Service difficulty report · Actuator Lug · Boeing 737291

Difficulty date
April 7, 1997
Submitted
March 26, 2000
Operation
Air carrier
Aircraft
N990UA
Make and model
Boeing 737291
Aircraft serial
21980
Engine
Pwa JT8D17
Part
Actuator Lug
Condition
Broken
Location
Rt Mlg
Stage of operation
IN
Nature of condition
O
Precautionary procedure
K

As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.

What was found

RT MLG ACTUATOR O/B ATTACH LUG WAS FOUND BROKEN IN HALF. THE HALF THAT WAS BROKEN OFF WAS IN TWO SECTIONS AND WAS FOUND TRAPPED IN A SEAL RETAINER IN THE LOWER TRAILING EDGE PANEL. THE ACTUATOR WAS RETAINED IN POSITION BY THE GEOMETRY OF THE WALKING BEAM. NO LANDING GEAR MALFUNCTIONS REPORTED. PARTS ARE UNDER FAILURE ANALYSIS. *S/D* MODE OF FAILURE WAS STRESS CORROSION CRACKING DUE TO STEADY HIGH TENSILE STRESS APPLIED IN A CORROSIVE ENVIRONMENT OVER A LONG PERIOD OF TIME. THE FOLLOWING WILL HELP ALLEVIATE THIS DISCREPANCY: APPLICATION OF PRIMER AND LOCKTITE TO BARE ALUMINUM SURFACES AND APPLICATION OF CORROSION INHIBITING SEALANT AROUND BEARING TO PREVENT MOISTURE INGRESS.