Spinning an RV-10

[jrs14855]

A few facts about certified aircraft: spin testing the Cirrus was apparently waived because of the chute.
There is NO spin testing requirement for US certified light twin engine aircraft.
AC23.8A Twin engine airplanes can not display an "undue tendency" to spin from an unaccelerated, wings level stall with the critical engine failed.

Cessna took the Skycatcher far beyond the testing requrements fo LSA , and as a result lost two aircraft before getting things sorted out.

My main point in this is that someone posted about spin testing airliners. I don't believe that any modern US airliner has been spin tested. I do know of alleged cases where the Lockheed Electra(4 engine turboprop) and the Boeing 707 were inadvertently spun.

[Ron Lee]

I do not recall every prior post but if this test was at the aft CG limit, was it loaded that way or is the basic CG such that it could be loaded to a point AFT of the aft CG limit with people in the back seat and/or lots of luggage?

[B25Flyer]

Originally Posted by Ron Lee

I have never seen anything until this thread that suggests that some mythical "polar moment" impacts how a plane recovers from an unusual attitude. NEVER.

Aft CG...yes. Now if it is factual that there is a real aerodynamic difference in how you get to a specific CG, then we all need to change our POH and training needs to be changed as well.

Voodoo physics doesn't cut it.

While we are at it...perhaps angular momentum is the term you should be using.

Ron,

The Laymans term for polar moment is the dumb-bell effect.. It is real, not voodoo science and concentrating weight at the ends of an airplane has a dramatic effect on spin recovery... Tip tanks being an extreme example of dumb-bell effect. if you have fuel in the tip tanks of an airplane on the C.G the amount of fuel would have no effect on CG, but a drastic effect on spin behavior and recovery...

There is so much more to aviation than the rote level learning we acquired as private, commercial, or ATP, students... The total volume of what is unknown in the universe so far exceeds the volume of what is known, and aviation is no exception. Much of the stuff that us left brainers hold to be gospel fact, is actually the best guess of some guy who came up with a simple way to make us left brain pilot learners understand a concept.... The real truth of it is that much of our understanding of aerodynamics is still a hypothesis... However, polar moment, or dumb-bell effect is not a hypothesis, it is well understood and well documented in the literature... But, not in the private, commercial, or ATP, PTS.

Once we realize how much we don't know and understand, we can open our mind to the reality of how much we have to learn about the art of aviation.... Yes there is science in it, but at the end of the day, like medicine, it is an art. and those who do it well, are in a practice.... Those who believe they have it all figured out are missing most of it....

Doug Rozendaal
Practitioner..

[gtmule]

Originally Posted by Phil

I can't believe what I'm reading. Who would have ever thought it was so easy to disprove the fundamentals of physics learned in a 101 level course.

I don't need wreckage to prove polar moment exist. (Which you could never prove with wreckage either)

And I don't need wreckage to tell me that the further away from center mass you move a mass of weight, the more pronounced it becomes.

This is simple stuff. I never realized how easy it would be to simply ignore the basics as being something insignificant.

Unbelievable.

You obviously didn't see the torque wrench thread....

[RVZoomie]

I can vouch for polar moment, its introduced in any Dynamic Stability and Control class and is a player in equations of motion. It can be considered about any of the three axis not just the longitudinal. It came up in the tanker as someone claimed to have recovered at 180 deg of bank. I suggested if they really knew their stuff they would've continued the roll and recovered faster considering the time and effort to dissipate and reverse the angular momentum they had created.

[aerhed]

I remember my first polar moment. New years day 93. Pulled into KPNA as a full-time resident, stepped out of my 72 Bago into -27 degrees. I blinked and my contact lenses froze and fell on the ground.

[RVbySDI]

Originally Posted by aerhed

I remember my first polar moment. New years day 93. Pulled into KPNA as a full-time resident, stepped out of my 72 Bago into -27 degrees. I blinked and my contact lenses froze and fell on the ground.

I don't care who you are: THAT THERE IS FUNNY!!!

[TSwezey]

Originally Posted by RVZoomie

I can vouch for polar moment, its introduced in any Dynamic Stability and Control class and is a player in equations of motion. It can be considered about any of the three axis not just the longitudinal. It came up in the tanker as someone claimed to have recovered at 180 deg of bank. I suggested if they really knew their stuff they would've continued the roll and recovered faster considering the time and effort to dissipate and reverse the angular momentum they had created.

Is that like somebody doing a 360 to turn around and go in the opposite direction?

[N427EF]

Todd,
I thought you needed to do a 380 for that

[David-aviator]

Originally Posted by B25Flyer

Ron,

The Laymans term for polar moment is the dumb-bell effect.. It is real, not voodoo science and concentrating weight at the ends of an airplane has a dramatic effect on spin recovery... Tip tanks being an extreme example of dumb-bell effect. if you have fuel in the tip tanks of an airplane on the C.G the amount of fuel would have no effect on CG, but a drastic effect on spin behavior and recovery...

There is so much more to aviation than the rote level learning we acquired as private, commercial, or ATP, students... The total volume of what is unknown in the universe so far exceeds the volume of what is known, and aviation is no exception. Much of the stuff that us left brainers hold to be gospel fact, is actually the best guess of some guy who came up with a simple way to make us left brain pilot learners understand a concept.... The real truth of it is that much of our understanding of aerodynamics is still a hypothesis... However, polar moment, or dumb-bell effect is not a hypothesis, it is well understood and well documented in the literature... But, not in the private, commercial, or ATP, PTS.

Once we realize how much we don't know and understand, we can open our mind to the reality of how much we have to learn about the art of aviation.... Yes there is science in it, but at the end of the day, like medicine, it is an art. and those who do it well, are in a practice.... Those who believe they have it all figured out are missing most of it....

Doug Rozendaal
Practitioner..

Excellent post, Doug. I couldn't agree with you more.

I've been at this longer than I care to admit and still feel like a student in some respects. I guess that's what keeps it interesting.