Rising, unpopulated terrain ahead of Runway 18 at Birmingham Shuttlesworth International Airport, Ala., could have created visual illusions that complicated the pre-dawn landing of UPS Flight 1354, an Airbus A300-600F that slammed into a hilltop short of the runway on Aug. 14, killing both pilots.

FAA training documents discuss a “black hole” illusion that it says is “particularly hazardous” when there are no lights before the runway and with city lights or rising terrain beyond the runway, conditions that are true for Runway 18 at Birmingham. “Those conditions may produce the visual illusion of a high-altitude final approach,” says the FAA. “If you believe this illusion, you may respond by lowering your approach slope.”

Evidence from the final seconds of the flight indicates that the approach slope was indeed much lower than expected. The aircraft sliced through tree tops and hit power lines over a house more than a mile from the runway threshold, continuing on to impact the rising face of a hill and breaking apart, the forward fuselage coming to rest only 200 yards beyond the impact area.

How the pilots found themselves at treetop altitude so far from the runway is a mystery the NTSB hopes to solve with the help of information from the cockpit voice recorder (CVR) and flight data recorder (FDR), UPS instrument approach standard operating procedures and other sources.

The engines did not appear to have experienced a pre-crash uncontained failure or fire, despite hitting the trees, and flight controls inputs were properly transmitted to the control surfaces.

Based on initial information the NTSB gathered from air traffic control tapes as well as the CVR and the FDR, the pilots had been cleared to land approximately 2 min. before impact. Flight 1354 was approaching the airport using a localizer non-precision instrument approach to Runway 18. There were scattered clouds at 1,300 ft. above the ground (AGL) and 10-mi. visibility. The autopilot was on and the autothrottles were engaged and maintaining airspeed at approximately 140 kt. The captain was flying the approach.

For a localizer approach, the aircraft receives precision lateral guidance to the runway but pilots use their altimeter to descend and maintain a safe altitude, in this case no lower 556 ft. AGL, until the crew visually sights the runway lights or precision approach path indicator (PAPI) lights through the windscreen. After going “visual,” the PAPI becomes the primary vertical guidance and pilots typically disconnect the autopilot and hand-fly the remainder of the approach. After the crash, the FAA verified that the PAPI was working correctly.

If pilots do not spot the runway before reaching the threshold, or if clouds or other obstacles cause them to lose sight of the PAPI or runway while in the visual segment, they are required to abort the approach in a go-around procedure. Birmingham's other runway, which has a full instrument-landing-system (ILS) approach with vertical guidance, was closed due to work on the centerline runway lights.

According to the NTSB, one of the pilots called “runway in sight” 13 sec. before the cockpit voice recorder (CVR) stopped recording, and 4 sec. before there were sounds on the CVR “consistent with an impact.” The NTSB had not determined at press time if the sound was the aircraft hitting the trees or impacting the hill. The FDR showed that the autopilot was engaged until 1 sec. before the recording stopped.

If in fact the “runway-in-sight” call was the first sighting rather than a repeat, the aircraft would have been well below the minimum descent altitude for the approach and possibly too low for the pilots to have seen the PAPI, raising the possibility that they had seen something other than the runway.

To understand the pilots' fitness, the NTSB has interviewed UPS employees and contractors who came into contact with the crew that morning and the evening before, in part to determine if fatigue may have played a part.

The captain and first officer began their duty day for UPS Flight 1354 in Rockford, Ill., at 9:30 p.m. the night before the crash. They flew to Peoria, Ill., and then on to UPS's hub in Louisville, Ky., for a layover before the 5 a.m. (EST) departure to Birmingham with a scheduled arrival 5:50 a.m. (CST). “They obtained keys for the sleep rooms in Louisville, and we want to determine if they used those rooms,” says NTSB member Robert Sumwalt.

The NTSB is also planning a flight test in a UPS A300 “to see how this approach would be flown in that type of aircraft, and to learn more about UPS's approach procedures,” Sumwalt says. He did not elaborate as to whether the approach would be performed during daylight or at night.