DFW05LA167

While in cruise flight the 1,403-hour pilot noticed that the trim wheel had rotated almost 360 degrees from its original position, stopped, and rotated 180 degrees in the opposite direction with no pitch attitude changes. The pilot then felt a strong vibration moving forward and aft in the yoke, followed by a clacking sound. The pilot feathered both engines and subsequently made a forced landing following an in-flight loss of the stabilator trim control. Examination of the stabilator trim tab control rod, revealed evidence of internal corrosion at the stabilator trim tab rod. Further examination revealed evidence that the corrosion had reduced the thickness of the load carrying area of the stabilator trim tab control rod.

On June 21, 2005, approximately 1545 central daylight time, a Piper PA-23-250 twin-engine airplane, N2521M, registered to and operated by Water Tech DBA of Brawley, California, was substantially damaged during a forced landing following an in-flight loss of the stabilator trim control near Carizzo Springs, Texas. The private pilot and three passengers were not injured. Visual meteorological conditions prevailed and a flight plan was not filed for the 14 Code of Federal Regulations Part 91 personal flight. The 312-mile cross country flight originated from the Laredo International Airport, near Laredo, Texas, at 1500 and was destined for Pecos, Texas.

During a telephone interview conducted by the NTSB, the 1,403-hour pilot reported that during cruise flight at 8,000 feet mean sea level, he engaged the autopilot system to take a photograph of a passenger. The pilot then noticed that the trim wheel had rotated almost 360 degrees from its original position, stopped, and rotated 180 degrees in the opposite direction with no pitch attitude changes. The pilot then disengaged the autopilot and actuated the electric trim button on the yoke with no change in pitch. As the pilot verified stabilator control, a "strong vibration moving forward and aft" was felt in the yoke followed by a "clacking sound". Subsequently, the airplane started to "shudder," the pilot reduced power on both engines to idle, and the "shudder" stopped.

The pilot cross checked the engine instruments and observed the manifold pressure gauge for the right engine "pegged" and decided to feather the right engine. He then increased the power for the left engine to 21 inches of manifold pressure and declared an emergency. A few minutes later, the airplane started to vibrate a second time with 400-500 feet altitude oscillations. The pilot immediately reduced power and feathered the left engine. The pilot then initiated a forced landing to the desert flats.

Examination of the airplane by a Federal Aviation Administration (FAA) inspector, who responded to the accident site, revealed that the stabilator trim tab control rod was fractured and separated approximately three inches forward of the trim tab control rod attach point. The leading edges of both wings were crushed aft throughout their respective span. The right engine was folded upwards and aft onto the wing.

Examination of the stabilator trim tab control rod by the NTSB Materials Laboratory, located in Washington, D.C., revealed evidence of internal corrosion at the stabilator trim tab rod. Further examination revealed evidence that the corrosion had reduced the thickness of the load carrying area of the stabilator trim tab control rod.