Narrative:

On sep/xa/99, air carrier airlines flight xyz departed ZZZ at xa:59. After feeling a vibration in the landing gear on taxi out, the crew returned to the gate. Investigation revealed #1 main wheel bearings had failed. A plane change was made and the flight to abc left 2 hours and 6 min late. The aircraft (a B737-300 air carrier plane XXX) was taken to the hangar for further evaluation. A more detailed investigation revealed that the axle was damaged and was replaced along with both brakes, tires and wheel assemblies. The cause of the bearing failure was the inner bearing was the wrong bearing. The tire and wheel assembly with the wrong bearing was installed on sep/xb/99 and had made 6 lndgs before the bearings had failed. I was assigned to the air carrier airlines tire shop in ZZZ, us on aug/xa/99. One of my responsibilities that day was to be the second set of eyes in the installation of the wheel bearing. One man draws the new bearings from the bin, checks part numbers, inspects the bearings then packs the bearings with grease. After the tire assemblies are built up, he installs the bearings and signs off the bearing box on the serviceable tire tag. The second set of eyes was developed to prevent the wrong bearings from being installed. I was that second set of eyes and signed the box designated for that task on the tire tag. One of the B737-300 main wheel and tire assemblies built that day made it to aircraft XXX with the wrong inner bearing. I was responsible for checking the bearing part numbers, and somehow did not get the job done. I will not try to make excuses but would like to give my thoughts on what might have been some contributing factors in this incident: 1. The bearing that was installed was part number 594 a B757 main inboard bearing. The bearing that was the correct bearing was part number 596. Again I am not trying to make excuses but the part numbers are very similar and the numbers could get transposed. Also, the size of the two bearings in question are almost identical. 2. The ZZZ tire shop is a very busy place. A crew of 8 amt's in the summer months build appox 500 tires a month. In the last six months we have averaged 18.3 tire and wheel assemblies a day. The day of aug/xb/99 was especially heavy. 34 tire and wheel assemblies were built that day (more tires than any other day in ZZZ tire shop history) including 1 B757 main, 6 B727 main, 2 B737-200 mains, 3 B737-300 mains, 16 B737-300 noses, 4 A320 mains, 1 B777-a main, and 1 B747-400 main. The installations of the bearings are done at the end of the day. I think fatigue was a factor. To prevent future occurrences I'm building a go-no go gauge that will be a positive check of the two bearings that are so similar in size and part number. The gauge can be used after the bearings and retainers are in place. If approved by engineering, this will be a final check before the bearing shipping covers go in place. This scenario is a problem that has been going on for years. The bearing manufacture (timken) offered two years ago to color-code the bearing cages, but the company failed to adopt that change. Callback conversation with reporter revealed the following information: the reporter stated that 34 tires had been built up on this day and only 33 bearing sets were available and one set was ordered for the remaining tire. The reporter said 33 serviceable tires were dispersed to 4 terminal locations for ready access by the technicians. The reporter said he works in the tire build up shop and three possible scenarios can allow the wrong bearing to be installed. The reporter stated the wrong bearing could have been installed in the buildup shop or could have been robbed from a serviceable tire in the gate storage area for a bearing dropped in the dirt by a mechanic. The reporter said the third possibility is the manufacturer boxing the bearings with the wrong identification and the shop not checking the bearing part number and installing the bearing inadvertently. The reporter stated the real problem is a fool proof bearing identification method.the reporter said he submitted a go-no go gauge which checks the slight difference in bearings. The reporter said the company engineering department rejected this suggestion. The reporter stated the bearing manufacturer has suggested color coding the bearings but this idea was not acted upon by the company. The reporter said this is a real problem with carriers operating the B737-300-500 and B757-200 fleets. The reporter said the aircraft in this incident had a damaged axle sleeve and the wheel assembly was damaged.

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Original NASA ASRS Text

Title: A B737-300 WAS DISPATCHED IN NON-COMPLIANCE WITH THE L MAIN GEAR WHEEL AND TIRE ASSEMBLY INSTALLED WITH A B757-200 BEARING IN THE INBOARD POS.

Narrative: ON SEP/XA/99, ACR AIRLINES FLT XYZ DEPARTED ZZZ AT XA:59. AFTER FEELING A VIBRATION IN THE LNDG GEAR ON TAXI OUT, THE CREW RETURNED TO THE GATE. INVESTIGATION REVEALED #1 MAIN WHEEL BEARINGS HAD FAILED. A PLANE CHANGE WAS MADE AND THE FLT TO ABC LEFT 2 HRS AND 6 MIN LATE. THE ACFT (A B737-300 ACR PLANE XXX) WAS TAKEN TO THE HANGAR FOR FURTHER EVALUATION. A MORE DETAILED INVESTIGATION REVEALED THAT THE AXLE WAS DAMAGED AND WAS REPLACED ALONG WITH BOTH BRAKES, TIRES AND WHEEL ASSEMBLIES. THE CAUSE OF THE BEARING FAILURE WAS THE INNER BEARING WAS THE WRONG BEARING. THE TIRE AND WHEEL ASSEMBLY WITH THE WRONG BEARING WAS INSTALLED ON SEP/XB/99 AND HAD MADE 6 LNDGS BEFORE THE BEARINGS HAD FAILED. I WAS ASSIGNED TO THE ACR AIRLINES TIRE SHOP IN ZZZ, US ON AUG/XA/99. ONE OF MY RESPONSIBILITIES THAT DAY WAS TO BE THE SECOND SET OF EYES IN THE INSTALLATION OF THE WHEEL BEARING. ONE MAN DRAWS THE NEW BEARINGS FROM THE BIN, CHECKS PART NUMBERS, INSPECTS THE BEARINGS THEN PACKS THE BEARINGS WITH GREASE. AFTER THE TIRE ASSEMBLIES ARE BUILT UP, HE INSTALLS THE BEARINGS AND SIGNS OFF THE BEARING BOX ON THE SERVICEABLE TIRE TAG. THE SECOND SET OF EYES WAS DEVELOPED TO PREVENT THE WRONG BEARINGS FROM BEING INSTALLED. I WAS THAT SECOND SET OF EYES AND SIGNED THE BOX DESIGNATED FOR THAT TASK ON THE TIRE TAG. ONE OF THE B737-300 MAIN WHEEL AND TIRE ASSEMBLIES BUILT THAT DAY MADE IT TO ACFT XXX WITH THE WRONG INNER BEARING. I WAS RESPONSIBLE FOR CHECKING THE BEARING PART NUMBERS, AND SOMEHOW DID NOT GET THE JOB DONE. I WILL NOT TRY TO MAKE EXCUSES BUT WOULD LIKE TO GIVE MY THOUGHTS ON WHAT MIGHT HAVE BEEN SOME CONTRIBUTING FACTORS IN THIS INCIDENT: 1. THE BEARING THAT WAS INSTALLED WAS PART NUMBER 594 A B757 MAIN INBOARD BEARING. THE BEARING THAT WAS THE CORRECT BEARING WAS PART NUMBER 596. AGAIN I AM NOT TRYING TO MAKE EXCUSES BUT THE PART NUMBERS ARE VERY SIMILAR AND THE NUMBERS COULD GET TRANSPOSED. ALSO, THE SIZE OF THE TWO BEARINGS IN QUESTION ARE ALMOST IDENTICAL. 2. THE ZZZ TIRE SHOP IS A VERY BUSY PLACE. A CREW OF 8 AMT'S IN THE SUMMER MONTHS BUILD APPOX 500 TIRES A MONTH. IN THE LAST SIX MONTHS WE HAVE AVERAGED 18.3 TIRE AND WHEEL ASSEMBLIES A DAY. THE DAY OF AUG/XB/99 WAS ESPECIALLY HEAVY. 34 TIRE AND WHEEL ASSEMBLIES WERE BUILT THAT DAY (MORE TIRES THAN ANY OTHER DAY IN ZZZ TIRE SHOP HISTORY) INCLUDING 1 B757 MAIN, 6 B727 MAIN, 2 B737-200 MAINS, 3 B737-300 MAINS, 16 B737-300 NOSES, 4 A320 MAINS, 1 B777-A MAIN, AND 1 B747-400 MAIN. THE INSTALLATIONS OF THE BEARINGS ARE DONE AT THE END OF THE DAY. I THINK FATIGUE WAS A FACTOR. TO PREVENT FUTURE OCCURRENCES I'M BUILDING A GO-NO GO GAUGE THAT WILL BE A POSITIVE CHECK OF THE TWO BEARINGS THAT ARE SO SIMILAR IN SIZE AND PART NUMBER. THE GAUGE CAN BE USED AFTER THE BEARINGS AND RETAINERS ARE IN PLACE. IF APPROVED BY ENGINEERING, THIS WILL BE A FINAL CHECK BEFORE THE BEARING SHIPPING COVERS GO IN PLACE. THIS SCENARIO IS A PROB THAT HAS BEEN GOING ON FOR YEARS. THE BEARING MANUFACTURE (TIMKEN) OFFERED TWO YEARS AGO TO COLOR-CODE THE BEARING CAGES, BUT THE COMPANY FAILED TO ADOPT THAT CHANGE. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THAT 34 TIRES HAD BEEN BUILT UP ON THIS DAY AND ONLY 33 BEARING SETS WERE AVAILABLE AND ONE SET WAS ORDERED FOR THE REMAINING TIRE. THE RPTR SAID 33 SERVICEABLE TIRES WERE DISPERSED TO 4 TERMINAL LOCATIONS FOR READY ACCESS BY THE TECHNICIANS. THE RPTR SAID HE WORKS IN THE TIRE BUILD UP SHOP AND THREE POSSIBLE SCENARIOS CAN ALLOW THE WRONG BEARING TO BE INSTALLED. THE RPTR STATED THE WRONG BEARING COULD HAVE BEEN INSTALLED IN THE BUILDUP SHOP OR COULD HAVE BEEN ROBBED FROM A SERVICEABLE TIRE IN THE GATE STORAGE AREA FOR A BEARING DROPPED IN THE DIRT BY A MECHANIC. THE RPTR SAID THE THIRD POSSIBILITY IS THE MANUFACTURER BOXING THE BEARINGS WITH THE WRONG IDENTIFICATION AND THE SHOP NOT CHECKING THE BEARING PART NUMBER AND INSTALLING THE BEARING INADVERTENTLY. THE RPTR STATED THE REAL PROB IS A FOOL PROOF BEARING IDENTIFICATION METHOD.THE RPTR SAID HE SUBMITTED A GO-NO GO GAUGE WHICH CHECKS THE SLIGHT DIFFERENCE IN BEARINGS. THE RPTR SAID THE COMPANY ENGINEERING DEPARTMENT REJECTED THIS SUGGESTION. THE RPTR STATED THE BEARING MANUFACTURER HAS SUGGESTED COLOR CODING THE BEARINGS BUT THIS IDEA WAS NOT ACTED UPON BY THE COMPANY. THE RPTR SAID THIS IS A REAL PROB WITH CARRIERS OPERATING THE B737-300-500 AND B757-200 FLEETS. THE RPTR SAID THE ACFT IN THIS INCIDENT HAD A DAMAGED AXLE SLEEVE AND THE WHEEL ASSEMBLY WAS DAMAGED.

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.