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  #1  
Old 09-02-2020, 09:27 PM
KRviator's Avatar
KRviator KRviator is offline
 
Join Date: Oct 2009
Location: Sydney, Aust.
Posts: 822
Default RV-7A down in NZ 01/01/18 - Accident report released

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)
Quote:
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:
Quote:
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.
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First flight 26th March 2016. Essential specs 145KTAS @ 2400RPM, 8000', 24.2LPH, Initial RoC 1800FPM.
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  #2  
Old 09-02-2020, 11:07 PM
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jcarne jcarne is online now
 
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Default

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.
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  #3  
Old 09-02-2020, 11:34 PM
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grubbat grubbat is offline
 
Join Date: May 2012
Location: Ga
Posts: 676
Default 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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Last edited by grubbat : 09-02-2020 at 11:39 PM.
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  #4  
Old 09-03-2020, 08:09 AM
Capt Capt is offline
 
Join Date: Feb 2017
Location: Australia
Posts: 650
Default

Tragic and so unessesary
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!
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  #5  
Old 09-03-2020, 08:34 AM
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fl-mike fl-mike is online now
 
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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".
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  #6  
Old 09-03-2020, 08:44 AM
iwannarv iwannarv is offline
 
Join Date: Aug 2005
Location: Olathe, KS
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Default

Quote:
Originally Posted by RV8JD View Post
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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Last edited by iwannarv : 09-03-2020 at 08:49 AM.
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  #7  
Old 09-03-2020, 09:02 AM
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grubbat grubbat is offline
 
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Default 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.



Quote:
Originally Posted by iwannarv View Post
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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  #8  
Old 09-03-2020, 09:25 AM
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N184DA N184DA is offline
 
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Location: Tacoma, WA
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Default

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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Last edited by N184DA : 09-03-2020 at 09:33 AM. Reason: Additional research
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  #9  
Old 09-03-2020, 09:32 AM
iwannarv iwannarv is offline
 
Join Date: Aug 2005
Location: Olathe, KS
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Default

Quote:
Originally Posted by N184DA View Post
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.
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  #10  
Old 09-03-2020, 09:39 AM
iwannarv iwannarv is offline
 
Join Date: Aug 2005
Location: Olathe, KS
Posts: 431
Default

Quote:
Originally Posted by grubbat View Post
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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Never judge a man by his trim tabs.

Last edited by iwannarv : 09-03-2020 at 09:41 AM.
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