Narrative:

I have been doing aerobatics in my 1973 decathlon since 1981. After doing most of my routine at altitude, I snapped inverted and proceeded to do a split south after my airspeed bled down to about 50. As I pulled back on the stick at the conclusion of the maneuver, I realized I had no back elevator. I moved it back and forth in an attempt to get back some control. At this point I was pointed 20 degrees below the horizon. I checked to see if the rear passenger stick was stuck. There is a well known airworthiness directive concerning the rear stick being caught in the front seatbelt. That wasn't the problem. The stick had somehow moved while I was inverted to get caught under the pilot's seat back cover. I was unable to dislodge it strapped tight into my seat, so I had to unstrap myself, bend over the seat, and rip the seat cover away. I was sure this would solve the problem. It didn't. The controls were still frozen. I remembered about using the trim in sits like this, and I was barely able to bring the plane up from its 20-30 degree dive. I eventually landed at my home airport. I was unable to flare on landing and basically did a real 3 point landing. I taxied to the local FBO and checked to see if there was anything restricting the controls which became loose after I stopped the aircraft. They found a metal camera bracket wedged into the controls. It must have fallen out of my pocket and somehow got into the stick boot which was fairly new and opened only at its apex where the stick came out. It amazed me that 2 separate problems occurred at the same time, both restricting my elevator control. Callback conversation with reporter revealed the following information: reporter stated that the front seat cover was an after market item which did not have snaps on the bottom to hold it down. Reporter advised that he has installed a strap on the seat cover to hold it down and prevent possible interference with the aft stick. Reporter stated that the rear cockpit stick boot is also a non factory item and fits loosely around the stick. Reporter stated that he has secured the top of the boot better and no longer carries loose items when doing aerobatics. Reporter advised that the item that fell into the stick boot was a camera tripod bracket that was approximately 1.5 inches square. Reporter stated that the elevator jammed in the neutral position, that the aircraft was not inverted, and that he used 'up' trim to recover from the nose down attitude. Analyst questions the possibility of this action as the citabria elevator trim is a tab system which would require opposite control when flying the aircraft with the trim only.

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Original NASA ASRS Text

Title: CH7A PLT EXPERIENCES A JAMMED ELEVATOR DURING AEROBATIC MANEUVERING DUE TO AFT CTL STICK INTERFERENCE WITH THE FORWARD SEAT AND A FOREIGN OBJECT LODGED IN THE CTL SYS.

Narrative: I HAVE BEEN DOING AEROBATICS IN MY 1973 DECATHLON SINCE 1981. AFTER DOING MOST OF MY ROUTINE AT ALT, I SNAPPED INVERTED AND PROCEEDED TO DO A SPLIT S AFTER MY AIRSPD BLED DOWN TO ABOUT 50. AS I PULLED BACK ON THE STICK AT THE CONCLUSION OF THE MANEUVER, I REALIZED I HAD NO BACK ELEVATOR. I MOVED IT BACK AND FORTH IN AN ATTEMPT TO GET BACK SOME CTL. AT THIS POINT I WAS POINTED 20 DEGS BELOW THE HORIZON. I CHKED TO SEE IF THE REAR PAX STICK WAS STUCK. THERE IS A WELL KNOWN AIRWORTHINESS DIRECTIVE CONCERNING THE REAR STICK BEING CAUGHT IN THE FRONT SEATBELT. THAT WASN'T THE PROB. THE STICK HAD SOMEHOW MOVED WHILE I WAS INVERTED TO GET CAUGHT UNDER THE PLT'S SEAT BACK COVER. I WAS UNABLE TO DISLODGE IT STRAPPED TIGHT INTO MY SEAT, SO I HAD TO UNSTRAP MYSELF, BEND OVER THE SEAT, AND RIP THE SEAT COVER AWAY. I WAS SURE THIS WOULD SOLVE THE PROB. IT DIDN'T. THE CTLS WERE STILL FROZEN. I REMEMBERED ABOUT USING THE TRIM IN SITS LIKE THIS, AND I WAS BARELY ABLE TO BRING THE PLANE UP FROM ITS 20-30 DEG DIVE. I EVENTUALLY LANDED AT MY HOME ARPT. I WAS UNABLE TO FLARE ON LNDG AND BASICALLY DID A REAL 3 POINT LNDG. I TAXIED TO THE LCL FBO AND CHKED TO SEE IF THERE WAS ANYTHING RESTRICTING THE CTLS WHICH BECAME LOOSE AFTER I STOPPED THE ACFT. THEY FOUND A METAL CAMERA BRACKET WEDGED INTO THE CTLS. IT MUST HAVE FALLEN OUT OF MY POCKET AND SOMEHOW GOT INTO THE STICK BOOT WHICH WAS FAIRLY NEW AND OPENED ONLY AT ITS APEX WHERE THE STICK CAME OUT. IT AMAZED ME THAT 2 SEPARATE PROBS OCCURRED AT THE SAME TIME, BOTH RESTRICTING MY ELEVATOR CTL. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATED THAT THE FRONT SEAT COVER WAS AN AFTER MARKET ITEM WHICH DID NOT HAVE SNAPS ON THE BOTTOM TO HOLD IT DOWN. RPTR ADVISED THAT HE HAS INSTALLED A STRAP ON THE SEAT COVER TO HOLD IT DOWN AND PREVENT POSSIBLE INTERFERENCE WITH THE AFT STICK. RPTR STATED THAT THE REAR COCKPIT STICK BOOT IS ALSO A NON FACTORY ITEM AND FITS LOOSELY AROUND THE STICK. RPTR STATED THAT HE HAS SECURED THE TOP OF THE BOOT BETTER AND NO LONGER CARRIES LOOSE ITEMS WHEN DOING AEROBATICS. RPTR ADVISED THAT THE ITEM THAT FELL INTO THE STICK BOOT WAS A CAMERA TRIPOD BRACKET THAT WAS APPROX 1.5 INCHES SQUARE. RPTR STATED THAT THE ELEVATOR JAMMED IN THE NEUTRAL POS, THAT THE ACFT WAS NOT INVERTED, AND THAT HE USED 'UP' TRIM TO RECOVER FROM THE NOSE DOWN ATTITUDE. ANALYST QUESTIONS THE POSSIBILITY OF THIS ACTION AS THE CITABRIA ELEVATOR TRIM IS A TAB SYS WHICH WOULD REQUIRE OPPOSITE CTL WHEN FLYING THE ACFT WITH THE TRIM ONLY.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.