Facet Opel

Homebuilt Aircraft & Kit Plane Forum

Help Support Homebuilt Aircraft & Kit Plane Forum:

Mike W

Well-Known Member
Joined
Nov 3, 2012
Messages
103
Location
Doncaster Yorkshire UK
I recall there had been speculation about a change in the spar structure (cutting a hole for the oxygen bottle??) which severely degraded the capability of the spar to withstand G loads. The report referenced above indicated the wing was designed for 8G, but that may have been before a hole was cut in the spar. Is any of this speculation correct, or relevant to the loss of the aircraft?
Some time ago I attached a letter Jim Marske sent me from the co designer of the Opel in HBA, where he stated that the cause of the accident was the rear skid attached to the rear spar striking the ground and weakening it.
My plank is still progressing through it's flight testing. See video on YouTube.

MW9 Plank stability & control and handling qualities​

 

rotax618

Well-Known Member
Joined
Oct 31, 2005
Messages
1,649
Location
Evans Head Australia
When I witnessed the Opal take off, it seemed extremely pitch sensitive, I have no doubt that abrupt changes in pitch puts large loads onto the airframe (self induced turbulence). The actual cause of Scotts crash is only speculation but if you wish to emulate his design, I suggest that you consider pitch stability as a primary design goal.
 

Victor Bravo

Well-Known Member
Supporting Member
Joined
Jul 30, 2014
Messages
11,385
Location
KWHP, Los Angeles CA, USA
The accident report referenced above said the failure happed at somewhere near 100 knots. This is lower than the cross country speeds that it routinely achieved. Koen's own "100 Seconds" video indicates that it exceeded 150 knots. So it would seem to me that the wing would have failed while being flown at higher speeds and higher G loads before this flight. I am certain that it was a lot easier and more likely to have overloaded the airplane at those higher speeds, and that 100 knots would require a larger effort (or larger error) to cause the failure than 150 knots.

Rotax 618, do you mean the letter from the co-designer said the tailskid breaking the rear spar happened on the same flight as when the aircraft crashed? That would at least explain how it might have failed at far lower loads than previously experienced.
 
Last edited:

rotax618

Well-Known Member
Joined
Oct 31, 2005
Messages
1,649
Location
Evans Head Australia
Not being an eyewitness to the crash, I will not express an opinion as to the airspeed or manoeuvres being carried out at the time of the accident. At the time it was rumoured that Scott did a beat up over his relatives home to announce his arrival, whether that was hearsay or a rumour I am not able to say. My remarks about the pitch divergence characteristics was from first hand observation of flights I personally witnessed at Evans Head Aerodrome when Scott was making the record breaking flights.
 

Woodenwings

Well-Known Member
Joined
Aug 2, 2006
Messages
244
Location
Toronto
I was fortunate enough to witness Scott Winton fly the Facet Opal, and was a friend of his father, Col Winton. The Opal had pretty remarkable performance, but in my opinion was too pitch sensitive for the average pilot.
Planks do fly, some are more docile than others. If I were to design an unswept rectangular flying wing I would design for an AR of not more than 3.5, naturally if soaring performance is what you want a swept or Fauvel planform is best with a higher AR.
First hand stories are valuable. Cheers
 

Woodenwings

Well-Known Member
Joined
Aug 2, 2006
Messages
244
Location
Toronto
I saw a video on YouTube where eye witnesses and friends commiserate the final moments. There was something up with the rear spar and the engine attach location. I forget the details. It was an Aussie video.

Clearly the design has merit....but lacked refinement or gradual improvements over time that other designs benefit from.

Sigh
 
Top