A B737-300 FO FLYING RPTS LOC ERRATIC AND UNRELIABLE DURING FINAL APCH AT 2000 FT. UNABLE TO DETERMINE IF PAX ELECTRONIC DEVICE CAUSED LOC MALFUNCTION.

Narrative

WE WERE TOLD TO 'MAINTAIN 2000 FT UNTIL THE LOC; CLRED ILS RWY 13 APCH' WHILE ON DOGLEG. THE AUTOPLT WAS ENGAGED AND IN USE AT THIS TIME. SINCE WE DID NOT HAVE ANY DME OR A STICKMAP; I WAS FOLLOWING ALONG ON THE LEGS PAGE. THE LOC STARTED TO MOVE ERRATIC AND BOUNCED OFF THE SIDE. WE NOTIFIED THE CTLR THAT OUR LOC WAS ACTING ERRATIC. MOMENTS AFTER THAT CALL; THE LOC STABILIZED AGAIN AND APPEARED TO CTR ON THE HSI. SINCE I KNEW WE WERE GETTING CLOSE TO THE FINAL APCH COURSE AND THE GS WAS STABLE AND INDICATING AN ABOVE GLIDE PATH PROFILE; I DISENGAGED THE AUTOPLT TO ASSIST IN THE TURN TO FINAL AND BEGAN A DSCNT OUT OF 2000 FT. AFTER THAT; THE LOC REALLY STARTED BOUNCING ALL OVER THE HSI. I LEVELED OFF AT 1700 FT AND ADDED PWR TO CLB BACK TO 2000 FT. I REMEMBER THE CAPT CALLING THE CTLR THAT THE LOC WAS COMPLETELY UNRELIABLE. WHILE WE WERE STILL IN IMC; I PUSHED UP THE PWR; PULLED BACK ON THE YOKE; AND BEGAN TRIMMING THE ACFT. I EXPERIENCED SOME SPATIAL DISORIENTATION FEELING I HAD A CLB INDICATION DUE TO THE ACCELERATION AND FORCE ON THE YOKE. THE CAPT SAID; 'HEY; YOU'VE GOT TO CLB.' I SAID 'YEAH; I'M TRYING' AND TRADED SOME AIRSPD FOR ALT AND CLBED BACK TO 2000 FT. I HAD NOT INITIATED A GAR AS AT THIS POINT I HAD NO IDEA WHERE I WAS WITHOUT A STICKMAP; COURSE GUIDANCE; OR DME. I DO REMEMBER NOTING HOW UNUSUAL IT FELT TO CLB THE ACFT WITH GEAR DOWN AND FLAPS 15 DEGS; AGAIN; ADDING TO MY SPATIAL DISORIENTATION. THE CTLR WAS EXCELLENT AND NOTED WE HAD GONE THROUGH THE LOC COURSE TO RWY 13. SHE GAVE US A SNAP VECTOR TO RWY 7 AND AN ASR BELOW THE CLOUDS. SHE WAS OUTSTANDING! WE BROKE OUT AND RWY 7 WAS RIGHT IN FRONT OF US. DURING ALL THIS CONFUSION WE NEVER HAD ANY 'RED FLAGS' IN OUR INST CAGES. UPON LNDG; WE SPOKE WITH THE GND CTLR AS THEY INQUIRED ABOUT OUR ACFT. ANOTHER PLT JOINED IN AND MENTIONED IT SOUNDED LIKE A PAX WAS USING AN ELECTRONIC DEVICE. AFTER WE SHUT DOWN; I ASKED THE FLT ATTENDANT IF HE OBSERVED ANYONE WITH ANY DEVICES ON AND HE SAID HE DID. THIS FRUSTRATED ME; HOWEVER; I CAN'T PROVE THAT A PAX DID HAVE A DEVICE ON. I ASKED THE FLT ATTENDANT TO PLEASE BE AWARE IF HE SEES A PAX WITH A DEVICE ON AGAIN TO BE MORE VIGILANT IN TELLING THEM TO TURN IT OFF. SOME LESSONS AND OBSERVATION LEARNED; 1) I SHOULD NOT HAVE DISENGAGED THE AUTOPLT; 2) I SHOULD HAVE ANTICIPATED THE SPATIAL DISORIENTATION BEING IN IMC AND HOW DIFFERENTLY THE ACFT FEELS TRYING TO CLB PARTLY CONFIGURED; 3) I COULD HAVE TOLD THE CAPT SOONER THAT I WAS DISORIENTED AS HE WOULD HAVE BEEN READY TO FLY THE ACFT IF NECESSARY.