NTSB Identification: NYC06IA229.
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Incident occurred Tuesday, September 26, 2006 in Manchester, MA
Probable Cause Approval Date: 01/31/2008
Aircraft: American Blimp Corp. A-60+, registration: N614LG
Injuries: 1 Uninjured.

NTSB investigators used data provided by various sources and may not have traveled in support of this investigation to prepare this aircraft incident report.

Prior to departure, the operator's maintenance personnel performed engine starts, runups, and pressure checks. While a mechanic was performing the engine runups, a gust of wind kited the blimp and then forced it down, fully collapsing the wheel strut which was mounted to a truss assembly in the bottom of the control car in close proximity to the rudder control system's idler shaft assembly drive sprockets. The pilot of the blimp who witnessed the incident, discussed the incident with a mechanic, then entered the control car and moved the rudder pedals and control wheel each way to insure that there were no flight control restrictions; however, prior to departure, the pilot did not perform a pre-unmasting flight control check with the aid of the crew chief, which was required by the aircraft flight manual. After applying power and lifting off, the nose of the blimp began to move left. The pilot could not arrest the turn with the application of right rudder. There was no response or feedback from the rudder and the blimp began to drift to the east. The pilot tried to steer using differential power but, when he added power on either engine, it only increased the rate of turn to the left. As the blimp continued to drift eastward while simultaneously turning left, the blimp approached a metropolitan area and the Atlantic Ocean. The pilot then descended so that if the blimp drifted towards an "open" area, a rapid descent could be initiated to the ground. The descent was then continued by venting helium from the blimp's envelope. As the blimp continued to descend the pilot realized that there were no open areas in which to land, and as the blimp was headed into the wind, he brought both engines to idle and held both helium valves full open until the blimp settled into trees. Post incident examination of the blimps rudder control system revealed that the pedal cable/chain assembly had slipped off of the idler shaft assembly outboard drive sprocket. Further examination revealed that the sprocket was partially surrounded by two metallic tabs, one located above the sprocket, and one located below the sprocket, which acted as a chain keeper guard; however, the front and left side of the sprocket was unguarded.

The National Transportation Safety Board determines the probable cause(s) of this incident to be:

A malfunction of the rudder control system, and the pilot's inadequate preflight inspection. Contributing to the incident was the inadequate design of the chain keeper guards.

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