Holding Pattern Entry Boundaries
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For this holding pattern,
What are the degree boundaries for the Direct Entry, Parallel Entry, and Teardrop Entry?
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The primary boundary is between direct entry and the non-direct entries. This line is 20° rotated from perpendicular from the heading that defines the hold. Ignoring this small rotation for a minute direct entry is called for through half of the circle. For example if it was a hold on heading 360 then approaching from the south ±90°.
Except there is a turn immediately after flying over the fix, standard to the right, so they make the direct entry more restricted on the “inside of the turn” by 20° and less restricted on the “outside of the turn” by 20°. So if you have to make a right turn to align with the holding heading and then another right turn after passing the fix it’s restricted you have to approach within 70° aligned with the holding heading. Alternatively if it’s a left turn to align with the hold heading and a right turn after passing the fix you are allowed to be up to 110° misaligned.
For example you have a left hold reference 165° so if you approached on heading 255° (from 75°) it would take a left square turn to align with 165° and then begin a left turn. That’s too tight so you couldn’t do a direct entry. You could from more aligned (heading 235° or less) you would have to make a 70° turn or less to align with 165° so that’s OK. Approaching from the west you have to make a turn so it’s permissible to have a heading of up to 75° (from 255°) which means up to a 110° right turn to align with 165°. Direct entry is if you have to make a 90° turn or less to the holding direction ±20° depending on if you are on the inside or outside.
The rest of the circle is the non-direct entry. This is split by the extended line through the fix along the reference heading. The oval track of the holding pattern lies entirely on one side of this divide. If approaching on the same side as the pattern, do a parallel entry. If approaching on the opposite side of the pattern, do a teardrop.
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The primary boundary is between direct entry and the non-direct entries.
https://www.americanflyers.net/aviationlibrary/instrument_flying_handbook/images/chapter_10_img_13.jpgThe Figure 10-6 that you showed seems to be for a right turn holding pattern with inbound 270°, where the direct entry boundary is between 20° and 200°. My figure (copied from Red Dog’s Chart Tutorial, p. 39) showed a left turn holding pattern with inbound 345°. So are you saying that the direct entry boundary for my figure is also 20° and 200°?
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It will differ depending on the inbound to the fix and the direction of the hold. If you get confused put you right hand (for a right hold) or your left hand (for a left hold) over the pic. Align the inbound track with your forefinger and the angle made between your forefinger and thumb is the 70 degree teardrop sector.
There is also 5 deg of latitude for each sector, ie if you are within 5 deg you can choose.
EDIT
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Hi jc1!
@jc1:
For this holding pattern,
What are the degree boundaries for the Direct Entry, Parallel Entry, and Teardrop Entry?
Talking about entry sectors, for info, (and AFAIK … I might be wrong and depends on country), this is (usually) not really applied by fighter pilots, even in IFR flight, because they can easily bank more than a “standard rate turn” and stay into the protected area of the procedure. Most of time, they fly the procedure in a simpler way
…Maybe the fly that way in IFR, but for sure, in tactical conditions (hold before the Push) they go the simplest way
But it is anyway good to know how to do things “academically”.
Correct me if I am wrong.
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It will differ depending on the inbound to the fix and the direction of the hold. If you get confused put you right hand (for a right hold) or your left hand (for a left hold) over the pic. Align the inbound track with your forefinger and the angle made between your forefinger and thumb is the 70 degree teardrop sector.
Thanks. That helped to visualize the entry sectors. To be more precise, I played around with it and came up with these two formulas that seem to work with any radial/turn combination for a holding fix. If this ain’t right, what’s wrong?
Right turn hold, 165° Radial (could be any radial)
Add 90° plus 20° to the Inbound Radial to get a marker for one end of the direct sector. 345° + 90° + 20° = 95°
Other end of the line for the direct sector is reciprocal of 95°…… 275°
Add 70° for Teardrop sector 275° + 70° … 345°
Add 110° for Parallel sector 345° + 110°… 95°Left turn hold, 165° Radial (could be any radial)
Subtract 90° minus 20° from the Outbound Radial to get a marker for one end of the direct sector. 165° - 90° - 20° = 55°
Other end of the line for the direct sector is reciprocal of 55°…… 235°
Subtract 70° for Teardrop sector 235° - 70° … 165°
Subtract 110° for Parallel sector 165° - 110°… 55°This is what the figures look like after the formulas are applied.
Right Turn Hold, 165 RadialLeft Turn Hold, 165 Radial
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That’s right. I described the boundary as the 3 o’clock-9 o’clock line but skewed 20° based on the turn. I hoped that would make the construction make sense from a “what were they thinking when they made it” way instead of rote memorization. I guess you could formulate a rule like right hand +110 -70 and left hand -110 +70 from the hold course.
Often you are inside the airplane approaching the fix and your perspective is likely to be of what the hold course looks like as you approach it. If you imagine the inbound leg is a big arrow floating in the sky you are cool if you approach it from the back. If you looking at the arrow from the side (more than 70° from the butt) you have to ask if you are inside or outside of the turn. After 110° misaligned it’s too sharp a turn no matter what and you gotta do an indirect.
Once it’s known an indirect is called for then I ask myself if I’m on the pattern side or not. If I’m looking at the right side of the arrow (and the hold is right turns) it means I’m on the pattern side so parallel. If I’m looking on the left side of the arrow (right turn hold) then I’m on the non-pattern side so I do teardrop.
