WASHINGTON — The National Transportation Safety Board (NTSB) has issued a safety alert highlighting the risks and necessary preparations for circling instrument approach procedures. 

The alert, titled "Circling Approaches: Know the Risks," comes as the NTSB prepares a report on its investigation into the July 2021 Bombardier Challenger 605 accident in Truckee, California, which involved an unstabilized circle-to-land approach. The Safety Board released the alert to coincide with the Air Charter Safety Foundation's (ACSF) Safety Symposium held last week.

At the ACSF event, board member Michael Graham provided an overview of the publicly available facts in the Truckee accident. Graham cited the accident and others, including the May 2017 Learjet 35A crash in Teterboro, New Jersey, and the December 2021 Learjet 35A accident at Gillespie Field in El Cajon, California, as instrumental in developing the safety alert.

According to the NTSB's alert, 10 accidents involving Part 91 and 135 operators have occurred during circling approaches since 2008, resulting in 17 fatalities. These approaches can be more dangerous due to the need for maneuvering at low altitudes and low airspeeds, increasing the chances of losing control or colliding with terrain.

Moreover, the NTSB explains that circle-to-land maneuvers often lead to unstabilized approaches. While sometimes necessary, pilots may not always assess the risks before agreeing to them.

To mitigate these risks, the safety alert advises operators to fully comprehend the risks involved, consider their own experience and limitations, such as weather and runway configuration, and be aware that they may have the option to request alternatives. Additionally, the NTSB recommends scenario-based training in realistic environments for such approaches, emphasizing the importance of a comprehensive briefing before undertaking them.

Graham outlined various issues uncovered during the investigation of the Truckee accident. These included inconsistencies in passenger numbers, the captain's incorrect visa status, a lack of basic indoctrination training and operating manuals for the captain and copilot, and the absence of a weight-and-balance calculation. The operator had only held its Part 135 certificate for 13 days, and this was the first time the crew had flown together.

The crew initially accepted an RNAV Runway 20 approach from ATC, despite having briefed for an RNAV approach to Runway 11. They never briefed for the new approach and ultimately requested a circle to Runway 11 as Runway 20 was too short. The aircraft eventually crashed while maneuvering too close to the ground with an incorrect configuration and speed, resulting in six fatalities.

The NTSB notes that several options could have led to a stabilized approach, such as requesting their original planned approach, briefing for the initially accepted approach, or performing a missed approach.

Graham referenced a Flight Safety Foundation finding that runway-aligned approaches are 25 times safer than non-aligned approaches. He emphasized the importance of understanding the risks, personal experience levels, and limitations before attempting a circle-to-land approach, advising pilots not to accept approaches they are not comfortable with.