” Tom said that because of the predominance of left hand turns in the landing pattern it would be wiser to have the ability to move fuel into and out of the right tank because it is the high tank when coming in to land. Most pilots will select the right wing tank in the pattern because they want the fuel at the pick-up when turning left.

I had to purchase an Andair fuel valve that had the AUX. position. I wanted to be able to feed the engine directly from the Aux. tank as well as have the ability to transfer in and out of it. The fuel lines run along the center tunnel up near the top and run all the way to a section of the tank that protrudes down through the floor.

I had to modify the baggage compartment floor to accommodate a removable panel that would allow access to an area under the floor where the dual transfer pumps, valves and plumbing are located. I want to be able to remove the tank easily for maintenance (15 to 30 minutes work) so I have incorporated shut off valves into the under floor plumbing as well.

This is the way I see the whole thing working. Normally, you would keep the tank full. I am going to be flying the plane solo a great deal so this is the best situation for weight and balance. If we are going to go on a trip where we are going to be loading the aircraft close to the gross weight , I will fly off the fuel from the aux. tank before the flight and we will proceed with the standard 60 gallons.

This thing is a work in progress. I have the fuel plumbing in from the valve to the floor rib at the front of the baggage compartment. The rest is on paper or is sitting on my work table waiting for my attention while I grind and file and sand the exceptional, high quality fiberglass components so that they will fit what is arguably one of the finest aluminum airframes offered in the marketplace.

I will have more commentary and some photos on this topic as I move further along.

Dave

I have been wondering what it might be like to put in a set of Precise Flight Speed brakes in my RV-10. I live in Southwestern Ontario Canada and it gets pretty cool here during the winter months. These speed brakes would let me create instant and controllable drag to get the airplane down quickly without having to shock cool the engine.

There seems to be lots of room in the bays between the wing ribs to install the two units and I imagine that it would be a fairly simple install when building either the standard or quick-build version of the wings. There would be a tremendous COOL factor as well.

I have often thought that it would also be of benefit when you are on the ground in high wind conditions. You could deploy them while taxiing to help control the aircraft better.

From what I have read there are a myriad of situations that would benefit from the use of speed brakes. Many pilots incorporate them into their checklists to ensure that they are used in a regular fashion. Most owners who install the Precise Flight system in their aircraft cannot understand why they didn’t do it sooner. Some even said that they should have put them in before other major upgrades, such is their utility.

There is a great AOPA article called “Lowdown on GO Down” that is very informative on this system as well as spoilers. I found a price on the Lancair website that show the speed brakes listed for US$ 3500.00. This is a pretty penny if you are building on a budget but so is the cost of a couple of “quicker than you anticipated” descents where you do some damage to your engine.

Here are a couple of pictures.

Dave

I came across an interesting throttle set-up installed in Scott Jackson’s RV. I didn’t see which model of RV he has but it’s a side-by-side model. It seems that there are a number of pilots out there that want this kind of arrangement because they have flown for the military.

I have always wondered what it would be like to operate the center control stick with my right hand. Having learned to fly in a Piper and then switching to Cessnas later on, I learned using my left hand on the yoke. It would be nice though to be able to control the aircraft with my dominant hand.

The more I look at Scott’s installation the more I like its simplicity. I think that I will look and see if there is room along the side of my RV-10 to install a second throttle. I will post Scott’s commentary along with some pictures.

Dave

” I’ve tried to keep it as simple as possible by making the left hand throttle connect to the center throttle right at the quadrant. This was possible by making the center-throttle lever extend below the pivot point so that it could be driven by, or drive, the left-hand throttle while the portion of it above the pivot was connected conventionally to the carburetor. Works well. Only problem to date has been a tiny bit of lost motion which I’m tracking down by bushing the pivot and clevis holes in the levers. Time will tell if the left-hand lever is too far aft-presently it’s right in line with the control stick when the stick is vertical. Since the pictures were taken, I’ve cut the left throttle lever shorter so the ex-military throttle grip almost touches the armrest.”

I have been watching in awe the accomplishments of a fellow Canadian as he designs and implements the installation of a turbocharged Subaru engine in his RV-10 project. Ross is the kind of guy that has the smarts and the where-with-all to pull of an engine conversion correctly.

He started in the game a few years ago with an RV-6. In it he installed a turbocharged Subaru EA-22. I was very impressed with the amount of detail and testing that he went through in validating his design and installation. You can see how he did it all in his RV-6A Build Log

Ross has a company that manufactures electronic ignition and fuel injection systems for the racing industry. As such, it only seemed fit that he adapted it to work in an airplane. It is simple and robust and flight proven. You can go to see his products at his Simple Digital Systems EFI home page.

After completing testing the RV-6A it seemed that Ross still had the building bug so he ordered a Van’s RV-10. I have watched his progress intently as he shares the same alternative engine bug that I have. I have especially enjoyed his development of a belly scoop where he houses the engine cooling radiator.

Ross has decided that the RV-10 needed more horsepower. To that effect he rounded up a twin turbo, Subaru EG33, six cylinder DOHC engine rated at 275 hp for takeoff. Isn’t that a mouth full. He has documented all of his fabrication and installation efforts in his RV-10 Build Log.

I would take the time to read very carefully all of the information on his site. there is a tremendous wealth of information available to the builder who is considering an alternative engine and it gives a true picture of the effort involved in creating your own firewall forward package.

Dave

Most people in the aviation community who have met me, either in person or on-line know that I am an alternative engine nut. From day one of my RV-10 project, I have been looking for an engine that would replace the prehistoric IO-540 that Van’s designed the airframe around.

As with most builders I ran into numerous roadblocks when it came to evaluating different engine options. One of the largest problems with the alternative engine market in general is the lack of a suitable firewall forward package. There aren’t many builders that want to put on the engineering hat as well.

Being the closet engineer that I am led me to start putting together a FWF package together for one of the engine / PSRU combinations that I thought would be perfect for the RV-10. The engine mount was the first piece in the puzzle.

I figured that it would be easier to start from scratch when building a new engine mount than to hack the existing one apart to modify it. It being already welded and heat relieved. I was able to get an example of an RV-10 engine mount lent to me by a fellow builder. From this we took measurements that gave us the dimensions of the mount points as well as the design of the structure that the nose gear is mounted to.

I took this information to a local aerospace MIL-Spec welding and fabrication shop. We made a fabrication jig and 2 initial units. This sub-mount is the perfect staring point for the builder who wants to install an alternative engine without having to hack apart the mount they get from Van’s. In fact you would be able to delete the mount from the Van’s Finish Kit to reduce costs.

The new sub-mount is made from the same material as the original and has been properly welded and heat treated. I think that there is are a number of individuals out there building RV-10s that are looking into alternative engines who might be interested in this product it should save them some time.

As happens in the pursuit of alternative engines for aircraft, I ran into too many roadblocks at least on the engine that I was pursuing at the time. I am currently waiting on a very new engine technology to mature in hopes that I will be able to utilize it in a totally new aircraft engine design. It will be designed to exactly fit into the space utilized by current engines and will attach to the existing mount so I have no need for these initial units.

I have 2 of the initial units available and more can be made with some notice. Here are a few pictures of them. You can contact me at davehertner@kitaircraftmods.com if you are interested in acquiring one of these for your project.

Dave

I found what I think is probably the coolest positions lights in the whole universe. Jeff Bordelon has taken some very powerful LED lights and embedded them in a plastic housing that is highly mirrored. It reminds me of the tail lights on many vehicles today.

Here is a couple of photos of the housing that holds the LEDs

What strikes me about this design is its efficient use of actual lighting to do the job. Usually you see this array of LED lights that are attached to a visible circuit board. I find that this is somewhat unfinished looking. This is the first LED set-up that I think has a purposeful design. What a bonus that the inclusion of mirroring adds to the overall efficiency.

Here are a couple of pictures of Chad Jensen’s wing tips with Jeff’s LEDs installed.

I would like to say bravo to Jeff for his fine work. He is offering these for sale on his web site http://www.jeffsrv-7a.com I think that I am going to put these in my RV-10 and there is no doubt that they would look great in your airplane.

Keep building!!

Dave

The other day I was hanging around www.vansairforce.net in the forums and I saw an interesting modification to the spacer holding the fiberglass wheel fairing on the outboard side of the main wheels. The original spacer, which is made from a threaded hexagonal extrusion has had a small number of attachment bolt failures thus far due to vibration. A couple of fellows from Texas have come up with a replacement that looks much stronger. Their names are Russ Davies and Dr. Linnard Griffin.

The picture below shows the old spacer sitting above the new beefier one. They both attach to the wheel nut in the same way but the greater amount of surface area that the new design places against the nut reduces the amount of stress on the bolt.

Here is a photo of the new spacer mounted on the airplane. The slots that are cut in the center of the spacer are there so a wrench can hold the unit while the bolt going into it from inside the nut is torqued.

All in all, I think that this is a great fix for the problem. It adds a little weight close to the CG which might be a problem for people who want the leanest machine possible but I would sacrifice a few ounces in exchange for the piece of mind knowing that my wheel fairings are secure and not prone to failure due to vibration.

Dave

A while ago I came up with a cool little modification that allowed for a better mounting of the Whelen taillight/strobe on my RV-10.

The problem that I heard others were having with the design of the lower rudder fairing was that it was difficult to get the 2 nuts that anchor the aluminum retainer ring epoxied in place. Mostly, this was due to the very cramped area within which you have to work.

I thought long and hard thinking that there had to be a better way to mount this thing. It dawned on me one day that it would be better for servicing the light if it were easy to remove from the plane altogether. The epoxy job tends to make the installation somewhat more permanent.

I got out a piece of 1/4″ aluminum and drilled a hole that was a little bigger than the outer diameter of the Whelen light housing. I transferred the outer retaining ring dimensions to the aluminum and started cutting it out.

I then located six holes around this ring of sorts that were away from the holes that hold on the retaining ring. I drilled these out to 1/8″ and countersank them till there was less than 1/8″ thickness remaining. The diameter of the counter bore was the same as the O.D. of a CS-4 pulled rivet.

I located the retaining ring’s mounting holes on the aluminum, drilled and tapped the holes to accept the machine thread mounting screws. From there I took the unit and cleaned it up and primed it. I placed the unit on the lower rudder fiberglass fairing and centered it in the location I wanted it and drilled out the six 1/8″ holes into the fiberglass and clecoed it on.

I then carefully removed the fiberglass in the center hole out to where it met the aluminum and trial fitted the whole assembly. I then blind riveted the ring to the fairing and installed the light assembly to make sure that everything fit as planned.

This modification worked to solve a couple of problems. First, it made the installation a much easier affair where you don’t have to work with epoxy and in a very tight area. Secondly, it makes the servicing of the light a breeze later on.

I will be making this adapter ring available for purchase in the near future. It is the perfect example of the type of modifications that I want to highlight on this blog.

Dave