RV-9 /9A aerobatics

MacCool · #1 01-03-2021, 09:16 AM

I have no desire nor intent, but I’m 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?

Snowflake · #2 01-03-2021, 10:51 AM

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.

PilotjohnS · #3 01-03-2021, 10:52 AM

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.

MacCool · #4 01-03-2021, 11:20 AM

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....?

PilotjohnS · #5 01-03-2021, 12:36 PM

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.

N804RV · #6 01-03-2021, 01:17 PM

Quote:

Originally Posted by PilotjohnS

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.

terrye · #7 01-03-2021, 01:21 PM

Quote:

Originally Posted by PilotjohnS

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.

AlexPeterson · #8 01-03-2021, 01:55 PM

Quote:

Originally Posted by PilotjohnS

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.

bruceh · #9 01-03-2021, 02:20 PM

Quote:

Originally Posted by MacCool

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.

grubbat · #10 01-03-2021, 03:25 PM

If I were to guess, I suspect the high aspect ratio wing performs less optimal pulling G’g 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 didn’t 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 don’t 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

I have no desire nor intent, but I’m 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?