Definition
An FAA Advisory Circular that provides guidance to pilots and aircraft operators using portable electronic devices, such as tablets, as Electronic Flight Bags (EFBs) in place of paper aeronautical charts and documents under Part 91. It outlines acceptable practices for evaluating, using, and managing EFBs, including suitability testing, backup requirements, and operational considerations.
Plain English
It is the FAA's official guidance document that tells private and general aviation pilots how to use a tablet or similar device as a digital replacement for paper charts and manuals.
Context Anchor
You may see AC 91-78 in discussions about electronic flight bags, paper chart replacement, and what a pilot must consider before relying on a tablet in the cockpit.
Derivation
Advisory Circulars are FAA documents organized by subject. The '91' refers to 14 CFR Part 91 (general operating and flight rules), and '78' is simply the sequential number assigned within that subject series.
Why Pilots Care
It determines whether a pilot's electronic device setup meets FAA standards, directly affecting what equipment can be used for navigation and instrument procedures.
Intuition Check
Do not read AC 91-78 as a regulation that automatically gives permission for every tablet use. It is FAA guidance that helps a pilot meet responsibilities that still come from the regulations and from safe operating practice.
Example Sentence 1
Before switching from paper charts to a tablet, the pilot reviewed AC 91-78 to make sure her setup met the FAA's recommended practices.
Example Sentence 2
Following the recommendations in AC 91-78 allowed the flight crew to transition fully to electronic charts without carrying paper backups.