B737 Undifferentiated or Other Model
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 120; Flight Crew Total 9207; Flight Crew Type 1610
Situational Awareness; Distraction
Aircraft Equipment Problem Less Severe; Deviation - Altitude Undershoot; Deviation / Discrepancy - Procedural Clearance
Flight Crew Returned To Clearance; Flight Crew Became Reoriented
Human Factors; Aircraft
Arriving from the oceanic sector into the SF Bay Area. I was both Pilot Flying (PF) and PIC. My iPad; used for approach chart data; froze. I could not scale or change charts. OAK (destination) had originally reported calm wind and 10 sm visibility and I was going to use the RNAV-Y 28L. The updated weather placed TRW over the airport and the wind was 15 gusting to 35; visibility 1 sm in heavy rain; so I was trying to shift to the ILS 30. As it was a round trip to OAK; we had three pilots in the cockpit and the other 2 had functioning iPads. I switched with the third pilot in the jump seat and had a functioning iPad quickly. This is our home base; we are all VERY familiar with the approach; but wanted it displayed to follow proper SOP's.As we crossed the OSI VOR; the Pilot Monitoring (PM)/SIC pointed to the altitude alerter which he had set to 6;000 feet per received NORMAL clearance. I did not realize that we were still at 7;000' and ATC had called a second time telling us to descend. There was no immediate conflict. No evasive maneuvering was taken or noted by any aircraft or ATC. We descended as instructed but may have delayed our descent by 30 seconds due to my distraction with the iPad.Subsequent to this; I contacted Jeppesen; the manufacturer of the software used in the iPad. They noted it was a known problem; they were working on a revision and provided a workaround in the meantime. The workaround was transmitted that evening to all company pilots to prevent further problems until a software fix is released.
B737 Captain reported undershooting his altitude clearance when he was distracted by a malfunctioning iPad.