Refer to figure.
We must calculate the Ground Speed for the leg WTP B - WPT C:
TAS: 135 kt; W/V: 340/20; True Track: 270°

Solving from Heading (HDG) & Ground Speed (GS), knowing WV, TAS and required track.

1. Set wind direction to 340° under the "TRUE HEADING" index at the top.
2. Set the center point on the True Airspeed (TAS) of 135 kt.
3. Mark the wind velocity 20 kt down from the centre point.
4. Initially, set the True Track to 270° under the "TRUE HEADING" index.
5. Note that this heading would result in 8°L drift and a track of 262°.
6. Reduce the heading value under the index until the heading minus the drift gives a track of 270°. This occurs at a heading of 278° with 8°L drift.
7. The groundspeed for this track is approximately 127 kt.

Sector time from WPT B to WPT C:

• Sector Time = Distance / Ground Speed
  Sector Time = 53 NM / 127 kt = 25 min

Accumulated time to DEST:

• Accumulated time until WPT B + Sector Time WPT B - WPT C + Sector Time WPT C - DEST = 23 min + 25 min + 4 min = 52 min