HOMEBUILT AMPHIBIAN DEPARTS RWY ON TKOF ROLL. DAMAGES ACFT; RWY AND VASI LIGHTS.

Narrative

THE ACFT INVOLVED IS A 2 SEAT EXPERIMENTAL AMPHIBIAN. 1 PLT AND 1 PAX WERE ON BOARD. ACFT IS AN AVENTURA II. IT HAS A HIGH WING AND AN ENG WITH A PUSHER PROP MOUNTED ABOVE THE REAR OF THE WING. IT IS PWRED BY A ROTAX 912 ULS ENG. THE 40 HR TEST FLT PERIOD HAD JUST BEEN FLOWN OFF. THE FLT TEST REGIME HAD INCLUDED GROSS WT TKOFS AND LNDGS. ALL WERE ACCOMPLISHED WITHOUT INCIDENT. THE FIRST PAX FLT WAS ACCOMPLISHED WITHOUT INCIDENT; AND THE ACFT HANDLING WAS ACCEPTABLE. ON THE FIRST PAX FLT; THE CTR OF GRAVITY WAS FORWARD; BUT WITHIN RANGE; AND THE ACFT WAS APPROX 40 LBS BELOW GROSS WT. THE ACFT HAS DEMONSTRATED A L TURNING TENDENCY DURING TKOF RUNS; ESPECIALLY IF LIGHTLY LOADED. THE CAUSES OF THIS ARE THE HIGH TORQUE ENG; P-FACTOR; AND GYROSCOPIC PRECESSION WHEN THE TAIL IS LIFTED. THE PROPER TKOF TECHNIQUE IS TO GRADUALLY AND CAREFULLY ADVANCE THE THROTTLE; AND TO FLY THE TAIL OFF AFTER SUFFICIENT GND SPD HAS BEEN OBTAINED. TRYING TO LIFT THE TAIL TOO EARLY; SEEMS TO MAKE THE L TURNING PROB WORSE. HEAVIER WT SHIFTS THE CTR OF GRAVITY FORWARD; DECREASING THE MOMENT ARM OF THE REARWARD CTR OF GRAVITY; AND INCREASING THE MOMENT ARM OF THE RUDDER. THIS COMBINATION IMPROVES CONTROLLABILITY. THIS WAS THE SECOND PAX FLT. THE ACFT WAS APPROX 65 LBS BELOW GROSS WT. WIND WAS VERY LIGHT; BUT WAS A SLIGHT XWIND FROM THE R REAR. A R XWIND WOULD BE EXPECTED TO PUSH THE TAIL L; AND THE NOSE R. HOWEVER; UPON ADVANCING THE PWR; THE NOSE OF THE ACFT CAME L; AND THE TAIL WHEEL WAS NOT SUFFICIENT TO BRING THE NOSE BACK TO THE R. WE DEPARTED THE RWY AND CLIPPED A RWY LIGHT AND A VASI LIGHT BEFORE I WAS ABLE TO CUT PWR; AND REGAIN DIRECTIONAL CTL. THE ACFT WAS THOROUGHLY INSPECTED. DAMAGE TO THE ACFT WAS LIGHT WITH A SEVERED L SPONSON BEING THE ONLY PROB. SEAPLANE SPONSONS ARE DESIGNED TO BE SACRIFICIAL IN THE EVENT OF CONTACT WITH A HARD OBJECT. BOTH SPONSONS WERE REMOVED PRIOR TO THE RETURN FLT HOME. INITIAL EVALUATION OF THE ARPT FACILITY WAS THAT THE ONLY DAMAGE WAS THE RWY AND VASI LIGHTS. AFTER SOME REFLECTION; I COULD HAVE DONE 2 THINGS TO REDUCE THE SEVERITY OF THE PROB. FIRST; I SHOULD HAVE IMMEDIATELY REDUCED PWR TO REGAIN DIRECTIONAL CTL AND TO REDUCE GND SPD. SECOND; I COULD HAVE FLOWN THE TAIL OFF THE GND; GAINED MORE EFFECTIVE RUDDER CTL; AND THEREBY REGAINING DIRECTIONAL CTL PRIOR LIFTING OFF OF THE RWY.