Calibrated Left Fuel Tank

I calibrated the left fuel tank tonight.  I ended up adding 20.44 gallons of fuel which is only 0.01 gallons more than the right tank.  That’s way less than the margin of error for the fuel measurement I was using, so I’m considering the two tanks identical in capacity and in unusable fuel level.  I filled both tanks all the way to the top so that I can begin calibrating the fuel flow sensor on upcoming flights.

Glassed Other Side of Gear Legs

No pictures tonight since it would look identical to last night, but I glassed the other side of the gear leg fairings.  I also stripped off the peel ply from last night and trimmed the excess epoxy.  I’ll need to sand down a few high spots before applying the filler.

Glassed One Side of Gear Legs

I wanted to lay up a thin layer of glass over the rivets holding the hinge material to the gear leg fairings.  I used a couple of strips of the lightest cloth I had on hand and covered them in some Dacron (which is what you see here).  I’ll do the other side of these soon and then I can put a thin coat of filler on the fairings.

Firewall Forward Inspection and Flight Testing

I got down to the airport really early this morning because I wanted to take care of a couple of things and get some flight time before heading back to Hollister to help Greg.  I pulled the cowl and gave everything a thorough inspection.  One of the things I found was that the oil filler tube could be rotated a little bit by hand.  Since the safety wire hadn’t moved, I think the fiber washer just compressed a bit.  I used a wrench to snug the tube back down and then redid the safety wire to keep it tight.

I also adjusted the high RPM stop on the governor 1 full turn to increase the maximum RPM a bit.  I’ve only been seeing a little over 2600 RPM at the stop.  Although I’ll likely have to adjust it further, I redid the safety wire to ensure this can’t move.

I buttoned everything back up and took off again.  I figured I could get at least an hour of flight time before landing at Hollister again.  I decided to shoot an instrument approach to get some more experience with the autopilot and interaction between the GTN and the SkyView.  I loaded up the GPS 31 approach at CVH with the RUDNY transition and engaged the autopilot.  I duplicated the approach waypoints in the SkyView since they don’t yet automatically stay in sync with the GTN (though this is coming).  The GTN did turn anticipation and smoothly guided the autopilot onto the initial leg of the transition.  I programmed an altitude step-down and commanded a 500 fpm descent.  The autopilot turned smoothly to intercept the final approach course and held the descent rate rock solid.  I broke off the approach a couple of miles out and climbed back up to 6,000 ft.

I headed over to the acro practice area and did a couple of rolls to warm up.  I then tried a loop for the first time.  The plane really builds speed fast on the down line, but pulling some G’s takes care of that nicely.  Next, I tried a hammerhead on about an 80º upline to keep some positive G on the engine for oil pressure.  The rudder is quite a bit more powerful than anything I’ve flown before, so the rotation at the top was crisp and quick.

Finally, I decided to do a few spins to learn how the plane recovers.  The plan was to start with an incipient spin entry with an immediate recovery.  I climbed up to 8,000 ft and positioned myself near the South County airport in case I needed it.  I pulled the power smoothly back to idle and started slowing up.  Right at the stall break, I fed in full left rudder and the plane rolled about 90º to the left and the engine stopped cold.  The prop came to an immediate stop straight up.  I had already initiated the spin recovery and I immediately rolled level and got the nose down into a glide.

One of the questions Dave Morss asked me to determine if I was ready for flight testing was how I reacted in an emergency situation.  I’ve only had a couple of surprises in my years of flying, but I knew that I tend to remain calm and work the problem.  When the prop stopped, my only reaction was to utter the word “interesting”.  After establishing the glide, I hit the engine start button and got the propeller windmilling again, but the engine still wasn’t producing power.  I still had the mixture pulled way out, so I opened the throttle to give the engine some more air.  After a few seconds, the power came back smoothly.  I climbed back up and decided to try again, but this time over Hollister since they have much bigger runways in case I couldn’t get the engine started again.

After arriving over the airport, I again pulled the power to idle and started to slow up.  I slowed more gradually this time so that I could monitor the engine more closely.  As the plane slowed, the engine RPM slowly dropped.  When it got down to around 400 RPM, I knew something was wrong and I added power back.  The engine stumbled a bit as the power came back up, but it ran smoothly again at around 75% power.  I pulled back to around 40-50% power and the engine started running rough again.  I brought the power back in and started examining the engine monitor more closely.  My EGTs were down a bit, so I decided to try leaning the engine further and repeating the approach to stall.  This time, the RPM held steady at about 700 RPM all the way through the stall break.  I didn’t repeat the spin entry, but I feel comfortable now that the problem was simply an over rich mixture for the altitude.

I landed at Hollister to help Greg with his RV again.  It took much longer than we expected, but we were able to wrap up all of the spar bolts and get the nuts torqued.  The ailerons and flaps still need to be hooked up, but other than that, the plane looks pretty close to being ready for inspection.

I knew I was pretty close to empty on the left tank, but I wanted to run it dry on the flight back, so I left a little early to ensure I would have sufficient light.  I ended up flying for nearly 20 minutes before the tank ran dry.  I then switched to the right tank and landed at South County.

Flight Testing and Airplane Move

I got down to the airport mid-morning so that I could fix the lower empennage fairing.  I trimmed the extra glass I added and then worked on the rivnut that replaced the ClickBond nut plate that popped off.  I drilled the hole out to 0.182″ and then filed a notch for the keyed rivnut.  The keyed variety has a small protrusion under the head to prevent the rivnut from rotating if it ever loosens up.  Finally, I reinstalled the fairing.  I still have some filler to apply, but it’s looking much better.

After buttoning everything up, I took the plane out and flew for a little bit.  The right fuel tank calibration looks good and showed a full tank, so I switched to the left tank so I could run it dry in order to calibrate it.  I headed down to Hollister so that I could help Greg with the reassembly of his RV-8.  I got there a little bit before the plane and the crew showed up, so I stayed in the pattern for a bit and practiced wheel landings.  I bounced one, but the other three were very nice.

After helping to unload, we grabbed some lunch and got started on the reassembly.  After some final prep work, we got the wings slotted in and a couple of close tolerance bolts in on each side. We got both ailerons attached and hooked up the fuel and vent lines.

It started getting dark and I needed to be back on the ground at South County before night.  I headed out right around sunset and got back up to South County in just a few minutes.  It was still fairly bright out, so I stayed in the pattern for a bit and did some touch and go’s as the sky darkened so that I could get used to the sight picture and get a feel for how bright the landing and taxi lights are.  I stopped about 10 minutes before it got truly dark, but it was good practice and it looks like the lights are plenty bright.

Attempted Right Fuel Tank Calibration

Although I had previously calibrated the capacitive fuel senders by setting the empty and full points, I still needed to fill the tank in 2 gallon increments to create the voltage to fuel level mapping.  I started with an empty tank and created the first calibration point.  I thought it was a little odd that the sensor showed 5 volts, but didn’t give it too much thought.  I added the first 2 gallons, but the sensor still showed 5 volts.  I was pretty convinced something was wrong at this point, but I added a couple more gallons to confirm.  Sure enough, the sensor still showed 5 volts.  I started to worry that the sender was outputting a bogus value, but I decided to confirm all of the settings first.  Fortunately, I pretty quickly found out that I hadn’t configured the correct input pins on the EMS.  I needed to switch from the default (pins 20 and 21) to the ones I wired the senders to (pins 22 and 31) and change the input type to capacitive from resistive.  With that change, I was getting voltage values that made sense for both tanks (2.9 volts from the left tank which is probably around half full and under a volt for the right tank which had the four gallons I just added).  Unfortunately, I now need to empty the right tank again to redo the calibration.  I could try to drain the four gallons out, but it’s probably easier to just fly again and run that tank dry.

Calibrated Right Fuel Tank

After burning off the four gallons in the right tank, I calibrated it in the SkyView system.  I’m using a scale that has 1 gram accuracy, and I’m measuring roughly 1 gallon at a time.  Given the accuracy of the scale, I should be able to measure the fuel capacity within one-tenth of a gallon over the 21 gallon capacity of the tank.

I added two gallons at a time up through 20 gallons, hitting the add button at each point on the SkyView.  I used the opportunity to calibrate my dip-stick at the same time.  Finally, I filled the tank to the very top and measured the amount of additional fuel I added.  I ended up with 20.43 gallons of usable fuel.  The claimed fuel capacity is 21 gallons, so there’s only a little over 1/2 gallon of unusable fuel.  That’s more than I was expecting, but the flop tube pickups may leave a little more fuel in the tank than the standard pickups.  I still need to do some in-flight checks to determine unusable fuel in all normal flight attitudes including full slips.

Unfortunately, I almost completely drained my battery in the process.  I was down to 10.2 volts before I shut everything down and hooked the plane back up to the trickle charger.  I’m planning on flying again in a couple of days, so I hope the battery is charged enough.  I’m thinking I might need to replace the battery anyway since I killed it at least twice during the build (so dead that the trickle charger wouldn’t bring it back).

Riveted Hinge to Left Gear Leg Fairing and Flight Testing

I wrapped up the hinge on the other gear leg.  I’m probably going to end up shortening these since they’re a bit longer than necessary.  I need to fabricate the clamping pads at the top of the fairings, and then I can align them to the longitudinal axis of the plane.

The clouds lifted enough in the afternoon that I could take the plane up for another flight.  I took the opportunity to calibrate the AOA system.  On the SkyView, this is done by doing a series of stalls in various flight configurations and hitting a button on the EFIS each time.  I also took the plane up to 8,000 ft to measure the true airspeed.  I’m still slow because the wheel pants and gear leg fairings are not installed, but I saw 162 kts.  I expect to be near 175 kts after the fairings are installed.

I also intentionally ran my right tank dry in flight so that I can do the final fuel gauge calculation. The SkyView system annunciated “fuel pressure” just a second or two before the engine started stumbling.  I switched tanks and hit the boost pump, and the engine surged back to life within 3-4 seconds.  The experience was very different than when I’ve run a tank dry in my Bonanza.  In the Bonanza, the engine power winds smoothly down with no surging or stuttering.  After changing tanks, the power winds smoothly back up.  In the RV, the power loss was much more abrupt and there was quite a bit of stumbling before power was smoothly restored.

Riveted Hinge to Right Gear Leg Fairing

I wasn’t able to spend much time at the hangar today, but I did get down there for a bit in the afternoon.  The winds were way too strong to fly (at least until I get more practice in the plane), but I did get a chance to resume work on the gear leg fairings.  I had previously trimmed them to size and put strips of tape along the aft edge as reference points to ensure they’re straight.  I then clamped the trailing edge with some cleco clamps and drilled the hinges to the inside of the fairing.  After countersinking, I removed the hinge and deburred it.  I used some of the G/flex epoxy from West Systems to bond the hinge halves to the inside of the fairing and then riveted into place with some soft rivets.  I only had time to do the right fairing today, but hopefully I can knock out the other one tomorrow.

I had been planning on fabricating some jacking points for a while now.  Even though I’m going to lift the plane by the engine mount using the shop crane I bought, I need something under the wings to keep the plane from swinging.  Since I fabricated aircraft jacks awhile ago, using them to support the wings seemed like the best plan.  I bought some 1″ galvanized pipe caps and drilled them for a 3/8″ bolt.  I then inserted a 2″ long 3/8″-16 bolt through and tightened it down with a washer and nut.  This is screwed all the way down to the stop I installed in the wing tie-down point.  I might trim about 1/4″ off the bolt to reduce the bending load a little further.

The cap just fits over the end of the ram on the jack.  It has just enough room to move around that I can insert it over the ram without having to be perfectly aligned with it.