Incident Overview
On March 10, 2010, about 1255 eastern standard time, a Gulfstream G1159A (registration N155MM) operated by Northeastern Aviation Corporation under 14 CFR Part 135 experienced a loss of engine power on the No. 2 engine while climbing through 35,000 feet mean sea level. The flight, which originated from Republic Airport (FRG), Farmingdale, New York, at 1229, was destined for Witham Field (SUA), Stuart, Florida. Visual meteorological conditions prevailed and an instrument flight rules flight plan was filed. The airline transport pilot in command, co-pilot, cabin service representative, and two passengers reported no injuries.
Window Pane Separation
The pilot in command reported that while passing through 35,000 feet, the flight crew heard a sound similar to a compressor stall, followed by a loss of power on the right engine. An emergency was declared with air traffic control and engine shutdown checklist items were initiated. The cabin service representative informed the crew that the No. 4 outer window pane on the right side of the airplane had separated. The crew assumed the window pane had been ingested into the right engine. The flight crew received clearance to return to FRG, made a visual approach, and landed at 1318 without further incident.
Engine Examination
A bore scope examination of the engine revealed that a compressor stall and flameout occurred as a result of debris from the No. 4 outer window pane being ingested into the right engine. Foreign matter was attached to the high pressure stage 1 turbine blades. The combustion cans were clean. The high pressure compressor stage 1 blades were damaged. The high pressure nozzle guide vanes were not damaged. The engine was removed and a new engine was installed.
Window Analysis
Review of aircraft log books indicated that the No. 4 right window had been inspected every 72 months and at each emergency exit window release check, with no anomalies noted. The last inspection was on June 9, 2009, and the window had accumulated 15,065 hours and 8,526 cycles since new. No anomalies were found during that inspection.
The window was sent to the NTSB Materials Laboratory for analysis. Examination revealed that fractures in the outer pane originated from an area of preexisting progressive cracking emanating from the exterior surface. The cracking did not initiate from local surface damage or scratches. There were no signs of impact from aerodynamic forces and no indication of surface crazing. The initial cause of the cracking could not be determined.