Date: 201311
Location: TUS.Tower, AZ
Flight conditions: IMC
Light: Daylight
Aircraft: Citation X (C750)
Operator: Fractional
Operating under: Part 91
Flight plan: IFR
Flight phase: Initial Approach
Airspace: Class C TUS
ATC / advisory: Tower TUS
Aircraft component: Tablet
Component problem: Design
Reporter organization: Fractional
Reporter function: Pilot Flying; Captain
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Human-Machine Interface; Confusion
Second reporter function: Captain; Pilot Not Flying
Anomaly: Deviation - Altitude Overshoot; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter CFTT / CFIT
Detector: Automation Air Traffic Control; Person Air Traffic Control
When detected: In-flight
Result: Air Traffic Control Issued Advisory / Alert; Flight Crew Executed Go Around / Missed Approach
Contributing factors: Aircraft; Chart Or Publication; Human Factors
Primary problem: Ambiguous

Narrative: Briefed the LOC BC 29R. There were rapid weather changing conditions. Originally weather was 3;800/5. We ended up flying to minimums. We briefed the correct minimums. Since I did not have the iPad in front of me I looked to the FMS for the next altitude to be set and asked that 2;990 be set. The Non-Flying Pilot set 2;990 which is the altitude in the FMS Database for the ASONE fix. MDA is 3;120. We had not gotten to 2;990 when Tower gave us a Low Altitude Alert and told us to check the altimeter setting. I immediately climbed approximately 150 FT and then called Missed Approach. We went missed and this time got vectors for the ILS. First of all there should be no altitude at ASONE fix or it should be changed to MDA. It is confusing and I feel a human factors issue. Secondly in the future I would look for and compare and brief that the altitude in the FMS is lower than the MDA altitude.


Second narrative: Approach changed from briefed ILS to LOC DME BC RWY 29 which was rebriefed. While stabilized and descending to altitudes on profile; the FMS has an altitude of 2;990 at ASONE fix. This altitude is NOT on the approach plate. Pilot flying requested 2;990 to be set because of it being shown on the FMS and I complied. I went back to the approach plate to confirm and my scan caught MDA of 3;120. As I was about to tell pilot we got a call from Tower advised us about an 'ALTITUDE ALERT.' We began an immediate climb and executed the missed approach. Terrain painting was negative and no voice systems activated. Events were happening quickly with many aircraft including military aircraft declaring 'MIN FUEL' due to rapid weather change. Additional information: about two hours later; when we were departing; Tower advised another aircraft on that same approach of a 'LOW ALTITUDE ALERT' and aircraft told the Tower of his altitude which was above MDA. If I did not make the point clear: [the aircraft's altitude was] the 2;990 that the FMS displayed.


Synopsis: A CE-750 flight crew; flying the LOC DME (BACK CRS) to Runway 12 initiated a missed approach when ATC advised of a low altitude alert.  Reporters advised they had entered the FMS displayed altitude at ASONE of 2;990 MSL which was lower than the MDA(H) of 3;120 MSL.