There was a time, once, when an airplane was considered finished when all of its parts came together and the thing flew. A couple of engine runs on the ground, some break-in time in the air to shake out any little assembly bugs that might have crept in, and it was ready for pilot and passengers. The Experimental/Amateur-Built aircraft regulations that came into effect during the 1950s (CAA, now FAA rules) dictated that aircraft built outside of Part 23 rules, designated Experimental aircraft, whether constructed in a factory or a basement, should have appointed test-flight hours to fly off before they are considered safe for flight with passengers or more than required crew.
The rules regarding the length of fly-off times are pretty clear, as there are only two possibilities. If the aircraft uses a certified engine and propeller combination unmodified-that means it is installed in the form it is certified in-then a 25-hour fly-off requirement may be considered for the machine. Everyone else gets 40 hours-even with an engine that is certified but might contain non-certified components or is part of an uncertified engine/propeller combination.
Who dictates this stuff, you might ask. Well, in our case with both our Kitfox IV and our RV-10, and in the case of most U.S. builders, the Designated Airworthiness Representative (DAR) who is inspecting the aircraft and issuing the airworthiness certificate gets to decide what kind of fly-off time to assign to each individual aircraft.
It makes sense. The DAR is there to verify that the work you did in building your aircraft is correct and that the plane is worthy of being set free to fly. Note that the DAR is not saying the airplane is airworthy-thats your job-but has concluded that it is fit to begin flight tests.
The DAR is supposed to have FAA training in how to determine which Experimental aircraft should spend a little more time in the test-flight phase than others. And most do. Most DARs, in fact, have seen a few different types of aircraft in their experience, some ready to fly, and some that probably should never have been pushed past the design phase. Our DAR, Ray Howell, issues airworthiness certificates to Liberty Aircraft for his day job. He reserves weekends and holidays to look over Experimental aircraft.
We chose Howell because he was the closest DAR who had actually issued an airworthiness certificate for our type, an RV-10. We were hoping that his familiarity with the aircraft would make the inspection go smoothly. That was a sound strategy. Howell was content that the work that my husband had performed on the aircraft was authentic and that the machine was well-crafted. He filled out our forms and handed them over, explaining as he did so that he felt compelled to issue us a 40-hour fly-off time because some of the components used in our engine are not FAA-certified, PMAd or otherwise approved parts. There was no discussion. He was holding to the letter of the rule and, for that matter, he was holding all the cards. Thats just how these things go.
I was a little surprised, considering that our first project, the Kitfox IV, had been assigned only a 25-hour fly-off, despite having a non-certified propeller and engine combination. I figured that the DAR would take into account our experience with building and consider the shorter fly-off for us. Id had high hopes to start out the summer with a nice trip north in the new machine, but the long fly-off time limited us to within 100 miles of our home base.
The Song Doesnt Remain the Same
A day or two later, seasoned by our first flight and first technical malfunction (see Down to Earth, June 2008), I was singing a different tune. I rationalized, whats 40 hours versus 25, after all? I mean, we wanted to fly the beast, isn’t that why we built it? And even if we were limited in where we could fly it for a time, at least we were flying it practically every day. We figured that we could do the whole test program in a little more than a month if we just stuck to a plan of flying a minimum of an hour every day. With two pilots, how hard could that be?
That philosophy worked well in the first 10 hours or so, when my husband and I traded off flights and exchanged notes on engine temperatures at different altitudes, at different power settings and in different flight configurations.
We played with the avionics for the next 5 hours, calibrating the EFIS, checking out the autopilot (amazing for someone whod never flown with digital accuracy) and practiced entering flight plans and loading approaches, selecting different map modes, and deciphering the terrain warnings and PFD graphics. The settings on the engine page alone could occupy you for a whole flight, if you werent careful.
It wasn’t long before we uncovered a few glitches in the electrical system, including a voltage regulator for the standby alternator that never did work, despite sending it back for bench-checking. We finally switched brands from B&C to Plane Power, and that did the trick. (Were still waiting for a refund from B&C, but thats another story altogether about what happens when you purchase and install parts that you might not actually use for two years.)
Not So Fast
All was on track until a little weather delayed the 40 hours in 40 days program. And then an opportunity to squeeze the airplane into the paint shop and finish its exterior put us more than a month off schedule. Somewhere around 20 hours and two and a half months into the fly-off, the whole concept began to get old. Wed broken in the engine, for the most part (oil consumption and cylinder head temperatures had stabilized), run the stall series and even tweaked the avionics and engine instrumentation. Flying alone and compulsively recording data was beginning to lose its novelty, and there was pressure from friends and family. People wanted a ride.
On my first flight with the airplane after it came back from the paint shop I was startled to sense it naturally rolling to the left. I checked the fuel balance, and even looked back to make sure that the dual trimtabs were not out of alignment. I couldn’t believe that paint alone could make such a difference. Back on the ground, the good news was that it wasn’t the paint, but the reassembly process that was to blame. A few adjustments to the flaps, then ailerons, then finally the wingtips, brought things back into balance (it took about six flights in all).
On the next couple of flights we began checking the leaning process, and I was flabbergasted to discover that the number six cylinder refused to stay within CHT limits on anything less than full rich fuel. It made no sense-everything had run so smoothly and evenly, with no cylinders out of temperature tolerances from nearly hour one. Even moving the mixture swiftly to more than 100 lean of peak, where the engine began to cough and sputter from the lack of fuel, did not cool this cylinder. Flying at 7500 feet, where the air was a brisk 55, didn’t do it. Were working to resolve our heat issues as this is written.
To make life more interesting, the EFIS software got a little cranky and decided not to boot quite right. Just like that. Gremlins. Poltergeists. Hiccups. Bugs.
The best I can figure is that this RV-10, with its IFR configuration and six-cylinder, fuel-injected powerplant, is a complicated beast. And after nearly four years of construction, it may actually take 40 hours of testing time to work out the inevitable kinks in its systems. Just take a look at the wiring under and behind the panel, and you’ll understand what I mean. It hurts just a bit to say it, but maybe, just maybe, the DAR was right.
Amy Laboda has taught students how to fly in California, Texas, New York and Florida. Shes towed gliders, flown ultralights, wrestled with aerobatics and even dabbled in skydiving. She holds an Airline Transport Pilot rating, multiengine and single-engine flight instructor ratings, as well as glider and rotorcraft (gyroplane) ratings. Shes helped with the build up of her Kitfox IV and RV-10.