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Aft C of G

The down load on the tail is lower. Thus the total weight which the wing needs to support is lower. Since the wing is carrying less weight it will have a lower stall speed.
 
Before we quit - Do you think an ordinary Citabria can go flat in a spin?
Bob,
Why did you ask this question? Did you have an incident? Curious minds, as I'm into wondering why something happens if for no other reason than to prevent a reoccurence. Flat spins could be nonrecoverable especially if the fuel in the tanks moves away from the outlets and the noise maker goes quiet.
 
No - I rarely do more than 3/4 of a spin.

But I have heard stories of folks who like to count the turns - I understand the impulse to make/break records (yesterday I did 42 Stearman landings) - but my impression is that after two or three turns a spin will tighten up.

We had a Citabria fatality last month - extremely experienced instructor; object of the lesson was CFI spin certification. I have heard almost nothing - one pilot suggested a low level engine failure and an unsuccessful landing - but I initially wondered if it hadn't spun in?

I own a Decathlon - not quite the same. I am not wild about multiple turn spins, so will be doing no exploratory testing. Just wondering if these fine airplanes can go flat? Pretty sure a Cub can get into a difficult-to-recover spin with a heavy guy in the back. Not gonna try that either.
 
Apologies to Colin for the thread drift however I don't believe that you will mind.

The airplane in which I had the flat spin episode normally spins with the nose nearly or sometimes, beyond vertical. This one time the nose went down to the normal position, wobbled a bit and rose to level. The plane was absolutely level in pitch and bank. One wing was going forward and the other back. All of the controls had no feedback whatsoever. The same as though it was parked in the hangar while checking the controls. It made seven turns loosing 700 feet. The only control which had any effect towards recovery was the throttle blasting the tail pushing the nose down to break the stall. Why did it do this? That is a big mystery which I was unable to duplicate. With this experience I feel that any airplane could get into a flat spin. If you are into a normal spin and the nose starts up on it's own, stop the spin immediately.

My Cub will only spin if I load it to the aft CG limit. Steep spiral yes, but spin no. I found no unusual spin characteristics in the Cub. That doesn't mean that something unusual will not happen. I've also done extensive spins in the 185 on amphib floats with no unusual characteristics found.
 
A lot of people get carried away with spins. First of all, if you are spinning a normal category airplane, all bets are off. If you are spinning in the utility category, read the AFM or TDCS and placards very carefully as the envelope is narrower than you may think. If you are in an aerobatic airplane and you exceed 6 turns, unless greater than 6 turns is the certification basis, you are a test pilot. FAR23-2150
 
Don't misunderstand me, all three of those planes were or are licensed Experimental-Research & development or Amateur built. The spins were accomplished completely in accordance with the FARs and in some cases were accompanied by an FAA test pilot.
 
None intended, I was just reviewing what the pilot of a certified aircraft, even one certified aerobatic should know before getting carried away. I was talking to a pilot of a well known certified aerobatic aircraft a while back, a real spin freak and he was stunned to know he was operating the aircraft outside of the certification parameters.

In your case you really were a test pilot. Suffice to say that one incident would require investigation and remediation if one was going for a certification. The stall stability rules have to be exhibited every time, all the time.
 
I own a Decathlon - not quite the same. I am not wild about multiple turn spins, so will be doing no exploratory testing. Just wondering if these fine airplanes can go flat?
Bob, I've spun a 150 Decathlon many turns, many times and often with an adult male in the rear. By 3 turns it's as wound up as it's going to get, and I've never had it try to flatten out. Because of the way I was taught, I always recovered with positive/assertive control inputs, but I think if you just let go of a Decathlon it'd fly itself out of a spin. I don't know how the airspeed would stack up, but I think it would stop rotating and start flying on it's own fairly quickly.
 
No - I rarely do more than 3/4 of a spin.

But I have heard stories of folks who like to count the turns - I understand the impulse to make/break records (yesterday I did 42 Stearman landings) - but my impression is that after two or three turns a spin will tighten up.

We had a Citabria fatality last month - extremely experienced instructor; object of the lesson was CFI spin certification. I have heard almost nothing - one pilot suggested a low level engine failure and an unsuccessful landing - but I initially wondered if it hadn't spun in?

I own a Decathlon - not quite the same. I am not wild about multiple turn spins, so will be doing no exploratory testing. Just wondering if these fine airplanes can go flat? Pretty sure a Cub can get into a difficult-to-recover spin with a heavy guy in the back. Not gonna try that either.

Bob,

I was advised by a guy who would know as I was becoming familiar with aerobatics to remember one thing about spins: Any airplane MAY become unrecoverable in a spin. As Pete noted, pay careful attention to the pitch attitude. If it starts to go flat, recover immediately. Unless you’re flying an aircraft certificated for flat spins.

Spins deserve a great deal of respect. Pilots often fail to exhibit that level of respect, and sometimes pay a heavy price.

MTV
 
Thanks for that - my feelings were gut instinct, and now they have at least some basis. I also got some input via PM.

Ten turn spins are not necessary or productive, and may not be safe.
 
I’m going to resurrect this thread regarding “excess stability.” The comments about it don’t make sense in my planes (plural) so I asked a very close friend, a Professor of Aerospace Engineering at a large university about stability, controllability, maneuverability, etc. with respect to my own airplanes. My Rev is a good example to start with. On paper the CG sits comfortably within the CG envelope. Flown empty I describe it like trying to balance on ball bearings. This plane is not excessively stable. In its forward limit its anything but. Clearly what I perceive as stability improves with weight added aft. It could be argued that maneuverability is at its peak but in this example that isn’t a good thing. Controllability is more difficult to understand. The plane responds to pilot inputs but the pilot has to make constant corrections. What a design engineer and a pilot define as controllability may not represent the same thing. My Cessna’s tendencies are along the same lines although not as dramatic. The concept that airplane stability improves as CG moves forward until it becomes ”excessively stable” doesn’t prove up in my experiments. I’ve read several papers about it and talked to the smartest guy I know about it. All we can come up with is that the paper description and pilot description don’t reconcile, and that’s probably semantics.

I was in FSDO a couple of weeks ago talking to a couple of inspectors and mentioned that every flight in my Rev brings another adjustment, so every flight I’m a test pilot again. CG was a large part of the discussion. It’s an interesting process. They reminded me why STCs are time consuming and difficult to get. Certificated guys operate within limits that somebody else explored and defined. Experimental guys don’t have that luxury. I have a new perspective on the process.
 
pa11driver
I missed your post (#18) earlier. I used to load as you do most all the time. But now would have to to say "it depends". Times I tend to load tail heavy, going into a short/new strip that I need hard braking, or if I have long legs to fly hoping to increase my airspeed. I will try to load front heavy for taking off on rough stuff so I can get the tail up, or knowing I am going into rough air.

I enjoy threads like this that help explain some of the terms and theories.
DENNY
 
Stewartb
How much dihedral did you dial in?
DENNY

Standard Supercub, if memory serves. Jeez, that was two years ago but it clearly has typical Cub dihedral. This is a W&B issue. The Flight Standards guy was interested and helpful, but that was not what I was at FSDO for. Weight aft is a normal thing for most of us. This Phase 1 testing isn't my normal operational profile so the CG is not a problem as much as an opportunity to learn new things. And new respect for test pilots. :)
 
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Both PA-12's I flew had what I'd call neutral stability (https://www.boldmethod.com/learn-to...-of-static-and-dynamic-stability-in-aircraft/). If disturbed in flight they would take off on their own up/down/sideways. Took constant minor corrections to maintain desired flight. One I owned had an O-360 and CS prop and was forward CG...still went looking when it smelled something. Wheels, skis, floats didn't matter. Not bad just different than the others I owned or had experience in.

Rigging was about 0.75* dihedral for the one with extended wings and 1* with factory wings. 2.5* wash on both.

Gary
 
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