I've not spun mine. I suppose an inverted spin would also satisfy the spin endorsement?

Others here probably know more about this than I do, but based on what I have been taught; No.

The airplane is limited legally to its certification. In Standard category, aerobatic maneuvers, including spins, are prohibited. Says so right on the sticker. To do spins in a 172 you have to load it so that it is in Cessna's certified Utility category.

You are screwed by the lazy (cheap?) certification that the airplane underwent long ago. The only way I know of to legally remedy that is to get it recertified in a category that allows spins and other aerobatic maneuvers. Given that the USN didn't elect to do that I suspect it's a bit out of the average owner's means to do so.

I suspect you're entirely correct John. I was hoping perhaps someone with more specific knowledge of this airplane that is clearly capable of spins and basic aerobatics could point out a path or work around. It seems if one could get it changed to experimental/exhibition that could work but I believe that would require some sort of written test plan submitted to the FAA and would be temporary in nature.

Again I'm speaking outside my area of expertise, but my understanding is that Experimental/Exhibition catagory is a permanent certification. You can convert to or from Normal or Utility to Experimental and leave it that way as long as you choose. It's the conversion to Acrobatic category from Normal, on an airplane that has never been certified as Acrobatic that is the problem. I am guessing that the path would be to first certify it as Experimental and then put it through the gamut of proving tests necessary to satisfy the FAA that it can be certified as Acrobatic. As a bonus, that probably would allow the change of all N3Ns, but again, it's not a process for the faint of heart.

This might be interesting if you could get a copy.

Spin tests of 1/16-scale models of the N3N-3 landplane and seaplane, 12 January 1940
The test program included the study of both the seaplane and landplane types. On both versions of the model, the effects of loading changes and control dispositions were examined, and on the seaplane, the effect of the cowled and uncowled engine was investigated.
Document ID
19770022119
Acquisition Source
Legacy CDMS
Document Type
Other - Other
Authors
Donlan, C. J.
(NASA Langley Research Center Hampton, VA, United States)
Date Acquired
August 8, 2013
Publication Date
January 1, 1976
Publication Information
Publication: Collected Works of Charles J. Donlan
Subject Category
Aircraft Design, Testing And Performance
Accession Number
77N29063
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

Charlie,

That's a good lead. I did the request and got the document along with Mr. Donlans other research including that of the XS-1. It's an interesting read but don't think it helps with the legal side of things. It does make me feel comfortable that the -3 version would be capable and safe for spins, normal or inverted. I've tried to load the file but it's too large. Happy to share if anyone wants a copy.

I'll add my N3N Story. About 12 years ago a big guy walked into the shop and wanted some tailwheel time. He was a student in the 152 at a local airport and so I crammed him into the J-3 and we flew a couple hours.

A couple years later I got a call. He said " I bought an airplane that will fit me!" Now this is a guy who had soloed the 152 but still a student. He was a go getter though and worked for the local power company. He worked every overtime he could and after big storms. Managed to buy a farm and build a shop etc. No debt.

So I was curious and he wouldn't say what it was just that he got an Airplane and I needed to come if I could give dual. He had gone for a ride with the seller when they delivered it.
I walked in the hangar and there was a R-1340 powered N3N with a T-6 cowl on it. Ooof.
"Can you give me dual?" I said I have no idea if I can fly it... Ok well let's see what it does. So after looking it over I taxied a bit. No grass at this county airport but 4700 ft paved.
It seemed reasonably close to the Stearman so ok what the hell. I took off and of course light with 600hp the rate of climb was pretty impressive. Roll rate was decent and it was very similar to the 300hp Stearman I had flown a few years earlier. Normal stalls etc. Power off 180 was spectacular from downwind but if you kept the prop back at cruise not too bad. I did not like the low MP needed to begin to descend in the pattern and reverse loading the crank was my concern.
The cockpit felt a bit shallower with the side walls and the side exhaust just belched out heat and fire depending on the power setting. I did not like the military stick grip someone had installed and prefer the Stearman style baseball bat. Military grip cants you hand forward too much.
Landing was ok and directional control was ok. So we started in with dual.
We flew to another spot with wide grass runway first and then worked back to the pavement from there. I finally said one day "You know I don't mind not seeing the runway but the whole airport is gone. Lets remove the cowl and baffles to fly it duster style. (It's in Experimental CAT). So we took a large amount of weight off the nose and then with the smaller diameter and visibility between the cylinders it was much better. A little MORE drag helped also.

By keeping the prop back and reduced MP takeoffs we didn't annoy the neighbors and could practice with it a bit tamer until he was confident to work up to full power.

He figured it out over the summer. And I finally soloed him on pavement end of summer. He did fine and built up more time. Then he built a short one way strip at his house with a big drop off on the approach end but it was a big enough radius you could land on the upslope. I was the first to land there with the N3N solo and then we worked into dual landings.

Later he got his private in the 152. He still has the N3N. It's just his airplane. Need to go to breakfast. N3N. Go somewhere to pick something up. Take the N3N. I said you have the best bragging rights in a bar if someone goes around asking what you're flying. 1940 600 Horsepower Navy Biplane is hard to top.... I heard he bought a J-3 Cub project for something more economical

I looped it a few times and some mild wingovers etc. I never felt like pushing it to spin it. Especially with the polar moments of big engine, big prop, rear oil tank etc. Looping it felt like I was sitting on my back porch looping my house but it went around from cruise just fine. Pavement 3 point, wheel landings, touch and goes were all fine.

The TCDS with 600hp info and gross weights is interesting. The brace wires are odd compared to the Stearman. They appear larger where the Stearman is smaller and smaller where the Stearman is larger but I never had them both side by side to compare. Odd. Single piece top wing is cumbersome if removed. Aluminum angle construction appears hell for stout and I wonder why it's not done more that way for light airplane design instead of tubing. Crashworthiness comparison? Manufacturing costs instead of welding would be fun to compare.

The gear with the cross brace wire was a different approach. It never gave trouble. What appeared to be T6 wheels and brakes worked fine. Tailwheel was fine.

Ground handling with the N3N seemed better than the Stearman. The N3N fuselage tank kept the weight lower and you did not get the top heavy feeling as much.

Wow. That one is a hoss.

I had heard that the Navy quit on the N3N due to it being an aluminum plane and AL was a war critical material.........the Stearman used less AL so it was adopted by the Navy out of necessity.

Another part of the story is that the N3N originally took advantage of a stock of Aluminum left over at Lakehurst due to the dirigible program cancellation.

The N3Ns served into the 50s at the Naval Academy where they were operated on floats and provided aviation training for the middies. They were based in hangars across the Severn River from the Academy. The hangars and some of the ramps still are there.