Accident Sequence
National Airlines Flight 193, operating as a scheduled passenger service from Miami to Pensacola with en route stops at Melbourne, Tampa, New Orleans, and Mobile, departed Mobile at approximately 21:02 CDT on an IFR flight plan. The aircraft climbed to a cruising altitude of 7,000 feet. At 21:09, the crew was advised they would be vectored for an airport surveillance radar (ASR) approach to runway 25. At 21:13, the radar controller informed the flight that it was 11 nautical miles northwest of the airport and cleared it to descend and maintain 1,700 feet. At 21:17, flaps were selected to 15°, and two minutes later, the flight was cleared to descend to 1,500 feet, followed shortly by a clearance to the minimum descent altitude (MDA) of 480 feet. As the aircraft rolled out on the final approach heading, the captain called for the landing gear and the landing final checklist. At 21:20:15, the ground proximity warning system (GPWS) whooper warning sounded and continued for nine seconds until the first officer silenced it. Nine seconds later, the 727 impacted the water with the landing gear down and flaps at 25°. The aircraft came to rest in approximately 12 feet of water.
Rescue
Three passengers were killed. The remaining 55 occupants were rescued, among whom 11 sustained injuries.
Weather
The weather at the time of the accident was reported as 400 feet overcast, visibility 4 miles in fog and haze, wind 190° at 7 knots.
Findings
The investigation determined the probable cause of the accident: The flight crew's unprofessionally conducted non precision instrument approach, in that the captain and the crew failed to monitor the descent rate and altitude, and the first officer failed to provide the captain with required altitude and approach performance callouts. The captain and first officer did not check or utilize all instruments available for altitude awareness and, therefore, did not configure the aircraft properly and in a timely manner for the approach. The captain failed to comply with the company's GPWS flightcrew response procedures in a timely manner after the warning began. The flight engineer turned off the GPWS warning 9 seconds after it began without the captain's knowledge or consent. Contributing to the accident was the radar controller's failure to provide advance notice of the start-descent point which accelerated the pace of the crew's cockpit activities after the passage of the final approach fix.