What happened
On March 15, 2018, an Astra SPX aircraft, registration B-200 and 01, operated by Changsha Airlines, was conducting a target towing mission near the RCR-34 target area. After encountering cloud cover that prevented the mission from proceeding, the crew decided to return to Taichung Ching Chuan Kang International Airport for an ILS approach to runway 36.
During the return flight, the crew noted discrepancies in airspeed and altitude readings. The pilot flying noted that the airspeed indicators on the two sides of the cockpit were significantly different, eventually deciding to rely on the left-side indication. During the final approach, the aircraft's airspeed dropped below the required landing reference speed, and the aircraft triggered multiple "glideslope" warnings as it descended below the established glide path.
The aircraft touched down on runway 36 at approximately 19:10 local time. Upon landing, the aircraft's trajectory deviated from the centerline at a 1.5-degree angle toward the left. The left main gear drifted off the paved surface approximately 2,430 feet from the runway threshold. The aircraft continued to veer left for about 1,650 feet before returning to the pavement at the 3,125-foot mark. There were no injuries to the four occupants, though the aircraft sustained minor damage.
The investigation
The Taiwan Transportation Safety Board (TTSB) investigation revealed that the aircraft's landing weight was approximately 21,814 lbs, which exceeded the maximum landing weight of 20,700 lbs. Investigators also found evidence of moisture in the left-side static pressure lines, which likely caused the unreliable airspeed indications. The investigation examined cockpit voice recordings, which indicated that the crew experienced significant difficulty controlling the aircraft's direction and speed during the landing roll.
Findings
- The primary cause of the excursion was the pilot's failure to monitor and correct the aircraft's position and heading during the landing roll, combined with a lack of monitoring by the pilot monitoring.
- The approach was unstable, characterized by airspeed below the reference speed and multiple glideslope warnings; however, the crew failed to execute a missed approach.
- The aircraft was operating at an overweight condition, as the actual landing weight exceeded the maximum allowable landing weight.
- A lack of Crew Resource Management (CRM) was evident, including a steep cockpit authority gradient where the pilot flying made unilateral decisions regarding airspeed, and the pilot monitoring failed to challenge or correct the deviation.
- The crew failed to effectively manage the unreliable airspeed situation, specifically by not cross-checking against backup instruments or discussing flight parameters.