Flight test: Card 1

 Since more than 830 RV-12s are flying, quite a lot of knowledge has been accumulated regarding what to expect during flight test.  Van's provides at the end of the PAP (Production Acceptance Procedure) five flight test cards to accomplish Phase I.  It's a task-based approach rather than hours-based and I'm pretty much following what's laid out in the PAP.  It's done just like the rest of the PAP, that being check boxes followed by a description of the task (83 check boxes for the first test card alone).  Some tasks are simply yes/no, OK/not-OK things, others require numbers to be recorded.  The data logging system built into the Dynon HDX helps tremendously.  The system records all flight and engine parameters many times per second which are then downloaded to a thumb drive after each flight.  

All flight testing is set up to be done solo at a specific total weight.  Accurately observing and recording numbers would difficult while also flying the airplane.  Thank you Dynon for providing this terrific data logging tool.  The FAA now allows, as discussed in the previous post, an additional qualified pilot to assist with Phase I, but so far I'm feeling the urge to keep doing it solo.  For some of the tasks I may want a helper, an example being calibration of the AOA gage which requires pushing a button on the EFIS at exactly the stall break while keeping the wings level with rudder.  We'll see.

Before getting into the actual flight test, here are a couple of additional thoughts about the first flight.  I've done eight flights so far (about 11 hours on the Hobbs) and I've gained some perspective.  Here's what I felt I had just done immediately after the first flight:

That's actually Chuck Yeager in a rocket-assisted F-104.  Here's what other people probably thought I had done on my first flight:

The first of the five test cards checks to see that all the sensors, instruments and systems are functioning properly.  Basic flying qualities are evaluated including trim and straight-ahead 1g stalls.  Frankly, considering the complexity of the systems, I'm surprised that everything worked perfectly and the airplane flies so damn well.

After reading the write-ups other builders have done detailing their flight tests, I was fully expecting to have a "heavy" wing as most people do to varying degrees. That's a tendency to roll one way or another with the ball centered and hands off the stick, requiring corrective stick force to counteract the rolling tendency.  No heavy wing.  The airplane also stalls straight ahead with no tendency to fall off on a wing.

Power-off 1g stalls were done with no flaps, half flaps and full flaps.  Because of the surprising numbers I am seeing in the cockpit (confirmed by the data logs) I repeated the stalls in each configuration multiple times on multiple flights.  According to a table in Section 5 of the POH, indicated airspeed and calibrated airspeed (corrected for instrument error) are the same.  Based on my real-world experience, I find this hard to believe.  Theoretically, a Pitot tube would produce about 3.5% error at the AOA seen at stall (~15 degrees) but I've seen larger errors in the lab.  Van's does bevel the end of the Pitot in order to mitigate this, so maybe it's true.  I just had a discussion with a Van's techs support guy at Oshkosh, and he agreed with me and said he'd check.  Strangely, just under the table in the POH showing no difference between indicated and calibrated airspeeds, the very next table shows a difference of about 4 knots between indicated and calibrated airspeeds but with indicated being higher than calibrated for stall speeds in all three flap configurations at a gross weight of 1050 lbf!  This would make my numbers even more amazing. Solo with full fuel, i'm right at that weight.

Anyway, even with a few knots error I'm surprised with the numbers I'm seeing.  Prior to flying my airplane, I had done stalls in other RV-12s, but it was always with a passenger.  For my airplane, built light (735 lbf empty weight), a passenger can easily be 25% of that, having a substantial effect on performance.

Solo, with about 110 lbf of fuel, I'm repeatedly seeing an indicated stall speed of 40 knots with no flaps and 35 knots (!) with half flaps.  With full flaps the number is a bit higher, probably because the nose is bobbing up and down and never reaching steady state.  The static ports are on the sides of the fuselage a few feet behind the aft edge of the canopy and may be in the turbulent wake from the separated flow at the wing root  

Landing, full flaps do add noticeable drag.  Half flaps are apparently magic in this airplane and that's the way I land unless I'm high on final -- something I prefer, slipping off any excess altitude.  This airplane will sink like a Cherokee (what I learned to fly in 57 years ago!) when slipped with full flaps.

The pic shows me sharing the runway with a bird on short final.  My hangar is at Vance Brand Airport (KLMO) in Longmont Colorado, elevation 5040 feet msl.  One of the tasks on the first card involved pushing the nose over until I had 120 knots indicated.  Starting at our field elevation and climbing a few thousand feet to do the tests, my density altitude has typically been over 10,000 feet.  Before doing this, I wondered how close I'd be to Vne (never exceed speed, no doubt based on flutter margins).  Many pilots I've known think Vne is indicated airspeed.  That's a good way to become no longer counted among the living.  Vne is true airspeed, 136 knots on an RV-12.  Fortunately, my Dynon HDX displays true airpseed (along with density altitude) so I kept a close eye on it as I did this task.  As I slowly approached the prescribed speed, at an indicated speed of 119 knots I bagan releasing forward force on the stick.  The computer screamed in my ear "Overspeed, Overspeed."  The data log showed I had reached a true airspeed of 136.1 knots.  I'd like to never hear that again.

Oshkosh 2026  I just returned from my 37th pilgrimage to aviation Mecca.  Although there was a record crowd (around 3/4 million people) it was a bit atypical.  As usual, I got there on Sunday (usually one of the best days for watching arrivals) but smoke from Canadian wildfires kept the airplane traffic low until Wednesday.  It was still, as always, a sensory overload.  Our NASA administrator, Jared Isaacman, flew his personal Mig 29 in.

His personal T-38 was parked beside it.  Looking at his accomplishments, I'd say he's an amazing guy.

First flight

 Incredibly, I started this build at my home on beautiful Badin Lake east 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 (and maybe taste).  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.

There are two schools of thought on first flights.  Some say an actual test pilot should be used because the builder is too heavily invested (emotionally and financially) in the airplane and might try to protect the airplane rather than save himself in the event of an emergency.  To me that would be akin to hiring a professional to stand in for you on your wedding night.

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 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.

PAP Section G4: Measuring fuel flow from the electric pump

It was with fear and trepidation that I poured four gallons of fuel into the tank for the first time, exposing the entire system -- all the fittings from the tank to the engine and back to the tank -- to gasoline.  I had tested the tank itself when I first built it back in North Carolina (see earlier post detailing that particular Klöster Föken), but the rest of system had never seen fuel, much less pressurized fuel.  When I first added the fuel, I did so with the fuel valve in the cockpit closed, limiting the gasoline to about half the fittings with gravity. providing the only pressure (~0.5 psi).  All appeared well.  I then opened the cockpit valve.  Seemed OK. When I switched on the pump, however, I immediately had a leak which I eventually traced to the fitting going to the fuel flow meter.  Tightening this seems to have fixed it.

For the actual measurement of the flow rate, the manual says to remove the fitting at the gascolator outlet, slip a 5/16-inch fuel hose over the fitting, turn on the pump and measure the time required to pump one gallon into a gas can at waist level.  The time is not to exceed 180 seconds.  

The first problem with this scheme is that without completely removing the bottom cowl, which involves detaching the oil heat exchanger from the cowl (a major PITA), the fuel fitting must be accessed from above.  I did remove the piano hinge wires from the lower cowl, allowing it to swing down a few inches with the oil cooler still attached.  With the new RV-12s, the oil cooler is no longer attached to the cowl, eliminating this headache.

The second problem is that a 5/16-inch fuel line doesn't come close to fitting.  The male threads on the fitting measure about 0.55 inch, so a 1/2-inch line fits well.  I used a short segment of 1/2-inch, a right-angle fitting, then the rest 5/16-inch.  The right-angle fitting made it possible to hook it up from above.

The time required to pump one gallon was 170 seconds.  Next up is doing the purge process to get the air out of the oil lines and lifters, burp it, and start the engine!

I recently returned from my 36th pilgrimage to Oshkosh.  The big news at the show was the final publication of MOSAIC, the long-awaited update to the rules governing Light Sport aircraft and Sport Pilots.  It's simple now: any aircraft with a clean stall speed, Vs1, of 59 knots or less can be flown by a person holding a Sport Pilot certificate.  All of Van's airplanes with the exception of the RV-10 qualify.  No medical.  Retractable gear with a variable-pitch prop: check.  Wanna fly a 182 or a Stearman?  You're good.

SB-00102 Control Stick Pushrod Inspection

The purpose of this post is twofold: to document that I have performed this Service Bulletin and to prove to my friends following this blog that I'm still alive and still working on the airplane.  The Service Bulletin was brought about by a fatal accident involving an RV-12 which resulted from improper installation of the rod ends on the aileron push tubes.  Over 600 RV-12s are flying so I guess over 599 builders did it right, but Van's says that "out of an abundance of caution" (seems like I heard that phrase a few thousand times back in 2020) the SB was necessary.

The diagram on the left shows the proper installation and the pic at right shows the improper installation on the accident airplane.  What I don't understand is this:  In the accident airplane, the stick on the right was functioning.  It's not much of a reach to put your hand on it from the pilot's seat.

To verify that did it correctly I snaked my borescope in through the cutout for the right stick and took a pic.

The alternative to this is to remove the floor pan, an odious task which involves removing hundreds of Phillips-head machine screws, half of which have the heads boogered up (that's the official machine-shop term) from five or six previous removals.

Back in 1948, Edward Murphy said "If a thing can be done two ways, one of which results in disaster, someone will eventually do it that way." 

Off Topic:

I'm getting ready to move my antique car from North Carolina to Colorado, causing me to look longingly at some pics of it.  What you see is an example of what can happen when your engineering students have too much access to your car.  It can grow teeth.

Page 42-F: Installing the ACK Emergency Locator Transmitter

Installation of the ELT seemed straight forward, not even requiring a blog post.  The only semi-difficult task involved stripping and soldering four small wires onto an electrical connector.  The hook up was done by following the instructions in the KAI and looking at the diagrams in the booklet which came with the ELT from AKC.  All the wires and the unit itself along with the enunciator box and a mysterious RJ-11 connector, were then neatly zip tied onto the ELT tray previously installed.  Easy peasy, I thought. One of the previously installed wires, an RJ-11 phone wire, goes from the display/switch unit on the instrument panel back to the ELT behind the passenger seat.  When everything was hooked up, the enunciator box starting emitting a ticking sound and a red light on the display unit on the instrument panel started to flash.  A call to ACK revealed that the RJ-11 wires and connectors are either straight through (polarity preserved) or crossed (polarity reversed).  According to ACK, they should all be straight through, but on all Van's aircraft the long wire from the instrument panel display unit back to the ELT is always crossed.  Something needs to un-cross the wire.  It turns out that the previously mentioned mysterious RJ-11 connector was supposed to be crossed, thereby fixing the problem.  Mine was not.  Amazon's aviation department to the rescue.  Problem solved.  I waited until the big hand on the clock was straight up, activated the ELT, tuned my hand-held radio to 121.5, and was rewarded with the irritating peyow, peyow, peyow sound that an ELT makes.

Build delayed by more broken bones: A while back in North Carolina I fell on my bicycle, breaking my left femur and having a titanium rod installed from the ball joint to just above my knee.  This joined titanium already in that leg from the knee to the ankle.  The Spousal Unit and I always go roller skating each Monday night at a local rink.  Confirming the expectations of my friends, I'm now recovering from surgery to install a titanium plate in my left wrist, fixing one of the most common roller skating injuries (broken wrist).  It's hard to work on the airplane one-handed.

Off topic: more Colorado wildlife

When I moved to Colorado from North Carolina, I often said that I wanted to see a Mountain lion in the wild.  Since arriving I'd seen bears, bobcats, moose, thousands of elk but no mountain lion.

 A couple of months ago the Spousal Unit awakened me at the butt crack of dawn, telling me to come see a mountain lion eating an elk behind the house.  Pretty exciting but a couple hundred yards away.

Then a trail cam on my back patio got a picture of one much closer to the house.

Then this.  Probably the same guy trying to cover a deer less than 100 yards from my front door.

No more pages in the build manual!

 As I approached the end of the build manual I was expecting the last part to contain instructions for loading the software into the Skyview HDX, adding the fluids, and doing the first engine start.  None of this was there.  There were no directions for finding additional documents that would walk me through this stuff.  Turns the documentation is there and I had to find out about it by reading other blogs and digging around on the RV-12 forums on vansairforce.net.  The first thing I should have gone to is called the Production Acceptance Procedure (always referred to as the PAP) which only exists because the RV-12 can also be had as a factory-built S-LSA airplane.  Other experimentals, E-LSA or EAB, don't have this document.  Early in the PAP another document is referenced, a read-me file on the downloads page at vansaircraft.com.  

This read-me file contains all of the steps required to download the Skyview software, settings files, databases, sensor definitions and current TFRs. It explains how to tell the software what equipment is installed and how to calibrate this equipment, including how to calibrate the stabilator position for takeoff, how to calibrate the fuel system, ADAHRS, AOA, autopilot servos and other stuff.  In other words, this is an absolutely vital document.  I went as far as I could in this, then came to some stuff that required the engine to be running.  Somewhere in here I discovered the PAP and everything started to become clear.

The reward for completing the steps in the read-me file was that I got to see the Skyview HDX all lit up in all its glory.  This was pretty exciting for me and I spent quite a bit of time staring at it.  On the right in the picture is my iPad running Foreflight propped up on the map box door.  I'm planning to mount it approximately in this position but standing off the instrument panel a bit and tilted toward me in the left seat.

At this point, with some fear and trepidation, I tried the landing light, navigation lights and strobe lights.  They all worked!  After patting myself on the back for doing such a great wiring job (prematurely, it soon became evident) I proceeded to test the Garmin GTR-200b radio.  This involved plugging a headset into the jacks on the pilot and co-pilot sides, which resulted in a loud squeal in both and an even louder string of swear words from me.  A wiring problem!

I'm convinced that 95% of all wiring problems involve a faulty ground, but where?  Since managing electrons is not something I'm good at, I enlisted the help of my EAA Technical Councilor, Dan Berry, to help track it down.  Like me, Dan is a mechanical engineer, but unlike me, Dan is a wizard with electrical things.  After studying some electrical diagrams that he pulled up on his phone from somewhere on the internet, he decided that the fault must lie somewhere in the wiring at the left wing root.  To get to it, I had to pull the wing.😡  This task is not as onerous as it might first seem since the RV-12 is designed for easy wing removal, very similar to that of a glider.

 I see a lot of talk on the forums about systems that allow one person to remove a wing unassisted.  Mine is simple: a 4x8 sheet of plywood with legs on casters.  The top of the table is just below the inboard end of the wing.  Moving blankets get stuffed between the table top and the bottom of the wing, accounting for dihedral.  When the spar pins are pulled, the table and wing can be easily pulled away from the airplane.

After removing the mountain of crap that had grown up atop my wing table, I pulled the left wing just enough to allow the wiring to be accessed. The tube seen going from the wing root into the side of the fuselage takes a pressure signal from the AOA port on the wing leading edge to the ADAHRS box mounted in the tail cone.

After Dan made some measurements to confirm his original diagnosis, I discovered that two of the seven wires going into the Molex plug shown had pins which were not properly inserted.  I still find this hard to believe since my standard procedure with Molex or d-sub pins is as follows: crimp the pin, tug the pin on the wire, insert the pin into the female plug, tug the wire to ensure proper insertion.

The blue connector shown automatically connects the wires from the fuselage to the nav and strobe lights and the stall warning vane when the wing is installed.  A corresponding one on the right side also has the wire for the landing light.  With the headset plugs hanging out in the air as shown and the blue plug not connected, the radio worked great.  Problem solved!  Turns out, one problem was solved and one was yet to be revealed.

Happily, I re-installed the wiring in the fuselage, re-installed the wing and plugged in the headset: loud squeal.  As Tom Cruise's sidekick said in the movie Risky Business, sometimes you just have to say WTF (abbreviated here due to the family nature of this blog).

Somehow, when the two halves of the blue plug came together, the squeal starts.  The nav and strobe lights work fine, which leaves the stall vane.  Turns out that by moving the stall vane around, I could make the squeal start and stop.  In its relaxed state, this normally-open switch was closed.  This new "squeal" I was hearing was the stall warning horn!  The switch/vane assembly can be reached (barely) by removing an inspection plate.  Sticking my phone in the wing, I got a picture of the assembly (shown).

The assembly consists of the microswitch and vane sandwiched between two plates.  When I built this thing I remember fearing that if I over-torqued the bolts I might crack the plastic housing of the switch.  The result was an assembly which was no where near rigid enough.  I could grab the outer plate and move it relative to the inner one.  Another self-inflicted wound.  Nothing to do but remove, re-torque and re-install.  Turned out to be one of the more challenging and frustrating things I've had to do on the build. 

The really maddening thing is that most people with AOA disconnect the stall vane after certification, which no doubt I'll do, making all this a waste of time.  But, being an E-LSA it must be built exactly like the ASTM prototype.  Right?

Off topic: more Colorado wildlife in my back yard recently.  Look at the rack on that one guy to the right.

Page 49: Cooling system

The Rotax 912 is an odd duck in that it has water-cooled heads and air-cooled (finned) cylinder barrels.  The water is actually a 50:50 mixture of antifreeze and distilled water.  From an engineering standpoint this is superior to the more typical air-cooled-only (Lycoming, Continental) arrangement.  Of course all the rejected heat ultimately goes to the air.  It just takes a different path with the Rotax.  

The components of the system which must be installed are the fiberglass duct which directs the ram air from just aft of the prop to the heat exchangers (shown again from the previous post), the oil cooler (air-oil heat exchanger), the "radiator" (a poor name since there's negligible radiation heat transfer) which is an air-water heat exchanger, a cabin-controlled door which can divert the hot air downstream of the radiator into the cockpit for heating (definitely needed here on the Front Range), and various hoses which transport the oil and water to various places.

The oil cooler is first bonded with high-temp RTV to an aluminum frame to which nut-plates have been riveted, allowing it to be attached to the bottom cowl.  The aft (left) end of the duct interfaces via a rubber seal (shown on the pic) with the radiator.

For the bonding process, the instructions call for a 20 lb weight to be used to ensure proper contact while the RTV cures.  I searched around the hangar weighing various things to use for this.

It turns out that a jug from a R-985 Pratt & Whitney radial from a twin Beech weighs almost exactly 20 lb.  I put the corresponding piston in the picture to show the beating it took when the engine swallowed a valve.  The jug (with cracked head) is sitting on a wooden plate atop the heat exchanger

The radiator (which doubles as a heater core) is also bonded to an aluminum frame which provides a flat surface against which the aft edge of the cooling duct interfaces.  The instructions specify that a 1/8th-inch gap should exit all the way around between the duct face and the aluminum frame.

A separate fiberglass piece bonded with epoxy (and RTV as a backup) to the duct itself makes this do-able.  The gap, which can be seen in the pic at right, was achieved by temporarily gluing inch-long segments of paint stir sticks from Lowe's (not Home Depot, too thick) around the aluminum and clamping everything together while it cured.  The rubber gap seal is bonded to the duct face later.  The seal can be seen in the first pic.

Hooking up the oil lines turned into an unexpected problem.  One line goes from the sump on the bottom of the engine to the oil tank (shown) at the top.  The ends of this particular hose are "clocked" by the supplier and the angle can't be changed.  The instructions warn not the twist the hose.  Looking at the pic at left, you can see that the female end can't possibly fit on the nipple on the tank without  significant twist.  I ordered a replacement ($288!) which fit perfectly.  The Mothership did give me a refund when I sent the bad one back.

Installing the oil lines, water hoses, gas lines and a couple of vent hoses in the tight quarters of the engine compartment was, in a couple of cases, a challenge.  Van's commonly requires the use of double Adel clamps, where one clamp attaches to a structural member, the other to a hose and the two are attached to each  other with a bolt, creating a sort of standoff.  I hate single Adel clamps, but two together requires the invention of new, stronger swear words.  In one case I didn't have a 3/8th-inch socket small enough to fit into the available space, requiring me to fabricate the wrench shown at right.  I've had to use it several times now.

In July I made my 33rd trip to Mecca (Oshkosh).  There I encountered this RV-12 with the best quality paint job I've seen on a -12.  If only I had a spare $20k!  As I've said before, I'm going to fly for a while with no paint, then wrap it in vinyl.  With wrap I can do it a bit at a time and if I screw something up I can easily remove the wrap and redo it.