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When getting in and out of our legacy Sonex, we've been wary of standing on the seating area. We try to step on areas with support beneath. We are in the process of building and have not purchased upholstery yet. The seating area is a sheet of steel anchored with piano hinges at the back (under the spine) and front (under the knees). Between those two points there is no support (it feels like you are sitting in a hammock) and there is a pretty significant gap between what you and the airplane floor.

Have we have missed something? Should the seating area have additional support beneath? It seems flimsy, but perhaps it's stronger than we think.
Comments, please.

Unless somebody messed with your kit, that "sheet of steel" is actually aluminum, and nothing goes under it.

David A.

Shouldn't you be stepping on the spar to get in?

DCASonex wrote:Unless somebody messed with your kit, that "sheet of steel" is actually aluminum, and nothing goes under it.

David A.

True! And I would add that it is designed to be stepped on.

The part of the Sonex that is most structurally abused in the entire airplane is likely along the "spine" of the seat pan. Originally, the hinge along the spine was attached to an unreinforced channel section. Before long, through a Sonex service bulletin, an extruded aluminum angle was added to the top of the channel section for additional strength in that area. So the next failure on my particular Sonex was the hinge material itself that is attached to the extruded angle. Some of the hinge loops began to break off and sections of the hinge had to be replaced. The next point of failure, which has just occurred, is a crack in the seat material itself along the bend of the spine adjacent to the hole through which the seat belts pass. I've added a couple of reinforcements in this area and we'll have to see how long before another failure occurs here.

If I were to rebuild the entire seat pan on my Sonex, or if I was building a new Sonex it would be my intention to do two upgrades and they are: (1) add a doubler skin along the entire length of the spine, bent to match the corner of the pan and riveted to both the bottom and back of the pan (note that some builders have used a thicker material for the entire seat pan but they haven't said how that has worked out for them) and, (2) use a structurally upgraded hinge material along the entire length of the spine. The remainder of the seat pan installation has never been an issue.

Just my opinion,

Art,,,,,,,,,,,,,,,Sonex taildragger #95 (800 hours),,,,,,,,,,,,,Jabiru 3300 #261

Having built and flown both the Legacy Waiex and the B model, I can say that I never liked the "sling seat idea". The B model has structural ribs below the seat pan that are very much like the style that was in the RV-8 that I built. I don't doubt that a builder can fabricate seat ribs similar to the B model that would eliminate the problems with the sling seat.

I remember that the sling seat could interfere with the pitch control components of the aircraft if additional weight was in the seat. I had to make adjustments for that before I could make a safe first flight. Designing and adding seat ribs for the legacy models is the best bet in my opinion.

All very interesting, to a new Sonex owner (will take possession within the next 2 weeks).

My question would be; is this space readily usable/accessible ie can it be used to store things like the aircraft tie down kit, spare fuel filter, firsts aid kit, etc??

Skippydiesel wrote:My question would be; is this space readily usable/accessible ie can it be used to store things like the aircraft tie down kit, spare fuel filter, firsts aid kit, etc??

Would be bad from a crashworthiness perspective.

Good space for remote mount radios, agars, etc. it’s not easy to get in to in the sense of baggage storage.

Bryan Cotton wrote:

Skippydiesel wrote:
Would be bad from a crashworthiness perspective.

Care to expand/elaborate.