United Airlines Boeing 737-900 Flaps Problem at Austin on May 5th, 2024

On May 5th, 2024, a United Airlines Boeing 737-900, registration N39463, performing flight UA-381 from Washington Dulles, DC, to Austin, TX, encountered a flaps issue while on final approach to Austin’s runway 36R. The crew initiated a go-around, climbing back to 3,000 feet and entering a holding pattern to troubleshoot the problem. After approximately 30 minutes, the aircraft made a successful landing on runway 36L, the longest available runway at Austin-Bergstrom International Airport, at a slightly higher-than-normal speed of 165 knots over ground. Following the landing, the crew requested emergency services to inspect the aircraft’s brakes due to the higher landing speed.

Event Sequence:

• Approach and Flaps Issue: The Boeing 737-900 was on final approach to runway 36R at Austin when the flight crew reported a problem with the aircraft’s flaps. Flaps are crucial for increasing lift and drag during landing, allowing the aircraft to land at a lower speed. A malfunction of the flaps can affect the landing profile, requiring the aircraft to land at a higher-than-normal speed. Upon recognising the issue, the crew made the decision to abort the landing and initiate a go-around, climbing back to 3,000 feet for further troubleshooting.
• Holding Pattern and Troubleshooting: After executing the go-around, the crew requested delay vectors and entered a holding pattern to assess the nature of the flaps problem. During this 30-minute period, the crew consulted with their operations centre and reviewed relevant checklists, ensuring that the aircraft remained stable and safe for further descent. While in the holding pattern, the crew prepared the aircraft for a non-standard landing approach, accounting for the higher landing speed and altered landing configuration due to the flaps issue.
• Final Approach and Safe Landing: After holding and addressing the flaps issue to the extent possible, the crew elected to land on Austin’s runway 36L, the longest available runway, to provide additional safety margin given the increased landing speed. The aircraft landed safely at 165 knots over ground, higher than the normal landing speed due to the reduced lift from the flaps not being fully deployed. The landing was executed without further incident, but the crew requested emergency services to check the brakes as a precautionary measure, given the higher landing speed and the additional braking required to bring the aircraft to a stop.

Post-Landing Actions:

• Brake Inspection and Aircraft Status: Emergency services inspected the aircraft’s brakes and other critical systems following the landing. Although there were no reports of any immediate issues, the aircraft remained on the ground in Austin for further inspection and maintenance. As of 21 hours after landing, the aircraft was still grounded, indicating that additional checks or repairs may have been necessary to address the underlying flaps issue before the aircraft could be cleared for its next flight.

Technical Considerations:

• Flaps Malfunction: The flaps are essential for managing the aircraft’s landing configuration by altering the lift-to-drag ratio, allowing for lower landing speeds and shorter stopping distances. A malfunction in the flaps, such as a failure to deploy or retract properly, can result in a higher approach speed and longer landing distance, requiring precise handling from the crew. In this incident, the crew’s decision to divert to a holding pattern and troubleshoot the issue reflects standard operating procedures to ensure the safety of the passengers and aircraft.
• Landing at Higher Speed: The higher-than-normal landing speed of 165 knots is a direct result of the flaps not being fully deployed. Landing at such a speed requires greater braking effort and can put additional stress on the aircraft’s tyres and braking systems. It is standard practice for crews to request emergency services to inspect the brakes and tyres after such landings to ensure that no damage occurred during the deceleration phase.

Conclusion:

The flaps malfunction on United Airlines flight UA-381 from Washington Dulles to Austin was managed effectively by the flight crew, who made the prudent decision to execute a go-around and enter a holding pattern while troubleshooting the issue. The subsequent landing on Austin’s longest runway at a higher-than-normal speed was executed safely, and the crew took additional precautions by requesting emergency services to inspect the brakes following the landing.

The aircraft remained grounded for 21 hours after the event, undergoing further inspections to address the flaps issue and ensure that the aircraft was fully operational before its next flight. This incident highlights the importance of crew training and standard procedures in managing in-flight system malfunctions, ensuring that safety is maintained at all stages of flight.

The quick and professional actions of the crew, coupled with their communication with air traffic control, ensured a safe outcome for the passengers and crew, reinforcing the robust safety protocols in place for handling in-flight anomalies.