Holding Procedures — Page 214, Lesson 292

Right, let's pick this up with the ATC side of holding. We've covered the pattern geometry and the entry procedures, so now we're looking at how the controller actually talks to you, and how you fly the hold under their instructions. First, the clearance to join. Because a holding pattern sits inside controlled airspace and is used by controlled flights, ATC — usually the approach controller — will pass you a clearance to enter it. That clearance has to specify four things: the location of the hold, the details of the holding pattern unless they're routinely published, the holding level, and any special requirements. So you'll hear something like "G-CD hold at OX FL50 expected approach time 1020." That's the fix, the level, and the expected approach time. The pilot's readback is "Hold OX FL50 1020 G-CD." Then, once you've actually joined and are established, you report: "Oxford Approach G-CD is established in the hold at FL50." Now, a critical operational point: you must ensure the aircraft is level at the holding level at least 5 NM before reaching the holding fix. That's a hard requirement — you don't arrive at the fix still descending. Once you've acknowledged the clearance, the controller will not expect to hear from you again until you've completed the joining procedure and are established in the pattern. Next, descending in the hold. When the level below you becomes vacant, the controller will re-clear you to the lower level. You acknowledge, and you immediately commence descent. There's a note here I want you to remember: a "shuttle" is a climbing or descending manoeuvre in a holding pattern. So the controller might say "G-CD shuttle in the hold to FL40." Your readback is "Leaving FL50 descending to FL40 G-CD," and when you arrive you report "G-CD level FL40." Then, departing the hold. At the appropriate time, the controller instructs you to commence the instrument procedure. It's usual to leave a holding pattern at the fix, but where radar is used, the Approach Radar controller may vector you from any position in the pattern. A typical clearance would be "G-CD advise when ready to commence the procedure." You reply "Ready to commence the procedure G-CD." Then the controller gives you the full clearance: "G-CD set the Oxford QNH 1003, clear NDB/DME approach runway 01, report turning inbound at 2000 ft." Your readback: "1003 set clear NDB/DME runway 01 wilco G-CD." There's one more departure case — timed approaches. Under certain circumstances, the controller clears you to depart the holding pattern at a specific time to commence the procedure. In that case, you adjust the holding pattern leg lengths so you depart from overhead the holding fix as close as possible to that stated clearance time. That's the whole point of varying your leg lengths — to hit that time. Now let's move to obstacle clearance. The instrument procedure designer ensures that the MOC — that's the Minimum Obstacle Clearance — is applied throughout the holding area. The MOC is 300 m, or 600 m in mountainous terrain. That clearance applies to the holding pattern itself and any adjacent airspace you'd use during a joining procedure. The size of the holding area depends on four factors: the nature of the pattern, the type of aircraft using the hold, adjacent airspace requirements, and the maximum holding altitude. Surrounding the holding area is a buffer zone, 5 NM wide. Within that buffer, the MOC decreases from full MOC at the boundary with the holding area down to zero at the extremity. So to tie it together: you have the holding area with full obstacle clearance, and around it a 5 NM buffer where that clearance tapers off to nothing. That's why you stay inside the pattern — outside the holding area, your protection is gone. That's the ATC and obstacle clearance side of holding.