Most EFBs incorporate a feature called Airport Moving Map, a display that provides a constantly changing view of an airport’s runways, taxiways and structures to help pilots identify and anticipate the airplane’s location on the surface. GPS technology makes it possible for the moving map to show pilots their actual position (own ship) on the airport surface.
The FAA has varying certification levels for Electronic Flight Bags based on the technical complexity of the EFB and the types of data it is intended to display. Devices able to show data both on the ground and in the air, including an Airport Moving Map that identifies the aircraft’s position, are subject to the highest, or “Class C” standards. These standards were set with particular regard for the strictest in flight requirements.-- From Press Release: http://www.faa.gov/news/fact_sheets/news_story.cfm?newsId=8409
Title 14 CFR Part 91.21: “Portable Electronic Devices”
FAA Advisory Circular 92.21-1B: “Use of Portable Electronic Devices”
Title 14 CFR Part 91.503: “Flying equipment and operating information”
FAA Advisory Circular 120-76A: “Guidelines for the Certification Airworthiness, and Operational Approval of Electronic Flight Bag Computing Devices”
The key text in the use of the any EFB in lieu of paper is:
CFR Part 91.21: “Portable Electronic Devices”. Under Part 91.21, the operator or Pilot In Command may authorize the use of a PED during any phase of flight.
AC 91-78, “Use of Class 1 or Class 2 Electronic Flight Bag (EFB)”, provides aircraft owners, operators, and pilots operating aircraft under Title 14 of the Code of Federal Regulations (14 CFR) part 91,
with information for removal of paper aeronautical charts and other documentation from the cockpit through the use of either portable or installed cockpit displays.
According to this AC, Class 1 and Class 2 EFB can be used during all phases of flight operations in lieu of paper reference material when the information displayed meets the following criteria:
The EFB system does not replace any system or equipment (e.g. navigation, communication, or surveillance system) that is required by 14 CFR part 91.
The EFB system on board the aircraft displays only precomposed or interactive information which are functionally equivalent to the paper reference material which the information is replacing or is substituted for.
The interactive or precomposed information being used for navigation or performance planning is current, up-to-date, and valid, as verified by the pilot.
The operator complies with requirements of 14 CFR part 91, § 91.21 to ensure that the use of the EFB does not interfere with equipment or systems required for flight.
A good article that puts in perspective: EFB Guidance Library