AINsight: FMS Error Results in Near-CFIT Accident

In October 2023, the captain of a de Havilland DHC-8-106 approaching the Val-d’Or Airport (CYVO) in Quebec, Canada, requested a go-around from air traffic control due to “navigation problems.” Seconds later, the terrain awareness warning system (TAWS) began generating alerts, and the flight management system (FMS) automatically displayed information about an imminent collision with terrain. The captain then ordered a go-around.

The Transportation Safety Board (TSB) of Canada’s safety investigation report cited a single programming error in the FMS that ultimately led to a series of additional errors that contributed to the flight crew’s confusion, increased workload, and loss of situational awareness during the approach.

At the time of the TAWS alerts and subsequent go-around, the aircraft was 1 nm right off the charted course, descending at 1,300 fpm, passing through 405 feet agl at 192 knots (approach speed was 120 knots) in a clean configuration.

Weather just before commencing the approach at CYVO was reported as IMC with light winds, ceiling 300-foot overcast, and visibility 5 statute miles. There were two pilots, one flight attendant, and 28 passengers on board.

TSB Investigation

Following the event, TSB began investigating the occurrence and published its final report (A23Q0143) on Oct. 28, 2025. At the time of the event, the regional airline that operated the aircraft had bases in Quebec and Ontario. It operated 17 aircraft, including one Hawker Siddeley 748, 14 DHC-8-100s, and two DHC-8-300s.

All Dash 8s were equipped with two Universal Avionics FMSs that operated in a “synchronized” mode, allowing each pilot to check and amend the flight plan as needed.

Most of the Dash 8s, including the incident aircraft, were equipped with an analog attitude indicator (ADI) and a traditional heading situational indicator (HSI). Only six of the company’s Dash 8s were configured with electronic flight instrument systems.

The captain of the incident flight had flown the Dash 8 for 17 years and had 10,600 hours TT, with more than 9,000 hours in type. The first officer was hired approximately six months before the event and had about 1,500 hours TT and 245 hours in type. During the flight, the captain was the pilot monitoring (PM), and the first officer was the pilot flying (PF).

Through interviews and flight data analysis, the TSB began to focus on the flight crew’s interactions with the FMS before initiating the RNAV (GPS) Approach to Runway 18 at CYVO. Unfortunately, the cockpit voice recorder for the event flight had been overwritten by subsequent flights.

As the aircraft approached CYVO, Montreal Area Control Center (ACC) advised the Dash 8 pilots that a medevac flight was going to land before them and issued a clearance to proceed direct to the IKDOB intersection—an initial approach fix—and to “conduct the published hold.” This is where the problems began.

Before selecting “direct to” (DTO) IKDOB, that intersection was listed three different times on the FMS waypoint and flight plan list. At the time of the DTO selection, IKDOB was the fifth waypoint listed. Two other IKDOB waypoints were listed: one at the beginning of the approach (#7 on the waypoint list) and one at the end of the missed approach–the “hold waypoint” (#12).

The PM entered “direct to” IKDOB in the FMS, and the aircraft proceeded as planned. Next, the PM attempted to add a holding pattern at the IKDOB waypoint. By default, the FMS “suggested” the preprogrammed hold at the end of the missed approach; the third IKDOB or waypoint #12. The PM accepted this suggestion and then activated the “DTO HOLD” (direct to hold) function in the FMS.

According to the report, “Unbeknownst to the flight crew, the FMS navigated the aircraft to the IKDOB missed approach waypoint, which corresponded to the final waypoint on the flight plan.” Once entering the hold at IKDOB, the next waypoint on the FMS navigation page would be replaced by dashes. The entire approach and missed approach procedure were now removed from the FMS flight plan.

Making matters worse, the final approach course for the RNAV (GPS) RW 18 approach was 182 degrees, while the holding pattern at IKDOB was offset to the northeast of the intersection with an inbound course of 230 degrees—a difference of 48 degrees.

Once established in the hold, the medevac aircraft executed a go-around due to poor weather and was not ready to begin another approach. At that point, ACC cleared the Dash 8 pilots to conduct an RNAV (GPS) approach to Runway 18 and asked if they could proceed directly or if they needed another circuit in the holding pattern. The flight crew acknowledged that they could proceed direct and begin the approach.

Following the approach clearance from ATC, the PM set the “PROCEED” (proceed to) function in the FMS to exit the holding pattern the next time it crossed IKDOB. “NO LINK” was now displayed on the FMS navigation page, indicating that there was no waypoint after the holding pattern at IKDOB.

Passing IKDOB–now the last waypoint in the FMS–the FMS maintained the aircraft on its current course (230 degrees), which diverged from the final approach course by 48 degrees. The aircraft continued this divergent course for 44 seconds.

Next, the PM attempted to reprogram and activate the RNAV (GPS) Runway 18 approach in the FMS. This action caused the FMS to enter the command heading mode, which synced with the current heading of 230 degrees. At that point, the aircraft continued a divergent course and was high above the desired vertical path.

The PF then began a 1,300-fpm descent using the vertical speed mode of the autopilot. Power was not reduced, so the airspeed began to increase to 204 knots.

Now, right of course, heading (HDG) mode was selected, and the pilots selected a left turn toward URVIX, the final approach fix. At this point, the aircraft was 8.84 nm from the runway and 1.39 nm right of the final approach course.

Before reaching URVIX, the course deviation indicator began to center, and the flight crew selected NAV mode to intercept the final approach course. The aircraft then began to turn to the right and never intercepted the final approach course. Now the aircraft was again to the right of course, and 500 feet high on the vertical path.

The PM then activated the DTO function to track directly to the runway, without visual contact. The aircraft continued to descend at 1,300 fpm. At 1,200 feet agl, the captain “asked ACC for clearance to conduct a go-around because of navigation problems.” This conversation lasted 32 seconds. Around six seconds later, the TAWS generated alerts, the captain ordered a go-around, and the first officer disconnected the autopilot, increased the power to maximum and increased the pitch and executed a go-around. At the time of the go-around, the aircraft was only 405 feet agl and positioned outside of the obstacle clearance area of the approach.

Notably, the airline’s SOPs did include stabilized approach criteria with the following statement: “Flight crews will not attempt to salvage a landing from an approach that is not stabilized.”

FMS Training

TSB investigators reviewed the airline’s initial and recurrent training programs and found that although the simulator training included programming the FMS in all phases of flight, it is possible that some pilots did not encounter the specific conditions faced by the incident flight, including:

• A holding pattern on a course that diverges from the final approach path;

• An approach with a holding pattern at the initial approach waypoint, which is also the missed approach waypoint;

• Reprogramming the FMS to recover an approach that does not perform as expected; and

• Synchronization of the heading in the heading entry field in the CMD HDG function when the approach is activated while the aircraft is on a heading that is divergent from the final approach path.

The TSB noted in its findings that “initial and recurrent training on the FMS did not enable the flight crew to recognize the particular subtleties of the system programming, causing a discrepancy between the flight crew’s expectations and the aircraft’s behavior…all leading to a delay in completing critical flight actions.”

Human Factors

TSB investigators also noted that a confluence of interrelated human factors contributed to this incident. Beginning with the FMS programming error and throughout the approach was an escalation of errors that contributed to a loss of situational awareness—both individually and as a crew, attentional narrowing (“tunnel vision”), and a significant increase in workload.

TSB referenced several human factors researchers and offered these definitions for discussion:

Decision-making: A cognitive process that involves identifying and choosing a course of action from several alternatives. Decision-making for pilots occurs in a dynamic environment and consists of four steps: gathering information, processing information, making a decision, and acting on that decision. To do this successfully, pilots need to understand the relevant elements of the environment, grasp the importance, and be able to project their future state.

Situational awareness: Integral to pilot decision making. In a dynamic environment, such as flight operations, situational awareness requires pilots to continuously extract information, integrate this information with previous knowledge to form a coherent mental picture, and from there, anticipate future events.

Shared situational awareness between flight crewmembers depends on the level of congruence between each pilot’s respective awareness of the situation. In that context, communication of available information between pilots is critical so that they have the same understanding of the situation. Flight crewmembers who have a shared situational awareness can anticipate and coordinate their actions to perform in a cohesive and efficient manner.

Information processing and workload: Pilots work in a complex environment that requires monitoring multiple sources and types of information. When pilots receive information that they are expecting, they tend to react quickly, without making mistakes. However, when they receive information that is contrary to their expectations, they are slower to react, and their actions may not be appropriate.

People have a limited attention span and information-processing capacity. Therefore, they may fall into the trap of attentional narrowing or channeling. They focus on certain cues in the environment that they attempt to process, while diverting their attention, intentionally or accidentally, from other cues or tasks.

For example, pilots experiencing a heavy workload may concentrate on certain indicators to the detriment of others. Workload depends on the number of tasks to be completed within a certain period. If the number of tasks to be completed increases or the time available decreases, the workload increases, which can lead to certain tasks being omitted or delayed.

Lessons Learned

According to the TSB report, the aircraft was just 15 to 20 seconds from hitting terrain. Attempts to salvage the approach—by reprogramming the approach or manually attempting to steer the aircraft towards the final approach course—further reduced safety margins. The most prudent course of action would have been to follow the company’s SOPs to execute a go-around when the approach became unstable.

Likewise, to maintain a shared mental model or situational awareness as a crew, during the approach, if any mode changes (lateral or vertical) from the initial planned briefing, then a discontinued approach or go-around should be executed immediately.

The opinions expressed in this column are those of the author and not necessarily endorsed by AIN Media Group.