Ravin Aircraft down in Camperdown - 15 March 2014

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Calle_Hedberg
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Re: Ravin Aircraft down in Camperdown - 15 March 2014

Unread post by Calle_Hedberg » Mon Aug 21, 2017 2:12 pm

Hi

I think flutter was ruled out for this accident - no evidence of it. The main spar broke exactly where it can be expected to break in case of excessive (>8G) G loads.

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Re: Ravin Aircraft down in Camperdown - 15 March 2014

Unread post by Iceberg » Mon Aug 21, 2017 2:30 pm

Calle_Hedberg wrote:Hi

I think flutter was ruled out for this accident - no evidence of it. The main spar broke exactly where it can be expected to break in case of excessive (>8G) G loads.

Regards
calle
Calle, if you look back at the beginning of the thread it was reportedly flying straight and level when it broke. 8G load unlikely?

If the entire wing went into torsional oscillation (flutter) the maximum torsional moment would be at the root and it will break there in torsion - to the untrained eye the failure mode would be difficult to distinguish from a pure bending failure.
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Re: Ravin Aircraft down in Camperdown - 15 March 2014

Unread post by ddevos » Mon Aug 21, 2017 3:58 pm

Iceberg wrote:Calle, if you look back at the beginning of the thread it was reportedly flying straight and level when it broke. 8G load unlikely?

If the entire wing went into torsional oscillation (flutter) the maximum torsional moment would be at the root and it will break there in torsion - to the untrained eye the failure mode would be difficult to distinguish from a pure bending failure.
I thought I either read somewhere in this thread or heard someone say somewhere that there was indeed a pull-up...
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Re: Ravin Aircraft down in Camperdown - 15 March 2014

Unread post by Volo » Mon Aug 21, 2017 4:15 pm

I still put my money on PIO's . A single rapid movement @ or near VNE which it seems it might have been, by an untrained hand as in someone used to the soggy controls of a "tincan" and its allover .
By the third out of sinc cycle you wont get your arm up to control the aircraft . The loads at this point are anyone's guess but could easily take the wings off in a straight mainspar failure which appears to have been the case here . Calle's knowledge of the aircraft might confirm this ?
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Re: Ravin Aircraft down in Camperdown - 15 March 2014

Unread post by jimdavis » Mon Aug 21, 2017 4:21 pm

I seem to remember there was some previous damage to the aircraft (maybe the tailplane?). Anyone remember this?

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Re: Ravin Aircraft down in Camperdown - 15 March 2014

Unread post by Calle_Hedberg » Tue Aug 22, 2017 5:08 pm

Hi,

I'm not going to read through 27 pages of posts to see what's been said or not said, but it is clear that they were planning a high-speed fly-by so the start of this sequence was a dive at more or less full power. As far as I know, the pilot in the left seat (first time in a Ravin) had mostly experience with flying Piper Arrow aircraft (or something like that, which is much less sensitive in pitch at high speeds than the Comanche/Ravin). Remember that the Ravin control sensitivity by necessity will be a compromise, since the speed range goes from ~55KIAS (very mushy controls) to a Vne of 243KIAS (very sensitive). The aircraft had no damage history that I'm aware of.

The instructor in the right seat had more experience, of course, but my guess is that the upset might have happened to fast for him to react. I'm guessing here, but I've had many upsets (at slower speeds) due to moderate turbulence or wind-shear over the last 7 years of flying Troll Air - and it usually takes a second or two before you get your "wits back" when your intestines get displaced and your headset fly, if you get my drift.

I don't like using derogatory terms to describe pilot errors of various kinds, but many accidents are basically of the "should not have happened" type:
- It is not wise to put a new pilot on the controls of a high-performance aircraft and then almost immediately take it close to Vne for a fly-by (which they called the airfield on beforehand to announce).
- it is not smart to do a barrel roll 100ft above the runway, especially when you know you've lost up to 800ft in similar rolls at higher altitudes some weeks before (ref Potch Ravin accident)
- it is not smart to fly into thunderstorms, or do scud-running up mountain valleys, or a lot of other things SA pilots have done over the last few years (we have discussed most of them at length here at the Academy).

Anyway, I'm also a bit disappointed that the CAA takes so long to finalise and release the report. Even if they are unable to give decisive answers - as is the case with many accidents - I cannot see such answers becoming more likely as time goes by... Better to get a report out with "root cause unknown or uncertain" than to stuff it into a drawer.

I think the technical assessment done by that Engineer team from Potch (total mental curtain on their names now, but it's those guys who have designed a range of brilliant gliders) was completed 1.5 years ago. I do believe they ascertained that the main spar broke where expected when over-stressed, but I guess it would be very difficult for the engineers to ascertain the exact root sequence of events that lead to the over-stress, in the absence of video and/or EFIS logger data.

Video data made it far easier to nail down the root cause of the Potch accident - all experts reviewing the footage concluded it was a botched barrel roll at low level. So that report came out quickly.

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Re: Ravin Aircraft down in Camperdown - 15 March 2014

Unread post by mikev » Tue Aug 22, 2017 5:34 pm

I think the technical assessment done by that Engineer team from Potch (total mental curtain on their names now, but it's those guys who have designed a range of brilliant gliders) was completed 1.5 years ago. I do believe they ascertained that the main spar broke where expected when over-stressed, but I guess it would be very difficult for the engineers to ascertain the exact root sequence of events that lead to the over-stress, in the absence of video and/or EFIS logger data.
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Re: Ravin Aircraft down in Camperdown - 15 March 2014

Unread post by JoziFlyer » Sun Aug 27, 2017 10:39 pm

Calle_Hedberg wrote:
I think the technical assessment done by that Engineer team from Potch (total mental curtain on their names now, but it's those guys who have designed a range of brilliant gliders) was completed 1.5 years ago. I do believe they ascertained that the main spar broke where expected when over-stressed, but I guess it would be very difficult for the engineers to ascertain the exact root sequence of events that lead to the over-stress, in the absence of video and/or EFIS logger data.
Calle
When flutter occurs, does it not usually begin in a control surface? And if so, that control surface hinge would probably be the weak point and first to fail - long before a wing spar could be compromised?
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Re: Ravin Aircraft down in Camperdown - 15 March 2014

Unread post by jimdavis » Sun Aug 27, 2017 10:45 pm

JoziFlyer wrote:
When flutter occurs, does it not usually begin in a control surface? And if so, that control surface hinge would probably be the weak point and first to fail - long before a wing spar could be compromised?
Jozi, when flutter starts anything can go. I have seen photos of a glass aircraft where the skin simply delaminates and the wing just falls apart.

It is unbelievably violent.

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Re: Ravin Aircraft down in Camperdown - 15 March 2014

Unread post by JoziFlyer » Sun Aug 27, 2017 10:48 pm

jimdavis wrote:
Jozi, when flutter starts anything can go. I have seen photos of a glass aircraft where the skin simply delaminates and the wing just falls apart.

It is unbelievably violent.

Jim
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Re: Ravin Aircraft down in Camperdown - 15 March 2014

Unread post by Scaffel » Wed Jul 18, 2018 12:02 pm

Still no accident report?
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Re: Ravin Aircraft down in Camperdown - 15 March 2014

Unread post by airdale » Tue Jan 08, 2019 7:55 am

Do anybody know if this accident report was finalised?
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Re: Ravin Aircraft down in Camperdown - 15 March 2014

Unread post by cage » Tue Jan 08, 2019 10:31 am

airdale wrote:
Tue Jan 08, 2019 7:55 am
Do anybody know if this accident report was finalised?
If you mail the head of the accident dept at the CAA (can be found in the contacts page of caa.co.za).
Give them the date and the reg and they will send you what they have.
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Re: Ravin Aircraft down in Camperdown - 15 March 2014

Unread post by PRDT » Sun Sep 01, 2019 8:59 am

Accident Report

http://caa.co.za/Accidents%20and%20Inci ... s/9249.pdf

“Probable Cause

The pilot executed a typical high speed fly past manoeuvre along runway 15. During the pull-up from high speed flight at low level, the elevator trim tab separated with the elevator resulting in the elevator separating with the fuselage. During the in-flight break-up the left wing and right wing respectively separated with the fuselage prior to the aircraft impacting the ground.”

“It is probable that the aircraft was flown above VNE (243kt) when the pilot pulled up which led to the elevator trim tab separating with the elevator resulting in the separation of the elevator from the fuselage. During the in-flight break-up the left wing and right wing respectively separated with the fuselage prior to the aircraft impacting the ground.”
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Re: Ravin Aircraft down in Camperdown - 15 March 2014

Unread post by vindog » Sun Sep 01, 2019 2:04 pm

I witnessed this accident. There was no pull up.

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