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  #1  
Old 01-03-2021, 09:16 AM
MacCool's Avatar
MacCool MacCool is offline
 
Join Date: Aug 2020
Location: central Minnesota
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Default RV-9 /9A aerobatics

I have no desire nor intent, but Iím curious as to what it is that makes the RV-9 and 9A limited to non-aerobatic flight. Is it the Roncz airfoil? Is it a handling/control issue, or a structural issue? Is the 9/9A somehow less robust than the 7/7A?
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  #2  
Old 01-03-2021, 10:51 AM
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Snowflake Snowflake is offline
 
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Default

Given the similarity of the fuselage to the -7, I would guess that the wing and tail structure were not designed to take the flight loads of aerobatic flight to the aerobatic standard limits.

That said, many people have looped and rolled their -9's. They just had a lot less safety margin that someone in a -7 would. When things go sideways, you want that margin.
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  #3  
Old 01-03-2021, 10:52 AM
PilotjohnS PilotjohnS is offline
 
Join Date: Jan 2016
Location: Southwest
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Default Yes

It is the strength of the wing. The 9a wings are longer span and narrower, giving better high altitude performance at the sacrifice of a lower maximum g load. The wing is slipper due to the higher aspect ratio. If you screw up the maneuver in a 9, you could pull the wings off.
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  #4  
Old 01-03-2021, 11:20 AM
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I thought I'd understood that the 7 and the 9 had the same fuselage and empennage, so that makes sense - wings not stressed for G loads associated with (incorrectly) performed aerobatics. I presume that it's not something I have to worry about in non-aerobatic flight as long as I pay attention to the maneuvering speed....?
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  #5  
Old 01-03-2021, 12:36 PM
PilotjohnS PilotjohnS is offline
 
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Location: Southwest
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Default Still 6 gs

If I am not mistaken the RV9 is still designed for 4.4 gs.(corrected, see below) I think I will be passed out before the plane comes apart, so I am not worried.
Most of our wonderful ex-military pilots can pull 9 gs all day long, they are the ones the 9 will complain about.
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WARNING! Information presented in this post is my opinion. All users of info have sole responsibility for determining accuracy or suitability for their use.

Dues paid 2021, worth every penny

RV9A- Status:
Tail 98% done
Wings 98% done
Fuselage Kit 98% done
Finishing Kit 35% canopy done for now
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Last edited by PilotjohnS : 01-03-2021 at 02:31 PM.
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  #6  
Old 01-03-2021, 01:17 PM
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N804RV N804RV is offline
 
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Quote:
Originally Posted by PilotjohnS View Post
If I am not mistaken the RV9 is still designed for 6gs. I think I will be passed out before the plane comes apart, so I am not worried.
Most of our wonderful ex-military pilots can pull 9 gs all day long, they are the ones the 9 will complain about.
Are you sure? I thought it was utility category up to 1600lbs. That's +4.4G/-1.75.

Besides, anyone who skis a pair of downhill mogul churning skis , and then slips on longer, skinny skis for cross-country understands what a difference that longer wing will make.

Its not about doing it right. Its that one time you don't that'll get you.
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  #7  
Old 01-03-2021, 01:21 PM
terrye terrye is offline
 
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Default RV-9 /9A aerobatics

Quote:
Originally Posted by PilotjohnS View Post
If I am not mistaken the RV9 is still designed for 6gs. I think I will be passed out before the plane comes apart, so I am not worried.
Most of our wonderful ex-military pilots can pull 9 gs all day long, they are the ones the 9 will complain about.
RV-9(A) are stressed to utility category +4.4/-1.76 G at solo weight and normal category +3.8/-1/52 G at gross weight. The aerobatic aircraft -3,-4-,-6,-7,-8 are stressed to aerobatic category +6/-3 G (but not sure at what weight). Very dangerous to assume a higher limit load factor than the designer used.
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  #8  
Old 01-03-2021, 01:55 PM
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AlexPeterson AlexPeterson is offline
 
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Default

Quote:
Originally Posted by PilotjohnS View Post
SNIP I think I will be passed out before the plane comes apart, so I am not worried. SNIP.
This is not true. You would still be awake to see the wings break. The airplane does not care how short the duration of the g-event is, while your body does. The sticks in all RV's are very capable wing-removal levers. Pull the stick too fast and too much, and you're toast.
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  #9  
Old 01-03-2021, 02:20 PM
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bruceh bruceh is offline
 
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Default

Quote:
Originally Posted by MacCool View Post
I thought I'd understood that the 7 and the 9 had the same fuselage and empennage...
There are differences in the Horizontal Stabilizer and Elevators. The 9 has a rectangular shape, and the 7 has a swept leading edge. Fuselages are 99% the same, save for the forward attachment of the wing due to the different shapes.
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  #10  
Old 01-03-2021, 03:25 PM
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grubbat grubbat is offline
 
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Default Guess

If I were to guess, I suspect the high aspect ratio wing performs less optimal pulling Gíg than the other standard Vans wings. I also suspect the longer span, and the longer horizontal are less tolerant to g loading than the other van designs. Sure, you can perform whatever acrobatic you prefer, however, you didnít purchase enough margins in this design to be able to do multiple aerobatic maneuvers such as tail slides and live to tell about it. As a matter of fact, some of the other designs donít have enough margins for tail slides so I guess every design has its aerobatic limitations. A good aerobatic pilot such as Bob Hoover could do a lot of non stressful aerobatic maneuvers in any plane so it really comes down to skill and acceptable risk.

Quote:
Originally Posted by MacCool View Post
I have no desire nor intent, but Iím curious as to what it is that makes the RV-9 and 9A limited to non-aerobatic flight. Is it the Roncz airfoil? Is it a handling/control issue, or a structural issue? Is the 9/9A somehow less robust than the 7/7A?
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