Date: 201502
Local time of day: 1201-1800
Location: SAT.Airport, TX
Flight conditions: VMC
Weather elements / visibility: Haze / Smoke; 10
Aircraft: Commercial Fixed Wing
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Cargo / Freight / Delivery
Flight phase: Initial Approach
Airspace: Class C SAT
ATC / advisory: Tower SAT
Reporter organization: Air Carrier
Reporter function: First Officer; Pilot Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Communication Breakdown; Confusion; Distraction; Human-Machine Interface
Second reporter function: Pilot Not Flying; Captain
Anomaly: Deviation - Altitude Excursion From Assigned Altitude; Deviation - Altitude Overshoot; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter CFTT / CFIT
Detector: Automation Aircraft Terrain Warning; Person Flight Crew
When detected: In-flight
Result: Flight Crew Became Reoriented; Flight Crew Returned To Clearance
Contributing factors: Human Factors
Primary problem: Human Factors

Narrative: On approach; cleared visual on vector just prior to base leg; autopilot engaged. Heading select used throughout base turn to about a 10 degree intercept to final. We got a frequency change to tower. I selected APP/LAND mode and autopilot began right turn toward LOC which was going to overshoot final. I disengaged autopilot and reversed turn to left and established a 10 degree intercept to final from overshoot; and inadvertently began a slight descent. I called for 'Flaps 22; gear down; before landing checklist.' As I was intercepting centerline (LOC); the PM instructed me to climb. As I began climb I looked at altimeter which was above 2000 ft. (MSL) and PM said we needed to climb back to the 1500 ft. AGL pattern altitude until intercepting GS. We climbed and joined GS and continued the approach to landing.Failure of PF to scan the radar altimeter and/or setting pattern altitude in alerter window. Poor VFR instrument scan. Failure of PF to make mental note of pattern altitude. Timing of frequency change had PM heads down. Good catch by PM shortly thereafter.


Second narrative: While maneuvering on a left base leg to a visual approach to runway 12R; Approach Control switched us to tower frequency. The Pilot Flying had disconnected the autopilot and was hand flying the aircraft. The slats and some flaps were extended at this time. I was heads down; making the frequency change on comm 1. I was heads down; and needed the frequency again; as a call for more flaps was made by the pilot flying. After switching the frequency; I looked up and noticed the radar altimeter showing below 1;500 feet AGL with a descent. I called out the error and commanded a climb; which was initiated by the Pilot Flying. The climb was already initiated; when terrain below us began moderately rising. This resulted in a 'Landing Gear' callout by CAWS. A moderate climb was completed back to 1;500 AGL and the base leg; final approach and landing were completed.For me; as Pilot Monitoring; being heads down longer than normal while changing frequencies and extending flaps; distracted me from Pilot Monitoring functions; delaying my recognition of the error. For the Pilot Flying; I suspect the MSL altitudes were primarily referenced on the PFD; not recognizing the SAT area has a higher elevation. (We had come from MEM).


Synopsis: An air carrier flight crew became distracted while hand flying the aircraft on final approach and inadvertently began a descent before intercepting the glideslope. The pilot monitoring caught the error and commanded a climb just as a 'Landing Gear' callout by CAWS alerted them to their altitude deviation.