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B773, vicinity Houston TX USA, 2014
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|On 3 July 2014, a Boeing 777-300 departing Houston came within 200 feet vertically and 0.61nm laterally of another aircraft after climbing significantly above the Standard Instrument Departure Procedure (SID) stop altitude of 4,000 feet believing clearance was to FL310. The crew responded to ATC avoiding action to descend and then disregarded TCAS 'CLIMB' and subsequently LEVEL OFF RAs which followed. The Investigation found that an inadequate departure brief, inadequate monitoring by the augmented crew and poor communication with ATC had preceded the SID non-compliance and that the crew should have followed the TCAS RAs issued.|
|Actual or Potential
|Air-Ground Communication, Human Factors, Level Bust, Loss of Separation|
|Type of Flight||Public Transport (Passenger)|
|Intended Destination||Moscow/Domodedovo International Airport|
|Take off Commenced||Yes|
|ICL / ENR|
|Location - Airport|
|Airport vicinity||Houston Intercontinental|
|Tag(s)||Aircraft-aircraft near miss,|
Deficient Crew Knowledge-systems,
Deficient Crew Knowledge-automation
|Tag(s)||Data use error,|
Inappropriate crew response - skills deficiency,
Inappropriate crew response (automatics),
Plan Continuation Bias,
Procedural non compliance,
Ineffective Monitoring - PIC as PF
TCAS RA response
|Tag(s)||Required Separation not maintained,|
|Safety Net Mitigations|
|TCAS||Available but ineffective|
|Damage or injury||No|
|Causal Factor Group(s)|
On 3 July 2014, a Boeing 777-300 (9V-SWH) being operated by Singapore Airlines on a scheduled passenger flight from Houston to Moscow Domodedovo as flight SQ61 with an augmented flight crewcame into conflict with another aircraft after exceeding its Departure Procedure (SID) stop altitude of 4,000 feet on departure from Houston in day IMC. An ATC descent instruction and TCAS RA annunciations followed. The minimum recorded separation achieved was 200 feet vertically and 0.61nm laterally.
The National Transportation Safety Board (NTSB) did not investigate the event because it was "regarded as a pilot deviation from an ATC clearance" but the Singapore AAIB "regarded the occurrence as being significant enough to merit a report to highlight the safety lessons". It was acknowledged that the factual information available consisted primarily of inputs from the NTSB, the FAA and the Operator.
The operating flight crew consisted of a Captain acting as PF and a Senior First Officer. A relief Captain was also part of the crew and was present for the pre-departure briefing and on the flight deck for the departure. Each pilot had an EFB on which charts were stored. The departure from runway 15L on the SID given included a requirement to "MAINTAIN 4,000' or as assigned by ATC" and advised that the filed altitude could be expected 10 minutes after departure. However, this information was contained in lines two and three of a three line 'Routing' section in the text box at the bottom left corner of the SID chart and had been missed. The PF stated that when he had been briefing, after reading the first line of this section, he had scrolled "to the pictorial portion […] of the chart and zoomed in to check on the track and distances". He had then concluded to the PM and the relief Captain that "there were no altitude restrictions” and proceeded to set the initial FPL cruising altitude of FL310 on the MCP.
During post-event interviews, it was apparent that all crew members "expected" that there would be some intermediate altitude to level off at before being cleared to FL310 and the PF said that "when he did not see any intermediate altitude on the SID chart, he thought that it would be given to him by ATC later" and had planned to ask ATC for it if not given, but he had not communicated this "plan to ask ATC" to the PM, who it was considered could have reminded him to ask ATC later. The Departure Clearance subsequently given by ATC concluded with the phrase "climb via SID" after including the name of the SID and the Transition, but made no mention of the charted SID stop altitude.
Once airborne, initial contact with ATC was followed by a radar heading to take up after passing 2,500 feet; the read back of this clearance was noted not to have included the altitude the aircraft was climbing to. The climb was continued through the 4,000 feet stop altitude and passing approximately 5,000 feet, a TCAS TA was annunciated followed by an ATC instruction delivered "in an urgent tone" to descend to 5,000 feet. The PF disconnected the AP and initiated the descent and soon after this a TCAS CLIMB CROSSING CLIMB RA was annunciated. This was ignored and after 19 seconds, with the aircraft still descending, it changed to a 'LEVEL OFF' which continued until 'CLEAR OF CONFLICT followed 8 seconds later and the aircraft started to level off at "about 5,000 feet". It was found that at their closest, the two aircraft had been 200 feet vertically and 0.61nm laterally apart, the other aircraft having been descending to 6,000 feet in accordance with its clearance. The Relief Captain subsequently re-examined the SID Chart and noticed the 4,000 feet altitude restriction which they had all missed during briefing from the chart earlier.
The Investigation noted that the "climb via SID" clearance phraseology had been part of new procedures and phraseology introduced by the FAA earlier in 2014 and that it had been highlighted to crews and included in their recurrent training details. Under this system, if a SID Chart contains a stop altitude, the R/T phrase "climb via" is deemed to include it as well as the route and neither are repeated when including a SID in the Departure Clearance.
It was considered that the failure of the other two pilots to notice the operating Captain's pre-flight briefing error suggested "ineffectiveness of the monitoring action […] and that there is room for improvement in Crew Resource Management (CRM) training". It was also found that when ATC instructed the aircraft to descend to 5,000 feet, this altitude was not set on the MCP so that when the aircraft reached 5,000 feet, another unauthorised climb began and "it took another query from ATC" before the crew realised this error. A number of other Operator Standard Operating Procedures (SOPs) were observed to have been ignored, in particular the FCTM in respect of standard radio communications phraseology which "requires pilots to articulate both passing altitude and assigned altitude in their initial contact with a radar departure frequency".
It was, however, noted that the SID stop altitude only appeared in a text box whereas it would have been less likely to be missed had it been included on the diagram showing the SID routing, particularly as at the time of the event, it appeared in a text box headed 'Routing' rather than in the one above headed 'Initial Climb'.
The lack of familiarity of the crew with TCAS RAs in actual flight was noted - it was found that the investigated event was the first time the PF had experienced a Climb, Crossing Climb RA in actual flight and the first time the other two pilots had experienced any RA in actual flight.
Safety Action taken as a result of the investigated event included the following:
- Singapore Airlines made significant changes to the pilot recurrent training programme in support of better monitoring and CRM and by introducing "more demanding" TCAS RA scenarios that include ones with conflicting ATC instructions and scenarios which invite a junior PM to challenge a PF if SOPs are not followed.
- The FAA amended their standards for charting RNAV SIDs so that the stop altitude is clearly shown in a box at the top centre of the chart.
The Final Report of the Investigation was completed on 11 November 2015. No Safety Recommendations were made.