Military Bomber
Flight Crew Flight Engineer; Flight Crew Air Transport Pilot (ATP); Flight Crew Flight Instructor; Flight Crew Multiengine; Flight Crew Instrument
Flight Crew Last 90 Days 10; Flight Crew Total 12000; Flight Crew Type 30
Situational Awareness
Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Clearance
Air Traffic Control Issued New Clearance; Flight Crew Became Reoriented; Flight Crew Returned To Clearance
Human Factors; Weather
While enroute; we were using XM (satellite radio) radar and ADS-B (Automatic Dependent Surveillance-Broadcast) radar data to deviate around weather. Due to the limitations of these delayed data systems; we were also attempting to remain in VMC conditions to allow for real time deviations. During this time we were changing altitude to aid in this (successful) effort. At one point; we allowed the aircraft to deviate slightly more than 300 feet. We eventually obtained a block altitude to provide us with the required flexibility. We should have obtained the block altitude earlier or have stayed on our assigned altitude until we obtained an amended clearance.
Pilot reports an altitude deviation while attempting to avoid weather using XM (satellite radio) and ADS-B (Automatic Dependent Surveillance-Broadcast) radar data.