When flying into KBCE in Flight Learning 3, we saw there was no control tower at the airport. As a reminder from Learning Flight 1, we can confirm this by looking at the sectional chart. Check out the Las Vegas Sectional on SkyVector and use the "World VFR" tab to locate "KBCE":
The Class E airspace surrounding the airport, along with the magenta runway, tells you the airport does not have a Tower. The letter "C" beside the 122.80, which denotes the CTAF frequency, is another giveaway. If you now find KASE, our destination airport, you’ll notice its blue runway indicates a tower controls the airport, and the blue, dashed circle indicates it is in Class D airspace.
Since we’re planning to depart IFR, the absence of an air traffic control tower means that we are subject to the "one in one out" rule in terms of ATC separation. It also means we won’t be contacting a local controller to receive our IFR clearance but instead someone remote at Salt Lake City Center. At most untowered airports, IFR clearances obtained on the ground won’t include clearance for a SID or a specific heading. Instead, pilots are generally expected to navigate on course at their own discretion after departure. Furthermore, terrain and obstacle separation is the pilot’s responsibility until the aircraft reaches a published safe altitude or receives radar vectors, when ATC begins ensuring terrain and obstacle clearance requirements.
With these details in mind, imagine the following scenario: KBCE is surrounded with heavy fog, so you have no visual references to the nearby mountain peaks. In your IFR clearance, ATC simply says "cleared as filed", without giving a heading or assigning a SID (since there are no SIDs at KBCE). You are responsible for navigating to the first waypoint on your route at your own discretion. How are you supposed to depart safely into the fog without the guidance of a regular SID? The answer is to use an Obstacle Departure Procedure (ODP).
Unlike the SIDs flown up to this point, which were at towered airports and documented with detailed charts, most ODPs consist only of a textual set of instructions that guarantee separation from terrain and obstacles, if followed correctly. Air traffic control may assign an ODP in an IFR clearance, but usually you will not be specially instructed to fly it. Regardless of whether or not it is assigned, flying the ODP is always acceptable and is especially encouraged when the weather is bad.
ODPs are even published for large, international airports, though they aren’t used as much because SIDs already incorporate obstacle protection.
Before we explore the (slightly more complex) situation at KBCE, let’s look at a textual ODP. There are several published for the airport we departed from in our last flight: KSLC. Returning to the AirNav page for KSLC, you’ll see a link toward the bottom of the charts section:
Clicking the link brings us to a long PDF with ODPs for several area airports.
As an alternative to AirNav, you can find ODPs in the Terminal Procedures Publication (TPP), along with other terminal charts. However you get to them, when you’re looking at the ODPs for the region, find "SLC" and you’ll see the specific procedures published for Salt Lake City International:
From Runway 14, you can see the ODP says to "climb to 10,000 ft. on heading 192 and the FFU R-341 to the FFU VORTAC before proceeding on course". In other words, climb on runway heading, and then join the FFU VORTAC radial 341 and track it southerly until you reach 10,000 ft. At 10,000 ft., the ODP tells you that you can safely turn in any direction and, provided you continue climbing at a standard rate of 200 ft. per NM to a safe altitude like an MEA, you will be protected from terrain. (There’s a little more to this but that’s the basic idea.)
The FAA provides obstacle assessments for departure for any airport with a published instrument approach. When there is no published ODP for an airport with a published instrument approach, the result of the FAA’s terrain assessment is that it’s safe to turn on course in any direction once you're 400 ft. above the runway.
Of course, at an airport like KSLC, you’d never be worried or even thinking about ODPs because ATC will have cleared you for a SID, which incorporates the obstacle protection of an ODP. However, at KBCE, there are no SIDs. If you go to the AirNav page for KBCE, click the link to access the ODPs, and then find "BCE", where you’ll see the following:
Unlike the textual ODPs at KSLC, the terrain surrounding KBCE is complex enough that the FAA has elected to make this ODP graphical. As a result, you can find the ODP published as the "BRYCE# DEPARTURE (OBSTACLE)". Although it looks a lot like a SID, it’s still an ODP. That means you don’t need ATC to specifically clear you "via the BRYCE# departure" to fly it.