Once maintenance was finished and certified, a Cessna 560 Citation Encore was set to conduct an IFR (Instrument Flight Rules) flight from Toronto/Lester B. Pearson International Airport (CYYZ) to Fort Lauderdale Executive Airport (KFXE) in Florida, United States (U.S.).
Prior to the flight, the captain and the first officer each conducted separate walk-around inspections as a part of the pre-flight procedures. Once the passengers had boarded and the baggage was loaded, the captain performed an additional walk-around. The aircraft had five individuals on board, comprising 2 flight crew members and 3 passengers when it departed from Runway 23 at Toronto/Lester B. Pearson International Airport at around 12:00 local time.
Around 12:11 lt, the aircraft unexpectedly yawed and rolled to the left, causing the flight crew to lose control as it quickly descended. The crew declared an emergency by sending a Mayday call to ATC, and at about 3200 feet ASL, they regained control and halted the descent. After regaining control, they requested a diversion to Buffalo Niagara International Airport (KBUF), New York, U.S. Following ATC instructions, the aircraft was directed to runway 23 at Buffalo Niagara International Airport (KBUF), New York, U.S., where it landed safely approximately 30 minutes after the inflight loss of control.
During taxiing to the ramp, a section of the left-hand engine's lower cowl detached from the horizontal stabilizer. This was noticed by the aircraft rescue and firefighting (ARFF) personnel, who alerted the crew that the left-hand engine cowling was missing. It was then discovered that the upper and lower cowlings of the left-hand engine had separated during flight, leading to a loss of control.
All five occupants sustained injuries varying from minor (both flight crew and one passenger) to serious (two passengers.
The aircraft sustained substantial damage;
The left rear fuselage dented
Left-hand side vertical stabiliser dented
The left-hand side vertical stabiliser was punctured and torn at the base (~150 square inches)
The left-hand horizontal stabiliser and elevator were dented and punctured
The aircraft interior had minor damage due to moving objects and occupants during the loss of control.
The accident was investigated by the Transportation Safety Board of Canada (TSB) which released the investigation report into the accident in March 2024. The TSB listed four findings as to causes and contributing factors;
1. During the reinstallation of the lower cowl doors, the non-sequential order in which the fasteners were tightened likely led to a slip of attention that combined with an unclear expectation on the part of both aircraft maintenance engineers about who would be securing the remaining fasteners. As a result, 6 consecutive fasteners were left unsecured.
2. The reinstallation of the left-engine cowl doors and the daily inspection were conducted and certified during the same shift and by the same aircraft maintenance engineer. Given that the cowl door reinstallation was completed as part of the maintenance work at the very end of the work shift, the daily inspection item for checking the condition and security of the engine cowl doors was not performed as a specific, separate operation. As a result, the improperly secured condition of the cowl door went unnoticed.
3. The location of the unsecured fasteners on the cowl door is not easily visible and was not typically checked during pre-flight walkarounds, and no specific guidance on how to look for unsecured fasteners on this aircraft was available to company flight crews. As a result, the unsecured fasteners went undetected by the flight crew despite their multiple walkaround inspections before the occurrence flight.
4. Because some of the fasteners were not secured, there was likely a gap between the cowl door and the nacelle that allowed air to flow inside the nacelle. The cowl doors then partially detached from the nacelle, resulting in the loss of control and rapid descent. Following this, a portion of cowl door became lodged on the horizontal stabilizer and resulted in continued difficulty to control the aircraft.
The report finished with a list of safety actions taken by the operator. The full report, with all investigation details, which served asthe source for this blog can be accessed by clicking on the .pdf file below;
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