Definition
An in-flight condition in which the aircraft's two-way radio communication with air traffic control is lost, requiring the pilot to follow specific lost communication procedures published in the Federal Aviation Regulations and on the relevant approach or en route charts.
Plain English
It means the radio isn't working well enough to talk to or hear ATC, so the pilot has to follow a set of pre-agreed rules for what to do next instead of getting instructions over the air.
Context Anchor
Seen in instrument flying material and communication failure discussions, especially when describing what a pilot should do after losing contact with air traffic control.
Derivation
Short for 'radio failure.' The 'R' stands for radio, and 'DOF' is a shortened form of the word that follows. It is used as a quick written tag in ATC and flight planning notes.
Why Pilots Care
Knowing the RDOF altitude lets a pilot comply with a lost-comm radar vector without guessing the safe climb height.
Intuition Check
Do not read RDOF as a type of navigation fix or clearance. In this context, it simply flags a radio failure situation.
Example Sentence 1
After the avionics issue on climbout, the crew declared RDOF and continued the flight under the lost communication rules in the regulations.
Example Sentence 2
The approach plate lists the RDOF value so the crew knows the minimum altitude to maintain during a lost-comm radar departure.