THIS ACR FLC EXPERIENCED A SERIES OF SHARP ROLLS AND YAWS FIRST TO THE L AND THEN TO THE R WITH THE BANK ANGLES UP TO 30 DEGS AND THE YAWS TO BTWN 5-10 DEGS. THE RPTR WAS BEHIND A B727-200; BUT IS UNSURE IF IT WAS THE CAUSE OF THIS EVENT.

Narrative

ROC-LGA. ESTABLISHED ON LGA LDA-A APCH RWY 22. AT 3000 FT (LEVEL) APPROX D15 FROM LGA (OUTSIDE CASLE INTXN) ACFT WAS AT APPROX 220 KIAS AND REDUCING SPD (CLEAN CONFIGN; AUTOTHROTTLES OFF). I WAS FLYING ACFT MANUALLY WHEN L WING ABRUPTLY DROPPED. CAPT AND I BOTH FOUGHT MOVEMENT OF ACFT AS R WING ABRUPTLY DROPPED. ACFT ROLLED APPROX 30 DEGS L; THEN 30 DEGS R; THEN STABILIZED. NO FURTHER EVENT TOOK PLACE. ACFT WAS LANDED NORMALLY. APCH CTL; WHEN ASKED; ADVISED US WE WERE FOLLOWING A B727 5 MI AHEAD; AND THIS WAS VERIFIED BY TCASII. NOSE DID NOT PITCH UP OR DOWN; AND AIR WAS CALM. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR WAS HAND FLYING A B737-200 DURING THIS EVENT. SHE SAID THAT SHE HAD BOTH FEET ON THE RUDDER PEDALS AND HER R HAND WAS ON THE CTL WHEEL AND HER L HAND WAS ON THE THRUST LEVERS. BOTH OF THE FLC SAW THE PRECEDING B727-200 AHEAD AND OFF TO THEIR R (LINED UP RWY 22 INSTEAD OF WITH THE LDA COURSE). THE ROLL AND YAW CAME WITHOUT ANY WARNING. THE RPTR SAID THAT THE MOVEMENTS WERE VERY SHARP. THE INITIAL ROLL WAS TO THE L AND THEN TO THE R. MORE CONCERNING TO HER WERE THE YAW MOMENTS. INITIALLY TO THE L THEN TO THE R AND THEN BACK AND FORTH FOR A TOTAL OF 6 OSCILLATIONS OF BTWN 5-10 DEGS. THE ROLLS WERE TO ABOUT 30 DEGS INITIALLY. THE RPTR SAID THAT SHE FELT THAT THEY HAD NO CTL OVER THE ACFT DURING THE 9-10 SECONDS THAT THESE OSCILLATIONS LASTED. THE RPTR WAS ADAMANT THAT THESE MANEUVERS MAY NOT BE CAUSED BY TURB. SHE SAID THAT THE MANUFACTURER'S REPRESENTATIVES PULLED THE FDR AND THE CVR AND INVESTIGATED THE INCIDENT; BUT SHE HAS NOT BEEN APPRAISED OF ANY FINDINGS.