RV-9A

Adam Weiss

Adam Weiss

Pre-takeoff checklist
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Aug 10, 2017
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470
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KLXT
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kcmopilot
Just trying to gain some knowledge here.
Please don't beat me up or tell me how stupid or risky I am.

I was curious about doing an aileron roll in my RV-9A.
If done correctly, it shouldn’t exceed 2 g’s.

The 9A is NOT aerobatic, but is rated to +4.4/-1.75, so I thought it’d be OK.
I asked online and got all the “don’t do that... you’re stupid, no aerobatics means no aerobatics” responses.
I totally get it, and I really am risk averse.
And I understand that for rolls in particular, I could do it wrong and exceed the limits.
No thanks. Not for me.

But, I’m still trying to reconcile the data I see.
For example, a C172 has a similar G rating in the utility category as my RV, and is approved for intentional spins, chandelles, steep turns, stalls, and lazy eights.
Does this mean that those maneuvers could be done safely in an RV-9A?
Appreciate your knowledge in advance.
 
Ive got an RV-6 kit I will sell you, then there is no question.
 
Adam Weiss said:
For example, a C172 has a similar G rating in the utility category as my RV, and is approved for intentional spins, chandelles, steep turns, stalls, and lazy eights.
Does this mean that those maneuvers could be done safely in an RV-9A?
Click to expand...
Non-specific to the RV-9, chandelles, 'steep' (<60 deg bank angle) turns, and lazy eights should be easy to do without exceeding structural limits and more forgiving of mistakes and buffoonery than rolls. Stalls and spins may be restricted not only due to structural limits, but may also be limited by recovery characteristics. Specific to RV-9's, a little reading and talking to e.g. an EAA flight advisor or experienced RV-9 pilot might help understand if the recovery characteristics of either are such that recovery might be difficult or may put you in a situation where airframe limits (structural, aero, etc) might be exceeded.

The issue with rolls and structural limits is not an exceedence when flown correctly, it's when you bugger one up - which *will* happen - you can very quickly end up in a situation where your only choices are overspeed or overstress.

Nauga,
postholed
 
Can’t answer your question directly but I have it on good authority that the RV-10, which is also non-aerobatic, will roll after a fashion so I suspect the 9 will too.
 
There’s video of a guy do rolls in a 9. I have a 9 and won’t do rolls in it. Specially because if I’m gonna do any Afro, I’m gonna best up someone else’s plane.


Sent from my iPhone using Tapatalk Pro
 
Like Nauga said, it’s really when you screw one up is problem. One time I let a friend roll my Glasair. He didn’t get the nose high enough and then didn’t go full stick deflection. Instead of being inverted at the 180, we were pointed straight down and recovered with at least 4 Gs and hauling ***. With a 6G airframe, it’s not an issue.

My Velocity is stressed to 9 Gs but Velocity won’t approve aerobatics in them. I don’t think there’d be an issue but I read the CEO was worried about the slow roll rate and getting into the situation I described above.

I’d say if you are going to experiment with rolls in the RV-9, go up with someone experienced first. Of course wear parachutes. ;)
 
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You can roll a Citabria, Pitts, 747, Ford Trimotor, Shrike Commander, King Air, 172, and lots of other aircraft. Rolls don't impart much load at all. The problem is when you eff up. Something like a RV-9A will blow through redline faster than you can fart. That's when you pull the wings off. Three possibilities; you are good, you are lucky, or you are dead.
 
Adam Weiss said:
For example, a C172 has a similar G rating in the utility category as my RV, and is approved for intentional spins, chandelles, steep turns, stalls, and lazy eights.
Does this mean that those maneuvers could be done safely in an RV-9A?
Click to expand...
What does G rating have to do with spin recovery?
 
Good question and discussion.
 
Velocity173 said:
Like Nauga said, it’s really when you screw one up is problem. One time I let a friend roll my Glasair. He didn’t get the nose high enough and then didn’t go full stick deflection. Instead of being inverted at the 180, we were pointed straight down and recovered with at least 4 Gs and hauling ***. With a 6G airframe, it’s not an issue.
Click to expand...

The other mistake people make is failing to neutralize the elevator after the pitch-up. That's another technique for screwing up a roll and getting a windshield full of planet. Not that I've ever...um...done that.
 
Velocity173 said:
Instead of being inverted at the 180, we were pointed straight down and recovered with at least 4 Gs and hauling ***. With a 6G airframe, it’s not an issue.

My Velocity is stressed to 9 Gs but Velocity won’t approve aerobatics in them. I don’t think there’d be an issue but I read the CEO was worried about the slow roll rate and getting into the situation I described above.
Click to expand...
FWIW, higher g capability means you might not overstress during a botched roll but there's no guarantee you won't put yourself to sleep. Those without experience should get training in a capable airplane with a capable instructor.

Has any Velocity been *tested* to 9g? I really like the airplanes, but a 9g structure in what could have been a 3.8g design seems like a waste of weight margins.

Nauga,
and margins with margins
 
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I don't get the -9 in the market of 100K RV-9s and 30K M20Cs. I understand the history and literature/marketing differences from the 7, I just don't see it being worth the acro handicapping, especially with otherwise identical cabin volumetrics to the 7.

Closest I can think of was cost in its inception, as a kit for a small engine and lower stressed wing assembly, for those who swore they'd never be interested in going upside down. Reality was that most 9s were bolted to big engines in practice, and not the 235 it was intended for. So that cost benefit washed away, leaving the marginal differences of stall speed and climb/glide. Certainly a preference among those who need (or prefer) the margin of spam can trainer behavior in the regime of reverse command. Yet here's an 9 owner asking about how to roll it, so I rest my case.

nauga said:
FWIW, higher g capability means you might not overstress during a botched roll but there's no guarantee you won't put yourself to sleep.

Has any Velocity been *tested* to 9g? I really like the airplanes, but a 9g structure in what could have been a 3.8g design seems like a waste of weight margins.

Nauga,
and margins with margins
Click to expand...

One such theory I've heard bandied about was that since there is no predictability of behavior between plastic deformation and ultimate stress in the case of these fiber glass wonders (effectively non-existent), the assembly would have to be certified at a much higher baseline level to account for the "entropy" endemic to something without an observable yield strength, and thus unpredictable ultimate strength delta (nevermind fatigue life calculations).

Put simply, no way to calculate the safety factor with so much entropy built into the material selection and manufacturing outcome, especially for garage yahoos working with composites. Thence, you get these fiberglass ships taken to 9Gs to statistically "certify at 6" and a generally heavier empty weight. Overbuilt compared to their ductile counters. It's not gratuitous, just compensatory for lack of predictability. Don't quote me, but seems legit.
 
The 100k RV-9 is an epic cross country machine and super efficient at altitude. This is why tons of people own them and fly them. Including myself.


Sent from my iPad using Tapatalk Pro
 
Grum.Man said:
Go ahead, an aileron roll shouldn’t even exceed 1G. Get a good power setting, pitch up about 30 degrees and rack that puppy around.
Click to expand...

Absolutely terrible advice to someone who clearly has not gained aerobatic expertise and perspective on why he should not attempt this at this point, otherwise he'd not be asking such a question online.

OP, don't even think about it yet. The non-precision positive G aileron roll can literally be the easiest maneuver done in any RV, including the -9....IF you have sufficient experience to be past the point of falling victim to specific newbie pitfalls associated with this maneuver which could actually get you killed (and HAS killed pilots). Foolish advice like the post above do not cover these specifics. You need to get some aerobatic training with an instructor in a 6G (more safety margin) aerobatic airplane and have done a bunch of rolls on your own in something else before even thinking about whether this is suitable for YOU in your RV-9. Then you will have the proper perspective.

The truth is that if you have the minimum required competency and training, you can do a thousand positive G rolls in a row in the -9 without messing them up or putting more than 2G on the meter. And that 2G should not even be seen while actually rolling, but this is beyond the scope here. You need to be past the learning process, and that is the whole point. Those who attempt to teach themselves aerobatics have a fool for an instructor. OP, fortunately you don't seem prone to this attitude, and seem to be asking an academic question at this point, which is fine.
 
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nauga said:
FWIW, higher g capability means you might not overstress during a botched roll but there's no guarantee you won't put yourself to sleep. Those without experience should get training in a capable airplane with a capable instructor.

Has any Velocity been *tested* to 9g? I really like the airplanes, but a 9g structure in what could have been a 3.8g design seems like a waste of weight margins.

Nauga,
and margins with margins
Click to expand...

No idea on their testing process. I would think if they’re claiming +9/-7 Gs, or in the case of the SE, +12/-9 Gs, they would have at least done some static load tests.
 
Velocity173 said:
I would think if they’re claiming +9/-7 Gs, or in the case of the SE, +12/-9 Gs, they would have at least done some static load tests.
Click to expand...
As would I, but the factory website specs clearly show the "Tested Airframe Load" is 6g for models with +9/-7 and +12/-7 design load factors. Link

Nauga,
who wants to believe
 
nauga said:
As would I, but the factory website specs clearly show the "Tested Airframe Load" is 6g for models with +9/-7 and +12/-7 design load factors. Link

Nauga,
who wants to believe
Click to expand...

Does tested mean breaking point or tested as in approved for 6 Gs but damage occurs at either 9 or 12 Gs? I know in Longezs they’ve been tested to 6.5 Gs with no failure. Canard to 12 Gs.

I know a way to settle this. I’ve got a Blue Mountain in the Velocity that displays Gs. I’ll take her up tomorrow, pull 9 Gs and take a picture of it for proof.

Velocity173,
Who can “hook” with the best of them
 
Velocity173 said:
Does tested mean breaking point or tested as in approved for 6 Gs but damage occurs at either 9 or 12 Gs?
Click to expand...
To me tested means tested, not 'tested without damage,' 'tested to failure,' or 'tested and cleared' but if I were going to operate above 3.8g I'd get clarification or do the testing myself.

Velocity173 said:
I know a way to settle this. I’ve got a Blue Mountain in the Velocity that displays Gs. I’ll take her up tomorrow, pull 9 Gs and take a picture of it for proof.
Click to expand...
At gross weight for score ;)

If you really want to impress me also get one at -7g.

Nauga,
loaded
 
nauga said:
To me tested means tested, not 'tested without damage,' 'tested to failure,' or 'tested and cleared' but if I were going to operate above 3.8g I'd get clarification or do the testing myself.

At gross weight for score ;)

If you really want to impress me also get one at -7g.

Nauga,
loaded
Click to expand...

I’m not sure if my 3 point seat belts that came from a car are approved for negative Gs.
 
Velocity173 said:
Does tested mean breaking point or tested as in approved for 6 Gs but damage occurs at either 9 or 12 Gs?
Click to expand...

My guess is, the latter. The idea being they can't certify to the yield because there is not one, so they have to go to ultimate. Obviously you can't certify to that point. But because ultimate is so scattered in the modeling (material and manufacturing entropy), they have to observe an even higher failure point and "certify down" to a probabilistic threshold that won't lead to failure, in order to mimic the safety factor calculation readily available for ductile materials. As such, they end up being overbuilt as individual samples. Aerobatic limits are thence easily met, and they could go lower if they wanted to, which is not really in marketing's interest.

It's still gonna be heavier than the ductile counterpart, because of the unpredictability. But it also means you're probably alright pulling to your heart's content. The only real opportunity cost for these types is fatigue life, if consistently stressed to the certified limit. That's because of the equally nutty crack propagation dynamics (or lack thereof) compared to ductile/homogeneous setups. No free lunch in life.

I'm a little skittish of amateurs and composite manufacturing. I've seen the aftermath of what one of my professional peers had in its hands at the time of his early demise. His own build. The NTSB wasn't impressed. But that's my risk tolerance and biases. Placebo as it may be, I'm a little more willing to play russian roulette on a paint by numbers rivet tin can job like an RV. But with the right vetting and trained eyes (I admit not to possess the expertise to evaluate composite manufacturing of a completed/sealed sample visually, let alone things you would need NDT in order to qualify) I suppose it would be no worse or even better than a poorly assembled factory job. One's monkey one's circus and all that jazz.
 
Peter Anderson said:
The 100k RV-9 is an epic cross country machine and super efficient at altitude. This is why tons of people own them and fly them. Including myself.


Sent from my iPad using Tapatalk Pro
Click to expand...
^This.
Original poster here.
Off topic, but I debated between M20E and RV-9 for a long time.
For me, RV-9 was a slam dunk. 5-10kts faster, fixed gear, lower MX, insurance and fuel burn, way more options for parts and avionics. Same mission.
Decent M20E $60-$70K. Got my 9 for $70K.

My 95% mission is fast XC with the wife to go see our kids.
Based on G ratings just wondered if any of these other things would be possible on the 5% use case of messing around in the area.
 
hindsight2020 said:
Aerobatic limits are thence easily met, and they could go lower if they wanted to, which is not really in marketing's interest.
Click to expand...
The airplane we're discussing is not aerobatic, and all that additional weight to overdesign the structure reduces the useful load, which is also not really in marketing's interest, at least with respect to an informed/educated customer.

Nauga,
stressed to impress
 
Adam Weiss said:
Just trying to gain some knowledge here.
Please don't beat me up or tell me how stupid or risky I am
Click to expand...

I won't beat you up, my arms aren't long enough. But, the average idiot knows not to pull the stupid and risky maneuver your describing.

Please tell us you aren't serious.
 
I must be dumber than the average idiot.
Still looking to see if you can do chandelles, lazy 8s, etc in a 9.
It’s clear a roll is too risky.
Trying to understand what limitations would constrain those maneuvers.
Spin would be limited by rudder authority.
 
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Velocity173 said:
Does tested mean breaking point or tested as in approved for 6 Gs but damage occurs at either 9 or 12 Gs?
Click to expand...

hindsight2020 said:
My guess is, the latter.
Click to expand...
If that's the case it's unfortunate that they chose terminology that closely resembles that with a very different meaning.

Nauga,
riding the limiter
 
Adam Weiss said:
I must be dumber than the average idiot.
Still looking to see if you can do chandelles, lazy 8s, etc in a 9.
It’s clear a roll is too risky.
Trying to understand what limitations would constrain those maneuvers.
Spin would be limited by rudder authority.
Click to expand...

I don't include chandelles and lazy 8s in the category of "aerobatic." They are more accurately described as precision flying maneuvers.
 
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@nauga -- Even if done "right" it's outside of the oplims of an RV-9. How does that work with the stupidity meter?

upload_2020-1-1_16-9-7.png
 
hindsight2020 said:
My guess is, the latter. The idea being they can't certify to the yield because there is not one, so they have to go to ultimate. Obviously you can't certify to that point. But because ultimate is so scattered in the modeling (material and manufacturing entropy), they have to observe an even higher failure point and "certify down" to a probabilistic threshold that won't lead to failure, in order to mimic the safety factor calculation readily available for ductile materials. As such, they end up being overbuilt as individual samples. Aerobatic limits are thence easily met, and they could go lower if they wanted to, which is not really in marketing's interest.

It's still gonna be heavier than the ductile counterpart, because of the unpredictability. But it also means you're probably alright pulling to your heart's content. The only real opportunity cost for these types is fatigue life, if consistently stressed to the certified limit. That's because of the equally nutty crack propagation dynamics (or lack thereof) compared to ductile/homogeneous setups. No free lunch in life.

I'm a little skittish of amateurs and composite manufacturing. I've seen the aftermath of what one of my professional peers had in its hands at the time of his early demise. His own build. The NTSB wasn't impressed. But that's my risk tolerance and biases. Placebo as it may be, I'm a little more willing to play russian roulette on a paint by numbers rivet tin can job like an RV. But with the right vetting and trained eyes (I admit not to possess the expertise to evaluate composite manufacturing of a completed/sealed sample visually, let alone things you would need NDT in order to qualify) I suppose it would be no worse or even better than a poorly assembled factory job. One's monkey one's circus and all that jazz.
Click to expand...

You can have just as many surprises with a used metal homebuilt. Corrosion, spar cracks, etc. Which design (composite vs metal) is more tolerate of builder error?

Not a single Glasair has had a structural failure. To be honest, don’t recall any Lancairs either. Vans can’t make that claim.

Fiberglass diving boards and surf boards...they never break.:)
 
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Ravioli said:
@nauga -- Even if done "right" it's outside of the oplims of an RV-9. How does that work with the stupidity meter?
Click to expand...
If I were the worrying type I'd be less concerned about someone (the OP) who asked about it *before this thread* and had decided it was not smart and more about others who imply *in this thread* that they've done it in airplanes similarly limited.

Nauga,
threaded
 
I would go for 20 nose up and coordinated to whichever direction you feel more comfortable with, but again it shouldn't be any G's involved.
 
Adam Weiss said:
^This.
Original poster here.
Off topic, but I debated between M20E and RV-9 for a long time.
For me, RV-9 was a slam dunk. 5-10kts faster, fixed gear, lower MX, insurance and fuel burn, way more options for parts and avionics. Same mission.
Decent M20E $60-$70K. Got my 9 for $70K.

My 95% mission is fast XC with the wife to go see our kids.
Click to expand...
My M20c is maybe 10 knots slower. One can be head easy in the 30's. Mine was more, but mine's nice. Different is I can take Mrs. Steingar and her **** (and the dog) to see whoever. I could probably bring the neighbor along while I was at it. Can't quite pull that off in your RV. I have to admit, there is something to getting parts at NAPA, though my Mooney doesn't really bread all that often.
 
steingar said:
My M20c is maybe 10 knots slower. One can be head easy in the 30's. Mine was more, but mine's nice. Different is I can take Mrs. Steingar and her **** (and the dog) to see whoever. I could probably bring the neighbor along while I was at it. Can't quite pull that off in your RV. I have to admit, there is something to getting parts at NAPA, though my Mooney doesn't really bread all that often.
Click to expand...
I can’t argue. If I’d have gone certified, it definitely would have been Mooney. They’re great machines.
 
Adam Weiss said:
I can’t argue. If I’d have gone certified, it definitely would have been Mooney. They’re great machines.
Click to expand...
And if one could be had for Mooney money I'd fly an RV, they're great machines. But they can't be had for Mooney money, and Mrs. Steingar doesn't like them.
 
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