|Holding Patterns - Download zip file of lesson here (400k)
Even though we never get assigned holds in FS (and rarely in real life), its a good skill to understand and be able to apply. Holds are very difficult to teach in writing, but hopefully, with the use of illustrations, youll gain an understanding of how to properly execute a hold. Holds are basically circular patterns which keep aircraft in a small space, allowing ATC to keep traffic orderly and seperated. In IFR training, we commonly practice holding over a VOR. Holds can take place in many places however. We can hold over NDBs, we can hold at DME distances on a specific VOR radial, we can hold at airway intersections, we can even hold at GPS waypoints with real-life GPS. Youll frequently see holds plotted on approach plates and STARs. Well simplify our discussion by just holding over a VOR and well also use a no-wind situation to start. Ill discussion wind correction afterwards. Holds require that you be VERY familiar and comfortable with the operation of the VOR and interpretation of the NAV equipment. Because VORs have 360 radials, we can be assigned to hold on any of those. For our example, lets say that we have been told to hold east on the 090 radial of the Vero Beach VOR. So, were going to head toward the VOR along the 090 radial, which means well be flying 270 TO. Standard holds are accomplished with right-hand turns, so when we pass over the VOR, we will make a 180 degree standard-rate turn to the right and head back away from the VOR for a specified time. We will then make another 180 degree standard-rate turn back towards the VOR. This will result in a racetrack pattern as depicted below.
Youll notice that we have an inbound(heading towards the VOR) leg and an outbound(away from the VOR) leg. Ive noted that the inbound leg should be 1 minute long. Above 14,000ft, the inbound leg should be 1 1/2 minutes long. So, how are we going to make sure our inbound leg is 1 minute long? Well, in a no-wind situation, our time outbound should equal our time inbound. So, lets start as we pass the VOR inbound. We start our right 180 degree turn. As we reach the abeam(the holding fix) point, the TO/FROM flag will flip and we will start our timer. Well then fly along until the timer indicates 1 minute and then begin our right-hand turn back inbound. If we make sure the turns are standard rate, we would roll right out onto the 090 radial(270 TO). At that point, we will again start our timer and see how long it takes us to reach the VOR. We do whatever it takes to make our inbound leg 1 minute long. If we found out that it only took us 50 seconds to fly the inbound leg, we would have to modify the outbound leg by adding 10 seonds to it, flying outbound for 1 minute and 10 seconds. Now, lets talk a bit about how we navigate each leg. Since were holding along the 090 radial, we will set 270 TO and TRACK the course inbound, keeping the needle centered. Now, as we approach the VOR, the needle will become more sensitive and start to move off-center. Dont chase it! Just continue to fly your heading until the TO/FROM indicator changes and then begin your turn. Now, as we turn outbound, what are we turning to? Well, since were not tracking a radial outbound, we just turn to the recipricol heading. So, in this case, we would turn to a heading of 090. The outbound leg is a dead-reckoning leg, we just fly a heading for a specified time(1 minute). So, like I said, if it was a no-wind situation, it would look just about like above.
Now, lets talk about how we enter a hold. We dont just magically appear along the inbound leg to start the hold. There are three enteries we can make, called "direct", "teardrop", and "parallel". The way we determine which entry to make is by our heading to the holding fix. Lets say that we have been given the holding instructions discussed above and were southwest of the VOR. We would proceed direct to the VOR by turning our HSI needle or OBS until it centered. Lets say that it centers with an indication of 050 TO which would mean were along the 230 radial. Our next step is to determine where we are in relation to the actual hold that were going to fly. Take a look at the diagram below:
You can see the various sectors for each entry. The sectors are detemined by adding 110 degrees to the holding course on the non-holding side and subtracting 70 degrees from the holding course on the holding side. Our holding course is the 090 radial, so if we add 110 degrees, we get the 200 radial on the non-holding side and by subtracting, we get the 020 radial on the holding side. We said above that we were proceeding inbound along the 230 radial, so by looking at the diagram, we see that we should make a teardrop entry. If we were inbound on the 330 radial, wed make a parallel entry and so on. Now, lets take a look at what it looks like in the plane and from above. Ill be flying the situation we discussed above. In the first turn, I didnt fly outound long enough, so I overshot the inbound leg. After weve looked at it, Ill discuss how to fly each entry.
OK, so now youve seen a teardrop entry. But how did I do it? Well, its pretty simple. When you pass the holding fix, turn to a heading of 30 degrees less than your outbound leg heading. Since the outbound leg heading is 090, I turned to 060 degrees. You just fly outbound for 1 minute as usual and then turn inbound. A direct entry is even easier. You simply fly as depcited. Once you cross the holding fix, you just begin your turn to the outbound leg heading. The parallel entry is the most difficult. As you pass the fix, you turn to the outbound leg heading, but youre flying parallel to the holding course on the NON-HOLDING side. After youve gone out for 1 minute, you then make a LEFT-HAND turn all the way back until youre heading direct to the VOR. Once you cross it, you proceed with the hold as normal. A picture is shown below.
OK, now lets talk breifly outbout flying in wind conditions and making crosswind corrections. On your first outbound leg in the hold, its all going to be guess work since you havent had a chance to establish a wind correction angle inbound yet. But, lets assume were heading inbound along the 090 radial with a wind from the north at 20 knots. Because we have a crosswind, were going to have to establish some crosswind correction to maintian course. I found that it was about 12 degrees to the right. So, since the outbound leg is a dead-reckoning leg, how are we going to compensate. Well, as we turn upwind, were going to have a decreased groundspeed and as we make our turn back downwind, were going to have an increased groundspeed. So, to account for that, were actually going to have to fly AWAY from the course as we proceed outbound. To do this, we will DOUBLE our crosswind correction on the outbound leg. So, since I said it was 12 degrees, we will have a 24 degree correction outbound, or an outbound heading of 66 degrees. Below is a picture of what a properly executed hold with wind correction looks like. It appears odd, but it is the proper procedure.
Well, I hope this has helped you to gain an understanding of holding procedures. Ill mention a few other things. The maximum holding speed for all propellor-driven aircraft is 175KIAS. For civil turbojet aircraft, it is 200KIAS up to 6,000ft, 230KIAS up to 14,000ft, and 265KIAS above 14,000ft. For military turbojet aircraft, its 230KIAS except for a few specific aircraft. Also, as I said above, normal holding take place with right-hand turns. You may be asked to hold with left-hand turns at times. In fact, the only time I was ever asked to hold outside of the training environment, I was asked to make left-hand turns. If they dont specify, you make right-hand turns. If you were instructed to hold east on the 090 radial of the VRB VOR at 7DME, you would follow the exact same procedure as above except that you would make your turns when you reach 7DME, not at the VOR. You should report to ATC when you enter the hold as well. You should be given an "expect further clearance" time so that you know about when you should be done holding or when to leave the hold in case of a loss of communications. As I said, holding can be complicated and a lot of people take a long time to pass this step in instrument training. Take your time, study the diagrams, and let me know if you have any quesitons. Good luck!