Narrative:

On approach into runway 35R, shortly after crossing the localizer OM, below 1800 ft AGL, captain flying, autoplt coupled ILS approach. LNAV selected, the aircraft pitched nose down between 5-8 degrees, following the pink command bars and the GS fly-down indication. This was followed by a series of pitch oscillations. The red flight director and intermittent red GS flags illuminated. The autoplt remained engaged. I disconnected the autoplt and observed the first officer's flight instruments showing normal with a slightly below GS indication and a flight director red flag. I xferred control to the first officer and he landed the aircraft successfully. After taxi in, we contacted moc. Maintenance came to the aircraft. Eventually the avionics person came to the aircraft. He pushed the glareshield GS test button and said it's ok. I insisted that I would not accept a GS MEL in IMC and the avionics technician sat down and tuned and observed the GS. After a few mins, the left GS failed. After a few more mins, it came back. The avionics technician and manager stated that they were going to MEL the GS. I insisted that I would not take the airplane and advised them I would be filing an as soon as possible report. After this statement, I was requested to leave the cockpit. The manager who spoke via cell phone with moc maintenance manager then brought out a test box that seemed to indicate the l-hand GS was weak. They proceeded to replace the l-hand navigation radio.

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Original NASA ASRS Text

Title: SF340 PIC RPT ON IMPROPER MAINT PRACTICE OF AN MEL ATTEMPT ON HIS ACFT'S ILS RECEIVER AFTER A PORPOISING MANEUVER BY HIS ACFT ON ILS FINAL APCH WHEN ARPT WX MINIMUMS WERE IFR.

Narrative: ON APCH INTO RWY 35R, SHORTLY AFTER XING THE LOC OM, BELOW 1800 FT AGL, CAPT FLYING, AUTOPLT COUPLED ILS APCH. LNAV SELECTED, THE ACFT PITCHED NOSE DOWN BTWN 5-8 DEGS, FOLLOWING THE PINK COMMAND BARS AND THE GS FLY-DOWN INDICATION. THIS WAS FOLLOWED BY A SERIES OF PITCH OSCILLATIONS. THE RED FLT DIRECTOR AND INTERMITTENT RED GS FLAGS ILLUMINATED. THE AUTOPLT REMAINED ENGAGED. I DISCONNECTED THE AUTOPLT AND OBSERVED THE FO'S FLT INSTS SHOWING NORMAL WITH A SLIGHTLY BELOW GS INDICATION AND A FLT DIRECTOR RED FLAG. I XFERRED CTL TO THE FO AND HE LANDED THE ACFT SUCCESSFULLY. AFTER TAXI IN, WE CONTACTED MOC. MAINT CAME TO THE ACFT. EVENTUALLY THE AVIONICS PERSON CAME TO THE ACFT. HE PUSHED THE GLARESHIELD GS TEST BUTTON AND SAID IT'S OK. I INSISTED THAT I WOULD NOT ACCEPT A GS MEL IN IMC AND THE AVIONICS TECHNICIAN SAT DOWN AND TUNED AND OBSERVED THE GS. AFTER A FEW MINS, THE L GS FAILED. AFTER A FEW MORE MINS, IT CAME BACK. THE AVIONICS TECHNICIAN AND MGR STATED THAT THEY WERE GOING TO MEL THE GS. I INSISTED THAT I WOULD NOT TAKE THE AIRPLANE AND ADVISED THEM I WOULD BE FILING AN ASAP RPT. AFTER THIS STATEMENT, I WAS REQUESTED TO LEAVE THE COCKPIT. THE MGR WHO SPOKE VIA CELL PHONE WITH MOC MAINT MGR THEN BROUGHT OUT A TEST BOX THAT SEEMED TO INDICATE THE L-HAND GS WAS WEAK. THEY PROCEEDED TO REPLACE THE L-HAND NAV RADIO.

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.