Maintenance: Third annual condition inspection.

Time for the third annual condition inspection (here are the first and the second) at 230.8 hours (see here for my POH, W&B, flight and annual checklists and flight test cards) and 1,611 gallons of avgas burned.  The annual took nearly 40 hours over 3 weekends.  A number of interesting findings turned up, as outlined below.

Oil leak:  Found some oil that I hadn't seen before...

I believe it's coming from where cylinder #1 mates to the crankcase.  Knowledgeable folks advise me not to worry about it and to keep an eye on it.

Nosewheel breakout force:  During my first condition inspection in 2018, I could get either 17 or 42 pounds on the nosewheel breakout force (see page 40A-07) due to the cotter pin alignment.  It's supposed to be 26 (which it was prior to first flight).  It escaped me (despite it being clearly written in the plans) that one can drill a new hole in the U-01406 Nose Gear Leg to accommodate a greater range for breakout forces.  So I drilled a new hole 90 degrees from the existing hole (shown below following drilling and test fit of cotter pin).  And magically, I got exactly 26.7 pounds on the breakout force (with new grease in the fitting).

Brakes:  They drag ever so slightly.  Back in December 2017, I did the canonical spring modification.  But, you could still hear the brakes drag when pulling the plane out of the hangar and even a bit of squealing when taxiing.  Long story short, I pulled off the caliper assemblies, cleaned up the pins then lubricated them with LPS-2.  However, what I believe was most important was to reposition the brake line so it wasn't torquing the assembly.  The assembly now slides a lot easier (following flight after this inspection, it appears to have solved the issue).   I went ahead and replaced the left wheel's brake pads (the right's were changed in 2019).  They didn't need to be, but I felt better getting them replaced now so they match the right side's more closely.

Wheels:  Both main tires replaced (the nose's is fine).  They were rotated in 2019.  The left one needed to be replaced.  The right one could have kept going.  I will monitor the wear more closely this time and if it continues to be asymmetric, I may consider shimming one of the axles.  Or maybe it's just bad piloting skills.

Elevator idler pulley:  I noticed a little bit of slop here.  When I pulled the bearing's bolt out, I found it was an AN4-12A.  It should have been an AN4-11A (per 36-02).  Oops.  Probably not going to bring the bird down, but it sure makes one wonder what else I missed.

Alternator filter:  I was proud of myself for figuring out what I thought was an elegant install.  It wasn't.  Turns out that the metal hood that I bolted the filter to could not be recruited into the task of holding this relatively heavy filter in the punishing environment of an IO-390.  I'm quite fortunate that the filter didn't completely separate from the airframe and depart the cowl in flight, doing damage to something or injuring someone.  This was a very educative experience and a potent reminder to stay within the bounds of my knowledge:  Don't do something that hasn't already been shown to be safe.

Fuel filter leak: I was pleased to see that my fuel filter was quite clean (left).  However, I was not pleased to see that there was another fuel leak in that area (right).  At last year's condition inspection, the fuel pump leaked due to the way it's constructed and how torque applied to its fittings is carried through its body.  See this post for information.  During this inspection, when I opened the inspection cover and saw the leak, I was amazed that I never smelled it since last time, it was the odor of fuel on opening the canopy that led me to find the original leak.  

I believe what may have happened is that the thread sealant on the NPT fitting between the filter and pump wasn't fully cured before flying.  So the leak happened only once and I never smelled it since the odor went away.  I could be wrong on that assessment.  I will be opening the inspection plate after the first post-inspection flight to try to verify.

Wing gap fairings, pan head to flush: Curiously, the plans specify that the 7 aft-most screws for the F-1411B Lower Wing Root Fairings should be pan head screws, as clearly evidenced in the following images from the plans (41-05, 41-04 and 29-18, respectively).  With the plane finally assembled back in 2017, I couldn't understand why those screws were specified as pan heads.  Yet, if you look very closely as Figure 3 on page 29-18 (not shown below), you can see that the protoype used K1100 flush nutplates (rather than the K1000 called for in plans).  So I decided to swap mine out to go flush.

 

 

The three aft-most nutplates could easily be removed from under the aircraft.  The second and third one back were more easily removed from the top using 12" long bits at a deliberate angle.  The fore-most nutplate was removable from below, however the wing spar is along the trajectory of the drill bit so I used a spring drill stop to prevent a catastrophe.  It was easy to dimple the skins using a screw with lots of Boelube on its head by just screwing it into the nutplate until it offered resistance.

Here are my replaced nutplates.  In the left image, you're looking down the gap with the wing on the left and fuselage on right).  The nutplate under the wing spar could not have its rivets squeezed or bucked due to the wing spar, so I used CCR-264SS-3-2 (right image looking inboard from the bottom of the left wing).

Now the Lower Wing Fairings are nice and flush (don't mind the in-process RV-14A tail in the background) so I'll get my 0.01 KIAS back.

Clean belly: My belly was an oil slick.  Now it's clean (can't say the same for the nosewheel fairing).

Engine borescope: Piston, cylinder wall, exhaust and intake valves of cylinder #1 shown.  All looked fine for this and the other cylinders.

Spark plug insulators broken:  Upon pulling the plugs for cleaning and gapping, I was greeted with broken insulators on #1T, #1B, #3B and #4T (top right, top left, bottom right, bottom left, respectively).

This caused quite a learning episode (experimental aviation is supposed to be for education right?).  This is evidence of detonation (not pre-ignition).  Using my comprehensive data analysis program, I combed all the engine data from every flight since my last condition inspection (which was the last time the plugs were serviced).  I was looking for any indication of a runaway CHT.  I could find none.  

I called Lycoming's technical support and was immediately in touch with a great technician (who ironically signed my engine's test run sheet at the factory in 2015!).  We had a one-hour long conversation whereupon we discussed how the engine was operating, how I was operating the engine, I sent him pics of the plugs, the borescope pics, the oil leakage and the fuel servo cable rigging.  We went over some performance numbers of the engine on takeoff and found that I was consistently running 4 to 5 GPH lean!

The technician offered several things to check:  Fuel restrictions (kinks in fuel hoses, verifying fuel flow through injectors), verifying mixture arm hits the stops and finally checking that the fuel servo is flowing properly.  We also discussed my approach to leaning for takeoff:  Slowly lean mixture until rough, then richen two or three turns (an approach I've used in every aircraft I've flown - which is a whopping 4 different models).  He indicated that that was the correct approach.  So I came away from that call thinking, perhaps erroneously, that my fuel servo might need to be recalibrated.  

The technician didn't see any evidence of severe detonation (e.g., clean pistons) in the borescope pictures. He advised to fly the airplane and not be concerned with possible damage.

After replacing all of the spark plugs to the tune of nearly $300 (!), and learning about fine wire vs. massive, my plan was to richen the mixture on takeoff until I hit a target flow rate appropriate to the altitude here (calculable from Figures 3-2 and 3-3 in the IO-390 operations manual).  If I couldn't get the correct flow, I'd abort the takeoff and pull the servo for servicing.   A friend advised that I change my leaning process for takeoff to instead lean until the first cylinder's EGT peaks, then richen to 100 degrees ROP.  The IO-390 manual states to go full rich for takeoff and only lean it out if it runs rough (e.g., at a high altitude airport - like mine).

I do believe I know when the detonation occurred.  My flight review was last month and we did a number of simulated engine outs when it was relatively hot outside.  The engine was worked probably harder than it ever has been.  Thus, the CHTs were relatively warm on those takeoffs and being fuel-starved and lean, conditions were probably good for detonation.  Though again, nothing in the engine data evidenced detonation on that day.  Turns out, detonation can be utterly transparent to the pilot and within the engine data.

Finally, after 3 weeks, the aircraft was buttoned up and ready for flight.

I was able to get the proper flow rate on takeoff.  I still need to compare with other RV-14A owners here in the area to see where their mixture is set for takeoff to see if perhaps my servo needs adjustment.  The brakes don't drag and since the nosewheel breakout force isn't overset, the aircraft is much more compliant on the ground.

That is one clean belly.