Joshua's RV-9A Project

To close out the flight testing, I juggled ballast around the cabin to explore the range of CG loadings.  With all the typical loading scenarios that I worked out, I can’t put the plane outside the envelope unless it’s over-gross; it never really gets close to the edges.  So, I worked weight back into the baggage area for aft CG testing, and repeated the stall series for good measure.  No surprises.  She really flies nicely.

With the temperatures turning colder as winter comes on, I put a strip of aluminum tape on the top of the oil cooler, to try and raise the oil temps up.  Since the variability of fall is unpredictable, I want to approach blocking it off in increments, so it doesn’t get too hot.

With just over 40 hours on the clock, I brought the logbooks up to date with the various engine maintenance, oil changes, replumbing, and so forth that had been done during the test period.  Then, wrote out and signed off the Phase I completion entry.  Free at last!

I’ve noticed a quirk in the AFS 4500 display, and after some experimentation, have identified the specific conditions that produce it.  I remembered to grab some screenshots on a recent flight, hoping they will be useful to Rob and the rest of the AFS crew for figuring out what’s behind it…

The bug is related to the VP-X system display page (accessed by pushing ‘Check’ once): whenever that page is displayed, alongside any page that contains BOTH the course AND bearing needles on the display, neither the course needle, bearing needle, or the colored status indicators for the VP-X loads are displayed.  The pitch indicator wings and flightpath marker also disappear.  In addition, the bar along the bottom of the screen with the button/knob legends turns white.

If only the course OR bearing needles are displayed, everything displays normally.  It is only when both needles are selected, that the problem exhibits.

(click any image for a full-size version)

PFD screen with CRS and BRG needles:

Same screen, with VPX page selected:

Split PFD/Map screen, with CRS and BRG needles selected, and VPX page displayed:

Split PFD/Map screen, with only CRS needle selected, and VPX page displayed, all is well:

Split PFD/Map screen, with only BRG needle selected, and VPX page displayed, all is well:

Map page, all is well:

6-pack page (4 with VP-X displayed), all is well:

As I’ve tried to fill up all decent-weather daylight hours with flight testing, the days have continued to get shorter, and the other activities that go along with the arrival of fall have begun again, as well.  Which is a long way of saying, I’ve gotten rather lazy about posting my flight test notes after each flight.  So this entry covers the last 2 weeks worth.

Things are generally going well, and I’ve continued getting to know the plane, and become more and more comfortable with how she flies.  I’ve done a moderate amount of pattern work (though I could use more yet) at the various airports, and can consistently land in a reasonable distance.  I’ve done simulated engine-out drills over the airport (altitude loss was 6-800′ per 360° turn).  Steep turns, dutch rolls, more stalls in various configurations, and so on.

After previous adjustments to the heavy left wing, I’ve flown the last 3 flights with 120 lbs of ballast in the right seat, and I’m happy to report that in the current config, with the ballast, it flies pretty much hands-off straight with an equal fuel load.  So, with a passenger, it’s balanced.  I’ll install the roll trim linkage soon, and unload the ballast.

I’ve done climb rate testing, and though the data isn’t as precise as I would ideally like, I’ve called Vy (best rate) to be 85 KIAS, and Vx (best angle) to be 75 KIAS.  In reality, the pitch angle below 80 is so steep that I wouldn’t want to go there…it’s impossible to see over the nose.  I usually end up climbing out around 100 KIAS, keeping the nose just below the horizon for visibility.  (I expect the speeds to change when we get the prop re-done.)  ROC at ~3000′, Vy is around 1450 FPM.

Messing around with economy power has been fun, too; how much fuel does it take to go along at 90kt, for example.  The EFIS uses groundspeed to calculate fuel economy (mpg), so any head/tail wind is factored in; I had a 23kt tailwind today at one point, and was showing 48 statute mpg at 143kt GS (120 ktas, 3.5 gph)…

Coming back to the airport at twilight continues to be a highlight — watching the sunset, and the lights winking on in small towns and farms, the headlights of cars on the county roads below.  Then, coming back into the pattern and clicking the mic to bring up the lights, I’ll never get tired of that view.

The engine stumble has essentially cleared up with the lower OAT.  Now, I’m trying to raise the oil temps, as I’m getting only 160 or so degrees.  I taped off part of the oil cooler which helped (mid-140′s to 160), but I need to add another strip and see what happens…looking to get over 180.

The nose seal weep that disappeared after 5 hours has reappeared, and weeping slightly more than before.  Not a lot of oil by any means, and not noticeable at all on the dipstick, just enough to make a bit of a mess.  Plan is to do the seal when I pull the prop for repitching; I already bought a couple new seals, and have the adhesive.

For some reason I’ve put off doing the maintenance logbook entries as I go along; fear of doing them wrong, I guess.  I was going to do them all tonight, but forgot the logbooks at the hangar.  Instead, I typed ‘em up on the computer, so at least I have all the numbers and such when I go to write ‘em in.  Now at least I don’t need to worry about forgetting something.  I may keep the electronic log going in parallel, too, since it’ll be searchable and readable (let’s just say my handwriting leaves something to be desired)…

I’ve worked on assembling a list of items that I want to put together for an onboard tool/spare kit, to allow repairs to be made away from home on trips.  Now I just need to track down all the stuff for an affordable price.

Allison is on break this coming weekend, and wants to go for a ride; she’d like to do some hops around the state to see her various family and check out the plane’s comfort level (it’s an easy 1:15 plane ride to her parents, or ~4 hrs in traffic on I-94).  I have just a few hours left on Phase 1, so if the weather cooperates this week and weekend, and I can get the time to fly off the hours, it should be doable.  I’ll be due for an oil change, too…but that can at least be done in the hangar after dark, whereas the test flight hours need to happen before ~7pm these days…tricky, as it’s just over an hour’s drive from the office to the hangar.

(summary of hours flown since last entry; 7 flights, 15.4 hours)

A month and a half on, flight testing continues.  As of today, the Hobbs reads 23.00; subtracting the various ground-run time done in pursuit of certification and engine troubles, I have 20.8 flight hours on the plane so far…half done with Phase I operations.

4 days of APRS squiggles, various speeds and altitudes; it’s clear I’m using all of the small test triangle.

Engine break in appears to have gone well, using oil consumption as an indicator; she used or blew out 1/2 quart in the first few hours, then slowly dropped to 7 quarts, where it stayed until I changed the oil this weekend.  On the advice of folks who said that filling it to capacity (8qts) will just dump a quart out the breather, I refilled to 6 qts indicated after the oil change.  7.4 hours of flight time since the oil change, and the level hasn’t budged…still at 6 qts.  Excellent.

Other than the engine stumble/miss, the problems seem to have been sorted out…

• The cabin CO level seems to have been resolved by the reseating of the #4 exhaust stack, where there was evidence of a small exhaust leak.
• I did the first oil change at 10 engine hours this weekend, without making too much of a mess.  I also took the opportunity while the sump was empty to remove the quick-drain valve, then clean and reinstall it with better thread sealant — hopefully this will stop a very small weeping leak at the threads.
• The heavy left wing was out of balance by ~9gal of fuel.  I took another critical look at rigging, and found the left flap was being pulled up tighter than the right; I lowered the left by 1 turn on the rod end bearing, and that brought the imbalance to ~5gal.  Before that, I’d experimented with a small trim tab on the right aileron to see what effect it had…nil.  Today, I taped a larger trim tab (6″ x 3/16″) to the right aileron, and she flew nearly hands-off.  I’ll get some ballast weight to load in the passenger seat, to take the solo-weight imbalance out of play, and see where we are then — if the trim tab is even needed with an even weight distribution.  Once we’re close enough that the roll trim can handle it (Van’s suggests <=3gal imbalance), I’ll pull the seat pans and hook up the roll trim mechanism.

I spent Monday — which I deemed too gusty to fly (at one point something like 19G28 @ 60° from runway heading) — reinstalling the fuel flow transducer.  As part of the engine troubleshooting, the transducer was removed from the FWF area.  Due to mounting considerations, I decided to reinstall it in the center tunnel, under the “doghouse” with the fuel pump.  The law of unintended consequences soon arrived, and I ended up remaking every piece of fuel tubing between the selector valve and the firewall, in order to make everything fit and work.  In the end, though, I believe the install will be more maintainable, since the new configuration makes it easier to get the pump/filter assembly out of the plane.  (I did open and clean the filter while I had it all apart; there was a minor amount of schmutz in there that I attribute to the several thousand paper towels that were used to clean the fuel tanks during the Proseal process…)  Also required with the pluming changes was reflushing the fuel system and a new set of flow tests…I’d estimated the job at 4 hours, but it ended up being 10+ when all said & done.

The nagging problem is the engine stumble/miss.  In addition to removing the 40″ of hose + FF transducer, and replacing it with 29 inches of hose, I also added a heat shield sleeve to the entire fuel servo->spider fuel line.  I’ve not really noticed any difference in operation…it still stumbles/misses (engine folks have said that they use the word stumble for a different symptom) on low RPM operations (final approach & taxi-in, notably) when the engine is warm.  Now that I have a larger body of data behind me from test flights, I’ll call Airflow Performance again to see if they have any additional suggestions–if they think it’s still a boiling fuel issue–and talk to Aerosport Power after that.  I can’t see anything else to do with the fuel system WRT heat loading, other than buy & install the fuel pump cooling shroud that Van’s offers–it couldn’t do any harm, and the pump is definitely hot, but I’ve heard it is a major PITA to install.  Otherwise, we have a forecast cold weekend coming up, which could provide some insight.  (Though, in my opinion, OAT’s in the 60′s and 70′s shouldn’t be causing a problem…)

Flight testing is moving on…in addition to burning up time doing some sightseeing around the test area (leaves are changing fast, and fields being harvested), plenty of actual testing has been done, too:

• Climb speed tests from 3000′ to 8500′.
• Glide speed tests on the way back down.
• Climb to and short cruise at 12,500′.
• Exploration of power-off stall characteristics: straight ahead, and in increasing banks left & right to 30°.  With flaps up, half, and full.  She’s quite well behaved in all configurations; some exhibit a slight left-wing down tendency, but nothing excessive, extreme, or not easily remedied.  After flying the stall series, I can make it consistently break straight.  The prop-stopped stall from my first flight has never repeated itself, even through the 30+ stall series I did over the weekend.
• Partial power-on stalls.
• Exploration of slow flight and MCA regimes with flaps up and down.
• Tweaks to radio mic gain to improve transmission audio quality.

Since the engine break in is pretty well done, time to start experimentation with LOP operations; initial testing leaning from 75% power, 6.8gph (~50LOP) gives about 145ktas, and 28smpg (better than all of our cars except Allison’s little coupe).  It gets pretty rough beyond that, but I still have the Pmags set in “stock” config, with the low advance curve…rumor says that selecting the higher curve improves LOP operations; we shall see.  CHT’s and oil temps have been great all along; CHT’s on the front cyls are a bit higher than the rears, as expected, but no one is too warm, even on extended climbs.

For fun, today’s test was economy…partial power LOP, at C-150 speeds.  ~90ktas, 2.5gph = 42smpg with over 9 hours endurance.  Even better economy might be out there, with different settings — I just set this up to see what it would do at C-150 speed.  I will also be curious to see what transpires when I get the intersection fairings on, and then have the prop repitched (possibly over the winter, or in the spring months when light & work schedule will conspire to prevent much flying time) to better match the engine & airframe.

I’ve done landings at all of the Phase I area airports now…Red Wing, Boyceville (short & narrow), Menomonie, and Winona.  Winona is a rough airport–the surfaces are deteriorated, and has the highest fuel price (Menomonie is lowest at the moment, followed by Boyceville); I’ve fueled everywhere except Winona.  At Menomonie yesterday, I stopped at the pump, and a fellow building an -8 came over to chat, along with the FBO owner or manager; nice folks, nice airport.  I did 3 landings there tonight before returning to base as the sun set.  I’ve selfishly been timing my return & landing so that I get to see the sunset, and the lights in the towns below coming on, along with the airport beacon & runway lights…it’s a nice sight, though none of my sunset photos so far have done it any justice.  I did get this nifty picture of some farm fields north of Winona in the low sunlight tonight, though…

I have photographed nearly every decent town in the Phase 1 area, along with what seemes like most of the lakes.  More practically, I’ve learned my way around the buttons and menus of the electronic doodads, and don’t have to think much about what to push anymore.  I’ve begun to develop habit patterns for entering flight plans, managing radio frequencies, and so on, along with more mundane stuff like fueling without spilling fuel all over the wing, remembering to sump the tanks, etc.  I’ve developed my mobile office, for days when I still need to deal with emails, server problems, etc, regardless of where I’m at (which is pretty much 7 days a week).  And taken goofy in-flight and on-ground pictures.

19.3 hours left on the Phase 1 clock…

[ summary of shop & flight test hours for the last week was entered on this post ]