Cessna Citation Mustang (C510)
Flight Crew Air Transport Pilot (ATP); Flight Crew Flight Engineer; Flight Crew Flight Instructor
Flight Crew Last 90 Days 150; Flight Crew Total 20000; Flight Crew Type 250
Aircraft Equipment Problem Less Severe; Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Clearance
Air Traffic Control Issued Advisory / Alert; Flight Crew Became Reoriented; Flight Crew Returned To Clearance
Aircraft; Human Factors
I was level at 4;000 feet tracking to PDZ VOR with autopilot engaged in NAV mode and altitude hold. ATC then issued a climb clearance to 6000 feet. I placed 6000 in the altitude alert window and engaged a Vertical Speed Mode of +1000 FPM. Immediately after receiving the climb clearance; ATC advised me that I could expect Radar Vectors to POM then to track outbound on the 295R. I was then given another climb clearance to 7000 feet. I then placed 7000 in the Altitude Alert Window. With this previously issued 'Expect' clearance; I then began to construct that routing in the MFD Routing so that when officially cleared to fly that route; I could then engage the appropriate Roll NAV Mode. While I was building the expected routing; ATC contacted asked if we were experiencing any problems because he showed me descending. Upon ATC query; I refocused my attention to the vertical path of the aircraft. At that point; I observed that indeed we were descending instead of climbing and the Autopilot was not engaged in any vertical mode but was tracking in Heading Mode. I intervened by disconnecting the Autopilot and manually initiated a climb to 7000.I do not know why or how the Autopilot dropped out of the Vertical Speed Mode. It was ATC's observation and communication that caused me to correct the situation. However; I do believe my exuberance to 'pre-load' the 'Expect' routing clearance; caused me to become fixated on the programing of that route and I failed to continue to monitor the immediate and actual aircraft progress.While the moment was a period of higher flight deck workload; the expectation and trust in automation should never create a complacent attitude that prevents required aircraft monitoring. Less reliance on automation and more attention to aircraft 'state' monitoring would have prevented this occurrence.
When given a climb from 4000 to 6000 feet and; quickly thereafter; issued an 'expect' lateral routing; the pilot of a CE-510S failed to monitor the aircraft's vertical track while pre-programming the expected new routing. ATC enquired as to why the aircraft was descending vice climbing as cleared. The reporter included a wise commentary on the need; especially for single pilot operations; to always pay greater attention to 'aircraft 'state' monitoring' even while engaged in required FMS programming.