Date: 201203
Local time of day: 1201-1800
Location: ZZZ.Airport, US
Weather elements / visibility: Turbulence
Aircraft: Commercial Fixed Wing
Operator: Air Carrier
Operating under: Part 121
Flight phase: Initial Approach
Airspace: Class C ZZZ
ATC / advisory: TRACON ZZZ
Aircraft component: Altimeter
Component problem: Improperly Operated
Reporter organization: Air Carrier
Reporter function: Pilot Not Flying; Captain
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Communication Breakdown; Confusion; Workload
Second reporter function: Pilot Flying; First Officer
Anomaly: ATC Issue All Types; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Clearance; Inflight Event / Encounter CFTT / CFIT
Detector: Automation Air Traffic Control; Automation Aircraft Terrain Warning; Person Air Traffic Control; Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Issued Advisory / Alert; Flight Crew Became Reoriented; Flight Crew Returned To Clearance
Contributing factors: Weather; Human Factors
Primary problem: Human Factors

Narrative: While on descent; I tuned in the ATIS early as there was known weather in the area. Upon receiving the ATIS I commented on how low it was 29.39. Descending I dialed the altimeter into the standby at which time we received an excessive amount of radio static due to weather (common problem in this aircraft while in clouds). We switched radios and although a small adjustment; it does take some getting used to. We had received deviations around weather; altitude changes; heading changes; and due to the radio that was acting up; it became a high work load. Somewhere in there I had switched on the lights; we ran our flows; and then did the checklist. Moving forward; we were given 3;000 until established; then a frequency change at which point the Controller read the altimeter for good measure as 30.39 or so I heard (I do not know at this point) and so I read back the frequency and altimeter setting of 30.39 which also happened to be our flight number. The Controller said nothing and we switched frequencies. At this point we could see the ground and were both starting to get the sense something was not right. Our radar altimeters were reading wrong as we approached and we were trying to figure out what it was when we received a gear warning that matched the RA that was reading wrong. ATC then asked us if we had been advised of a low altitude alert by the previous guy which we had not. He then started to read the altimeter when we realize that although it was set correctly in the standby; somehow we had both set the primaries to 30.39 instead of 29.39 missed it despite the checklist. We immediately corrected our altitude and there were no further issues; nor any conflicts.If something does not feel or sound right should always query ATC. When I read back the altimeter and flight number is sounded odd to me and I though it was simply because they were the same.


Second narrative: While on descent we were handed off to another ATC frequency and the Controller stated the altimeter setting was 30.39. Shortly there after we were cleared to 3;000 FT for the ILS; when we leveled off at 3;000 we received a too low gear warning and noticed the radar altimeter was at 1;100. At that time ATC advised us of a low altitude alert and that the altimeter setting was 29.39 not 30.39. The setting was corrected and we climbed to the proper altitude and landed. How often is your flight number the altimeter setting too? With thunderstorms in the vicinity of the airport my concern was getting the aircraft on the ground before the weather impacted the field. We should have verified the altimeter setting with the next Controller since it was similar to our call sign.


Synopsis: Air Carrier flight crew reports getting their flight number and the altimeter setting confused during descent resulting in descent 1;000 FT below assigned altitude. The error is detected by ATC and a GPWS flap warning nearly simultaneously.