ODPs and Circling Approaches

Flight Summary

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.

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.

Here are three potential routes for this flight:

• BRYCE# BCE V8 JNC V134 DBL
• BRYCE# BCE J60 DBL
• BRYCE# BCE DBL

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.

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.

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.

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.

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!

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.