Monday, October 30, 2006
Creating holding clearances
So there you are, trucking along in your trusty bug smasher (or trusty sim), tracking inbound on the 360° radial, when without warning your instructor sadistically says, “Devise a holding clearance from your present position that will require a parallel entry for a left-hand holding pattern.”
Many instrument students do very well figuring out holding entries in an intuitive fashion. However this approach tends to break down when you are on the dispensing end of a holding clearance rather than the receiving end. Although at first glance it may seem a bit daunting, once you have your secret decoding ring, it’s remarkably easy to do.
The secret decoding ring system works when the airplane is traveling to a VOR (or GPS waypoint). Let’s take the situation shown above, traveling towards the VOR. Remember when you were studying for your instrument rating and your instructor drew out the classic diagram for determining holding entries?
The trick in creating holding clearances is to use this same diagram and overlay it on the DG or HSI. Let’s say you are tracking inbound on the 360° radial as shown in the first figure, and you want to create a holding clearance that will force a teardrop entry for a standard (meaning right-hand) holding pattern. To do this, take the pattern formed by the red lines in the above figure and superimpose it on the DG or HSI, with the inbound leg being the radial on which you are tracking inbound.
Because it is a right-hand holding pattern, tilt the horizontal line up about 20° or so on the right-hand side of the DG or HSI. The radial on which you are tracking inbound forms the vertical line. Taken together, these two lines delineate the three regions for hold entries. The small pie-shaped section is for teardrop entries – any radial selected in this region will call for a teardrop entry. (Hint – remember “Tiny Tears”) The larger pie-shaped segment defines the parallel entry region. Any radial in this region will call for a parallel entry. Everything below the tilted line calls for a direct entry. So in this case, if you want to create a holding clearance that will force a teardrop entry for a right-hand pattern, any radial between about 190°and 240° will work very nicely. So the holding clearance could be
Hold southwest of VOR on the 210° radial right-hand turns EFC
If you want to create a holding clearance for a left-hand pattern, just tilt the left-side of the horizontal line up rather than the right side. Let’s say you want to create a holding clearance that will call for a parallel entry for a left-hand holding pattern. Again, superimpose the two lines on the DG or HSI, but this time since a left-hand pattern has been specified, tilt the left side of the line up about 20° or so, as shown below.
The 240° radial lies right in the middle of the parallel entry region. So a holding clearance could be:
Hold southwest of VOR on the 240° radial left-hand turns EFC
Creating hold clearances for your student is really a very simple matter once you know this little trick. Try out a few for yourself.
Direct entry for either left-hand or right-hand hold could be:
Hold northeast of VOR on the 030° radial EFC
Teardrop entry for left-hand hold could be:
Hold southeast of VOR on 150° radial left-hand turns EFC
Parallel entry for left-hand hold could be:
Hold southwest of VOR on 210° radial left-hand turns EFC
Parallel entry for right-hand hold could be:
Hold east of VOR on 090° radial right-hand turns EFC
And there you have it – the secret decoding ring for creating holding clearances for your student. And yes, it works equally well for teaching holding entries to your student. The only caveat is that you must be tracking towards the waypoint in order for this method to work.