Condition Inspection @ 564 hours

[GraemeSmith]

Sonex Legacy S/n 1153
564 hours on airframe
564 hours on AeroVee which was top overhauled (cylinders and pistons) at 472 hours last year
141 hours on current installed Prince P tip which was my spare put on when original needed a little epoxy reseal on the trailing edges by the hub. It is in the box as my current spare.

I have flown the plane 380 hours since buying it from the builder at 185 hours. It lives outside on tie downs on the coast and gets beaten about a bit by weather with little shelter once the winds are sweeping the tie downs.

I went into this knowing a lot of what I wanted to tackle. The plane has been getting "loose" feeling - like well worn in - without anything demonstrably wrong. Indeed the supervising AP commented it looked like I was taking it completely apart in places - just to put it together again. But having broken 500 hours this year - it was time to look REALLY hard at everything.

You can follow the daily reports with extensive photographs on the FB group but the principal issues were:

- Bearing wear in rod control system, evidenced by a slight "snick" when lifting the trailing edge of the elevator. I bought the bearing kit from Aircraft Spruce, started at the back and worked my way forward - replacing all the bearings, bolts, washers, nuts and cotter pins. Many would have been a "pass" - but as I was in there! The worst - that definitely contributed to the "snick" in the system were the two bearings holding the dual stick yoke to the frame on the floor of the aircraft. Once freed of the system - these bearings were demonstrably a sloppy "fail".

The other (surprising) bearing slop was in the big bronze bush bearings where the PILOT stick pivot is located. Both these bearings had a surprising amount of slop in them when pulling fore and aft. They might have got a "you could leave it till next year" - but as I had the kit and was in there. The rarely used passenger stick bearings were quite satisfactory.

The aileron bellcrank bearings in the wings were a fail last year and were done last year. The design leaves a lot to be desired from the point of view of changing the bearings after the holders are rivetted to the rib. You have to cut an inspection panel and then drill rivets to get the bearings out.....

- Tailwheel. Sonex 6" hard rubber wheel. I replace the bushes in that annually. Failure to do so means the aluminum part gets chewed and then it needs new aluminum.

- Left main axle replaced. Planned - the little tab on the bottom that holds the brake shoe mount plate had cracked and the plate was moving - which was messing up the brake setup. I took the old axle off, jigged it on the drill press to "find the axis" of the securing hole / toe in angle. Then put the new axle in the jig and drilled it to match. Fitted with all new hardware.

- Right main - discovered the axle was moving fore and aft about 3-4 degrees. On drawing the securing bolt - found it necked and ridged. Replaced with all new and all well. However this meant I didn't trust the top bolts holding the gear legs into the motor mount - so I drew both of those and replaced with new. They were a "pass" but there were wear lines developing.

- Underside of horizontal stab - right side. A touch of "frost" developing. It's just a function of being outdoors on the coast. Scotchbright soaked in CorrosionX to remove. (Plane gets polished in April)

- Cylinder heads - I keep a spare and serviced set ready to go. I really don't trust the valves after 100 hours though I am VERY careful with CHT's and EGT's. I replace the exhaust valves as a matter of course every 100 hours (via my ready to go spare heads). Nothing untoward while changing the heads. But on the test flight - the engine is running demonstrably better and is back on her numbers more precisely for CHT/EGT. Examining the heads that came off this time and working the valves. An intake valve was happily stuck in its seat and the seat was moving up and down in the head - acting as the valve. EMPI heads. And NOT the first time this has happened. Though the previous time was when the seat fell across the valve and the cylinder lost all compression. Exhaust valves don't look burned though they have plenty of deposits on the backs and stems. Par for the course running 100LL with Decalin to help scavenge it.

- Ground up rebuild of the brakes, starting with new levers in cockpit (old ones were developing slop and twist), new cables, complete going over of the security of the backing plates and fit new shoes.

Things I was pleased about:

- Tailwheel mount, rudder post and horizontal stab structure. Firm and clear of any corrosion. This is kept treated with CorrosionX and once all confirmed good - reapplied.

- Careful mirror, bright light and photograph inspection down inside empennage and deep into wing roots and up above top of fuel tank. Rudder and Flap bearing blocks. All good. CorrosionX reapplied.

- Main sparbox - borescoped and all looked good. Reapplied CorrosionX

- Thorough inspection of all welds on motor mount and rigging control rods. All remain well painted and powder coated. Dye Penetrant testing on some randomly chosen welds showed no cause for concern.

Principally - it was all about wear and tear and replacing stuff that can be replaced.

On the return to service flight - the plane felt quite different - like when you change the clutch on a stick/manual car and the engagement point is slightly different. She feels "firmer" on the controls and the engine is back to full power.

I think that covers it.

YMMV

[GordonTurner]

Thanks Graeme

Careful reading of your carefully written “not quite autopsy” (let’s hope not) is an excellent guide for novice mechanic.

Appreciate the effort and thoughtfulness, and for sharing.

All the best, Gordon

[Bryan Cotton]

Excellent report, thanks Graeme. I'm at 59 hours and climbing.

[Weatherpilot]

As a new owner I truly appreciate your report. Gives me some idea of things to check on my airplane as I prepare for first "new-to-me" flight. I have decided to and scheduled a condition inspection with my local A&P/IA to make sure we have a comprehensive look at everything.

Thanks!

[Wood]

Thanks Graeme
Great read. I’m coming up on that time as well. Did complete valve job last year so that’s looking a little closer look at everything else this year.
Thanks for this

Mark