Balancing, Act 2

One of the last significant tasks before inspection is weighing the airplane to determine its Basic Empty Weight (BEW) and Center of Gravity (CG). An accurate BEW and CG are critical to keeping the airplane within its weight and CG limits. Fortunately, EAA Chapter 106 has a great set of ramps and digital scales that are available to members for airplane weighing…very cool!

I prepped the airplane by emptying the fuel tanks and topping oil up to 8 quarts, then set up the ramps and scales.

Setting up the scales

The airplane must be in level flight attitude, so Ellen and I rolled the airplane onto the ramps and leveled it by adjusting tire pressure in the main wheels and adding shims under the tailwheel scale.

A tailwheel on a scale

The weighing process was simple. Roll the airplane on the scales, roll it off, record weight and repeat to confirm the numbers. Easy-peasy!

While the airplane was level we also measured main wheel and tailwheel distances from the wing leading edge, which is 70 inches behind the W&B datum defined by Van’s. With that number and our measurement, we were able to compute the arms for each wheel and so compute the empty center of gravity.

Large scale picture

The results –

  • Right wheel – 535 lbs
  • Left wheel – 530 lbs
  • Tailwheel – 62 lbs
  • Basic empty weight – 1127 lbs
  • Center of gravity – 79.4 inches aft of datum.

All in all, I’m pretty happy with the result. I had hoped for basic empty weight to be closer to 1100 lbs, but we made conscious decisions to add things like a constant-speed propeller, nicer seats and carpet that add weight but improve the airplane for travel.

Next step…DAR inspection!

Calling for a taxi

I’m following the EAA Flight Test Manual and Test Cards and the last test required before first flight is taxi and brake burn-in. Landing gear and tailwheel setup on the RV-7 are straightforward so I didn’t anticipate any steering problems on the ground, but like any aircraft test it’s the things you don’t expect that can really bite you. And since brake burn-in requires 25-30 knots groundspeed, I planned to verify steering in a large, open ramp area before heading out to the runway for higher-speed stuff.

Taxiing under power~Fortunately, the RV-7 is very well-mannered on the ground and I had no problems with brakes or steering as I taxied to the ramp. A quick check on Comm 1 and 2 was also successful, and engine EGTs/CHTs were stable and within expected ranges.

Here’s a nice video courtesy of Ellen…

The only problem I encountered was minor landing gear shimmy – if you look closely in the video below, you’ll see the main gear tires oscillating just a bit. This is common to RVs and most builders correct it by adjusting tire pressure, adding wood stiffeners to the gear legs, or both.

Big props to Ellen…she was my ground crew and called on the radio to ask if I felt vibration, which I did, but wasn’t sure what it was.

After finishing taxi tests and brake burn-in, I finished the G3x full-power vibration survey and magnetometer calibration. It’s good to have the avionics completely done!

The taxi hero shotThanks to Burt Wadas for being my official ground-test photographer!

Balancing Act

The last major task on my to-do list was balancing the elevators. Van’s instructions aren’t super clear on whether to do this before paint, but a call to Sterling at Van’s confirmed that the elevators must be balanced before first flight. Works for me.

I decided to put together a simple rig for balancing – two pieces of aluminum box extrusion trimmed and drilled at one end to accommodate elevator hinge bearings and bolts to hold them in place, both clamped to an aluminum work support. Here’s a pic –

Elevator balancing rig

The left elevator needed some weight and I had to remove some from the right elevator.

With balancing complete the elevators went back on the airplane and the airframe exterior is DONE!

Lighting tips

Another finish-up task is done – installing LED nav/strobe lights on the wingtips. It was an easy job, simply installing the light mounts and connecting the lights themselves to wiring runs from the wing conduits.

Wingtip Nav-StrobeAll lights in action…the Mighty RV is ready for the night show at Airventure.

Rolling my own…

…Nav antenna, that is. I had always planned on using a Bob Archer-designed wingtip Nav antenna because they work well for horizontally-polarized ILS/LOC/GS signals and also fit nicely within the wingtip fairings, thus eliminating a tiny bit of parasitic drag. You can find Bob Archer’s description of his antennas here and instruction/plans for building them here on Van’s Air Force.

I was all set to buy one of Bob’s antennas from Aircraft Spruce. But since I’m an Electrical Engineer by education (can’t spell “geek” without EE) as well as an airplane homebuilder and ham radio operator (N1DLS), I decided to make my own antenna out of some materials I had laying around the shop and a piece of fiber/resin circuit board material I bought from McMaster Carr.

There’s nothing difficult about fabricating the antenna, it’s only an afternoon’s work to put one together using plans you’ll find on the interwebs.

Home-rolled Archer antenna

The magic in this antenna lies in a couple of areas – the gamma-match coax impedance-matching device, which is the narrow aluminum and fiberglass structure to which the coax connects, and the length of the long outboard aluminum strip that’s parallel to the wing. The antenna must also be well-grounded to the aircraft, hence the big piece of aluminum angle that holds it onto the wing.

Archer Gamna

So how does the novice Archer antenna builder know how to adjust these magic bits? The answer is an antenna analyzer, something which no self-respecting ham radio nerd would be without. Here’s mine –

Antenna analyzer #1

The instructions should tell you how to tune the antenna but if you need help and an antenna analyzer as well, hit up your nearest airplane-building ham radio buddy (there are a lot of us) and he/she/I will be glad to help.

After several iterations of adjusting the gamma match and antenna length, I had a well-tuned and matched antenna…I hope. The analyzer picture below shows that the antenna is almost perfectly matched at 114 MHz. I can live with that.

Analyzer with matched antenna

And here’s the final product –

Final Archer antenna

Applying pressure

I started back to work this week for The Man…a different Man, and this one pays better!

It’s been awhile since the engine has been turned over and since the first start is approaching, it’s time to pre-oil the engine. Superior’s manual says that you can do that by either applying oil at 35 PSI into one of the lubrication galley ports on the front of the engine, or by cranking it with the starter until the oil pressure sensor shows 20 PSI. I chose to do the latter as it’s less mess and is also a good test of the G3x. I loosened slightly the oil pressure line AN fitting at the sensor end so air could escape. Made a little mess when the pressure came up, but was easily cleaned.

A video is worth a thousand words and there’s not much else to say anyway.

Big thanks for Mike Henning and Bob DiMeo for their help!

Wiring and plumbing the wings

We’re getting close to Oshkosh and I wanted to get as much done as I could before our trip, so over the weekend I installed the pitot tube and wired landing lights, OAT probe and pitot heat to their circuits in the fuselage.

Here are the Baja Designs Squadron Pro landing lights connected and doing their thing. Not terribly bright in this picture but they hurt to look at, and that’s a good thing…

Landing lights

No post on landing light installation would be complete without proof that the GAD-27 can indeed flash the lights…

I had fitted and plumbed the pitot tube several years ago so installation was relatively straightforward – just had to connect the AN plumbing and heater connector, then screw it to the pitot mast. And yes indeed, it gets hot…

Heatet pitot is hot!I screwed up the fuel tank feed lines, so some surgery was required to install an AN union and line to the left fuel tank. Once that was done, I reinstalled the vent line I fabricated a few years back. The RG-316 coax you see snaking out from the rubber gasket is a line that connects a Princeton capacitive fuel level sender to the fuel tank’s BNC connector.

Left fuel tank plumbed

Same thing on the right wing…

Right fuel tank plumbedPlumbed the right wing as well, and installed the fuel tank support bolts on both sides.

Pitot-static and OAT connected

Connected the OAT probe and pitot-static lines in the cockpit.

More right wing plumbing…and finished connecting the right fuel tank. Had to do another splice job on the fuel line, but it came out fine.

And now we’re off to Oshkosh!

Miscellaneous engine tasks

Lots of little wrap-up tasks remain…this weekend I installed engine sensors.

Here are the PMag connection, oil temperature, current shunt, manifold/fuel/oil pressure and fuel flow sensors all wired…

Engine sensors wired

CHT and EGT probes wired on cylinders 2 and 4…

Cylinders 1 and 3 sensors

…and the same on cylinders 1 and 3.

Cylnder 2 and 4 sensors

I’ve been putting off safety-wiring the prop bolts ’cause it’s a reall pain in the ass.

Prop safety-wired and spinner installed…but now it’s done, and as a treat to myself I installed the spinner!

On the wing

Now that I’m done with transition training, I’m all fired up to finish the Mighty RV. So..let’s get those wings on!

Starting the wing installThe promise of beer and burgers made it easy to co-opt some of my flying and/or RV-buidling friends to come over to the ThermosWorks on Saturday. The wings aren’t particularly heavy, but a few extra pairs of hands come in handy when trying to maneuver the wing spar into it’s slot in the fuselage.

Another wing install

Mark Masse (RV-7 builder) and Rich Snyder (RV-8 builder) work the left wingtip up, down, left and right while Mike Henning (RV-4 builder/flyer) guide the spar into the fuselage and Burt Wadas (best friend) positions tapered stainless steel pins to align bolt holes.

The last left wing install pic

Almost done…there are two close-tolerance bolts inserted now, enough to hold the wing in place til the rest of the bolts are installed.

Right wing install

Onto the right wing…same process, but much faster the time.

Another right wing install

You can’t see him in this picture, but Bob DiMeo (RV-8 builder/flyer and my Technical Counselor) is waiting to insert tapered pins in while Burt and I position the wing spar.

Sucking it in...

Fast forward an hour or so…the wings are in place and all bolts inserted. Everyone who has a gut is sucking it in for this picture!

B-e-a-youtefull!

After burgers and beer, Ellen and I pushed the Mighty RV out into the sun for some pictures. Beautiful, ain’t it?

Even more beautiful

Another picture, I knew you’d ask for it.

Finally beayouteefulAnd finally, a really nice shot captured by Ellen. This is a big day in the life of the project – we’re a huge step closer to flying!

Transition training time

I’m not good at forecasting completion dates for the Mighty RV, but I took a chance on being done this Summer/early Fall and booked transition training with Mike Seager this week in Vernonia, Oregon in the factory RV-7 trainer, N477RV.

N477RV

Vernonia Municipal (05S) is beautiful and quiet grass strip with only a few hangars.

Vernon OR airport

I put off my airline and lodging reservations as long as I could – probably a little too long. It’s not particularly easy to find a place to stay in Vernonia, but my wife came across a really great place on Airbnb that’s only a mile or two from the airport…

A great place to stay

Tamara and her family are great hosts, and their guest suite is spacious, quiet and comfortable. I highly recommend you check it out if you’re traveling to Vernonia for training with Mike!

The first flight on 26 June was a short intro flight from Vernonia to Scappoose (KSPB)…

27 June first flightTurns out that my first landing in Scappoose was one of only a few really good landings I made that week!

26 June second flight

The second flight on 26 June consisted of air work – steep turns, slow flight, power off/on stalls – and several touch-and-gos at Scappoose. N477RV had only recently been updated with an Advanced Flight Systems glass cockpit including ADS-B Out and In.

The RV-7 is easy to fly, but there’s definitely a learning curve when transitioning from a slower, less-responsive airplane. Control forces are significantly lighter, and gentle nudges on the stick quickly replace larger movements used on garden-variety Pipers and Cessnas. The RV is less speed-stable than I expected – a known characteristic – so Mike teaches trimming for pitch attitude rather than speed and that seems to work well. Stall characteristics are fairly benign, with a slightly sharper break but fast recovery with pitch reduction and/or power addition. Rapid application of power at low airspeeds can produce pronounced torque roll which was an eye-opener at first, but I quickly became used to it. Power-off descent rates are relatively high, in the vicinity of 800 feet per minute in this airplane equipped with a constant-speed prop.

I’m a relatively low-time taildragger pilot, but I found the RV-7 easier to land than the Citabria I’ve been flying. The RV’s large rudder requires less movement to keep the airplane pointed in the right direction, and its wide-stance landing gear and low wing make crosswind landings less challenging than the Citabria.

27 June first flight

After ten stop-and-gos at SPB, I was pretty much cooked for the morning of the 27th. Fortunately, Mike had me scheduled for flights right after breakfast and lunch each day, so I had a lot of time in the afternoon to relax.

27 June second flight

Weather on the afternoon of 27 June was challenging…there were showers and thunderstorms moving through the area so we took some detours to stay legal as we worked our way back to Vernonia.

Marginal VFR

Blah

28 June first flight

Lots more touch-and gos on the morning of 28 June. At this point I thought I was improving nicely, but the afternoon was to prove me wrong…

28 June second flight (1)

28 June second flight (2)

We headed over to Astoria (KAST) for some crosswind landings on the last flight of my transition training. I can’t say that these were the best landings I ever made, but Mike patiently worked me through my mistakes.

The RV grinMy RV grin is in full force. Mike is a wonderful instructor – patient and easy to work with while training to high standards. I’m certain that I’m not the best student that Mike has ever had, but I’m pretty sure I’m not the worst and I definitely felt very comfortable flying the RV-7. I couldn’t wait to get back and finish up the Mighty RV!