NTSB investigators working to determine the cause of the recent in-flight breakup of a Piper trainer have discovered a wing crack in another Piper PA-28R-201 aircraft, the agency said on Tuesday. The crack measured about 0.040 inches long and deep. “The plane inspected had a similar number of total airframe hours and cycles [to the accident airplane] and was used exclusively for flight training of students,” the safety board wrote in its investigative update. After the crack was found, the wings were removed. “The airplane’s wings were subsequently reinstalled and examined using new inspection procedures developed by Piper Aircraft,” the safety board said in its investigative update. “A bolt-hole eddy current inspection probe was used to confirm the location and size of the previously identified crack.” Nine additional PA-28R-201 airplanes were inspected using eddy-current inspection (ECI) techniques under NTSB supervision. No crack indications were detected in those inspections, the board said.
ECI techniques can be used to detect cracks in metal structures, using an inspection coil that creates a magnetic field. When placed next to a conductor, this field induces an “eddy current” in the metal, which creates an imbalance when it detects a flaw. This imbalance then is magnified and shown on an oscilloscope. The NTSB update says the investigative team is examining the corrective actions taken after an accident in March 1987, in which a Piper PA-28-181 lost a wing in flight. After that accident, an Airworthiness Directive was issued (PDF), which required owners to remove the wings of their airplanes to check for cracks. That AD was rescinded in 1989. The NTSB’s observation that a crack was located successfully using Piper’s new inspection procedures seems to imply that a new directive might allow the use of ECI techniques rather than wing removal. Piper spokesperson Jacqueline Carlon told AVweb on Tuesday: “Piper Aircraft continues to support all investigative efforts by the NTSB.” The NTSB did not respond to AVweb’s request for comment.
A student pilot from Embry-Riddle Aeronautical University and an FAA examiner were killed in Aprilwhen the Piper PA-28 they were flying crashed shortly after takeoff from Daytona Beach International Airport. A wing detached from the aircraft prior to the crash.
IMAGE 1: In thisApril 10NTSB photo taken at the NTSB Materials Laboratory, the NTSB says fracture features consistent with metal fatigue can be seen in the aft spar web doubler of the Piper PA-28R-201 involved in the April 4 crash.
IMAGE 2: This NTSB graphic highlights the left-wing assembly and attachment bolt for a Piper PA-28R-201. The wing spar attachment bolt hole is an area of interest to the NTSB in its investigation.
