PVT PLT OF A BOEING STEARMAN ACFT CLAIMS THAT NEITHER HE OR HIS PLT PAX WAS CTLING THE ACFT WHEN IT SPIRALED DOWN TO TFC PATTERN LEVEL CONTRARY TO TWR CLRNC.

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DEPARTED SEBASTIAN; FL (X26); APPROX XA00 FOR LCL PLEASURE FLT (VFR) IN STEARMAN BI-PLANE. PAX WAS RETIRED AIR FORCE KC135 PLT (ATP/CFII) WITH APPROX 8000 HRS TOTAL TIME. PLT WAS PVT/SEL; 700 HRS TOTAL TIME; 130 HRS TIME IN TYPE. DURING LAST PHASE OF FLT PAX REQUESTED WE DO A LOW PASS AT VRB FOR FBO PERSONNEL; A SCHOOL WHERE PAX TAUGHT. VRB TWR ADVISED RWY 04 IN USE; PLAN A DOWNWIND (L) FOR RWY 04 AND EXPECT THE LOW APCH FOR RWY 11 FROM THE DOWNWIND. PAX THEN REQUESTED WE QUICKLY RADIO FBO OPS AND GIVE THEM AN ADVISORY. WITH ADVISORY DIALED INTO COM 1; I SAID (RADIOS IN REAR COCKPIT ONLY) 'OK; WE GOT IT...GO AHEAD.' PAX CONTACTED FBO OPS AND I THEN SWITCHED BACK TO TWR FREQ AND CONFIRMED OUR POS AND INTENTIONS. I REDUCED PWR FOR DSCNT FROM 2500 FT TO TPA. SHORTLY THEREAFTER; WE ENTERED A GENTLE R SPIRAL DSCNT APPROX 400 FPM. AFTER 2 TURNS; TWR ASKED US WHAT WE WERE DOING. I CALLED BACK THAT WE WERE 'SPIRALING DOWN TO TPA.' (APPROX 2 MI NNW OF TWR.) TWR EXCITEDLY CHASTISED US 'NOT TO DO THIS IN CLASS D AIRSPACE. WE SHOULD ALREADY BE AT TPA.' WHEN ACFT REACHED 800 FT I TOOK CTL (SAID 'I GOT IT') AND ESTABLISHED US ON THE L DOWNWIND RWY 04. MOMENTS LATER I HANDED THE ACFT OVER TO THE PAX; WHO COMPLETED THE FLY-BY ALONG RWY 11 UNDER TWR APPROVAL. WE THANKED ATC AND RETURNED TO X26. UPON LNDG; I DISCOVERED THAT THE PAX HAD RELEASED THE CTLS WHILE WE WERE APCHING VRB. WHEN I DIALED IN FBO AND SAID 'OK; WE GOT IT; GO AHEAD.' THE PAX THOUGHT I SAID 'I GOT IT' AND RELINQUISHED CTL. THE ACFT HAD BEEN TRIMMED AT APPROX 100 MPH. CONTINUED BY ITSELF FOR (EST) 30 SECONDS PRIOR TO MY PWR REDUCTION. UPON REDUCTION ACFT ENTERED THE GRADUAL R TURN AS DESCRIBED. TOTAL TIME ACFT NOT UNDER CTL APPROX 90 SECONDS (ESTIMATED). NO TFC HAZARD OR COLLISION AVOIDANCE REQUIRED. CONCLUSION: OPEN COCKPIT BI-PLANE VERY NOISY ENVIRONMENT TO COMMUNICATE IN. WILL BE MUCH MORE CAREFUL WITH CHOICE OF WORDS; AND WILL REQUIRE SECONDARY CONFIRMATION FOR CTL TRANSFER (EITHER A SHAKE OF THE STICK BY ACCEPTING PLT OR VISUAL ACKNOWLEDGEMENT VIA MIRROR UNDER TOP WING).