How to fly a procedure turn

Sometimes you arrive at a fix pointing the wrong way for the approach. A reversal procedure turns you around in a known piece of sky and puts you on the inbound track, established and stable.

All of them start the same way. You cross the fix, track outbound on a published track, and time the leg. This trainer always times it, one to three minutes, which is what the ICAO figure shows and what works with an NDB as well as with a VOR. Then you reverse.

Your exercise starts half a minute before the fix, established on the track and tracking toward it, with the panel already set. That is 1 NM at 120 kt and 2 NM at 240, because half a minute is half a minute whatever you have set the speed to. So you fly the station passage first: watch the flag go from TO to FROM, and start the clock as it flips. Getting established is not the exercise, the reversal is.

The turn side is the manoeuvring side, the side a chart marks with a barbed arrow. Everything happens on that side of the track.

The one you will see most. At the end of the outbound leg, turn 45 degrees away from the track toward the manoeuvring side. Hold that heading for one minute, then turn 180 degrees the other way.

You roll out cutting the inbound track at 45 degrees, which is a comfortable angle to intercept. Turn onto the inbound track as the needle comes alive, and track back to the fix.

One minute on the 45 degree leg is the category A and B timing, which covers the speeds this trainer flies. Faster aircraft are given a little longer.

Same outbound leg, no straight bit in the middle. Turn 80 degrees away from the track, and as soon as you get there roll straight into a 260 degree turn the other way.

Those two numbers are not arbitrary. Eighty out and 260 back is a net 180 degrees, so you come out pointing at the fix with no intercept to judge, which is why some pilots prefer it. Flown at one radius it leaves you about a third of a radius to the side of the track, close enough to simply turn back onto it as you roll out. The price is that you are turning continuously for nearly a full minute.

A base turn looks similar and is a different animal. The outbound track is not the reciprocal of the inbound track: it diverges by a few degrees. Then a single sweeping turn of a little more than 180 degrees brings you onto the inbound track.

How far it diverges is not a free choice, and there is a number for it: 36 divided by the outbound time in minutes.

• One minute outbound: 36 degrees.
• Two minutes: 18 degrees.
• Three minutes: 12 degrees.

It is a reciprocal because of where it comes from. A turn of about 180 degrees moves you sideways by two turn radii, so the outbound leg has to end that far off the inbound track for the turn to arrive on it. The longer the leg, the less divergence that takes.

Both the leg and the turn radius grow with speed, so the same base turn works over a range of speeds. Not all of them: above about 170 kt the turn is bank limited, the radius grows faster than the leg, and you sail through the track. Fly one at 120 kt and again at 250 with SHOW SOLUTION on, and you will see it.

Start the timer as you pass the fix, or abeam it if you can tell, whichever comes later. That is where the outbound leg begins, and it is why the exercise puts you a mile short of the station rather than already outbound: the station passage is part of the job.

Wind matters more here than in a holding, because you fly the reversal only once and there is no second lap to fix it. The same rules of thumb apply, and they are a suggestion rather than a law:

• Take the crosswind in knots, halve it, and use that as your wind correction angle on the inbound track.
• A headwind outbound means you cover less ground, so the reversal ends up closer to the fix. A tailwind pushes it further out.

The honest check is the map. Fly it, then use SHOW SOLUTION: the amber track is the procedure drawn to scale for the speed you flew, so your white trail should sit on it. Where it does not is where the timing or the wind correction was off.

Then hide it and fly the next one on the instruments alone.

A reversal exists to turn you around: you arrive at the fix pointing away from the runway, and the procedure gets you onto the final approach course pointing at it. If you already arrive lined up, there is nothing to reverse, and the chart says so with NoPT on that route. Fly a procedure turn on a NoPT segment and you are doing something the controller does not expect.

The other way round matters more. If the chart depicts a reversal on your route and no NoPT, it is not optional: it is part of the procedure, and the protected airspace is drawn assuming you fly it. Being vectored onto final, or being told "straight in", are the clearances that remove it.

Which reversal is a chart decision, not yours. A procedure turn barb means you may fly any of the three shapes on the depicted side. A drawn base turn or a specific 45/180 track means that one, as drawn.

Two limits define the protected area. The turn is made on the side the chart shows, and only that side: the barb points into it. And the whole manoeuvre stays within the charted distance from the fix, commonly ten nautical miles, sometimes less where terrain is close. Both are on the plan view; both are there because the other side and the space beyond were never surveyed.

The distance is the one that catches people out at speed. One minute outbound at 90 kt is a mile and a half; at 180 kt it is three, plus the turn, plus the run in. Add a tailwind outbound and a ten mile limit is closer than it looks. Faster aeroplanes shorten the outbound leg, or use the 80/260, which needs less room lengthwise.

45/180 is the default. One turn off, a timed leg, one turn back, a 45 degree intercept. The timed leg is what lets you fix the wind: stretch or shorten it and the intercept still works.

80/260 uses no straight leg at all, so it takes less distance along the track and it is the one to reach for when the ten mile limit is tight or the aeroplane is fast. The cost is that there is nothing to adjust: the two turns are the whole manoeuvre, and a strong wind shows up as a poor intercept.

The base turn is different in kind. The outbound track is not the reciprocal of the inbound one; it diverges by an angle the designer chose, and one turn brings you round onto final. It is drawn, not chosen, and the divergence is worked out from the outbound time: 36 divided by the minutes.

Outbound timing starts over the fix, or abeam it if the turn from the arrival takes you wide, whichever comes later. It does not start when you roll wings level; that adds the whole turn to the leg and pushes the reversal towards the limit.

On the 45/180 the second clock starts when you roll out on the 45 degree heading, and it runs one minute in category A and B aeroplanes, a little longer in the faster categories. Then the 180. If the inbound needle is alive before the 180 is complete, the wind pushed you in; if it is dead for a long time after, the wind pushed you out. Adjust the 45 degree leg next time, not the turn.

Turning the wrong side. The barb is small and the habit is strong. Read it out on the way in: "turn on the north side", before the fix, not after.

Starting the clock on roll out. See above. The leg is timed from the fix, and the difference is a full turn's worth of distance towards the limit.

Flying a reversal on a NoPT route. Not dangerous by itself, but nobody is expecting it, and it costs the slot behind you.

Descending too early. The procedure turn altitude is a minimum for the whole manoeuvre, and the next step down is usually allowed only once established inbound. Established means the needle inside the last two dots and staying there, not the first flicker.