Incident Overview
The crew reported that while the aircraft was on the ground at San Francisco, a mechanic added oil to the right engine. The captain stated that he observed the six latches in the down position and the cowling halves were flush. The first officer did not exit the aircraft to verify the cowling because the captain had been outside with the mechanic.
In-Flight Sequence
During cruise flight, the top half of the right engine cowling separated from the airframe. As it detached, the cowling struck the cabin window adjacent to row 4, causing the window to break and resulting in a loss of cabin pressure.
Passenger Impact
A female passenger seated in seat 4C received a laceration to her right forearm. Additionally, her purse was expelled through the opening created by the broken window.
Examination Findings
A post-incident examination of the failed nacelle components revealed no evidence of preexisting cracks.
Investigation
The investigation focused on the cowling separation and the subsequent depressurization event. No other factors were identified in the source material.