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Rolling G Limits

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shinden33

Joined: 02 Nov 2007
Posts: 39

Posted: Wed Aug 06, 2008 9:05 am Post subject: Rolling G Limits

All, 



Has anyone heard mention of asymmetric or rolling g limits on civilian aircraft.  I've seen them with military aircraft but I have never heard mention of rolling g limitations for civilian aircraft until today.   What's really disturbing is that FAR 23.349 states that structural requirements for certification only require that the airplane be built for rolling loads at 2/3 of symmetric G limit.  http://rgl.faa.gov/REGULATORY_AND_GUIDANCE_LIBRARY/RGFAR.NSF/0/E6FD59161E5CCA9685256687006D10A2?OpenDocument

From the look of this reg, US airplanes may have implied limit?  Anyone have any experience with rolling g limits on civil aircraft?  More importantly for this crew, does anyone have any gouge on rolling g limits for Yaks and CJs?



Scott

N8252

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dsavarese0812(at)bellsout
Guest

Posted: Wed Aug 06, 2008 9:31 am Post subject: Rolling G Limits

Scott,

I am not aware of any published rolling G limitations for the Yak 52.  That 

doesn't mean that somewhere in the archives of this airplane's engineering 

documentation there isn't one.  I just have never seen one.

Dennis



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Joe Enzminger

Joined: 06 Feb 2006
Posts: 26

Posted: Wed Aug 06, 2008 3:53 pm Post subject: Re: Rolling G Limits

I don't think you'll find published limits in your approved flight manual, but the fact of the matter is there is a limit.  In other words, if you pull to your limit load factor and then add full aileron, something is going to bend or break, no doubt about it and no way to design around it.



The 2/3 limit is a good rule of thumb with a safety factor built in, but if it's not a U.S. Certificated airplane, there's no guarantee it'll work out.  I could go into all the other issues (like decreased fatigue life, etc.) that come into play with "Rolling G's", but the fact of the matter is it's better to "unload, roll, load".



Incidentally, this doesn't apply to snap rolls.  While I wouldn't do it (simply because it's hard to be this precise), you can snap at the limit load factor without concern for the effects of rolling G's.  The maximum (not recommended) snap speed is usually the speed at which the airplane will stall at the limit load factor. 



Joe

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wlannon(at)persona.ca
Guest

Posted: Wed Aug 06, 2008 4:22 pm Post subject: Rolling G Limits

Turning/rolling  positive "G" limit for the CJ6 is 3.6.

This is information received by Joe Howse some years ago from  Mr. Yiji Guo, 

Senior Engineer, Beijing Aeronautical Technology Research Centre.

It has been published on the Yak List numerous times over the past years by 

Joe and myself.



3.6 G represents 60% of the normal 6G limit for symmetrical loading and is, 

as far as I know, an industry standard to avoid the possibility of exceeding 

the normal limit with unequal loading..

I have no information for the Yak 52 but expect a similar standard would 

exist for that.



Walt



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petervs(at)knology.net
Guest

Posted: Wed Aug 06, 2008 6:50 pm Post subject: Rolling G Limits

When I was taking aerobatics instruction in the Yak from Sergie I 

asked him the best way to break a Yak. His reply was to do snap rolls 

without fully stalling the wings. So I guess that means that if you 

don't fully stall the wing before the snap roll you will be inducing 

rolling g's.



Pete

At 06:53 PM 8/6/2008, you wrote:

 	  Quote: 	
		  



I don't think you'll find published limits in your approved flight 

manual, but the fact of the matter is there is a limit.  In other 

words, if you pull to your limit load factor and then add full 

aileron, something is going to bend or break, no doubt about it and 

no way to design around it.



The 2/3 limit is a good rule of thumb with a safety factor built in, 

but if it's not a U.S. Certificated airplane, there's no guarantee 

it'll work out.  I could go into all the other issues (like 

decreased fatigue life, etc.) that come into play with "Rolling 

G's", but the fact of the matter is it's better to "unload, roll, load".



Incidentally, this doesn't apply to snap rolls.  While I wouldn't do 

it (simply because it's hard to be this precise), you can snap at 

the limit load factor without concern for the effects of rolling 

G's.  The maximum (not recommended) snap speed is usually the speed 

at which the airplane will stall at the limit load factor.



Joe





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