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RV-7A down in NZ 01/01/18 - Accident report released

KRviator

Well Known Member
ZK-DVS, an RV-7 was involved in a fatal accident 2 years ago. The report has just been published by the NZ CAA, available in PDF format HERE.

In short, it is an exact carbon copy of the Canadian RV-7 accident involving C-GNDY, whose report is available HERE, also in PDF format.

From the NZ report (my bolding)
At approximately 1217 hours, the aircraft entered a high angle of bank (AoB) manoeuvre, achieving 70 degrees AoB. Five seconds later the AoB increased to 130 degrees and the aircraft began to pitch nose-down. During the resulting descent, the indicated airspeed was recorded at 244 knots (kts), which exceeded the aircraft ‘never exceed speed’ (Vne).

Approximately 30 seconds after entering the high AoB manoeuvre, witnesses observed the aircraft break up in flight and then impact terrain approximately three nautical miles southwest of Te Kopuru.

<SNIP>
In-flight breakup occurred as a result of rudder flutter, as the aircraft airspeed exceeded the design limitations

From the Canadian report:
Following a rapid descent (10 560 fpm down, 45° nose-down pitch), the aircraft progressively descended during the manoeuvres to approximately 1690 feet asl (800 feet agl). It reached airspeed of 234 knots before levelling momentarily at 1870 asl. The last EFIS record prior to impact indicated a nose-down pitch of 31°, right bank of 105° and airspeed 181 knots.

<SNIP>
The aircraft encountered either flutter or overstress of some rudder components. Subsequently, the vertical stabilizer and parts of the rudder separated from the empennage during flight. Consequently, the aircraft became uncontrollable resulting in the impact with terrain.

VAF'ers - Our VNE's are based on flutter, which is based on TAS - NOT KIAS.

Pilots need to learn from the mistakes of others. In aviation, we aren't going to live long enough to make all of them ourselves. We are better than this. We have to be.
 
244 KIAS, wow! I didn't see any weather to calculate true airspeed but I'm betting it was much higher! The report even mistakes the 200 kts Vne as indicated instead of true.
 
Unzipped Rudder

Another design exceeded, another unzipped rudder, another fatality. Want more margins? Don’t exceed VNE, but if you anticipate you will, trashcan that zipped rudder and put a RV-8 rudder on it which has a folded design and a bit more margin built in. I put one on my -9 and the folded edge is the ticket. Yea I know the spin recovery takes a little bit longer but we no spin.
 
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Tragic and so unessesary:confused:
I'm always amazed at how many Pvt drivers out there really don't understand VNE or even Va, TAS to some is something akin to Airliners!
 
The rate at which airspeed increases following a badly dished roll is an eye-opening experience. You'd better have that throttle back "right now" and already be in recovery or you'll quickly find yourself in a bad "corner".
 
Even Van's current documentation for the older airplanes is in error in this respect, where the document Airspeed Indicator Markings by Model shows Vne in terms of IAS and not TAS.

I'm not arguing on the points of your post as I agree with you..... But I interpret this section/document just as it says - 'these are the speeds in which to put the marks on the airspeed indicator'.

We can't mark an airspeed indicator for TAS - as it is always changing given the conditions and environment. I don't see the verbiage on this document as ultimate rule of true (airspeed) VNE. But at any rate I agree this document could be expanded to clarify.... 'This is where you will place marks on the airspeed indicator - however see below for True Airspeed (actual current condition) flight limitations....'
 
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Why the need to change to IAS l

I bet every airplane manufacturer has had this discussion about where to mark the for Indicated Airspeed. You want the best numbers. If you use 18,000 ft TAS, then the competition will eat your airspeed lunch cause they will use 8500 feet tas. The indicated airspeed will be faster and there goes the marketing. Descending from altitude say 17,000 ft which happens sometimes in RVs but probably not too often, Indicated airspeed is LOW and to the newbie, quite depressing. All the aircraft manufacture use IAS and they have a statement about corrections at altitude. Vans could do that too but I guess vans thinks it’s pilots are incapable of that maybe? Or maybe the marketing is so important that there is a resistant to revert to realistic IAS numbers. I don’t know but it has always bothered me that Vans departed from the industry standard by trying to go to TAS given that even today, people question it or don’t understand. On my twin, Mr Smith built an airframe that had lots of margins and the yellow area on the airspeed indicator is very small. I like margins. They make me happy happy happy.

I believe a case was made before to go back to the industry standard of realistic IAS indicator markings and leave the TAS in the manual. Maybe it’s time to revisit that effort.



I'm not arguing on the points of your post as I agree with you..... But I interpret this section/document just as it says - 'these are the speeds in which to put the marks on the airspeed indicator'.

We can't mark an airspeed indicator for TAS - as it is always changing given the conditions and environment. I don't see the verbiage on this document as ultimate rule of true (airspeed) VNE. But at any rate I agree this document could be expanded to clarify.... 'This is where you will place marks on the airspeed indicator - however see below for True Airspeed (actual current condition) flight limitations....
 
I have a Dynon D-10A,,

Since most (if not all) EFIS today show real-time TAS, I’m wondering if we can set an alarm, based solely on TAS and not IAS?

I’ll have to look over my manuals,,,

Edit:
Just reviewed the manual for the D10A,,
I don’t see TAS bugs/alerts as an option.

Maybe a collective request to Dynon in behalf of all of us dependent upon TAS redlines, to adopt TAS as an option
 
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I have a Dynon D-10A,,

Since most (if not all) EFIS today show real-time TAS, I’m wondering if we can set an alarm, based solely on TAS and not IAS?

I’ll have to look over my manuals,,,


On the G3X Touch system, you can set a 'TAS VNE'. This will bring the red/white 'barber pole' down on the airspeed indicator to match current TAS limit to the appropriate IAS.
 
I bet every airplane manufacturer has had this discussion about where to mark the for Indicated Airspeed. You want the best numbers. If you use 18,000 ft TAS, then the competition will eat your airspeed lunch cause they will use 8500 feet tas. The indicated airspeed will be faster and there goes the marketing. Descending from altitude say 17,000 ft which happens sometimes in RVs but probably not too often, Indicated airspeed is LOW and to the newbie, quite depressing. All the aircraft manufacture use IAS and they have a statement about corrections at altitude. Vans could do that too but I guess vans thinks it’s pilots are incapable of that maybe? Or maybe the marketing is so important that there is a resistant to revert to realistic IAS numbers. I don’t know but it has always bothered me that Vans departed from the industry standard by trying to go to TAS given that even today, people question it or don’t understand. On my twin, Mr Smith built an airframe that had lots of margins and the yellow area on the airspeed indicator is very small. I like margins. They make me happy happy happy.

I believe a case was made before to go back to the industry standard of realistic IAS indicator markings and leave the TAS in the manual. Maybe it’s time to revisit that effort.

You're right that most (all) certificated aircraft the the category of aircraft we fly have IAS markings and thats where we fly them up to their service ceiling. We've been trained to use the IAS limits as ultimate.

Just as a data point, the SR22T I fly on occasion has a placard listing 2 different IAS VNE values. One for below 18k and one for above 18k (you can guess that the one for 'above 18k', is a lower IAS VNE.)

With modern EFIS systems we can set VNE as TAS and it will modify redline on the altitude tape to reflect that. But, not all airplanes have a modern EFIS system....
 
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With modern EFIS systems we can set VNE as TAS and it will modify redline on the altitude tape to reflect that. But, not all airplanes have a modern EFIS system....

A call to Dynon confirmed that with the D10A, we are out of luck.
No such ability.

Skyview = yes

But I am not ready to ditch my D10A just yet,, so I will keep an eye (as I always do) on my real-time TAS readout.
 
I don’t think in this case the failure was about the IAS verses TAS issue. The aircraft was 44 knots above the IAS limit and this appears to be a low altitude event. It appears to be a very large over speed. Given the usual temps in NZ the last part of the event at 1700 feet IAS and TAS were probably almost the same.
G
 
In Switzerland, we must place a sticker in the cockpit with the text:

Vne: 200KIAS, minus 2kt per 1000ft altitude

This as a "rule of thumb" to prevent such bad cases.

For those with an EFIS that show Vne in TAS, the sticker is not needed.
 
Sobering

ZK-DVS, an RV-7 was involved in a fatal accident 2 years ago. The report has just been published by the NZ CAA, available in PDF format HERE.

Thanks for posting this, I called and talked to the investigator soon after this happened and sent them links to the other reports. It has taken a long time for this report to be issued.

The report leaves me wanting for information to definitively prove that the pilot failed before the aircraft. Was there an analysis or testing to show that the rudder flutters? Ever? Even in the other reports? There is no indication of such. There is a consistent failure mode here and it is hard to believe that RV7 pilots (regardless of experience) are more likely to overspeed than RV6 or RV8 pilots.

Reading accounts of this pilot being careful and conservative are consistent with my son's account of him when flying with him a few months before this accident. He certainly seemed to be a conservative pilot and was employed in an aviation job for Air Rescue NZ, as pilot and safety officer among other responsibilities.

I am going to have to read this for understanding about 5 more times.
 
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7?

Bill, are we up to 7 planes now? For some reason I thought we had 3 or 4.

Thanks for posting this, I called and talked to the investigator soon after this happened and sent them links to the other reports. It has taken a long time for this report to be issued.

The report leaves me wanting for information to definitively prove that the pilot failed before the aircraft. Was there an analysis or testing to show that the rudder flutters? Ever? Even in the other reports? There is no indication of such. There is a consistent failure mode here and it is hard to believe that 7 pilots (regardless of experience) are more likely to overspeed than 6 or 8 pilots.

Reading accounts of this pilot being careful and conservative are consistent with my son's account of him when flying with him a few months before this accident. He certainly seemed to be a conservative pilot and was employed in an aviation job for Air Rescue NZ, as pilot and safety officer among other responsibilities.

I am going to have to read this for understanding about 5 more times.
 
... it is hard to believe that 7 pilots (regardless of experience) are more likely to overspeed than 6 or 8 pilots.

For the most part, -6's and -8's have .020" rudder skins and folded trailing edges, and for the most part -7's have .016" rudder skins and riveted trailing edges. So perhaps the same number of people have overspeeded their -6 and -8 tails, and the effect of doing so is reduced because the design is less prone to failure (due to flutter or otherwise).
 
Bill, are we up to 7 planes now? For some reason I thought we had 3 or 4.

I was (now edited) talking about the RV models, but I think we are up to 5 lost. There is one that happened in AZ and did not get much attention, but when finally the report was available, the crash photos showed the empennage the familiar missing VS/rudder and the HS spar was failed. It had been about 12 months between events up to the NZ one, (Dean). I hope we don't see another anytime soon.
 
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By distinguishing the folded vs. riveted trailing edge, are you making indirect reference to the Kutta Condition?

No, I was only saying that maybe the folded trailing edge is less prone to flutter, I wasn't speculating why that might be the case. I hadn't considered the Kutta condition because I had forgotten about it, to be honest... :) I'll have to go back and review my aero texts...
 
I posted this a long time ago but I once took a hard look at the accidents stats. One of the interesting things I noticed was that I could not find a single incident of inflight structural failure on a RV6 despite at the time it having far more actual flight hours than other Vans models. The difference was striking compared to the RV7.
G
 
There is a difference in the mass/weight (w/o tips) and due to larger area and centroid of the respective rudders, paint (not insignificant) will aggravate the weight and movement of the CG farther from the pivot.

While these are facts, I have no idea if they are relevant to flutter, rudder failure or safety. More knowledgable people on this subject may know.

Screen Shot 2020-09-08 at 10.16.40 AM.png
 
I have basic understanding of flutter and did attend a session on flutter in one of the OSH forums years ago. I recall that improper control surface balancing can also play a role in flutter.

Can anybody comment on the proper methods for balancing Ailerons, Elevator and the Rudder after the plane is painted?

I have asked this question of builders as I walk the RV parking area and to my surprise a fair number said they did not balance the Rudder.
 
A call to Dynon confirmed that with the D10A, we are out of luck.
No such ability.

I don't buy that since we're talking software here. That they don't want to spend time on it because it's not economically good for them, even though it will be a lot safer for their clients? That I will agree.

Dynon says they support all of their equipment no matter how old but experience shows it not to be 100% true unless you are using a Skyview and up. Try calling or emailing for support on a D180 and I hope you aren't grounded somewhere or your hotel bill will be lengthy. You'll get better and faster support here on VAF.

It's sad to say it because I've been a Dynon cheerleader for many years but the truth is the truth.
 
I don’t think in this case the failure was about the IAS verses TAS issue. The aircraft was 44 knots above the IAS limit and this appears to be a low altitude event. It appears to be a very large over speed. Given the usual temps in NZ the last part of the event at 1700 feet IAS and TAS were probably almost the same.
G

So in this case the TAS vs IAS issue was not relevant. This is what I suspected. Vans list IAS because that is what most cockpits display. If you make the assumption that most rvs fly below a given max altitude (say 14,000 for arguments sake) and you base the vne in ias on that altitude then you are covered. If you have people going way above, with oxygen, then you have an issue. So there is all this discussion but I am not convinced there is an issue at all depending on what assumptions were made in converting that limit TAS to IAS. I suspect that for most of us, at the altitudes we fly, we are covered. Also there is a margin between VNE and the max demonstrated flutter speed which is another reason why Vans likely didnt feel there was a need to provide a TAS envelope.

Btw, the answer to this is NOT to install a stronger rudder! None of the airframe is cleared to these higher speeds. Beef up the rudder and something else will come off. This incident was an egregious violation of the poh. Had the pilot respected the IAS limits he would have been fine.

I think, and correct me if I’m wrong, that most of us who fly around at 10k ft and below and respect the IAS numbers have nothing to worry about.
 
nz accident

Btw, the answer to this is NOT to install a stronger rudder! None of the airframe is cleared to these higher speeds. Beef up the rudder and something else will come off. This incident was an egregious violation of the poh. Had the pilot respected the IAS limits he would have been fine.

The above is burying your head in the sand. Mistakes are made and accidents happen. You cannot prevent accidents by saying they are illegal.
 
The above is burying your head in the sand. Mistakes are made and accidents happen. You cannot prevent accidents by saying they are illegal.

Sorry but Scott is right.

You can’t keep adding strength to every component that fails when limits are clearly and significantly exceeded, otherwise our planes will end up too heavy to fly!

Skylor
 
The above is burying your head in the sand. Mistakes are made and accidents happen. You cannot prevent accidents by saying they are illegal.

Sorry, but there are some mistakes that you can make in any airplane that will kill you. If you want a completely “pilot-proof” airplane, you are going to be waiting for a very long time - as soon as the engineering community makes something fool-proof, nature creates a better fool.

I am all for making things as low risk as possible, but I have no idea how to eliminate all risk - and you DO have to expect that pilots will do their part in staying within reasonable limits. TAS vs. IAS is irrelevant in this discussion - going 44 knots over redline is simply not something one can expect to get away with without consequences.

The real lesson here is that if you are careless, you will break the airplane.
 
nz accident

Sorry, but there are some mistakes that you can make in any airplane that will kill you. If you want a completely “pilot-proof” airplane, you are going to be waiting for a very long time - as soon as the engineering community makes something fool-proof, nature creates a better fool.

I am all for making things as low risk as possible, but I have no idea how to eliminate all risk - and you DO have to expect that pilots will do their part in staying within reasonable limits. TAS vs. IAS is irrelevant in this discussion - going 44 knots over redline is simply not something one can expect to get away with without consequences.

The real lesson here is that if you are careless, you will break the airplane.

As a new person to experimental aviation, what I see is basically the wild west as far as limitations go. I read ads for the RV-6 with cruise speeds listed above the VNE and you see dual aerobatics in a 6 on you tube where you know they are not below the aerobatic wt of 1375. You have a poster stating that he checked for flutter in a 6 to 234 kts IAS. I read where Vans estimated the flutter speed of the 7 to be around 300kts

"The kit manufacturer had conducted flight testing of the RV-7A prototype. No indications of
flutter were encountered at a speed of 217 knots. Additional theoretical flutter analysis was
done where the flutter speed was calculated to be 300 knots for the baseline design. The
addition of weight, however, can decrease flutter speed by 50 knots or greater. Any imbalance,
such as paint and filler, which increases the weight of the rudder aft of the hinge line, has an
adverse effect on flutter speed."

I would guarantee that an equal number of 6 and 8 pilots have grossly exceeded VNE and still alive to tell or not to tell about it.

It would appear that some pilots may watch aerobatics on you tube and off they go. The one in NZ appeared to be an aileron roll that developed into an unusual attitude with no idea how to recover. All of these accidents appear to be aerobatic related.
 
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Vans list IAS because that is what most cockpits display....

I suspect that for most of us, at the altitudes we fly, we are covered. Also there is a margin between VNE and the max demonstrated flutter speed which is another reason why Vans likely didnt feel there was a need to provide a TAS envelope....
I think, and correct me if I’m wrong, that most of us who fly around at 10k ft and below and respect the IAS numbers have nothing to worry about.


Van’s says Vne is based on TAS. You might want to rethink “having nothing to worry about” at 10k and using IAS. Standard day at 10k, 200 KIAS = 243 KTAS.

Personally, I don’t go anywhere near 200 KTAS.
 
Van’s says Vne is based on TAS. You might want to rethink “having nothing to worry about” at 10k and using IAS. Standard day at 10k, 200 KIAS = 243 KTAS.

Personally, I don’t go anywhere near 200 KTAS.

Point taken but by my calcs,
Standard day, standard lapse rates,
At 10,000’
200KIAS = 229KTAS

ButI’ll check my work :)
 
A rough conversion from indicated miles per hour to true airspeed in knots is fairly easy for those of us in the Denver area (5,000' MSL).

As someone else mentioned in an earlier post, a rule of thumb is to add 2% for each 1,000' above sea level. Most of us in the Denver area routinely cruise around at 7,500'-ish MSL. At 2% per thousand, this means we have to add 15% to our indicated airspeed to arrive at true airspeed. It also just so happens that to convert miles per hour to knots, you add 15%.

So... around here, indicated airspeed in MPH is roughly equivalent to true airspeed in Knots. As an example, my RV-3 typically indicates about 175mph at 7,500'. This equates to a true airspeed of approximately 175kts. I have to be careful because my -3 can easily exceed Van's Vne in level flight. Gotta love excess performance!

Of course, in addition to my steam gauge airspeed indicator, I have a Dynon D10 set up to display in knots. It displays indicated airspeed as well as true airspeed, so the mental gymnastics aren't really required.

One of my pet peeves is when people don't know the difference between ground speed, indicated airspeed, and true airspeed, so whenever I'm asked to do a flight review, you can better bet that whoever I'm working with walks away with (if nothing else :) ) an understanding of airspeed!
 
View attachment 2212Keep in mind that TAS is based on density altitude. In the SE this summer I often see density altitudes approaching or exceeding 14,000 at 9500 to 11500 cruise altitudes.
 

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View attachment 2212Keep in mind that TAS is based on density altitude. In the SE this summer I often see density altitudes approaching or exceeding 14,000 at 9500 to 11500 cruise altitudes.

So you are 4 Kts over Vne in the pic, yet no red anywhere showing on your airspeed tape. Does the dynon allow you to configure Vne based on TAS?
 
So you are 4 Kts over Vne in the pic, yet no red anywhere showing on your airspeed tape. Does the dynon allow you to configure Vne based on TAS?


I am pretty darned sure that is in MPH not knots. It beats me why people use MPH when Knots is the industry standard.

And yes the Dynon Skyview / HDX allows you to select a IAS&TAS redline, so it will display red based on either.
 
So you are 4 Kts over Vne in the pic, yet no red anywhere showing on your airspeed tape. Does the dynon allow you to configure Vne based on TAS?

It’s knots and the VNE on a F1 is 240 knots. I have set the Dynon up to use 230 knots true to provide a margin beyond the design spec.
 
It beats me why people use MPH when Knots is the industry standard.
I can only speak for myself. Because until I went to a flying school to get my license, I had never flown in an airplane with Knots on the speedometer. Older aircraft (and I flew in a lot of them growing up) were not "standardized" on knots.

Also, MPH is faster. :)
 
Also, MPH is faster. :)

My RV-6 was set up for me to fly from the left and my Wife to fly from the right.

My side was set up for knots and her side for mph. Her side went faster but she had further to go, so we usually got there about the same time.
 
I imagine somebody of this experience would have been well aware of VNE limitations.
What concerns me is what caused him to get to excessive VNE speed and this report offers some hypothesis to why this may have happened but no actual conclusion.
All of those hypothesis are very valid and something I take seriously out of this report. For me IMC and aerobatic experience are another limitation.
 
"It would appear that some pilots may watch aerobatics on you tube and off they go. The one in NZ appeared to be an aileron roll that developed into an unusual attitude with no idea how to recover. All of these accidents appear to be aerobatic related."

This could have been one page.

MPH / KTS / TAS / lapse rates...

Appears the guy goofed up an acro maneuver. How many times have we read or summarized a roll that gets turned into a split S and an over G scenario. We need more acro schools. Would save more lives and airplanes.
 
I still don't understand why some are saying it was a botched aileron roll. The description doesn't sound like a roll and how can someone botch up a simple roll, aside from freezing and not completing it once they start it or they tried to do a super slow roll?

"The CAA said at about 12:16 local time, the RV-7′s EFIS recorded the aircraft in a steep 70-degree left bank with a nine-degree nose-down pitch. The airspeed was recorded as 148 knots. RV-7 aircraft are designed to be operated in both aerobatic and normal categories. After a short descent, the aircraft returned to its initial altitude of 4,500 feet. A minute later, the EFIS recorded that the aircraft had entered a 70-degree right bank with a nose-up pitch of 20 degrees, while the airspeed had dropped to 132 knots. A few seconds later the bank angle increased to 130 degrees with a 20-degree nose-down pitch.

At 12:17:13, the nose pitched down further to 60 degrees with the aircraft in an approximately 60-degree right-bank as the airspeed climbed to 183 knots. Six seconds later, the RV-7′s nose dropped to 30 degrees below the horizon as the airspeed rocketed to 244 knots. The RV-7′s never-exceed speed is approximately 200 knots. Four seconds later the aircraft rolled into a 40-degree right bank with a 30-degree nose-down pitch and an airspeed of 99 knots. "
 
I still don't understand why some are saying it was a botched aileron roll. The description doesn't sound like a roll and how can someone botch up a simple roll, aside from freezing and not completing it once they start it or they tried to do a super slow roll?
The "aside from" is *exactly* how they can botch up a "simple" roll, especially for someone who hasn't had much, or any, aerobatic training. It is *very* common for someone to ease off the stick deflection during their first roll, and end up with a roll rate near zero and inverted. When it doesn't look right, panic sets in, and the genetic programming in humans is to contract into a smaller space, which means hands come back towards the belly. Result? A split-S.
 
It is *very* common for someone to ease off the stick deflection during their first roll, and end up with a roll rate near zero and inverted.

Or simply fail to neutralize pitch input before making the roll input.

I'll suggest a caveat for the description of flight taken from the EFIS recording; the EFIS appears to have been set to record at five second intervals. A lot can happen between data captures, which are really just snapshots of events at a particular instant.

Morbid, yes, but if you really want your friends to know what happened to you, set your EFIS to record at not more than 1 second intervals.
 
Morbid, yes, but if you really want your friends to know what happened to you, set your EFIS to record at not more than 1 second intervals.

And have a camera recording everything inside. If it doesn't burn it could be recovered and explain a lot.
 
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