B777 first officer reports being cleared to FL310 and initiating descent in VNAV. He is subsequently...

Attributes
ACN	1181629
Time
Date	201406
Local Time Of Day	1201-1800
Place
Locale Reference	ZAU.ARTCC
State Reference	IL
Environment
Flight Conditions	VMC
Aircraft 1
Make Model Name	B777 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	Descent
Route In Use	Vectors
Component
Aircraft Component	MCP
Person 1
Function	First Officer Pilot Not Flying
Experience	Flight Crew Last 90 Days 240 Flight Crew Total 23735 Flight Crew Type 6500
Events
Anomaly	Conflict Airborne Conflict Deviation - Procedural Clearance

Narrative:

Cruising at FL360 we were cleared to FL310 while 10 NM north of grb and requested to expedite. Subsequently cleared to FL280 while still in VNAV. MCP altitude window was reset to FL280 but button was not pushed. Aircraft leveled at FL310 while remaining in VNAV. Told by ATC to turn to 090 heading and continue descent to FL280. Received TCAS traffic caution about this time from opposite direction aircraft at FL300. Next told by ATC to maintain FL310. We climbed from about FL307 to FL310. First officer disconnected autopilot and started turn to 090 and climbed back up to FL310.

Original NASA ASRS Text

Title: B777 First Officer reports being cleared to FL310 and initiating descent in VNAV. He is subsequently cleared to FL280 which is set in the MCP but the button is not pushed and the aircraft levels off at FL310. This is not immediately detected by ATC or the crew resulting in a conflict.

Narrative: Cruising at FL360 we were cleared to FL310 while 10 NM north of GRB and requested to expedite. Subsequently cleared to FL280 while still in VNAV. MCP altitude window was reset to FL280 but button was not pushed. Aircraft leveled at FL310 while remaining in VNAV. Told by ATC to turn to 090 HDG and continue descent to FL280. Received TCAS traffic caution about this time from opposite direction aircraft at FL300. Next told by ATC to maintain FL310. We climbed from about FL307 to FL310. First Officer disconnected autopilot and started turn to 090 and climbed back up to FL310.

Data retrieved from NASA's ASRS site 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.

B777 first officer reports being cleared to FL310 and initiating descent in VNAV. He is subsequently cleared to FL280 which is set in the MCP but the button is not pushed and the aircraft levels off at FL310. This is not immediately detected by ATC or the crew resulting in a conflict.