VL3 Sprint / Flamingo

[Spin]

I've just heard that a VL-3 Sprint, sold in South Africa as the Flamingo suffered an in flight break up and crashed over the weekend, killing the pilot and passenger.

 

The aircraft, a sleek looking composite retractable, powered by a 100hp Rotax, may not even be sold in Australia for all I know, but the lessons that are already coming out of this accident are well worth pondering.

 

The plane and crew were competing in the annual Presidents Trophy Air Race and were observed in a shallow decent from high ground to low, heading for one of the turning points that has to be rounded at between 200 and 300 feet agl. From what eye witnesses have said, it seems the wings separated from the fuselage, in flight and were severely damaged - torn apart is one description I heard. Flutter is the obvious conclusion, but why it occurred remains to be seen.

 

Now I may be the only idiot that missed that page in the book, but I always understood that VNE was an IAS number ie. redline on the asi was an absolute, however I am now told that this is not necessarily so and particularly composite manufacturers, sometimes reflect VNE as a TAS figure. VNE on this particular aircraft is shown as either 162 kts or 183 kts on the various agents and manufacturers websites, however max speed in level flight is already 145kts, so it doesn't take much imagination to see that in a competitive situation with the throttle against the dash, the aircraft could exceed VNE relatively easily in a dive.

 

For me two things stand out - 1. know your aircraft's limits as set out in the manual ( and understand what they represent), and

 

2. coloured bands on the asi aren't there to make it pretty, they represent safe limits, determined by whatever testing the manufacturer has done. Exceed them by any margin and you just joined the test pilot program.

 

 

[Spin]

Found a photo of the aircraft, source as indicated on the image.

 

 

 

[Tomo]

however I am now told that this is not necessarily so and particularly composite manufacturers, sometimes reflect VNE as a TAS figure.

I've never heard this before, but thinking about it now, TAS would be faster than IAS if you take air density/altitude into the equation.

 

 

[Spin]

Yep that's it, not normally a huge spread at the sort of altitudes we fly at, but get up high and it can make quite a difference

 

 

[PapaFox]

An easy approximation for TAS is to add 2% of IAS for every 1000ft above MSL

 

 

[Mc Guyver]

I have copied from another egroup

 

Erika Gibson, Beeld

 

Johannesburg - Two participants in the President's Trophy Air Race in Bela Bela in Limpopo on Saturday died when their plane appeared to break into pieces in the air.

 

Both wings of the Flamingo two-seater plane "fluttered like feathers" while the fuselage fell straight to the ground, said Tertius Myburgh, who flew right behind the Flamingo in his own plane.

 

Werner Blignaut, a commercial pilot for Naturelink at Wonderboom Airport in Pretoria, and Cronjé Erasmus, his navigator, who was also a flight instructor at SFT flight school at the Kitty Hawk air field outside Pretoria, died in the accident.

 

The air race has been held since 1937 and Saturday's accident was the first fatal incident since its inception.

 

Like confetti

 

According to Myburgh, Saturday's part of the race was from Rustenburg to Bela Bela and back.

 

They were flying straight towards the turning point at Bela Bela when he saw only the white of the plane's wings "unfold".

 

"It looked like feathers floating around and afterwards some of the stuff that the plane was made of, blew through the air like confetti.

 

"I said to my co-pilot: 'Look, that plane is breaking up.' But it was so unreal that I wondered if it hadn't perhaps been a whirlwind.

 

"The next moment we were above the turning point and no one said anything over the radio. But right after, the message did come through and then I knew that I hadn't imagined it."

 

Mechanical problem

 

Chris Briers, who had been on standby with his helicopter in Bela Bela - and who up until last week would have taken part in the race himself - said everything pointed to something having gone wrong mechanically.

 

"The air race's safety standards are very high. Something like this could probably have happened anywhere. A pilot is powerless when something goes wrong with his plane. It was coincidental that they were busy with the air race when the accident happened."

 

According to Briers, who rushed to the accident scene, pieces of the wing lay over 100m from the plane's fuselage.

 

He said Flamingo planes were built in Brits and were the ideal planes for races like these.

 

The ill-fated plane was only nine months old.

 

Jannie de Klerk of Naturelink said on Sunday that Blignaut had been a first officer in Embraer 120 planes in the Air Force and would have been made a captain soon. He was engaged to Sharon Badenhorst.

 

Erasmus had become a father two months ago, with the birth of his daughter.

 

The Aero Club of South Africa, the organiser of the air race, refused to comment on Sunday.

 

 

[Bruce Robbins]

VNE is one of the few speeds that is usually quoted in TAS. Check your individual POH.

 

The Pipistrel Virus actually has a table on the dash showing different VNE speeds (Indicated)for different heights. The higher you go, the lower the indicated VNE gets.

 

The main reason is that VNE is usually set by flutter constraints, and flutter does not care about IAS, just the speed of the air past the surface.

 

 

[Spin]

Bruce I'm not sure that I agree with "usually indicated as TAS". It is certainly true where flutter is the limiting factor, which I understand is a characteristic of many composite designs, but so far the aircraft I have flown (more traditional types), express it as IAS or don't clearly define it as either. I am glad to hear that the Virus displays the various speeds on the dash, rather than burying them in the POH.

 

Whichever it may be though, my intention was to highlight the possibility that it may be something other than the obvious redline speed on your asi. The second intention was to point out that VNE, like other limits on aircraft aren't advisory. Sure there is a safety margin built in, but just how big that margin is we don't know. Also bear in mind that aging materials, repairs and minor mis-rigging can all erode that margin, resulting in a very bad day as these two aviators found. RIP

 

 

[Bruce Robbins]

Bruce I'm not sure that I agree with "usually indicated as TAS". It is certainly true where flutter is the limiting factor, which I understand is a characteristic of many composite designs, but so far the aircraft I have flown (more traditional types), express it as IAS or don't clearly define it as either.

 

Hi Spin,

 

VNE is a complex limitation that I shouldn't have tried to summarise in one short sentence. The point I was trying to make was that of all the speed limitations that we fly within, VNE is the one that is more likely to be a function of TAS rather than indicated.

 

However, most light aircraft GA or RA, tin or plastic, only have a IAS indicator, so it makes sense that the redline or VNE should be marked on this. That doesn't mean that we can happily approach redline on the IAS indicator with impunity. Fortunately below 10,000 feet it's not so much of an issue, but after much reading on this subject I've decided that I will always view VNE as TAS.

 

Stick IAS TAS and VNE into a search engine and have fun wading through the results. :)

 

 

[Spin]

You know I'm really not sure what we're arguing about:question:, suffice to say it's something that pilots would do well to pay close attention to.

 

 

[John Brandon]

I think it may be worthwhile to review http://www.raa.asn.au/safety/excess_speed2.html

 

cheers

 

John Brandon

 

 

[slartibartfast]

Love your work John.

 

 

[Spin]

Thanks for posting that John, I have been doing quite a bit of reading since hearing about the incident and the RA Aus document has to be the most concise and intelligible source I have seen so far.

 

 

[dazza 38]

Same here Thanks john,a good read.

 

 

[Guest Darrell Lush]

Just an update on this terrible tragedy and to clear up some inaccuracies that have transpired. The Vne of the aircraft was reduced to 142 knots IAS as per a technical bulletin issued by the manufacturer. This reduction was a safety measure to address an unrelated tail surface vibration that occurred in flight. The accident investigation has been reopened because I have shown that the investigation report was nothing more than a copy/pasted version of the unqualified opinion of a race official. Unfortunately this official made serious errors when calculating the aircraft's speed. The aircraft, as are all participating aircraft, was fitted with a GPS/logger which logged a ground speed. The wind vectors were simply deducted from this groundspeed and the resultant was assumed to be a TAS without correcting for temp/altitude. The Vne is also expressed as an IAS and the official erroneously assumed the Vne to be expressed as a TAS. The reasons for these and other blatant errors which were in the report are now the subject of an internal CAA forensic investigation which I am assisting in conducting. A vital report on the dynamics of the wing spar failure was omitted from the final accident report. I have had a cursory view of this report and to me it indicates that the wing spar failure occurred as a result of an impact and not a flutter related failure. The report also omits the fact that the canopy was first to fail. The wreckage trail confirms this. The pilot had also mentioned that the canopy's plexiglass was denting inwards a few weeks prior to the accident. An STC was issued to retrofit an extra latch on the canopy to make it more secure, but this installation was never conducted.

 

In summary, the pilot never exceeded Vne. I have recalculated the speeds to determine the approximate IAS and have found that the average speed flown by the pilot was approximately 135 - 139 knots. I am posting this to warn other "Flamingo" owners to check the integrity of their canopies in order to prevent another tragic recurrence. The report appears to be a concocted, manipulated version of the facts, designed to protect specific entities from liability.