<< >> NASA ASRS Report 520103, August 2001

A C172R on landing lost the left main gear axle nut and outer bearing due to incorrect installation of axle nut cotter pin.

Attributes
ACN	520103
Time
Date	200108
Day	Sat
Place
Locale Reference	airport : zzz.airport
State Reference	US
Altitude	agl single value : 0
Environment
Light	Daylight
Aircraft 1
Operator	general aviation : personal
Make Model Name	Skyhawk 172/Cutlass 172
Operating Under FAR Part	Part 91
Flight Phase	ground : maintenance
Person 1
Affiliation	company other
Function	maintenance : technician
Qualification	technician : airframe technician : powerplant
Experience	maintenance technician : 25
ASRS Report	520103
Person 2
Affiliation	other
Function	flight crew : single pilot
Events
Anomaly	aircraft equipment problem : critical maintenance problem : improper maintenance maintenance problem : improper documentation non adherence : published procedure non adherence : far
Independent Detector	other flight crewa
Resolutory Action	none taken : detected after the fact
Consequence	other
Factors
Maintenance	contributing factor : schedule pressure performance deficiency : inspection performance deficiency : installation performance deficiency : testing
Supplementary
Problem Areas	Maintenance Human Performance Aircraft
Primary Problem	Maintenance Human Performance

Narrative:

On jul/xa/01, I accomplished a 100 hour service on a C172R. I was rushing because I was told the plane was slotted for a flight that night. I don't know if the plane flew. During the service, I installed the left wheel assembly on the axle. I put the cotter pin in through the axle, nut but I failed to put it through the axle. This made the wheel assembly unsecured. The plane flew for a couple of days, and was performing touch-and-goes. The pilot told me he performed 12-15 touch-and-goes. On the last landing, he said he heard a grinding sound. He discovered that the axle nut had backed off completely. The outer bearing came out. The wheel assembly was held in place by the brake caliper. He was ok and the plane too, except for the bearings.

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Original NASA ASRS Text

Title: A C172R ON LNDG LOST THE L MAIN GEAR AXLE NUT AND OUTER BEARING DUE TO INCORRECT INSTALLATION OF AXLE NUT COTTER PIN.

Narrative: ON JUL/XA/01, I ACCOMPLISHED A 100 HR SVC ON A C172R. I WAS RUSHING BECAUSE I WAS TOLD THE PLANE WAS SLOTTED FOR A FLT THAT NIGHT. I DON'T KNOW IF THE PLANE FLEW. DURING THE SVC, I INSTALLED THE L WHEEL ASSEMBLY ON THE AXLE. I PUT THE COTTER PIN IN THROUGH THE AXLE, NUT BUT I FAILED TO PUT IT THROUGH THE AXLE. THIS MADE THE WHEEL ASSEMBLY UNSECURED. THE PLANE FLEW FOR A COUPLE OF DAYS, AND WAS PERFORMING TOUCH-AND-GOES. THE PLT TOLD ME HE PERFORMED 12-15 TOUCH-AND-GOES. ON THE LAST LNDG, HE SAID HE HEARD A GRINDING SOUND. HE DISCOVERED THAT THE AXLE NUT HAD BACKED OFF COMPLETELY. THE OUTER BEARING CAME OUT. THE WHEEL ASSEMBLY WAS HELD IN PLACE BY THE BRAKE CALIPER. HE WAS OK AND THE PLANE TOO, EXCEPT FOR THE BEARINGS.

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.