SonexBuilders.net

Hey all,
I thought I would start a thread on flight test. I'd like to share and discuss methods, requirements, and similar topics.

I'll go first - aft CG testing. This is covered in AC90-89B, paragraph 6.1. This is actually in conjunction with max gross weight testing. One of the challenges in the Sonex series is the fuel is a major contributor to longitudinal CG. As you burn fuel it moves aft. So, if you are ballasted up to MGW and aft CG, and are flying around doing stalls and the stuff called out in AC90-89B, you will be burning fuel. So, what do you do? Take off over gross and get to a safe stall altitude right when you hit MGW and aft CG? Then when you return to land you will have burned off fuel and be beyond the aft CG limit. Or do you fly the maneuvers close to the limits but never exceed them?

I'm about to go out and start working on ballast. It seems that as I add ballast against the seatback I will have to ensure I land with enough fuel to keep within the CG range or at least darn close to it. I'll share my ballast pictures and invite any contributions for a safe way to ballast a Sonex.

Used 25lb bags of whole kernel corn. Slid a couple down onto the floor under the tank for landing.
Fed it to the deer after testing.

Crap! Now I have to buy some deer!

Clever idea.

I used water softener salt, made sure no bags leaked salt into the plane. The corn would have been better but I didn't have any deer either.

I used 50 lbs. bags of play sand from Home Depot & aviation supply. I started off with two bags and added the rest one at a time after a few flight tests. Once you get to gross it's good to leave them there and fly a few hours and really get a feel for the plane. Just be sure you have whatever you use secured so that the weight cannot shift or move in anyway to block or jam a control. One builder used some barbell weights from the gym.

With the Aerovee do your first gross weight flight early in the morning when it's cool and smooth. Having said that I did test my former Sonex (Aerovee powered nose dragger) to a gross of 1150 lbs. It wasn't scary but it wasn't spectacular at all. With my current configuration (3.0 Corvair & tailwheel) gross testing was to 1250 lbs. Climb was good and the plane handled very well as my C/G range came out excellent.

Be careful and have fun!

For an RV-8, I used reams of copy paper. CASES of copy paper. I think I finally used the last of it maybe 15 years later :-)
Rusty

Interesting thread!

You guys put a lot more effort into this than I did: I built the plane with everything as far forward as possible- empty weight CG for the finished plane turned out smack at 20% chord (forward limit).

Filled up the tank and did some stall tests- no surprises. Burnt off fuel while stalling around up there- when I finally tired of this there was perhaps 3 gals left in the tank. Filled up the tank again and loaded the pax seat to max gross 1150 lbs with properly secured (!) sandbags. More stalling around up there with the fuel slowly bruning off- still no nasty surprises.

We´re not allowed to spin LSA´s up here, so I had a qualified test pilot do this for me, first only him and later on with fatty me next to him and in both cases half full tank. The tests only confirmed what already has been known for decades: the Sonex is a docile and predictable aircraft, coming out of the spin with the standard procedure.

Good enough!

I had a separate shop building at the time that was heated by a good coal stove, so Old King Coal was my first passenger, In 40 lbs bags.

David A.

DCASonex wrote:I had a separate shop building at the time that was heated by a good coal stove, so Old King Coal was my first passenger, In 40 lbs bags.

David A.

You had King Coal and I had Mr. Sandman! lol

Bryan Cotton wrote:Crap! Now I have to buy some deer!

Clever idea.

I have a small herd sleeping behind my hangar so...