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All Together Now

Finally, after four months of interruptions, priorities, fragmented blocks of time, and truly awful weather, some of which begat the need for a new rudder, N313TD is back to operational status.

When I installed the new RDAC, I had to leave the left side CHG and EGT probes unconnected, because the wires wouldn’t reach the new RDAC location.  Yesterday, I ran the K-type extensions from both sets of probes to the new location and connected them accordingly, and as far as I know, they all go to the right terminals.  To truly test it out, I need to heat up the cylinder head and probes with a heat gun to find out which is which, but that’s not happening at a tie down in Santa Monica.   I know 1 and 3 are right.  It’s 2 and 4 that might not be.  You see, I ran the wires and wrapped them in spiral wrap before I thought to mark which was which.   The photo above shows a messy, but functional arrangement with enough extra wire to allow switching terminals, although I believe I can set them in the EFIS.  At that point, I can clean them up and make them all nice.  But for now, they’re secure and self-supporting, so I’m good.

The other thing that happened on the way to the new RDAC module was that I somehow picked up an extra 2500 ohms between the fuel tank and the Fuel Level inputs.  This new RDAC has a DIP switch for a pull-up circuit on most of the sensor inputs.  The manual says you’re supposed to have the pull-up on for float-type senders, but if it’s on, the resistance drops to zero and the fuel level reads full.  Not useful.

With the pull-up circuit off, ~8 gallons reads about 1500 ohms, according to the raw level reading in the EFIS.   One of my tanks is pretty much there, because I leveled the airplane and the fuel on the left side is juuuuuust touching the outboard rib of the tank.  So I half-assed it using the settings below until I can properly calibrate by emptying each tank and adding back 3.5 gallons at a time.   The gradations are from the previous measurements.

Opinions are strong on this, with most of them in the key of “you should use a totalizer and do the math” and “if you keep track of what you put in and the time you fly, you don’t need a gauge.”   But the saner voices acknowledge that fuel gauges are a good redundancy to a totalizer, and I tend to agree.  Either way, I now have everything I had before the old RDAC went tits-up, and then some.  #1 and #3 CHT’s aren’t randomly dropping out anymore, and the left-side fuel level doesn’t randomly jump from its normal reading to full tank.  The EFIS is still a mess.  I can’t get it to take the latest update and it can’t read any of the raster maps I’ve uploaded, and I’m getting pretty damn good at QGIS, so I’m not as happy with it as I should be.  But it’s still performing well for a 2010 unit that’s no longer being manufactured.

Did I mention I was doing this stuff outside at a tie down at SMO?  Yeah, about that.  No electricity, so no luxuries, specifically, no heat gun, which means yours truly was shrink-wrapping wire with a barbecue lighter and a cupped hand.

All repairs are field repairs, yo.   Can’t wait to install the Fed-mandated ADSB equipment before 2020.

Oil Cooling hell.

Yesterday, I went from having a flying airplane back to having a project.  For quite a while now, my oil temperatures on hot days and climbouts have been marginal to unacceptable, and since I have the break in the work schedule, I figured I’d do something about it.   So I joined the Compton EAA chapter and rented a space in the hangar for a month while I sort it out.  My oil cooler is the stock Van’s 7-row Niagara oil cooler that seems to work on most RV installs, but not mine.   There are a few reasons this might be: timing, blow-by (which would suck, the cyls are more or less new) bad baffling (worked when I first flew, so wtf) or carbon deposits in the cooler.  It’s actually fine as long as the OAT is 65f or below.  I can settle in to cruise at 190-195F no problem.  But on hot days, or long climbs, I will go above 220 real fast, and that’s no good.   Last year, I purchased a 10-row cooler with the intention of replacing the stock one, but I never put it on.  I first attempted to seal up any baffle leaks.  This improved things a bit, but not enough to matter.  Cylinder head temps are fine.   I’ll hit 400 on those if I mash it and rabbit up to 10,000ft, but they cool down pretty fast once leveled off, and usually settle in around 350-375.  I’m sure there’s more I can do, but for now I need to solve the big one.

The 10-row cooler will not fit on the back of the baffle like the stock one does.  It’s too wide.  There are a number of ways to mount the cooler on the firewall, but none of them work because my firewall is already full of stuff, namely the RDAC, fuel pump, and brake line fittings.

I supposed I could probably move the RDAC and fuel pump, but that’s less appealing to me than mounting on the engine mount and connecting it with a SCEET tube to a flange on the baffle where the original cooler was mounted.

So it’s off to Compton I go, first to do exploratory surgery, then some design work, and then hopefully some fabrication.  They have ALL the tools.

Annual Inspection 2015

Believe it or not, it’s been a year since 313TD was given its special airworthiness certificate.   In that year, I’ve put 65 hours on it, which is respectable.   But alas, no matter the hours, the regs say you have to do an annual inspection.

I won’t bother posting the whole list of items checked, but I did find a few things I wasn’t terribly happy about.

  • Throttle cable got a little too close to the exhaust.  Operation seems fine, but the plastic wrap is bubbled slightly where the heat-wrap runs out.   It also chafes against the fuel pump.   I wired up a fix, we’ll see if it stays.
  • The wires going into the lower rudder cover are a little chafed.   Wrapped ’em up good.
  • Left side fuel vent line fitting was loose.  Blue residue inside the wing root fairing.
  • The screws holding the spinner on were crap.  Two of them stripped out and had to be removed via drill.  Replaced all with 6/32 stainless.
  • Stripped out a mag screw.  Why do they make those things with Torx fittings?   Suck it, Slick Aircraft.   I was able to drill off the screw and replace it with a slotted one like it’s supposed to have.
  • Fuel hose from throttle body to injection spider was loose at the spider.   That’s the only really scary one.  But this is what inspections are for.
  • Left aft wheel pant cracked.   I think I may have jammed a chock under it a little too hard at some point.  I have to fix this over the weekend.

To do the job, I rented some floor space from Andre over at Bill’s Air Center.   Once I got in, I was able to do the job in 3-4 hour chunks, using  mostly my own tools.     The guys there are awesome!   It really helps to have several master aircraft mechanics occasionally looking over your shoulder and helping you out with the hard stuff.   But really, most of the pain is dealing with access panels.   So many screws.    I have a few things left, but mostly I wanted to get out of the shop and give Andre his floor space back.    Here’s what’s left:

  • Adjust Idle.   This is the biggest one.   I re-timed the mags, and it looks like they’re better than the last time I did them, plus with a set of clean plugs, the engine runs way better.   Problem is, the idle is about 200rpm too high, and it stumbles a bit on throttle advance.   I suspect this is because of the change in timing.
  • Fix wheel pant.   Without this, I can’t fly.   That happens ASAP.
  • Reinstall interior.   I took most of it out and left it at home while I was working.   Seemed like the smart thing to do.
  • Fix o-ring on right fuel drain.  Fuel leaks are not cool.

I also fixed a couple of things that were annoying me, like the canopy latch being too tight to allow smooth operation.

So once I get my to-do’s done, I’ll make a logbook entry certifying its airworthiness and take it for a test flight.