Flight test discussion - Phase 1

[Bryan Cotton]

Don't forget. If you spin test at a max gross weight of 1100 or 1150 depending on your engine's HP, you will be 150 - 200 lbs over the max aerobatic gross weight of 950 in a Sonex.

True. Most Cessnas are certified for spins but not acrobatics. So the question is really "can you teach spins in a Sonex?"

If yes, I will do the first spin with ballast rather than a passenger.

[Rynoth]

True. Most Cessnas are certified for spins but not acrobatics. So the question is really "can you teach spins in a Sonex?"

The smaller Cessnas like the 152/172 are typically Normal Category and also Utility category at certain weight/cg limits.

(1) Normal category, for each airplane intended for nonacrobatic operation. Nonacrobatic operation includes all maneuvers incident to normal flying, stalls (except whip stalls), and turns in which the angle of bank is not great than 60 degrees.
(2) Utility category, for each airplane intended for limited acrobatic operation. Limited acrobatic operation includes all maneuvers incident to normal flying, stalls (except whip stalls), spins (if approved for the particular type of aircraft), lazy eights, chandelles, and steep turns in which the angle of bank is greater than 60 degrees.
(3) Acrobatic category, for each airplane intended for use without restrictions other than those shown to be necessary as a result of required flight tests.

You can't do a loop in a Cessna that doesn't go beyond Utility Category, but some of them are approved for Utility Category spins with certain W/B ranges.

It's actually a bit tricky to find information on when a Sonex/Waiex is in the Utility Category (online anyway.) I don't have my flight manual handy, but I did find this online for the Xenos: https://www.sonexaircraft.com/documents ... page28.pdf

[GraemeSmith]

All Cessna 150/152 that are still stock (in the sense that an STC modification has not been made that disqualifies them from spinning) are Utility Category and are approved for spins - AS LONG AS the "Rudder Stop AD" has been complied with - by the fitting of the bigger rudder stop kit. Aircraft that have not been fitted with the rudder stop kit still comply with the AD but have to be placarded against intentional spins.

The Cessna 172 can be spun if loaded such that it is in the utility category envelope on the W&B. However with the modern American physique - you have to leave a lot of fuel out to get the loading correct and the endurance with the required VFR minimum fuel on landing means you don't have much time in the air to accomplish much training.

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The legacy Sonex (which I am familiar with) loaded at 950lb or less and if in the CG range defined in the yellow owner manual provided by Sonex - is in the Aerobatic category and thus can be spun. (Which essentially means one person and fuel)

Otherwise the aircraft is in the utility category and per Sonex is not to be "intentionally spun".

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The numbers are different for the other aircraft as can be seen by Ryan's link to "Page 28" - and should be checked for your aircraft model as I am not familiar.

[Bryan Cotton]

With my prior ballast configuration, I was near the aft CG limit and really had to be careful with my fuel level. Burn too much fuel, go too far aft. So I reconfigured to move the ballast forward. I removed the right stick and built a wooden deck.

I added a 25 lb bag of Oil Dri to move the heavier ballast forward, and secured it again. I had to lengthen the lap belt.

Now I'm not too far aft until the last couple gallons of fuel. I like it.

Waiex 191 185 lbs ballast.png (76.75 KiB) Viewed 2766 times

What I'd like to do next is figure how to safely move some weight from behind me to in front of me while flying. Then I can do my thing at aft CG, move it forward, and land.

[Bryan Cotton]

So here's another CG question - how am I going to get to the forward CG limit without losing 100 lbs? Do I find a rental forward CG Sonex test pilot? Do I somehow bolt lead to the engine? I suspect the Waiex is worse than the Sonex in this regard, in that my empty CG is biased aft. Makes for nice light pitch forces though. It doesn't seem too bad as I can be at zero fuel with 400 pounds of people (no baggage) and be 0.3" forward of the aft limit. Also single place I'm still easily in the acrobatic weight/CG range between 0 and 11 gallons while wearing a chute.

[Bryan Cotton]

Here is my moveable ballast concept. I borrowed and tweaked Area51's idea. I made a ballast box with some straps (including my shoulder harnesses) running through it.

Here is 16 lbs of ballast (1 gallon water jugs) in the ballast box.

I can move the 16 lbs forward 31". In the forward position the ropes are snug so they can't get forward into the pedals, or really go anywhere.

Here is a practice run of moving the ballast.


I may add one more strap held on by a carabiner clip to hold the jugs in the ballast box. Would be something to keep them from flying up if I did any negative Gs in a stall recovery.

So I'm going to figure out how much fuel to put me a little forward of aft CG. Needs to be enough to climb to a safe altitude, burn down to aft CG, do a couple of maneuvers and stalls, and then move the ballast forward. Then I'll land and be done with aft CG.

[BRS]

I know a float plane pilot who does a similar thing. In order to quickly get the floats up-on-step he would weigh down a duffle bag and tie a rope to it. The bag would start off in the full aft of the cabin until the plane was up on the step then the passenger would pull the rope to get the bag up forward and put the CG back in range.

[Bryan Cotton]

Right now I'm at 6 gallons. With my water ballast aft, I'll be at the limit at 5.5 gallons. Too windy to fly today but I'll taxi to the pump and put in 2.5 gallons, so I have fuel to taxi and climb up to a safe altitude. Moving the water jugs brings my CG forward 0.4", so puts it within the safe range quite easily.

[Bryan Cotton]

I took off near freezing, and at 1131 lbs. In the cold the Aerovee had no problem hoisting me aloft and climb was good. Burned off some fuel, and did stalls at 1116 lbs and the aft CG limit, 69.3". I'm going to call the aft CG test done. The moveable water ballast worked well.

[Bryan Cotton]

I ballasted so that at full fuel I was at 1100 lbs. Then I set off to do my service ceiling test. I got to 9024', but I'm going to call the service ceiling 8500'. I wonder if that is why Sonex advertises the max true airspeed at 8000'.

I had to pause around 7500' at a lower power setting and a higher airspeed because my oil climbed to 246F. Got it to 230 and it pretty much stayed there for the rest of the climb.

Do you other Aerovee guys do any better? I'm only at 20.3 hours of flight time.