OPERATING AND MAINTAINING A SONEX

[SonexN76ET]

I would like to start a new topic here that I hope that we can build on to help all of us to safely operate and maintain a Sonex aircraft. All aircraft types have certain things that wear out or need additional attention. For those of you who have been operating your aircraft for awhile, can you please provide some insight into:

- Key inspection items to look out for? Or what do you look at before each flight?
- What have you seen wear out?
- What have you seen break?
- What have you seen come loose?
- What have you seen that needs frequent adjustment?
- What have you seen that needs periodic adjustment?
- What are some of the critical items you always keep an eye on?

For instance, I check the small cotter pins in the control surface piano hinges before each flight. I have often wondered if anyone ever finds one missing. I have also heard that the piano hinges in the cowling get looser after awhile and people have to put some type of a keeper in place to ensure that they do not work there way out. I also check the bolts on the landing gear periodically to ensure that they remain tight. I also torque my prop at each oil change. But, I would like to hear from others as to what your experiences are.

I would like for this to be a healthy exchange of information based on what you have actually seen or experienced. This is not the forum for opinions or hearsay. It is a forum for tangible information that all of us can use to ensure safe operation of our aircraft.

Thanks,

Jake

[MichaelFarley56]

This is an EXCELLENT idea Jake! Thanks for creating this and I can't wait to read the responses people will offer.

For myself personally, I'll start a list but most likely I'll edit it down the road as new reminders pop into my head. These are things I do in addition to or put special emphasis on during my preflight. This isn't a coclusive list of my preflight items; just things I really watch for.

Preflight

- Check to ensure all cotter keys are properly secured at the end of each control surface piano hinge.
- I've covered the cotter keys at the end of bolts/castle nuts with 'torque seal' and I check to make sure the torque seal isn't cracked or missing (this would indicate possible movement)
- For my Waiex, I ensure the torque tubes for the ruddervators are secure but still move and twist freely a small amount
- No cracks in the fiberglass tail tips
- Nothing is left/missed in the flap sockets in the aft spar. I normally leave my flaps down in the hangar and wouldn't want a rag or tool to jam my flaps down
- I check the ends of the torque tubes on my flaps and ailerons for security.
- I check the outer wheel pant screw or bolt that threads into the axle. They can work loose.
- I check to make sure my wheel pants are secure and I can't move them.
- I check to make sure there's no oil leaking out the bottom of my cowling
- I check for cracks on the prop very closely
- I check to make sure all hinge pins for the cowling are secured and can't work their way loose.

Engine Start

-The biggest thing I'm looking for here is proper oil pressure right away.
- Engine smoothness as well.

Takeoff

- I check my radio (FL-760) to make sure I'm not accidently transmitting non-stop
- Canopy is secured!
- I make sure I'm hitting appropriate RPMs and oil pressures at the beginning of the takeoff roll.
- As I climb, I make sure my engine temps and pressures are all normal

Ending the Flight

- I always take the time to wipe down my prop and make sure it's clean. This lets me check for nicks or cracks that would need addressed.
- I usually wipe down the wings, tail surfaces, and cowlings to get rid of summertime bugs. This lets me look things over well.
- I take a look in the engine compartment and underneath the airplane for signs of leaks or loose items.

Before I Close the Hangar

- Fuel valve is OFF
- All switches are OFF
- Canopy is CLOSED and LATCHED

Items that Wear Out

We are vely blessed with a great airframe that can withstand normal wear and tear without any issues. I've been very lucky overall by not finding much wrong that's Sonex specific. For me, the items that get checked and replaced are pretty "airplane generic"; check the tires regularly, and change the oil. I always try to have a few extra VW oil change gaskets handy and just like Jake, I will check my prop bolt torque and prop track every time the cowling is off. Finally, even though it doesn't always look like it, I really try to keep the whole airplane clean, inside and out. I think this makes identifying problems much easier as things are easier to spot.

[kmacht]

I am just coming up on 10 hours now but thought I might be able to add to the list a little bit based on what I have seen so far.


- What have you seen wear out?\
I had the bearings in my tailwheel wear out after just a few short hours. The sonex sounded like a shopping cart when landing. I thought it was just the hard tailwheel but when I pulled it there was a lot of slop in the wheel bearing. I replaced it with a spare and it is much quieter. I don't suspect that they will wear out that quickly normally. It is the same tailwheel I had on for the past 9 years of building so I am guessing that there was alot of gunk that got in the bearings over the years especially during the painting and prepping process.

- What have you seen break?
I had the electronic ignition fail on me in flight at hour 8. The trigger magnet embedded in the little round cap that you adjust for timing came loose and went missing. It is only held in there with a little bit of glue. It failed on the first cold morning that I went flying. I suspect the glue became brittle and let the magnet go. The good thing was that I didn't even know it failed until I tried to start the plane for another flight that day. The mags kept the plane running with almost no noticeable difference, they just wouldn't allow the plane to start again since the starter doesn't spin fast enough for them to generate a strong spark.

The only other thing to break was the sump plate during the 10 hour oil change. I had the old stamped metal one and the threads that hold the plug in stripped out. I replaced it with a machined aluminum one and don't expect any further problems.

- What have you seen come loose?
The outer wheel pant screw (the one that goes into the axle) seems to keep wanting to loosen itself up. I now check it before every flight. I added a rubber washer to it and that seemed to help quite a bit.

- What have you seen that needs frequent adjustment?
Not much. I'm still playing with the mixture on the aerocarb. It has run fine since day 1 but I find myself still adjusting it trying to find a happy medium that doesn't require many mixture adjustments when flying. I had it all set right up until the cold weather set in and I had to make it a 1/2 turn richer.

- What have you seen that needs periodic adjustment?
Again, I have only a few hours on my plane so not much has needed adjustment yet. I was surprised at how much the head bolts moved when they required re-torquing at 10 hours. I have also had to replace my intake rubber adaptors a few times. Once they get hot and then cold again a few times they get a set shape and it is very hard to remove the intake tube without cutting them off. I have had to pull the intake tube twice. Once to get the elbows off to torque the head bolts and again to pull the battery.

Keith
#554

[daleandee]

I just kick the tire and light the fire ...

:P

Dale
N319WF

[N111YX]

For the most part, my Waiex has not required any unique replacements or adjustments.

However, off the top of my head, some operating notes...

Aileron slop may develop over time. This is noticed by lightly moving the aileron trailing edge by hand and feeling perhaps 1/8 inch travel before the other aileron moves with it. The solution is to check the rod ends and look for the slop there. Most likely, one just needs to spin the castle nut tighter to the next hole to accept the cotter pin. I looked a for-sale Sonex one time and there was about 3/4 inch "loose, floating" travel on one aileron. Probably a good flutter source right there.

The Waiex uses a taper pin to prevent such slop in the ruddervator mixer but that too is susceptible over time with use and can be fixed the same way. I use (and highly recommend) taper pins in the control sticks to prevent slop. I can't stand to have a quarter inch back and forth slop in a stick before aileron movement.

I have had to tighten the bolt that goes through the titanium tailwheel rod also. Landings will work in some play that is evidenced by being able to rotate the tailwheel assembly left and right likely with a squeak.

My tires will be below a comfortable PSI in about a month or so. If I had to do it over again, I might take the time to add little doors to the wheel pants to access the tire stem. Much easier than taking the pants off.

Try to have a soft material or maybe use rubber grommets between the canopy material and the aluminum strip attached to the bow otherwise you may see whitish Plexiglas dust around the area as the canopy rubs with vibration.

If you have the old, rubber "Thermos"-style gas cap, it's only good for a couple hundred cycles before the rubber part fails. If you smell fumes or can't tighten it easily, it may be time to change it.

Also, the use of a split washer helps keep the outer bolt holding the wheel pant on.

If I think of more, I'll be back... :idea: