Formosa Airlines Flight 7623

Formosa Airlines Flight 7623

B-12255, the aircraft involved in the accident in October 1994
Accident
Date	18 March 1998 (1998-03-18)
Summary	Electrical failure
Site	9 kilometers northwest from Hsinchu Airport, Taiwan
Aircraft
Aircraft type	Saab 340B
Operator	Formosa Airlines
Call sign	BRAVO 12255
Registration	B-12255
Flight origin	Hsinchu Airport, Hsinchu, Taiwan
Destination	Kaohsiung International Airport, Kaohsiung, Taiwan
Occupants	13
Passengers	8
Crew	5
Fatalities	13
Survivors	0

Formosa Airlines Flight 7623 was a domestic flight from Hsinchu to Kaohsiung. On 18 March 1998, it crashed into the ocean shortly after take-off in a severe right bank, killing all 13 occupants on-board.^[1]

The aircraft involved was a Saab 340B. Registered B-12255, it had been manufactured in April 1993 and had since then accumulated 8,076 flight hours.^[2][3]

The flight's commander was 43-year-old Captain Fei Kuo-pang, a line instructor and a former Air Force veteran, he joined Formosa Airlines in 1989, and had clocked about 11,000 total flying hours, with 6,455 hours on the Saab 340. The co-pilot was 28-year-old First Officer Hung Chi-ping, having been employed by Formosa Airlines in October of the previous year, he was still undergoing line training at the time of the accident, and with only 305 hours of total flying time, 44 of them were on the Saab 340.^[4] Sitting in the observer's seat was 40-year-old First Officer Cheu Der-kun, also a retired Air Force pilot, he was scheduled to be on this flight to familiarize himself with the aircraft since he had been promoted to be trained as a Saab 340 captain. He had a total of 5,588 flight hours, including 613 hours on the Saab 340. A mechanic was on-board, 53-year-old Wu Kai-ying had been with Formosa Airlines for 8 years and had accumulated maintenance experience on the Saab 340 during that period.^[1]

During pre-flight checks, a failure of the right-hand main bus was noticed, which caused the following systems to be unavailable: the left-hand electronic flight instrument system (EFIS), the EFIS Comparators, LH/RH Flight Directors, LH RMI, autopilot, yaw-damper and others. Also, the No. 2 engine anti-ice start-bleed valve was left open because of this, which caused its ITT to be 15 °C higher than normal on that power.

According to the Minimum Equipment List (MEL), take-off with a Main Bus offline was prohibited, but the flight took off from runway 05 at 19:29 anyway. Due to the autopilot failure, the plane had to be flown manually. Since the yaw-damper also failed, rudder inputs would have been required, but they weren't made. The more than 30 °C ITT split between engines had a little effect on the aircraft, but only when the crew reduced power on the No. 2 engine, 30 seconds later, probably to reduce the ITT. This caused the No. 2 engine to have 13% less torque, leading to rolling and yawing to the right, which required constant left aileron.

The flaps, which were supposed to be retracted at 1,000 feet, weren't retracted until the plane almost reached the maximum allowed speed with flaps deployed. When the climb power was set, a symmetric Power Lever Angle (PLA) change was made. However, due to the earlier RH PLA pull in combination with the normal backlash in the power lever cables between the PLA and the Hydro-Mechanical Unit (HMU), the RH engine torque was decreased while the LH engine torque remained unchanged. This resulted in an even greater asymmetry.

The aircraft started to turn to the right, and the rate of climb started decreasing. The co-pilot transmitted to ATC: "Left 230, Bravo 12255", while the plane was at 21° degrees of right bank. 10 seconds later, the captain asked for assistance with his heading, during which the plane was in a 10° nose-up pitch and 24° right bank, which increased by one every second. After the captain said "Ask for radar vectors" he also made a small right aileron input, worsening the bank. At the last moments of the flight, right aileron commands were inputted, and the aircraft, 161 seconds after take-off, crashed into the ocean, pitched down 65°. None of the 13 occupants survived.^[5][2][3]

The RH Main Bus failure meant that the airplane couldn't take off according to the MEL. However, the pilots ignored this. The flight taking place at night in Instrument Meteorological Conditions (IMC), pilot fatigue (the captain was on duty for more than 11 hours), and system failures probably contributed to the loss of situational awareness and spatial disorientation, which caused the aircraft to bank further and further to the right. The crew also failed to follow standard operating procedures.^[2][3]

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