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11-14-2011, 11:57 AM
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Join Date: Jan 2007
Location: Battleground
Posts: 4,348
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Quote:
Originally Posted by Russ McCutcheon
""Also its been said that a ground loop is not a question of if but a question of when"".
I can't answer your question but I will say I have heard this saying before and I don't agree. I also don't agree that you have to land gear up at any point if you fly retract.
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That saying is to make those of us that have feel better. 
__________________
Smart People do Stupid things all the time. I know, I've seen me do'em.
RV6 - Builder/Flying
Bucker Jungmann
Fiat G.46 -(restoration in progress, if I have enough life left in me)
RV1 - Proud Pilot.
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11-24-2011, 08:59 AM
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Join Date: Feb 2005
Posts: 426
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% accidents matches population distribution
Quote:
Originally Posted by LeeM_2000
Yeah, I did this research last year. I was mostly concerned with attempting to figure out the impact of the A-model doink-over, but you can see that accidents are fairly even between the two configurations given my considerable margin of error.
According to what I have been able to pull up from the NTSB database from 1/1/2000 to 9/25/2010:
I counted 300 total RV accidents broken down as follows:
66% non-A models
34% A models
32% (95) of the total RV accidents were fatal
57% (54) non-A of the fatal accidents--2 of those were nose-overs
43% (41) A models of the fatal accidents--4 of those were nose-overs
38% of the tricycle accidents ended with a nose-over
23% (70) of the RV accident reports have the term "nosed over" in the narrative. 'Nosed over' may not be an official catch-all, but it appears to be the term used when the airplane rotates about the nose and comes to rest inverted. Also, nearly all of the "nosed over" reports mention nose gear failure.
17% of all RV accidents reported were A model doink-overs
Nose-overs are broken down as follows:
71% (50) A models
29% (20) non-A models
Conclusions:
This is not an exact science and it can be difficult to tell the apples from the oranges when reading accident reports.
Tri-cycle gear RVs are not significantly less accident-prone than conventional gear RVs. That is, unless there are fewer tail dragger RVs flying than tri-cycle RVs. I sort of assumed a slight edge to the tail dragger.
Nosegear failure contributes to 17% of all RV (tail dragger and nose dragger combined) accidents and 1% of the fatal accidents
Rollover accidents in RVs are not particularly deadly, always but substantially damage the airframe.
Rollover accidents occur more that twice as frequently in A model RVs as in non-A model RVs and rollovers are twice as deadly in A model RVs.
Most of the nose-overs happen after botched landings, but a fair number are due to engine failure and related off-airport landings.
Stipulations:
I don't know the total number of flying RVs and how many of each type there are.
Not all accidents are reported to the NTSB.
Model names can be misrepresented by the reports.
I did not consider other accident causes and a fair number cite improper landing technique.
There is a lot more to be gleaned from the NTSB reports, but this is all I had time for. If you don't like my numbers, go figure your own.
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Based on the data for the number of A models and tail draggers presented in this thread the accident distribution matches very closely. Of the 3,4,6,7,8,and 9 model RVs 2475 are A models and 4158 are tail draggers. That is 37% A models and 63% taildraggers. So the accident rate present in the FAA data base matches pretty well the distribution of types of airplanes flying. We can conclude they are about equally likely to have an incedent reported. The Nose over rate however is (not surprising) is much higher for the A models
(50/2475 vs 20/4158 roughly).
__________________
John Adams
Seattle
RV7 600+hrs
Paid 12/2014
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11-24-2011, 09:22 PM
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Join Date: Apr 2006
Location: Arizona
Posts: 387
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It's the Pilots!
John,
It?s probably more accurate to say the nose-over rate WAS higher for ?A? models based on the reported data. There is no way to know from the reported numbers the effect of the recent nosewheel mods or, more importantly, increased pilot awareness of proper ?A? model operation. Again, I would suggest that the individual pilot is the best place to look for analyzing and improving RV safety. Both RV models, as designs, appear to be safe. From the numbers, the one inescapable, valid conclusion is that it?s the pilots (us!) that need further development!
Bill Palmer
P.S. I wonder what this thread would look like if the rate of RV tailwheel model ground loops and prop strikes were analyzed in detail?  Based on past experience, I don?t think one would be able to draw valid conclusions about RV tailwheel safety from the reported numbers. Once again, as always, it would boil down to the pilot; not the RV tailwheel (or nosewheel)!
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11-24-2011, 10:17 PM
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Join Date: May 2009
Location: KS
Posts: 110
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No doubt it's the pilot, but I'm not sure ground loops are really comparable to doink-overs since it is reasonable to assume that most of them do not get reported because they do not meet the "substantial damage" or "injuries" criteria for reporting an accident. I suspect a lot of non-doink-over nose gear fails do not get reported for the same reason.
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11-24-2011, 11:01 PM
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Join Date: Sep 2009
Location: London
Posts: 167
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Assuming there are 2,700 RV NG flying,
and the average RV does 100 landings per year.
We are looking at 270,000 landings per year.
Even if they only do 50 landings a year (this is only an estimated average),
that's 135,000 landings a year!
If the NG design is deficient,
you will be seeing a lot higher incidents (and at a more regular interval) than what is reported.
Just my 2c.
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11-25-2011, 06:34 AM
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Join Date: Jan 2005
Location: SC
Posts: 12,887
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Interesting thought - Staying current
Since January, when I got my -9 flying again with the new engine I have put 83 hours and performed 147 landings (Lots of YE flights in there) for a a ration of 1.8:1 landings per flight hour.
If I go back to when the plane first flew the numbers are 537 landings to 337 hours for a landings per hour ratio of 1.6:1.
__________________
Bill R.
RV-9 (Yes, it's a dragon tail)
O-360 w/ dual P-mags
Build the plane you want, not the plane others want you to build!
SC86 - Easley, SC
www.repucci.com/bill/baf.html
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11-25-2011, 06:52 AM
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Join Date: Feb 2011
Location: USA
Posts: 3,179
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Not germain to this thread but ...
Quote:
Originally Posted by Webb
its been said that a ground loop is not a question of if but a question of when.
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I actually believe this old saying is pretty faithful. The clarification is this "generalization" - like all statistics - conciders the entire fleet of conventional gear airplanes. There are some designs less prone to ground loops and some designs more prone.
For example, my RV-8 is pretty docile until the cross wind at landing suddenly bumps up to 18kts at 90 degrees (and my experience was that I prefer not to repeat dancing on the head of is particular pin). Contrast that with a Stearman in an unexpected 5-7kts cross wind and very quickly the back end can try to take lead. Back to this thread, the challenge with all of the accident data is that it's a limited data-set. It takes a large time range to cet a sufficient sampling and over that same time, the type of aircraft, distribution, pilot hours, runways, ADs, etc alter the data.
If we assume it takes the average builder 5+ years to build (more for the slow build kits). Then in 2000, nearly all the flying RVs would be 3, 4, 6, 6A, and some 8 models. Thus, the majority of RVs would be conventional gear. Fast forward to 2010 and it may be that more pilots are based at public and private airports with paved runways and thus tricycle gear RV's are significantly more prevalent than a decade ago.
My conclusion is that the RV is a well designed series and there are characteristics of each design which require attention. I would suspect Vans Aircraft would update the designs if there were statistical data suggesting a design was inferior or would widely benefit from a change.
JMO, YMMV, OFI, M2C
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11-25-2011, 08:24 AM
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Join Date: May 2009
Location: KS
Posts: 110
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Quote:
Originally Posted by RVnoob
Assuming there are 2,700 RV NG flying,
and the average RV does 100 landings per year.
We are looking at 270,000 landings per year.
Even if they only do 50 landings a year (this is only an estimated average),
that's 135,000 landings a year!
If the NG design is deficient,
you will be seeing a lot higher incidents (and at a more regular interval) than what is reported.
Just my 2c.
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It has been demonstrated that landing is not the only operation that can result in biffing the nose gear or doinking over. The design is clearly deficient. The magnitude of the deficiency is what is questionable. A lot of really smart dudes seem to perceive a relatively high probability of doinking. I suspect that's why Mr. Anti-Splat almost can't make his doo-hickeys fast enough. 
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11-25-2011, 08:57 AM
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Join Date: Jan 2005
Location: Richmond, VA
Posts: 696
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Quote:
Originally Posted by LeeM_2000
...The design is clearly deficient. The magnitude of the deficiency is what is questionable.
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While I respect your right to have an opinion on the subject, if you're going make multiple conclusion, as if they're factual, providing the data you've based your conclusion on would add substantially to your credibility. Note that the person you just quoted did exactly that, and has a level of credibility for doing so. I may choose to agree or disagree with him but at least I know the basis of his conclusion.
It is easy to misunderstand statistics, even when you're trying to discern what they're telling you. Without your data, I opine that you are doing a disservice by posting opinions as conclusions.
__________________
Don Alexander
Virginia
RV-9A 257SW Purchase Flying - O-320, Dynon D100
RV-9A 702DA (reserved) Finish Kit IOX-340
www.propjock.com
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11-25-2011, 09:03 AM
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Join Date: May 2009
Location: KS
Posts: 110
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Quote:
Originally Posted by Don
While I respect your right to have an opinion on the subject, if you're going make multiple conclusion, as if they're factual, providing the data you've based your conclusion on would add substantially to your credibility. Note that the person you just quoted did exactly that, and has a level of credibility for doing so. I may choose to agree or disagree with him but at least I know the basis of his conclusion.
It is easy to misunderstand statistics, even when you're trying to discern what they're telling you. Without your data, I opine that you are doing a disservice by posting opinions as conclusions.
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Definition of DEFICIENT
1: lacking in some necessary quality or element <deficient in judgment>
It is my opinion that landing gear should not tuck on landing or roll out under all but the most extreme conditions. In this case the necessary quality would be to NOT tuck and cause a rollover. There is plenty of evidence to suggest that this landing gear design can and will tuck under what I consider less than extreme conditions.
Last edited by LeeM_2000 : 11-25-2011 at 08:00 PM.
Reason: demoticonification
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