The Taiwan Transportation Safety Board (TTSB) released the Final Report on its investigation into the engine nacelle strike involving UPS Airlines Flight 5X61 during landing at Taiwan Taoyuan International Airport.

On August 13, 2025, UPS Airlines flight 5X61, a Boeing 747-8 freighter (B747-8F) registered in the United States as N613UP, was operating a cargo flight under the provisions of 14 Code of Federal Regulations Part 121 from Hong Kong International Airport (VHHH) to Taiwan Taoyuan International Airport (RCTP) with three flight crew members onboard. At 2008 Taipei local time, during landing on Runway 05L at RCTP, the aircraft sustained a No. 4 engine nacelle strike, which resulted in damage to the No. 4 engine and nacelle, the No. 3 engine nacelle, as well as multiple areas of the right wing and fuselage. No injury to any person involved in the flight or to any third party.

According to the Transportation Occurrence Investigation Act of the Republic of China and the content of Annex 13 to the Convention on International Civil Aviation Organization (ICAO), the TTSB, an independent transportation occurrence investigation agency, was responsible for conducting the investigation. The investigation team also included representatives from the U.S. National Transportation Safety Board (NTSB), UPS Airlines, and Taiwan’s Civil Aviation Administration (CAA). The investigation report was sent to relevant organizations and authorities for comments, subsequently reviewed and approved at the TTSB’s 89th Board Meeting on 14 August 2026, and released on 31 August 2026.

The investigation identified 15 findings based on a comprehensive review of factual data and analyses and issued 2 safety recommendations to the relevant organizations.

Ⅰ. Findings from the Investigation

Findings Related to Probable Causes

1. At the time of the occurrence, meteorological conditions at Taiwan Taoyuan International Airport were influenced by Typhoon Podul, resulting in strong and gusty winds with a significant right crosswind component on Runway 05L used by the occurrence aircraft for landing.
2. One second after touchdown, the No. 1 forward thrust lever was inadvertently advanced beyond the idle position, triggering automatic speedbrake retraction and causing the aircraft to retain high residual lift after touchdown.
3. The combination of high residual lift and the gusty right crosswind resulted in three transitions of the aircraft’s air/ground sensing system back to AIR mode, delaying the deployment and activation of the aircraft's deceleration devices. The resulting unstable aircraft state, together with the development of asymmetric thrust and the adverse wind conditions, further increased the complexity of aircraft control during the landing roll.
4. During the landing roll, the occurrence aircraft experienced multiple left roll tendencies associated with gusty right crosswind conditions. To counter these tendencies, large right control wheel inputs were applied by the Pilot Flying. The aircraft subsequently developed an excessive 9.2-degree right-wing-down attitude, exceeding the B747-8 ground contact angle limits, resulting in the No. 4 engine nacelle strike.

Findings Related to Risk

1. The delayed deployment of the speedbrakes and the No. 1 thrust reverser, together with the delayed application of wheel braking, reduced the stopping margin during the landing roll.
2. During the landing roll, the abnormal aircraft attitude directed the flight crew’s attention outside the cockpit, reducing the effectiveness of instrument monitoring. This contributed to both premature and delayed callouts related to deceleration devices and reduced the crew’s shared situational awareness of the abnormal aircraft configuration.
3. The occurrence aircraft’s engine nacelle strike during landing resulted in debris and detached components being scattered along the runway surface. Consequently, a subsequently landing B777F cargo aircraft sustained damage to three main landing gear tires, as well as multiple scratches and punctures to its belly composite panels.
4. Timely communication between the tower Local Controller and the occurrence flight crew could have facilitated earlier recognition of a possible engine nacelle strike and enhanced shared situational awareness of foreign object debris on the runway and its associated risks at an early stage, thereby preventing damage to subsequent landing or departing aircraft.
5. Both the tower Local Controller and the Local Monitor observed sparks emanating from the occurrence aircraft; however, this abnormality was not communicated to the occurrence flight crew, indicating ineffective application of Team Resource Management in addressing the potential operational risk.

Other Findings

1. The flight crew was properly certificated and qualified in accordance with applicable U.S. federal regulations. There was no evidence to indicate that medical conditions, fatigue, medication use, alcohol, or other drugs impaired the crew’s performance during the occurrence flight.
2. The occurrence aircraft was properly certificated, with no reported anomalies in the flight control systems.
3. The aircraft’s weight and balance remained within approved operational limits throughout the occurrence flight. Upon landing, the remaining fuel was sufficient for the aircraft to attempt additional approaches or to divert to its alternate airport.
4. During the first and second approaches, the flight crew determined that the crosswind conditions exceeded the operator’s limitations and executed go-arounds in accordance with standard operating procedures.
5. During the third approach, the reported wind conditions were within the operator’s approach limitations, and the crew established and maintained a stabilized approach in accordance with the operator’s stabilized approach criteria.
6. During the flare and initial touchdown of the third approach, the aircraft was handled in a manner consistent with the operator’s recommended crosswind landing techniques, and the flare and touchdown were within normal limits.

II.Transportation Safety Recommendations

To UPS Airlines

UPS Airlines advised that a number of proactive safety actions had been completed or were underway following the occurrence, as detailed in Section 4.2.1 of the Final Report. As these actions addressed the safety issues identified by the investigation, no safety recommendations have been issued in this report.

To Taiwan Civil Aviation Administration

1. Enhance training programs for tower controllers on Air Traffic Management Procedures, emphasizing that visual indications such as sparks require immediate advisory to the aircraft concerned and an assessment of runway integrity.
2. Strengthen Team Resource Management practices among Air Traffic Controllers to ensure that, when abnormalities are observed by any team member, timely and appropriate safety actions are initiated.

Full Report is available for download at https://www.ttsb.gov.tw

Eric Shen, Director

Secretary Office

Tel: +886-2-7727-6229

E-mail: ericshen@ttsb.gov.tw

Morris Yang, Investigator-In-Charge

Aviation Occurrence Investigation Division

Tel: +886-2-7727-6288

E-mail: morris@ttsb.gov.tw