RV-7 or RV-6

[RV7A Flyer]

Originally Posted by sailvi767

In the Utah accident they actually have zero idea what happened other than Mountain wave and turbulence that day. Both occupants were highly experienced pilots and I doubt they made abrupt inputs. The level of turbulence could have been extreme but no one really knows.

Postaccident examination of the airplane revealed damage to the horizontal stabilizers and elevators that was consistent with a downward failure in positive overload. The loads required to fail the horizontal stabilizers and elevators cannot be generated from normal flight or control movements. Such failures would have required an abrupt pull back on the stick and corresponding movement of the elevator to a trailing-edge-up position, at speeds greater than the airplane's maneuvering speed. Failure of the horizontal tail first would have caused the airplane to pitch down rapidly, producing air loads on the upper surface of the wing that were sufficient to fail them in negative overload. The damage observed on the wings was consistent with a downward failure in negative overload. Additionally, there were no indications of any pre-existing cracks or anomalies with the horizontal stabilizers, elevators, or wing structures, and no pre-accident anomalies were observed that would have precluded normal control of the airplane.

Probable Cause and Findings
The National Transportation Safety Board determines the probable cause(s) of this accident to be:
The pilot's abrupt flight control inputs, likely above the maneuvering speed, in severe winds and turbulence conditions, which resulted in an in-flight breakup.

Given that they're the ones who did all the analysis, including examination of the wreckage, metallurgy, whatever, and nobody here did, this is the best we can do...but they certainly didn't have *zero idea* what happened. In any case, claiming that this was because of rudder failure, contradicting the NTSB report, without any evidence is misinformation at best.

[sailvi767]

Originally Posted by RV7A Flyer

Given that they're the ones who did all the analysis, including examination of the wreckage, metallurgy, whatever, and nobody here did, this is the best we can do...but they certainly didn't have *zero idea* what happened. In any case, claiming that this was because of rudder failure, contradicting the NTSB report, without any evidence is misinformation at best.

I never claimed it was rudder failure. I simply stated it was an accident that was not caused by a VNE over speed. I suspect as I pointed out extreme turbulence might have been a factor. Inflight breakups of airframes without a known underlying cause are fortunately one of the things that does get NTSB attention. This was as you mentioned properly investigated unlike most light aircraft accidents. What caused the overstress was however supposition on the part of the NTSB. I lived and flew extensively in the area years ago so it hit close to home. The part that really got my attention is the forecast only called for moderate turbulence. Still mountain wave is nothing to take casually in the area. I once was descending into the valley 20 miles south of SLC and we lost 50 knots of airspeed in about 5 seconds. It was a eye opener!

[RV7A Flyer]

Originally Posted by sailvi767

I never claimed it was rudder failure. I simply stated it was an accident that was not caused by a VNE over speed. I suspect as I pointed out extreme turbulence might have been a factor. Inflight breakups of airframes without a known underlying cause are fortunately one of the things that does get NTSB attention. This was as you mentioned properly investigated unlike most light aircraft accidents. What caused the overstress was however supposition on the part of the NTSB. I lived and flew extensively in the area years ago so it hit close to home. The part that really got my attention is the forecast only called for moderate turbulence. Still mountain wave is nothing to take casually in the area. I once was descending into the valley 20 miles south of SLC and we lost 50 knots of airspeed in about 5 seconds. It was a eye opener!

But why even bring it up? Per the NTSB, someone yanked the snot out of the stick while over Va and tore things off the plane. That could happen in ANY aircraft, and it's not a design problem. It's a PILOT problem.

The OP was asking about a 6 vs a 7, and some people here have resurrected the thinking that changing a well-built 7's rudder based on TLAR "engineering" is somehow something the OP should do lest he kill himself by exceeding Vne by 1 knot and inducing flutter.

It's *misinformation* at best, fear-mongering at worst. *Stay within the envelope*.

Based on the results of our various design and testing programs, we determine and publish do-not-exceed limits for calculations such as max gross weight, max G-loading, etc. When we publish specification numbers for our aircraft designs, we expect that people will stick by those limits when they build, certify and fly their airplanes. While we do, of course, build in a certain safety margin or “buffer,” it’s very important to understand that these margins “belong” to the engineer – not to the builder. Pushing the limits is just that. So, unless you are fully and uniquely qualified to assess your own custom design (in which case you’re on your own, of course) we will tell you — quite directly — that the published limits are the limits. Period.

Van's Aircraft (emphasis added)

[sailvi767]

I believe the aircraft was possibly overstressed. I don’t believe a highly experienced pilot yanked the **** out of it. I suspect they encountered severe turbulence that induced high vertical G loads. In another life I pulled a lot of G. The aircraft should have taken 6 G’s without a failure and should been able to go beyond that without a inflight breakup. 6 G’s is a very high loading to intentionally pull in a RV. The 9 G ultimate load is extreme G to pull. This pilot should have been well versed on how to handle an aircraft in a turbulence encounter. The NTSB makes no mention that this was a pilot induced accident or that the aircraft was above VA. The last radar track had a max groundspeed of 133 knots. In the end the report basically has no solid conclusions.

“A review of the weather information indicated that there were likely low-level winds gusting from 26 to 46 knots at the time of the accident and that moderate-to-severe turbulence likely existed at the accident site. The weather conditions likely contributed to the in-flight breakup by either aggravating a flight maneuver or preventing a recovery from a loss of airplane control.”

[RV7A Flyer]

Originally Posted by sailvi767

I believe the aircraft was possibly overstressed. I don’t believe a highly experienced pilot yanked the **** out of it. I suspect they encountered severe turbulence that induced high vertical G loads. In another life I pulled a lot of G. The aircraft should have taken 6 G’s without a failure and should been able to go beyond that without a inflight breakup. 6 G’s is a very high loading to intentionally pull in a RV. The 9 G ultimate load is extreme G to pull. This pilot should have been well versed on how to handle an aircraft in a turbulence encounter. The NTSB makes no mention that this was a pilot induced accident or that the aircraft was above VA. The last radar track had a max groundspeed of 133 knots. In the end the report basically has no solid conclusions.

“A review of the weather information indicated that there were likely low-level winds gusting from 26 to 46 knots at the time of the accident and that moderate-to-severe turbulence likely existed at the accident site. The weather conditions likely contributed to the in-flight breakup by either aggravating a flight maneuver or preventing a recovery from a loss of airplane control.”

Probable Cause and Findings...The pilot's abrupt flight control inputs, likely above the maneuvering speed

NTSB (emphasis added)