Narrative:

I was assigned to do a transit check on large transport. During my check I found #4 main wheel assembly with cord showing. I removed and replaced #4 main wheel assembly, as per the maintenance manual. During taxi out, the crew members said it felt like they had a flat tire. Upon return to the gate, #4 main wheel assembly was found loose on axle. I know for a fact that the axle nut spacer, axle nut, and axle nut lock screws were installed and safetied. The wheel assembly was rotated in direction of normal rotation during the torque procedure. It was torqued to correct specification 70 ft-pounds pre torque and 35 pounds final torque. It's my opinion that if wheel assembly was not correctly installed, the axle nut would not have torqued so easily, and if the axle nut lock screws were not aligned properly, they would not have seated fully and tightened up against the axle nut. Furthermore, if the wheel assembly was not all the way on the axle, the hub cap assembly would not have went fully into the anti skid transducer. I truly believe, after looking at the wheel assembly, the brake assembly and all the hardware, that the inner bearing failed and came apart. Once the bearing came apart it caused the wheel assembly to wobble, giving an indication that the crew thought was a flat tire. After the bearing failed and the tire was working back and forth there was a tremendous amount of heat buildup, but the fuse plug never blew. The inner race, bearing, and wheel assembly was severely damaged by the heat, to the point that they are scrap.

Google
 

Original NASA ASRS Text

Title: MECH RPT REGARDING WORK DONE ON WHEEL ASSEMBLY AND POSSIBLE PART FAILURE.

Narrative: I WAS ASSIGNED TO DO A TRANSIT CHK ON LGT. DURING MY CHK I FOUND #4 MAIN WHEEL ASSEMBLY WITH CORD SHOWING. I REMOVED AND REPLACED #4 MAIN WHEEL ASSEMBLY, AS PER THE MAINT MANUAL. DURING TAXI OUT, THE CREW MEMBERS SAID IT FELT LIKE THEY HAD A FLAT TIRE. UPON RETURN TO THE GATE, #4 MAIN WHEEL ASSEMBLY WAS FOUND LOOSE ON AXLE. I KNOW FOR A FACT THAT THE AXLE NUT SPACER, AXLE NUT, AND AXLE NUT LOCK SCREWS WERE INSTALLED AND SAFETIED. THE WHEEL ASSEMBLY WAS ROTATED IN DIRECTION OF NORMAL ROTATION DURING THE TORQUE PROC. IT WAS TORQUED TO CORRECT SPEC 70 FT-LBS PRE TORQUE AND 35 LBS FINAL TORQUE. IT'S MY OPINION THAT IF WHEEL ASSEMBLY WAS NOT CORRECTLY INSTALLED, THE AXLE NUT WOULD NOT HAVE TORQUED SO EASILY, AND IF THE AXLE NUT LOCK SCREWS WERE NOT ALIGNED PROPERLY, THEY WOULD NOT HAVE SEATED FULLY AND TIGHTENED UP AGAINST THE AXLE NUT. FURTHERMORE, IF THE WHEEL ASSEMBLY WAS NOT ALL THE WAY ON THE AXLE, THE HUB CAP ASSEMBLY WOULD NOT HAVE WENT FULLY INTO THE ANTI SKID TRANSDUCER. I TRULY BELIEVE, AFTER LOOKING AT THE WHEEL ASSEMBLY, THE BRAKE ASSEMBLY AND ALL THE HARDWARE, THAT THE INNER BEARING FAILED AND CAME APART. ONCE THE BEARING CAME APART IT CAUSED THE WHEEL ASSEMBLY TO WOBBLE, GIVING AN INDICATION THAT THE CREW THOUGHT WAS A FLAT TIRE. AFTER THE BEARING FAILED AND THE TIRE WAS WORKING BACK AND FORTH THERE WAS A TREMENDOUS AMOUNT OF HEAT BUILDUP, BUT THE FUSE PLUG NEVER BLEW. THE INNER RACE, BEARING, AND WHEEL ASSEMBLY WAS SEVERELY DAMAGED BY THE HEAT, TO THE POINT THAT THEY ARE SCRAP.

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.