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Report: Intentional descent below MDA in thunderstorm causes ATR-72 CFIT accident in Taiwan
29 January 2016
Approach profile of flight GE222 (ASC)

Approach profile of flight GE222 (ASC)

An intentional descent below MDA during an approach in a thunderstorm caused the crash of an ATR-72 in Taiwan, the ASC investigation report shows. 

On July 23, 2014 TransAsia Airways flight GE222  departed from Kaohsiung International Airport on a scheduled domestic flight to Magong Airport, Penghu Islands, Taiwan. The flight had been delayed because of poor weather as a result of Typhoon Matmo that was passing through the area.

Weather conditions forced the flight to enter a holding pattern to wait for improvement. When a UNI Air ATR-72-600 landed at Magong following a VOR approach to runway 20, the crew of GE222 requested the same approach.

The latest weather information known to the crew was the the 18:45 report stating a visibility of 1,600 meters in thunderstorm rain, with ceiling at 600 feet. At 19:03 the controller cleared the flight to land on runway 20, reporting wind from 250 degrees at 19 knots. At that time the Runway Visual Range (RVR) had dropped to 600 meters.

Failing to observe the runway environment at the minimum descent altitude (MDA) of 330 feet, an altitude of 200 feet was selected. When the aircraft descended through 249 feet, the first officer said “we will get to zero point two miles”. At 19:05:44 and at an altitude of 219 feet, the captain disengaged the autopilot  and announced “maintain two hundred” four seconds later. The aircraft then maintained its altitude approximately between 168 and 192 feet for the following ten seconds. At 19:05:57, the captain asked the first officer “have you seen the runway”, and at almost the same time. The flight crew then had a conversation for about 13 seconds attempting to locate the runway environment. In the meantime, the altitude, course, and attitude of the aircraft started to conspicuously deviate to the left. At 19:06:11, both pilots called “go around” at 72 feet and both engine power levers were advanced. Two seconds later, the aircraft hit the foliage 850 meters northeast of the runway 20 threshold. The aircraft sustained significant damage and consequently collided with a residential area. Due to the high impact forces and post-impact fire, the aircraft was totally destroyed.

Findings Related to Probable Causes

Flight Operations
1. The flight crew did not comply with the published runway 20 VOR non-precision instrument approach procedures at Magong Airport with respect to the minimum descent altitude (MDA). The captain, as the pilot flying, intentionally descended the aircraft below the published MDA of 330 feet in the instrument meteorological conditions (IMC) without obtaining the required visual references.
2. The aircraft maintained an altitude between 168 and 192 feet before and just after overflying the missed approach point (MAPt). Both pilots spent about 13 seconds attempting to visually locate the runway environment, rather than commencing a missed approach at or prior to the MAPt as required by the published procedures.
3. As the aircraft descended below the minimum descent altitude (MDA), it diverted to the left of the inbound instrument approach track and its rate of descent increased as a result of the flying pilot’s control inputs and meteorological conditions. The aircraft’s hazardous flight path was not detected and corrected by the crew in due time to avoid the collision with the terrain, suggesting that the crew lost situational awareness about the aircraft’s position during the latter stages of the approach.
4. During the final approach, the heavy rain and associated thunderstorm activity intensified producing a maximum rainfall of 1.8 mm per minute. The runway visual range (RVR) subsequently reduced to approximately 500 meters. The degraded visibility significantly reduced the likelihood that the flight crew could have acquired the visual references to the runway environment during the approach.
5. Flight crew coordination, communication, and threat and error management were less than effective. That compromised the safety of the flight. The first officer did not comment about or challenge the fact that the captain had intentionally descended the aircraft below the published minimum descent altitude (MDA). Rather, the first officer collaborated with the captain’s intentional descent below the MDA. In addition, the first officer did not detect the aircraft had deviated from the published inbound instrument approach track or identify that those factors increased the risk of a controlled flight into terrain (CFIT) event.
6. None of the flight crew recognized the need for a missed approach until the aircraft reached the point (72 feet, 0.5 nautical mile beyond the missed approach point) where collision with the terrain became unavoidable.
7. The aircraft was under the control of the flight crew when it collided with foliage 850 meters northeast of the runway 20 threshold, two seconds after the go around decision had been made. The aircraft sustained significant damage and subsequently collided with buildings in a residential area. Due to the high impact forces and post-impact fire, the crew and most passengers perished.
8. According to the flight recorders data, non-compliance with standard operating procedures (SOPs) was a repeated practice during the occurrence flight. The crew’s recurring non-compliance with SOPs constituted an operating culture in which high risk practices were routine and considered normal.
9. The non-compliance with standard operating procedures (SOPs) breached the obstacle clearances of the published procedure, bypassed the safety criteria and risk controls considered in the design of the published procedures, and increased the risk of a controlled flight into terrain (CFIT) event.

10. Magong Airport was affected by the outer rainbands of Typhoon Matmo at the time of the occurrence. The meteorological conditions included thunderstorm activities of heavy rain, significant changes in visibility, and changes in wind direction and speed.

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