Commercial Fixed Wing
Flight Crew Air Transport Pilot (ATP)
Situational Awareness; Other / Unknown
Aircraft Equipment Problem Less Severe; Deviation - Altitude Overshoot; Deviation / Discrepancy - Procedural Clearance
Flight Crew Became Reoriented; Flight Crew Returned To Clearance
Aircraft; Human Factors
Following a missed approach to Juneau Airport; we were executing a second LDA Z [X] Runway 8 approach into Juneau; via the SSR VOR transition.  The flight was operating in VMC on top of a cloud layer.  After leveling at 7;000 feet; a descent was initiated between SSR VOR and LYNNS to 5;600 feet; by selecting 5;600 in the altitude alerter and selecting vertical speed mode on the AFCS.  The altitude alerter did not chime; and the plane continued in a descent through 5;600 feet.  Both pilots were momentarily looking outside; and when I glanced back inside to scan the altimeter; the plane was descending through 4;900 feet.  I immediately responded by bringing the power levers to climb power and selecting a climb mode on the AFCS to return the plane to 5;600 feet.  The flight remained in VMC during the altitude deviation.
Air carrier pilot flying the LDA X Runway 8 at JNU reports descending below the 5;600 foot MEA on the SSR 007 degree radial after setting 5;600 in the MCP and initiating a vertical speed descent. No chime was heard and the deviation was not noted until 4;900 feet and corrected.