NTSB Identification: ERA10FA140
14 CFR Part 91: General Aviation
Accident occurred Monday, February 15, 2010 in Farmingdale, NJ
Probable Cause Approval Date: 03/08/2012
Aircraft: CESSNA T337G, registration: N12NA
Injuries: 5 Fatal.

NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.

One of the pilots announced over the airport’s common traffic advisory frequency his intention to perform a low pass over the runway, and ground witnesses observed the airplane fly about 50 feet above the runway with the landing gear retracted. Global positioning system data recovered from the wreckage indicated that the airplane’s ground speed at that time was about 160 knots (kts) (184 mph). Witnesses observed the airplane’s nose pitch up just before the outboard 6-foot section of the right wing separated, and the airplane descended uncontrollably and impacted the ground.

Although the pilot/owner seated in the left front seat was not rated to operate a multi-engine land airplane, he was known to perform ostentatious maneuvers in the accident airplane on previous occasions. The pilot seated in the right front seat was rated to operate a multi-engine land airplane. A placard above the airspeed indicator indicated, “Maneuvering --- 135 KTS (155 MPH)”; therefore, the pilot’s low pass and subsequent pitch up maneuver, consistent with an ostentatious display, was performed at an airspeed that exceeded this operating limitation. Postaccident metallurgical examination of airplane’s structure revealed that the right wing forward spar upper cap failed in compressive buckling. Although the left wing did not fail in flight, it showed buckling characteristics similar to the right wing, indicating that both wings were overloaded in upward bending.

The airplane was modified under 22 different supplemental type certificates (STCs), which included separate STCs for a short field take-off and landing (STOL) kit, an extended wingtip fuel tank, and winglets. The investigation found evidence that the combined effects of the multiple STC modifications on the accident airplane may have adversely affected the airplane’s wing structure because the combined effects of the STCs were not accounted for. For example, although not a factor in the in-flight breakup, skin fatigue cracks were observed at certain stations on the wing, which indicate that the airplane was subjected to vibratory stresses. Therefore, although each individual STC modification did not pose a concern, the combination of STCs on the accident airplane created wing loads that were not initially evaluated. As a result of this accident investigation, the Federal Aviation Administration (FAA) reevaluated the STCs and determined that revised operating limitations should be disseminated and implemented for this airplane; the FAA issued airworthiness directives (ADs) 2010-21-18 and 2011-15-11 to help address these issues. These ADs are available from the FAA’s website at . In addition, concurrent with this investigation, the NTSB investigated another accident (NTSB identification ERA10FA404)involving an airplane with multiple STCs installed and discovered that the FAA does not provide any guidance to an STC installer to help the installer determine the interrelationship between multiple STC modifications.

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

The pilots’ failure to adhere to the airplane’s operating limitations, which resulted in overload failure of the right wing. Findings of the investigation were the adverse effects of multiple supplemental type certificates (STC) to the airframe wing structure that were not evaluated at the time the STCs were installed and the lack of guidance by the Federal Aviation Administration for multiple STC interaction evaluation.

Full narrative available

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