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RV9 Aerobatic Conversion

Plumbmaster

Active Member
What are the plus and minus G tolerances for the RV nine? Is the -9 even slightly aerobatic? If not, can the 9B converted i.e. by shortening the wingspan to be able to be safe for aerobatics?
My reason for asking is that there are a significant number of -9’s available for sale and the flying season is coming up.
 

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RV-9 Aerobatics

Don't go there please. In the hands of a skilled demo pilot maybe. But not in mere mortal experience levels.

Buy or build the plane that meets your needs.
 
RV9 Spar

Without the benefit of talking to Van's, a previous forum on this subject contained information relating to the spar length of the -9. Apparently, the spar is different on the -9...
 
-9 To -7 Conversion

Unfortunately, I converted my -6A to cash in July and then the market "took off" (pun intended). The problem is not the lack of funds, it's the lack of 6's and 7's for sale. I always felt the taildraggers were a sexier bunch and want to be able to land at "unimproved" air strips. Here patience is the key obviously.
Buku -9's for sale, not so much with the others
 
Ron,
In post #1 you wanted aerobatic capability. In post #6 you wanted unimproved airstrip capability. The 9 (or 9A) would be better for unimproved airstrips due to slower approach speed than a 6 or 7.

Fin 9A
 
Fin,

Having flown the -6A considerably, I would be comfortable flying a -6, -7 and -8 in to a grass or gravel (ouch) strip. The Vans nose wheel configuration, especially on my 1995 model did not inspire confidence even with an anti splat mod. When I sold my plane in July I was betting that the economy was going to go in the crapper and planes would become less expensive. Quite the opposite has happened! Additionally you “Niners” have my respect, great cross country airplanes and indeed good to land on grass fields!
 
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The long answer is, "NO".

Our 9A has treated us well for way over 2000hrs, but aerobatic it is not. There are all kinds of missions, and most of us try to explore various things with not just one mission. The 9(A) is great for transporting to distant lands quickly and with happy loved ones. For other experiences, for me, maybe a super decathlon or an RV8...

I'll still pick the RV9A any day if it means a bikini on a beach!
 
If I understand it correctly (I may very well not), it's not just the wingspan that's the limiting factor, it's the airfoil itself. The -9 wing is optimized for more stable cross country type flight. It stalls 10 mph slower than -7. It's other speeds are similar, but the key point is that it was engineered for Utility class and not for aerobatics. I would think that if Van's thought that it was designed for aerobatics, they'd allow it and even promote it that way. This is a simple case of accepting the mission of the -9 and if you can't, change the mission or pick a different plane.

I'm a big fan of my -9A and I'm perfectly content keeping the blue side up. I hope you can find a plane to fit your mission without having to use "it should work" engineering.

BTW, the answer to your initial question, the RV-9 is rated for +4.4/-1.8G at Utility Gross Weight of 1,600 pounds. Here is an excerpt from the 9/9A construction manual - I suspect that the text is very similar to the other models. Emphases retained.

AEROBATICS

Note: The RV-9/9A is NOT designed or intended for aerobatics.

Note: Aerobatic maneuvers as defined by the FAR’s include bank angles greater than 60 degrees relative to the horizon and nose-up/nose-down pitch angles of 30 degrees relative to the horizon. These maneuvers must be performed above a minimum altitude of 1500 feet AGL and all participants in the aircraft must wear a parachute.

RV airframes are stressed for aerobatics up to a gross weight of 1050 lb.for the RV-3, 1375 lb for the RV-4/6/6A, and 1600 lb. for the RV-7/7A and the RV-8/8A with the “Dash One” wing (included in all RV-8/8A kits shipped since January, 2001.) Earlier RV-8/8As with the original wing have an aerobatic gross weight of 1550 lbs.

This means that they have design strengths of 6 positive and 3 negative Gs (plus a 50% safety factor) at up to this weight. The key word is WEIGHT. RV structures have a certain amount of strength and are capable of carrying a given load at given G load. If the weight increases, so does the stress. As the empty weight increases, the useful load decreases —less fuel and pilot/passenger load can be carried within the aerobatic weight limit. For this reason, a heavy 2-seat RV may become a single place aerobatic airplane because it cannot carry two people and remain under the aerobatic gross weight limit. We expect that the empty weights of many RV-4s and RV-6/As will be over 1050 lbs. because of optional equipment installed. These will definitely be single place aerobatic airplanes. Some RVs have been built with such high empty weights that when flown by a pilot weighing much over 200 lb., are no longer structurally qualified to perform aerobatics at all. Check the specific aerobatic gross weight given in Section 14. Always remember, RVs are not indestructible. Like all other airplanes, they have been designed with finite limits which must be observed. As a homebuilt, any individual airplane may have different limits which in all probability will be lower than design limits.
 
Great information Claude, indeed the 6A was flown as a single seater Aerobatic aircraft by myself. I have not been fortunate enough to transport a bikini babe to the beach (yet)!
 
You could probably clip the wings and do it, but you need to do all your own engineering design and analysis work. It would be truly experimental. I haven’t heard of anyone else that has done it since it seems easier to just get a 7.

Tim
 
You could probably clip the wings and do it...
Unfortunately not.

You're still looking at increasing the load and bending moment at the wing root to the aerobatic region... The spar carry-through needs to carry that additional load and it wasn't designed for it.
 
You could probably clip the wings and do it, but you need to do all your own engineering design and analysis work. It would be truly experimental. I haven’t heard of anyone else that has done it since it seems easier to just get a 7.

Tim

You would also have to completely analyze and address the tail - its a different design than on the other side-by-sides, so you’re starting from scratch in understanding its strengths and weaknesses.....
 
l - its a different design than on the other side-by-sides, so you’re starting from scratch in understanding its strengths and weaknesses.....

Yep, that's my point, if it wasn't clear it's because I rarely articulate well.... I just want to point out that any one of these planes is just a bunch of parts. You can apply them and modify them as you see fit, as long as you are capable and interested. If you don't have those skills, don't do it. That and there are easier ways to get an aerobatic 9. Like a 7 :)

Tim
 
IMHO, it is not just about G loads. If you have some type of mis-hap while doing aerobatics in a non-aerobatic approved airplane, there is a good chance that you will have significant challenges with both the FAA and your insurance carrier, even if the G loading was under the max for the utility class.

Larry
 
You would also have to completely analyze and address the tail - its a different design than on the other side-by-sides, so you’re starting from scratch in understanding its strengths and weaknesses.....

And the engine mount and the battery box and..and...and...
 
It kind of depends on what you consider aerobatic maneuvers:

- 60 degree turns are 2G can be done in any utility aircraft
- Hoover roll (1G positive all the way around) can be done in any airplane with sufficient inertia and roll rate. Hoover has shown that and many have validated it. A competition roll is much more aggressive on the airframe. So don't do those.
- A round loop will likely be above utility G limits. Just "getting around" a loop is generally not.
- An airplane either spins or it doesn't so that's not something to play with lightly ...
- Combined maneuvers might be more tricky as e.g. to do a 1/2 cuban you really can't do a bad partial loop followed by a 1/2 hoover roll. You will end up way past VNE pointing down... .

There are of course two other things to consider:
1. Safety: You reduced your safety margin for screw ups quite a bit. You don't have to be superman but you do need to know what you are doing. You will literally have no time to experiment as things on a downline in any RV happen fast... . However, even aerobatic rated RVs are not a free for all as the crash of the RV-8 demonstrator due to over stress showed a few years back. You just have more margin and therefore more time.

2. Legal: You likely have to take the airplane back to phase 1 to get the proper log book entry assuming you have the needed language in your operation limitations. Not sure how the FSDO would react to that.

Oliver
 
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Good day Ron, I am looking for a quality RV-9A to buy, you mention seeing lots for sale. Can you advise where you are seeing all the RV-9's for sale please? I am checking all the usual sources, here and the airplane sales publications. No joy.

Many thanks, Dave.
 
oh really??

Scott... now I am challenging you to post a photo of you in that bikini on the beach.....

Back to the thread... so I don't get zinged. I have aileron rolled the 9A as part of upset training. (wake turb.) But, an aerobatic plane.... it is not.
As the others have said, buy a different wing spar.
Cheers.
 
How

Step 1. TAke the RV-9 tail off and install RV-8 tail.
Step 2. Take both wings off and set in corner of shop.
Step 3. Do research on how to convert a Diesel engine to the RV airframe
Step 4. Ponder the complexities of adapting said Diesel engine to somehow drive a prop without self destructing
Step 5. Let project sit in hangar for decade while you grow too old to fly
Step 6. At your demise, your family will be forced to figure out what all this **** is and sell it for scrap prices
Step 7. Some young buck buys the pile at a discount and starts to put together asking a Bunch of questions on VAF
Step 8. Vic S is called to do a Prebuy on the pile and he writes a book about it and becomes rich.
Step 9. Dan H somehow gets the airframe and does a torch test on it and it fails due to the diesel fuel tank mounted on wrong side of firewall
Step 10. I drive over to wetumpka Alabama to visit my daughter and stop by airport and pick up the heap and take home and scrap the whole project except for the RV-8 tail which I hang on my ceiling.
Step:11 This completes the lifecycle of converting a RV-9 to an aerobatic plane. I may have omitted some steps in the interest of journalists brevity, so do accept my sincere apology.
 
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