What happened
On 03 February 2016, a Siai Marchetti SF 260 AM, registration ZU-SFE, was conducting a scheduled test flight from Polokwane International Airport. The flight, operated by Aerosud Aerospace Systems, was being flown by two certified test pilots. After climbing to 6,000 feet AMSL and completing several maneuvers, including a steep turn and an approach to a stall, the aircraft was in straight and level flight at 105 knots.
During this phase of flight, the entire canopy suddenly separated from the airframe. The separation caused the canopy to strike the monitoring pilot, resulting in minor injuries to the left side of their upper body. Despite the loss of the canopy, the pilot in command performed a low-speed handling check, found no further abnormal vibrations or control issues, and successfully returned the aircraft to Poloklanew International Airport. Post-flight inspections noted damage to the vertical stabilizer and the rear fuselage where the canopy had impacted the airframe.
The investigation
SACAA AIID investigators examined the cockpit controls and the canopy mechanism. The investigation focused on the relationship between the canopy emergency release lever and the parking brake lever, which are located adjacent to each other on the center instrument pedestal. While the handles differ in size, their grips are very similar, creating a potential human factors issue.
Investigators found that the emergency release lever was in an extended position, approximately 24 mm from its fully engaged state. The locking wire associated with the lever was stretched and partially severed. Furthermore, the sliding pins on the canopy rail were protruding asymmetrically, indicating that the rail locking pins were not properly engaged with the canopy lugs. While ground crews and pilots had reported that the lever appeared secured and wire-locked during pre-flight checks, the investigation suggested that the visual state of the lever on this aircraft type can be misleading, as the lever does not sit fully flush against the pedestal even in a secure position.
Findings
- The primary cause of the incident was the improper use of the emergency system.
- The canopy rail was not fully secured, likely due to the emergency release lever being partially activated and then returned to a position that appeared locked without the pins re-engaging properly.
- The proximity and similar grip of the canopy emergency release lever to the parking brake lever present a significant human factors risk for inadvertent activation.
- Visual inspections of the locking wire and lever position may be insufficient to confirm the canopy is truly secure, as the lever's resting position varies between aircraft.