What happened
During the approach to runway 31R, two Boeing 747 aircraft were being followed by a Swearingen SA 227AC Merlin. The crew of the Merlin accepted a visual approach, with air traffic control identifying the lead traffic at the 11 o'clock position.
Radar data revealed that the first 747 was positioned only 10 degrees to the left of the Merlin's nose, which the flight crew identified as the aircraft they were to follow. The second 747, intended to be the primary traffic for the Merlin to follow, was positioned at 45 degrees to the left of the nose. While on this visual approach, the Merlin passed approximately 300 feet above the top of the second 747 in the vicinity of the outer marker. No evasive action was taken by the crew during the encounter.
Findings
The captain of the Merlin noted that he typically flies between 1 to 1.5 dots high on the glide slope specifically to avoid wake turbulence. During the event, the sun was at an angle that caused both 747 aircraft to be backlit, potentially affecting visibility.