"Flat spin" within approved envelope?
 

As long as the CG is within the envelope, does that mean that spins are always recoverable?

I ask because I'm curious to know at what aft CG point does a spin in a 172 become unrecoverable. If its outside the envelope, no problem. Inside, well then that's something to think about!

Thank you!

If it is spin certified then yes, it is safe as long as you load it properly. Because spin testing is time consuming, expensive, hazardous, and unnecessary for most applications you generally do not get "spin approved" unless the airplane is likely to see spins in typical use. Trainers and aerobatics generally do, with exceptions (twins), but not much else.

Thank you, Cub!

I have heard of stalls gone wrong resulting in spins in which both pilots had to get out of their seats and lean all the way forward over the dash to move the CG far enough forward.

I also know that a CG only a fraction of an inch out can create an unrecoverable situation in some cases. I would not only not push the envelope, I would give myself a safety margin. Seriously...less than one inch can kill you.

Skyhawks are only spin approved when loaded in the utility category as you already know, and there is not much slack there. I take the junk out of the baggage area and leave my flight bag at the hangar when doing spins. An additional problem you run into with vintage Skyhawks is the seats coming loose at high deck angles & rudder kicks.

The newer Skyhawks do not have that problem (loose seats), but they have an even narrower utility category. I used to work at Cessna and I was told this is because the airplane has had a lot of changes, things like sound proofing and G1000. The 172S POH shows utility loading ends at 40.5 inches aft of datum, normal extends to 47.5. That's a big delta in an aircraft of this size. There really can't be anything behind the pilots and fuel needs to be reduced. I used to take the rear seats out of the back of the 172SPs as an additional precaution. That was a pain and added a half hour of fooling with seats to a lesson, so we did not do a lot of spins.

I seem to remember something about "3 turns", as if the aircraft was only certified/demonstrated to recover from spins of 3 turns, no more. That could be a problem if true. From personal experience, some of them are very "spin resistant", and some with just the right CG and conditions/loading can be a wild ride, although none enter "easily". If you ever do this from a stall something is extremely wrong, I had one time I thought my student's actions were actually starting a spin during one, so I slammed the yoke forward to decrease the AOA, way more important than slamming the rudder.

Years ago my uncle went along to do spins with his friend who just bought a Luscombe. After several rounds of 2 and 3 turn spins, they tried a 4 turn spin, but it went flat. They couldn't get the nose down, but my Uncle's friend was thinking fast enough to open the door to get as much of his body weight as forward as possible. The change in airflow and CG was enough to recover.

It took a while to discover the cause, but apparently the plane was painted many times by the previous owner and the previous owner never took off the old paint or got a new weight and balance.

Holy crap! That's incredible.

For the seasoned CFIs out there, would you recommend always loading the plane to utility category when doing any air work?

My concern is that while practicing stalls with a student, we could enter a spin in a normal category loaded aircraft which could prevent a recovery.

Thoughts??

I wouldn't worry about that. If a student turns a normal stall into a spin, you should be able to recognize and recover before the spin fully develops. If you haven't yet, go up and do a bunch of spins to the point where you get bored. At first a spin seems to develop very quickly, but as you get used to it you will realize there is a good amount of time from when a stall goes bad to when it becomes a spin.

I only had one serious scare with a student doing stalls. We were in a light sport aircraft that is certainly not spin worthy and extremely unstable around the vertical axis. By that point I had done so many power on stalls in that airplane with that student that I was a little too relaxed. I saw that he forgot to add the rudder as he added power and pulled up, but wanted to teach him a lesson by letting him experience a wing drop, which is violent in this plane. He ended up pulling back quickly and despite it being 2 years since my last spin I still remembered the feeling. I went from being bored, to being in denial that we were going to spin, then to acceptance of the fact that we were going to spin, and then finally a remembered that I was in the one aircraft I really didn’t want to spin! Despite all of that, I had enough time to push the nose down and give opposite rudder before we entered a fully developed spin.

Here's a dumb one for you. Twenty seven years ago, this bored CFI took up a Tomahawk with another bored CFI. We wanted to practice a spin in it. We had never done a spin in this type of plane though but it's a plane, right? Good thing we started high. Couldn't get out of the spin. Opposite rudder, full nose down. Nothing!!!

Providence we recovered after, I don't know how many turns, and just some 900 feet above the ground.

We discovered the placard "no spins approved" over our heads afterwards. Stupid! Stupid! Stupid!