Narrative:

I had completed about 6 uneventful touch-and-goes with my pre-solo student pilot (private rotorcraft). The last hourly ATIS was 320 degrees at 15 KTS gusting to 22 KTS, 10 mi, few 10000 ft. The winds had increased, become variable and on our previous landing were between 290 degrees at 19 KTS and 300 degrees at 18 KTS. We were on final approach to runway 33R when tower informed us of a learjet (model 24 or 25) on final to runway 33L. We were not advised of wake turbulence. I reported the lear in sight as it passed to the left and descended below us. I noticed the lear landed a bit beyond the 1000 ft markers of runway 33L (runway 33L begins beyond runway 33R) and was pulling off the runway as we crossed the threshold of runway 33R. Our approach was stabilized with 30 degrees of flaps and my student had proper crosswind inputs. My right hand was close to the yoke, my feet resting on the pedals and my left hand between the seats. At about 25 ft AGL, suddenly and abruptly we experienced approximately 60 degree left (upwind) wing roll down, and what seemed like 20-30 degree pitch down. I took the controls immediately, leveled the wings, applied full power and executed a go around. We returned for an uneventful landing on runway 33L. Initially I believed a wind gust was accountable for our abrupt upset. There are tall bushes and brush between the runways and I believed that both they and the relatively strong winds would break up the wake. I spoke to the tower, and they said they only saw the event once I had leveled the wings of the aircraft. They stated they didn't think it was wake turbulence from the learjet and attributed it to a wind gust coming off the bushes. However, the aircraft executing touch-and-goes behind us on runway 33R experienced no similar situation. Given the wind direction (left quartering headwind), our crosswind correction (left wing down) and the combination of the abrupt (left) roll and downward pitch movements, I believe we were affected by the lear's wake which was blown from runway 33L over to runway 33R. This event points to the importance of wake turbulence when landing on parallel runways, especially when winds favor blowing of the wake.

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Original NASA ASRS Text

Title: C172 INSTRUCTOR AND STUDENT ENCOUNTER POSSIBLE WAKE TURB WHILE LNDG ON A PARALLEL RWY 33R AT ISP.

Narrative: I HAD COMPLETED ABOUT 6 UNEVENTFUL TOUCH-AND-GOES WITH MY PRE-SOLO STUDENT PLT (PVT ROTORCRAFT). THE LAST HRLY ATIS WAS 320 DEGS AT 15 KTS GUSTING TO 22 KTS, 10 MI, FEW 10000 FT. THE WINDS HAD INCREASED, BECOME VARIABLE AND ON OUR PREVIOUS LNDG WERE BTWN 290 DEGS AT 19 KTS AND 300 DEGS AT 18 KTS. WE WERE ON FINAL APCH TO RWY 33R WHEN TWR INFORMED US OF A LEARJET (MODEL 24 OR 25) ON FINAL TO RWY 33L. WE WERE NOT ADVISED OF WAKE TURB. I RPTED THE LEAR IN SIGHT AS IT PASSED TO THE L AND DSNDED BELOW US. I NOTICED THE LEAR LANDED A BIT BEYOND THE 1000 FT MARKERS OF RWY 33L (RWY 33L BEGINS BEYOND RWY 33R) AND WAS PULLING OFF THE RWY AS WE CROSSED THE THRESHOLD OF RWY 33R. OUR APCH WAS STABILIZED WITH 30 DEGS OF FLAPS AND MY STUDENT HAD PROPER XWIND INPUTS. MY R HAND WAS CLOSE TO THE YOKE, MY FEET RESTING ON THE PEDALS AND MY L HAND BTWN THE SEATS. AT ABOUT 25 FT AGL, SUDDENLY AND ABRUPTLY WE EXPERIENCED APPROX 60 DEG L (UPWIND) WING ROLL DOWN, AND WHAT SEEMED LIKE 20-30 DEG PITCH DOWN. I TOOK THE CTLS IMMEDIATELY, LEVELED THE WINGS, APPLIED FULL PWR AND EXECUTED A GAR. WE RETURNED FOR AN UNEVENTFUL LNDG ON RWY 33L. INITIALLY I BELIEVED A WIND GUST WAS ACCOUNTABLE FOR OUR ABRUPT UPSET. THERE ARE TALL BUSHES AND BRUSH BTWN THE RWYS AND I BELIEVED THAT BOTH THEY AND THE RELATIVELY STRONG WINDS WOULD BREAK UP THE WAKE. I SPOKE TO THE TWR, AND THEY SAID THEY ONLY SAW THE EVENT ONCE I HAD LEVELED THE WINGS OF THE ACFT. THEY STATED THEY DIDN'T THINK IT WAS WAKE TURB FROM THE LEARJET AND ATTRIBUTED IT TO A WIND GUST COMING OFF THE BUSHES. HOWEVER, THE ACFT EXECUTING TOUCH-AND-GOES BEHIND US ON RWY 33R EXPERIENCED NO SIMILAR SIT. GIVEN THE WIND DIRECTION (L QUARTERING HEADWIND), OUR XWIND CORRECTION (L WING DOWN) AND THE COMBINATION OF THE ABRUPT (L) ROLL AND DOWNWARD PITCH MOVEMENTS, I BELIEVE WE WERE AFFECTED BY THE LEAR'S WAKE WHICH WAS BLOWN FROM RWY 33L OVER TO RWY 33R. THIS EVENT POINTS TO THE IMPORTANCE OF WAKE TURB WHEN LNDG ON PARALLEL RWYS, ESPECIALLY WHEN WINDS FAVOR BLOWING OF THE WAKE.

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.