What happened
On a scheduled cargo flight from Regina, Saskatchewan, to Hamilton, Ontario, a Boeag 727-227 operated by Kelowna Flightcraft Air Charter Ltd. experienced an inflight incident shortly after takeoff. During the initial climb, the crew observed the illumination of the aft cargo door warning light, accompanied by irregular pressure ratio indications for the number 3 engine.
In response to these indications, the crew elected to shut down the number 3 engine and divert the aircraft to Saskatoon, Saskatchewan. The aircraft landed safely at 0710 central standard time with airport rescue and firefighting services on standby. Upon inspection, the aft cargo door was found to be open, though the handle was stowed in the locked position. There were no injuries resulting from the event, though the door hinges sustained minor damage.
The investigation
The investigation examined the aircraft's maintenance records, flight data, and the mechanical integrity of the cargo door. While the flight crew met all qualification and rest requirements, and the aircraft was maintained according to approved systems, investigators focused on the state of the cargo door prior to departure.
Analysis of the flight data recorder indicated a sudden fluctuation in the number 3 engine pressure ratio approximately two and a half minutes after rotation. Investigators determined that the door's position relative to the engine inlet meant that the opening of the door interrupted the airflow, causing the engine irregularities.
Testing of the door, hinges, and microswitches at the TSB Engineering Laboratory revealed no mechanical defects. While an instructional placard on the door contained wording that the operator interpreted as a specific instruction, the investigation concluded this wording did not contribute to the incident. Instead, it was determined that the door was likely closed but not properly locked during the early morning loading process, and the aerodynamic forces of flight eventually forced the door open.
Findings
- The primary cause of the incident was that the aft cargo door was closed but not locked prior to takeoff.
- Aerodynamic forces during flight caused the unsecured door to open.
- The ground crew failed to verify the security of the cargo door before the aircraft departed.
- The flight crew did not identify the unlocked door during their pre-flight walk-around or notice the warning light before takeoff.
- The lack of a requirement for ramp attendants to verify cargo door security contributed to the error.
Safety action
Following the investigation, Purolator Courier updated its ramp operations manual to include a mandatory checklist. This new procedure requires ramp personnel to verify and initial the security of all cargo doors after every loading operation. Additionally, the TSB issued occurrence bulletins to alert the aviation community regarding cargo door closing procedures and the potential for misleading instructional placards.