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I am studying procedure design manuals (TERPS, PBN 8260.58A manual, ICAO PANS-OPS 8168 manual etc.) and I haven't found any guidelines concerning altitude constraints that can be imposed on a waypoint.

Take, for example, JFK's DEEZ FIVE departure. CESID has an "AT or ABOVE 2500" altitude constraint. Is there a reason that an altitude constraint was imposed on CESID, rather than on e.g. SKORR or YNKEE?

Another example, as far as STARs are concerned, is SEA's HAWKZ SEVEN. There is a Minimum Enroute Altitude for each leg, which is more than enough both for obstacle clearance and for communication. Why did the designers decide to an "At or ABOVE FL220" at PTERA? And why at PTERA and not e.g. at KRIEG, KNGDM or WRUSL?

Can someone point me in the right direction?

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Altitude limits on these procedures have to take many different things into account, including obstacle clearance and communication, but also radar coverage, separation from other procedures and airspace, the overall profile of the procedure, noise abatement, and more.

The at or above 2500 restriction on the DEEZZ is similarly included in the other SIDs at KJFK. The main reason could be that the NYPD operates helicopters out of Floyd Bennett Field below that area, and the Jamaica Bay seaplane base is also nearby. Another reason could be to keep aircraft above the approach for runways 4L and 4R, though I'm not sure they would use those at the same time. It could also help noise abatement for the homes and parks in the area.

In the case of the HAWKZ, my guess on the altitude restriction is to keep all the aircraft on those segments at approximately the same altitudes. It seems like an aircraft could be lower than FL220 at PTERA without other issues, but the lower an aircraft descends, the slower it flies, and it would become difficult to work a slower aircraft in with the faster stream of traffic at the higher altitude. This sort of restriction is not uncommon on STARs that begin relatively far out.

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  • $\begingroup$ Keep in mind McChord AFB is just to the South of SEA, and that they have published high altitude instrument approach procedures that might drive keeping commercial traffic higher than terrain would otherwise dictate. $\endgroup$
    – Michael Hall
    Jul 8, 2019 at 18:04
  • $\begingroup$ @MichaelHall KTCM is a good point, but PTERA is closer to PDX than TCM, and I don't see even high altitude procedures for either one in that area. $\endgroup$
    – fooot
    Jul 8, 2019 at 18:29
  • $\begingroup$ Good point as well. Still, it's 83 NM from SEA, and a roughly 265' per NM descent gradient isn't too steep. I think the best we can do is speculate... $\endgroup$
    – Michael Hall
    Jul 8, 2019 at 18:58

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