« Archives in April, 2014

10 Hour Oil Change

8 hours.

OK, it’s the 13.2 hour oil change, but who’s counting?   I got out there as early as I could and set the engine to draining.  The cheesy quick-drain valve on the sump has an absolutely abysmal flow rate, but it has a fitting for a length of hose so you can drain it into a container and not get dirty oil all over the place.   I set it going and worked on other things.   After it had put some oil in the bucket, I took the oil filter off.   This is tricky, because the spin-on oil filter is basically a can full of dirty oil that just wants to dribble it everywhere it can.   The neat trick I figured out is to wrap a rag around the bottom of it while taking it off.

The next thing to do was cut the filter apart and have a look at the filter element.  The guys left an oil filter cutter on the workbench for me, but it was the wrong type, and didn’t work with my filter.   My filter has the threaded fitting on it, and this cutter is designed for a filter with the threaded hole.    No big thing.   I just put it in the vise and cut it apart with a rotary grinder.

I found no metal bits on the filter element.   None.   That was very cool.   That means my engine isn’t shredding some vital part of itself as it runs.  I also took out the screen and had a look at that. One solitary aluminum chip (which I suspect actually came from the bench I set it down on), and a couple of dark, non-metallic flakes and that was it.    I spun on the new filter and safety-wired it up, then replaced the oil screen and wired it.

A fairly detailed inspection showed no chafing or burning, but there was a weird discoloration on the firesleeve of one of my fuel lines.   I need to check that out, but I think it’s just from some oil that got on there before.

And finally, today, I dialed in the governor.  I had been getting a max takeoff RPM of about 2459, which was enough to get it in the sky, but the takeoff power on that engine is supposed to be 2700.   A turn and a half of the fine pitch screw on the gov, and my takeoff RPM is now 2650.   I’ll call that a win.    The weather turned out to be decent – clear skies with wind 11 at 260, so I got a chance to fly a bit.   Maintenance clock was reset to 25 hours, and I’m back to testing.

No More Wobble.

16 hours.

Going to have to sum up last week as well.   Last weekend I did the fiberglass layups on the intersection fairings.   I hate those things.  As is typical with Van’s fiberglass, the fit is garbage.   Add my lack of skill to that, and the result is a set of ugly  fairings that just barely managed to get the job done.   I may wind up reworking the whole landing gear fairing mess, but for now, these will do.   I think if I actually make them smooth and trim off the excess, I’ll get a couple of knots out of them, but the process went like this:  Saturday – Fiddle with wet fiberglasss layups all day.   Sunday – trim the extra bits off, install some platenuts for mounting hardware, go flying.

That’s when I noticed the wing wobble.  running flat-out, with ground speed at around 190mph, trimmed up, the slightest bounce on the stick would cause a divergent oscillation..  This is without the autopilot, au naturel.   Bump the stick, the wiggle starts and just gets worse.    So I had to leave it for another week.

This week:

2 hours fiddling, almost 3 hours flying.  I can live with that.   First thing on the agenda was to double check the gear leg fairing alignment.   No issue there.   Next was clocking the governor back a couple of notches on the control shaft to get more RPM on my takeoff run.  It currently tops out at 2549, when it should be around 2600-2650.   One notch is too coarse of an adjustment; I wasn’t able to cycle the prop during runup, so I had to set it back to where it was.    With that fixed,  I went up just to confirm the oscillation, and sure enough, predictable and repeatable.   So I came back down and checked my rigging.  Turns out, one of the ailerons was off.   Not sure how that happened, but whatever it was, it wasn’t enough to cause a problem with the gear fairings and wheel pants off, at least not until the autopilot was engaged.   The AP couldn’t keep up with the oscillation either.    And, because I’d read about it, I checked the trailing edge of the ailerons.  The control surface is supposed to be absolutely flat from front to back, and then it wraps around where the trailing edge is bent.   This being a quickbuild kit, you’d think they’d be just fine.   Not so.  If the surfaces bulge outward at all, they can cause instability, so you do the heavy-wing treatment: Squeeze the trailing edges so the top and bottom are flat and not curved outward.   Even a little convex is OK.   But the idea is to go easy, not even enough to notice visually.

That was the magic bullet.    Hands-off, the stick stayed rock solid.   Repeating the bump test had the wings settle back to trimmed bank angle.   The autopilot was still a little twitchy though.   The fix for that was to move the AP control linkage to the innermost hole on the servo arm.  Less motion, more precise control increments in the stepper motor.   So that was awesome.   Being able to steer the plane with the heading bug is cool.

With everything trimmed up, balls to the wall, I managed to get 192mph ground speed in level flight.   The fuel burn was absolutely decadent, but it was pretty cool to go almost 200mph.   Oh, and the oil door stayed closed, which was nice.

So I did some more speed runs and spent some time getting familiar with the new handling.   A little different with gear fairings.   It doesn’t slow down as fast, for one thing.   I landed at SZP, went back to OXR, then spent some time in the pattern.   Landings are a little different as well.