Sonex-A purchase - What to look for

[Area 51%]

Also, one spring that connects the two sections of the exhaust on one side is stretched nice and tight, and the other one is much less tight. Is this an issue? Also, the previous owner ran safety wire down the middle of the exhaust pipe connector springs. Is this necessary?

I personally believe it a necessary add-on. Springs can lose their tension when they get hot allowing the pipes to separate and vent exhaust gases directly on the injector/carb. I experienced such a failure that caused total vaper-lock with a resulting uneventful emergency landing.
At the very least, if you wrap the pipes, keep the springs on the outside of the wrap.

[BRS]

I used to fly a gyroplane, think pusher propeller. The exhaust had about six springs which did a real job when going through the propeller. Wire through the springs were a must. The other thing we did was to run a generous bead of high temp silicone across the stretched springs. Gotta do what you gotta do. In the Sonex I guess it's more about not torching things under the cowl as it's not so likely a runaway spring is going forward.

[Hambone]

Thanks for the replies. I'll run safety wire in the middle of the springs. It can't hurt, and could possibly help.

[bvolcko38]

Add some red RTV to the springs...it keeps them from vibrating causing metal fatigue.

[Hambone]

So I finally flew the Sonex from the airpark to the local airport after installing the new heads, and getting a fresh conditional inspection.

It was a rather eventful experience!

Engine was running well, takeoff was uneventful. I had intended on climbing overhead the airpark to give the engine a good run before heading over to KGOO, where I wanted to practice some approaches before landing. However, the CHTs starting climbing a few minutes into the flight. I leveled off, let it cool, and recommenced the climb. After a few iterations of this, I had only climbed 2,000 ft. I really didn't want to return to the airpark, so I headed over to KGOO, only 6 miles away.

Enroute, the engine started running rough. I leaned the mixture a bit, and this helped. But I really wanted to get it on the ground. Entered 45 to downwind at 100 mph, turned base still at 100, and pulled the throttle to idle and lowered 20 flaps. Idle all the way from base to final, and still almost 100 mph. The engine wouldn't idle below 1200 RPM. No problem, I thought. I'll just hold it a few feet off the ground, let the airspeed decay, and land. This was all going well, but after I touched down, I let it get a little bit sideways, which broke one of the wheel pants in two. I was paying more attention to the rapidly approaching end of the runway rather than keeping it straight after touchdown.

So now I'm concerned about the landing gear. Getting sideways must have imparted a side load on the wheel and axle, and to me, it looks like there's a little more camber than there used to be. It must have taken quite a load to cause the tire to contact the inside of the wheel pant hard enough to split the wheel pant.

Anyway, I learned a lot, and lived to tell the tale. I hadn't flown in a while, I didn't like the rough-running engine, and I let myself get behind the aircraft. Maybe I should have gone around and set up a more stable approach. Hopefully there's no permanent damage to the gear. I'll need to figure out how to check it for safety before I fly it again. In the meantime, I'm going to try to adjust the mixture, idle speed, and timing in an effort to get the engine to run smoother and cooler.

[Bryan Cotton]

That's a bummer! The gear is pretty stout but people have bent them. From the description it seems unlikely to me that it's bent. It's pretty springy gear. But I'd check it visually for straightness and pull the wheel off to inspect the axle. That's an easy job and the bearings need periodic service anyway.

[Hambone]

So... on to the next adventure!

Nice cool day outside, so I thought I'd take it up and just fly a box pattern over the airfield to see how the cooling is doing. Leaned engine for max RPM at beginning of takeoff roll, after rolling, RPM dropped a bit, so I went full rich. Smoothed right out at 3120 RPM. Rest of the takeoff was uneventful. On initial climbout, engine was running rough, leaning a bit smoothed it out nicely. CHT hit 420 during climb. Leveled off at 5,000', and played around with the throttle and mixture to evaluate cooling. Could get 2950 RPM with CHT 350 as long as I was going at least 110 mph. Changing the mixture didn't make much difference. So I'm going to work on the baffling to see if this helps. Oil temp only got up to 90-100, so I should have probably plugged the oil cooler intake.

Flew for about an hour, so it was time to land. All was going well, until I touched down on the mains a little fast, and when I lowered the tailwheel to the ground, encountered a substantial wheel shimmy that pulled me off toward the side of the runway. I overcorrected, overcorrected again, and before I knew it, I was in the infield grass. Nothing damaged except my pride. I'm wondering if the wheel alignment was altered during the 2000 mile drive in the UHaul, or did I bend something during a marginal landing when flying the airplane here.

Now I should have known about the shimmy. The day before, I adjusted the tailwheel linkage to get it to track straight, and did 3 high-speed taxis to confirm it. I noticed the shimmy, but thought it just was my ham-fisted (footed?) s-turning down the runway, trying to track straight.

Anyway, I was pleased with the engine cooling. I don't think it's that far off, and I now realize that it needs special care and handling, especially during climbs and pattern work.

So I'll get someone to help me pull the wheels off, and we'll see what's going on.

The adventure continues!