Investigation findings into the December 2012 Perimeter Aviation Flight 993 that crashed in Sanikiluaq, Nunavut
The investigations conducted by the Transportation Safety Board of Canada (TSB) are complex, and it is never just one factor that causes an accident. The December 2012 Perimeter Aviation crash in Sanikiluaq, Nunavut, was no exception. There were many factors that caused this accident, the details of which are contained in the 11 findings as to causes and contributing factors.Furthermore, there were 14 additional findings as to risk as well as 1 in other findings.
Findings as to causes and contributing factors
- The lack of required flight documents, such as instrument approach charts, compromised thoroughness and placed pressure on the captain to find a work-around solution during flight planning. It also negatively affected the crew's situational awareness during the approaches at CYSK (Sanikiluaq).
- Weather conditions below published landing minima for the approach at the alternate airport CYGW (Kuujjuarapik) and insufficient fuel to make CYGL (La Grande Rivière) eliminated any favourable diversion options. The possibility of a successful landing at CYGW was considered unlikely and put pressure on the crew to land at CYSK (Sanikiluaq).
- Frustration, fatigue, and an increase in workload and stress during the instrument approaches resulted in crew attentional narrowing and a shift away from well-learned, highly practiced procedures.
- Due to the lack of an instrument approach for the into-wind runway and the unsuccessful attempts at circling, the crew chose the option of landing with a tailwind, resulting in a steep, unstable approach.
- The final descent was initiated beyond the missed approach point and, combined with the 14-knot tailwind, resulted in the aircraft remaining above the desired 3-degree descent path.
- Neither pilot heard the ground proximity warning system warnings; both were focused on landing the aircraft to the exclusion of other indicators that warranted alternative action.
- During the final approach, the aircraft was unstable in several parameters. This instability contributed to the aircraft being half-way down the runway with excessive speed and altitude.
- The aircraft was not in a position to land and stop within the confines of the runway, and a go-around was initiated from a low-energy landing regime.
- The captain possibly eased off on the control column in the climb due to the low airspeed. This, in combination with the configuration change at a critical phase of flight, as called for in the company procedures, may have contributed to the aircraft's poor climb performance.
- A rate of climb sufficient to ensure clearance from obstacles was not established, and the aircraft collided with terrain.
- The infant passenger was not restrained in a child restraint system, nor was one required by regulations. The infant was ejected from the mother's arms during the impact sequence, and contact with the interior surfaces of the aircraft contributed to the fatal injuries.
Findings as to risk
- If instrument approaches are conducted without reference to an approach chart, there is a risk of weakened situational awareness and of error in following required procedures, possibly resulting in the loss of obstacle clearance and an accident.
- If additional contingency fuel is not accounted for in the aircraft weight, there is a risk that the aircraft may not be operated in accordance with its certificate of airworthiness or may not meet the certified performance criteria.
- If Transport Canada crew resource management (CRM) training requirements do not reflect advances in CRM training, such as threat and error management and assertiveness training, there is an increased risk that crews will not effectively employ CRM to assess conditions and make appropriate decisions in critical situations.
- If a person assisting another is seated next to an emergency exit, there is an increased risk that the use of the exit will be hindered during an evacuation.
- If a person holding an infant is seated in a row with no seat back in front of them, there is an increased risk of injury to the infant as no recommended brace position is available.
- If young children are not adequately restrained, there is a risk that injuries sustained will be more severe.
- If a lap-held infant is ejected from its guardian's arms, there is an increased risk the infant may be injured, or cause injury or death to other occupants.
- If more complete data on the number of infants and children travelling by air are not available, there is a risk that their exposure to injury or death in the event of turbulence or a survivable accident will not be adequately assessed and mitigated.
- If temperature corrections are not applied to all altitudes on the approach chart, there is an increased risk of controlled flight into terrain due to a reduction of obstacle clearance.
- If the missed approach point on non-precision instrument approaches is located beyond the 3-degree descent path, there is an increased risk that a landing attempt will result in a steep, unstable descent, and possible approach-and-landing accident.
- If there is not sufficient guidance in the standard operating procedures, there is a risk that crews will not react and perform the required actions in the event that ground proximity warning system warnings are generated.
- If standard operating procedures, the Airplane Flight Manual and training are not aligned with respect to low-energy go-arounds, there is a risk that crews may perform inappropriate actions at a critical phase of flight.
- If non-compliant practices are not identified, reported, and dealt with by a company's safety management system, there is a risk that they will not be addressed in a timely manner.
- If Transport Canada's oversight is dependent on the effectiveness of a company's safety management system's reporting of safety issues, there is a risk that important issues will be missed.
Other findings
- The quick response of the people on the ground reduced the exposure of passengers and crew to the elements.