US investigators are attempting to ascertain whether the pilots of the crashed UPS Airbus A300-600 freighter used crew rest areas at Louisville before departing on the ill-fated flight.
The crew had been on an overnight duty, operating Rockford-Peoria-Louisville, with Birmingham as the next destination. The aircraft crashed short of runway 18 at Birmingham as it approached in darkness on 14 August.
As part of routine procedure the National Transportation Safety Board is looking into the 72h history of the crew, to assess their rest patterns.
"We know that they obtained keys for the sleep rooms in Louisville," says NTSB board member Robert Sumwalt, adding that the crew "signed out" the keys. "We want to see if we can determine if they actually used those rooms."
Information from the flight-data recorder shows the autopilot was engaged "until the last second of recorded data" from the instrument, says Sumwalt, while the autothrottle remained activated. But he points out that the flight-data recording ended several seconds before that of the cockpit-voice recorder.
Flight-control inputs "correlate" with the positions of the flight-control surfaces, says Sumwalt, while the engine parameters indicate normal powerplant operation.
The recording also indicates that the aircraft was "tracking" the selected airspeed of 140kt, which is "consistent" with the expected approach speed, he says.
Investigators will perform a flight test with a UPS A300 over the next few weeks to examine how the instrument approach procedure is flown.
But checks on Birmingham's precision-approach path indicator lamps - which provide a visual guide that pilots are on the correct glidepath - have shown that they were set to within 0.01° of their proper alignment.
Two surveillance cameras, one at the airport and the other at the adjacent Air National Guard station, captured images of the fire after the crash. Sumwalt says the NTSB has yet to determine whether they also recorded the accident.