Skylane 182/RG Turbo Skylane/RG
Flight Crew Private; Flight Crew Instrument
Flight Crew Last 90 Days 35; Flight Crew Total 1080; Flight Crew Type 30
Workload; Human-Machine Interface
Deviation - Altitude Excursion From Assigned Altitude
Flight Crew Returned To Clearance
Aircraft; Human Factors
Departed with IFR flightplan for SBY with a substantial rerouting.  Due to wanting to get launched as we were being met at destination; and knowing the rerouting would cost extra time; I decided to enter only the first intersection (WEARD) in the flight plan and program the balance enroute.  This plan was compromised by not having familiar paper charts at hand (current charts were available on an iPad which was available to me; expired paper charts were in the airplane; but not at hand); and hesitation programming the G1000 under the pressure of a hand-flown climb with a request for expedited climb from NY Approach.  At the time I had about 23 hour in type.  I had reached the cleared altitude of 5;000 direct WEARD with LHY next; and was in VMC close to cloud bottoms.  Either shortly before or possibly shortly after WEARD intersection; I noticed an altitude deviation (approximately 300 FT low).  About the same time my clearance via LHY was amended to Direct ETX; which put me back closer to the planned route. The deviation was immediately corrected without complaint from ATC; but certainly not something I am familiar with; having successfully flown approximately 600 hours IFR in a C172 equipped with KLN94 and KAP140 over the past six years. Contributing factors:- lack of experience with G1000 (at the time about 23 hour; about ten of those solo)- failure to enter the reroute before departure increased workload in visual climb- some unfamiliarity with iPad charts that were available (Foreflight) - failure to activate autopilot altitude hold immediately on reaching cleared altitude.Correctives:- add G1000 experience before flying in complex airspace- take time to do flight plan entry before departure - use autopilot for both climb and enroute when IFR.  I am certain that this would not have happened had I been flying my previous aircraft even though it did not have altitude hold on its autopilot.  My familiarity with programming the KLN94 would have meant a much lower workload at the time.  The altitude deviation likely had no safety implication; but it could have.  After another ten hours solo with the G1000 on that same trip; I am already much more confident with its operation.
A C182 pilot had an altitude deviation while attempting to program a G1000 which had not been completed prior to takeoff due to time constraints.