Excelleron 50 Horizontal Tail Flutter
11-14-2005 | 09:54 PM
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From: Brisbane, AUSTRALIA
Excelleron 50 Horizontal Tail Flutter
Hi,
Has anyone out there experienced horizontal stabiliser flutter on the Exelleron 50 airplane?
Yesterday I experienced horizontal stabiliser flutter, and I still have the aircraft to tell the tale. This occurred on flight number six.
However, the story goes back to last week, when I did the post-flight inspection of the Excelleron after 3 flights. I discovered that the horizontal stab failed (broke) cleanly along the centre-line, and the only thing holding it in was the epoxied attachment to the fuselage sides. I noted at the time that the tail seemed a bit flimsy and the first three flights were accompanied by a buzzing sound from the airframe. However I repaired this and proof loaded it to a 12g tail balance load. On the next flight I experienced flutter of the tail whilst at about 30 ft and about 100km/hr (occurred right in front of me). I managed to recover the aircraft intact (by miracle) to do an inspection. The forward and aft spars had broken symmetrically (both LH and RH side) and snapped the elevator pushrod out of the servo arm. I have attached some photos of the horizontal stab with the covering cut away showing this spar damage.
The elevator gaps were sealed and the control linkages had very little or no backlash or slop.
Regards
Waz
PS. I have rebuilt the tail, and after a dozen flights I have yet to experience flutter
Has anyone out there experienced horizontal stabiliser flutter on the Exelleron 50 airplane?
Yesterday I experienced horizontal stabiliser flutter, and I still have the aircraft to tell the tale. This occurred on flight number six.
However, the story goes back to last week, when I did the post-flight inspection of the Excelleron after 3 flights. I discovered that the horizontal stab failed (broke) cleanly along the centre-line, and the only thing holding it in was the epoxied attachment to the fuselage sides. I noted at the time that the tail seemed a bit flimsy and the first three flights were accompanied by a buzzing sound from the airframe. However I repaired this and proof loaded it to a 12g tail balance load. On the next flight I experienced flutter of the tail whilst at about 30 ft and about 100km/hr (occurred right in front of me). I managed to recover the aircraft intact (by miracle) to do an inspection. The forward and aft spars had broken symmetrically (both LH and RH side) and snapped the elevator pushrod out of the servo arm. I have attached some photos of the horizontal stab with the covering cut away showing this spar damage.
The elevator gaps were sealed and the control linkages had very little or no backlash or slop.
Regards
Waz
PS. I have rebuilt the tail, and after a dozen flights I have yet to experience flutter
11-14-2005 | 11:51 PM
#2
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RE: Excelleron 50 Horizontal Tail Flutter
I'm no expert with pattern planes, but two things stand out to me. One, those rib notches look really deep, almost halfway through the leading edge. And two, the TE break right in front of the horn along with the pushrod being forced out of the servo arm leads me to wonder if counterbalancing the elevator would take some stress off the linkage setup.
Could be that forces on the elevator prevented the pushrod from moving and the resulting compression between the horn and the arm snapped the TE and popped out the pushrod and then the LE broke at its weakest point being the rib notch as a result.
Could be that forces on the elevator prevented the pushrod from moving and the resulting compression between the horn and the arm snapped the TE and popped out the pushrod and then the LE broke at its weakest point being the rib notch as a result.
11-23-2005 | 08:51 PM
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From: Brisbane, AUSTRALIA
RE: Excelleron 50 Horizontal Tail Flutter
I've just realised that you guys might not have seen the Excelleron 50. The model is relatively new and it seems that I have been doing some product testing without knowing it.
And yes the rib slots in the forward spar would reduce the strength in bending as well.
I'd be interested what the horizontal stab internals in the Excelleron 90 are like, noting that this model seems to be very popular.
I'd like to try the Excelleron 90, but I guess T've been tainted somewhat with the build quality of the 50 version.
Woxman
And yes the rib slots in the forward spar would reduce the strength in bending as well.
I'd be interested what the horizontal stab internals in the Excelleron 90 are like, noting that this model seems to be very popular.
I'd like to try the Excelleron 90, but I guess T've been tainted somewhat with the build quality of the 50 version.
Woxman
11-23-2005 | 10:26 PM
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From: Tomball,
TX
RE: Excelleron 50 Horizontal Tail Flutter
My Dad has hundreds (if not thousands) of flights on his Excelleron 50. It is not as new as you might think...He's had his flying on a Saito 72 over a year.
He used CF dual elevator pushrods (commonly referred to as DEPS these days) on his and has had no signs of weakness in the tail at all. He cut out the bottom of the fuse to install and glued the part back in. This linkage is as positive as you can get. Zero flex, Zero slop
I might suggest that the damage you see in the stab on yours is the result of elevator flutter if you used the supplied linkages. The ones in the box were some of the poorest material I've ever encountered. Very soft and flexible with very bad geometry required to make it work at the rear exit locations.
Overall, the construction of this ARF was much better than average. I was imppressed with the small details in the fuse construction that we were able to see when the bottom was opened up.
This plane flies really good for such a small plane. He even has a second one in the box waiting for the first one to expire
Richard
He used CF dual elevator pushrods (commonly referred to as DEPS these days) on his and has had no signs of weakness in the tail at all. He cut out the bottom of the fuse to install and glued the part back in. This linkage is as positive as you can get. Zero flex, Zero slop
I might suggest that the damage you see in the stab on yours is the result of elevator flutter if you used the supplied linkages. The ones in the box were some of the poorest material I've ever encountered. Very soft and flexible with very bad geometry required to make it work at the rear exit locations.
Overall, the construction of this ARF was much better than average. I was imppressed with the small details in the fuse construction that we were able to see when the bottom was opened up.
This plane flies really good for such a small plane. He even has a second one in the box waiting for the first one to expire
Richard
11-24-2005 | 09:34 AM
#5
My Feedback: (1)
RE: Excelleron 50 Horizontal Tail Flutter
Woxman:
I just competed my Excelleron 90 and found it to be pretty much a by-the-book build. I am new to Pattern, built and flew a GP Venus 40. The only issue I had with the 90 was that it was my first experience with pull-pull cable system. On this model, both the rudder and elevator are pull-pull. The build was careful and deliberate througout the process and I finally found that the pull-pull was not as difficult as I had originally imagined.
I have not yet flown it, just got some of the finishing touches done before having to leave for a flight north for the holiday weekend. But, I intend to go through a complete pre-flight with the 'club pro' then put it up for it's maiden.
DS.
I just competed my Excelleron 90 and found it to be pretty much a by-the-book build. I am new to Pattern, built and flew a GP Venus 40. The only issue I had with the 90 was that it was my first experience with pull-pull cable system. On this model, both the rudder and elevator are pull-pull. The build was careful and deliberate througout the process and I finally found that the pull-pull was not as difficult as I had originally imagined.
I have not yet flown it, just got some of the finishing touches done before having to leave for a flight north for the holiday weekend. But, I intend to go through a complete pre-flight with the 'club pro' then put it up for it's maiden.
DS.
