What happened
Two Beech E18S aircraft, operated by the same company, departed from the same location on a night cargo flight, taking off 10 minutes apart. The aircraft arrived at their destination 4 minutes apart and landed on runway 36L.
After the first aircraft, N2069C, landed, the tower controller cleared the pilot to taxi to the ramp. As the pilot approached the UPS ramp, they contacted the UPS ramp controller using a second radio. The ramp controller instructed the pilot of N2069C to hold short of the ramp. The instructions provided by UPS did not specify a particular location for the aircraft to hold.
While the first aircraft was stopped on the taxiway short of the cargo ramp, the second aircraft, N4980V, was cleared by the tower to taxi to the ramp. During this movement, the second plane collided with the first plane. At the time of the collision, the first aircraft was positioned nearly perpendicular to the path of the taxiing aircraft.
Findings
The collision took place in an area that was not visible to the air traffic control tower. Although all taxiway centerline lighting and blue edge lights were operational, visibility of the aircraft's position was hindered by the aircraft design. Both planes were equipped with rotating beacons on the lower fuselage and navigation lights on the wing tips and tail; however, for aircraft approaching from either side, the illumination from the tail navigation light on this specific model was blocked by the vertical stabilizers and rudders.