Definition
A document, approved by the aircraft's certifying authority and incorporated into the airplane flight manual, that lists external secondary airframe and engine parts which may be missing for flight, along with any associated operating limitations and performance corrections.
Plain English
An approved list that tells the pilot which small external parts of the airplane can be missing and still allow the airplane to be flown, and what limits apply when they are.
Context Anchor
Pilots encounter the CDL during preflight or before takeoff when deciding whether an airplane may be flown with a missing panel, fairing, cover, or similar external part.
Derivation
Configuration refers to how the aircraft is physically put together. Deviation means a departure from that standard build. So a Configuration Deviation List is literally a list of approved departures from the standard physical configuration of the airplane.
Why Pilots Care
It lets crews determine whether a takeoff can continue or must be rejected when the aircraft is not in standard configuration.
Intuition Check
Do not read CDL as a casual checklist or a pilot’s judgment call. It is an approved list for that aircraft, and if the missing item is not allowed by the CDL, the airplane should not be flown in that condition.
Example Sentence 1
During preflight, the captain noticed a small wing-to-fuselage fairing was missing and consulted the CDL to confirm the airplane could be dispatched with a reduced takeoff weight.
Example Sentence 2
During the rejected takeoff drill, the instructor asked whether the CDL permitted the observed configuration.