Narrative:

[Aircraft was] on autopilot; descending via the bazbl STAR. Due to rain showers along the STAR plus other traffic; center had kept us at 250 KIAS and too high to make riice at 10;000 ft. Center was informed and said to just do the best we could; so this was not an issue.) center had released us from the 250 KIAS speed restriction (the other traffic was no longer a factor). Out of about 16;000 ft I used vertical speed plus speed brakes to make riice at 10;000 ft and 250 KIAS. Out of about 11;300 ft; we were handed off to approach. Several things happened at once: (1) the FMC went into 'altitude acq' mode (v/s window blanked); (2) aircraft was decelerating to 250 KIAS; and (3) approach cleared us down to 8;000 ft. The captain (pm) went to set the MCP to 8;000 ft; but the aircraft was still in 'altitude acq' mode with the speed still about 290 KIAS. I raised my hand in front of the MCP altitude window and said; 'not yet. It's still in 'altitude acq' mode; wait until we see 'altitude hold'.' the captain waited until it went into altitude hold mode; then he selected 8;000 ft; I then waited until we were at 250 KIAS before pushing 'level change' to descend to the new assigned altitude of 8;000 ft. We did not deviate from altitude or airspeed during the event. The purpose of this report is to show the types of events that are possible with the new procedure of pm setting altitudes in the MCP; while on autopilot. If I; as the PF; had been in control of the altitude selector in the MCP during the descent (old procedure); I would have delayed the setting of the new altitude in the MCP until it had gone into 'altitude hold' mode; thus eliminating the potential for an altitude deviation.

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Original NASA ASRS Text

Title: When ATC kept them high on an arrival the flight crew of an Airbus experienced a minor disagreement as to the desirable pilot PM/PF SOP that are best applicable to expediting their descent utilizing the FMS modes and the Altitude Alert window.

Narrative: [Aircraft was] on autopilot; descending via the BAZBL STAR. Due to rain showers along the STAR plus other traffic; Center had kept us at 250 KIAS and too high to make RIICE at 10;000 FT. Center was informed and said to just do the best we could; so this was not an issue.) Center had released us from the 250 KIAS speed restriction (the other traffic was no longer a factor). Out of about 16;000 FT I used vertical speed plus speed brakes to make RIICE at 10;000 FT and 250 KIAS. Out of about 11;300 FT; we were handed off to Approach. Several things happened at once: (1) the FMC went into 'ALT ACQ' mode (v/s window blanked); (2) aircraft was decelerating to 250 KIAS; and (3) Approach cleared us down to 8;000 FT. The Captain (PM) went to set the MCP to 8;000 FT; but the aircraft was still in 'ALT ACQ' mode with the speed still about 290 KIAS. I raised my hand in front of the MCP altitude window and said; 'Not yet. It's still in 'ALT ACQ' mode; wait until we see 'altitude hold'.' The Captain waited until it went into altitude hold mode; then he selected 8;000 FT; I then waited until we were at 250 KIAS before pushing 'level change' to descend to the new assigned altitude of 8;000 FT. We did not deviate from altitude or airspeed during the event. The purpose of this report is to show the types of events that are possible with the new procedure of PM setting altitudes in the MCP; while on autopilot. If I; as the PF; had been in control of the altitude selector in the MCP during the descent (old procedure); I would have delayed the setting of the new altitude in the MCP until it had gone into 'altitude hold' mode; thus eliminating the potential for an altitude deviation.

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.