12.99 Engine induction air

This entry is part 50 of 50 in the series 12 - Engine / Propeller

My CHT’s (Cylinder Head Temperature) run hot.  This is not an unknown issue with a Velocity.  Keeping CHT’s in a manageable is an ongoing challenge with many piston engine aircraft.  Since the engines are air cooled, getting air to flow around the cylinders is key.

So here’s the Velocity engine setup for a Continental IO550 engine.

IO550 Right side view cowl 3

Air enters the upper plenum through the two roof NACA Ducts (upper right of diagram).  This air then moves down around the six cylinders cooling them (and also passes through the oil cooler) on its way to the lower plenum. The lower plenum air is the exhausted through the openings at the rear of the cowling in front of the propeller.

My configuration has one difference.  The engine exhaust is routed aft out the bottom of the lower cowling with fairings around each of the two exhaust pipes.  This is another exit point for the hot, lower plenum air. This should provide better cooling than the standard setup where the exhaust sticks straight down out the lower cowling.

IO550 Right side view cowl 4

One of the first things airplane owners do when faced with high CHT’s is to find and plug any holes in the baffling separating the upper and lower plenum. Those openings will allow cooling air to escape into the lower plenum.  I checked and plugged any holes and made sure there were no large gaps between the baffles and the cylinders.

Now what?

Normally, people look at trying to get more air into the upper plenum.  On a Velocity this can be a challenge that traditional tractor style aircraft don’t have to worry about. On your typical Cessna, Piper or Beechcraft, the upper plenum entrance is at the front of the airplane and it’s wide open. Not so on the Velocity.  Some builders have installed vortex generators on the roof to keep the air attached to the top of the fuselage making it easier to get into the NACA Ducts on the roof.  Some of these VG’s are so big they look like shark fins.

One of the things my good friend Malcolm Collier taught me was to think of cooling air like a length of rope; It’s a lot easier to pull rope out of a space than it is to push it into a space.  If you pull enough air out of the lower plenum, then more cooling air will have to be drawn into the upper plenum (assuming the openings are large enough and there’s no blockage).  To that end, some builders have installed vents on the bottom to provide additional exits for the hot air. But I already had that with my exhaust. I could add these louvers, but I don’t think that’s the solution.

Clearly there’s something else.

The Continental IO550 engine installation in a Velocity is somewhat unique. The induction air intake is unfiltered. While building, I started building a pipe to connect the intake to the lower plenum which would connect to a filter box that was then connected to an intake scoop or duct.  But the space was just too tight and by this point the modifications had piled up and I needed to finish the build and get in the air.  So I elected to stick with the plans.  I did build a small U-turn so the air was being pulled from the front instead of the back.

2014-08-18 _20140818_162112

Then one day during a short, local flight I noticed that I wasn’t fighting to keep my CHT’s down in the climb.  And in cruise they were much lower than usual. Once back on the ground, I discovered that the oil door was open.  I’m guessing that it wasn’t pressed all the way down and it popped open once the engine started. But why would that result in lower CHT’s?

Here’s my theory.  The oil door is located forward of the engine air intake.  I think that the open oil door provided a second air source which went mostly into the engine intake.  With the oil door opening providing induction air, that left more NACA air available for cooling.

IO550 Right side view cowl 6

A quick, back of the napkin calculation showed that the engine consumes about 6.5 cu/ft of air every second.  Which means that 6.5 cu/ft per second of cooling air coming in the roof NACA ducts is being consumed by the engine.  Now I don’t know how to calculate the volume of air coming through the two roof NACA’s.  But every cu/ft would matter.

Now the question is how to fix it.

I’m already in paint. So I would really like to not mess with the cowling.  But I’ve got to create an opening for the engine air.  I thought about making an oil door with a small scoop that fed a square duct on the underside of the upper cowling that then connected to the intake.  But the fuel distribution lines are about an inch from the inside of the cowling. The other problem with that is a scoop sticking up into the air just in front of the prop would disturb the air even more than is already is.

So it would have to be a small NACA duct that terminates just above the intake.  My old “U-turn” intake would have to be replaced with a box-type of intake that would accept the air from the NACA duct.

First order of business is to build the new airbox.  Just like the original U-turn intake, I started with blue foam.  Cut the basic shape on the bandsaw and then using Permagrit files I got it down to the shape I wanted.

IMG_20200407_143418    IMG_20200407_143443IMG_20200408_091254IMG_20200408_091248IMG_20200408_091243

After a test fit, I had to create a couple of… divots to clear engine case bolts and screws from the aluminum baffle at the rear of the engine.


Then the whole thing gets wrapped in duct tape and a few layers of BID to create the final product. Once the epoxy has cured, I poured lacquer thinner down the opening to dissolve the blue foam. Then I just pulled out the duct tape.  The first test fit of the new airbox revealed a problem that I ALWAYS discover: I make the foam blank the size I want the finished piece!  Which means it a little too big.  So rather than remake the whole part, I just ground out the divots and made them a little deeper.


Then I began sanding and filling to make it pretty.  Because that’s how I roll.

Now that the airbox is done, it’s time to start on the duct. Because the engine intake is 2.75″ in diameter, that’s a little less than 6 square inches in area.  So I will want the NACA duct to have at least that large of an opening.  I decided on 4-1/2″ x 1-3/8″.  That gives me a little under 6.2 square inches of area.

Andy Millin’s Excel spreadsheet was used to determine the shape of the duct.

I laid out three layers of BID on a waxed piece of glass. These would be the sides of the duct.  Then I determined where the end of the duct should be and applied masking tape to the cowling and drew out the duct.



I cut the back and sides of the duct and left the front of the ramp attached.


The side pieces of the duct where cut so that they would be too high.  I slid them into the cuts for the side of the duct (I used three layers of BID because it was the exact thickness of the saw blade I used to cut the duct). Stir sticks cut to 1-3/8″ long were used to hold the ramp at the correct angle while the epoxy holding the sides to the cowling and duct ramp cured.


Once the epoxy cured, I trimmed the top and bottom of the side pieces.  I left them longer on the back to create the channel that would feed the airbox. I rounded the bottom side of the duct and applied a few layers of BID to reinforce the duct. On the topside, I used epoxy/cabo to create a small fillet at the bottom of the ramp. While all of that was setting up, I used some leftover fiberglass to create the front and back of the air channel.  Then that was wrapped with BID as well.


After everything had cured, I began sanding, filling, sanding, filling sanding, priming, sanding, filling, sanding, priming… You get the idea. Eventually, it was time to paint. Before that, I did a test fit just to make sure the new duct didn’t interfere or hit anything on the engine.

I was going to paint it myself, but I figured that I would have the guy who painted the lower nose after the front gear sheared off take care of that task. Couple days later, the cowling was done.

Now it was time to figure out how to interface the duct channel with the airbox.  When I started all of this, to allow the duct channel to be able to move in and out of the airbox and also move left/right and front/back, I was thinking of using baffle material as a sleeve.   But the number of parts and complexity became too much.  Add to that, there would be very little left/right and front/rear motion because of where this interface is located. And that it didn’t need to be perfectly airtight.  So I decided to use flexible baffle material to make the interface as airtight and simple as possible.

I mounted the new airbox, installed the cowling (as far as it would go) and marked the airbox where the duct channel hit it. Then I cut a rectangular opening on the top of the airbox.  Put the cowling back on, see where it hits, enlarge the opening, repeat about a half dozen times that now the duct channel slips inside the airbox opening. To be honest, this is probably good enough.  I have about 1/4″ gap on the sides and 1/8″ on the front and rear.  For now, I’m going to fly with it like this.  Then once I’m certain there’s no contact between the NACA runner and the airbox, I’ll revisit the interface again.

One thing that was bothering me about this setup is water.  I remember Malcolm telling me about a guy who put an induction air scoop on the bottom of the cowl (Lycoming engine, as I recall).  One day he was trying to takeoff on a wet runway and the engine kept losing power during the takeoff roll. After a number of attempts, he gave up.  Turned out that water was being kicked up by the nosewheel was being ingested into engine significantly reducing power.  He ended up moving the intake duct off to the side didn’t have any further problems.

So I’m curious if I fly through some really heavy rain will I run into any problems. I asked a couple IA’s and they said if I flew through rain heavy enough to affect the engine performance that I had would be having other more significant issues before the engine became a problem.  Okay… but where to get a more expert opinion?

George Braly is an engine guy who really knows engines. He’s one of the three guys who started GAMI and Tornado Alley Turbo.  We had a chat unrelated to Velocity’s almost 20 years ago.  So I reached out and asked him.  He said that he had run some calculations at one point and that heavy rain shouldn’t be able to introduce enough water as to affect engine operations. He also wasn’t a fan of NACA ducts.  But that donkey was already out of the barn.  But his feeling about the water was good enough for me… Kinda.

I remember my old IA telling me how the intake on a Cessna Caravan works.  The air intake is actually at the back of the engine.  The air enters a duct just behind the prop.  Travels all the way to the back of the engine and then makes a 180 degree turn and enters the turbine inlet. If they are taking off from an unimproved runway or in situations where lots of… non-air material is entering the duct, they can open a door at the 180 turn so that heavy material will continue out the back while the (lighter) air makes the 180 degree turn into the engine.

So here’s what I’m thinking: The airbox slopes away from the engine intake.  I’ll drill some holes at the lowest point in the airbox.  Any excessive water will drain out the airbox while the lighter air will make the 180 degree turn into the engine intake. I’d really like a door that I can open, but that’s a long way to run that cable.  And I’ve already got three control levers besides the engine controls in the cabin (heated air damper, oil cooler damper and parking brake) so I don’t one more to have to find a place for.

Finished airbox painted the same color as the engine.


Installed on the engine.


Cowling installed

IMG_20200506_125344 (3)IMG_20200506_125254 (2)

I was able to go up the other day.  Unfortunately, because of the Saharan dust cloud I couldn’t get over 2,500′ so I had to pull the power back and descend to 2,000′ with the power pulled back so I don’t have a good “apples to apples” comparison flight (normally when I takeoff the power stays all the way in until I hit cruising altitude).  But looking at a past flight with the OAT 15F cooler and the engine oil cooler damper closed (providing more cooling air for the cylinders and induction), my #2 CHT hit 412F on that flight. On my latest flight the OAT was 15F hotter, the oil cooler damper was open and my #2 CHT only hit 397F.  I’m think that with the damper closed that I would have dropped that temp at least 10 to 15 degrees.

So for now, I’m calling this a win.  Once this dust clears out I’ll be able to get some additional data.

So this happened.

This entry is part 10 of 10 in the series 99 - Non-Build Topic

Back in the beginning of March 2018, I was tracking down an annoying oil leak that I determined was from a crack in the oil pan. I removed the oil pan, had it welded and reinstalled.  I was going to do a quick flight around the pattern and then see if the leak was fixed.

On landing after the flight, I picked up a shimmy in the nose wheel. This had happened once back in November or 2017.  I did NOT like it.  I had checked the breakaway tension on the fork and it was slightly low, but within specs.  I inspected the fork and nose strut for any indication of cracks and found none.

I called Scott Swing and discussed the situation.  I was already planning on going down to Sebastian to get main gear booties installed so I decided to go ahead and get a shimmy damper while I was there.

During the first week of December, I spent two days in Sebastian installing main gear booties while Scott installed the shimmy damper.  I can’t tell you how much easier it is to taxi with the shimmy damper!

So I figured my shimmy days were behind me.

Which is why that shimmy on the landing caught me off guard. I immediately pulled the nose off.  Then decided to go around. So I added power, and went around. I thought that maybe I came in too fast.

I considered raising the gear, but I had no idea where the nose gear was pointing.  I knew if it was within about 45 degrees of straight ahead that the nose gear guides would straighten it out. But if it was farther out that 45 degrees, the nose fork could do some damage when retracting.  And even worse, might not be able to extend.  So I left it down.

Came around for the second attempt. As soon as the nose gear touched down, the shimmy returned. And once again, I pulled the nose off. I briefly considered going around again, but decided that wouldn’t accomplish anything. So I planned on holding it off as long as possible.

I thought that I had the nose back on the ground although I didn’t feel it. But a glance at the airspeed showed about 50kts.  So I must have greased the nose down.  But as soon as I touched the brakes, the nose hit the runway.

Training is an amazing thing.

Without even realizing it, while I was sliding down the runway, I pulled the mixture.  I have absolutely no memory of doing that but once I viewed the video, I saw it. The engine, however, continued to run (but just barely).  I eventually realized that the boost pump was still on.

My theory at the time was that the shimmy somehow caused the nose gear to retract.


Because I’m at a very small airport and it was about 7am, the place was deserted. I ran over to the airport office (My plane was blocking the runway) and got the airport maintenance guy.  We grabbed the engine hoist that I used when pulling the oil pan, hooked up to the back of his truck and went out to retrieve my plane.

Now at this point, I was thinking that all I needed to do was raise up the nose, and pull the gear down, slide in the overcenter pin and we could tow it back to the hangar. But I’ve got a hidden latch that has to be accessed from the nose gear opening. Which I couldn’t do because it was sitting on its nose.

So we put a sling around the nose and hoisted it up enough to unlatch the nose hatch. When I opened the hatch, I was dumbfounded. THE NOSE GEAR WASN’T THERE!

The nose compartment was empty!  I also noticed a spot on the leading edge of the left wing where the paint and filler were missing. I guessed that during the shimmy, the nose gear departed, flew off to the left, impacted the leading edge and then continued on.

But we had to get the airplane off the runway. So we took 2×4 and wedged it in the nose compartment, wrapped a strap around it and lifted up the nose. Then I sat on the tailgate to keep the plane somewhat stable while he drove to my hangar. About 15 minutes after the nose began scraping along runway 36, the plane was back in the hangar.

Then we drove out to find the nose gear. I found it on in the grass on the left side of the runway about 500’ from the end of the runway.

Let’s go to the tape: Video.

I couldn’t identify anything out of the ordinary in the landing (other than the shimmy). But on the second landing attempt, I believe that I can hear the “BANG” when the nose strut broke off. Definitely not something I enjoy watching.

I called Scott and discussed the “event”. The strut sheared off right at the bottom of the gusset.  My plane has an older style “Taco” gusset. It’s a piece of steel that is folded over on either side of the strut.  The current struts use a much longer, solid gusset. The best guess is that when the first shimmy occurred, an unseen stress fracture was created. It’s possible that the fracture caused the shimmy.  Or the shimmy could have been caused by an out of balance nose wheel which then weakened the strut enough that it broke. Unfortunately, there’s no way to know for sure. What I do know is Velocity changed from the old Taco Gusset struts to the new style for a reason.


The nose strut was broke just below the gusset. I checked the strut thoroughly and could not see anything which provided any clues as to what causes the shimmy or what caused the break.



The bracket which holds the pin for the shimmy damper was broken. But that either happened from the shimmy or impact after the strut broke away.  It was not like that before the flight.


The bottom of the nose was depressing.  I had gotten the plane painted less than a year ago! The bottom was flat as a pancake. The outlet for the oil cooler was ground down flush. The rear arm of the left gear door broken, but the canard bulkhead was undamaged and there was no structural damage.


The left door had a broken hinge arm that would have to be replaced.


There was also some damage to the top of the cowl at the prop opening and to the spinner.  When the nose dropped after the gear departed, the back of the plane (and engine) were moving up.  When the nose hit and stopped its downward motion, the engine continued up a bit. The inertia of the prop moving up and forward caused the spinner to make contact with the cowling.


The leading edge of the left wing took some damage from where the nose gear hit. All things considered, this is much better than had it gone straight back and hit the prop.


Time to get busy:

I pulled the canard, nose gear doors and nose strut that day.  Scott had a new strut gear door hinge arm and shimmy damper pin bracket on the way up that afternoon. I held off repairing any fiberglass until I had the new nose gear hardware in. I also left the gear pivot brackets alone hoping that the new nose strut would drop right.

Once the new nose strut arrived I compared it to the one I have.



The new style has a single layer gusset and it’s a LOT longer.  It will require opening up the slot in the canard bulkhead to accommodate it.


The first challenges… 1) The top of the new strut would not align with the captivator plate. And 2) when retracted, the fork was offset enough that it was rubbing on one of the guides.  I talked to Scott about options.  He said that I could grind one side of the captivator plate to get it to fit.  Then I could send the strut back down and he could put it in a fixture and bend it so the fork would fit between the two guides.  In the end we decided that the correct fix was to remove the pivot brackets and re-mount them.

I pulled the plates, used a soldering iron to heat up the bushings and got those out. Then it was like I was back in Sebastian a couple days after I bought the kit when I was installing the nose gear for the first time.  After a while (a long while), I got the nose gear exactly where I wanted it.  Got everything reassembled and did numerous gear cycles to make sure.

I took the nose fork to a local welding shop and they used dye penetrant to check for any cracks that may have resulted from its trip after leaving the airplane.

IMG_20180329_151911 IMG_20180329_151856 IMG_20180329_151905 IMG_20180329_151920


No apparent cracks.

Now it was time to get started on the cosmetic work. I thought about adding a bunch of micro to the bottom of the nose to recreate the curve but in the end I decided that since it’s on the bottom, nobody would ever see it anyway.  And even if they did, it could be hard to tell. So I got the grinder out and removed the finish around the area to give the fiberglass something to bond to.

The oil cooler outlet needed to be recreated.  Malcolm did a real good job of creating that.  So good that the nose oil cooler alone can keep the oil temps down to 140F without a vernatherm. I tried my best to recreate that outlet.

Once that was done, I smeared micro over the exposed foam and covered the area with multiple layers of fiberglass.

IMG_20180328_093742 IMG_20180328_093811

The leading edge on the left wing only suffered superficial damage.  Basically, the filler get knocked off. So that would wait until it was time for the filling task.  The gear doors required a lot of work as well.  The edge where the doors meet was completely gone. So I had to recreate that part of the door.  And the rear hinge arm was gone on the left door so that had to be reinstalled.  I probably spent more time rebuilding the doors than any other part of the repair.

When doing the filler before, the plane was upside down.  So I would be doing this laying on my back.  This was a PAIN!  And it was HOT!  Fortunately, I still had my Hutchins Hustler.  So the sanding phase was quick.  The absolute worst part was the airport is an hour from the house. So I would drive out, sand the filler, figure out where more was needed, spread the filler, then I was done. Total time are the airport was about 90 minutes with two hours driving time.


The leading edge of the wing and the cowling was a walk in the park by comparison.  The spinner was a whole different story.  It’s made of kevlar. So you really can’t sand it because it just fuzzes up. Fortunately, I know Malcolm. And he knows just about everything about composites. Turns out, the fix is super glue. Sorry, isocyanate adhesive. 😉  Once you get the area sanded about where you want it, you cover the area with the glue. After it cures, you do a final sanding and then apply the epoxy and fiberglass. I used a very lightweight veil since I didn’t want to impact the balance too much.

IMG_20180328_143135 IMG_20180328_143143

After a few days of this, I was ready to prime.

At this point, since the canard was out, I made some modifications.  First was to put in bellows around the rudder pedal push rods.  Then I made some baffles around the nose gear pivot.  These mods were to block air from entering the cabin to help keep it warm in the winter. You can read about those here.

The last improvement/modification I made was to install at anti-slop block where the control stick attaches to the aileron torque tube.

As I was getting ready to reinstall the canard, I noticed the copilot elevator had some slop between the elevator and the torque tube.  Turns out that while the insert that the torque tube plate attaches to was countersunk, it wasn’t countersunk enough. That was allowing a little play between the two. The fix was to countersink the insert just a bit more.


Fortunately, I still have some Akzo-Nobel gray and white primer left. So once I had the areas primed in white, it wasn’t too noticeable.


Now it’s time for paint.  I asked Scott about bringing it down there, but scheduling was a challenge and it was going to be kind of pricey.  The shop on the field put me in touch with the guy who used to paint for Gulf Coast Helicopters. The only downside is that there was a bunch of overspray.  So I have a bunch of cleanup and buffing work to do.

In 2006 I had the nose gear on my 182RG collapse after landing in Greensboro, NC.  That incident cost about $60,000 to repair. Around $35,000 of that was engine teardown and a new prop. The rest was replacing/repairing everything else that got damaged. When all was said and done, this “incident” ended up costing me about $1,000 ($550 for a new nose gear parts and about $450 for painting). I spent quite a few hours making repairs, but that doesn’t count… because it’s working on the plane.

Post repair test flights indicate that I must have gotten the nose oil cooler outlet shape right because it’s keeping the oil cool all by itself.

What’s the takeaway?

If you have the old style taco gusset, maybe consider proactively replacing it.  I know there are still many out there, so I can’t say that this is a necessity. Inspecting the nose gear leg doesn’t seem very useful. After the shimmy in November, I looked at the gear leg carefully.  As did Scott. But nothing was found to indicate a problem. So I’m not sure there’s a good lesson to be learned other than when the nose hits the runway, GET ON THE BRAKES… HARD!  Had I done that, I think the damage to the nose would have be much less.




8.99 – Cracked wheel

This entry is part 8 of 8 in the series 08 - Wheels / Axles

During the annual condition inspection this year, I was tightening the three screws which hold the brake disc onto the wheels.  One of them was not tightening.  I thought that maybe I had stripped the head.

Turns out the threads in the wheel are what got stripped.

I called Matco to see if a helicoil was an approved fix. While waiting for a callback from an engineer, I pulled the wheel because whether I could use a helicoil or had to replace the wheel, it was going to have to come off anyway.

Once it was off, I looked at the hole and decided that replacement was the only option.

2018-08-14 IMG_20180814_095147a

The crack around the hole makes fixing it a non-starter.

When I spoke to Matco, they said that if I sent them the wheel that they would replace the half with the crack for $90.

So off it went.

13.4 – More Static Port Fun

This entry is part 67 of 67 in the series 13 - Electrical / Instruments


Well, that didn’t work very well.

Currently I’m back to my original design with some minor changes.  The original static port was bonded in place.  My new one is held in place with an AN bulkhead fitting nut. And instead of .75″ in diameter, it’s 1″ in diameter.  I adjusted the height of the dam behind the opening and by doing low altitude passes over the runway at high and low speeds, I have got the altitude error down to about 10′.  I still get the altitude “drop” when I rotate at takeoff, but the rest of the time, the error appears to be minor.

So I’m calling it done.


The other day during takeoff, I just happened to glance at the altimeter.  Normally, the altimeter is not something you’re concerned with during the takeoff roll.  But just before the wheels left the ground, I noticed that the altimeter was reading 50′ lower than the field elevation.

After reviewing the flight data for the past 30 or so flights, I discovered that the altimeter would go from the field elevation when the plane was stopped to 50′ – 60′ below at 70KIAS.

I thought that I had the static port error taken care of.  But once I saw this, I did a constant altitude, increasing airspeed test.  The GPS altitude should remain constant, but it didn’t.

After thinking about it, I thought that the angle of the fuselage may be a factor.  All the other planes that I’ve looked at have their static ports located where they are perpendicular to the airflow.  In some cases where the fuselage tapers back towards the tail.  But never at the front where the fuselage width is increasing. I think that’s because in that position, the static port could be subjected to ram air.


The location of the static port on a Velocity is where the fuselage tapers to the nose at a 15 degree angle. I think that the airflow may be affecting the pressure subjected to the port. Now it’s possible the boundary layer may factor in here but as I’m not a fluid dynamics guy, I really don’t know.

But here’s my idea. If I could match the angle of the static port to that of the airflow, I may be able to get a null pressure area.


So I put some 1″ aluminum stock in the lathe and got to work. While I was at it, I decided to make another change.  The current port is bonded in place.  So changing it is a bit of a pain. The new static port will be held in place with a nut from a bulkhead AN fitting.

Here’s the new static port:IMG_20180524_180133



And here’s where is gets interesting:


I have created 15 degree “wedges” that will allow the port to be perpendicular to the airflow.

I have absolutely no idea if it will work or not.  After the baby hurricane makes landfall on Memorial Day and moves on, I’ll install it and find out.

Still can’t fly, but I got the static port installed.

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It is oriented to be plumb and aligned with the direction of flight.

7-99 Sealing the Nose Landing Gear

This entry is part 39 of 39 in the series 07 - Landing Gear

One of the biggest comfort issues with the Velocity is heat (or lack thereof). There are numerous methods of increasing the amount of heat entering the cabin.  I won’t go into that here.  Beyond that, the reason for lack of a warm cabin is that the retractable gear Velocity’s are drafty.

In a Velocity with retractable gear, there’s a big opening in the front for the nose gear.  While there are doors which cover this opening when the gear is retracted, it’s not airtight. And when the gear is extended, the volume of air entering through that opening is impressive.

The area under the doghouse at the leading edge of the canard is open to the nose, and all of the air entering the opening for the nose gear. This is the primary path for outside air into the cabin.

Second, that nose gear opening extends aft of the canard bulkhead. Which means air is infiltrating into the keel.  Directly above this opening is where the elevator push-pull tube exits the keel into the cabin.  Some people have fashioned boots to seal the area around the push-pull tube to block this path of outside air entering the cabin. But even then, there are numerous paths from the keel to the cabin.

The final path for outside air getting into the cabin is through the openings for the rudder pedal push rods which go through the canard bulkhead to the bellcrank.

When I extend the landing gear, I am greeted with (literally) a blast of air.  In the summer, it’s welcome.  In the winter, not so much.

Blocking the primary air path has been solved for quite a while by creating an upper bulkhead between the leading edge of the canard and the top of the nose. What I will be addressing is stopping the air through the second and third paths.

For the rudder pedal pushrods, the factory has been using a box which covers the area on the forward side of the canard bulkhead.  I couldn’t use this approach as my oil cooler exit duct if closer to the canard bulkhead than the plans call for.  Fortunately, fellow builder and problem solver Andy Millin came up with a solution.  Grommets (which I would call small bellows type seals). One for each pushrod. These are available from McMaster-Carr for about $15 each.  The part number is 9280K62.  Andy says this can be done with the canard in.  My canard was out for service which made the job much easier. Once I had removed the pushrods and bellcrank, I had to enlarge the holes to accommodate the grommets.This created a bit of a challenge because a hole saw would be the perfect tool.  But the rudder pedals were in the way from the cabin side and the oil cooler exit duct was in the way from the nose side.So here’s what I did:  I took the hole saw bit and put a ratcheting wrench on the hex shaft.  Then a large area washer went over that to give me a larger bearing surface. Wedge the whole thing in position and start turning the wrench.  In just a few minutes, I had two perfectly sized holes.

Hole saw rig:

IMG_20180328_075112 Cutting the holes:


The next task was creating a flat surface for the grommets. Now I could have just globbed on the RTV and stuck them in place. But the holes where close to the edges and I didn’t want any chance of air leaking through.  So I took a piece of ¼” aluminum stock that I had, waxed it up, applied some Resin Research epoxy with cabo around the holes and clamped the aluminum in place. The next day, I removed the aluminum, cleaned up the holes and then I was ready to install the grommets.

Ready to install the grommets:

I could have used screws to install the grommets, but as there is very little tension on the grommets, I used RTV.  Once the RTV cured, I cut the tips of the grommets off and reinstalled the rudder pushrods.


Grommets installed


View from the cabin side:


Rudder pushrods installed


Blocking the air coming through the keel has always been a challenge.  Some have made a boot similar to those found on manual transmission shifters. Over the years, I’ve considered a couple approaches.  The one that I was most hopeful of was similar to what is found on many automatic transmission console shifters. Basically a slotted housing with a flexible, wide area washers.  But because of the size of the opening, I would need multiple wide area washers with slotted openings and that would require guides on the housing.  If I was still in the building stage, I would have explored that further.  But I wanted to get back in the air.  So I went with Plan A.

I had thought about this approach while still building but I abandoned it to get finished. Basically, it’s a pair of supports with baffle material being the final seal against the pivot shaft.  The disadvantage to this method is that there is a gap while the gear is in transit. But when the gear is up or down, it should provide a very good seal.  I took measurements and built up the concept in CAD to get the dimensions and validate the concept.

Here’s what it looks like:


There are two rigid components.  The upper (canard) and lower (floor) brackets.  One thing I did NOT want was one of these coming loose and preventing the gear from extending.  So on the canard bracket, the two center mounting holes go through the canard bulkhead with MS27039 screws and locknuts. Since there’s no way to do through-hole screws on the floor bracket, I used 5 T10 screws.

bulkhead floor

The material for the brackets is 1/8” aluminum.  This is a bit of a challenge to bend, but I didn’t want any possibility of it deforming.  The flexible material is standard 1/8” baffle material which is cut trial-and-error to get a tight fit against the gear leg in the retracted and extended position.

NOTE: I do not think it’s possible to install these with the canard installed. Also, the brackets are a little oversized.  They will require some trimming to fit.  This is intentional since you want a very tight fit to the sides of the keel.

In the first version, I attached the baffle material to the bracket using pop rivets. But I noticed buckling.  So on the second version, I used 1/16” aluminum stock as a backing surface.

I planned on using RTV to fill any gaps between the brackets and the keel but decided to try it out before doing that.

Gear up.  I could have made the floor baffle a little tighter, but then I would run into binding when the gear was down.


Gear down.  Very tight fit all around.  And that’s when it is really needed.


View from inside the keel with the gear up.  A little bit of gap here, but I’m more concerned with when the gear is down.


On the first flight after installing, when I lowered the landing gear, I was a little alarmed at first because I thought the gear wasn’t extending. There was no familiar rush of air when the gear was extending. Before, I could always feel a strong breeze around my lower legs.  Now, the only indication that the gear is down is the drag of the gear and the wind noise from the gear hanging out in the air.

I’m going to have to wait about six months for cold weather before I can claim total success. But at this point it feels promising.



Electronic Ignition

This entry is part 49 of 50 in the series 12 - Engine / Propeller

One of the things I was planning on when I started building was to install electronic ignition.

If you understand aircraft engines, please skip ahead “RESUME HERE” mark. 😉

The spark on aircraft piston engines is provided by a magneto. This is similar to the distributor on an (older) car engine.  The difference is that a magneto is effectively self powered. It generates the spark without any outside power required. That’s why an airplane engine can run even if the master power switch is turned off.

There are two magnetos which are connected to two spark plugs for each cylinder. There are two reasons for this: 1) redundancy and 2) two sparks burn the fuel mixture better than one.

There is also a big drawback to magnetos.  They don’t advance as the engine turns faster. Even car distributors did this. As a result, the timing on a magneto is a bit of a compromise. It’s set so provide adequate spark across the RPM range of the engine.

Electronic ignitions require power to generate the spark.  But they can create multiple sparks when they fire which burns the fuel even more completely.  And they will advance the timing as the engine turn faster.



At the time I started building, electronic ignitions were complicated affairs with multiple boxes and wires and required external power.  I didn’t like that so I was going to go with standard magnetos.  Then I heard about G3i.  This was a really interesting concept.  It used an external box and controlled the spark.  But it used the existing magneto.  Which means, if the box lost power or failed outright, then the magneto would continue operating in legacy mode. The only problem was it was only available in a 12v version. So I made provisions for one in my electrical system design, but waited to see if they would come out with a 24v version.

At the 2016 Sun-N-Fun I stopped at the E-Mag booth.  They had an electronic ignition which was literally a drop in replacement for the magneto. No external boxes!  And… It did not require external power.  It had an integrated generator.  Well sign me up! The owner of the company said that they were currently working on certification. I said I have an experimental aircraft. He said that he could get me one real soon and would appreciate feedback.  I said “no problem”. He said that should be able to get one of his “Non-certified” units in a couple of months.  “Great” I thought.

About a month later, I sent him an email and was told they are focusing on getting certification.  I said I didn’t need a certified unit and he said that they didn’t have anymore non-certified units but that I’m on the list and it should be just another month.  Over the next two years, I would check in and be told “couple months”.

To date, they still aren’t shipping a unit for a 6-cylinder Continental.

At Oshkosh that same year I stopped by the SureFly booth and talked to the owner, Jason Hutchison.  Basically the only difference between his ignition and E-Mag was that he didn’t have a generator integrated in his.  It required a 10amp circuit.  Okay, I can live with that. And it was about the same price as the E-Mag. But I wouldn’t be able to use my existing wiring harness.  He said they would be shipping in… wait for it… a couple months. He gave me his card with his personal cell phone number on the back.

I told him that whoever called me first would get my business. Over the next 14 months whenever I called he said that he was running behind because of whatever.  But he always told me what was holding him up.  And he was very forthcoming.

In December of this year, I received my SureFly SIM6C.

Then I had to get an ignition harness. I had no idea how much one would cost.  I figured a couple hundred.  Turned out to be closer to six hundred. 🙁

But that was for a complete harness (both magnetos).  So if anyone want a right magneto Slick ignition harness for a Continental 6-cylinder, let me know, it’s yours for $300 with free shipping!

I built the airplane but I purchased the engine. Whenever I do anything serious on the engine, I like to have someone that knows engines to work with.  My old A&P/IA from up in Chicago has semi-retired and now spends his time raising cattle and working on airplanes in Tennessee. I told him what I was planning on doing and asked if he would help and he said “Come on up!”.  And up I went.

Pictures of the Bendix magnetos:

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2012-09-15 IMG_20120915_164400

I flew up on Friday morning and at 8:30am we started pulling the old left mag (technically it’s the right mag because the engine is on backwards).  That’s when we started finding pieces of aluminum sheet.  It took me a minute before the light bulb went off in my noggin’ and I looked at the intake ducts on the upper cowling.  To kept the cylinder head temps even, I built a “diverter” to direct the incoming air down onto the cylinders.

2018-03-03 IMG_20180303_115720 It seems the vibration caused it to crack and come apart. So I removed what was left and then we installed the new electronic mag. When it was time to set the timing, Lynn said “we need to find the correct engine position”.  I said, “no problem, I’ve got it marked on the prop flange.” But the new mag wouldn’t fit in that orientation. So we had to re-clock the gear about 20 degrees so it would fit.

New electronic ignition installed:

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The company that did my fuel system adjustments last spring had it all screwed up. So Lynn broke out his gauges and we set the fuel injection system pressures as well.

Once that was done, he hopped in the co-pilot seat and said “Let’s go!”.  You gotta love an A&P who’s not afraid to ride in a plane he just worked on.  🙂

We took off and started climbing. At about 1,000′ the CHT alarms started going off.  It’s amazing how much that diverter helped. I was having a hell of time keeping a couple of the CHT’s below 410. It was very bumpy so we returned to the airport. Once on the ground he asked if I wanted to go to lunch.  I said that I wasn’t comfortable with the CHT’s and that it was probably best if I took off now just in case I had to return.

So off I went.  I made it about 7 miles when I decided to turn around. I had one cylinder that had gone over 420 degrees! When I landed, Lynn asked what I wanted to do.  I said that I had been flying over two years without the diverter so I knew that I could keep the CHT’s under 400 (barely) without it. So that’s not the problem.  My fuel pressures and flow had been too low before he adjusted them, so that’s not it.  Which means it has to be this electronic ignition. So I said that we’re going to have to put the old mag back in.  He agreed.

So off comes the cowling.  I get started on disconnecting the ignition harness while he starts removing the mag.  He mentions that we’re going to have set the timing on the old mag.  I once again say that shouldn’t be a problem since I’ve already got the mark on the prop flange. He comes to a dead stop…  “What?” I ask.

He said “I thought you said that mark was for the new mag?”  I said “Yeah. It’s for setting the timing of the mag.” And then I get “the look”. You know the look.  When you think you know what you’re talking about but you really don’t?  THAT look.

He said “Don, the timing of you Bendix mags is at 22 degree BTC. You told me this new mag is supposed to be timed at top dead center.”  He continued:  “That would explain why the CHT’s were so high. And why we had to reclock the timing gear 20 degrees.”

To say I felt like a idiot would be an understatement.  But that right there is why I like to have someone who knows what they’re doing when I do engine work.

We re-clocked the mag gear, re-installed and re-timed the new mag.  Started up the engine and it ran fine (but it ran okay before so that’s not conclusive). Put the cowlings back on, loaded up and took off again.

This time the CHT’s for the hottest cylinders only sneaked over 410 and I easily got them back down under 400.

On the trip home at 7,500′ (500′ lower than the trip up) with the same OAT, I was indicating about the exact same airspeed (I was hoping for a little improvement) but my fuel burn was .5 GPH lower. I’ve only made one other trip so I’m still gathering data on performance.  After a couple more trips I should be to determine what improvements to expect.

One thing I’m surprised at is the mag check. On other airplanes I’ve flown with electronic ignition, when you do the mag check, the difference between the legacy mag and the electronic mag is HUGE.  The reason (as explained to me) is that when you shut off the legacy mag, you barely notice it because the electronic mag is generating so much spark that you don’t really notice the loss of the legacy mag.  But when you shut off the electronic mag, the old mag is the only thing generating the spark so the engine feels very rough.  I don’t see that with this mag.

When I got back home, I thought about how to make a diverter that wouldn’t crack again. I still have some titanium left over so I decided to try that.  It took a quite a bit of work to get the roll in the back but eventually made it. Hopefully, this one will last a little bit longer.

2018-03-03 IMG_20180303_153854

2018-03-03 IMG_20180303_153903

15.99 – Cabin Heat Control

This entry is part 9 of 9 in the series 15 - Interior

One of the things that I noticed (actually Ann noticed) is that while I have great heat, she doesn’t have that much.  It took me a minute to figure out why.

There are two ports on the duct which carries the heated air from the oil cooler to the hoses that feed it to the cabin. Since the hot air duct is just on the other side of the bulkhead from the pilot side rudder pedals, there is a very short piece of tubing (maybe 1″) that runs from the duct to the opening just in front of the rudder pedals.

But for the copilot side, it runs up to the top of the canard bulkhead, over the copilot side and then down to the floor.

That air is going to want to take the path of least resistance some almost all of it ends up on the pilot side.

So I created some movable covers.

Here’s the hot air port on the pilot side.

2017-10-14 IMG_20171014_104210

With the new cover installed and in the open position.

2017-10-14 IMG_20171014_104730

With the new cover in place blocking the hot air. 2017-10-14 IMG_20171014_104716

With the hot air restricted on the pilot side, it should be forced over to the copilot side. We’ll have to wait for cold weather to see if it works.


14.99 Painting

This entry is part 37 of 38 in the series 14 - Final Assembly / FInishing

Everything has now been painted white.  Unlike before, which was primer, now it’s actual paint!

And boy is it SHINY!  You can read a book in that reflection.

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Scott will start working on the striping next.

Here’s the mask being laid out.


Riley working on the accent stripes.


The end of the mask and accent stripes on the cowling.