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Following the incident, thorough testing revealed that the ILS was misaligned, which led to new regulations for snow clearing around localizer antennas to avoid future disruptions. The event prompted internal reviews at CommutAir to improve pilot training and decision-making under pressure.
Conclusion: The Ripple Effects of a Single Flight
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Understanding the Lessons Learned from CommutAir Flight 4933
On March 4, 2019, CommutAir Flight 4933 experienced a serious accident that serves as a reminder of the critical importance of crew resource management, situational awareness, and adherence to established aviation protocols. The chain of events leading to the incident began not on the day of the flight, but several days earlier when issues were first noticed with the instrument landing system (ILS) at Presque Isle Airport in Maine.
The Prelude to Disaster
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The first officer (FO) involved in the accident had flown into Presque Isle on February 27 and experienced discrepancies between the aircraft's navigation instruments—specifically between GPS and ILS indicators. Upon noticing that the ILS indicated a need for a slight right turn while their GPS devices showed alignment with the runway, both pilots decided to disregard the ILS indications, believing they were more familiar with the local terrain.
Presque Isle, located in a remote area, had no manned air traffic control tower and was covered in deep snow, which likely contributed to the lack of reports regarding the anomalies. The FAA regulations at the time required multiple reports before any action could be taken, and in the case of Presque Isle, only one such report had been filed.
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The Day of the Flight
On the day of the accident, the plane was being piloted by a relatively inexperienced captain and a first officer who had been feeling under the weather. They were tasked with flying the Embraer 145 in snowy conditions, which compounded the already tough approach. In their pre-flight briefings, they noted the predicted weather and runway conditions, receiving various warnings that were all dismissed as manageable.
As they reached the point of descent towards Presque Isle, the first officer began to notice that the ILS needles were reacting differently than expected. Despite previous experiences of navigational confusion, both pilots proceeded, aware yet collectively dismissive of the warnings.
The Approach
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During the approach, the crew seemed confident and followed standard operating procedures. However, critical decisions began to falter. As they descended, they did not establish the necessary visual references—specifically seeing the runway—before passing the minimum altitude for landing.
When the minimum altitude was reached, the first officer indicated he was still relying on instruments, stating they were 'staying on the flight directors' because he didn't have visual contact. Serious misjudgment occurred here, as both pilots should have initiated a go-around due to the lack of visual confirmation.
Immediate Consequences
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As they descended further, both pilots suddenly spotted what they presumed was the runway but was, in fact, a white-out caused by the snowy landscape. In a panic to avoid an imminent collision with what they thought was a tower ahead, the first officer pulled up, drastically reducing speed, and re-engaged the missed approach protocol—but it was too late.
The aircraft impacted the snowy ground approximately 3,600 feet from the runway threshold and 230 feet to the right of the runway edge. Miraculously, all onboard survived, with only minor injuries reported.
Analysis and Recommendations
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Investigations into the incident concluded that the primary cause was the pilot's decision to continue the approach below the minimums without visual confirmation of the runway—exemplified by a psychological phenomenon known as confirmation bias, where the pilots' conviction about the runway's visibility led them to miss critical cues that indicated otherwise.
Key lessons emphasized the silence of previous pilots who noticed the ILS irregularities without reporting, highlighting the significance of proper crew resource management, awareness of instrument anomalies, and vigilance in executing flight protocols—even when conditions seem manageable.
Changes Implemented
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CommutAir Flight 4933 serves as a cautionary tale in aviation: safety depends not just upon compliance with protocols but on ensuring that all personnel feel empowered to report anomalies and voice concerns. Each flight is a shared responsibility where every crew member's input can make a critical difference in the outcome. It reminds us that clear communication, adherence to protocols, and awareness of cognitive biases are crucial in preventing accidents in any operational environment.