Ravin Aircraft down in Camperdown - 15 March 2014

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

Unread post by nrm » Sat Sep 07, 2019 10:01 am

jimdavis wrote:
Fri Sep 06, 2019 4:13 pm
nrm wrote:
Fri Sep 06, 2019 2:04 pm
He did not do a sudden pull up. That is according to eye witnesses, experienced pilots.
Nev, I suggest that the eye-witness not seeing it, doesn't mean it didn't happen. I imagine it could happen in the blink of an eye and that it wouldn't necessarily involve a noticeable pitch. I am sure Stressors will be able to shed light on how quickly breakup sequence could happen. Would one necessarily observe a noticeable pitch up before everything came apart?

jim
The eyewitness I was referring to is an experienced instructor. The rudder trim tab was recovered in the school grounds a long way from where the aircraft began to disintegrate
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Re: Ravin Aircraft down in Camperdown - 15 March 2014

Unread post by Dragon » Sat Sep 07, 2019 12:14 pm

jimdavis wrote:
Fri Sep 06, 2019 4:13 pm
nrm wrote:
Fri Sep 06, 2019 2:04 pm
He did not do a sudden pull up. That is according to eye witnesses, experienced pilots.
Nev, I suggest that the eye-witness not seeing it, doesn't mean it didn't happen. I imagine it could happen in the blink of an eye and that it wouldn't necessarily involve a noticeable pitch. I am sure Stressors will be able to shed light on how quickly breakup sequence could happen. Would one necessarily observe a noticeable pitch up before everything came apart?

jim
“Snap” Jim, I think we were typing and posted at the same time but I merely duplicated your post without realizing it. I agree with you re fuel and explosion, but I didn’t look into it, I was just searching for a clip that illustrated our point. If I had had the time I would indeed have looked into it deeper to check it was thoroughly relevant so I hope it is, if not, I hope people get the gist of it.
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Re: Ravin Aircraft down in Camperdown - 15 March 2014

Unread post by vindog » Wed Sep 11, 2019 9:14 am

For clarity, the Raven was on a very shallow descent prior to the accident. There was a minor correction in direction to line up in the extended center line of the runway 15 Emoyeni (very slight left turn then once aligned a slight right turn to be on the center line). The level off was very gentle and smooth.The left wing departed as they leveled off for the flyby at about 400 meters before the threshold. .The right wing departed immediately thereafter. The engine sounded like it was at full power and like the prop was on a fine setting. These are the memories of what we saw on that sad day.
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Re: Ravin Aircraft down in Camperdown - 15 March 2014

Unread post by bear » Fri Sep 13, 2019 5:25 pm

Ignoring the mechanical issues, which Stressmerchant has elaborated on (as always most thoroughly, thanks M), a comment on the human side of things:
Nobody calls ahead saying they going to do a flypast, then starts the maneuver with a shallow dive, making small corrections to the line up, then initiates a high-g pull up 400m (miles away figuratively speaking) from the threshhold. Nobody. My money is on flutter, especially with the buzz heard by the eyewitness, and that some bits of the rudder were found far from the rest of the debris.

A flutter analysis is all good and well, but does not define that aircraft, on that day.
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Re: Ravin Aircraft down in Camperdown - 15 March 2014

Unread post by Calle_Hedberg » Fri Sep 13, 2019 10:59 pm

Hi,

I'm obviously just a normal pilot with negligible knowledge about materials, load testing etc, but Stressmerchant's initial observation resonates with me:
"In my opinion, after reading this report, I get the impression that the cause was not really determined with any real certainty. Blaming the pilots is the easiest path since they are not around to defend themselves. Given the various potential scenarios, the probabilities may favour a pilot error, but I think that the report is not conclusive evidence of this. I would like to have seen a statement to the effect that even though the most likely scenario was an error by the pilot, the cause could not be conclusively proven."

Although there might be small differences in the rigging of different aircraft, my own Ravin 500 is generally flown with negligible elevator tab trimming - the only exception being on final at speeds well under 100kts (by negligible tab trimming I mean that the elevator tab is more or less exactly in line with the elevator or "neutral". I always set it back to neutral before take-off. In my lay person's understanding, that would mean relatively less force on the tab and less chance of something breaking even under speeds close to Vne.

At the same time, it is a FACT that one observer observed "a piece coming off" and that the elevator was found a considerable distance away - at least indicating that the accident sequence hit the elevator before the wings.

I've stated before on this thread that I've flown my Ravin close to Vne a few times - it does not take long to reach 230+ kts when descending at 500-1,000fpm at full power - and then eased it out of the dive with no problems. But while it does not take long, it's not extremely rapid either - I never had problems monitoring both the outside and the instruments during those dives, and obviously kept a very sharp eye on the ASI (of which I have several). I would start easing it out of the dive at around 225 kts, if my memory serves me right (reaching a max of ~235 or so).

So I too find it hard to believe that the pilot would deliberately exceed Vne, showing off or not. I recall several similar discussions from past accidents, including the Flamingo accident at the 2010 PTAR - where investigators regarded exceeding Vne as probable while others, based on familiarity with the pilot, regarded that as unlikely.

I don't know the pilot here at all, but my skepticism is more based on the nearly 50kts difference between max straight and level speed at full power and Vne for the Ravin. That's a large buffer - especially when compared with the Flamingo, which had a very small buffer between max straight and level speed and Vne. The larger the buffer, the less likely you would (at least accidentally), exceed Vne, IMHO.

(That said - it was equally astonishing for me to see the Potch barrel roll accident (and the Albatrosses scud running out of Tzaneen, and...). So I guess we just have to accept that no matter how many hours and how much experience pilots have - sometimes they just wander off the reservation and into the killing fields..)

In any case, I agree with Stressmerchant that the accident report could have stated that the cause could not be CONCLUSIVELY proven.

The learning aspects of this are the same old, same old:
- you can do an impressive fly-by WITHOUT going close to Vne
- you can do an impressive fly-by WITHOUT barrel rolls, pull-ups or other dangerous low-level maneuvers
and if some hangar cowboy afterwards sneer at you, then use that right hand finger...

I would even argue that doing a fly-by a lot slower, with some maneuvering, might actually be a more interesting fly-by for spectators than a high-speed one. I talked to a relative a few days ago, who has a mountain cottage high up in a valley flowing into one the fjords in Western Norway. He told me that when I overflew the cottage back in 2015, coming down the valley at 200+ kts, it was so fast that he didn't even managed to snap a photo... That brought home to me the above truth: we have been conditioned to regard high speed as the best way to impress those on the ground, and I'm no better than most other pilots in that regard (BUT next time I overfly somebody's house, I'll do it nice and slow with a bit of wig-waging and maybe an orbit - to give them a chance to really SEE the aircraft 8) )

Best regards
Calle
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Re: Ravin Aircraft down in Camperdown - 15 March 2014

Unread post by Ugly Duckling » Fri Sep 13, 2019 11:10 pm

I recall Scully putting the Ravin through it's paces at Potch in the early 2000s. Sweetly flown to show the capabilities of the "fantastic plastic "
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Re: Ravin Aircraft down in Camperdown - 15 March 2014

Unread post by Calle_Hedberg » Sat Sep 14, 2019 12:18 am

Ugly Duckling wrote:
Fri Sep 13, 2019 11:10 pm
I recall Scully putting the Ravin through it's paces at Potch in the early 2000s. Sweetly flown to show the capabilities of the "fantastic plastic "
And when the same Scully showed me how to do pylon racing a few years ago, he mentioned that during that performance he generally never went beyond 150-160 KIAS. Which again just underscores the point that while speed might be a very important factor when it comes to car racing, it's less so with aerial displays...

Regards
Calle
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