Date: 201601
Local time of day: 1201-1800
Location: MDW.Airport, IL
Flight conditions: IMC
Weather elements / visibility: 10
Light: Daylight
Aircraft: Citation II S2/Bravo (C550)
Operator: Air Taxi
Operating under: Part 135
Flight plan: IFR
Mission: Passenger
Flight phase: Initial Approach
Airspace: Class C MDW
ATC / advisory: TRACON C90
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Not Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP); Flight Crew Flight Instructor; Flight Crew Multiengine; Flight Crew Instrument
Human factors: Situational Awareness
Anomaly: Aircraft Equipment Problem Less Severe; Deviation - Altitude Overshoot; Deviation / Discrepancy - Procedural Clearance; Inflight Event / Encounter CFTT / CFIT
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Became Reoriented; Flight Crew Returned To Clearance
Contributing factors: Aircraft; Human Factors
Primary problem: Human Factors

Narrative: Second in Command (SIC) was Pilot Flying (PF); Pilot in Command (PIC) was Pilot Not Flying (PNF) on specific leg of trip. PF engaged Autopilot (A/P) shortly before reaching vectoring altitude of 3;000ft MSL. Upon receiving vectors to intercept final approach course and clearance to commence ILS 31C at MDW - was given alt restriction from Chicago approach control of 'maintain 2;500 ft until RUNTS; contact MDW tower at RUNTS.' PNF read back full clearance with instructions to maintain 2;500 ft. Company SOPs were complied with - including setting alt alert; A/P alt select; and standard call out and verification of alt restriction to PF. PF acknowledged clearance while allowing A/P control aircraft to intercept final approach course. Descent from 3;000ft MSL brought aircraft into solid IMC layer present to reported ceiling of 1;300ft AGL. PNF was 'inside of A/C' tending to PNF flight duties including: briefing approach; running checklists; and contacting FBO for services. After tasks were completed; PNF noticed that A/C had descended below MDA of 2;500ft MSL outside of RUNTS to approximately 2;000ft MSL in steady descent. Deviation from assigned alt was alerted to PF who quickly recovered to assigned alt of 2;500ft MSL outside of RUNTS. Recovery was initiated before any alt deviation report was received by Chicago approach control. After altitude was recovered and a stabilized approach was assured at a safe distance away from the FAF-ILS 31C approach was continued according to standard IAP requirements. A thorough debrief was initiated after flight was completed and aircraft was shutdown. At time of discovery of alt deviation by PNF (PIC); it was noticed that the PF (SIC) was actually inside of aircraft fixated on EFB; unaware that the A/P had not captured the selected altitude as assigned. Had the PF been monitoring the aircraft properly while the PNF was tending to 'inside/head down' flight duties - the altitude deviation could have been avoided. The PF (SIC) admitted to reliance on A/P for completing flight as desired. As a 3;000+hr pilot with 1000+hrs in type - the PF (SIC) should have been aware of the hazards of reliance upon A/P in critical phases of flight. It should also be noted that the PNF (PIC) should have verified proper level off at assigned altitude while commencing PNF duties. The reliance on automation and trust that only one pilot of two pilot crew should verify that aircraft is operating in accordance to normal ops and assigned clearances are two factors that will be reviewed and mitigated by this crew on future flights.




Synopsis: CE-550 Captain; with the First Officer flying; reported a descent below the assigned altitude of 2;500 feet during approach. The First Officer had programed the autopilot to capture 2;500 feet which it did not; but he did not notice due to being fixated on the EFB.