Hey there, this may be a bit of a dumb question, but I’m wondering why the Onex only has an Aerobatic category in its performance specifications, and if there is any way to certify in a normal category to be able to carry a little more weight when I’m not planning on doing anything other than cross-country flying. I’m a 6’4” 250lb guy, so unfortunately, any pounds I can spare will go a long way.
If the answer to this is “that’s not how experimental certification works,” feel free to just say so and I’ll get the picture!
Hey FakeLouis,
It looks like Sonex has one gross weight for the Onex, namely 950 lbs.
With an experimental, there is no certification involved. When you apply for airworthiness you can claim any max gross weight you care to, but physics still applies.
I suspect they list it as the aerobatic weight category to show you can do aerobatics up to max gross. Maybe a marketing thing. The Sonex/Waiex A and B models have an aerobatic GW of 950 and the utility category weight at a higher value depending on installed HP.
It’s a good possibility that there’s a different limiting factor for the gross weight than structural limits. When they increased the gross weight for the other 2 place Sonex they also mentions wing power loading and landing gear structural limits as being other constraints. It could also be something like meeting the clean stall speed for the old pre-mosaic LSA requirements. The different wingspan options are also something to consider.
I can’t recall if they mentioned anything about the Onex here but if you have some time it might be worth watching to understand some of their thinking:
Hey Ampzapper,
Contacted the Sonex team and it turns out your suspicion was correct! The landing gear is the limiting factor here. Since that’s the case, I don’t think I’m gonna try to mess with anything and just live with the performance envelope as is. However, it may drive me to change from a 100HP engine to the normally aspirated 80HP.
I’m a heavy guy, 250lbs on a bad day. That combined with the 600lbs empty weight and a full tank with an 80HP engine only puts me 10lbs shy of max gross (not to mention that I don’t know what weight difference the 2 Axis AP, spare Garmin G5, and Explorer Lite EFIS will make). If we add on the 25 lbs worth of turbocharger, I would never be able to take off with full fuel anyway, so I think it’s not worth it to get a little extra performance in the hot and high climates I tend to fly in.
Thanks for the insight!
You’ll have to be pretty careful with what you add or be prepared to leave a couple gallons of fuel on the ground. You should be able to get the weights of the avionics from the installations manuals. Autopilot is pretty heavy, my Dynon AP is 5 lbs. Battery type, interior and exterior finish will all be things to also consider.
Another thing that might be worth looking at if you have a bigger budget would be going with a Rotax. In theory it could help with weight and you’d get more power. I know there’s a couple Onex out there finishing up with the new mount. I’d want to see where they come out (also considering how they’re optioned) and make sure the cg would work before committing to this though since there’s a bunch of other accessories needed for installation not in the Rotax published data.
