An air carrier crew on the lax riivr arrival began deviating around thunderstorms without ATC cleara...

Narrative:

Descending on the riivr two arrival into lax we were navigating to gramm intersection as we were deviating around an area of weather to the east. There were numerous cells in the area that would need to be navigated around. At altitude; we could visually see a clear route from our present position to gramm. However; when the controller issued a descent to us; it became evident that our descent path would potentially take us through an area of weather between our present position and gramm. Due to the weather in the area and the amount of traffic descending into the la basin; the controller was task saturated and the radio frequency was experiencing numerous blocked calls associated with the large number of clearances issued and the requests for deviation around the weather by arrival aircraft. As it became apparent that we would need to deviate to the left of course; we tried to get clearance from the controller; but with no luck. At one point the controller asked all aircraft to suspend their transmission in order that he could control the situation. Unfortunately; we needed his ear immediately. As we neared the cell; I told the controller that we needed an immediate left turn. With no response; we started a left turn and I announced to the controller that we were turning left. Upon hearing my intention; he advised us not to turn left yet to which I responded that doing so would put us through the cell. At that point we stopped the turn. We had a TCAS target to our left that was not at our altitude to which we presume the controller immediately gave an altitude clearance; followed immediately with a clearance for us to turn left and increase our descent rate. We were able to miss the cell and since we had no TCAS warning; we presume that the controller had maintained proper separation. Although this was a stressful situation for the controller and us; the controller kept his cool and performed his duties in a professional manner. His quick recognition of the potential conflict resulted in a positive resolution of the situation. I think that the dynamic nature of developing weather and high-density traffic conditions makes incidents such as this one; to be quite stressful and have a very real potential for compromising safety.

Original NASA ASRS Text

Title: An air carrier crew on the LAX RIIVR Arrival began deviating around thunderstorms without ATC clearance because the TRACON Controller was task saturated; but eventually cleared them.

Narrative: Descending on the RIIVR TWO Arrival into LAX we were navigating to GRAMM intersection as we were deviating around an area of weather to the east. There were numerous cells in the area that would need to be navigated around. At altitude; we could visually see a clear route from our present position to GRAMM. However; when the Controller issued a descent to us; it became evident that our descent path would potentially take us through an area of weather between our present position and GRAMM. Due to the weather in the area and the amount of traffic descending into the LA basin; the Controller was task saturated and the radio frequency was experiencing numerous blocked calls associated with the large number of clearances issued and the requests for deviation around the weather by arrival aircraft. As it became apparent that we would need to deviate to the left of course; we tried to get clearance from the Controller; but with no luck. At one point the Controller asked all aircraft to suspend their transmission in order that he could control the situation. Unfortunately; we needed his ear immediately. As we neared the cell; I told the Controller that we needed an immediate left turn. With no response; we started a left turn and I announced to the Controller that we were turning left. Upon hearing my intention; he advised us not to turn left yet to which I responded that doing so would put us through the cell. At that point we stopped the turn. We had a TCAS target to our left that was not at our altitude to which we presume the Controller immediately gave an altitude clearance; followed immediately with a clearance for us to turn left and increase our descent rate. We were able to miss the cell and since we had no TCAS warning; we presume that the Controller had maintained proper separation. Although this was a stressful situation for the Controller and us; the Controller kept his cool and performed his duties in a professional manner. His quick recognition of the potential conflict resulted in a positive resolution of the situation. I think that the dynamic nature of developing weather and high-density traffic conditions makes incidents such as this one; to be quite stressful and have a very real potential for compromising safety.

Data retrieved from NASA's ASRS site as of April 2012 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	969848
Time
Date	201109
Local Time Of Day	1201-1800
Place
Locale Reference	LAX.Airport
State Reference	CA
Environment
Light	Daylight
Aircraft 1
Make Model Name	Large Transport Low Wing 2 Turbojet Eng
Operating Under FAR Part	Part 121
Flight Phase	Descent
Route In Use	STAR RIIVR
Flight Plan	IFR
Person 1
Function	Pilot Not Flying Captain
Qualification	Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Last 90 Days 145 Flight Crew Total 19850 Flight Crew Type 8600
Person 2
Function	First Officer Pilot Flying
Events
Anomaly	ATC Issue All Types Deviation - Track / Heading All Types Inflight Event / Encounter Weather / Turbulence

An air carrier crew on the lax riivr arrival began deviating around thunderstorms without ATC clearance because the TRACON controller was task saturated; but eventually cleared them.