TSB Final Report Summaries
- Aviation Safety Letter - Issue 2/2014
- Guest Editorial
- Flight Operations
- Maintenance and Certification
- SMS - Working Together for the Safety of Everyone
- TSB Final Report Summaries
- Judgement - Your Decision (TP 5305E)
- Accident Synopses
- Take Five… Gear Down and Locked
- Everything Moves At An Airport. Be Alert! (TP 14010E)
The following summaries are extracted from final reports issued by the Transportation Safety Board of Canada (TSB). They have been de-identified and include the TSB’s synopsis and selected findings. Some excerpts from the analysis section may be included, where needed, to better understand the findings. Unless otherwise specified, all photos and illustrations were provided by the TSB. For the benefit of our readers, all the occurrence titles below are now hyperlinked to the full TSB report on the TSB Web site. —Ed.
On September 1, 2010, at 15:29 EDT, a Eurocopter AS350 B-2 departed on the 85-NM VFR flight from a worksite to the Hydro-Québec helicopter base near Chibougamau, Que., with the pilot and three passengers on board. Approximately 20 NM northwest of the destination, the pilot deviated from the direct route to make a precautionary landing due to reduced visibility in heavy rain and thunderstorms. On final approach to land, and at approximately 70 ft AGL, the pilot lost all visual reference. The aircraft collided with trees coming to rest on its left side. The pilot and the passenger seated in the front were seriously injured. The two passengers seated in the rear suffered minor injuries. The aircraft sustained substantial damage. There was no post-crash fire. The ELT activated on impact. The TSB authorized the release of this report on December 12, 2011.
As no aerodrome forecast (TAF) for Chibougamau (CYMT) was available when the pilot was flight planning early in the morning, the graphic area forecast (GFA) was consulted. The GFA available to the pilot at the time of planning did mention the probability of isolated cumulonimbus clouds with tops to 40 000 ft ASL, 2 SM visibility in thunderstorms, rain and mist. The pilot was aware that the cold front was expected to move through the Chibougamau area around 16:00.
Except for the line of thunderstorms that passed through the worksite at approximately 14:30, visual meteorological conditions (VMC) prevailed throughout most of the day between Chibougamau and the worksite. The pilot did not feel it necessary to obtain a weather update during the day though there were opportunities to do so—at 11:01 when refuelling or at anytime using the satellite telephone. Obtaining a weather update before departing or while en route for the return flight at 15:30 would have made the pilot aware of the significant meteorological information (SIGMET) issued at 14:40 indicating the presence of thunderstorms in the Chibougamau area.
The pilot delayed departure from the worksite until approximately 30 min after the passage of the thunderstorms and associated heavy rain. The speed of the helicopter, however, allowed it to catch up with the front between 40 and 20 NM from destination, where visibility started to decrease: first in light rain, then in moderate rain and, finally, in heavy rain.
When visibility decreased to approximately 1 mi. in moderate rain, the pilot elected to deviate from the direct GPS route toward a blueberry field to execute a precautionary landing and wait for better conditions. At no time prior to this did the pilot think it necessary to change course and fly out of the line of thunderstorms. The pilot knew the terrain well and therefore, at that point in the flight, did not perceive any risk in continuing. When visibility decreased further in heavy rain, the pilot was compelled to land immediately on the gravel road. The pilot was aware that the rain was intensifying as the aircraft approached its destination; however, the pilot was surprised by the suddenness of the decrease in visibility as the decrease had been gradual over the last 20 to 30 NM and the cloud ceiling had remained VMC. Visual reference with the ground and trees was lost while manoeuvring at low speed, on final approach to the road. While in a hover over the trees, 75 ft from the road side, the helicopter descended vertically without the pilot realizing it and struck the trees and then the ground. The helicopter was not equipped with windshield wipers which might have been useful in this phase of flight and in the weather conditions encountered. The decision to deviate out of the weather and land was taken too late.
Some aviation weather forecast products mentioned the thunderstorms in the Chibougamau area but did not specify their location and displacement. There was a noticeable lack of information on the probability of thunderstorms in the CYMT TAF issued at 14:00 and on the displacement of the line of thunderstorms in the SIGMET issued at 14:40. Notwithstanding, the line of thunderstorms associated with the passage of the cold front was noticeable over a period of several hours on satellite imagery, the Canadian Lightning Detection Network (CLDN) and weather radar images. Chibougamau falls outside the coverage area of those radars and any thunderstorms within 40 SM of Chibougamau Airport would not appear on the weather radar imagery.
Although injuries sustained by the two front occupants were serious, they were not life threatening. Rapid rescue response is essential to survivability, especially when occupants are injured. The safety briefings received by passengers prior to flying were useful in providing them with essential information on the ELT, survival equipment, satellite phone and first aid kit. The passengers’ ability to quickly communicate with the operator enabled both the company and first responders to react rapidly: a company helicopter was on site within 40 min of the occurrence and two ambulances were on site within an hour.
Findings as to causes and contributing factors
- Although the pilot was aware of the passage of a cold front forecast for the time of the return flight, a weather update was not obtained as weather at the worksite was VMC throughout most of the day.
- The pilot had not anticipated catching up with the line of thunderstorms which had previously passed over the worksite. The decision to deviate and/or land prior to encountering conditions of reduced visibility in heavy rain was made too late.
- While attempting to execute a landing on a gravel road to wait for the weather to improve, the pilot lost all visual references in conditions of reduced visibility in heavy rain; consequently, the helicopter collided with the trees and ground.
- The pre-flight safety briefings received by the passengers allowed them to quickly communicate their situation and location to the company and first responders. They made use of the survival equipment, satellite phone and first aid kit. The pilot was able to ensure the ELT was ON. Rapid response is crucial to survivability.
Safety Action Taken
Following this occurrence and another fatal occurrence (TSB A10Q0132) involving Hydro-Québec (HQ) employees and flight in poor weather, HQ’s flight safety department conducted a risk assessment of its overall flight operations. The review of its occurrence data highlighted four main safety concerns in its contracted helicopter flight operations. These are:
- flight in poor weather;
- flight within the height–velocity curve;
- takeoff in overweight configuration; and
- operation at less than 11 m from structures.
- HQ has organized information sessions at various HQ locations in order to address the four concerns raised during its risk assessment exercise. These concerns will be addressed with contract helicopter operators as well as HQ users (employees). The objective is not only to discuss HQ’s concerns but also to educate the users by emphasizing their role as passengers and how they may negatively or positively influence the safe outcome of a flight. The first information sessions were held on April 21, 2011 and July 13, 2011. More sessions will be organized in the future.
- The operator has modified the content of the annual pilot training syllabus in order to address safety with regard to pilot decision-making training and inadvertent IMC/low visibility training.
Note: The TSB investigation into this occurrence resulted in a significant report with extensive discussion and analysis on many issues such as controlled flight into terrain (CFIT), helicopter flight data monitoring, enhanced ground proximity warning systems, automation, pilot incapacitation and spatial disorientation, unusual attitude recovery, go-around (GA) procedures, crew resource management (CRM) training, organizational and management information, safety management systems (SMS), crew pairing policy, “just culture”, non-punitive reporting and more. Therefore we could only publish the summary, findings and safety action in the ASL. Readers are encouraged to read the full report, hyperlinked in the title above. —Ed.
On July 23, 2011, at 14:57 NDT, a Sikorsky S-92A helicopter departed the Sea Rose floating production, storage, and offloading vessel, with 5 passengers and 2 flight crew members on board, for St. John’s International Airport (CYYT), N.L. After engaging the GA mode of the automatic flight control system during the departure, the helicopter’s pitch attitude increased to approximately 23° nose-up while in instrument meteorological conditions (IMC). A rapid loss of airspeed occurred. After reaching a maximum altitude of 541 ft ASL (534 ft radar altitude), the helicopter began descending towards the water in a nose-high attitude at low indicated airspeed. The descent was arrested 38 ft above the surface of the water. After approximately 5 s in the hover, the helicopter departed and flew to St. John’s. The helicopter’s transmission limits were exceeded during the recovery. There was no damage to the helicopter and there were no injuries. The TSB authorized the release of this report on June 26, 2013.
Departure profile (derived from flight data recorder (FDR) data)
"Too Low Gear"
|Bar. Altitude||259 ft||386 ft||423 ft||467 ft||521 ft||541 ft||454 ft||329 ft||161 ft||81 ft||54 ft||54 ft|
|Radar Altitude||255 ft||391 ft||424 ft||467 ft||520 ft||533 ft||437 ft||306 ft||152 ft||72 ft||44 ft||38 ft|
|Airspeed||64 kt||58 kt||54 kt||47 kt||37 kt||32 kt||25 kt||27 kt||28 kt||1 kt||0 kt||21 kt|
|Vert. Speed (/min.)||1000 ft||1125 ft||875 ft||750 ft||750 ft||-125 ft||-1375 ft||-1500 ft||-1875 ft||-875 ft||-250 ft||125 ft|
|Eng. Torque (avg.)||84%||60%||58%||52%||60%||54%||52%||56%||97%||130%||102%||78%|
The initial portion of the departure from the SeaRose was hand flown by the captain, who made a rapid application of forward cyclic, at a rate of almost 7°/s, to adopt the accelerating attitude. As the helicopter accelerated through the takeoff safety speed (VTOSS), the captain made a large aft cyclic input at an average rate of 5.6°/s, which caused the helicopter to enter a nose-high, decelerating pitch attitude. As the pitch attitude passed through 2.4° nose-up with airspeed and vertical speed increasing, the captain released the cyclic force trim release button and then engaged the GA mode. The airspeed at the time was 64 kt indicated airspeed (KIAS). Following GA mode engagement, the captain released hand pressure on the cyclic stick, believing that the helicopter would adopt a wings-level, 750 ft per minute (fpm) climb out in accordance with the standard GA profile.
Once the nose-high unusual attitude was recognized, the captain attempted to correct the problem by momentarily depressing the cyclic force trim release button. However, the captain did not set an appropriate attitude, as per the operator’s standard operating procedures (SOPs), to recover from the nose-high unusual attitude that had developed as a result of the initial aft cyclic input. When the captain released the cyclic force trim release button, the helicopter’s airspeed re-referenced to 56 KIAS and it continued to decelerate as a result of the aft cyclic stick position, and, to a lesser extent, as a result of the aerodynamic forces associated with blowback. As the airspeed of the helicopter decreased to within 5 kt of the minimum control speed in IMC (VMINI), the captain momentarily pressed the cyclic force trim release button and made an aft cyclic input. This caused the helicopter’s airspeed to decrease below VMINI, and the helicopter entered a 23° nose-high unusual attitude.
As the helicopter descended towards the water, the captain attempted to recover from the nose-high unusual attitude that had developed following GA mode engagement. However, even though the captain’s attention was focused primarily on the attitude indicator, the captain did not correct the excessive nose-up attitude and did not recognize the severity of the descent until the helicopter descended below the clouds.
In addition, despite the sounding of the aural “don’t sink” alert, there was no initial attempt to arrest the descent, which reached a maximum value of 1 880 fpm, while yawing to the right. It is likely that the captain had difficulties processing the information that was presented on the flight instruments because it was not what the captain was expecting to see. The captain, subtly incapacitated, possibly due to spatial disorientation, did not lower the nose of the helicopter and apply collective in a timely manner to recover from the nose-high unusual attitude. This contributed to the excessive amount of altitude that was lost during the inadvertent descent.
As the helicopter descended below the base of the clouds, its rate of descent peaked at 1 880 fpm, at an altitude of 156 ft above the water. At that rate of descent, the helicopter was less than 5 s from impacting the water. In response to the rapidly approaching water, the captain aggressively pulled on the collective to arrest the descent. The rapid application of collective in order to arrest the inadvertent descent resulted in the transmission torque limits being exceeded. As designed, the occurrence helicopter’s full authority digital engine control (FADEC) system went into blowaway when the rotor speed (Nr) decreased below 100%, with both engines operating. By going into blowaway, the pilots had more power available to them to arrest the descent before water impact. During the rapid application of collective, neither pilot realized that transmission operating limitations had been exceeded during the recovery, and the flight continued back to CYYT.
Findings as to causes and contributing factors
- During the departure procedure, the captain made a large, rapid aft cyclic input just before the cyclic trim button was released and the go-around (GA) mode was engaged, which caused the helicopter to enter a nose-high, decelerating pitch attitude.
- The S-92A’s GA mode is designed with reduced control authority. As a result of this reduced control authority, the helicopter experienced difficulties recovering from the nose-high pitch attitude which occurred following the GA mode engagement.
- As the airspeed of the helicopter decreased to within 5 kt of the minimum control speed in IMC (VMINI), the captain momentarily pressed the cyclic force trim release button and made an aft cyclic input. This caused the helicopter’s airspeed to decrease below VMINI, and the helicopter to enter a 23° nose-high unusual attitude.
- The captain, subtly incapacitated, possibly due to spatial disorientation, did not lower the nose of the helicopter and apply collective to recover from the nose-high unusual attitude. This contributed to the excessive amount of altitude that was lost during the inadvertent descent.
- Contrary to what is stated in the two-challenge rule in the operator’s SK-92 Helicopter Standard Operating Procedures, the first officer did not take control of the helicopter when appropriate action was not taken to recover from the inadvertent descent.
Findings as to risk
- If cockpit and data recordings are not available to an investigation, this may preclude the identification and communication of safety deficiencies to advance transportation safety.
- The S-92A’s enhanced ground proximity warning system provides no warning of an inadvertent descent at airspeeds below 40 KIAS with the landing gear down. As a result, there is increased risk of controlled flight into terrain (CFIT) during those phases of flight.
- If there are delays initiating the CFIT avoidance procedure in response to an enhanced ground proximity warning system alert, there is an increased risk of CFIT.
- If pilots of automated aircraft do not maintain their hands-on visual and instrument flying proficiency, there is increased risk that they will be reluctant to take control and that they will experience difficulties recovering from unexpected flight profiles that require pilot intervention.
- If S-92A pilots do not consult the top portion of the primary flight display to confirm proper autopilot engagement, they may not recognize that the system is degraded or not engaged.
- The S-92A Rotorcraft Flight Manual (RFM) is misleading in that it states that the GA mode can be used to recover from an unusual attitude. The GA mode will not function below 50 KIAS and it is limited in how fast it can make attitude and power changes. As a result, pilots and passengers are at increased risk of collision with terrain if pilots attempt to use the GA mode to recover from an unusual attitude at low altitude.
- If the GA mode is engaged at 55 KIAS, in accordance with the operator’s SK-92 Helicopter Standard Operating Procedures, there is increased risk that the GA mode will disengage as a result of a transitory decrease in airspeed below the VMINI.
- There is no standard procedure at the operator for the use of the cyclic force trim release button during departures. This could lead to difficulties if a rapid transfer of control is required during a departure.
- The lack of standard callouts for pitch deviations increases the likelihood of miscommunication during unusual attitude recoveries.
- There was no formal process in place at the operator to ensure adherence to crew pairing restrictions. As a result, the occurrence first officer was paired with pilots who were not qualified training pilots. Therefore, any possible reduction in risk as a result of this risk control measure was not realized.
- If flight crews do not receive recurrent training in unusual attitude recoveries, they are more likely to experience difficulties recovering from unusual attitudes.
- If flight crew members are not trained to recognize and respond to subtle incapacitation, they may not have the confidence to take control from a more experienced pilot.
- If CRM strategies are not practiced during simulator and flight training, there is increased risk that flight crews will experience breakdowns in CRM that could reduce safety margins.
- If autopilot modes are engaged while one pilot is preoccupied with other duties, that pilot will not be able to properly perform the pilot monitoring functions. This increases the risk that deviations from the standard flight profile will go undetected or will not be detected in a timely manner.
- If actions taken by a company are perceived by employees to be inconsistent with its non-punitive reporting and just culture policy and processes, there is a risk that employees will not report safety occurrences for fear of reprisal.
- If reportable incidents are not reported to the TSB, there is increased likelihood that opportunities to advance Canadian transportation safety will not be realized.
- The rapid application of collective in order to arrest the inadvertent descent resulted in transmission torque limits being exceeded.
- During the rapid application of collective, neither pilot realized that transmission operating limitations had been exceeded during the recovery, and they continued the flight back to CYYT.
- The operator was unaware that the cockpit voice recorder is privileged under the Canadian Transportation Accident Investigation and Safety Board Act.
Safety Action Taken
Following this occurrence, the operator:
- published guidance for its crews on S92 autopilot functions, pilot incapacitation, unusual attitude and recommended recovery procedure;
- made several amendments to its S92 standard operating procedures;
- enhanced its simulator training by including more specific exercises focused on the basic unusual attitude recovery technique, including situations where the pilot flying responds to cues from the pilot monitoring, but does not carry out the correct physical actions to rectify the situation;
- developed a process for ensuring that crew pairing restrictions are followed;
- provided training to all first officers on escalation strategies for communicating concerns to captains;
- established a chief training pilot position; and
- provided training to all employees on a Just Culture program.
Sikorsky Aircraft Corporation
In 2013, Sikorsky issued Temporary Revision 11 to the S-92A RFM. This revision required S‑92A operators to add information to the RFM concerning the use of the coupled flight director and information related to the GA function.
Note: The TSB investigation into this occurrence resulted in a significant report with extensive discussion and analysis on many issues such as communications, aids to navigation, flight recorders, post-impact fires, organizational and management information, self-dispatch, pilot experience, pilot decision-making (PDM), crew resource management (CRM), threat and error management (TEM), aircraft icing and more. Therefore we could only publish the summary, selected parts of the factual information, analysis, findings and safety action in the ASL. Readers are encouraged to read the full report, hyperlinked in the title above. —Ed.
On January 10, 2012, a Piper PA31-350 Navajo Chieftain departed the Winnipeg/James Armstrong Richardson International Airport (CYWG), Man., en route to North Spirit Lake (CKQ3), Ont., with 1 pilot and 4 passengers on board. At 09:57 CST, on approach to Runway 13 at CKQ3, the aircraft struck the frozen lake surface 1.1 NM from the threshold of Runway 13. The pilot and 3 passengers sustained fatal injuries. One passenger sustained serious injuries. The aircraft was destroyed by impact forces and a post-impact fire. After a short period of operation, the ELT stopped transmitting when the antenna wire was consumed by the fire. The TSB authorized the release of this report on September 19, 2013.
History of the flight
The pilot arrived at CYWG at approximately 05:30 to prepare for a 07:30 departure. The flight departed CYWG for CKQ3 at 07:51 on an IFR flight plan. The planned routing was from CYWG to Deer Lake (CYVZ), Ont., with an en route stop in CKQ3 to drop off a passenger. The remaining 3 passengers were then to be flown onward to CYVZ for meetings. En route, the aircraft flew just above the cloud tops at an altitude of 9 000 ft ASL.
The flight arrived in the CKQ3 area at about 09:30, and the pilot broadcast a traffic advisory on the CKQ3 aerodrome traffic frequency (ATF). The airport foreman, who was plowing the runway, advised the pilot that snow clearing was underway and would be completed in about 10 min. The pilot replied indicating intention to delay the landing until snow clearing was completed. The aircraft was heard flying overhead CKQ3 for several minutes, and sounded near and low, but could not be seen due to heavy snow and cloud cover.
Ice was accumulating on the aircraft’s windshield during the delay. The pilot called again several minutes later to ask whether snow clearing was completed. The airport foreman advised the pilot that approximately 60% of the runway had been cleared and that the equipment was in the process of exiting the runway. The pilot commenced the approach. During the approach, the aircraft banked to the left and then steeply to the right before it struck the ice at about 09:57.
Aids to navigation
CKQ3 is not serviced by any ground-based navigational aids. Navigation to CKQ3 was accomplished by the operator’s pilots using their global positioning system (GPS).
The low level airspace in the vicinity of CKQ3 is uncontrolled. The area minimum altitude (AMA) in the vicinity of CKQ3 is 2 700 ft ASL. This altitude is designated to provide terrain clearance for aircraft operating in uncontrolled airspace. Under normal circumstances, pilots operating under IFR are not authorized to descend below the AMA, except in accordance with an approved instrument approach procedure or when operating in visual meteorological conditions (VMC). At an airport with no instrument approach procedure and with the ceiling below AMA, the pilot has the option of diverting the aircraft to an airport that does have an instrument approach or diverting to an area where visual flight rules (VFR) exist.
CKQ3 did not have an approved instrument approach procedure. There was no indication that either the pilot or the operator had developed an improvised instrument approach to CKQ3.
Wreckage and impact information
TSB investigators arrived on scene approximately 26 hr after the accident. The aircraft struck the frozen surface of the lake in a right wing-low attitude at both a high rate of descent and forward speed. Contents of the aircraft, such as baggage and cargo, were found strewn halfway up the wreckage trail, indicating an early breakup of the cockpit and cabin area. The wreckage trail was generally aligned with the extended centreline of the runway. It was approximately 380 ft long, and the aircraft had come to a rest in an upright position, facing a southeasterly direction (Photo 1). Damage to the propellers suggests that the engines were producing power at the time of the impact. A post-impact fire consumed a majority of the aircraft.
Photo 1. Wreckage on site
An approximate 4‑ft section of the right wing leading edge containing the stall warning vane was torn off and found approximately halfway down the wreckage trail. This section of leading edge was not affected by the fire and exhibited some clear and mixed ice that was approximately ⅜ in. thick (Photo 2). The stall warning vane was not heated and exhibited hard packed ice inside the stall warning housing, trapping the vane in a downward position (Photo 3). The left horizontal stabilizer leading edge was also not affected by the fire and exhibited ice accumulation (Photo 4).
Photo 2. Leading edge ice
Many of the aircraft de-ice system components were consumed by the post-impact fire. Other components that were recovered had suffered burn damage to the point that examination and bench testing were inconclusive. The vacuum pumps were recovered along with the engines, and no anomalies were found. An examination of the remaining de-ice boots and plumbing that were not damaged did not reveal any anomalies. Due to the extent of fire damage, it could not be determined whether the aircraft de-ice system had been functioning normally. An inspection of the remaining aircraft wreckage did not reveal any pre-impact anomalies.
Photo 3. Stall warning vane
Photo 4. Ice on the horizontal stabilizer leading edge
Pilot decision-making (PDM)
PDM can be described as making the right choice at the right time and avoiding circumstances that can lead to difficult choices. Many decisions are made on the ground, and a well-informed pre-flight choice avoids the need for a much more difficult in-flight decision.
An important component of PDM is good situational awareness, which requires a pilot to align the reality of a situation with his or her expectations. Inadequate or ineffective PDM can result in operating beyond an aircraft’s capability or a pilot’s abilities.
When conditions are particularly good or bad, the decision to depart is an easy one. However, the decision can become complicated when conditions become marginal. Complicating factors, such as economics, customer commitments and professional obligations, compounded by conditions that do not clearly argue against departing, can interfere with even the most safety-conscious pilot’s decision making.
Klein’sFootnote 1 expectation-primed decision-making is a mature model that describes how skilled professionals make rapid decisions in complex environments. Less experienced crews have fewer prior experiences to draw upon and will have fewer linkages between the current context and their prior experience. Consequently, documented procedures and decision criteria become even more valuable to less experienced crews.
Threat and error management (TEM)
To better understand the role of the crew in managing risk during normal operations, the NASA University of Texas, Human Factors Crew Resource Project has developed the TEM model.
The model is based on the premise that, in every flight, hazards that must be handled by the crew will be present. These hazards increase the risks during a flight and are termed “threats” in the TEM model. Threats include such things as weather conditions, traffic, aircraft serviceability issues, unfamiliar airports, etc. Provided that the crew members have an opportunity to handle the threat, effective management of the hazard leads to a positive outcome with no adverse consequences. However, mismanagement of the threat can lead to crew error, which the crew must also manage. Mismanagement of crew error may lead to an undesired aircraft state, which can lead to an accident. At any point, effective management of the situation by the crew can mitigate the risk, and the situation may be inconsequential.
The TEM model has been widely adopted as the foundation for modern CRM training courses. CRM courses are intended to provide flight crews with practical tools to help them avoid, trap or mitigate threats and errors that are typical in commercial aviation operations. A typical CRM course also includes the core elements of PDM training and expands on those concepts to include a broader understanding of decision-making.
The majority of the pilot’s flying experience was in a training environment, either as a student or an instructor, in VFR weather conditions with less complex aircraft.
At the company, the pilot successfully completed the required training, pilot proficiency check (PPC) and line indoctrination training in excess of that required by the company operations manual (COM). However, transitioning to a job as a pilot with this operator, a Canadian Aviation Regulations (CARs) Subpart 703 air taxi operator, put the pilot in new and more challenging flying environments while operating a more sophisticated aircraft type. Operating single-pilot IFR would have increased the workload and would have made it more difficult to formulate effective solutions to problems as they arose.
The pilot’s multi-engine and instrument flight times on arrival at the company, together with the times accumulated during line indoctrination training, satisfied both the company and CARs experience requirements for single-pilot, multi-engine flight into instrument meteorological conditions (IMC). An analysis of the applicable weather information for the pilot’s flights after completion of line indoctrination training was completed. But because the aircraft’s en route altitudes were not recorded, the investigation could not determine an accurate profile of the pilot’s flight time in IMC or the pilot’s experience in icing conditions while employed at the company.
The flights from December 20, 2011, to January 8, 2012, were conducted to a large extent in uncontrolled airspace and outside of ATC radar coverage. The weather conditions for most of the flights were such that flight into IMC would not have been required. On some flights, ceilings would likely have required flight into IMC and some exposure to icing conditions was likely as well. Overall, the pilot had accumulated flight experience in clouds and icing conditions, but would not have encountered icing conditions as severe as those on the accident flight.
PDM, CRM and TEM training
The operator’s initial pilot training did not include any PDM, CRM or TEM training. Without such training applied to relevant examples of the company’s flight operations, the company’s initial training left inexperienced pilots not always prepared for self-dispatch. Under the current regulations, CARs 703 and 704 operators are not required to provide CRM training. As a result, there is an increased risk that crews operating under CARs 703 or 704 will experience breakdowns in CRM.
The operator’s PA31-350 pilots were uncertain as to the aircraft’s certification or capability to fly into icing conditions, and as a result, likely did not pass on an understanding of these issues to the occurrence pilot.
The flight departed from the operator’s base in CYWG, where the operator relied on the pilot for operational decisions and self-dispatch. The operator does not haveFootnote 2 any company procedures or tools in place to aid the pilot in deciding whether or not to depart, or to support the pilot by providing information regarding runway conditions. The nature of a self-dispatch system leaves the pilot with the decision as to whether the flight should depart, based on the pilot’s training, experience and operational pressures. The pilot was relatively new to the Piper PA31-350 aircraft type, passenger flights to remote airports and winter operations in icing conditions. This lack of familiarity and experience increased the risk that the flight would depart into conditions beyond the capabilities of the aircraft and the pilot.
The available information indicates that the aircraft was certified and equipped for dispatch and that the pilot met the minimum requirements for dispatch on the accident flight. However, the runway at CKQ3 had not been cleared, and the weather conditions in the area presented significant challenges for single-pilot flight with an aircraft not equipped for continuous flight in icing conditions. Moreover, these challenging conditions arose at or near the destination, making a diversion back to Winnipeg seem a less feasible option once the aircraft had started its descent and had started to accumulate ice.
The most likely scenario is that the flight proceeded normally until the aircraft started its descent into the North Spirit Lake area. During the descent, the pilot learned that the flight would have to hold until the runway was cleared of snow. The aircraft began to accumulate ice, and its ability to climb back on top of cloud would have diminished.
The pilot, anxious to complete the flight successfully, likely did not appreciate the extent of the aircraft’s limitations in icing conditions, and believed that the best option was to continue to CKQ3 and hold, then land once the runway was clear.As the descent continued below the AMA, the aircraft would have continued to accumulate ice, especially on areas such as the wing root sections that did not have the benefit of de-ice capability. The pilot, occupied with the hold and approach, likely no longer had the situational awareness to fully consider the other options of diverting the flight to either CYRL or CYVZ, and continued in a gradually deteriorating flight situation.
By the time the runway was clear, the aircraft would have accumulated a significant amount of ice. As the aircraft manoeuvred onto final approach, the turns and changes in the aircraft configuration likely added enough drag to cause the aircraft to stall at an altitude from which recovery by the pilot was not possible.
Findings as to causes and contributing factors
- The pilot’s decision to conduct an approach to an aerodrome not serviced by an IFR approach in adverse weather conditions was likely the result of the pilot’s inexperience and may have been influenced by the pilot’s desire to successfully complete the flight.
- The pilot’s decision to descend into cloud and continue in icing conditions was likely the result of inadequate awareness of the Piper PA31-350 aircraft’s performance in icing conditions and of its de-icing capabilities.
- While waiting for the runway to be cleared of snow, the aircraft held near North Spirit Lake (CKQ3) in icing conditions. The resulting ice accumulation on the aircraft’s critical surfaces would have led to an increase in the aircraft’s aerodynamic drag and stall speed, causing the aircraft to stall during final approach at an altitude from which recovery was not possible.
Findings as to risk
- Terminology contained in aircraft flight manuals and regulatory material regarding “known icing conditions,” “light to moderate icing conditions,” “flight in,” and “flight into” is inconsistent, and this inconsistency increases the risk of confusion as to the aircraft’s certification and capability in icing conditions.
- If confusion and uncertainty exist as to the aircraft’s certification and capability in icing conditions, then there is increased risk that flights will dispatch into icing conditions that exceed the capability of the aircraft.
- The lack of procedures and tools to assist pilots in the decision to self-dispatch leaves them at increased risk of dispatching into conditions beyond the capability of the aircraft.
- When management involvement in the dispatch process results in pilots feeling pressure to complete flights in challenging conditions, there is increased risk that pilots may attempt flights beyond their competence.
- Under current regulations, Canadian Aviation Regulations (CARs) 703 and 704 operators are not required to provide training in CRM, PDM or TEM. A breakdown in CRM or PDM may result in an increased risk when pilots are faced with adverse weather conditions.
- Descending below the area minimum altitude while in instrument meteorological conditions without a published approach procedure increases the risk of collision with terrain.
- If on-board flight recorders are not available to an investigation, this unavailability may preclude the identification and communication of safety deficiencies to advance transportation safety.
Safety action taken
NAV CANADA has published an approved instrument approach procedure for the North Spirit Lake aerodrome in the April 2012 revision of the Canada Air Pilot.
- The operator has revised its operations manual and implemented a multi-crew policy that applies to all IFR flights.
- The operator has amended its flight training record keeping procedures by changing the training forms to make it easier and more efficient to prove that all required training has been completed.
- The operator has updated the captain’s trip report form to include provisions for progressive fuel-state monitoring.
- The operator has revised its operational flight plan form to include the calculated landing weight and landing centre of gravity.
On May 25, 2012, a de Havilland DHC-2 Mk.1 Beaver floatplane departed Edgar Lake, Ont., with two passengers and 300 lb of cargo on board. The aircraft was destined for the company’s main base located on Lillabelle Lake, Ont., approximately 77 mi. to the south. On arrival, a southwest-bound landing was attempted across the narrow width of the lake, as the winds favoured this direction. The pilot was unable to land the aircraft in the distance available and executed a go-around. At 14:08, EDT, shortly after full power application, the aircraft rolled quickly to the left and struck the water in a partially inverted attitude. The aircraft came to rest on the muddy lake bottom, partially suspended by the undamaged floats. The passenger in the front seat was able to exit the aircraft and was subsequently rescued. The pilot and rear-seat passenger were not able to exit and drowned. The ELT activated on impact. The TSB authorized the release of this report on September 19, 2013.
The investigation determined that the aircraft was maintained and operated in accordance with existing rules and regulations. The analysis focuses on the pilot, the particular circumstances that led to the aircraft impacting the water and the underlying systemic safety issues within the floatplane industry.
The wind at the time of the occurrence was very strong and gusty. While these conditions were known to the pilot, changes in wind speed and direction, as well as the mechanical turbulence caused by the wind’s passage over obstacles on the windward side of the approach, would have made for challenging landing conditions.
There likely was an increase in headwind, which in turn increased the float time of the aircraft while in the landing flare. As the available landing distance was used up in this landing flare, the pilot decided to conduct a missed approach, applied power and increased the aircraft angle of attack. It is possible that the pilot inadvertently allowed the aircraft speed to bleed off, or perhaps a change in the headwind component due to gusty winds (wind shear) resulted in a sudden drop in airspeed below the stall speed. The rapid application of full power caused the aircraft to yaw to the left, and a left roll quickly developed. This movement, in combination with a high angle of attack and low airspeed, likely caused the aircraft to stall. The altitude available to regain control before striking the water was insufficient. The aircraft was not equipped with a stall warning system, which might have given the pilot additional warning of an impending stall.
The rear-seat passenger did not have an upper body restraint and suffered a serious head injury when the aircraft struck the water. This injury rendered the passenger unconscious, which resulted in drowning. This passenger was seated next to the only operational exit. Even though this door was operational, the physical obstacle of the unresponsive passenger might have made this exit unusable.
Due to the damage to the pilot’s door, significant torque on the handle was required to open it. As well, the original small recessed rotary interior door handles on this aircraft had not been replaced with ones that are more accessible and easier to operate. Either of these factors might have prevented the pilot from opening the door. The pilot survived the impact, but was unable to exit the aircraft, possibly due to difficulties finding or opening an alternate exit. The pilot subsequently drowned. Commercial seaplane pilots who do not receive underwater egress training are at increased risk of being unable to exit the aircraft following a survivable impact with water.
The pilot did not provide a full safety briefing to the passengers before takeoff, possibly because they were frequent travellers. However, the passengers were not aware of the location of the life preservers, and the front-seat passenger was not aware of the shoulder harnesses. The injuries received by the front passenger were likely aggravated by the fact that the available shoulder harness was not worn. Not wearing a shoulder harness can increase the risk of injury or death in an accident.
The floatplane, shown here after being removed from the water, was heavily damaged in the crash.
Findings as to causes and contributing factors
- On the windward side of the landing surface, there was significant mechanical turbulence and associated wind shear caused by the passage of strong gusty winds over surface obstructions.
- During the attempted overshoot, the rapid application of full power caused the aircraft to yaw to the left, and a left roll quickly developed. This movement, in combination with a high angle of attack and low airspeed, likely caused the aircraft to stall. The altitude available to regain control before striking the water was insufficient.
- The pilot survived the impact but was unable to exit the aircraft, possibly due to difficulties finding or opening an exit. The pilot subsequently drowned.
- The rear-seat passenger did not have a shoulder harness and was critically injured. The passenger’s head struck the pilot’s seat in front; this passenger did not exit the aircraft and drowned.
Findings as to risk
- Without a full passenger safety briefing, there is increased risk that passengers might not use the available safety equipment or be able to perform necessary emergency functions in a timely manner to avoid injury or death.
- Not wearing a shoulder harness can increase the risk of injury or death in an accident.
- Not having a stall warning system increases the risk that the pilot might not be aware of an impending aerodynamic stall.
- Commercial seaplane pilots who do not receive underwater egress training are at increased risk of being unable to exit the aircraft following a survivable impact with water.
Safety action taken
Following the occurrence, the company began providing a printed graphic area forecast (GFA) to pilots each morning. All pilots are required to sign the printed weather report and verify that conditions are suitable for the planned flight.
Safety action required
Underwater egress training for commercial flight crews
Seaplane travel is common in Canada, particularly in British Columbia. In the Vancouver Harbour area alone, there are about 33 000 floatplane movements per year, carrying approximately 300 000 passengers.
The Transportation Safety Board of Canada (TSB) has found that the risk of drowning for occupants involved in seaplane accidents is high. TSB and British Columbia Coroners Service data show that, over the last 20 years, about 70% of the fatalities resulting from accidents where aircraft crashed and were submerged in water were attributed to drowning. Half of the deceased were found in the submerged wreckage. While it could not be determined in all cases, some investigations found that the occupants were conscious and able to move around the cabin before they drowned. These past occurrences validate the probability that able-bodied persons can be trapped in sinking aircraft and drown as a result.
This investigation concluded that the pilot survived the impact, but was unable to locate a suitable exit and drowned. Pilots who receive underwater egress training have a greater probability of escaping from the aircraft and a greater chance of surviving the accident.
Transport Canada (TC) has recognized the critical importance of underwater egress training; however, such training remains voluntary. TC indicated that a process is currently underway to initiate the drafting of new regulations requiring underwater egress training using an accelerated procedure, but it did not provide a timeframe for these actions.
The TSB is concerned that pilots who have not received training in underwater egress may not be able to exit the aircraft and subsequently help passengers to safety. Therefore, the Board recommends that:
The Department of Transport require underwater egress training for all flight crews engaged in commercial seaplane operations. (A13-02)
Transport Canada Response
Transport Canada is currently drafting a proposed regulation that will introduce mandatory emergency underwater egress training for flight crews of commercially operated fixed wing seaplanes (Subpart 703 and 704) by amending current mandatory emergency training set out in the Standard 723 Aeroplanes and Standard 724 Aeroplanes of the Canadian Aviation Regulations.
The proposed regulation makes egress training mandatory for initial training, with recurrent training required every 3 years thereafter on an ongoing basis.
The proposed regulation is anticipated to be pre-published in the Canada Gazette Part I in summer 2014.
Passenger shoulder harnesses
The TSB has found that the risk of serious injury or death is increased for occupants of light aircraft who are not wearing upper-torso restraints or shoulder harnesses. The results of previous safety studies completed by the TSB (Aviation Safety Study SA 9401, TP 8655E) have been more recently supported by a Federal Aviation Administration (FAA) study into fatal and serious injury accidents in Alaska.
A significant portion of the commercial floatplane fleet in Canada was manufactured before shoulder harnesses were required for passenger seats and remains in this configuration today.
In the event of a seaplane accident, the occupants of the aircraft may drown if they are unconscious; loss of consciousness is normally caused by head trauma. If restrained and protected during the impact sequence, occupants might maintain consciousness and stand a better chance of successfully exiting a sinking aircraft. The use of a three-point safety restraint (safety belt and shoulder harness) is known to reduce the severity of upper body and head injuries and more evenly distribute impact forces.
The TSB has previously recommended (A94-08, A92-01) that small commercial aircraft be fitted with seatbelts and shoulder harnesses in all seating positions. Following these recommendations, changes to regulations were made to require shoulder harnesses in all commercial cockpits and on all seats in aircraft with 9 or fewer passengers manufactured after 1986. This regulatory change did not address the vast majority of the commercial floatplane fleet, which was manufactured prior to 1986.
The TSB considers that, given the additional hazards associated with accidents on water, shoulder harnesses for all seaplane passengers will reduce the risk of incapacitating injury, thereby improving their ability to exit the aircraft. Therefore, the Board recommends that:
The Department of Transport require that all seaplanes in commercial service certificated for 9 or fewer passengers be fitted with seatbelts that include shoulder harnesses on all passenger seats. (A13-03)
Transport Canada Response
Transport Canada has devoted significant effort to seaplane safety. In 2006 a risk assessment team met to analyze the risks associated with egress from submerged aircraft and identify potential risk reduction measures. The team considered the option of making shoulder restraints available to all occupants. The team’s analysis showed that this option would not reduce the risks by any significant factor.
On August 22-25, 2011, TC inspectors, floatplane industry representatives, and aircraft manufacturers formed a Focus Group which undertook a risk assessment and discussed TSB recommendations to determine what would be the best mitigation strategy to improve levels of safety for commercial seaplane operations in an effective and sustainable way. The group discussed the use of shoulder harnesses but concluded other measures offered more promise than mandating shoulder harnesses.
Most commercially-operated seaplanes in Canada are in the normal/utility category. The cabin designs and configurations of most of these likely do not readily lend themselves to installation of shoulder restraints for all passengers without substantial aeroplane redesign and/or structural modification. Most of the aircraft structures are not robust enough to support shoulder restraints in a crash and may hinder egress. Mandating the retrofitting of shoulder restraints for all occupants is not feasible. Each application to install shoulder harnesses would need to be assessed on a case by case basis.
Since fleet-wide installation of shoulder harnesses is not feasible, Transport Canada will continue its efforts at safety education and promotion.
In December 2013, Transport Canada published a Civil Aviation Safety Alert (CASA) on Safety Belts, and an article in the Aviation Safety Letter (ASL) Issue 4/2013 titled “Shoulder Harnesses and Seat Belts- Double Click for Safety”. Transport Canada will also be revising Advisory Circular (AC) 605-004 Use of Safety Belts by Passengers and Crew Members, to align with Federal Aviation Administration (FAA) AC No.21-34.
Stall warning systems for DHC-2 aircraft
Current regulations require that aircraft certified in the normal, utility, aerobatic, or commuter category be designed with a clear and distinctive stall warning. The stall warning may be furnished either through inherent aerodynamic qualities of the airplane or by a device that gives clearly distinguishable indications.
When the DHC-2 was certified, a stall warning system was not included as it was determined that the aircraft had a natural aerodynamic buffet at low airspeeds and high angles of attack, and that this was a clear and distinctive warning of an impending stall. Therefore, if a pilot does not recognize or misinterprets buffeting as turbulence while at a low airspeed or high angle of attack, there is a risk that the warning of impending stall will go unrecognized. A stall warning system providing visual, aural or tactile warning can give pilots a clear and compelling warning of an impending stall.
A large number of DHC-2 aircraft continue to operate in Canada. The TSB has determined that the frequency and consequences of DHC-2 aircraft accidents following an aerodynamic stall are high.
Stalls encountered during critical phases of flight often have disastrous consequences. Therefore the Board is concerned that the aerodynamic buffet of DHC-2 aircraft alone may provide insufficient warning to pilots of an impending stall.
On June 1, 2012, a Eurocopter AS350-B2 helicopter departed Terrace Airport (CYXT), Terrace, B.C., at 7:54 PDT for a local mountain training flight, with two pilots and one aircraft maintenance engineer (AME) on board. At 8:41, the helicopter struck the snow-covered side of a mountain ravine in daylight conditions at about 4 000 ft ASL. The 406 MHz ELT activated on impact, resulting in the initiation of search activities. A local commercial helicopter operator located the accident site about 1 hr 50 min later. There was no fire. The aircraft was destroyed, and there were no survivors. The TSB authorized the release of this report on November 6, 2013.
An aerial view of the crash site on the mountainside: the tail-end of the helicopter appears as a small dark line on the snow of the mountain valley.
History of the flight
The sole base pilot for the operator at Terrace was preparing to take some leave. In preparation, a training flight was planned to provide a relief pilot with some familiarity with the local area, as well as hover-exit (allowing passengers to exit a helicopter while it is hovering close to the ground) and mountain-flying training. The relief pilot arrived in Terrace the evening before the training flight. The base pilot’s leave was to commence the day after the training flight.
A company flight itinerary was filed with the operator dispatch office in Fort Saint John, B.C., and included the company aircraft maintenance engineer (AME) as a passenger. The flight departed CYXT at 7:54. The helicopter remained within 15 NM of Terrace and proceeded north along the east side of the Kitsumkalum River Valley. Recorded global positioning system (GPS) data from three different on-board units showed some manoeuvres at two locations before the helicopter proceeded westbound across Kitsumkalum River. On the western side of the valley, the helicopter entered a ravine heading southwest and flew along the right-hand or south-facing side of the ravine. Near the top end of the ravine, at about 3 800 ft ASL, the helicopter made a 180° left turn and proceeded part of the way back, in a descent, along the north-facing slope of the ravine. The helicopter then made a right-hand turn, crossed over a ridge and descended into another parallel ravine. The helicopter turned to the southwest again up the ravine and proceeded in a climb, while the ground speed was declining, following the terrain contour along the left side of the ravine.
The helicopter was climbing at about 1 000 ft/min until it quickly leveled off at about 4 500 ft ASL and 45 kt ground speed. It commenced a right-hand turn near the top end of the ravine. As the helicopter turned, it maintained 4 500 ft for about 9 s before it began descending at an accelerating rate, with increasing ground speed and tightening radius of turn. Recovered data recorded at 1-s intervals showed that the helicopter completed a turn of about 285° in 25 s and descended the last 220 ft to the accident site in 3 s (4 400 ft/min). It struck the 30°-inclined, snow-covered slope in a slightly left-of-centre, frontal collision at about 4 000 ft ASL at 8:41.
Plot of GPS data from the occurrence flight
(Image: Google Earth, diagram added by TSB)
The aircraft systems were examined, and no indication of a malfunction was found. The pilots were both experienced, and the training pilot had knowledge of the local area. Neither fatigue nor physiological factors were considered contributory. Therefore, this analysis will focus on the events, conditions and underlying factors that caused or contributed to pilot decision-making (PDM).
The training flight occurred when it did because it was the only opportunity for the relief pilot to receive some additional mountain-flying and hover-exit training, along with a familiarization flight in the local area, before the training pilot left for vacation. It is unusual for a third person to be on board for a pilot training flight. However, given the intent to include hover-exit training, someone was required to perform the exit and entry while the helicopter was in a hover.
Terrace weather conditions and forecasts were suitable for a VFR flight. The pilots were likely aware that the forecast indicated temporary restrictions to ceiling and visibility and potential airframe icing conditions for the area.
As the helicopter climbed, the nature of the snow-covered terrain near the top end of the ravine would have provided fewer and fewer visual references to aid in a pilot’s depth perception. It is probable that the mountain ridges were obscured by overcast ceilings, resulting in whiteout conditions of flat lighting and little or no horizon reference. The records of the flight path indicate a right-hand turn commencing at 4 500 ft ASL as a steady, uniform arc, which is consistent with the flight path of an aircraft entering a spiral dive. The relatively low engine power demand and the lack of any indication of icing on the airframe following the accident suggest that airframe icing was not a factor.
The company and the pilots were authorized to conduct low-visibility operations in uncontrolled airspace. By approving this exception, Transport Canada (TC) authorizes VFR flight operations in instrument meteorological conditions (IMC) at reduced visibilities. Many helicopter operators hold this operations specification, and it is usually applied as an operating standard. In accordance with the conditions of this authorization, the operator had policies, procedures and training in place to serve as defences against weather-related risks. The required pilot training is primarily aimed at PDM skills as a method of avoiding a loss of visual reference. Minimum VFR weather conditions include a minimum visibility requirement as a safety defence against a loss of visual reference.
Operating in conditions with visibility reduced to 0.5 SM increases the risk of inadvertent loss of reference. The low-visibility operations specification allows the visibility to be reduced from 1 SM to 0.5 SM, provided that the pilot has appropriate experience and training and that the helicopter is operated at reduced speed. But it does not require instrument flight proficiency for pilots or the use of aircraft certified for flight in IMC. Research and statistics show that without basic instrument flight training and proficiency, the average time prior to loss of control for VFR pilots can, in most cases, be measured in minutes.
Currently, the risks associated with VFR flight into adverse weather remain substantial, and TC has not indicated that it plans any action to reduce the risks associated with allowing a non-instrument-rated commercial helicopter pilot’s basic instrument flying skills to deteriorate as described in Recommendation A90-81.
In accordance with the company operations manual (COM), the reduction in ground speed as the helicopter climbed up the ravine could indicate that poor visibility conditions were encountered. However, continuing to climb at 1 000 ft/min is not consistent with that hypothesis. The records of the flight path show that the helicopter maintained a relatively steady height above the terrain directly below, but the engine parameters did not indicate that the pilot was demanding any of the excess power available to out-climb the terrain gradient. The rate of climb to 4 500 ft ASL would suggest that the pilots did not assess the conditions they were in as being particularly hazardous. However, the quick level-off at 4 500 ft, coincident with initiating a right-hand turn, would suggest that conditions changed and could indicate that the pilots unexpectedly lost sight of the ground. As soon as sight of the ground is lost, the pilot’s priority would be to regain visual reference by descending, turning or both, while maintaining control of the helicopter. The subsequent flight path of the helicopter indicates that a turn and slow descent were attempted. But during this manoeuvre, the non-instrument-trained pilot flying became disoriented, lost control of the helicopter and collided with the snow-covered terrain.
The remote location of the aircraft battery in the tail boom, combined with the routing of high amperage cables behind and over the cabin, likely mitigated the risk of ignition of the spilled fuel.
The rotor and tail-end of the crashed helicopter, protruding from the snow of the mountainside.
Findings as to causes and contributing factors
- The helicopter likely entered IMC, resulting in the pilot losing visual reference with the ground and becoming disoriented, which resulted in a loss control of the helicopter and collision with terrain.
- Neither pilot held an instrument rating or had any recent instrument flight training, nor was the helicopter equipped for instrument flying, which contributed to the loss of control of the helicopter while flying in IMC.
Findings as to risk
- Operating in conditions with visibility reduced to 0.5 SM increases the risk of inadvertent loss of visual reference.
- The remote location of the aircraft battery in the tail boom, combined with the routing of high amperage cables behind and over the cabin, likely reduced the risk of ignition of the spilled fuel.
Safety action taken
The operator has made the following changes:
- suspended the use of its TC-issued Operations Specification that allows low-visibility operations;
- developed and implemented a pre-flight risk assessment that must be completed before all flights;
- developed a flight-training policies and procedures manual (essential crew only for all training flights);
- implemented a flight data monitoring system;
- purchased an AStar flight simulator, with a main focus on controlled flight into terrain (CFIT) and inadvertent meteorological condition training;
- added a CFIT training course to its annual ground school;
- created a quality assurance position within the flight operations department;
- implemented human factors training, which includes annual decision-making workshops and crew resource management for flight and maintenance personnel;
- increased standard operating procedures to 1-mi. visibility, 500-ft ceiling, and clear of cloud; and
- continued to educate its customers on the risk of flying in low-level or low-visibility operations.
On August 26, 2012, a Cessna 172M departed Springbank Airport (CYBW), Alta., on a VFR flight to conduct a pipeline patrol to the south, through foothill terrain. While the aircraft was circling a pipeline stream crossing on Chaffen Creek, approximately 22 NM west-northwest of Claresholm, Alta., near the Chain Lakes Reservoir, it entered a spin, descended steeply, and collided with terrain at 17:34 MDT. The pilot, who was the sole occupant of the aircraft, sustained fatal injuries. The aircraft was destroyed by impact forces, and there was no post-impact fire. The 406 MHz ELT activated on impact. The accident occurred during daylight hours. The TSB authorized the release of this report on July 17, 2013.
There were no indications that any aircraft systems contributed to the loss of control of the aircraft and its subsequent collision with the ground. Therefore, this analysis will focus on aircraft handling and the environment in which the flight was conducted.
Pipeline reconnaissance at the operator involved photography by a single pilot/observer, which often required that the aircraft be placed in a left turn to give the pilot the best, unobstructed view of a location of interest. Angles of bank during this manoeuvring were often in the area of 45° and at times exceeded 50°. The pilot would have been viewing the outside world through a handheld camera at a time when the aircraft was in a critical phase of flight. At this time, the pilot’s attention would have been distracted from control and monitoring of the aircraft.
There are no data to identify the spin characteristics of the Cessna 172 with the additional fuel tanks. Flight conditions during the stream-crossing reconnaissance and photography were conducive to stall and subsequent spin entry. These conditions would have been a relatively low airspeed/high angle of attack, steep bank angle to the left, moderate engine power and possible excessive left rudder application. The steep descent, short wreckage trail and low ground speed point to a loss of control at low altitude due to aerodynamic stall. Ground scars indicated that the spin rotation had been stopped; however, insufficient height remained to arrest the high rate of descent.
The pilot was highly experienced both in the Cessna 172 and in the pipeline patrol environment, and was familiar with manoeuvring in steep turns at low altitude while inspecting and photographing ground features. The conduct of single‑pilot, low‑level pipeline patrols that include the additional task of photography can increase the potential for distraction from primary flying and increase the risk of loss of control. However, there are no definite explanations for the loss of control on this flight.
The reason for the change in engine noise as the aircraft entered the stall could not be determined. The engine appeared to have operated normally during descent, and there were signatures of high power application on impact. It is unlikely that a power interruption would have caused the pilot to lose control.
Aerial photograph of the accident site
Findings as to causes and contributing factors
- For undetermined reasons, while manoeuvring during low‑level pipeline reconnaissance, control was lost and the aircraft entered an aerodynamic stall and spin.
- Although the pilot was able to arrest the spin, the low altitude of the aircraft prevented recovery from the stall before the aircraft struck the ground.
Findings as to risk
- The conduct of single‑pilot, low‑level aerial inspection flights that include additional tasks beyond flying the aircraft, such as photography, increases the risk of loss of control.
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