North Star DC3T at Sachigo Lake on Dec 3rd 2019, aircraft contacted trees on approach
Last Update: August 4, 2022 / 16:32:30 GMT/Zulu time
Incident Facts
Date of incident
Dec 3, 2019
Classification
Accident
Airline
North Star Air
Departure
Red Lake, Canada
Destination
Sachigo Lake, Canada
Aircraft Registration
C-FKAL
Aircraft Type
BASLER BT-67 Turbo 67
ICAO Type Designator
DC3T
The airline reported: "North Star Air is reporting that one of the company's Basler BT-67 cargo aircraft was involved in an accident near Sachigo Lake, Ontario. The accident happened at approximately 9:10am local time on December 3, 2019. There were no passengers onboard the aircraft and both flight crew members sustained no injuries." The Canadian TSB opened an investigation.
The Canadian TSB so far has not mentioned the occurrence (neither on their Twitter feed, their daily log nor their website) nor that they deployed investigators on site or opened an investigation.
NAV Canada reported: "A North Star Air Douglas DC3C (C-FKAL) on a flight to Sachigo Lake, ON (CZPB) crashed in the vicinity of Sachigo Lake, ON (CZPB). No injuries. No impact to operations." and provided as accident time 15:35Z.
On Dec 6th 2019 the Canadian TSB reported: "While on approach to CZPB, the aircraft collided with terrain approximately 500 metres southwest of the threshold of Runway 10. The 2 flight crew members received no injuries. The aircraft sustained substantial damage. The TSB is investigating."
Sachigo Lake is located about 180nm north of Red Lake and features a gravel runway 10/28 of 1070 meters/3500 feet length.
On Aug 4th 2022 the TSB released their final report concluding the probable causes were:
Findings as to causes and contributing factors
- The decision to depart on, and continue, a visual flight rules flight in instrument meteorological conditions was influenced by a distorted perception of risk resulting from successful past experience in similar situations.
- The captain likely experienced attentional narrowing while carrying out a highworkload visual approach at very low altitude in instrument meteorological conditions. This most likely resulted in an inadvertent but controlled descent that was not detected until the aircraft collided with terrain.
- The result-oriented subculture of some North Star Air’s DC3-TP67 pilots, which emphasized mission completion over regulatory compliance, resulted in visual flight rules flights, such as the occurrence flight, being conducted in instrument meteorological conditions.
- North Star Air’s safety management system did not identify the underlying factors that led to the reported instances of company aircraft operating visual flight rules flights into instrument meteorological conditions, nor were any additional measures taken to monitor its DC3-TP67 operation to ensure flights were being conducted in accordance with regulations. As a result, previously identified unsafe practices persisted, and played a direct role in this occurrence.
Findings as to risk
- If minimal supervision of flight crews occurs within a company’s flight operation, there is a risk that previously identified unsafe or non-compliant practices will persist.
- If pilots of multi-crew aircraft are not provided with, and given an opportunity to practise, modern crew resource management strategies, there is increased risk that safety margins will be compromised because of breakdowns in crew coordination.
- If Transport Canada approves a company’s safety management system without first conducting an in-depth review to ensure that all required elements are present and effective, safety management system enterprises may not have the ability to effectively manage safety.
- If Transport Canada relies on operators to investigate allegations of regulatory noncompliance without monitoring them, there is an increased risk that the unsafe practices that are being investigated will persist.
- If pilots do not file flight plans or flight itineraries, as required by regulations, there is a risk that following an accident search and rescue services will be delayed, reducing the occupants’ chances of survival.
- If cockpit restraint systems do not fully accommodate pilot functional reach or if they are not used correctly, there is an increased risk of injury during an accident.
- If cockpit voice and flight data recordings are not available, it is more difficult to accurately assess crew resource management, standard operating procedure execution and effectiveness, and workload management. As a result, the absence of on-board flight recordings can limit the identification of safety deficiencies and the advancement of safety.
- If aircraft operate with emergency locator transmitters approved under legacy design standards, there remains a risk that potentially life-saving distress signals will not be detected because of damage caused to the emergency locator transmitter system during an accident.
The TSB summarized the ADS-B Data and the pitot static ports as follows:
During the final seconds of recorded ADS-B data, the last 3 recorded data points showed anomalous altitude values. In particular, the data points indicated a sudden 400-foot climb and descent within about 7 seconds. The investigation believed that this was unrealistic and inconsistent with the nature of the crash damage. It was determined, in consultation with Aireon, NAV CANADA’s provider for satellite-based ADS-B services, that the probability of the recorded values being somehow corrupted after transmission by the aircraft was extremely remote. In addition, this anomalous data coincided with the aircraft’s passage over an area of tall trees on the northern edge of the runway clearing; there were no other indications of erroneous data at any other point during the flight. The circumstances therefore suggest a high likelihood that the erroneous pressure altitude data transmitted by the aircraft via ADS-B was the result of damage to the pitot-static tubes just before impact with the ground. The investigation determined that the last 11 minutes of the flight were generally flown only 100 feet or less from treetops, and within 200 feet or less of the ground. During the final turn, the aircraft’s altitude had been steadily decreasing toward terrain over about 10 seconds before reaching one of its lowest points during the entire flight. This position coincided with the last valid altitude data. At that point, the corrected barometric altitude placed the aircraft at or below the estimated height of the treetops.
The DC3-TP37 aircraft’s air data system uses pitot-static tubes to measure altitude. The tubes are mounted on very long supports that hang unusually low below the fuselage, by about 2 feet. They are vulnerable to damage if there is any contact with treetops.
The TSB opened the analysis with this statement: "There was no indication that an aircraft system malfunction contributed to this occurrence.", stated that there were no cockpit voice recorder data available and the ELT had activated but could not be received because the antenna had been ripped off. Large portions of the analysis deal with the company safety culture as well as Transport Canada's oversight over the company.
With respect to the actual circumstances leading to impact with terrain the TSB analysed:
Pilot decision making
The pre-flight weather information available to the captain indicated low ceilings and visibilities reduced in light snow would be encountered on the route from Red Lake Airport (CYRL), Ontario, to Sachigo Lake Airport (CZPB), Ontario. Visual flight rules (VFR) flight in such conditions, especially for a multi-engine, fixed-wing aircraft, would leave very little safety margin to deal with in-flight challenges such as avoiding terrain and obstacles, diverting, dealing with an emergency, etc. However, the risks inherent with a VFR flight along this route in such conditions can be mitigated by operating under instrument flight rules (IFR), greatly enhancing the safety margins.
The investigation determined that, based on the aircraft fuel and cargo load, a suitable alternate aerodrome would have been available for the occurrence flight to be conducted under IFR if an additional 233 pounds of fuel had been uploaded to the aircraft. However, because of the captain’s history of operating under VFR, consideration was not given to determining what IFR options existed prior to departing CYRL. Instead of looking for IFR options, the pilots departed on a VFR flight, without having filed the flight plan or flight itinerary required by regulation and the company’s operations manual.
Shortly after takeoff from CYRL, the aircraft entered, and climbed above, the cloud layers before reaching the planned cruising altitude to CZPB. This action was not in accordance with the regulations governing VFR flight, which require the aircraft be operated clear of cloud and in visual contact with the surface at all times. As the aircraft approached CZPB, the pilots initiated a descent through the cloud layers by reference to their flight instruments.
Once the aircraft broke out of cloud at very low level, the aircraft was not in a position to land and the captain flew a large low-level 360° turn, at a height as low as 100 feet above ground level (AGL), in order to remain clear of cloud. This low-level manoeuvring occurred approximately 400 feet below the minimum altitude required for a commuter flight conducted under VFR in uncontrolled airspace.
After completing the 360° turn, the aircraft was once again not in a position to join the final approach and land on Runway 10. Again, the captain continued operating visually by conducting a low-level manoeuvre similar to a left-hand circuit, which brought the aircraft in close proximity to a significant obstacle (a 150-foot tall tower), in conditions that were below the minimum required meteorological conditions for VFR flight.
As outlined above, a series of operational decisions that were made during this occurrence resulted in increased risk levels. The investigation determined that the captain had a history of conducting VFR flights in instrument meteorological conditions (IMC). Over time, the pilot’s repeated success conducting these types of operations resulted in a reduced perception of risk, which contributed to his willingness to deviate from regulations, despite the well-documented risks associated with operating under VFR in IMC.
Collision with terrain during low-level flight
In the absence of CVR and flight data recorder information, the investigation focused on the meteorological conditions present and the aircraft’s flight profile during the final moments of the flight. The investigation considered the possibility that the aircraft, which was operating at extremely low altitudes, experienced an aerodynamic stall, potentially aggravated by the presence of ice. An in-depth performance analysis concluded that, although the stall margin decreased immediately following the turn from downwind, the stall margin improved as the aircraft descended to near tree-top level in the final moments before the impact. This reduced likelihood of a stall in the final moments is supported by the absence of any audible stall warnings during the flight. Because it is unlikely that a stall occurred, the rest of this section will consequently outline the most likely scenario of what did occur.
After the aircraft’s descent from the enroute altitude, the captain conducted a large lowlevel visual 360° turn in IMC at altitudes considerably lower than the minimum en-route altitude for VFR under Canadian Aviation Regulations (CARs) Subpart 704 and the minimum descent altitude for an instrument approach to Runway 10. Then, at heights that varied between 150 and 225 feet AGL, he flew a circuit-type manoeuvre for landing on Runway 10.
As a result, from the moment that the aircraft descended below the clouds in anticipation of a visual approach, the flight was being conducted at a significantly elevated risk level, outside the safety envelope provided by the regulations. Operating below the minimum altitude and horizontal distance requirements prescribed for VFR flight can lead to controlled flight into terrain (CFIT). At these low altitudes in IMC, the pilots would have had very little time to respond to any unexpected obstacles.
During the unbriefed, ad hoc circuit-type manoeuvre to Runway 10, the aircraft remained within 0.4 nautical miles (NM) of the runway, passing within 0.12 NM of a 150-foot tall tower. As a result, the aircraft, which had operated at low altitude for an extended period of time, was being manoeuvred at a height and a horizontal distance from obstacles that represented a significant risk of collision.
As the aircraft passed abeam the threshold of Runway 10, the captain, seated in the lefthand seat, entered a low-level turn for the final approach. After 2 previous unsuccessful attempts to position the aircraft for landing on Runway 10, it is likely that the captain, who had a history of completing VFR flights in poor weather, was highly motivated to carry out the approach to landing. The captain’s attention was likely fixated on outside references, trying to locate, and position the aircraft for landing on, Runway 10. The high workload resulting from the lack of visual cues during the turn from the downwind leg due to the low visibility, low clouds, and snow-covered terrain could have contributed to attentional narrowing, making it difficult for the captain to accurately assess height, speed, and distance. However, because of previous experience in similar weather conditions, the reduced safety margins went undetected, and the captain continued the attempted visual approach.
Data from the automatic dependent surveillance-broadcast (ADS-B) suggests that the captain was unaware of the aircraft’s exact position relative to Runway 10, possibly believing that the aircraft was lined up for the approach. Unbeknownst to the captain, the aircraft, which had been operating at low level for several minutes, continued descending, making contact with the trees and the terrain, in a more or less level attitude, sliding approximately 350 feet. During this crash sequence, the pitot-static tubes, which inputs to the ADS-B signal, was compromised due to impact with trees.
Aircraft Registration Data
Aircraft registration data reproduced and distributed with the permission of the Government of Canada.
Incident Facts
Date of incident
Dec 3, 2019
Classification
Accident
Airline
North Star Air
Departure
Red Lake, Canada
Destination
Sachigo Lake, Canada
Aircraft Registration
C-FKAL
Aircraft Type
BASLER BT-67 Turbo 67
ICAO Type Designator
DC3T
This article is published under license from Avherald.com. © of text by Avherald.com.
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