ODPs and Circling Approaches

FSA Learning Flight 4

Fun Fact

Built in 1936, the hangar at KBCE is fashioned entirely from local ponderosa pine, adapting old-fashioned construction techniques to accommodate new transportation technology. This distinctive building helped put the airport onto the National Register of Historic Places in 1978.

Source: www.brycecanyonairport.com
Screenshot by Orbx

Flight Summary

Flight 4 takes us to one of the world’s most challenging high-elevation airports: Aspen (KASE). The surrounding terrain only offers one way into and out for most aircraft. And if that and the 8,000 ft. elevation wasn’t enough, you have the unpredictability of Colorado mountain weather to contend with. But before we get to fly the challenging approach into KASE, we have to escape KBCE, which has plenty of its own challenges.

Concepts Discussed in this Flight:
  • Obstacle Departure Procedures
  • Flight Levels
  • Circling Approaches

Airports Visited in this Flight

Bryce Canyon Airport

Bryce Canyon Airport (KBCE)

Elev: 7,590 ft. / 2,314 m

Addon Scenery Recommendations

Aspen Airport

Aspen-Pitkin County Airport (KASE)

Elev: 7,738 ft. / 2,289 m

Addon Scenery Recommendations

Objective 1

Prepare to Fly

Once again, picking the right aircraft will make a big difference on this flight. In addition to needing RNAV capability, you’ll want an aircraft that can depart from a relatively short runway and climb quickly. Since we’ll be going into the flight levels on this flight, a turbine or jet-powered aircraft will be best. However, the runway at KASE is restricted to aircraft with:

  • A maximum wingspan of 95 ft. or less.
  • A maximum allowable gross landing weight in excess of 100,000 lbs. (dual wheel) or 160,000 lbs. (dual tandem wheel).

The airport is one of the most scenic we’ll fly to anywhere in the series. Gateway to world-class skiing and resort lifestyle, Aspen sees regular CRJ series aircraft from SkyWest (operating for American, United, and Delta). The airport also sees plenty of private jet traffic and hosts two flight schools.

Objective 2

Locate the Obstacle Departure Procedure

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.

Objective 3

Fly the ODP

Let’s look at the BRYCE# departure in detail:

The procedure explains what to do when departing from either end of the runway. If departing from Runway 3, aircraft fly to the YAYDO waypoint before turning back to BCE. Once BCE is reached, the aircraft (climbing at or better than the minimum 285 ft. per NM to 12,100 ft.) is safe to turn in any direction and join the filed route.

For departures from Runway 21, pilots turn right toward BCE. In this case, the aircraft won’t necessarily be high enough to be afforded obstacle clearance. Thus, the aircraft needs to hold at the BCE VOR until reaching a safe MEA (for example, along a Victor airway) before proceeding on course.

By the way, now that we have mentioned climb gradients in several places, you may be wondering how to translate information like "climb at 285 ft. per NM to 12,100 ft." into something helpful. The easiest way is to look at the FAA’s Climb/Descent Table, which is published at the end of each TPP.

To find the official version of this table, visit the FAA's Terminal Procedures Publication page, pick any of the volumes (like NE1), and open it. The table is the second-to-last page.

Armed with this knowledge, let’s review how the ODP would be flown assuming Runway 3 is planned for departure. Remember, even if you’re flying with human ATC, it’s up to you to select your desired departure runway at this untowered airport.

Air Traffic Control (Click to Expand) (Click to Collapse)

Following the ODP from Runway 3 is simple: fly heading 033 to 8,100 ft., then fly to YAYDO, and then to BCE VORTAC. You must reach BCE by 13,300 ft. before you can turn in any direction and proceed on course. The departure from Runway 21 is a little more complicated, involving flying a hold entry at BCE, and continuing to climb in the hold until reaching a safe altitude.

Ground School Seminar: Holding Patterns
We don’t cover hold entries in detail in this flight. For a detailed discussion of holds, including rules, entries, and regulations, Boston Virtual ARTCC has produced a dedicated Holding Patterns Ground School seminar for online viewers. This hour-long session features interactive walk-through examples that can be applied to this scenario. The most logical entry into the BCE VORTAC hold for departures from Runway 21 is a parallel entry.

Objective 4

Navigate to KASE

From the BCE VORTAC, you have several choices for navigating to KASE. Using the Enroute L-9 IFR chart, you can see one option is to join the V8 airway at BCE (MEA 13,300 ft.) and follow it to JNC before joining V134 to the DBL VOR near KASE. However, this limits you to a maximum cruising altitude of 17,000 ft (recall that Victor airways are low-level airways). A second option, if you’re planning to enter Class A airspace and cruise at FL190 or above, is to join J60 at BCE, an airway that connects directly to the DBL VOR. Finally, you could elect to simply use the OROCA published along the route and navigate directly to KASE (or the DBL VOR) after you complete the ODP at BCE. For this flight, enroute navigation is your choice. But, for reasons we’ll explain in the next objective, we’d recommend picking a route that ends up at the DBL VOR.

Pilot Tip

In the United States, 18,000 ft. is the "transition altitude". Above this altitude, pilots use a standard altimeter setting of 29.92" (instead of the local airport altimeter settings used at lower altitudes). To reflect this change to "standard" pressure settings, U.S. pilots reference altitudes above 17,999 ft. as "flight levels". The term "FL190" means 19,000 ft. as read on an altimeter set to 29.92".

Different countries have their own rules regarding transition altitudes and flight levels. In some countries, the transition altitude can be as low as FL060, or 6,000 ft.

Here are three potential routes for this flight:


Objective 5

Select an Approach

Once you reach your cruising altitude, and perhaps even before, you’ll need to start looking at the available approaches at KASE. By now, you should know where to find instrument approach procedures and will notice the following approaches are published for KASE:

  • RNAV-F.
  • LOC/DME-E.
  • Roaring Fork Visual Runway 15.

Excluding the visual approach, you can see we have choices between the RNAV and LOC/DME approaches. However, you might notice these approaches are named a little differently. Instead of seeing "RNAV RWY 21" (like at KBCE), this approach just says "RNAV-F".

Most instrument approaches, including all of those we’ve flown thus far, are aligned with specific runways so that straight-in minimums can be published. The requirements for such an approach are that the final approach course must be aligned within 30 degrees of the straight-in runway and the approach must also allow for a reasonably gradual descent path. However, the terrain at KASE doesn’t allow for anything to happen gradually. Both the RNAV-F and LOC/DME-E approaches are not able to offer a shallow enough descent angle to be considered straight-in approaches. As a result, instead of the RNAV RWY 15 approach, we have the RNAV-F.

Approaches that end in a letter, like the RNAV-F or LOC/DME-E are called circling approaches. The initial portion of flying the approach is just like that of any other approach type. You join the lateral navigation portion, capture the vertical profile (either with navigation equipment or by manually descending the aircraft to meet the charted altitude restrictions), and fly to the minimums. However, once you get to the minimums, the rest is up to you: you need to decide how to safely maneuver the aircraft to stick the landing. We’ll look at that in the next objective.

Whether you’re flying with ATC or on your own, you can request or fly either the RNAV-F or LOC/DME-E approach. The minimums are very similar, so the choice might come down to your navigation capabilities or comfort with one approach over the other. You might also select an approach based on how you’ve decided to fly the enroute portion to KASE. For example, if you’re passing over DBL, flying the RNAV-F via the VORTAC might be easiest. Or, if ATC is available to give you vectors (or just direct AJAXX), flying the LOC/DME-E could avoid a course reversal.

This flight will discuss flying the RNAV-F approach from the DBL VOR, assuming you’re reaching the VOR via the V134 airway (MEA of 14,000 ft.) or direct (crossing at the OROCA of 16,800 ft.). Because there is a published hold-in-lieu of procedure turn at the DBL VOR, we can use it to help set up for the approach.

Objective 6

Flying the RNAV-F Approach

First, we’ll discuss setting up the RNAV-F Approach and flying it to the Final Approach Fix (FAF) of ALLIX, which aircraft cross at 12,200 ft. MSL (or about 4,300 ft. AGL). Depending how you approach the DBL VOR, this is likely going to involve flying a hold entry. In the next objective, we’ll discuss the circling maneuver: how you get from ALLIX to the runway.

Look at the RNAV-F Approach at KASE. The approach begins at the DBL VOR, which also has a published hold. In fact, this is called a hold-in-lieu of procedure turn, and it’s used by pilots who are coming the "wrong way" to "turn around" and establish inbound on the approach. For example, Aircraft #1 in the figure below is inbound to DBL from the south. There is no way this aircraft could cross DBL and immediately pivot to the to join the final approach course; it would require an excessively steep turn. Instead, the aircraft uses the depicted hold to safely point toward the runway.

However, Aircraft #2 is located north of the DBL VOR and is nearly aligned with the runway already. In this scenario, there is no need to fly a course reversal; the aircraft can simply cross the DBL VOR and then continue flying the approach. Skipping the hold-in-lieu in this way is authorized by the boxed note: "NoPT for arrivals on DBL VOR airway radials 297 CW 020". In other words, aircraft coming to DBL from anywhere other than the blue-shaded area (north of the VOR) must fly the hold-in-lieu of procedure turn to become established on the approach.

In this example, we’re tracking to DBL via V134, which is outside of the "NoPT" area. As a result, we’ll be required to (and will want to) fly the hold-in-lieu of procedure turn. Effectively, we’re flying the first part of a hold (the entry) to join the final approach course, then flying inbound to the airport. To do so:

  1. Fly to DBL via the V134 airway. Along the airway, you can descend to the MEA of 14,000 ft. MSL.

  2. At the DBL VOR, turn left heading 346. Fly this heading for about one minute, managing your speed so that flying for one minute does not put you further than 8 NM from the VOR. You can also descend to 13,700 ft. MSL at this time.

  3. After 1 minute, make a left 225-degree turn to a heading of 121.

  4. Fly heading 121 to join the 166 inbound radial to DBL (final approach course), crossing DBL level at 13,700 ft. MSL.

These steps are illustrated in the figure below:

You’ll now be just north of DBL, pointing toward the runway:

At this point, you’ve just flown a parallel hold entry. Since you’re lined up with the runway and are at the recommended 13,700 ft. MSL altitude at DBL, there is no need to fly another lap in the holding pattern. Instead, you’ll fly the RNAV approach inbound, just like on the RNAV RWY 21 approach at KBCE.

Pilot Tip
If you’re using an advanced GPS or FMS, the hold entry might be pre-programmed; flying the approach from DBL might be as simple as selecting the DBL transition and then following the magenta line. Remember, however, even if you’re following an FMS or GPS course, you’re still in charge. If the airplane starts to turn the wrong direction toward terrain, it’s up to you to stop it.

Objective 7

Circle to Land

As we’ve discussed, the RNAV-F is a "circling approach". This differs from the "straight in" approaches (like the RNAV RWY 21 at KBCE) we have seen in past flights. On both the approaches to KASE, the terrain just north of the runway prevents a standard approach from being constructed. A typical ILS approach uses a 3° descent angle; this approach uses a 6.49° angle!

In this objective, looking at the RNAV-F, we’ll discuss how to make it from the published minimums (about 2,2400 ft. MSL) to the runway. The circle-to-land concepts described below will be equally applicable to aircraft flying the LOC/DME-E approach.

A normal circling approach begins like any other: descend along the procedure until you reach the circling MDA (in this case, 10,220 ft. MSL for the recommended aircraft), then level off. While keeping the airport in sight, proceed as directly as possible to the intended landing runway. Given that you may be below the standard VFR traffic pattern altitude, a base or downwind leg will likely be closer to the airport than usual. Provided you remain within the protected area for the approach, the circling MDA will provide 300 ft. of clearance from terrain and obstacles.

Remain level at the circling MDA until in a position from which a descent to a landing on the intended runway can be made at a normal rate of descent, using normal maneuvers. Then, make one smooth, turning descent toward the runway to land. For example, at an airport with a little less nearby terrain, if you were planning to circle from this approach to land on Runway 33, the approach might look something like this:

However, here at KASE, landing on Runway 33 is not a great idea. It’s downhill and the terrain on the approach end makes a landing on Runway 33 very challenging (whereas the terrain northwest of the airport is a little more forgiving). You would have to keep the turn to final pretty close to the runway to avoid the 8,156 ft. MSL peak just south of the airport.

Pilot Tip
The key to flying this approach successfully is configuring the aircraft early. It may be advisable to have flaps and gear in the landing configuration before leaving 13,700 ft. MSL at DBL. Careful management of altitude, speed, power, and descent rate is required to fly the approach "straight in".

With better terrain and an upsloping runway, landing on Runway 15 is much more favorable. If you get the runway in sight soon enough, the most common practice is to "circle" by flying the approach straight in. As soon as you break out of the clouds, anywhere above the published minimums, as long as you are able to maintain visual contact with the runway, it’s safe to descend. You’ll need a pretty significant rate of descent to make the approach, so managing your speed, configuration, and power settings will be important. For most airline operations, the maximum descent rate below about 1,000 ft. AGL is 1,000 FPM. If, at 1,000 ft. AGL, your vertical descent is significantly higher than 1,000 FPM, a missed approach should be initiated. Similarly, by 1,000 ft. AGL, you should be established in the correct configuration for landing with all checklists completed and the airspeed at the appropriate approach speed for your aircraft.

If you find you’re too high for the landing, or if you only break out of the cloud close to the airport, two potential circling maneuvers you could fly to land on Runway 15 are shown below:

Ultimately, there is no single "correct" answer when it comes to circling. Unless the procedure prohibits it (and with ATC approval), you can circle in any direction or method to make the approach. However, you do have to remain close enough to the airport to stay within the protected area. Generally, getting further than 2-3 miles from the runway is "too far".

Circling may require maneuvers at low altitude, at low airspeed, and in marginal weather conditions. Pilots must use sound judgment, have an in-depth knowledge of their capabilities, and fully understand the aircraft performance to determine the exact circling maneuver since weather, unique airport design, and the aircraft position, altitude, and airspeed must all be considered.

Air Traffic Control (Click to Expand) (Click to Collapse)

Objective 8

Land and Taxi to Parking

The approaches to KASE are some of the most challenging flown in the world. Between the terrain, elevation, full approach including course reversal, and circle-to-land procedure, you’re well down the path of professional pilot—or, at least, flight simulation expert—when you can successfully complete this flight!

Go Flying

To complete Learning Flight 4, escape KBCE using the ODP, then navigate to KASE. Fly the mentally and physically challenging circling LOC/DME or RNAV approach at KASE and you’re one flight away from completing our Learning Flight series!

  1. Load your aircraft at KBCE and set the weather.
  2. Plan your route: determine how you’ll get from BCE (at the end of the BRYCE# ODP) to the DBL VOR, where the KASE approach begins.
  3. Fly an instrument approach to KASE. Remember, neither of the two instrument approaches are available at night (denoted by the "procedure NA at night" note on each chart).
  4. Fly the approach and land at KASE. As you park, be happy you don’t have to pay the $100+ landing and handling fees charged to real-world general aviation pilots landing here!

In Flight 5, we’ll look at escaping KASE using an almost-forgotten navaid: the back course. From there, we fly into Denver International Airport (KDEN) using a modern, RNAV STAR to introduce the "descend via" concept and finish off the Learning series with an RNAV RNP approach.