Narrative:

On takeoff; upon raising nose; a violent nose wheel shimmy was felt. After wheel retraction; the nose gear unsafe light was illuminated and a visual inspection of the nose gear indicated that the gear was angled about 20 degrees and the scissors was up against the fuselage preventing the wheel from retracting into the wheel well. Upon landing; the shimmy was violent and we stopped and shutdown on the runway. We declared an emergency and had crash fire rescue equipment standing by. This is important because on this airplane; the nose wheel is the weakest part of the airplane. Previous incidents like this resulted in the nose gear being ripped out from under the airplane. The problem occurred because the shimmy damper pin not retracting into its sleeve and engaging the shimmy damper. While towing the aircraft; this pin has to be secured to the 'disengaged' position by a 'wedge'. After removing the tow bar; this pin has to be manually re-engaged and threaded knurled nut be placed over the pin preventing it from coming out and disengaging the shimmy damper. It is possible that this was not accomplished. Contributing factor(s): mission was rushed. Preflight inspection was done prior to towing activity therefore no control to verify pin was re-engaged and nut was installed. Before start checklist has a challenge and response item that only asks for wedge removal and not re-securing of the nut. Making sure this pin is re-engaged and nut is re-secured currently depends on 'tribal knowledge'. No process exists with controls to ensure re-engagement and re-securing. Corrective actions: before start checklist has been revised to include challenge and response verification that the nut has been re-secured. Pre-flight checklist will only be accomplished after towing activities have been completed and tow bar is removed. Pre-flight checklist will be revised to include pin re-engagement and and re-securing nut. All ground personnel will be re-trained to look for this particular item when clearing the aircraft to start. All personnel will be re-trained that re-installing the nut is the next activity is the process of removing the tow bar.

Related reports:

Google
 

Original NASA ASRS Text

Title: B-25 pilot reports violent nose wheel shimmy during rotation and an unsafe indication after gear retraction. Flight returns and lands safely; again with violent nose wheel shimmy; and shuts down on the runway. Shimmy damper pin was likely not properly engaged and secured after towing.

Narrative: On takeoff; upon raising nose; a violent nose wheel shimmy was felt. After wheel retraction; the nose gear unsafe light was illuminated and a visual inspection of the nose gear indicated that the gear was angled about 20 degrees and the scissors was up against the fuselage preventing the wheel from retracting into the wheel well. Upon landing; the shimmy was violent and we stopped and shutdown on the runway. We declared an emergency and had CFR standing by. This is important because on this airplane; the nose wheel is the weakest part of the airplane. Previous incidents like this resulted in the nose gear being ripped out from under the airplane. The problem occurred because the shimmy damper pin not retracting into its sleeve and engaging the shimmy damper. While towing the aircraft; this pin has to be secured to the 'disengaged' position by a 'wedge'. After removing the tow bar; this pin has to be manually re-engaged and threaded knurled nut be placed over the pin preventing it from coming out and disengaging the shimmy damper. It is possible that this was not accomplished. Contributing Factor(s): Mission was rushed. Preflight inspection was done prior to towing activity therefore no control to verify pin was re-engaged and nut was installed. Before Start Checklist has a challenge and response item that only asks for wedge removal and NOT re-securing of the nut. Making sure this pin is re-engaged and nut is re-secured currently depends on 'tribal knowledge'. No process exists with controls to ensure re-engagement and re-securing. Corrective Actions: Before Start Checklist has been revised to include challenge and response verification that the nut has been re-secured. Pre-flight Checklist will only be accomplished AFTER towing activities have been completed and tow bar is removed. Pre-flight Checklist will be revised to include pin re-engagement and and re-securing nut. All ground personnel will be re-trained to look for this particular item when clearing the aircraft to start. All personnel will be re-trained that re-installing the nut is the next activity is the process of removing the tow bar.

Data retrieved from NASA's ASRS site as of April 2012 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.