Simultaneous Non-Precision Approaches

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Cristóbal Catalán
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Simultaneous Non-Precision Approaches

Post by Cristóbal Catalán » Thu Jun 28, 2018 1:12 pm

I was going over through some of the old S3 training material to keep some retention on the theoretical knowledge and I was wondering the following:

Take for example you are working P80 and are providing radar services to two IFR Skyhawks, one being 123AB and 321CD, both headed to Hillsboro. 123AB wants the VOR/DME-C approach and 321CD wants the NDB-B approach. They are both at the same speed and distance from the field, south and north respectively.

In my head, the answer would be 'no', but could you clear both Skyhawks for both the NDB-B and the VOR/DME-C approach, provided that the last requires a circle-to-land maneuver? Would it be required of the Approach controller to let them in one at the time, or perhaps ask one of the aircraft if they can accept the other's approach and follow them in?

Thanks,
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Frank Miller
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Re: Simultaneous Non-Precision Approaches

Post by Frank Miller » Thu Jun 28, 2018 2:45 pm

Great question! I think you can certainly clear the two aircraft for the respective approaches if you are assured of maintaining separation (including once you turn them over to tower). Both are circling approaches, so I don’t see why that makes a difference. I think you face two challenges.

1. Both aircraft may arrive at roughly the same time. This risks creating a problem for tower, assuming poor visibility (though obviously you need at least ceilings above the circling minima). I’m assuming both will land on 13R, the VOR/DME-C arrival will likely circle south (e.g. right traffic) and follow the NDB-B arrival in (which is essentially a straight in). Tower cannot extend the VOR/DME-C arrival on the circling approach as the pilot must maintain visual contact with the runway at all times.. So you may be creating quite a little problem for your tower controller if the two aircraft seem likely to arrive simultaneously. Maybe visibility is good enough, however, to cope with this—-or even to switch them to a visual approach (where you can maintain separation visually) or have them cancel IFR altogether once they have the field. Still, none of this is advisable. So let’s assume both pilots stay IFR and the field is at minimums for the two approaches.

2. Both approaches have the same missed approach procedure and no alternate (CORRECTION: Actually, the NDB-B approach DOES have an alternate—-I misread the chart when I first posted this reply). If you don’t assign the alternate, this makes matters far worse as clearing them for the approach automatically clears them to fly the missed. Two aircraft climbing to 3000 and heading to UBG to hold. Potentially ugly.

So.... what to do?

Well, you could put them on the same approaches in sequence, as you’ve suggested. Or you could apply some speed control to create some separation. Or you could clear them for the approach with a restriction on the time to cross the IAF. That last option might be accompanied by an approval for S turns 10 degrees either side of their course to the fix to allow them to control the time they arrive at the fix.

But isn’t there another option?

Why not give them their requested approaches but create the separation you need with a brief hold? Clear one for the approach, and clear the other to hold over the IAF (either the BANKS NDB or the UBG VOR) with an expected clearance time of +3-5 minutes. Once the aircraft you want to be #1 in sequence is turned inbound from its procedure turn, release the #2 from the hold and let them proceed outbound and make their procedure turn. That creates the necessary separation. For two Skyhawks, you actually shouldn’t need more than 2 minutes (see, e.g., 7110.65 para 6-7-5 for Minima Intervals for timed approaches). And you may find that you can skip the hold entirely if the necessary separation is created while the two pilots fly their approaches——many things can make the two planes fly at different speeds, including winds aloft, aircraft performance and flying technique. The hold gives you a way to create a safety margin.

I’d be interested to hear what others have to say on this topic, but that’s my best guess at the answer.

Frank

Richard Teves
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Re: Simultaneous Non-Precision Approaches

Post by Richard Teves » Fri Jun 29, 2018 12:37 pm

Frank you've got it. The terminology of simultaneous approaches is normally left for parallel runways at bigger airports that have reduced distances between runways.
Simultaneous approaches allow aircraft to approach runways independently of adjacent parallel runways. Aircraft may pass or be passed by aircraft on the adjacent approach path, but must maintain standard separation behind aircraft on the same approach path. The standards for simultaneous approaches are generally contained in FAA Order 7110.65R, paragraphs 5-9-7 and 5-9-8. (Borrowed from someone much smarter than I am)

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