Charter/Taxi (Non Scheduled Revenue Flight)

The failure of both pilots to see and avoid the other airplane.
Contributing to the accident were:
1) the PA-12 pilot’s decision to fly with a known severe vision deficiency that had resulted in denial of his most recent application for medical certification and
2) the Federal Aviation Administration’s absence of a requirement for airborne traffic advisory systems with aural alerting among operators who carry passengers for hire.

The failure of the pilots of both airplanes to see and avoid the other airplane.

The accident was the consequence of a controlled flight into terrain.
The following contributing factors were identified:
• While the pilot was operating in the vicinity of Lockhart River Airport, there were areas of cloud and rain that significantly reduced visibility and increased the risk of controlled flight into terrain.
In particular, the aircraft probably entered areas of significantly reduced visibility during the second approach.
• After an area navigation (RNAV) global satellite system (GNSS) approach to runway 30 and missed approach, the pilot immediately conducted another approach to the same runway that was on a similar gradient to the recommended descent profile but displaced about 1,000 ft below that profile. While continuing on this descent profile, the aircraft descended below a segment minimum safe altitude and the minimum descent altitude, then kept descending until the collision with terrain about 6 km before the runway threshold.
• Although the exact reasons for the aircraft being significantly below the recommended descent profile and the continued descent below the minimum descent altitude could not be determined, it was evident that the pilot did not effectively monitor the aircraft’s altitude and descent rate for an extended period.
• When passing the final approach fix (FAF), the aircraft’s lateral position was at about full-scale deflection on the course deviation indicator (CDI), and it then exceeded full-scale deflection for
an extended period. In accordance with the operator’s stabilized approach procedures, a missed approach should have been conducted if the aircraft exceeded half full-scale deflection at the FAF, however a missed approach was not conducted.
• The pilot was probably experiencing a very high workload during periods of the second approach. In addition to the normal high workload associated with a single pilot hand flying an approach in instrument meteorological conditions, the pilot’s workload was elevated due to conducting an immediate entry into the second approach, conducting the approach in a different manner to their normal method, the need to correct lateral tracking deviations throughout the approach, and higher than appropriate speeds in the final approach segment.
• The aircraft was not fitted with a terrain avoidance and warning system (TAWS). Such a system would have provided visual and aural alerts to the pilot of the approaching terrain for an extended period, reducing the risk of controlled flight into terrain.
• Although the aircraft was fitted with a GPS/navigational system suitable for an area navigation (RNAV) global satellite system (GNSS) approach and other non-precision approaches, it was not fitted with a system that provided vertical guidance information, which would have explicitly indicated that the aircraft was well below the recommended descent profile. Although the operator had specified a flight profile for a straight-in approaches and stabilized approach criteria in its operations manual, and encouraged the use of stabilized approaches, there were limitations with the design of these procedures. In addition, there were limitations with other risk controls for minimizing the risk of controlled flight into terrain (CFIT), including no procedures or guidance for the use of the terrain awareness function on the aircraft’s GNS 430W GPS/navigational units and limited monitoring of the conduct of line operations.

Other factors that increased risk:
• Although an applicable height of 1,000 ft for stabilized approach criteria in instrument meteorological conditions has been widely recommended by organizations such as the International Civil Aviation Organization for over 20 years, the Civil Aviation Safety Authority had not provided formal guidance information to Australian operators regarding the content of stabilized approach criteria. (Safety issue)
• The Australian requirements for installing a terrain avoidance and warning system (TAWS) were less than those of other comparable countries for some types of small aeroplanes conducting air transport operations, and the requirements were not consistent with International Civil Aviation Organization (ICAO) standards and recommended practices. More specifically, although there was a TAWS requirement in Australia for turbine-engine aeroplanes carrying 10 or more passengers under the instrument flight rules:
- There was no requirement for piston-engine aeroplanes to be fitted with a TAWS, even though this was an ICAO standard for such aeroplanes authorized to carry 10 or more passengers, and this standard had been adopted as a requirement in many comparable countries.
- There was no requirement for turbine-engine aeroplanes authorized to carry 6–9 passengers to be fitted with a TAWS, even though this had been an ICAO recommended practice since 2007, and this recommended practice had been adopted as a requirement in many comparable countries. (Safety Issue)

Other findings:
• The forecast weather at Lockhart River for the time of the aircraft’s arrival required the pilot to plan for 60 minutes holding or diversion to an alternate aerodrome. The aircraft had sufficient fuel for that purpose; and the aircraft had sufficient fuel to conduct the flight from Cairns to Lockhart River and return, with additional fuel for holding on both sectors if required.
• There was no evidence of any organizational or commercial pressure to conduct the flight to Lockhart River or to complete the flight once to commenced.
• Based on the available evidence, it is very unlikely that the pilot was incapacitated or impaired during the flight.
• There was no evidence of any aircraft system or mechanical anomalies that would have directly influenced the accident. However, as a consequence of extensive aircraft damage, it was not possible to be conclusive about the aircraft’s serviceability.
• The aircraft was fitted with Garmin GNS 430W GPS/navigational units that could be configured to provide visual (but not aural) terrain alerts. However, it could not be determined whether the
terrain awareness function was selected on during the accident flight.

The flight crew's failure to stop the airplane on the available runway, which was wet and resulted in the airplane impacting a ditch.

The aircraft stalled during initial climb because its total weight was above the MTOW and the CofG was well beyond the aft limit. The crew failed to prepare the flight according to procedure and, failed to proceed with a mass and balance calculation and the passengers and lugages were incorrectly placed in the cabin according to the CofG.

The investigation determined that the accident was caused by the following probable cause(s):
- Loss of in-flight control as a result of slowing below Minimum Control Speed and drag, generated by the failure of the right engine (No. 2).
- Failure of engine No. 2, due to lack of lubrication, possibly caused by oil leakage through an 11.5 mm fracture, found in one of the sides of cylinder No. 2 at the height of the intake valves.
- Inappropriate application by the crew of the emergency procedure for landing with an inoperative engine, by not declaring the emergency, not feathering the propeller of the inoperative engine and configuring the aircraft early for landing (with landing gear and flaps) without having a safe runway, making it difficult to control the aircraft and placing it in a condition of loss of lift and control.

Contributing Factors:
- Failure of the operator to emphasize in the crew training program the techniques and procedures to be followed in the event of engine failure, among others, the declaration of emergency to ATC, the flagging of the propeller of the inoperative engine, the care in the application of power to the good engine so as not to increase yaw and not to configure the aircraft until landing has been assured.
- Lack of emergency calls by the crew, which denotes deficiencies in the Operator's Safety Management System, and which prevented the early warning of the aerodrome support services and deprived the crew of possible assistance from other aircraft or from the same operator.

Findings as to causes and contributing factors:
These are conditions, acts or safety deficiencies that were found to have caused or contributed to this occurrence.
1. A fatigue fracture originated in the bolt hole bore of the right-hand wing lift strut’s upper outboard lug plate, and eventually led to an overstress fracture of the right-hand wing lift strut’s upper outboard and inboard lug plates during the left turn prior to the final approach.
2. The failure of the outboard and inboard lug plates led to the separation of the righthand wing lift strut from the wing and, subsequently, the separation of the right wing from the aircraft.

Findings as to risk:
These are conditions, unsafe acts or safety deficiencies that were found not to be a factor in this occurrence but could have adverse consequences in future occurrences.
1. If operational flight plans data and load calculations are not available, there is a risk that, in the event of a missing aircraft or accident, aircraft information, including its number of occupants, route, cargo, and weight and balance information, will not be available for search and rescue operations or accident investigation.

Other findings:
These items could enhance safety, resolve an issue of controversy, or provide a data point for future safety studies.
1. The detailed visual inspection prescribed in the Viking Air Ltd. Supplementary Inspection and Corrosion Control Manual, and required by Airworthiness DirectiveCF2018-4, did not identify cracks that could form in the right-hand wing strut’s upper outboard lug plate.

The pilot’s failure to release the parking brake before attempting to initiate the takeoff, which produced an unexpected retarding force and airplane nose down pitching moment. Also causal was the flight crew’s delayed decision to abort the takeoff, which resulted in a runway excursion. Contributing to the accident was the lack of a NO TAKEOFF annunciation warning that the parking brake was engaged, and lack of a checklist item to ensure the parking brake was fully released immediately before takeoff.

Findings as to causes and contributing factors:
These are conditions, acts or safety deficiencies that were found to have caused or contributed to this occurrence.
1. The pilot’s decision making was influenced by several biases and, as a result, the flight departed and subsequently continued into poor weather conditions in mountainous terrain.
2. The high speed at low altitude and low forward visibility reduced the opportunities for the pilot to take alternative action to avoid terrain.
3. Within the box canyon, the canyon floor elevation increased abruptly within less than 1 NM and the low visibility prevented the pilot from detecting this and taking sufficient actions to prevent collision with terrain.
4. When the pilot turned into the box canyon, the terrain awareness and warning system aural alerts were ineffective in warning the pilot about the rising terrain either because he had already heard multiple similar alerts in the preceding minutes, or because he had silenced the alerts.

Findings as to risk:
These are conditions, unsafe acts, or safety deficiencies that were found not to be a factor in this occurrence but could have adverse consequences in future occurrences.
1. If administrative safety defences are not used as intended, it increases the risk that the hazards associated with the flight will not be identified and mitigated.

Other findings:
These items could enhance safety, resolve an issue of controversy, or provide a data point for future safety studies.
1. The pilot held a valid instrument rating and the aircraft was equipped to fly in instrument meteorological conditions. However, there were no scenarios in the pilot’s flying history on the Cessna 208B Grand Caravan or in his training where a transition from visual flight rules to a flight under instrument flight rules in an emergency was performed.