Flight crew reported descending below charted altitude on an instrument approach to destination airp...

Attributes
ACN	1750268
Time
Date	202007
Local Time Of Day	0601-1200
Place
Locale Reference	BGR.TRACON
State Reference	ME
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Make Model Name	Small Transport
Operating Under FAR Part	Part 135
Flight Phase	Initial Approach
Route In Use	Other Established on approach
Flight Plan	IFR
Person 1
Function	Pilot Flying Captain
Qualification	Flight Crew Flight Instructor Flight Crew Commercial Flight Crew Multiengine Flight Crew Instrument
Experience	Flight Crew Last 90 Days 200 Flight Crew Total 8000 Flight Crew Type 4000
Person 2
Function	First Officer Pilot Not Flying
Qualification	Flight Crew Multiengine Flight Crew Instrument Flight Crew Air Transport Pilot (ATP) Flight Crew Flight Instructor
Experience	Flight Crew Last 90 Days 74 Flight Crew Total 6600 Flight Crew Type 390
Events
Anomaly	Deviation - Altitude Excursion From Assigned Altitude Deviation - Procedural Clearance Inflight Event / Encounter CFTT / CFIT

Narrative:

The sic (second in command) and I thoroughly briefed the approach; RNAV GPS 22 approach to bhb. We were cleared to cross carda at 3000 and cleared for the approach. Autopilot was on. I selected approach mode and do not recall if I selected VNAV. We dialed the altitude down to the missed approach altitude. Between carda and becra; ATC called with cancelling instructions. The sic had his head down writing the instructions. I looked over to see what the sic was doing.when the aircraft turned at becra; I compared the altitude to the chart and noticed immediately we were descending through 1700. I knew something wasn't right so I leveled the wings; arrested the descent and asked the sic to help me sort this out. Initiated a climb and at that exact moment ATC asked our altitude. Our altitude should have been 2100. Sic called missed approach. We climbed to 3000 on a heading per ATC instructions. We reloaded the approach and came back to a successful approach and landing. We did not get any taws (terrain awareness and warning system) alerts.

Original NASA ASRS Text

Title: Flight crew reported descending below charted altitude on an instrument approach to destination airport.

Narrative: The SIC (Second in Command) and I thoroughly briefed the approach; RNAV GPS 22 approach to BHB. We were cleared to cross CARDA at 3000 and cleared for the approach. Autopilot was on. I selected Approach mode and do not recall if I selected VNAV. We dialed the altitude down to the Missed Approach Altitude. Between CARDA and BECRA; ATC called with cancelling instructions. The SIC had his head down writing the Instructions. I looked over to see what the SIC was doing.When the aircraft turned at BECRA; I compared the altitude to the chart and noticed immediately we were descending through 1700. I knew something wasn't right so I leveled the wings; arrested the descent and asked the SIC to help me sort this out. Initiated a climb and at that exact moment ATC asked our altitude. Our altitude should have been 2100. SIC called missed approach. We climbed to 3000 on a heading per ATC instructions. We reloaded the approach and came back to a successful approach and landing. We did not get any TAWS (Terrain Awareness and Warning System) alerts.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.