新人自制 熟肉版本 维基百科 大西洋东南航空2311号航班
Atlantic Southeast Airlines Flight 2311 was a regularly scheduled commuter flight from Hartsfield-Jackson Atlanta International Airport to Brunswick Golden Isles Airport which suffered an uncontrolled collision with terrain during landing approach just north of Brunswick, on April 5, 1991. The aircraft was an Embraer 120RT Brasilia, registered N270AS.
A few minutes before the aircraft impacted the ground, controllers at Glynco Jetport cleared flight 2311 for a visual approach to runway 07 at the airport. Witnesses reported that as the airplane approached the airport, it suddenly turned or rolled to the left until the wings were perpendicular to the ground. The airplane then fell in a nose-down attitude and disappeared out of sight behind the trees. Four years later, another Embraer Brasilia of ASA crashed in the Georgia countryside in similar circumstances, with nine fatalities.
The aircraft involved in the accident was an Embraer EMB-120 Brasilia, manufactured on November 30, 1990. It was equipped with two Pratt & Whitney PW-118 engines and Hamilton Standard 14RF-9 propellers. The airplane received its U.S. standard airworthiness certificate on December 20, 1990. The aircraft had accumulated about 816 flying hours prior to the accident. Only one deferred maintenance item was noted in the maintenance logs. This was for fuel leaking from the auxiliary power unit cowling. The circuit breaker for the APU had been pulled while spare parts could be made available to fix the cowling.
Captain Mark Friedline, age 34, had been hired by Atlantic Southeast Airlines in May 1981. He was fully qualified to fly three different commercial aircraft including the EMB-120. It was estimated that at the time of the accident, he had accumulated about 11,724 total flying hours, of which 5,720 hours were in the EMB-120. He had been involved in the development of the EMB-120, and its introduction to service in the United States, and was trained to fly the aircraft by the manufacturer. An inspector described his knowledge of aircraft systems \"extensive\", and his pilot techniques as \"excellent\".
First Officer Hank Johnston, age 36, was hired by Atlantic Southeast Airlines in June 1988. He was a qualified flight instructor. Because more than 6 months had passed, since he had undergone an FAA medical inspection and he was issued with a first-class certificate, it automatically reverted to a second-class certificate. A second-class certification was adequate for his duties as a first officer. At the time of the accident, it was estimated that he had accumulated about 3,925 total flying hours, of which 2,795 hours were in the EMB-120.
Flight Attendant Cindy Crabtree, age 30, was hired by Atlantic Southeast Airlines in 1986.
On the morning of the accident, the captain and the first officer arrived at the Dothan Regional Airport by taxi about 06:15. The taxi cab driver reported that the crew was in good spirits and readily engaged in conversation. The crew flew first to Atlanta, then performed a round trip to Montgomery, Alabama, before returning to Atlanta. After this round trip, the crew had a scheduled break for around two and a half hours, in which they were described to be well rested and talkative.
Flight 2311 was scheduled initially to be operated by N228AS, another EMB-120 . However, this airplane experienced mechanical problems, and so the flight was switched to N270AS. This aircraft had flown four times already on the day of the accident with no reports of any problems. The flight departed just before 14:00.
The flight crew then took off 23 minutes behind their planned schedule and flew the aircraft to Brunswick, deviating slightly to avoid poor weather. Just after 14:48, the flight crew acknowledged to Jacksonville air route traffic control center that the airport was in sight, and flight 2311 was subsequently cleared for a visual approach to Glynco Jetport, which the flight crew acknowledged.
The last transmission received from flight 2311 was to the ASA manager at the airport, who reported that the flight made an “in-range call” on the company radio frequency and that the pilot gave no indication that the flight had any mechanical problems. Witnesses reported seeing the aircraft approaching the airport in visual meteorological conditions at a much lower than normal altitude. Several witnesses estimated that the aircraft flew over them at an altitude of 100 to 200 feet above the ground.
The majority of the witnesses reported that the airplane suddenly rolled to the left until the wings were perpendicular to the ground. The aircraft then descended in a nose-down attitude and disappeared from sight behind trees near the airport. One witness told investigators that they saw a puff of smoke emanate from the aircraft prior to or subsequent to the airplane rolling to the left. Others reported loud engine noises described as a squeal, whine, or an overspeeding or accelerating engine during the last moments of the flight, although they said that these noises seemed to have stopped, or at least faded before the aircraft impacted with flat ground two miles short of the runway.
An observer driving along a road southwest of the airport told an NTSB investigation that he saw the airplane in normal flight at normal altitudes, and that he believed that the approach was not abnormal. The airplane completed a 180-degree turn from the downwind leg of the approach and continued the turn. He then saw the aircraft pitch slightly, before it rolled to the left until the wings were vertical. The airplane then turned nose-down and smashed into the ground. He saw no fire or smoke during the flight and he believed both propellers were rotating.
An investigation carried out by the National Transportation Safety Board initially determined that a malfunction of the asymmetric flaps, ailerons or rudder could not have caused the accident, after multiple pilots in simulators managed to keep the aircraft under control. Engine failure was also ruled out by detailed inspection of the two engines. The investigators found that the circumstances of this accident indicate that a severe asymmetric thrust condition caused a left roll that led to loss of control of the airplane. The investigation examined all the possible events that could have caused the loss of control. The powerplant and propeller examinations indicated that the engines were operating normally but that a propeller system malfunction occurred which caused abnormally low propeller blade angles and a high drag condition on the left side of the aeroplane.
The NTSB found that the flight crew would have been unable to perceive any problem with the airplane until the propeller blade angle was between 24 and 26 degrees. They stated that the airplane would have \\\"become very difficult to control after the propeller reached the 22-degree stop. Therefore, it is most likely that the pilots of flight 2311 did not notice a problem with the airplane until the propeller began to overspeed and roll control was affected.\\\" Thus, the flight crew would have been unable to declare an emergency as the event was so sudden.
Whilst in the final report, it was accepted that the fact that Atlantic Southeast was overworking pilots, estimating that the pilots only received 5 to 6 hours of sleep, contrary to FARs played no part in the accident, the NTSB raised concerns that the airline, along with other commuter airline corporations, "scheduled reduced rest periods for about 60 percent of the layovers in its day-to-day operations. The Safety Board believes that this practice is inconsistent with the level of safety intended by the regulations, which is to allow reduced rest periods as a contingency to a schedule disruption, and has the potential of adversely affecting pilot fitness and performance."
Eventually, the NTSB concluded that the probable cause of the accident was:
the loss of control in flight as a result of a malfunction of the left engine propeller control unit which allowed the propeller blade angles to go below the flight idle position. Contributing to the accident was the deficient design of the propeller control unit by Hamilton Standard and the approval of the design by the Federal Aviation Administration. The design did not correctly evaluate the failure mode that occurred during this flight, which resulted in an uncommanded and uncorrectable movement of the blades of the airplane’s left propeller below the flight idle position.
Former Texas senator John Tower, 65, his daughter Marian, astronaut Manley "Sonny" Carter, American College of Physicians president-elect Dr. Nicholas Davies, and N.A.T.O. liaison Dr. June T. Amlie, were among the 23 passengers and crew killed.Two children, Brian and Laura Birdsong, ages 9 and 6, also died in the accident. A statue was erected in their memory at Zoo Atlanta.