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Andy A

Rolls in a CT?

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Just curious, are rolls allowed in a CTLS?  Sure would be fun if they were.

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Almost any airplane can be rolled, but few can be rolled legally. Normal and utility category airplanes are not permitted to exceed a bank angle of 60 degrees. Only acrobatic category airplanes may be rolled, and then only when the occupants are equipped with parachutes. Nevertheless, the enforceability of such regulations at several thousand feet and in remote places being somewhat problematic, a good many Cessnas, Cherokees, Cirruses and their ilk have, in fact, been rolled-or so I would surmise, never having seen it done myself.

https://www.flyingmag.com/safety/accident-investigations/its-possible-roll-airplane

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I joke that if I ever designed a plane, it would never get off the ground due to the metal and redundant bolts I'd put into it.  Our CT aircraft  demonstrate  that those who designed our planes had an excellent knowledge about designing light weight composite structure.  I think the stabilator, in particular, demonstrates a minimal composite structure design that seems to be safe.  I'm curious though, are there any reported failures of this area?  There have been instances where cracked stabilator brackets have been found but I'm wondering about the design overall?

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My memory is fuzzy but I'm guessing something like an Italian air show catastrophic failure involving the tail.?

My mind goes to failure at that point, lately I'm using big deflections resulting in g's but I apply it smoothly and don't think it adds up to a lot of force applied to the stab much like I can push the tail down on the ground to pivot pushing with a fingertip.

Wind shear however, I've had one big slam and expect this could be a cause of failure if said big slam stressed the stab.

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When you look at lubrication oil system of the Rotax as it is installed on the CTs and at that little tank hanging a few inches away from engine, you would think that oil has to be constantly in the bottom of the tank in order to be pumped into the engine properly. So if you roll, unless you keep the Gs on absolute positive value, the oil would tend to leave the bottom of the tank and the engine would pump air instead of oil. Sould this happen, not sure if it is so easy to bring lubrication oil back in the circuit.

Standard carburator system seems to be based on gravity too (not talking about electronic injection).

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2 hours ago, CT2K said:

So if you roll, unless you keep the Gs on absolute positive value,

I do experience negative Gs from time to time.  Rotax doesn't know its doing a roll on that its negative.

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My point is when lubrication oil little tank is upside down and engine ends up pumping air instead of circulating that oil, that must not be something good

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A properly executed aileron roll is a 1g maneuver.  The key phrase being "properly executed."

CT, do you really get negative g's occasionally, or do you mean "less than 1g"?  My experience is that true negative g's are hard to get into, and you have to actually try to do it.  The most I ever hit in my CT was -0.2g, I was actually trying to do it, and it was pretty uncomfortable and some pens and stuff started floating around the cockpit.  It's pretty hard to go beyond 0g in the negative in normal, or even aggressive maneuvering.  

BTW, Rotax has a -0.5g limit on the 912 series engines, you are not supposed to exceed that in the negative.  I'm presuming that's due to the oiling system, as CT2K alluded to.

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8 hours ago, FlyingMonkey said:

CT, do you really get negative g's occasionally, or do you mean "less than 1g"? 

Yes I do but as you point out its far more common to see less than 1 than it is to see negative.    The more dramatic canyon exits for instance can be negative.

 

 

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