Definition
A navigation procedure used to determine the time and distance from a VOR or NDB station by flying a heading 90° to the bearing of the station, timing how long it takes for the bearing to change by a set number of degrees (commonly 10°), and applying a simple formula to calculate minutes and miles to the station.
Plain English
A method that uses a stopwatch and a small change in bearing to figure out how many minutes of flying time, and how many miles, you are from a ground-based navigation station.
Context Anchor
Used in navigation and instrument flying when working with a radio magnetic indicator and a radio navigation station.
Why Pilots Care
Provides a backup method to estimate position and arrival time when DME or GPS is unavailable.
Grounding Statement
If the bearing pointer moves quickly, the aircraft is relatively close to the station; if it moves slowly, the aircraft is farther away.
Intuition Check
A time-distance check is not just checking a clock and a mileage number. In this context, it means estimating time and distance from a station by measuring how quickly the station’s bearing changes.
Example Sentence 1
With no DME on board, the pilot performed a time-distance check off the VOR and calculated they were about 18 minutes from the station.
Example Sentence 2
Using the time-distance check, the crew confirmed their groundspeed matched the planned value.