Rudder Flutter

[FrenchyRV-6A]

Made structure repairs to horizontal stabilizer of RV-6A per Vans service bulletin and repositioned empennage forward 1 inch to comply with plans. Now encounter rudder flutter at 175 mph. Had never flown above 175 mph prior to repairs so don’t know if rudder flutter was already there, but ops manual has the published VNE. Called Vans and they had no other reports of rudder flutter. Any ideas?

[jcarne]

Wow I'm surprised they didn't hang up the phone when you mentioned the F word. I asked them for some moment numbers on the -7A rudder and that one got brushed under the rug.

P.S. Welcome aboard!

[FrenchyRV-6A]

Years ago, there was some discussion about the nosegear causing the tail to vibrate. Can’t find any info on it. Is it archived?

[rvbuilder2002]

Originally Posted by FrenchyRV-6A

Made structure repairs to horizontal stabilizer of RV-6A per Vans service bulletin and repositioned empennage forward 1 inch to comply with plans.

It would be helpful if you further explained “Repositioned empennage fwd 1 inch”.
To do this it would require major structural changes to the fuselage and/or emp attachment.

[David Paule]

Vne is not necessarily the number on the airspeed indicator. On RVs, it's true airspeed. Flying out of Colorado, the indicated airspeed will be lower than true airspeed, and that needs to be taken into account.

Also, it's not likely that you had full-fledged rudder flutter because you survived. Flutter is usually destructive, almost explosively so. Can you describe what happened and what the flight conditions were more thoroughly? Did the post-flight inspection reveal any damage?

Dave

[Kyle Boatright]

Originally Posted by FrenchyRV-6A

Made structure repairs to horizontal stabilizer of RV-6A per Vans service bulletin and repositioned empennage forward 1 inch to comply with plans. Now encounter rudder flutter at 175 mph. Had never flown above 175 mph prior to repairs so don’t know if rudder flutter was already there, but ops manual has the published VNE. Called Vans and they had no other reports of rudder flutter. Any ideas?

You repositioned the empennage forward by 1"? I'd love to see pictures of the before and after with the empennage fairing removed.

[scsmith]

Like others I am interested in what and why you did to the empennage.

But....


PLEASE....


MAKE SURE THE JAM NUTS ON THE ROD ENDS THAT FORM THE RUDDER HINGES ARE TIGHT. TIGHT.

[wjb]

Originally Posted by David Paule

Vne is not necessarily the number on the airspeed indicator. On RVs, it's true airspeed. Flying out of Colorado, the indicated airspeed will be lower than true airspeed, and that needs to be taken into account.

Hi Dave,

Is this right, TAS? Section 15 of the builders manual specifies Vne at 230 MPH IAS (200 kt IAS) for the -7

[plehrke]

Originally Posted by rvbuilder2002

It would be helpful if you further explained “Repositioned empennage fwd 1 inch”.
To do this it would require major structural changes to the fuselage and/or emp attachment.

And if doing so, most likely made tail not stiffly tied in and would make it very likely to have aero issue, or as OP described as “flutter”.

Why was the empennage moved forward 1”? I must have missed that in the SB.

[FLY6]

Had a buddy install a tail beacon x on his RV4 and when completed, had more what I would call, rudder oscillation during flight between the speeds of 140 to 160 knots. Reversed everything and still had the oscillation. Had another experienced builder look and they determined the rudder skin was flexing way too much. He put On 3 or 4 pieces of angle with 2 sided tape On each side of the rudder to see if that rectified the oscillation and it did. He ordered a new rudder from Vans. Not sure why it showed up after his work but it did. Not sure if Vans changed the thickness of their rudder skin but hopefully his new rudder will work flawlessly.