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I was examining FAA's departure procedures and I noticed PIKES ONE SID (chart and continuation) which serves Denver Airport.

enter image description here

In the description, it states:

TAKEOFF ALL RUNWAYS: Fly assigned heading for RADAR vectors to assigned route. Climb and maintain 10000 or ATC assigned lower altitude. Expect filed altitude 10 minutes after departure.

LOST COMMUNICATION: If no transmissions are received within one minute after departure, maintain assigned heading until 7000 feet, then climb to filed altitude via direct DEN VOR/DME, thence via assigned transition. If filed altitude is above 10000 feet, cross DEN VOR/DME at or above 11000 feet.

What troubles me is that DEN navaid is (obviously) very close to the airport, so I am not sure how an aircraft would depart from the airport via a runway very close to DEN, for example 07/25, and have enough space in order to reach DEN. In addition, based on Lost Communication, an aircraft would climb until 7,000 feet and then go direct to DEN, even if it has already surpassed DEN (by departing, for example, via runway 17R/35L) and theoretically it can just follow the assigned route by skipping this navaid.

In other words, is the aircraft obliged to fly to DEN before following the assigned route under any circumstances and, if yes, what would be a possible flight path in case of a runway that is really close to it?

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    $\begingroup$ It seems like this route is mostly used for flights to KALS. You can see a list here. It looks like the typical route is an assigned heading on takeoff and then direct SOLAR. $\endgroup$
    – fooot
    Commented Oct 24, 2019 at 14:52

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Let's treat the "normal" and "lost communication" cases separately.

Fly assigned heading for RADAR vectors to assigned route. Climb and maintain 10000 or ATC assigned lower altitude. Expect filed altitude 10 minutes after departure.

The essence of this is that on departure, responsibility for navigation rests with the air traffic controllers, not the pilot. The controllers will issue headings and routes to fly in order to keep the aircraft separated from other departures, arrivals, and other traffic. Once clear of traffic, the controller will issue instructions on how and where to rejoin the cleared route. At this point the pilot takes over responsibility for navigation along the cleared route.

Usually, it goes something like this. The departure will be assigned an initial heading, often the runway heading: "runway 17R, fly runway heading, cleared for takeoff." The aircraft flies this assigned heading. The aircraft will then contact the departure controller. The departure controller may continue assigning specific headings in order to separate the aircraft from other departures, arrivals and other traffic. Once clear, the controller has some options. They can clear the aircraft direct to a convenient fix/waypoint or NAVAID on the aircraft's flight plan ("Proceed direct ADANE, resume own navigation") or they can say something like "Fly heading 130, join the Denver 159 radial, resume the departure." It's up to them, but they will issue some kind of instruction that results in the aircraft joining its cleared route.

LOST COMMUNICATION: If no transmissions are received within one minute after departure, maintain assigned heading until 7000 feet, then climb to filed altitude via direct DEN VOR/DME, thence via assigned transition. If filed altitude is above 10000 feet, cross DEN VOR/DME at or above 11000 feet.

If communication is lost, the pilot should do the following in order once it is realized that communication has been lost.

  1. Fly the last assigned heading until reaching 7,000'.
  2. Turn (back toward the airport and the DEN VOR) and fly to DEN.
  3. Comply with the crossing restriction (make sure you reach 11,000' before getting to DEN if your filed altitude is above 10,000').
  4. At DEN, turn outbound on the appropriate (filed/cleared) transition leg.
  5. Keep climbing to the filed altitude.

It is likely that some short amount of time will pass before it is realized that communication has been lost. The aircraft will travel some distance away from the airport during this time. The aircraft must also continue until it reaches 7,000'. So by the time it would become necessary to "proceed direct DEN," the aircraft will not be "right next to it" and a turn direct DEN is reasonable.

If you departed runway 25, your route might look something like this (not to scale!).

enter image description here

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    $\begingroup$ Shouldn't the flightpath in that diagram be passing directly over DEN and then turning to the transition leg, rather than turning back well short of DEN? $\endgroup$
    – Vikki
    Commented Oct 24, 2019 at 22:27
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    $\begingroup$ @Sean That's a good question and might be worth a dedicated post here. What I've drawn shows "turn anticipation" and is what any RNAV system I've ever used will do (Garmin, Rockwell Collins FMS, etc.). Airway protected volumes include flyover overshoot protection for non-anticipated (flyover) turns. Aircraft without RNAV or DME may not be able to turn early and must fly-over. Either way, as long as you stay within the protected volume, it doesn't matter. Note that some waypoints in actual RNAV procedures are explicitly fly-over instead of fly-by. $\endgroup$
    – TypeIA
    Commented Oct 25, 2019 at 0:44
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    $\begingroup$ That said the turn should definitely at least be drawn closer to DEN. It looks premature and cuts off too much of the corner. I drew the spline in by hand as a Path in Photoshop so it's not at all precise. :) $\endgroup$
    – TypeIA
    Commented Oct 25, 2019 at 1:00
  • $\begingroup$ In the old days of /A navigation, an aircraft was expected to fly to the NAVAID before making the turn. Modern FMS, however will cut the turn short of the NAVAID, and fly the aircraft's best performance radius to the new course. $\endgroup$
    – atc_ceedee
    Commented May 9, 2021 at 21:20

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