Atlantic Southeast Airlines Flight 2311
| Atlantic Southeast Airlines Flight 2311 | |
|---|---|
 An EMB 120, similar to the one in the accident |
|
| Accident summary | |
| Accident type | Loss of control due to mechanical failure |
| place | near Brunswick , Georgia , United States
|
| date | April 5, 1991 |
| Fatalities | 23 |
| Survivors | 0 |
| Aircraft | |
| Aircraft type |
.svg){kind=small} Embraer EMB 120
|
| operator |
Atlantic Southeast Airlines
|
| Mark |
N270AS
|
| Departure airport |
Atlanta Airport , United States
|
| Destination airport |
Brunswick Airport , United States
|
| Passengers | 20th |
| crew | 3 |
| Lists of aviation accidents | |
Atlantic Southeast Airlines flight 2311 (flight number: EV2311 ) was a scheduled flight operated by Atlantic Southeast Airlines from Atlanta Airport in Georgia to the regional airport in Brunswick , Georgia. On April 5, 1991, an Embraer EMB 120 crashed on its approach for landing. The cause was loss of control due to heavy wear and tear in the area of a mechanical shaft of the propeller control and the resulting misalignment of the propeller blades. Astronaut Sonny Carter and former Senator John Tower died in the crash .
plane
The Embraer EMB 120 aircraft was delivered to Atlantic Southeast Airlines on November 30, 1990 and received its certificate of airworthiness on December 20, 1990. Before the accident, the aircraft had completed 845 take-offs and landings ( cycles ) with 816 operating hours. The machine was equipped with two Pratt & Whitney PW118 engines and Hamilton Standard 14RF-9 propellers. In the maintenance books, a fuel leak on the cowling of the auxiliary power unit was recorded as the only maintenance point. The machine was not equipped with a flight data recorder or cockpit voice recorder ; these were not mandatory for smaller machines at the time of the accident.
crew
The 34-year-old captain of the machine had been employed by Atlantic Southeast Airlines since 1981. He had type ratings for three different types of aircraft, including the EMB-120. At the time of the accident, he had 11,724 hours of flight experience, including 5720 in the EMB-120. He was involved as a pilot in the development of the EMB-120 and was trained by the manufacturer to fly this type of aircraft. His knowledge of the technology of the aircraft type was considered extensive and his performance as a pilot was excellent.
The 36-year-old first officer was hired by Atlantic Southeast Airlines in June 1988. He had a qualification as a flight instructor. He was given a first-class medical certificate during the previous body examination by the FAA, which qualified him for the rank of captain. However, since it had been more than 6 months since the last investigation, it was downgraded to a second class certificate, equivalent to the rank of first officer. At the time of the accident he had 3925 hours of flight experience, of which 2795 were on the Embraer EMB-120.
There was also a flight attendant on board.
Flight history
On the morning of the accident, the pilots of Flight 2311 reached Dothan regional airport at 6:15 a.m. local time. The taxi driver who picked up the pilots later said that they were in good spirits and very talkative at the time. The crew first flew to Atlanta, from where they made a return flight to Montgomery , Alabama . The pilots then had a two-and-a-half hour break, during which they would appear relaxed and talkative.
Flight 2311 should originally have been served with another EMB-120 with the aircraft registration N228AS . However, since this machine had a mechanical problem, N270AS was assigned to the flight. The machine had already made four individual flights that day without any problems. At 1:47 p.m. local time, Flight 2311 took off from Atlanta with a 23-minute delay.
In order to avoid a bad weather front, the crew deviated slightly from the usual flight route. At 2:48 p.m., the air traffic control crew in Jacksonville announced that the airport was in sight. The crew received a clearance to approach the Glynco Jetport in visual flight , which they immediately confirmed.
the accident
Later testimony indicated that the machine had flown unusually low in the last moments, at a height of 30 to 60 meters above the ground. The machine then immediately leaned 90 degrees to the left, fell to the ground in a swoop, and fell into a forest. All 23 people on board were killed in the impact.
Accident investigation
After the accident, the NTSB started the investigation. Since Sonny Carter and John Tower were two prominent figures among the victims, the crash received a lot of public attention.
As part of the aircraft accident investigation, the investigators were able to quickly rule out that a malfunction of the wing flaps or elevators could have caused the accident, after which pilots were able to keep the machine under control under such conditions during flights in the flight simulator. Since chopped-up leaf remains were found in the engines, an engine failure could also be ruled out.
It was found that a highly asymmetrical thrust caused the engine to roll to the left and become uncontrollable. The examination of the engines and propellers showed that the engines were running normally during the crash, but that the propellers had malfunctioned, which caused the propeller blades on the left side of the aircraft to be aligned almost perpendicular to the direction of flight. This had meant that the machine on the right engine had normal thrust, while on the left not only was there no thrust, but the machine was also braked by the position of the propeller blades.
The investigators found a shaft and a socket of the propeller control at the crash site, the internal teeth of which showed abnormally strong material wear. They found that the manufacturer of the propeller mechanics, Hamilton Standard , had only recently changed the design of the control shaft and now used a harder material in the manufacture of the shaft. According to the investigators, the different hardnesses of the material meant that the control shaft acted like a file on the control bush and rubbed off the teeth.
Attempts in which the defective shaft was installed in a test engine at Hamilton Standard could not initially confirm the investigators' thesis on the processes; the propellers with the defective control shaft went into the sail position of the engine attached to the ground. A test flight was therefore carried out in which the shaft was mounted in the engine of an Embraer EMB-120 of the same construction. In order not to endanger the test pilot, a lock was installed through which the propeller blades could be adjusted to an angle of no less than 22 degrees. The propellers on the wrecked machine had moved to a position of 3 degrees instead of going into the sail position at 79.2 degrees. During the test flight, the propeller blade actually moved to the 22-degree position and the pilots reported that under these circumstances it was difficult for them to keep the machine under control. The investigators came to the conclusion that the crew of the accident machine could not intervene because the defect had suddenly and unpredictably led to the loss of control. Subsequent test flights carried out on a flight simulator confirmed the inevitable loss of control when the propeller was turned, as on the plane destroyed in the accident.
Investigators also found that the airline violated the FAA's rules on rest times by designing their rosters so that pilots only slept about 5 to 6 hours a night. Investigators expressed concern about such practices, which were not uncommon in the industry at the time, but noted that fatigue was not a factor influencing the course of the accident in any way.
In its final report of April 28, 1992, the NTSB stated that the alleged cause of the crash was a loss of control. This was caused by a malfunction of the propeller control, which made it possible for the propeller blades to move into a misalignment. The incorrect design of the propeller unit by Hamilton Standard and the approval of the affected components by the FAA contributed to the accident.
Sources and web links
- Incident report in the Lessons Learned the Federal Aviation Administration
Individual evidence
- ↑ a b c d e f g h i j k l m n o p q Aircraft Accident Report: Atlantic Southeast Airlines, Inc., Flight 2311, Uncontrolled Collision With Terrain, to Embraer EMB-120, N270AS, Brunswick, Georgia, April 5, 1991. (PDF;) National Transportation Safety Board , accessed March 5, 2019 .
- ↑ Accident report Embraer EMB 120 N270AS , Aviation Safety Network (English), accessed on March 15, 2019.
Coordinates: 31 ° 15 ′ 34.8 ″ N , 81 ° 30 ′ 34.2 ″ W ,