2011-01 · NASA ASRS report 929447
MD83 flight crew reports confusion over the crossing restrictions printed in the box next to WITLA on the BOACH 4 RNAV departure from LAS. The upper limit is exceeded resulting in a TCAS RA with an inbound B737.
It was the co-pilots leg departing Runway 1R at LAS on the Boach Four RNAV to Hector. Our altitude clearance; per the SID; was up to FL190. In the climb; and nearing WITLA Intersection; I noticed a B737 approaching from the right. Noting that our closure was going to produce a TA/RA; I quickly notified ATC trying to alleviate a TA/RA advisory. At the same time I consulted the departure plate to see what we had done wrong and to verify our altitude restrictions. Before ATC could respond; a TA/RA occurred that advised us to descend. While complying with the TA/RA; ATC directed us to descend to 10;000 FT and comply with the rest of the SID restrictions. The flight continued without further issues. I do not recall our altitude at the time of the TA/RA; but we were above the 10;000 FT restriction. Upon review of the departure plate; I quickly noticed that the WITLA Intersection altitude restriction had been compromised. I also noticed that the WITLA Intersection altitude restriction has a different depiction than I am used to seeing. The 'At or below 10;000 (ATC)' in one box and an 'At or above 7;900' in a completely different box; was a bit confusing. I am guessing that my co-pilot saw only the bottom box of 'At or above 7;900.' At first glance; I too; saw the bottom box as the restricting altitude. We did brief the departure and altitude restrictions prior to departure; but apparently not thoroughly enough.
The altitude box at WITLA is devided into an upper and lower halfs. The lower box reads 'At or above 7;900.' The upper box reads 'At or below 10;000 FT (ATC).' The (ATC) in parenthesis meant to us; if assigned by ATC. It had not.If 10;000 FT was to be a hard altitude we would have expected the established format of 'At or above 7;900' and at or below 10;000 FT.' I believe the lack of separation was caused by the chart formatting and not due to lack of crew review or inattention.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.
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