Dash 8-100
Flight Crew Air Transport Pilot (ATP)
Human-Machine Interface; Training / Qualification
Deviation / Discrepancy - Procedural Maintenance; Deviation / Discrepancy - Procedural Published Material / Policy; Ground Event / Encounter Loss Of Aircraft Control; Ground Event / Encounter Vehicle; Ground Incursion Taxiway
Aircraft Aircraft Damaged; Flight Crew Regained Aircraft Control; General Flight Cancelled / Delayed; General Maintenance Action
Equipment / Tooling; Human Factors; MEL; Procedure
The door was closed and we were cleared for pushback. As the tug began to push us back there were several large jolts and the tow bar came free from the tug. The tug driver stopped his vehicle and we continued to roll backward toward another aircraft. I applied the parking break to stop the aircraft. I entered the cabin to check on the Flight Attendant and the passengers as we had stopped more abruptly than normal. The Flight Attendant had finished her walk through and was sitting down at the moment we stopped and had stumbled into row one; but she was OK. I then exited the aircraft to see what had happened. I noticed the tow bar was still attached to the nose wheel and had rotated approximately 160 degrees. Ramp supervisors had arrived and asked if they could tow us back to our spot to clear the alley. I told them not to touch anything until I had spoken to Maintenance. I got back on the plane and asked the First Officer to call for an agent to deplane the passengers and proceeded to call Maintenance. The agent arrived and the passengers were deplaned. If the pin for the tow bar had been installed properly this incident would not have happened.
Captain called in to Maintenance Control and I took the call. Contract Maintenance was called and their Mechanic reported that a steering link had broken along with damage to a wire conduit and a steering fuse lug had sheared. No [other] structural damage was found. The decision was made to ferry the aircraft to a Maintenance Station for a Rough Towing Inspection and repair. The discrepancies were entered in the logbook and the broken link was secured with safety wire. I felt that the centering spring would keep the nose wheels straight and the aircraft was then ferried gear down and doors closed. The next day I was told that this was not true and the nose wheels could have moved due to the broken link.This event occurred because I had not researched deep enough into the manual to realize the broken link made the centering spring ineffective. Although it is not specifically spelled out; I still should have realized the centering spring centered the links and the links centered the nose wheels. My lack of complete understanding of the mechanism was why the inappropriate temporary repair and subsequent ferry happened.
When; during pushback of a DHC-8; the tow bar detached from the tug because the link pin was incompletely inserted. The resulting whiplash damaged a steering link and sheared a steering fuse lug on the aircraft. The damage required it to be ferried for inspection and repair. The interim fix utilized to prepare the nosegear for the ferry flight turned out to have been inappropriate and could have allowed the nose gear to swivel. Fortunately; that did not happen and the airplane was repaired and returned to service.