Island VOR/DME Fix and Drift Correction
You are navigating a twin turboprop at FL180 in still-air cruise TAS 260 kt, heading 085°M with magnetic variation 6°W. The OBS is set on a distant VOR (radial 270) and the CDI shows full-scale fly-right deflection; the TO/FROM flag reads FROM. The DME reads 84 NM. Your planned track to the next waypoint is 090°M and you need to cross the 090°M radial of the same VOR. Wind at FL180 is forecast 300°/45 kt. You have 40 minutes of usable fuel reserve above destination minimum and a 12-minute buffer for the fix.
1. Determine your current position relative to the VOR and the track error, then state the heading correction to regain the planned track.
Read the worked answer
CDI full-scale fly-right with FROM means the selected radial (270) is behind you to the left; you are on the 270 radial but displaced to the side where the needle commands a right turn. With OBS 270 and FROM, the aircraft lies on the 090°M radial side of the station only if the flag were TO. Here the FROM flag confirms you are outbound from the VOR on the 270 radial side; full-scale deflection means you are roughly 10° off the selected radial, so your actual bearing from the VOR is about 280°M, i.e. you are on the 280 radial at 84 NM. Planned track 090°M; actual track made good is roughly 100°M, giving a track error of ~10° right. To regain track, apply a closing correction of twice the error: turn left 20°, heading 065°M (070°M if you want a 1.5× correction with a slower intercept). Confirm with a second fix before the radial crossing.
2. Estimate the wind correction angle and groundspeed on the new heading, and decide whether the 12-minute fix buffer is adequate.
Read the worked answer
Wind 300°/45 kt, TAS 260 kt, heading ~070°M. The wind is roughly 50° off the nose to the left. Crosswind component ≈ 45 sin50° ≈ 34 kt; headwind component ≈ 45 cos50° ≈ 29 kt. WCA ≈ arcsin(34/260) ≈ 7.5°, so the required heading is about 077°M to hold 070°M track (or 072°M for 070°M heading). Groundspeed ≈ 260 − 29 ≈ 231 kt. At 231 kt, 84 NM takes about 22 minutes; the 12-minute buffer is therefore insufficient if you must also fly the intercept. You should request a direct routing or reduce the intercept angle to save time; the buffer is only adequate if the remaining distance to the radial is under about 45 NM.