B737 flight crew reported a low altitude alert on approach to oak due to miscommunication on the cle...

Attributes
ACN	1455206
Time
Date	201706
Local Time Of Day	1801-2400
Place
Locale Reference	OAK.Airport
State Reference	CA
Environment
Flight Conditions	Mixed
Light	Night
Aircraft 1
Make Model Name	B737 Next Generation Undifferentiated
Operating Under FAR Part	Part 121
Flight Phase	Initial Approach
Flight Plan	IFR
Person 1
Function	Captain Pilot Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Last 90 Days 365 Flight Crew Type 10000
Person 2
Function	First Officer Pilot Not Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Events
Anomaly	ATC Issue All Types Deviation - Altitude Overshoot Deviation - Procedural Clearance Inflight Event / Encounter CFTT / CFIT

Narrative:

While on downwind for an approach to oak runway 30; ATC gave a turn to base and a descent from 4000 ft to what I thought was 2400 ft. I thought the first officer read back 2400 ft; and as I was hand flying I asked him to set 2400 ft in the altitude window. Descending through 2900 ft MSL ATC advised us we were below our assigned altitude of 3400 ft. I immediately climbed the aircraft to 3400 ft and remarked to the first officer that I thought we were cleared to 2400 ft. ATC then said we were below the minimum vectoring altitude for the sector. Published altitudes on the ILS 30 approach are 2700 ft for wuvon and 2000 ft for mitoe (FAF). As we were being vectored to intercept final near wuvon; the 2400 ft altitude didn't seem unreasonable. At no time did we receive a GPWS warning. Both pilots had terrain selected on their map displays; and no terrain conflicts were noted.

Original NASA ASRS Text

Title: B737 flight crew reported a low altitude alert on approach to OAK due to miscommunication on the cleared altitude.

Narrative: While on downwind for an approach to OAK Runway 30; ATC gave a turn to base and a descent from 4000 ft to what I thought was 2400 ft. I thought the FO read back 2400 ft; and as I was hand flying I asked him to set 2400 ft in the altitude window. Descending through 2900 ft MSL ATC advised us we were below our assigned altitude of 3400 ft. I immediately climbed the aircraft to 3400 ft and remarked to the FO that I thought we were cleared to 2400 ft. ATC then said we were below the minimum vectoring altitude for the sector. Published altitudes on the ILS 30 Approach are 2700 ft for WUVON and 2000 ft for MITOE (FAF). As we were being vectored to intercept final near WUVON; the 2400 ft altitude didn't seem unreasonable. At no time did we receive a GPWS warning. Both Pilots had TERRAIN selected on their map displays; and no terrain conflicts were noted.

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.

B737 flight crew reported a low altitude alert on approach to oak due to miscommunication on the cleared altitude.