What was found
PILOT REPORTED THE FOLLOWING: "AT ROUGHLY 230 P.M., I WAS MAKING MY WAY BACK FROM A NORTH CANYON TOUR LANDING SOUTH TAKEOFF WEIGHT 3767 POUNDS. WINDS WERE ABOUT 9 KTS GUSTING 18 FROM THE DIRECTION OF A ABOUT 220 AND I RECEIVED VERY LITTLE TO NO TURBULENCE THOUGHT THE ENTIRE FLIGHT. SHORTLY AFTER MAKING A CALL TO 978 THAT I WAS 2 MILES OUT, I EXPERIENCED A CONTINUOUS STRONG VERTICAL HOP ON COPTER 9 AT AN ALTITUDE OF 6900 AND AT AIRSPEED OF 90KTS. TEMPERATURE WAS ABOUT 29 DEGREES CELSIUS, TORQUE WAS AROUND 72, N1 WAS AT 94% AND N2 AT 100%. AS IT WAS HOPPING, I EXPERIENCED A DESCENT RATE OF ABOUT 300-400 FPM. ANTI TORQUE PEDAL PERFORMANCE DECREASED AND I STARTED TO YAW RIGHT BUT I WAS STILL ABLE TO MAINTAIN AIRCRAFT HEADING PLUS OR MINUS 10 DEGREES. THIS LASTED FOR ABOUT 3-4 SECONDS. WHEN IT HAPPENED, I INCREASED POWER TO STOP MY DESCENT AND INITIATED A CLIMB. WHEN THE AIRCRAFT LEVELED OFF, THE HOPPING STOPPED AND I WAS ABLE TO CLIMB BACK TO 6900 AND LAND SAFELY SHORTLY AFTER. PASSENGERS SEEMED OK. CURRENT PILOT WEIGHT 170 POUNDS. PERFORMANCE CALCULATION FOR THE DAY IGE 3900, OCE 3800."