O

oz8

I'm New Here
Hi all,

I'm curious to know more about the aerobatic capabilities of the RV-8, particularly with a passenger. I would like to be able to fly mild aero's two up, just loop and roll type stuff. I'll leave the lomcevaks etc. to the Pitts drivers :D
How does the -8 perform with a pax? I'm 6'4" 200 pounds; my passengers would range from my wife (120 lbs) to a couple of mates my size. I'd like to know about CG issues (if any), spin recovery with a pax (not planning to spin deliberately, but you never know...) pitch forces with a pax and so on. Is the -8 a good mount for dual aerobatics? Or should I build something else?

Thanks in advance, Adrian.
 
Adrian,

I am 6'-5" and 255 pounds. I flew as a passenger on several occasions in an 8 where the pilot was around 220 pounds. Quite a load.

The 8 handles it with ease. We have done several loops, rolls, and split S's. The airplane performs greatly. Each was done at well less than maximum power.

That was one of the main factors in my building an 8.

I don't think you willl have any issues with how it performs with two aboard.

Regards,

Donald
RV-8 Empennage Underway
N-284DP Reserved
 
Performance is not a problem, but there are two potential issues - weight and CG.

Weight - Van has designed the structure to handle 6g at the aerobatic gross weight. This was 1550 lb until some time in the last few years when a design change allowed it to be increased to 1600 lb. Depending on how heavy the aircraft is (major factors are engine, prop, inverted oil system, avionics, paint weight, and all the extra stuff that people are tempted to add), how heavy the people are, and how much fuel you want to have, you may or may not be able to fly at 1550 or 1600 lb with two people.

CG - Van recommends forward and aft limits of the CG envelope. If you are doing aerobatics, he recommends a more forward aft CG limit. I assume this is to keep the stick force/g from being too light, but I am only making an educated guess here. Depending on the empty CG of the aircraft, and the pax weight, you may or may not be able to fly at this CG.

You can play around with the weight and balance calculator on Dan Checkoway's web site. He has a Weight and Balance Database with data from flying aircraft. Click on the N-number of an aircraft (or the model name in the list at the top) to get a page where you can run W&B scenarios.

I looked at a couple of scenarios, just for amusement. If you pick the lighter aircraft, you might have some hope with two 225 lb people, and 20 USG of fuel, except that the CG is too far aft. If you pick one of the mid-weight aircraft, with a more forward CG, you can keep the CG inside the recommended envelope, but you have to back off on the weight to 200 lb per person (including parachute).

From a practical point of view, if you intend to abide by Van's weight and CG recommendations, the RV-8 is probably not a suitable two-person aerobatic aircraft. People do fly aerobatics with pax, but they are probably heavier than the recommended gross weight, and at aft CG. The aft CG means a lighter stick force/g, which increases the chance of an inadvertent overstress. Being overweight reduces the ability of the structure to handle the inadvertent overstress.
 
oz8 said:
Hi all,

I'm curious to know more about the aerobatic capabilities of the RV-8, particularly with a passenger. I would like to be able to fly mild aero's two up, just loop and roll type stuff. I'll leave the lomcevaks etc. to the Pitts drivers :D
How does the -8 perform with a pax? I'm 6'4" 200 pounds; my passengers would range from my wife (120 lbs) to a couple of mates my size. I'd like to know about CG issues (if any), spin recovery with a pax (not planning to spin deliberately, but you never know...) pitch forces with a pax and so on. Is the -8 a good mount for dual aerobatics? Or should I build something else?

Thanks in advance, Adrian.
Click to expand...

The 8 willl be fine for this task.
 
Aft CG

Thanks for the information. I really would like to build an -8, and if I do I intend to keep it light and simple. That means O-360, fixed pitch Sensenich, carburettor, minimal gadgets and maybe light landing gear. I have played around with Dan Checkoway's weight and balance chart (nice work Dan :) ) and found that Brian Denk's bird, similarly equipped to to what I would build, is within aerobatic CG limits with two 200 pounders on board. It's close to the aft aerobatic CG limit though, and this is what concerns me. How tolerant is the -8 of this kind of loading? In an inadvertant spin scenario, would recovery be difficult? Impossible :eek: ? I would like to hear your experiences!

Thanks again, Adrian
 
For casual loop & roll stuff the RV-8 is fine with a GIB. Exercise some caution with a heavy back seater, because pitch forces do lighten significantly, and you may pull more than you realize. I wouldn't let the GIB fly aerobatics unless you are very sure of their skills and prudence

I'm surprised at how little difference a back seater makes to the performance and handling of the RV-8. The -8s (compared to the rest of the RVs) tend toward forward C of G anyway.

My airplane will easily loop from cruise solo with about 2.5 ":g", and with two up I usually use about 3.

The heaviest backseater I have flown is 260#. At that CofG, I wasn't comfortable with anything over the top, but I did do an aileron roll. I wouldn't want to fly the airplane with the CG any more aft than that, although I was still well within Van's suggested limits.

I weigh about 165#, and my airplane is at 1099# with and empty CG of 78.5"

James Freeman
 
Dual acro? OK, just not for me, thanks.

oz8 said:
Thanks for the information. I really would like to build an -8, and if I do I intend to keep it light and simple. That means O-360, fixed pitch Sensenich, carburettor, minimal gadgets and maybe light landing gear. I have played around with Dan Checkoway's weight and balance chart (nice work Dan :) ) and found that Brian Denk's bird, similarly equipped to to what I would build, is within aerobatic CG limits with two 200 pounders on board. It's close to the aft aerobatic CG limit though, and this is what concerns me. How tolerant is the -8 of this kind of loading? In an inadvertant spin scenario, would recovery be difficult? Impossible :eek: ? I would like to hear your experiences!

Thanks again, Adrian
Click to expand...

You're clearly a man of sound reasoning and excellent taste in outfitting an RV8. :D My -8 is reasonably light, and has ample loading allowance to stay within 1550# acro gross. For me, that means half fuel and back seat bubba factor below 200 pounds. In general, I avoid looping maneuvers as it puts me in a more aft CG range, inverted and slow condition over the top. I certified my -8 for upright spins while solo only. Never tested inverted, dual spins. Don't wanna go there.

So, maneuvers that can get me into an untested attitude, are avoided. I will do 1G rolls (pitch, lock, roll, finish nose on horizon) as much as any back seater wants as they are comfortable, easy on the airplane and usually do not peg anyone's hurl meter. No puke in my airplane in six years of flying and I intend to keep it that way! :eek:

Yes, the airplane is tough enough to handle the loads, but I like to keep dual flights fairly mild. It's just my personal limit, not the airplane's.
 
Dual acro

FWIW I see no problem with dual acro as long as wt and balance are in limits. I'm curious - did all you guys test your airplane at the aft CG limit and max weight during phase I? I thought we were to fully explore and validate the flight envelope during that time. I guess if we all were to do that we'd know just what loading conditions are comfortable for us. If we don't explore these regimes, I thinkwe're required to placard new limitations on the plane reflecting what was actually demonstrated during phase I. Is there someone who can clarify this with authority? Thanks in advance - I'm not yet flying but did explore the full envelope with our Pitts. Personally, I like flying the Pitts at an aft CG - it's more fun! Bill
 
Bill,
You are right on! The full range of weight and C/G are to be tested during phase I. If not, then your flying must be limited to the weight and C/G to which you DID test. There is no one looking over your shoulder to make sure you do this, but if you don't, it's like your high school teacher said, "You're only cheating yourself."
 
Dual spins

In the United Kingdom the -8 has been approved for spinning as of March this year by the PFA (within aerobatic CG limits of course). This implies that it has been tested through the full range of aerobatic loadings and spin attitudes. Reassuring to know should you accidentally wind up in an inverted spin with bubba in the back!

Cheers, Adrian
 
I seem to remember Vans first RV-8 accident involved two large people in the airplane. Altitude is life!

Jeff
-8 wings
 
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