A temporary loss of communication with ATC and non standard clearances while flying the sunst RNAV S...

Narrative:

This event occurred during descent on the sunst RNAV arrival to las. I was pilot flying and the captain the pilot not flying. We had been cleared and descended to cross fuzzy at 16;000 ft and 250 KTS when I noticed; several miles outside of ipumy; that we hadn't heard from ATC in a while and were rapidly becoming too high to comply with the 11;000 ft and 230 KTS crossing at ipumy (we still had not yet been given the 'descend via' clearance). When we received no response to our inquiry to ATC we went back to the last assigned frequency and were told to switch to another frequency. When the captain checked in and advised of our altitude we were cleared to descend to 10;000 ft and to delete the restriction at ipumy. I selected open descent but; before we leveled off at 10;000 ft; ATC cleared us to 'descend via' the sunst RNAV arrival. I selected 8;000 ft in the altitude but forgot to push 'altitude' for a managed descent. I announced the next crossing; which was nipzo at 9;000 ft; but neither of us realized we were still in open descent. Shortly after passing 9;000 ft we received traffic advisory and both of us focused on this. The traffic was 2;500 ft below us; but this also contributed to our not noticing the altitude deviation. We realized we had gone approximately 500 ft below the nipzo crossing when ATC advised us. I deselected the autopilot and climbed back up to 9;000 ft and no other disruptions occurred. Several factors led to this event: the confusion and distraction from the lost communications; receiving a non-standard/out-of-the-ordinary clearance to descend to 10;000 ft rather than to 'descend via the sunst RNAV arrival;' and being distracted with a traffic advisory; all which took place during a high workload environment.to prevent this from happening again; I will be more alert and prepared to confirm automation when a change in descent clearance is given other than what we are used to receive in a multiple crossing RNAV arrival. I would also be quicker to query ATC when I notice approaching our next descent point rather than waiting to query after well crossing it and being further behind and being put in a catch up mode.

Original NASA ASRS Text

Title: A temporary loss of communication with ATC and non standard clearances while flying the SUNST RNAV STAR to LAS resulted in two deviations from charted crossing restrictions for the reporting A320 flight crew.

Narrative: This event occurred during descent on the SUNST RNAV arrival to LAS. I was pilot flying and the Captain the pilot not flying. We had been cleared and descended to cross FUZZY at 16;000 FT and 250 KTS when I noticed; several miles outside of IPUMY; that we hadn't heard from ATC in a while and were rapidly becoming too high to comply with the 11;000 FT and 230 KTS crossing at IPUMY (we still had not yet been given the 'descend via' clearance). When we received no response to our inquiry to ATC we went back to the last assigned frequency and were told to switch to another frequency. When the Captain checked in and advised of our altitude we were cleared to descend to 10;000 FT and to delete the restriction at IPUMY. I selected open descent but; before we leveled off at 10;000 FT; ATC cleared us to 'descend via' the SUNST RNAV arrival. I selected 8;000 FT in the altitude but forgot to push 'altitude' for a managed descent. I announced the next crossing; which was NIPZO at 9;000 FT; but neither of us realized we were still in Open descent. Shortly after passing 9;000 FT we received traffic advisory and both of us focused on this. The traffic was 2;500 FT below us; but this also contributed to our not noticing the altitude deviation. We realized we had gone approximately 500 FT below the NIPZO crossing when ATC advised us. I deselected the autopilot and climbed back up to 9;000 FT and no other disruptions occurred. Several factors led to this event: the confusion and distraction from the lost communications; receiving a non-standard/out-of-the-ordinary clearance to descend to 10;000 FT rather than to 'descend via the SUNST RNAV arrival;' and being distracted with a traffic advisory; all which took place during a high workload environment.To prevent this from happening again; I will be more alert and prepared to confirm automation when a change in descent clearance is given other than what we are used to receive in a multiple crossing RNAV arrival. I would also be quicker to query ATC when I notice approaching our next descent point rather than waiting to query after well crossing it and being further behind and being put in a catch up mode.

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.

Attributes
ACN	1059714
Time
Date	201301
Local Time Of Day	1201-1800
Place
Locale Reference	L30.TRACON
State Reference	NV
Environment
Flight Conditions	VMC
Light	Dusk
Aircraft 1
Make Model Name	A320
Operating Under FAR Part	Part 121
Flight Phase	Descent
Route In Use	STAR SUNST3
Flight Plan	IFR
Component
Aircraft Component	Autoflight System
Person 1
Function	First Officer Pilot Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Person 2
Function	Pilot Not Flying Check Pilot
Qualification	Flight Crew Air Transport Pilot (ATP)
Events
Anomaly	ATC Issue All Types Deviation - Altitude Crossing Restriction Not Met Deviation - Altitude Overshoot Deviation - Procedural Published Material / Policy Deviation - Procedural Clearance

A temporary loss of communication with ATC and non standard clearances while flying the sunst RNAV STAR to las resulted in two deviations from charted crossing restrictions for the reporting A320 flight crew.