6
$\begingroup$

In FAR/AIM, 5-3-8. Holding part, There is a sentence that says

(b) Outbound leg timing begins over/abeam the fix, whichever occurs later.

I got to know that the word 'over' is for parallel or teardrop entry. But I still can't understand the intention of 'whichever occurs later'.

Could anybody explain this more specifically?

$\endgroup$
  • $\begingroup$ "Over" would be appropriate to disambiguate what happens in parallel or teardrop entry. But I don't understand the "whichever occurs later" logic. The sentence makes most sense to me with the final word removed. $\endgroup$ – BowlOfRed Aug 14 '19 at 5:09
  • $\begingroup$ BowlofRed/ Thanks, now I realize the meaning of 'over'. Still the last sentence is obscure, so I modified my post a bit. $\endgroup$ – Student412 Aug 14 '19 at 6:12
5
$\begingroup$

The text is written that way to take into account the various type of holding entries. In case of a parallel or teardrop entry, the outbound leg starts after passing over the fix. In all other cases the outbound leg start after passing abeam the fix, following a turn that starts over the fix.

Case 1: Established in a holding pattern

So when established in a holding pattern, the outbound leg starts abeam the fix.

The sequence is:

  1. inbound leg
  2. pass over the fix
  3. turn outbound
  4. pass abeam the fix
  5. outbound leg
  6. turn inbound
  7. repeat from 1.

In this case it is clear that the time of the outbound leg should start when you pass abeam the fix, which occurs later in the sequence.

Case 2: Entry into holding pattern

diagram with holding entry procedures

Case 2.1: Parallel Entry into holding pattern

When entering the holding using a parallel entry ((a) in the diagram) the sequence is:

  1. fly to the fix
  2. pass over the fix
  3. turn outbound course
  4. outbound leg (on non-holding side)
  5. turn to inbound leg
  6. intercept inbound leg
  7. follow sequence for established in a holding pattern

In this case the timing of the outbound leg should start when you pass over the fix. From this, it follows that the outbound time will include the time spent in the outbound turn (3.).

Case 2.2: Teardrop Entry into holding pattern

When entering the holding using a teardrop entry ((b) in the diagram) the sequence is:

  1. fly to the fix
  2. pass over the fix
  3. turn outbound course
  4. outbound leg (30 degree into holding side)
  5. turn to inbound leg
  6. intercept inbound leg
  7. follow sequence for established in a holding pattern

In this case the timing of the outbound leg should start when you pass over the fix. From this, it follows that the outbound time will include the time spent in the outbound turn (3.).

Case 2.3: Direct Entry into holding pattern from holding side

When entering the holding using a direct entry from the holding side ((c) in the diagram, sector on the holding side) the sequence is:

  1. fly to the fix
  2. pass over the fix
  3. turn outbound
  4. pass abeam the fix
  5. outbound leg
  6. turn inbound
  7. follow sequence for established in a holding pattern

In this case it is clear that the time of the outbound leg should start when you pass abeam the fix, which is later in the sequence.

Case 2.4: Direct Entry into holding pattern from non-holding side

When entering the holding using a direct entry from the non-holding side ((c) in the diagram, sector on the non-holding side), you may not complete the turn before being abeam the fix. In that case the sequence is:

  1. fly to the fix
  2. pass over the fix
  3. turn outbound course
  4. outbound leg
  5. turn inbound
  6. follow sequence for established in a holding pattern

In this case it is clear that the time of the outbound leg should start when you pass over the fix. From this, it follows that the outbound time will include the time spent in the outbound turn (3.).

| improve this answer | |
$\endgroup$
0
$\begingroup$

It's nothing to do with the type of entry, it's down to your accuracy of flying. If you are flying accurately, you will pass directly overhead the holding fix, in which case you hit the stopwatch as you pass overhead. But if you fly slightly to the side, for whatever reason, then you hit the stopwatch as you pass abeam the fix as being a rough approximation of the overhead.

| improve this answer | |
$\endgroup$
  • 3
    $\begingroup$ How could you pass both over and abeam the fix (so requiring the "whichever occurs later" wording)? $\endgroup$ – Dannie Aug 14 '19 at 11:30
0
$\begingroup$

In a 2018 publication, "A Treatise on the Holding Pattern:Expelling the Myths and Misconceptions of Timing and Wind Correction", the complete mathematical solution of the generalized holding pattern problem was finally solved. The results are completely analytic and are valid for any wind direction and wind speed up to 99.99% of the aircraft true airspeed. The results show that the outbound time should start when the aircraft has crossed the fix and turned to the outbound heading. The analysis is valid for any constant rate of turn (standard, bank-limited, or specified). The solution provides the inbound wind correction angle, outbound heading and outbound time, which allows the aircraft to intercept the inbound course exactly at the point that satisfies the required inbound time or inbound distance (i.e. ATD) from the fix. Thus, it is no longer necessary to locate the abeam point. In the AIM (5-3-8), for cases where the abeam point cannot be determined, the recommendation is to start the outbound time when the outbound heading is reached, . When the windspeed ratio (wind speed/TAS) is greater than 1/3 with a quartering headwind, the shape of the track of the aircraft in the holding pattern is such that it is impossible to determine the abeam point. However, there is another property of the holding pattern solution that shows that if the outbound time is started at the point the aircraft has turned to the correct outbound heading, the outbound time is the same ,for a given relative wind angle measure from the inbound course, whether the aircraft is flying left (non-standard) or right(standard) holding patterns. If the time is started at the abeam point, the outbound times will be different when flying standard or non-standing holding patterns. The fact that abeam point does not need to be determined, reduces pilot workload during the hold.

| improve this answer | |
$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.