AINsight: Circling Can Be a Very Risky Approach

 - November 26, 2021, 10:00 AM

Pilots continue to demonstrate widespread confusion on the key elements of flying a circling approach, according to a recent Flight Safety Foundation (FSF) survey that found they often misunderstand basic terms and procedures for this procedure. A lack of understanding of these crucial factors when maneuvering an aircraft close to the ground in marginal weather conditions can lead to tragedy.

Basic terms such as circling approach, visual approach, circle to land, and visual maneuvering often are misunderstood by pilots. Likewise, there is a general lack of understanding regarding flying a circling approach procedure. As an example, pilots are confused on when to begin the circling maneuver, what direction to turn, when to descend from the minimum descent altitude/height to the touchdown zone, and how to properly fly a go-around from a circling approach.

Another FSF study highlights the dangers of flying a circling approach. These procedures are inherently riskier than a straight-in approach and should be flown only as a last resort. Risks include penetrating obstacle clearance limits either during the approach or subsequent go-around, a loss of control in-flight event either during the approach or go-around, or colliding with another aircraft in the air or during a wrong surface landing.

Straight-in approaches are 25 times safer than a circling approach; adding vertical guidance (an ILS glideslope or VNAV path) increases the safety margin by another eight times. For these reasons, operators will either prohibit or place restrictions on circling approaches.

The FAA’s Instrument Procedures Handbook urges caution when attempting a circle-to-land maneuver: “Circling approaches are one of the most challenging flight maneuvers in the National Airspace System (NAS), especially for pilots of Category C and Category D turbine-powered transport category airplanes. The maneuvers are conducted at low altitude, day and night, and often with precipitation present affecting visibility, depth perception, and the ability to adequately assess the descent profile to the landing runway.”

Furthermore, AIM 5-4-2(f) states, “Circling may require maneuvers at low altitude, a 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.”

In business aviation, access to second or third-tier airports creates a Catch 22 situation. The ability to serve “close-in” or remote airports is a huge benefit to passengers, but often these airports do not have the approach capability of larger airports. Operators and pilots must weigh the risks associated with flying something other than a straight-in approach and determine if it is worth the risk of flying a circling approach.

In a recent accident, preliminary reports suggest that the pilots of a midsize business jet—a Category C aircraft—lost control in-flight during a circling maneuver. On July 26, 2021, a Bombardier Challenger 605 aircraft crashed near the Truckee-Tahoe Airport (KTRK) in Truckee, California. Both pilots and four passengers were killed in the crash.

The NTSB preliminary report sets up the event as a routine flight from Coeur d’ Alene, Idaho, to Truckee. As the aircraft passed over northwest Nevada, the flight became more complicated when ATC began to issue descent instructions and advised the flight crew to expect the RNAV (GPS) approach to Runway 20 at KTRK due to ATC flow control “constraints.” The flight crew accepted the approach and requested to circle to Runway 11 (a longer runway) for landing performance considerations.

At that time, the weather at KTRK was reported as variable winds at three knots, a 3,500-foot ceiling, and five miles of visibility, with smoke from nearby forest fires. Runway 11 circling approach minimums for a Category C aircraft at KTRK include an MDH of 1,796 feet and visibility of three statute miles. Visibility at the time of the accident reportedly had dropped to four statute miles.

Approaching KTRK, the flight crew was instructed by ATC to hold at ALVVA—the initial approach fix—due to preceding traffic on the approach. After one turn in the holding pattern, ATC cleared the flight crew for the approach, canceled radar services, and instructed them to contact the KTRK tower.

At the LUMMO fix, approximately 10 nm north of Runway 20, the flight crew “checked in” with the tower. The tower controller offered either a left downwind to Runway 29 or Runway 11; the flight crew announced that they would make a right turn and reported Runway 11 in sight. ATC then cleared the flight to land on that runway. There were no further radio transmissions from the aircraft.

Witnesses near the crash site reported seeing the aircraft at a low altitude and in an abnormal flight path to Runway 11. Others noted the aircraft in a nose-down attitude in a steep left turn—“banking erratically”—just before impact.

A preliminary flight path reconstruction indicates the aircraft overshot the final approach course to Runway 11 and crashed short of the runway.

The crew did have other options. In addition to the RNAV (GPS) approach to Runway 20, KTRK has a straight-in RNAV (GPS) approach to Runway 11; that approach would have offered a much higher safety margin than attempting the circling approach maneuver.

Circling approaches are not an instrument approach in the traditional sense. A circling approach is the visual segment conducted after an instrument approach and terminates in either a landing or an instrument missed approach.

According to ICAO Doc 8168 PANS-OPS Vol 1–Flight Procedures, “A circling approach is an extension of an instrument approach procedure which provides for visual circling of the airport prior to landing.” JAR-OPS 1.435(a)(1) defines it as “a circling approach in the visual phase of an instrument approach to bring an aircraft into position for landing on a runway which is not suitably located for a straight-in approach.”

In other words, pilots fly a circling approach when they cannot land from a straight-in approach due to tailwinds, obstacles, other limitations, or to accommodate traffic flow for ATC. Circling approaches come in many different varieties, but what is confusing is that they are all classified as a “circling approach.”

Examples include a circling approach that becomes a VFR pattern due to winds or to accommodate ATC restrictions—in other words, to accommodate an orderly traffic flow in high-density airspace.

Common “circling VFR patterns” are Teterboro’s (KTEB) ILS Runway 06 circle to land Runway 01—this procedure separates KTEB traffic from Newark International and the major airports in New York City, namely LaGuardia and JFK. Another is Chicago Midway’s (KMDW) ILS Runway 31C circle to land Runway 22L, which provides space between traffic at Midway and Chicago O’Hare.

Other varieties include a circling approach that is really a straight-in to a specific runway. Classic examples include the old “checkerboard” approach to Hong Kong Kai Tak Airport’s Runway 13 and the iconic Canarsie “circling approach” to Runway 13 L/R at New York’s JFK International Airport. Both approaches were replaced by either an entirely “new” airport or RNAV GPS approach.

From the prior FSF survey, pilots often would misinterpret terms such as a circling approach, visual approach, circling to land, and visual maneuvering. Although a visual approach and circling approach are conducted by visual reference, there are some differences.

A visual approach, in general, is an approach by an IFR flight when either part or all the instrument approach is not completed, and the approach is executed in visual reference to the terrain—or, in the U.S., by following the preceding aircraft. Visual conditions are defined as maintaining VMC. In the event of a go-around or balked landing, the pilots will comply with ATC instructions.

In contrast, a circling approach, after initial visual contact, the basic assumption is that the runway environment must be kept in sight while at the MDA(H) during circling. If visual reference of the runway is lost while circling, the missed approach for the instrument approach must be followed.

Another common misconception is when to descend from the MDA(H), when to begin the circling maneuver, or what to do in the event of a missed approach. In general, a successful circling approach begins with a thorough briefing at cruise, if not before.

Understanding the approach category of the aircraft, the circling criteria (either TERPS or ICAO PAN-OPS or other), current weather conditions (to include ceiling, visibility, and winds), restrictions to circling (for example, at night or in a certain geographic area), and the missed approach procedure are paramount to a safe outcome.

In general, TERPS applies to airports in the U.S., territories in the Pacific region, or U.S. military bases. Otherwise, ICAO PAN-OPS applies. On Jeppesen charts, these criteria are displayed on the far-left margin or in the “minimums” boxes.

Of importance, the category of the aircraft is based on indicated airspeed (IAS) flown during the circling maneuver. Generally, this is 1.3 times stall speed (Vso) at max landing weight or the approach speed recommended by the OEM—often the higher of the two.

The most recent TERPS and ICAO PAN-OPS circling criteria “updates” account for elevation (for example, true airspeed) and wind up to a maximum of 25 knots. Approaches with the new larger circling minima are displayed on Jeppesen approach charts with a “C” in a black square.

Pilots must understand and plan to maneuver within the visual circling area to maintain the minimum obstacle clearance as prescribed for that category of aircraft. A common strategy to reduce the risk of maneuvering during a circling approach is to use the next higher category to increase the safety margins—meaning an approach Category C aircraft uses Category D minima. Likewise, pilots can use the aircraft’s flight management system to “draw” an appropriately sized circle around the runway to visualize the maneuvering area.

A final area of confusion for pilots is related to initiating a go-around from a circling approach. The correct response can be broken down into two steps. Prior to reaching the MDA, fly the published missed approach procedure; or after reaching the MDA, and beginning the circling maneuver, the missed approach begins with a climbing turn towards the airport and then rejoins the missed approach of the approach conducted prior to reaching the MDA. Of importance, first begin the climb, but always honor the lateral path of the missed approach procedure as published.

Circling approaches are an incredibly complex procedure. One of the best risk-mitigation strategies is to simply eliminate the hazard by flying a straight-in approach or, if available, an RNAV visual approach (for example, KEWR’s Stadium Visual).

Since a circling approach at or near minimums is dangerous, another strategy is to divert to an airport with better approach capabilities.

Planning for a circling approach requires an extensive briefing to include aircraft configuration at specific points, level of automation to be used, a clear understanding of when the circling maneuver begins, and at what point it is safe to descend from the MDA(H). It also requires an exacting explanation of how to initiate the go-around from various points on the approach or during the circling segment of the approach.

Pilot, safety expert, consultant, and aviation journalist - Kipp Lau writes about flight safety and airmanship for AIN. He can be reached at stuart.lau3@gmail.com.