REFLECTOR: anyone know the story behind this-musthavemissedit..... [heur]

Tom Martino tmartino at troubleshooter.com
Wed Nov 9 07:41:36 CST 2005 

Have many winglets failed like this before?  Or worse have any departed
the aircraft?

Apparently, from what I'm reading ... winglets produce a lot of stress?

-----Original Message-----
From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of steve korney
Sent: Tuesday, November 08, 2005 9:43 PM
To: reflector at tvbf.org
Subject: RE: REFLECTOR: anyone know the story behind
this-musthavemissedit..... [heur]


Check out this web-site...Might shed a little more light on the subject
of 
Winglets..


http://www.mh-aerotools.de/airfoils/winglets.htm


Best... Steve



----Original Message Follows----
From: "Tom Martino" <tmartino at troubleshooter.com>
Reply-To: Velocity Aircraft Owners and Builders list
<reflector at tvbf.org>
To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org>
Subject: RE: REFLECTOR: anyone know the story behind 
this-musthavemissedit.....
Date: Tue, 8 Nov 2005 21:17:39 -0700

This is the best explanation I have heard for the stability of the
winglets.  Great job!

-----Original Message-----
From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Scott Baker
Sent: Tuesday, November 08, 2005 9:01 PM
To: Velocity Aircraft Owners and Builders list
Subject: Re: REFLECTOR: anyone know the story behind
this-musthavemissedit.....

Picture a sailboat with its bow pointing into the wind and the boom
trailing straight back (along the centerline of the boat).  This invites
a situation whereby the sails luff (i.e. flutter) because they lack wind
loading.  Tack the boat at an angle to the wind and the sails fill true,
because they are now (my word) "loaded".
Winglets on the Velocity are toed in.  The shape of the winglet is
actually a wing with the "top" or cambered side faces inboard; and the
bottom or flat side faces outboard.  Looking at the outside shape of the
winglet and rudder, one will notice a slight cuff (concave shape).
Builders sometimes mistakenly believe the concave area should be filled
in with micro in order to make a straight surface along the winglet and
rudder outside line.  Wrong.  The cuff is part of the "wing" shape and
is designed in this fashion for a purpose - and that is, to allow the
winglet to create lift in a horizontal direction towards the fuselage.
The winglet forces mimic that of a person pushing the winglet from the
outside towards the fuselage.  This "loads" the winglet and adds to
stability.  It also creates a design that does not support flutter.  It
is very important that builders who build from the basic kit make
absolutely sure that the toe-in of the winglets are built according to
the construction manual.  Straight winglets and the absence of a slight
concave line on the outside of the winglet invite flutter.  This is what
happened with Brendan and the first "Brazil" set of wings.  The toe-in
was reduced by a fraction of an inch and the shape of the outside of the
winglet did not feature a concave feature.  It was just enough to begin
winglet flutter, which once started - could not be stopped once the
rudder cables broke.
SB

	----- Original Message -----
	From: Greg Poole <mailto:gpoole at zeta.org.au>
	To: 'Velocity Aircraft Owners and Builders list'
<mailto:reflector at tvbf.org>
	Sent: Tuesday, November 08, 2005 8:15 PM
	Subject: RE: REFLECTOR: anyone know the story behind this-
musthavemissedit.....

	In a word; Wow!

	Knew all about the accident but never got to see the very
sobering picture of the aircraft afterwards (thanks Alex!) or the detail
provided below by Scott (thanks mate!). Would like to know a little more
how streamlining invites flutter - or do you mean that the bulk of the
wings/winglets were reduced to a point that structural rigidity was
lost?

	Yes...now that I have seen it thank God again that Brendan made
it out OK!

	....You all be careful out there now!

	Greg in Sydney.
	Std RG E.

	-----Original Message-----
	From: reflector-bounces at tvbf.org
[mailto:reflector-bounces at tvbf.org] On Behalf Of Scott Baker
	Sent: Wednesday, 9 November 2005 10:20 AM
	To: Velocity Aircraft Owners and Builders list
	Subject: Re: REFLECTOR: anyone know the story behind this- must
havemissedit.....

	Yes, I know all about it.
	The aircraft pictured belonged to Bob Wood.  It is a fixed gear
Velocity XL and it featured the first "Brazil" wing.  Brendan O'Riordan
was the pilot.  The aircraft developed a flutter in the right vertical
stabilizer immediately after the aircraft was leveled off following the
first take off; estimated speed 110 knots.  Brendan attempted to slow
the aircraft by reducing power - and at the same time deployed both
rudders.  Deploying the rudder "loads" the winglet to help reduce the
possibility of flutter.  The flutter action was so violent that it broke
the rudder cables and the right rudder was torn from its hinges.  The
aircraft became almost uncontrollable at that point.  Brendan added air
speed by lowering the pitch attitude and headed to a sparsely populated
area West of Sebastian Airport.  The aircraft struck the ground at
approximately 90 knots, hitting Palmetto trees and ultimately flipping
the aircraft inverted before it came to a stop.  Brendan, thank God, was
okay.  He was released from the local hospital emergency room after a
quick examination - but as you can see in the photo, Bob's aircraft was
a total loss.
	The designer of the wings, Dan Maher, and other aeronautical
engineers were consulted.  The winglet and rudder design were found to
be too streamline that it invited flutter.  The winglets and rudders
were redesigned and flight tested on the factory's XL training aircraft.
Important: Everyone who has a "Brazil" wing has the new wing design,
which was thoroughly and professionally flight tested to 210 knots
without any hint of flutter.
	Velocity built Bob Wood a second aircraft, aka "Bob-II".
	The bottom line is that the first "Brazil" wing had a design
problem, it resulted in a forced (crash) landing, Brendan escaped
injury, all of the old winglets and rudders were destroyed, new winglets
and rudders were designed and professionally flight tested in excess of
normal flight limits, Bob Wood was satisfied with a replacement aircraft
, new "Brazil" wings are performing great... and life goes on!
	Reports of this were published on the Reflector years ago when
the accident occurred.  Many "Reflectorites" were at the Velocity Open
House when the accident occurred.
	Hope this helps.
	Best regards,
	Scott B.



		----- Original Message -----
		From: Alex Balic <mailto:alex157 at pwhome.com>
		To: reflector at awpi.com
		Sent: Tuesday, November 08, 2005 5:36 PM
		Subject: REFLECTOR: anyone know the story behind this-
must have missedit.....

		Saw this in the builder site, don't remember about it
other than the one time that there was a flutter problem with the
original Brazilian wings- is this the aftermath?
http://www.tvbf.org/gallery/?display=.%2Fincidents%2FBrazilian%20wing%2F
bob_1_1.jpg


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