RECENTLY RELEASED TSB REPORTS

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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. We encourage our readers to read the complete reports on the TSB Web site. For more information, contact the TSB or visit their Web site at http://www.tsb.gc.ca/. -Ed.

TSB Final Report A05F0025-Hydraulic Flight Control Malfunction

On February 6, 2005, a Canadian-registered EurocopterAS350B2 helicopter was engaged in various mining support activities in the jungle and terrain in the Kamarang area, Guyana. At 17:25local time, with a 120-ft longline attached, the pilot entered a stable, out-of-ground-effect hover to begin coiling the longline onto the ground below the helicopter. As the pilot gradually descended, and at a height of about 10 ft above ground level(AGL), he experienced significant binding in the flight controls. The pilot was unable to rectify the control binding and had considerable difficulty maintaining attitude and altitude control of the helicopter. During 15seconds of random, uncontrolled hover flight, the helicopter turned and climbed to about 20 ft AGL, whereupon the pilot retarded the throttle lever, causing the main rotor rpm to decay rapidly. As a result, the helicopter descended quickly, struck the ground, bounced, and landed upright, causing substantial damage to the skids, the tail boom, and the main rotor head. The pilot was not injured and the impact forces were insufficient to activate the emergency locator transmitter (ELT).

Finding as to causes and contributing factors

  1. The helicopter had a flight control malfunction and the pilot was unable to effectively control the helicopter before it collided with the terrain. The cause of the malfunction could not be determined with certainty, but was most likely a loss of hydraulic pressure.

Findings as to risk

  1. The hydraulic cut-off (HYD CUT OFF) switch is underrated for its application in the AS350, and as a result, is exposed to higher-than-design electrical current draw, leading to intermittent function and premature failure. Failure of the switch can lead to improper operation of the hydraulic system or warning devices.
  2. The two printed circuit boards (22-alpha and 30-alpha) in the centre pedestal were contaminated by debris accumulation. This could lead to an electrical short-circuit resulting in a malfunction of the hydraulic system and its warning systems.
  3. The main rotor hydraulic servo actuators were outof- tolerance for extension and retraction rates and internal leakage, a circumstance that may cause asymmetric servo operation.
  4. The lateral hydraulic servo accumulators differed remarkably in the time required to exhaust them of hydraulic pressure, leading to asymmetric servo operation.
  5. The hydraulic test (HYD TEST) switch is vulnerable to inadvertent operation that has been shown to cause loss of control of the helicopter. The helicopter manufacturer has issued a voluntary Service Bulletin to install a protective cover device over the HYD TEST switch to prevent inadvertent operation. Without the cover, the risk of unintentional use is always present.
  6. The aural warning horn to alert the pilot of low main rotor speed also functions as the low hydraulic pressure warning, a situation that leads to ambiguity and potentially inappropriate response to the actual emergency.
  7. The gross particulate contamination found in the hydraulic system fluid presents a clear risk of servo malfunction and could lead to loss of control; the source of the contamination was not found.
  8. Although the AS350B2 can be controlled without hydraulic servo actuators, it requires the pilot to exert considerable muscular effort, which is difficult to gauge accurately. The required effort may exceed the physical strength or endurance of some pilots.
  9. The lack of a requirement for recurrent AS350 training may result in unacceptable loss of familiarity with the emergency procedures, a loss of awareness of hydraulic system malfunctions, and the unusually high control forces that result. Collectively, these issues could result in a loss-of-control situation.

Safety action taken



TSB Final Report A05F0047-Loss of Rudder in Flight

On March 6, 2005, at 0645Coordinated Universal Time (UTC), an AirbusA310-308 aircraft, departed Varadero, Cuba, for Québec City, Que., with9 crew members and 262 passengers on board. At approximately0702 UTC, the aircraft was 90NM south of Miami,Fla., and in level flight at FL350, when the flight crew heard a loud bang and felt some vibration. The aircraft entered a Dutch roll and the captain disconnected the autopilot to manually fly the aircraft. The aircraft climbed nearly 1 000 ft while the captain tried to control the Dutch roll. The crew initiated a descent back to FL350 and requested further descent and a possible diversion to Fort Lauderdale, Fla. During the descent, the Dutch roll intensity lessened and then stopped when the aircraft descended through FL280. Noemergency was declared. When the aircraft was abeam Miami, the crew decided to return to Varadero. During the landing flare, the rudder control inputs were not effective in correcting for a slight crab. The aircraft landed and taxied to the gate. After shutdown, it was discovered that the aircraft rudder was missing. Small pieces of the rudder were still attached to the vertical stabilizer. One flight attendant suffered a minor back injury during the event.

Findings as to causes and contributing factors

  1. The aircraft took off from Varadero with a preexisting disbond or in-plane core fracture damage to the rudder, caused by either a discrete event, but not a blunt impact, or a weak bond at the z-section of the left side panel. This damage deteriorated in flight, ultimately resulting in the loss of the rudder.
  2. The manufacturer’s recommended inspection program for the aircraft was not adequate to detect all rudder defects; the damage may have been present for many flights before the occurrence flight.
  3. This model of rudder does not include any design features in the sandwich panels to mechanically arrest the growth of disbond damage or in-plane core failure before the damaged area reaches critical size (such a feature was not specifically demanded for certification).

Findings as to risk

  1. A cockpit voice recorder (CVR) with a 30-min recording capacity was installed on the aircraft, and its length was insufficient to capture the rudder-loss event, resulting in critical information concerning the rudder failure not being available to investigators.
  2. There was no published procedure for disabling the recorders once the aircraft was on the ground; valuable investigation information can be lost if the data are not preserved.
  3. The sampling intervals for lateral and longitudinal acceleration captured by the digital flight data recorder (FDR) were insufficient to record the highly dynamic conditions present at the time of the occurrence. This resulted in incomplete information being recorded.
  4. The rudder position filtering and the necessity for additional analysis adversely affected the accuracy and effectiveness of the investigation efforts.
  5. There are insufficient published procedures available to flight crew members to assist in recovering from a Dutch roll.
  6. Declaring an emergency and clearly communicating the nature of the problem allows air traffic control(ATC) to more easily co-ordinate between units and anticipate the needs of the crew in planning traffic management.
  7. Procedures and practices that do not facilitate information sharing between crew members increase the likelihood that decisions will be based on incomplete or inaccurate information, potentially placing passengers and crew at risk.

Other findings

  1. Throughout the event, the crew received no electronic centralized aircraft monitor (ECAM) message relating to the control problem that the aircraft had experienced, and there were no other warning lights or cockpit indications of an aircraft malfunction.
  2. After the rudder-separation event, the aircraft was not in danger of losing the vertical tail plane during the flight, either through loss of static strength or loss of stiffness.

Safety action taken


TSB Final Report A05H0002-Runway Overrun and Fire

On August 2, 2005, an Airbus A340-313 aircraft departed Paris, France, at 1153 Coordinated Universal Time (UTC) on a scheduled flight to Toronto, Ont., with 297 passengers and 12 crew members on board. Before departure, the flight crew members obtained their arrival weather forecast, which included the possibility of thunderstorms. While approaching Toronto, the flight crew members were advised of weather-related delays. On final approach, they were advised that the crew of an aircraft landing ahead of them had reported poor braking action, and the A340’s weather radar was displaying heavy precipitation encroaching on the runway from the northwest. At about 200 ft above the runway threshold, while on the instrument landing system (ILS) approach to Runway 24L with autopilot and auto thrust disconnected, the aircraft deviated above the glide slope and the groundspeed began to increase. The aircraft crossed the runway threshold about 40 ft above the glide slope.

During the flare, the aircraft travelled through an area of heavy rain, and visual contact with the runway environment was significantly reduced. There were numerous lightning strikes occurring, particularly at the far end of the runway. The aircraft touched down about 3 800 ft down the runway, reverse thrust was selected about 12.8seconds after landing, and full reverse was selected16.4seconds after touchdown. The aircraft was not able to stop on the 9000-ft runway and departed the far end at a groundspeed of about 80 kt. The aircraft stopped in a ravine at 2002 UTc (16:02 Eastern Daylight Time [EDT]) and caught fire. All passengers and crew members were able to evacuate the aircraft before the fire reached the escape routes. A total of 2 crew members and 10passengers were seriously injured during the crash and the ensuing evacuation.

photo

Findings as to causes and contributing factors

  1. The crew conducted an approach and landing in the midst of a severe and rapidly changing thunderstorm. The operator did not have procedures related to the distance required from thunderstorms during approaches and landing, nor were these required by regulations.
  2. After the autopilot and auto thrust systems were disengaged, the pilot flying (PF) increased the thrust in reaction to a decrease in the airspeed and a perception that the aircraft was sinking. The power increase contributed to an increase in aircraft energy and the aircraft deviated above the glide path.
  3. At about 300 ft above ground level(AGL), the surface wind began to shift from a headwind component to a 10-kt tailwind component, increasing the aircraft’s groundspeed and effectively changing the flight path. The aircraft crossed the runway threshold about 40 ft above the normal threshold crossing height.
  4. Approaching the threshold, the aircraft entered an intense downpour, and the forward visibility became severely reduced.
  5. When the aircraft was near the threshold, the crew members became committed to the landing and believed their go-around option no longer existed.
  6. The touchdown was long because the aircraft floated due to its excess speed over the threshold and because the intense rain and lightning made visual contact with the runway very difficult.
  7. The aircraft touched down about 3 800 ft from the threshold of Runway24L, which left about 5100 ft of runway available to stop. The aircraft overran the end of Runway24L at about 80-kt and was destroyed by fire when it entered the ravine.
  8. Selection of the thrust reversers was delayed, as was the subsequent application of full reverse thrust.
  9. The pilot not flying (PNF) did not make the standard callouts concerning the spoilers and thrust reversers during the landing roll. This further contributed to the delay in the PF selecting the thrust reversers.
  10. Because the runway was contaminated by water, the strength of the crosswind at touchdown exceeded the landing limits of the aircraft.
  11. There were no landing distances indicated on the operational flight plan for a contaminated runway condition at the Toronto/Lester B. Pearson International Airport (CYYZ).
  12. Despite aviation routine weather reports (METAR) calling for thunderstorms at CYYZ at the expected time of landing, the crew did not calculate the landing distance required for Runway24L. Consequently, they were not aware of the margin of error available for the landing runway, or that it was eliminated once the tailwind was experienced.
  13. Although the area up to 150 m beyond the end of Runway24L was compliant with AerodromeStandardsandRecommendedPractices(TP312E), the topography of the terrain beyond this point, along the extended runway centreline, contributed to aircraft damage and to the injuries to crew and passengers.
  14. The downpour diluted the firefighting foam agent and reduced its efficiency in dousing the fuel-fed fire, which eventually destroyed most of the aircraft.

Findings as to risk

  1. In the absence of clear guidelines with respect to the conduct of approaches into convective weather, there is a greater likelihood that crews will continue to conduct approaches into such conditions, increasing the risk of an approach and landing accident.
  2. A policy where only the captain can make the decision to conduct a missed approach can increase the likelihood that an unsafe condition will not be recognized early and, therefore, increase the time it might otherwise take to initiate a missed approach.
  3. Although it could not be determined whether the use of the rain repellent system would have improved the forward visibility in the downpour, the crew did not have adequate information about the capabilities and operation of the rain repellent system and did not consider using it.
  4. The information available to flight crews on initial approach in convective weather does not optimally assist them in developing a clear idea of the weather that may be encountered later in the approach.
  5. During approaches in convective weather, crews may falsely rely on air traffic control(ATC) to provide them with suggestions and directions as to whether to land or not.
  6. Some pilots are under the impression that ATC will close the airport if weather conditions make landings unsafe; ATC has no such mandate.
  7. Wind information from ground-based measuring systems (anemometers) is critical to the safe landing of aircraft. Redundancy of the system should prevent a single-point failure from causing a total loss of relevant wind information.
  8. The emergency power for both the public address (PA) and evacuation (EVAC) alert systems are located in the avionics bay. A less vulnerable system and/or location would reduce the risk of these systems failing during a survivable crash.
  9. Brace commands were not given by the cabin crew during this unexpected emergency condition. Although it could not be determined if some of the passengers were injured as a result, research shows that the risk of injury is reduced if passengers brace properly.
  10. Safety information cards given to passengers travelling in the flight decks of the operator’s Airbus A340-313 aircraft do not include illustrations depicting emergency exit windows, descent ropes or the evacuation panel in the flight deck doors.
  11. There are no clear visual cues to indicate that some dual-lane slides actually have twolanes. As a result, these slides were used mostly as single-lane slides. This likely slowed the evacuation, but this fact was not seen as a contributing factor to the injuries suffered by the passengers.
  12. Although all passengers managed to evacuate, the evacuation was impeded because nearly 50percent of the passengers retrieved carry-on baggage.

Other findings

  1. There is no indication that the captain’s medical condition or fatigue played a role in this occurrence.
  2. The crew did not request long aerodrome forecast (TAF) information while en route. This did not affect the outcome of this occurrence because the CYYZ forecast did not change appreciably from information the flight crew members received before departure, and they received updated METARs for CYYZ and the Niagara Falls International Airport (KIAG).
  3. The possibility of a diversion required the flight crew to check the weather for various potential alternates and to complete fuel calculations. Although these activities consumed considerable time and energy, there is no indication that they were unusual for this type of operation or that they overtaxed the flight crew.
  4. The decision to continue with the approach was consistent with normal industry practice, in that the crew could continue with the intent to land while maintaining the option to discontinue the approach if they assessed that the conditions were becoming unsafe.
  5. There is no indication that more sophisticated ATC weather radar information, had it been available and communicated to the crew, would have altered their decision to continue to land.
  6. It could not be determined why doorL2 opened before the aircraft came to a stop.
  7. There is no indication that the aircraft was struck by lightning.
  8. There is no information to indicate that the aircraft encountered wind shear during its approach and landing.
  9. The flight crew seats are certified to a lower standard than the cabin seats, which may have been a factor in the injuries incurred by the captain.

Safety action taken

Due to space limitations, we cannot publish the safety action taken section, which includes seven aviation safety recommendations from the TSB. Readers are invited to read this section, and the entire final report of this major investigation, on the TSB Web site at: http://www.tsb.gc.ca/eng/rapports-reports/aviation/2005/a05h0002
/a05h0002.asp
. —Ed.


TSB Final Report A06P0010-Engine Power Loss-Forced Landing

On January 21, 2006, a Cessna 208B aircraft was en route at 9000 ft above sea level(ASL), from Tofino,  B.C., to the Vancouver International Airport, B.C., when the engine failed. The pilot began a glide in the direction of the Port Alberni Regional Airport, B.C., before attempting an emergency landing on a logging road. The aircraft struck trees during a steep right-hand turn and crashed. The accident occurred at about 14:20Pacific StandardTime (PST), approximately 11 NM south-southeast of the PortAlberni RegionalAirport. Five passengers survived with serious injuries; the pilot and the other two passengers were fatally injured.

photo

Findings as to causes and contributing factors

  1. The engine lost power when a compressor turbine blade failed as a result of the overstress extension of a fatigue-generated crack. The fracture initiated at a metallurgical anomaly in the parent blade material and progressed, eventually resulting in blade failure due to overstress rupture.
  2. The combination of aircraft position at the time of the engine failure, the lack of equipment enabling the pilot to locate and identify high terrain, and the resultant manoeuvring required to avoid entering instrument flight conditions likely prevented the pilot from attempting to glide to the nearest airfield.

Findings as to risk

  1. Single-engine instrument flight rules (SEIFR) operations in designated mountainous regions have unique obstacle risks in the event of an engine failure. Canadian equipment requirements for such operations do not currently include independent terrain mapping, such as terrain awareness and warning systems (TAWS).
  2. Airline operators are not currently required to conduct any additional route evaluation or structuring to ensure that the risk of an off-field landing is minimized during SEIFR operations.
  3. Pilots involved in commercialSEIFR operations do not receive training in how to conduct a forced landing under instrument flight conditions; such training would likely improve a pilot’s ability to respond to an engine failure when operating in instrument meteorological conditions (IMC).
  4. Mean time between failure (MTBF) calculations do not take into account in flight shut downs (IFSD) not directly attributable to the engine itself; it may be more appropriate to monitor all IFSD events.
  5. The design of the Cessna 208B Caravan fuel shutoff valves increases the risk that the valves will open on impact, allowing fuel spillage and increasing the potential for fire.

Other finding

  1. The operator was not providing downloaded engine parameter data for engine condition trend monitoring (ECTM) evaluation at appropriate intervals.

Safety action taken

Terrain Awareness and Warning System (TAWS) Equipment Requirement
A requirement for the installation and use of TAWS has been supported by Transport Canada (TC). This installation and use of TAWS equipment will enhance a pilot’s ability to identify and avoid terrain risks in the event of a loss of propulsion under IMC. Information about the TAWS equipment requirements that are being approved for Canada can be found in TC’s CommercialandBusinessAviationAdvisoryCircular (CBAAC)0236 dated29July 2005, which is available on the TC Web site at http://www.tc.gc.ca/eng/civilaviation/standards/commerce-circulars-menu-284.htm

Enhanced Pilot Training Requirement
On June 6, 2007, the TSB sent a Safety Advisory to TC, suggesting that TC consider incorporating additional pilot training requirements into subsection 723.98(24) of the Commercial Air Service Standards(CASS) to ensure that SEIFR pilots receive practical training on engine failure procedures in IMC. The training would include the pilot’s initial response to the failure, the descent in instrument conditions, the avoidance of terrain hazards during the descent, and the practice of forced landings under various degraded surface weather conditions.

TC responded to this Safety Advisory on July 25, 2007. The response outlined a number of difficulties involved in establishing a specific standard that could cover a myriad of circumstances that a pilot may meet in the event of an engine failure under SEIFR operations.

TC’s position is that air operators should be proactive in reviewing their SEIFR operations, specific to their individual training program, to ensure that this possible training gap or related hazard is addressed within the company operations manual.

TC’s Civil Aviation Standards Branch will prepare an issue paper with the recommendation that air operators review their company training programs to ensure that SEIFR pilots receive practical training on engine failure procedures in IMC specific to the air operator operations and geographic location.

www.tsb.gc.ca/eng/rapports-reports/aviation/2006/a06p0010/a06p0010.asp -Ed.

TSB Final Report A06P0157-Collision with Terrain

On August 7, 2006, a float-equipped Cessna A185F departed Nimpo Lake, B.C., at 12:45Pacific Daylight Time (PDT), with only the pilot on board. The pilot was to pick up a passenger at Kluskoil Lake, B.C., and then return to Nimpo Lake. The aircraft was reported overdue at 15:00 PDT, and a search operation was initiated. An emergency locator transmitter (ELT) signal was received, and the aircraft wreckage was located on a hillside in the vicinity of Mount Downton, at an elevation of 6824 ft above sea level (ASL). The aircraft was destroyed, but there was no fire. Both occupants received fatal injuries. The accident happened at about 14:00 PDT.

Aerial view of accident site, with TSB investigators at the approximate impact point
Aerial view of accident site, with TSB investigators at the approximate impact point

Findings as to causes and contributing factors

  1. While flying in mountainous terrain, the pilot was manoeuvring close to terrain, and struck the ground at slow speed, with the aircraft in a nose-down attitude, possibly after a stall.
  2. The pilot’s lack of experience in mountain flying likely caused him to misjudge how close to the terrain he could safely fly. The strong wind from the southeast may have been a factor.


TSB Final Report A06Q0157-Engine Failure

On September10, 2006, a Cessna 172M, with the pilot and two passengers on board, took off at 15:45 Eastern Daylight Time (EDT) from Saint-Hubert, Que., for a flight according to visual flight rules (VFR) over Montréal,Que. About 15 min after takeoff, when the aircraft was over the city, the engine (Lycoming O320- H2AD) lost power and stopped.

The pilot tried to restart it, but without success. The pilot transmitted a distress message and quickly reported the situation to the control tower. The aircraft was approximately 1 250 ft above ground level(AGL) at the time. The pilot landed the aircraft on the northbound side of Parc Avenue, in Montréal. On landing, the left wing tip struck a traffic light post before the aircraft came to rest. The aircraft was substantially damaged, but there were no injuries.

photo of plane

Findings as to causes and contributing factors

  1. The aircraft was not on level ground when the draining was done before the flight. Consequently, the water in the fuel tank was lower than the drain valve and could not be removed with the pipette.
  2. The water accumulated in the right fuel tank migrated to the gascolator bowl, saturating it, and causing the engine to stop.

Findings as to risk

  1. The inspections done by the approved maintenance organization (AMO) and the pilot did not find that the fuel filler cap chain for the right fuel tank was missing. As a result, the chain was exposed to the water in the bottom of the tank, and the fuel was contaminated by corrosion from the chain hooks.
  2. On the Cessna 172, the location of the gascolator drain valve makes it hard to collect fuel for visual examination before flight.
  3. The Canadian Aviation Regulations(CARs) do not require aircraft owners to comply with service bulletins. As a result, ServiceBulletinSEB92-26 was not completed on the occurrence aircraft. This upgrade would have made it possible to properly drain the water that had accumulated in the right fuel tank before the flight.


TSB Final Report A07W0005-Landing Short of Runway

On January 9, 2007, a BritishAerospace Jetstream3112 was conducting an instrument approach to Runway29 at Fort St.John, B.C., on a scheduled instrument flight rules (IFR) flight from GrandePrairie,Alta. At 11:33 Mountain Standard Time (MST), the aircraft touched down 320 ft short of the runway, striking approach and runway threshold lights. The right main and nose landing gear collapsed, and the aircraft came to rest on the right side of the runway, 380 ft from the threshold. There were no injuries to the two pilots or 10passengers. At the time of the occurrence, the runway visual range (RVR) was fluctuating between 1 800 ft and 2 800 ft in snow and blowing snow, with winds gusting to 40kt.

This picture taken shortly after the occurrence illustrates the poor visibility
This picture taken shortly after the occurrence illustrates the poor visibility

Findings as to causes and contributing factors

  1. A late full flap selection at 300 ft above ground level(AGL) likely destabilized the aircraft’s pitch attitude, descent rate, and speed in the critical final stage of the precision approach, resulting in an increased descent rate before reaching the runway threshold.
  2. After the approach lights were sighted at low altitude, both pilots discontinued monitoring instruments, including the glide slope indicator. A significant deviation below the optimum glide slope in low visibility went unnoticed by the crew until the aircraft descended into the approach lights.

Finding as to risk

  1. The crew rounded the decision height (DH) figure for the instrument landing system (ILS) approach downward, and did not apply a cold temperature correction factor. The combined error could have resulted in a descent of 74ft below the DH on an ILS approach to minimums, with a risk of undershoot

Other finding

  1. The cockpit voice recorder (CVR) was returned to service following an intelligibility test that indicated that the first officer’s hot boom microphone intercom channel did not record. Although the first officer’s voice was recorded by other means, a potential existed for loss of information, which was key to the investigation.

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