What happened
On July 19, 2009, a Beechcraft C90, registration PT-LSO, operated by Líder Taxi Aéreo S.A. - Air Brasil, was performing a passenger transport flight from Minas Novas (SJSK) to Belo Horizonte (SBBH). The aircraft was carrying two crew members and seven passengers.
While climbing through 8,000 feet, the aircraft's main door opened and became completely detached from the airframe, falling into an uninhabited area. Following the separation, the crew initiated an emergency return to the departure aerodrome. The aircraft landed without further incident, sustaining light damage, and all nine occupants remained uninjured.
The investigation
CENIPA investigators examined the aircraft's maintenance history and the physical condition of the recovered door. The investigation revealed that the mechanical locking bayonets were intact and functional, suggesting the door was not forced open by mechanical failure, but rather that the aircraft began the flight with the door unlocked.
Crucially, investigators found that the electrical system designed to alert the crew to the door's status—the "CABIN DOOR" warning light—had been physically disabled. The metallic roller component of the switch had been intentionally cut away, and the associated wiring had been isolated. This prevented the cockpit alarm from activating. Maintenance records also showed a history of discrepancies regarding the door's electrical system, including frequent inadvertent activation of the warning light.
Furthermore, the investigation found significant wear on the mechanical locking components, including an ovalized internal groove and a warped locking lever, which likely contributed to the electrical system's instability.
Findings
- The aircraft began the flight with the main door in an unlocked position.
- The cabin door alarm system was intentionally disabled by cutting the switch mechanism, rendering the cockpit warning light non-functional.
- The crew failed to perform the required pre-flight checklist items, which included physical verification of the door lock and visual inspection of the locking indicators.
- Maintenance history indicated recurring issues with the door's electrical system, which may have led to the decision to isolate the faulty wiring.
- Significant wear was present on the mechanical locking hardware.
Safety action
CENIPA issued the following recommendations to the National Civil Aviation Agency (ANAC):
- Monitor Líder Taxi Aéreo S.A. to ensure the organization demonstrates the capability and resources necessary to provide adequate maintenance services for Beechcraft C90 aircraft in accordance with technical manuals and legislation.
- Emphasize to the company's flight crews the critical importance of strict adherence to operational procedures, specifically the thorough execution of checklists to mitigate the risk of overlooking critical aircraft items.