Date: 201505
Local time of day: 1801-2400
Location: ZZZ.Airport, US
Light: Night
Aircraft: B747 Undifferentiated or Other Model
Operator: Air Carrier
Operating under: Part 121
Mission: Cargo / Freight / Delivery
Flight phase: Parked
Aircraft component: Nose Gear Tire
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Technician
Reporter qualification: Maintenance Airframe; Maintenance Powerplant
Human factors: Communication Breakdown; Troubleshooting
Anomaly: Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: Aircraft In Service At Gate
Result: General Maintenance Action
Contributing factors: Human Factors; Logbook Entry; Procedure; Aircraft
Primary problem: Human Factors

Narrative: B747 aircraft arrived at ZZZ2 from ZZZ1 with a repeat write-up for nose wheel vibration at rotation. Per pilot debrief; vibration only occurred after rotation. Normal taxi-out; take-off roll; landing roll-out and taxi-in were normal. The pilot who observed the problem originally was a passenger and this flight from ZZZ1 to ZZZ2 and said his inbound to ZZZ1 had the exact same symptoms. ZZZ1 [Maintenance] signed off the original write-up as removed a piece of asphalt from a nose wheel tire. When I got the plane at ZZZ2; it was a repeat write-up with the two pilots echoing each other on the symptoms they observed. Per Fault Isolation Manual (FIM) XX-51-00-101; the most logical course of action was to change the Nose Wheel Steering Metering Valve. Management did not agree with that course of action and directed myself and my work partner to check the [nose wheel] spin brakes [in FIM] and replace the tires. We also [checked] tire inflation; improper tire wear and strut inflation. All were good.  Since we were directed by Management to perform certain steps which neither of us believed were applicable to the problem; I made separate write-ups stating that 'Management directs Nose Landing Gear (NLG) tire change; etc' in Logbook pages. I did not annotate our actions as Corrective Actions for the original discrepancy in Logbook because I did not feel these tasks were the proper corrective actions for the discrepancy.  I was assigned [the same B747] again tonight and noticed that the original discrepancy was signed off by another Mechanic and he cited my earlier work in his Corrective Action. He also stated that he inspected the tires and found no defects on them. I hope not; they were brand new.  I do not believe; nor does my partner who worked with me last night and again tonight; that the problem has been corrected and that the aircraft is safe to fly.

Callback: Reporter stated he and his work partner were following the Aircraft Maintenance Manual (AMM) and Fault Isolation Manual (FIM) Troubleshooting Tree of 'if Yes; if No;' procedures. The FIM asked if the Nose tires were wobbling on retraction into the nose wheel well. The answer was 'Yes'; per both pilots who made the repeat write-up inbound into their Station. The wobbling started when there was no weight on the wheels. The FIM than directed that the Nose Wheel Steering Control Valve (Metering Valve) be replaced. Since their Maintenance Supervisor did not want that FIM procedure followed; he and his partner were not going to sign-off the Corrective Action block in the Logbook for the repeat discrepancy. That's why he made separate write-ups for the work they did accomplish which included changing both nose tires. The B747 then flew to a foreign country where his Air Carrier contracts Heavy Maintenance. He does not know if any further maintenance was done on the nose gear at that station; but so far he has not seen any repeat nose wheel vibration issues on the aircraft. Given the vibration description by the pilots; he believes the wobbling will return as the nose tires start to wear.



Synopsis: A Line Aircraft Maintenance Technician (AMT) reports he was directed by a Maintenance Supervisor to replace both nose tires on a B747 aircraft instead of replacing the Nose Wheel Steering Control Valve (Metering Valve) per the Fault Isolation Manual (FIM) troubleshooting tree. Pilots had made a repeat write-up of a nose wheel wobbling vibration after rotation when weight was removed from nose wheels.