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An first officer flying the psp sbono 1 arrival misunderstood the controller's 11;000 ft clowd crossing clearance and momentarily descended below 11;000; then returned. The commercial chart maa altitude formatting at crowd was confusing.
| Attributes | |
| ACN | 1002475 |
| Time | |
| Date | 201203 |
| Local Time Of Day | 1201-1800 |
| Place | |
| Locale Reference | ZLA.ARTCC |
| State Reference | CA |
| Environment | |
| Light | Daylight |
| Aircraft 1 | |
| Make Model Name | Large Transport Low Wing 3 Turbojet Eng |
| Operating Under FAR Part | Part 121 |
| Flight Phase | Initial Approach |
| Route In Use | STAR SBONO |
| Flight Plan | IFR |
| Person 1 | |
| Function | First Officer Pilot Flying |
| Qualification | Flight Crew Commercial |
| Events | |
| Anomaly | Deviation - Altitude Overshoot Deviation - Procedural Published Material / Policy Deviation - Procedural Clearance |
Narrative:
On the sbono approach; approach control cleared us to 11;000 ft to cross clowd intersection while descending around 12;000. We were within 5 miles of crossing clowd intersection. The commercial chart actually has maa 10;000 ft in bold letters beside the intersection on the chart but there is a faint arrow pointing the opposite direction of our flight path. I thought I heard the controller say 'cross clowd at 10;000 ft' but it was actually a clearance to cross at 11;000 ft. While the captain was clarifying the altitude; I descended through 11;000 ft due to my descent rate and thought process of not wanting to miss the crossing restriction that was quickly approaching. The whole event lasted less than 30 seconds. There was no conflict with other traffic. We were not in a sterile period and we were not talking to each other at the time. I misunderstood the controller. I would obviously not descend below the altitude the captain put in the autopilot altitude window until clarifying the altitude. I would also suggest commercial chart publisher make changes to the approach chart and move the maa 10;000 away from the SID course line.
Original NASA ASRS Text
Title: An First Officer flying the PSP SBONO 1 Arrival misunderstood the Controller's 11;000 FT CLOWD crossing clearance and momentarily descended below 11;000; then returned. The Commercial Chart MAA altitude formatting at CROWD was confusing.
Narrative: On the SBONO Approach; Approach Control cleared us to 11;000 FT to cross CLOWD Intersection while descending around 12;000. We were within 5 miles of crossing CLOWD Intersection. The Commercial Chart actually has MAA 10;000 FT in bold letters beside the intersection on the chart but there is a faint arrow pointing the opposite direction of our flight path. I thought I heard the Controller say 'Cross CLOWD at 10;000 FT' but it was actually a clearance to cross at 11;000 FT. While the Captain was clarifying the altitude; I descended through 11;000 FT due to my descent rate and thought process of not wanting to miss the crossing restriction that was quickly approaching. The whole event lasted less than 30 seconds. There was no conflict with other traffic. We were not in a sterile period and we were not talking to each other at the time. I misunderstood the Controller. I would obviously not descend below the altitude the Captain put in the autopilot altitude window until clarifying the altitude. I would also suggest Commercial Chart publisher make changes to the approach chart and move the MAA 10;000 away from the SID course line.
Data retrieved from NASA's ASRS site as of July 2013 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.