AN ACR AT72 FLC HIT THE WAKE (ROTOR DOWNWASH) OF A HELI THAT CROSSED THEIR RWY AS THEY STARTED THEIR TKOF ROLL. THE AT72 FLC FELT A SHARP JOLT AS THEY WERE IN THEIR INITIAL CLB.

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A SINGLE-MASTED HELI LNDG TO THE N CROSSED THE DEP RWY AS IT DSNDED TO A HOVER. TKOF CLRNC RECEIVED WHEN THE HELI WAS STILL S OF RWY 10; BUT NO ADVISORY OR CAUTION FOR POSSIBLE WAKE TURB WAS PROVIDED. I MENTIONED THE POSSIBILITY TO THE CAPT (MY FLT) WHO ELECTED TO COMMENCE THE TKOF ROLL. SURE ENOUGH; AS WE PASSED THE POINT ON RWY 10 WHERE THE HELI HAD PASSED LESS THAN 2 MINS PREVIOUSLY -- OUR POINT OF ROTATION -- WE GOT A JOLT SUFFICIENT TO ROCK THE ACFT/DISPLACE THE ACFT. THE BAL OF THE DEP WAS UNEVENTFUL. I WAS SURPRISED AT THE LCL CTLR'S OMISSION. WHAT SHOOK US COULD HAVE REALLY DISPLACED A LIGHTER CRAFT. MY CAPT LEARNED HIS LESSON. WHO PINCHES THE CTLR? (CLASSIC ACCIDENT POTENTIAL BTWN FIXED WING AND ROTOR WING ACFT -- EVEN THOUGH HELI WAS DOING IT RIGHT -- AVOIDING FLOW OF FIXED WING TFC.) CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR WAS THE FO ON AN ATR72 THAT HIT THE ROTOR DOWNWASH OF A HELI SHORTLY AFTER LIFTOFF. HE SAID THAT HE SAW THE HELI APCHING THE RWY WHILE IN POS ON RWY 10 AT TVC AND THAT HE TOLD THE CAPT THAT THE CTLR WAS PROBABLY GOING TO RELEASE THEM AS IT STARTED ACROSS. HE ALSO; ALLEGEDLY; TOLD THE CAPT THAT THEY SHOULD HOLD BECAUSE OF THE POTENTIAL WAKE ENCOUNTER; BUT WHEN THE CTLR CLRED THEM FOR TKOF THE CAPT APPLIED PWR WITHOUT ACKNOWLEDGING HIS CAUTION OR HESITATING. ACCORDING TO THE RPTR; THEY WERE JUST ABOUT 50 FT IN THE AIR WITH THE GEAR COMING UP WHEN THEY FELT A SHARP JOLT THAT CAUSED THE ACFT TO BE DISPLACED IN EVERY AXIS; THEN EVERYTHING RETURNED TO NORMAL. THE FO SAID THAT HE THINKS THAT HE MENTIONED THE JOLT TO THE CTLR; BUT IS NOT SURE. HE SAID THAT THE CAPT WAS QUITE IMPRESSED BY THE EXPERIENCE AND TALKED ABOUT IT AT LENGTH. THE FO SAID THAT HE HAD BEEN A HELI PLT IN THE MIL AND WAS FAMILIAR WITH THE ROTOR DOWNWASH EFFECTS. HE HAD ALSO BEEN A CAPT WITH A LARGE AIRLINE AND WAS SENSITIVE ABOUT PUSHING THE CAPT TO MAKE THE CORRECT DECISION. HE SAID THAT MOST OF THE CAPTS SEEMED TO BE A BIT DEFENSIVE TOWARD HIM AND SOME OF THE OTHER HIGH TIME FO'S. SO HE WAS ATTEMPTING TO BE; IN THIS CASE; TOO GENTLE. THE RPTR SAID THAT HE WILL NOT DO THIS IN THE FUTURE. THE RPTR SAID THAT HE DOES NOT THINK THAT MOST PLTS AND CTLRS UNDERSTAND THE THREAT THE ROTOR DOWNWASH PRESENTS TO FIXED WING ACFT NEAR THE GND. HE IS WRITING A LETTER FOR PUB IN HIS UNION SAFETY BULLETIN.