Date: 201206
Local time of day: 0601-1200
Location: ZZZZ.Airport, FO
Flight conditions: IMC
Light: Daylight
Aircraft: Medium Transport
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Initial Approach
ATC / advisory: Tower ZZZZ
Aircraft component: MCP
Component problem: Improperly Operated
Reporter organization: Air Carrier
Reporter function: First Officer; Pilot Not Flying
Human factors: Training / Qualification; Workload; Time Pressure; Situational Awareness; Distraction
Anomaly: Deviation - Altitude Crossing Restriction Not Met; Deviation / Discrepancy - Procedural Clearance; Inflight Event / Encounter CFTT / CFIT
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Took Evasive Action
Contributing factors: Company Policy; Human Factors; Procedure; Weather
Primary problem: Human Factors

Narrative: We had thoroughly briefed the approach for the VOR/DME-2 Runway 13 before commencing the approach. The current weather included a scattered layer of clouds reported at 1;500 FT AGL and good visibility. We had begun the 10 DME arc to intercept the final approach course and were stepping down in altitude as depicted on the approach. The pilot flying had briefed the approach as a Continuous Angle Non Precision Approach (CANPA) and had determined a descent rate of 800 FPM once we passed the 8.0 DME position on the final approach course. We had leveled at 2;000 FT prior to reaching the 8 DME fix and the pilot flying set the descent altitude in the altitude selector on the Flight Guidance Control Panel FGCP since we had agreed to monitor our progress with regards to both altitude and distance as there was an altitude constraint of 1;500 FT at the 5 DME fix from the VOR. However; during the segment from 8 DME to 5 DME; the VOR CDI began to swing well to the left of center without any change in aircraft heading. The pilot flying and pilot not flying were both focused on the VOR needle and neglected to notice the airplane descending below the 1;500 FT floor as the airplane had not yet reached 5 DME . By the time the deviation was noticed; the aircraft had descended to 900 FT MSL at the 5 DME point. By this point we had been in VMC for approximately 400-500 FT. The pilot flying continued on a 'visual' approach since we had acquired the airport and landed without further incident. The threats encountered were a rushed descent as ATC had left us high until a relatively close distance to the airport. This shortened the time available to prepare for the approach. A second threat was an unfamiliar approach to an airport that the pilot not flying had never flown into before. It was also the first time than the pilot not flying had flown a CANPA approach since completing initial new-hire training. Further threats were numerous step downs on the approach; a lack of recommended altitudes and distances on the approach plate; and finally; the VOR signal that began wandering for no apparent reason during the final portion of the approach which served as a major distraction to the flight crew. An error on the part of both pilots was focusing too much attention on the VOR CDI deflection and neglecting the vertical progress of the aircraft which led to an undesired aircraft state of being 600 FT below the altitude restraint at the FAF. As the pilot not flying; I should have been more vigilant to monitor the descent progress of the aircraft. I could have asked the pilot flying what he would have liked me to focus on: troubleshooting the faulty VOR signal; or monitoring the aircraft's progress. After discussing the event; the pilot flying and I both decided that the appropriate course of action that SHOULD have been taken was to set the altitude to 1;500 FT until passing the 5.0 DME fix THEN setting the MDA in the altitude selector. This would have arrested the aircraft's descent at 1;500 FT preventing us from descending below the minimum altitude for that segment of the approach. For future approaches similar to this example I plan to verify each step-down with the pilot flying and verify that it is set appropriately in the altitude selector so as to prevent another incident similar to this one.




Synopsis: A Medium Transport flight crew on a Constant Angle Non Precision Approach (CANPA) set the Mode Control Panel at the Decision Altitude. After becoming distracted they descended early; 600 FT below the Final Approach Fix altitude.