Narrative:

This report is about WX radar problems on 2 aircraft. Same problem with stabilization. When aircraft turns right, radar display falls off to the left and paints the ground. Turn left and radar display falls off to the right and paints the ground. The first aircraft was aircraft XXX. Radar had been written up the previous 2 days but since airline XXX is only required to give you history on only the previous leg flown, the cockpit crew was unaware of previous problems. Coordinated problem with dispatch and ATC. Returned to phoenix. The next aircraft was aircraft YYY. The same problem but aircraft had long history. 2 write-ups, in september 1997 by me. Written up again may 1998 by me. Same problem. This flight had same problem but WX had moved off to the east and it was more prudent to continue to denver than to return to phx where more WX was moving in. Obtained MEL in denver and continued to las under MEL since WX was good en route. The maintenance fix I found out later was to 'tighten tilt knob on radar.' no way, this aircraft is probably still flying around with a bad radar. Callback conversation with reporter revealed the following information: all his airline's B737-200's exhibit this problem. The #2 vertical gyroscope system has been allowed to deteriorate to the point it is incapable of stabilizing the radar antenna. He further states that the B737-200 fleet is so nonstandardized that there are insufficient spare parts for proper maintenance. The airline's B737-300's do not have this problem because they use ring laser gyroscopes.

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Original NASA ASRS Text

Title: B737 CREW RPT THAT THEIR AIRLINE CANNOT, OR WILL NOT REPAIR THE WX RADAR ANTENNA STABILIZATION SYS.

Narrative: THIS RPT IS ABOUT WX RADAR PROBS ON 2 ACFT. SAME PROB WITH STABILIZATION. WHEN ACFT TURNS R, RADAR DISPLAY FALLS OFF TO THE L AND PAINTS THE GND. TURN L AND RADAR DISPLAY FALLS OFF TO THE R AND PAINTS THE GND. THE FIRST ACFT WAS ACFT XXX. RADAR HAD BEEN WRITTEN UP THE PREVIOUS 2 DAYS BUT SINCE AIRLINE XXX IS ONLY REQUIRED TO GIVE YOU HISTORY ON ONLY THE PREVIOUS LEG FLOWN, THE COCKPIT CREW WAS UNAWARE OF PREVIOUS PROBS. COORDINATED PROB WITH DISPATCH AND ATC. RETURNED TO PHOENIX. THE NEXT ACFT WAS ACFT YYY. THE SAME PROB BUT ACFT HAD LONG HISTORY. 2 WRITE-UPS, IN SEPTEMBER 1997 BY ME. WRITTEN UP AGAIN MAY 1998 BY ME. SAME PROB. THIS FLT HAD SAME PROB BUT WX HAD MOVED OFF TO THE E AND IT WAS MORE PRUDENT TO CONTINUE TO DENVER THAN TO RETURN TO PHX WHERE MORE WX WAS MOVING IN. OBTAINED MEL IN DENVER AND CONTINUED TO LAS UNDER MEL SINCE WX WAS GOOD ENRTE. THE MAINT FIX I FOUND OUT LATER WAS TO 'TIGHTEN TILT KNOB ON RADAR.' NO WAY, THIS ACFT IS PROBABLY STILL FLYING AROUND WITH A BAD RADAR. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: ALL HIS AIRLINE'S B737-200'S EXHIBIT THIS PROB. THE #2 VERT GYROSCOPE SYS HAS BEEN ALLOWED TO DETERIORATE TO THE POINT IT IS INCAPABLE OF STABILIZING THE RADAR ANTENNA. HE FURTHER STATES THAT THE B737-200 FLEET IS SO NONSTANDARDIZED THAT THERE ARE INSUFFICIENT SPARE PARTS FOR PROPER MAINT. THE AIRLINE'S B737-300'S DO NOT HAVE THIS PROB BECAUSE THEY USE RING LASER GYROSCOPES.

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.