Investigation Summary
The accident occurred during the flight's second attempt to land at Presque Isle. During the first approach, the captain called for a missed approach after the crew lost sight of what they believed was the runway. On the second attempt, the captain called 'runway in sight' at the decision altitude, but the first officer later reported seeing only 'white on white' due to heavy snow cover. The investigation revealed that the airport's Instrument Landing System (ILS) localizer was misaligned, directing the aircraft approximately 200 feet to the right of the centerline. This misalignment had been noted by other CommutAir pilots on previous flights, including the accident first officer, but had not been formally reported to the FAA. The NTSB found that the captain's decision to continue the approach despite the lack of visual cues, combined with the first officer's fatigue and the technical failure of the ILS, led to the off-runway landing.
Final Conclusions
The NTSB determined the probable cause was the flight crew's decision, due to confirmation bias, to continue the descent below the decision altitude when the runway had not been positively identified. Contributing factors included the first officer's fatigue, which exacerbated the bias, and the captain's poor judgment in instructing the first officer to continue the approach. Additionally, the failure of previous pilots to report the known ILS localizer misalignment prevented corrective maintenance that could have prevented the lateral deviation.
Photographic Evidence (1)
Video Analysis
The Mystery Of The Missing Runway | United Express Flight 4933 — An in-depth look at the 2019 CommutAir accident where an Embraer 145 landed in the snow next to the runway due to ILS misalignment and crew confirmation bias.
If playback is blocked, the owner has disabled embedding — use the link above.
Airframe & Maintenance
Crew Experience
Captain
40 years old; joined CommutAir in 2013.
First Officer
51 years old; joined CommutAir in 2018; reported fatigue and flu symptoms.
Systems & Failure Modes
Instrument Landing System (ILS)
The ground-based system providing lateral (localizer) and vertical (glide slope) guidance. The localizer at Presque Isle was found to be out of tolerance by 200 feet.
Enhanced Ground Proximity Warning System (EGPWS)
Provided the 'minimums' callout during the approach, indicating the aircraft had reached the decision altitude.
Interesting Facts
- 01The ILS localizer was misaligned by approximately 200 feet to the right of the runway centerline.
- 02The first officer had only slept for five hours the night before the accident and was suffering from flu symptoms.
- 03The aircraft came to rest 3,600 feet beyond the runway threshold in a grassy area between the runway and a taxiway.
- 04The captain had a history of training difficulties, including a failed EMB-145 checkride and previous disciplinary monitoring.
- 05The accident first officer had personally experienced the localizer misalignment on a flight to Presque Isle just days before the accident but did not report it.
- 06While the NTSB confirmed 3 minor injuries, initial local news reports cited up to 5 injuries.
Safety Actions & Advisories
Pilot Reporting Procedures
The NTSB highlighted the critical need for pilots to formally report navigation aid discrepancies to the FAA and company dispatch rather than relying on informal cockpit observations.
CommutAir Operational Enhancements
CommutAir implemented new requirements for Presque Isle, including mandatory destination and takeoff alternates, requiring both thrust reversers to be operative, and mandatory review of missed approach actions prior to every approach.
Training and CRM Improvements
The airline enhanced training to include erroneous localizer signal scenarios in simulators, emphasized the use of FMS-extended RNAV centerlines for situational awareness, and incorporated 'top of climb' and 'post flight' CRM/TEM debriefings.
Visual Acquisition Requirements
New procedures require both pilots to visually acquire approach lights before descending below MDA/DH and to acquire the runway environment before continuing to land, with a mandatory 'Verified' callout by the pilot flying.
Location
ACCIDENT SITE · Coordinates taken from the entered by an editor.