What happened
On 3 July 2014, a Singapore Airlines Boeing 777-30/ER, registration 9V-SWH, departed George Bush Intercontinental Airport in Houston, Texas, bound for Moscow. During the departure via the INDIE ONE Standard Instrument Departure (SID), the aircraft climbed beyond a prescribed altitude of 4,000ft, placing it on a collision course with another aircraft descending to 6,000ft.
As the aircraft reached approximately 5,600ft, the Traffic Alert and Collision Avoidance System (TCAS) issued a Traffic Advisory, followed by urgent instructions from Air Traffic Control to descend to 5,000ft. Although a TCAS Resolution Advisory (RA) commanded a "Crossing Climb," the pilot flying initially failed to execute the maneuver correctly, continuing a descent instead. The conflict was resolved after the aircraft leveled off at 5,000ft, though the crew briefly attempted to climb back to a previously set altitude of FL310 before realizing the error.
The investigation
The investigation focused on why the crew failed to adhere to the SID altitude restriction. It was established that during the departure briefing, the pilot flying used an Electronic Flight Bag to review Jeppesen charts but failed to return to the routing text box after examining the pictorial map. This caused the crew to miss the specific instruction to maintain 4,000ft.
Investigators also examined the crew's cockpit management. The pilot flying had proactively set the altitude selector to the final cruise altitude of FL310 on the Mode Control Panel (MCP) despite not having clearance for that level. Furthermore, the pilot monitoring did not challenge this setting, and the initial radio contact with ATC failed to communicate the aircraft's intended climbing altitude, which might have alerted controllers to the deviation sooner.
Findings
- The primary cause was the flight crew's failure to notice the 4,000ft altitude restriction located in the routing section of the departure chart.
- The departure briefing was non-systematic, as the pilot ended the review on a zoomed-in map without re-verifying the text-based routing instructions.
- There was a breakdown in Crew Resource Management (CRM), characterized by a lack of monitoring by the pilot monitoring and a failure to communicate the plan to request intermediate altitudes from ATC.
- The pilot flying's decision to set the final cruise altitude (FL310) on the MCP prior to receiving clearance was contrary to standard operating procedures.
- The altitude restriction was not prominently displayed in the "Initial Climb" section of the chart, but was instead embedded in the routing text box.
Safety action
Following the incident, the operator implemented enhanced simulator training focusing on demanding TCAS RA scenarios and more rigorous CRM training to ensure pilots effectively challenge deviations. Additionally, the FAA updated its charting standards for RNAV SIDs to ensure the "top altitude" is clearly displayed in a prominent box at the top center of the chart to prevent similar oversight.