Definition
FAA Advisory Circular 90-109, titled 'Transition to Unfamiliar Aircraft,' provides guidance for pilots and instructors when moving to an aircraft they have not flown before, with particular emphasis on experimental, amateur-built, and technically advanced aircraft. It outlines recommended training, transition planning, risk assessment, and proficiency considerations to help pilots safely adapt to differences in handling, systems, performance, and avionics.
Plain English
An FAA guidance document that explains how a pilot should prepare and train when stepping into a type of aircraft they have not flown before, so the change is handled safely rather than by trial and error.
Context Anchor
Seen in aircraft checkout and transition training discussions, especially when an instructor is preparing a pilot to fly a new type, model, or category of aircraft.
Derivation
An Advisory Circular (AC) is a non-regulatory FAA publication offering guidance on a topic. The number 90-109 identifies it within the FAA's numbering system, where the 90-series covers general operating procedures.
Why Pilots Care
Following its recommendations lowers the chance of errors or accidents when a pilot first operates a new aircraft.
Intuition Check
Do not read “transition” here as just a casual change or a paperwork step. In this context, it means a planned training process for safely moving into an aircraft with differences that can affect the flight.
Example Sentence 1
Before checking out the club's new RV-7, the instructor built a transition syllabus based on the recommendations in AC 90-109.
Example Sentence 2
AC 90-109 emphasizes performing a thorough preflight and systems briefing prior to the first flight in any new airplane.