Tuesday, July 3, 2012

Flight Test Follies: Things to do when it's hot

It's been hot in the Upper Midwest for the last few days, near 100 degrees. Keep that in mind if you're coming to Oshkosh in a couple of weeks.

As much as I love flying (and by the way, I've put more hours in my logbook in the last three weeks than in any year since the year I learned to fly in 1997), I've had very little interest in getting under a bubble canopy in these conditions.

So, it's given me a little bit of time to work on various "squawks" that the plane has provided, most of which involve a few systems. There's very little flight testing of the design that goes on as this is a proven design.

Still, I've done a few stalls and such (stalls clean at 51 knots, stalls with flaps extended at about 47-48 knots), but for the most part, I'm trying to check systems.

I'm still chasing the source of oil on the bottom of the cowling and had pretty much concluded it was coming from the top fitting on the oil cooler. I installed a steel fitting but it didn't "clock" the the best orientation for the hose coming from the engine (or going to the engine, I always forget which) and while it wasn't finger tip loose, it wasn't real tight either.

Not having another steel fitting, I swapped it out for an aluminum fitting.


And that solved the immediate problem, although I'm still seeing drips on the bottom of the oil sump bolts in a few spots.

I'll reinstall the steel fitting eventually. Mahlon Russell at Mattituck says the trick is to use Loctite 272, which is resistant to heat and expands to fill any gaps i the threads. You can't find the stuff anywhere but online, it seems.

I also noticed a couple of brown spots on the bottom of the cowling, mostly on the left side where the exhaust stack comes across to the #2 cylinder stack. I had already ordered -- and have been carrying around in the trunk of the car -- a role of reflective foil from Van's so I slapped another piece on and that seems to have solved that problem.

The #1 and #2 cylinders are still the hottest of the four cylinders, the GRT EIS 4000 engine monitor tells me. With the injection nozzles being cleaned (I've been checking them often just to be sure), this can only be due to those large "air dams" that Van's' instructions for the baffle have you install.




So I cut each one down by about 1/2". Stein Bruch gave me a piece of stainless steel to place between the cylinder fins and the air dam and then I simply cut them with a Dremel tool and cutoff wheel, and then filed and sanded them smooth.


I tested it out on a flight in the hot weather and while they remain the hottest two cylinders, the readings on all four cylinders are within about 10 degrees of each other.

Which brings us back to the nagging EGT reading (exhaust gas temperature) on the #1 cylinder. It had been low for months before initial flight, so I assumed it was a bad probe. When I cleaned the injector out, it zoomed to a reading 200 degrees hotter than the others, but then eventually settled back to being hundreds of degrees cooler.

When I watch the readings, it drops hundreds of degrees in a second, and then increases by 100 degrees. I traced the connection -- again -- and cleaned and tightened the spade connectors, and when I was taxiing out to fly, and when I took off, the readings were all similar. But when I taxied back in, I notice #1 was reading on 680 degrees. That's ridiculous. I'm really tired of chasing this problem and maybe I'll order a new probe, or perhaps I'll swap probes out and see how that works.

Maybe there's a problem with the bottom spark plug, but I haven't been able to check. The deep 7/8" socket I have to get at it, isn't deep enough to work. I bought another yesterday from Sears, but I'm not sure this one will work either. So does anyone have a deep socket for this task I can borrow?

Other squawks: There was a little chip on the lower right aft portion of the canopy from hitting the rear skin, so I sanded that out.

The heavy wing problem is becoming less of a problem. Although I ordered new brackets for the "heavy aileron," I haven't yet started filing bolt holes to lower the aileron. Instead, I've been squeezing the trailing edge of the "light" wing aileron. And it's improved. I calculated the other night, that it's about a 24 pound difference. That is, if I use 4 gallons of fuel in the "heavy" wing's tank, it flights pretty much level. At 3 gallons, Van's says don't worry about it. But I squeeze just a little more and I'll see -- maybe tonight or early tomorrow -- if that makes any difference.

I also have a larger "gap" from the top wing skin to the flap on the left side. I've been pushing the skin down and over time, I suppose that will make a difference.

I'm also recalibrating the Dynon D100 to see if that makes any difference in the -- as we say in New England -- wicked slow HSI information coming from the Garmin 296. At times, it can show a heading that's 180 degrees off. But the calibration system for the Dynon is pretty rinky-dink and it's possible to enter incorrect data, so I'll be doublechecking tonight whether that can be made better.

Everything else seems to be working well. In this heat, I can't get the oil temps to get much below 206-212, the cylinder head temps are about 390-406, and I can't get much more RPM tan 2350 pm the takeoff roll. But I got it to 2600 at 3,000 feet, I'm getting about 135 indicated on the airspeed indicator for both the backup steam gauge and the Dynon. The Garming GPS showed a groundspeed of about 149-157. Is this good, considering I don't have wheel pants or gear leg fairings or intersection fairings in place? I have no idea. But 130 knots is still 150 MPH and you get places with that.

I'm only up to about 13 hours through my 40 hours of Phase I testing, and I'm running out of places to go. On Sunday, I dropped into Dodge Center and was met by a gentleman who said, "is this the plane Doug has written about?" And, of course, it was (and is). It was Gordie Westfall, an affable man with great homebuilding skills who recently sold his RV-6 when he lost his medical. We visited his hangar and talked about projects he's got underway.

Then I flew over to Red Wing and met another builder who is building such a beautiful RV-9, I wanted to hang a sheet over my RV-7A to avoid any comparisons.

But, unfortunately, time spent chewing the fat on the ground doesn't count toward Phase I hours, so it was back in the air to fly around, look down, and hear the cash register ringing in my head while watching the fuel flow meter.

2 comments:

  1. Bob, I've only been following your blog for a few weeks, but it's pretty impressive. I'm not a builder, and don't want to be, but I greatly admire those who are. I'm sure the satisfaction you get flying it is beyond the comprehension of us non-builders.

    Two questions. I was surprised to read that your fuel burn was 16 gph, and that you seemed happy with that (did I read that correctly?). That seems like an awful lot of gas and I wonder if this is really what you expect. I don't know anything about your engine, so I'm not questioning it from that standpoint, but at $5/gal that's some pretty expensive flying.

    I also want to ask, and please don't take offense, but you identified the number of hours you've invested in the build at around 1,100 (if I remember correctly). My decision not to build was based partly on my concerns about my ability to survive all those quiet moments of self-doubt, wondering if I was doing it right, and whether I'd ever finish. From a practical standpoint, I also had doubts about the building to flying ratio. My question is; do you think the hours you spend flying it will ever equal the hours you spent building it?

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  2. The 16 gph figure was what was indicated on the engine monitor, however I also knew it was high because the FLOSCAN (the device that measures fuel flow) had not yet been calibrated. I've since calibrated it. A typical cruise in this plane would be about 8 gph. Still expensive, but consider that you go in a straight line. Also, when first breaking an engine, you pretty much run the engine full blast, so you're using 14 or so gph. It's a necessary evil.

    As for the number of hours, the total number was 3,023, if I recall correctly. There's no algebra for me involved. I loved the build process. Is flying better? I don't know; flying is cool but building is too. Every day you're working on something different.

    Over the course of 11 years you get stumped by stuff and you figure out what the fix is or how to do something and even though you don't think you ever will, you do. That's a good feeling and you probably pick up a friend along the way and that's good too.

    The process is a lot like life. If you look at the big picture of what you need to do, you'll freeze up instantly and be paralyzed by the enormity of it all. If you just do one thing at a time, finish that, and do another, then eventually you get done. One step at a time, one foot in front of the other or, "just keep swimming." It's the secret to everything, whether you're building an airplane or just trying to get through a single day. Or a single hour.

    The saying I learned before I started is: The only reason you should ever attempt building an airplane, is so that you can BUILD an airplane. A lot of people start building an airplane because they want to FLY an airplane. That usually leads to an unfinished project taking up space.

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