Atlantic Southeast Airlines (ASA) Flight 2311 ATC Recording

Credit(s)/Source(s): ‪@elsopaipilla315‬ & CONUS Archive
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Accident Description:
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𝗔𝘁𝗹𝗮𝗻𝘁𝗶𝗰 𝗦𝗼𝘂𝘁𝗵𝗲𝗮𝘀𝘁 𝗔𝗶𝗿𝗹𝗶𝗻𝗲𝘀 𝗙𝗹𝗶𝗴𝗵𝘁 𝟮𝟯𝟭𝟭 was a scheduled domestic passenger flight from Atlanta to Brunswick, operated by an Embraer EMB-120 Brasilia (Reg. N270AS) on 𝗔𝗽𝗿𝗶𝗹 𝟱, 𝟭𝟵𝟵𝟭.
The flight was initially scheduled to depart Atlanta at 13:24 EST and be operated by an EMB-120 Brasilia (Reg. N228AS). Because of mechanical problems an airplane change was made to N270AS. The flight departed Atlanta at 13:47 and arrived in the Brunswick area about 14:44. At 14:48 the flight was cleared for a visual approach to runway 07. The plane had just turned from base leg to final approach when the plane was seen to pitch up about 5° and roll to the left. The plane then nosed down into the ground, 9,975 feet short of the runway.
Examination of the left propeller components indicated a blade angle of about 3°, while the left PCU ballscrew position was consistent with a commanded blade angle of 79.2°. Extreme wear on the PCU quill spline teeth, which normally engaged the titanium-nitrided splines of the propeller transfer tube, was found. The titanium-nitrided surface was much harder and rougher than the nitrided surface of the quill. Therefore, the transfer tube splines acted like a file and caused abnormal wear of the gear teeth on the quill. Wear of the quill was not considered during the certification of the propeller system.
𝗣𝗿𝗼𝗯𝗮𝗯𝗹𝗲 𝗖𝗮𝘂𝘀𝗲:
"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."