2011-11 · NASA ASRS report 983512
An Inspector and Mechanic report about their involvement with an incorrect position installation of an apex spacer at the right Main Landing Gear (MLG) Torque Links on a CRJ-900 aircraft. The right MLG had wobbled and split in two places on landing.
I came in and a CRJ-900; Aircraft X; was Aircraft On Ground (AOG) [status] for parts; for a Right-Hand Main Landing Gear (RH MLG) Strut Repack. We; Mechanics Y and Z and myself (Mechanic X); received the parts into the hangar. Mechanics Y and Z began to repack the RH MLG strut. The job went really well. I was the Lead Technician on duty with RII. So I observed the removal of lower torque link; as well as the installation. I don't recall at this time the position of the washer and apex spacer during the installation of the lower [MLG] torque link. The Final Inspection looked fine as well. Base Manager can verify the installation; he was standing there as well. If we did install the washer and apex spacer backwards; I am not sure really how; it does not seem it would have looked correct to me and I would have caught it. But I am human and we were being pressured to get the aircraft out as soon as possible. I reviewed the history of Aircraft X and [gear] shimmy seemed to be an issue before the strut repack was accomplished. It may be possible this was installed incorrectly; before we disassembled. Then [again]; may have been second nature [for mechanics] to reinstall the same way they took it apart. Like; I stated above; I honestly don't remember the position of the washer and apex spacer after completion of the installation. I do not believe this caused this incident either.Aircraft X had to be towed off runway [after landing] and the whole right MLG replaced. [An Engineering Order] has been issued to perform a Fleet Check of the apex spacer [position] on all CRJ-900 MLG Torque Assembly.
We had changed the right inboard main tire and brake. After letting the CRJ-900 off the jack; about an hour later noticed that the main strut had started to leak; that was about XA:30am. We started to get the aircraft ready to jack and disassemble the [main] strut. We got the jobcard; I don't recall who printed the jobcard or who picked the parts. After disassembly and cleaning; we put the strut seals on and found out we didn't have a new scraper seal. We went Aircraft On Ground (AOG) [status] for [the scraper seal]; I'm not sure of the time it [scraper seal] came in. We installed the scraper seal and reassembled the strut. I don't recall the exact way Mechanic Z and I reassembled the shimmy damper; we didn't take it apart. Maintenance Control was pressuring us to get it done; to get the aircraft out. I don't recall the way Mechanic Z and I put the torque link back together; but looking at another torque link on another aircraft; I don't think we could have; but we are human and we didn't disassemble it [torque link]; but we could have; it was a long day. The drawings on the jobcard are not real clear and the fact that we didn't take it apart [were contributors]. [We needed a] better drawing on the jobcard and a note on the jobcard about the location of and the difference [between]; the spacer [and the washer]. When the plane landed; the gear failed.
Reporter stated he was told the CRJ-900 aircraft was really wobbling going down the runway after landing. The right main gear strut housing had split in two places; the main gear did not fold under; but collapsed down; vertically. The upper and lower torque link bushings were found to be completely worn; where the torque links attach to the strut housing and lower piston/axle assembly.Reporter stated he was not involved with the earlier; initial teardown of the right main gear and torque links when the gear was leaking and found to be missing the scraper seal. He came into the gear re-assembly after the apex pin had been installed to check the drag brace pin torque wrench requirements. After the landing incident; the apex spacer was found installed under the head of the apex pin; instead of in between the forward ends of the upper and lower torque link. The washer that was supposed to be under the apex pin was installed where the apex spacer should have been. The apex pin goes through entire assembly including the shimmy damper. The apex spacer looks like two washers stuck together; with no other distinguishing left or right facing marks.Reporter stated his Air Carrier does not believe the incorrect location of the apex spacer was the 'smoking gun' that caused the right main landing gear failure; but if the spacer location was an issue; then the Manufacturer needs to better identify the apex spacer and the design of the assembly.
More incidents for this aircraft family
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.
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