First flight

 Incredibly, I started this build at my home on beautiful Badin Lake west of Charlotte, NC in October of 2011.  This bird flew the nest at my home airport in Longmont, CO on May 12th 2026, so I'm hereby claiming the record for the longest build time for an RV-12: 14.5 years.  Time flies.

First flights of aircraft licensed in the experimental category have historically had a comparatively high accident rate, and it's easy to see why.  In addition to physically flying the airplane, a solo pilot is keeping a sharp eye on the engine instruments (oil temp, oil pressure, fuel pressure. left and right cylinder head temps, left and right exhaust gas temps) and on the flight instruments.  After all, this airplane has never been in this situation before, pitched up at this angle at full power for this long.  Did I do all the wiring correctly?  Did I crimp all the fittings on wire ends well?  Did I adequately tighten all the fittings on oil, gasoline and water (yes water) lines?  It's a mental load which can distract from most important task: flying the airplane.

A few years ago the FAA actually did a wise thing by instituting the "additional pilot" program, whereby a second, qualified pilot with experience in that make and model airplane can accompany the builder pilot on the first flight, sharing the work load.  From what I've read, the first-flight fatal accident rate is now zero since the program was started.  My fearless friend and CFI Bill Snodgrass accompanied me.  Bill has over 1600 hours in RV-12s and is intimately familiar with how they should look, feel, sound and smell.  I had planned to fly his RV-12 several times in the days leading up to the first flight in mine, but ended up not having flown at all for four months prior to the first flight.  The rust on my piloting skills was evident.  I had flown his plane for 20 or so hours in the previous year, so I was not completely uncalibrated to the RV-12, but I should have flown just prior to my first flight.

The pic above shows the airplane before the flight.  I know it's considered bad luck to photograph a flight before departure.  I figured if I made a smoking hole in the ground the NTSB could look at this pic and see that all the pieces were there.

The actual flight went well, no heavy wing, all instruments showing what I expeccted.  Rather than start on the first flight-test card, we decided to shoot four landings to a full stop, then pull the top cowl to look for leaks (none found).

Here's the after pic with the requisite RV grin.  It's been two days now and I think I'm still smiling.

I had planned to start the formal flight test yesterday but the wind didn't cooperate.  Phase I flight test will be entirely task based rather than time based as was typical in the past.

The Spousal Unit (my beautiful and talented wife, Karen) had given me strict instructions to not tell her when the first flight was going to occur in order to minimize her worry.  This was hard to accomplish without outright lying.  The day of the flight it went like this.  Her: "You're not going to fly today are you?"  Me: "Actually, I'm thinking about flying tomorrow."  That wasn't a lie.  I was, indeed, thinking about flying tomorrow but planning to fly today, also.

Off topic: Weird Colorado weather

We've had a dry year here on the Front Range, with snow totals and mountain snow pack about 1/3 of normal.  However, a few days ago (May 6th) we had eleven inches of snow over a two-day period which then melted entirely within 24 hours.  Snow in May seems strange to this southern boy.

Airworthiness Certificate

 The final hurdle in this process -- a process which took 15 years and certainly involved blood (several #30 and #40 holes in various fingers and other blood-letting feats), gallons of sweat, and a fair amount of money -- is the Airworthiness Certificate.  Getting this certificate involves, among other things, an inspection by the FAA itself or by a person designated by them called a Designated Airworthiness Representative (DAR).  If the people from the FAA do it, it's free but apparently impossible to schedule.  If a DAR does it, it's expensive but can be done at your convenience.  I had an excellent DAR, Brad Roon, who charged $1000.  Horror stories abound from other builders I know who have gone through the process, so I consider myself lucky.

For the inspection, all cowls and inspection plates must be removed and certain bits of paperwork must be available. The required on-hand paperwork includes aircraft registration, weight and balance calculations, a complete list of service bulletins with dates showing completion, and a few other documents.  Brad provided a list of everything he wanted to see.  He did a very thorough physical inspection of the entire airplane, which made me a bit nervous, but was what I wanted.  I was confident that all was good because I had a superb EAA technical counselor (Dan Berry) doing periodic inspections as everything went together.  Dan was picky (to put it mildly) but, again, that's what I wanted.  After all, this machine, which started out as a collection of parts, will soon carry me into the sky.

Prior to the DAR visit, the on-line AWC application must be completed on the FAA website.  This is an unbelievable PITA, what you would expect, I suppose, from a government website.  Many documents must be uploaded there, including the Maintenance Manual, the Flight Training Supplement and the Pilot Operating Handbook.  Each of these is over 100 pages, and they want the actual documents, not a link to the documents.  I'll bet you $1000 to a dime that no one at the FAA looked at these other than to see that they were there.

One of the things you submit is a request for a test area, a box specified by lat-long coordinates, within which you're restricted for the Phase I flight test.  I photocopied part of a sectional chart for that and included it in my application, with my requested test area marked in red.

What the FAA granted me was much more generous: from Boulder north to Wyoming and from the Rocky mountains east beyond Fort Morgan.  Brad asked me how much flight time I needed for phase one.  For an E-LSA it can be as little as 5 hours rather than the usual 40 hours for EAB.  I told him 10 hours.  No doube it'll take longer.  Phase I flight test as it appears in the PAP provided by Van's is task based rather than hour based.  I'll describe it as it happens.

Another thing that is issued in addition to the Airworthiness Certificate is a document listing the Operating Limitations for the aircraft (OpLims).  These are requested by the DAR and approved by the FAA.  They give conditions under which the airplane must operate: pilot certificates required, what can and can't be done with the airplane, etc.  Interestingly, even though aerobatics are prohibited in the RV-12 by Van's, the OpLims say only that any aerobatics to be done must be demonstrated during phase one flight test.  Hmmm. Also, a lot of verbiage is devoted to talk about not having external things on the aircraft that can be jettisoned during flight.  That lets out any bombing runs.

So with Airworthiness Certificate in hand, all that's left is to re-install all the cowls, covers and plates, then go fly.

Off topic (sort of)

Here's what happens when you're old and you've hung around airplanes since grade school.  Hard to believe it's been 55 years since I got my license.  Time flies.

PAP Section G6-1: Dynamically balancing the propeller

After syncing the carbs I was less than pleased with the amount of vibration present, especially at low RPM. This being the case, I decided to deviate from my previous plan and do the DynaVibe deal before first flight.  I had planned to put this off until after Phase 1 flight test, as many people do, and fly the plane over to Akron, CO to a shop where others I know had done this with satisfactory results. 

The Mothership recommends doing it before first flight, however.  A member of my local EAA chapter 648, Rick Hall, owns the most expensive version of the DynaVibe balancer and offers it, along with his expertise, free of charge to chapter members (he did accept a bottle of Beefeater gin).

Using this device requires attaching three things to the engine: an accelerometer, preferably as close to the engine centerline and as near the prop as possible (shown here nearest the prop hub with the single black wire), a piece of special reflective tape to the back of one prop blade, and a laser pulse counter (the yellow device to the right).  The laser and reflective tape measure prop RPM.  The tach in the airplane shows engine RPM.

The engine is run at low RPM (2500 in the case of a Rotax 912), then up to cruise power (5200 with the airplane static, depending on how you pitched the prop) where the engine will live most of its life.  The DynaVibe then gives an angular location for the temporary stick-on balance weight and the mass of the weight.  The DynaVibe assumes the weight will be on the perimeter of the rear bulkhead for the spinner.  If for some reason the weight must be attached at a different radial location, a simple calculation allows the new mass value to be determined (r1 * m1 = r2 * m2).

I tied the tail to Rick's pickup truck since I'd had the airplane jump the chocks on a previous full-power run-up.  When that happened I feared I had set the prop pitch too fine, thereby producing too much static thrust.  My fears were allayed when I saw the correct static RPM (5200) at rull power.  On one full-power run I did throw off one of the stick-on weights, heard it hit something over the roar of the engine, but could never find it.

This process stretched over two days (due to starting mid-afternoon) but could have been done in two hours if I had been prepared.  I was not familiar with where and how the brackets for the accelerometer and laser attached to the engine.  Turns out I needed two M8 bolts which I didn't have.  A trip to the aviation aisle at a nearby Home Depot solved that problem but wasted time.

The picture at right shows the temporary stick-on weights on the aft face of the spinner bulkhead.  It was necessary to remove the paint to keep them attached at high RPM.

Van's warns against succumbing to the temptation to attach the permanent weights to the existing screws which attach the spinner to the bulkhead.  Instead, a new hole should be drilled in the bulkhead face and bolts and washers should be used to match the weight of the temporary ones.  Being an anal engineer, I calculated the weight of the aluminum removed by the drill (0.1 grams) and ground the required metal off the washers to get the matching weight.  The required weight was 13.1 grams (yeah, I know that grams is a unit of mass, not weight, but irritating though it may be they express weight in grams in Europe where the Rotax is made).

I was initially worried that the existing nut plate or rivets would interfere with the bolt head or nut of the permanent weight, but it turned out to not be a problem.

Shown first is the aft face of the spinner bulkhead, then below it the forward face.  I used large diameter washers for the AN3 bolt to keep the stack short.  Ideally, the DynaVibe would be used again to check the final balance with the permanent weights but this wasn't done.  I'm confident it's good.

PAP Section G-6 - Maintenance manual page 12-7: Carburetor Synchronization

When I sold my Honda CB-750 motorcycle I thought I'd never have to sync carbs again (that ill-handling monster had four carbs).  At least the Rotax only has two. The idea here is to ensure that the two cylinders on each side of the engine see the same throttle opening across the rev range.  This is done by starting with the throttle arm on each carb 0.004 inches from the mechanical stop using a feeler gage, then opening each carb 1.5 turns of the adjuster (clockwise).  The lock nut on each arm is then screwed down, attaching the arms to the two cables.  The two cables merge into one, which is the throttle in the cockpit.  Idle is now set for each carb and can't be adjusted individually with the throttle-stop screws once the cables are locked to the arms.  Adjusting the throttle plate opening of one carb relative to the other must be done with the ferrule adjusters on each cable.  The following didn't dawn on me initially and I learned it the hard way: the friction lock on the throttle plunger in the cockpit must be tightened down before adjustments are made to the ferrules.  This prevents relative motion between each cable and its sheath.  The ferrule only attaches to the sheath, but the cable and sheath must move as one at each carb during ferrule adjustment.  Otherwise it'll screw up the 2.75 inch plunger travel needed in the cockpit to ensure the achievement of full throttle on each carb with the plunger full forward. Francis Miller, who administered my private pilot check ride back in 1969, told me that the origin of the expression "balls to the wall" came from this: propeller, mixture and throttle "balls" all the way to the instrument panel.  I thought it meant something else.  Also, the RV-12 only has one ball.  Returning now to the topic at hand, the Rotax setup is different from anything I've seen in that the carbs are spring-loaded wide open.  The throttle cables allow the springs to open the throttles or pull them closed, a safety feature, I guess, in the event of cable breakage.

In the pic, the ferrule adjuster can seen on the cable at left, the lock nut which secures the cable to the arm on the right, and the throttle idle stop (with orange torque seal) just to the right and below.

The carbs are now mechanically synced and must be tested over the rev range, with adjustments made to the ferrules as needed.  This is accomplished by measuring the manifold vacuum on each side and making ferrule adjustments as needed to balance them.  The vacuum readings can be obtained with two individual gages or a single differential pressure gage (the bast way).

A couple of years ago when I was insanely optimistic about when I'd have the engine running I bought a kit from Aircraft Spruce which included two vacuum gages (which I later found for $20 each at Harbor Freight) and some tubing which was supposed to facilitate hooking everything up to a Rotax.  As I recall I paid a few hundred bucks for this.  Both gages were faulty, but I found them on line under a different name, still $20 bucks.  This rig would have worked, with poor accuracy, but probably good enough.

Fortunately, I was able to borrow a CarbMate, which uses an electronic differential pressure transducer (shown below).  Adjustments are made until the light is centered.  

After some puzzling attempts at a balance I started to doubt the device (couldn't be me, right?) so I rigged up a large syringe (below) hooked up to each leg of first the analog gages and then the CarbMate, exposing both legs to the same vacuum.  Both measurement methods passed the test, each analog gage showing the same reading and the CarbMate exactly in the center of its scale.  I went with the CarbMate.

I already had the syringe on hand since I had used it to test the pitot-static system earlier (discussed in a previous post).

With renewed confidence in the measurement system, I hooked it up to the Rotax.  The intake plenums on each side of the engine are connected by a balance tube which can be disconnected, allowing the two legs of the measurement device to be attached.  Although it's a bit crowded, the pic below shows the hookup.

The two black tubes in the center with brass fittings are the hookup.  The two brass fittings with the teflon thread tape go to the two legs of the CarbMate.  The initial confusing readings were due to a vacuum leak on one of the rubber hoses, easily fixed with a hose clamp.

Once all this was sorted out the process was easy.  Balance is checked at idle and at approximately 3000 rpm, this higher rpm allowing the carbs to get off the idle enrichment circuit.  Mine was perfect at idle (1800 rpm) and at high rpm but showed a slight variation (1/2 of a light on the CarbMate) part way between the two.  I called it good, figuring the engine spends most of its life either near idle or around 5000 rpm.

More Colorado wildlife: I had a few elk in my back yard.

PAP Section G-8: Fuel System Calibration (Dynon)

 In order to calibrate the fuel system in the Dynon software, data points must be taken starting with an empty tank as fuel is added in two-gallon increments until the tank is full.  The software generates a table of gallons vs.voltage output from the rotary resistor hooked to a float which was installed in the tank when it was built (as I recall, construction of the fuel tank was the first thing in the build to earn the characterization Klöster Föken).  This float-type fuel quantity sensor is not to be confused with the mechanical back-up fuel gage (also with a float).  It made sense to do this now since the tank was already empty from the weight-and-balance section.

Step one was to get 20 gallons of ethanol-free mogas in cans. Fortunately, it's available from the FBO here at my home base at KLMO.  So with four five-gallon cans of fuel, I proceeded to fill a two-gallon can and pour it in the tank until all the data points were recorded.  The Dynon looks like this as the table gets populated:

The only problem occurred when I went past 12 gallons.  The system was recording the data points but wouldn't display them.  I tried every way I could think of to scroll down but no go.  I ended up continuing the process, unable to see the voltage values corresponding to the rest of the data points.  When it's all done, you can edit the table and see everything.  The right-most knob then allows scrolling.  The data looks like this:

 

Being an engineer I couldn't help myself so I did a curve fit of the data to be sure there weren't any wonky points.  Looks good.  Amazingly so considering that I filled a two-gallon container ten times, each time eyeballing the fuel level and the two-gallon mark on the container to be sure they aligned.

Next up is the carb sync, coming soon to a browser near you.  In the bigger picture, I've secured a DAR do to the airworthiness inspection but we're dead in the water due to the government shutdown.

PAP Section G7: Weight and balance

In order to perform the initial weight and balance calculations, the airplane must be weighed containing oil and coolant but no fuel.  Since several procedures which came before this required fuel in the tank, the tank must now be drained (an odious task). The build manual suggests removing the gascolator bowl and running the electric fuel pump until all gas is evacuated.  This would be a major PITA, requiring  removal of the lower cowl and four safety-wired bolts.  I opted instead to once again remove the fitting on the gascolator outlet and attaching the device I previously made to facilitate measurement of the fuel flow rate from the electric pump (see previous post).  Worked great with just the upper cowl off.

The build manual says to place 2" blocks under the mains to facilitate leveling of the fuselage, then to adjust tire pressures to fine tune the leveling process.  For the purpose of weighing the three wheels, the blocks make a negligible difference.  On the above pic, LF is the nose wheel and LR and RR are the mains.  I was pleased with the total weight of 735 lbf considering that I have the optional landing light and autopilot servos.  The expected range of values seems to be 735 lbf - 800 lbf.  However, mine is without wheel pants, paint and an interior, other than seat cushions.  I'll certainly add wheel pants and wrap (no paint) later.

For the measurement of the moment arms, however, it's worth leveling.  I used 2x4s (1.5" thick) which was actually a bit too much, requiring a bit of tire pressure adjustment.  I dropped a plumb bob from the wing leading edges just outside of the mains, snapped a carpenter's chalk line, then made the required measurements from that.  Van's datum is arbitrarily 70" forward of the wing leading edge and all moment calculations are relative to this datum.  The empty CG is then easily calculated by recalling something we learned in the first week of Engineering Statics: For a non-accelerating object, the sum of the moments about any point must equal zero.  With my wheel weights (shown on the pic) and arm measurements, my CG is 81.18 inches aft of the datum for the empty airplane.

With the moment arms supplied by Van's for pilot, passenger, baggage and fuel, my no-fuel CG with me in the airplane looks like this:

The CG location is 80.76 inches, well within the allowable range of 80.49 - 84.39 (shown wrong in the notes on my spreadsheet).  As I imagine most people do, I put this in an Excel spreadsheet to make it easy to play around with various fuel and bagage loads.  With 50 lbf of baggage, a 180 lbf passenger and full fuel, I'm behind the aft limit.  I put this spreadsheet on my iPhone and iPad for easy use.

More Colorado Wildlife:  In a first for me, I discovered a half-eaten rattlesnake in my back yard.  The front third and rear third were gone, leaving what I would think would be the best part of the snake for eating, the fat middle third.  I was unaware that any animals dined on rattlesnake, bet it turns out several do.  Number one on the list is coyotes, which I frequently see (and hear at night).  Number two is mountain lions which I've had visit my yard several times (see earlier post).  Third was bobcats, which I've gotten on the trail cam in my yard twice.  Bon Appétit.

I also had a momma bear and cub on my cam behind my house.

PAP Section G6: First engine start

Before the first engine start, a procedure must be followed which purges air bubbles from nooks and crannies, and most notably the valve lifters, throughout the engine.  This is accomplished by removing the spark plugs to allow easy engine rotation, removing the oil return line at the oil tank and providing a clean container to collect any oil which makes it that far, and turning the prop vigorously until a 40 psi reading shows on the pressure readout in the cockpit.  This causes the oil pump to move oil from the tank throughout the engine and back to the now-disconnected tank return line (maybe).  The instructions say that this may take 40 - 60 revolutions of the prop.  As with all things these days, many Ewe-Tube (they're a bunch of sheep, but that's another story) videos exist showing this process.  The best I found is here.

This process can be sped up by capping the oil tank overflow line and pressurizing the oil tank to 10 psi with an air source before turning the prop.  It is claimed that this step is optional and simply speeds things up.  My friend and ace Light Sport mechanic Bill Snodgrass had done this procedure before and had fabricated a rig to facilitate this.  We first tried it without the air pressure and couldn't produce any reading on the oil pressure gage by turning the prop.  With the air pressure, however, we quickly saw an oil pressure of 55 psi and declared it done.  No oil made it to the catch container but Bill said this is normal in his experience.

After the purge, I did a normal "burp" of the system, which is done before every engine start with a Rotax.  This being a dry sump oiling system, oil which leaves the crank shaft, rods and rockers and accumulates in the crank case must be returned to the oil tank.  This is done in a novel way: rather than using a pump the way race cars do, blow-by from the piston rings pressurizes the oil, forcing it back to the oil tank.  After the engine is run and shut down, oil is left in the crank case, making it impossible to check the oil level in the oil tank.  With the engine off and the cap off the oil tank, the prop is rotated in the normal direction until the distinct sound of a flushing toilet is heard, indicating that the oil is now back in the tank and ready to be checked.

Now it's show time.  With my ex-fireman friend Chad Rennicke, complete with fireman's hat, manning the fire extinguisher, I inclined my head a few degrees and said a silent prayer that I had hooked everything up right -- all the wiring, gas line fittings, oil line fittings -- then turned the ignition key for the first time.  It cranked immediately, oil pressure came up, gages looked good, relief flooded over me, then it quit!  Instantly I knew I had forgotten to turn the fuel valve on.  This done, it fired back up and ran great.  No fire, no smoke, no funny sounds.

Incredibly, after working on this airplane since 2011, I feel for the first time that I'm within sight of the end of the build.  I'm ready to fly.