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 A06W0041-Airframe Failure and Collision with Terrain

On March 21, 2006, the pilot of a McDonnell Douglas Helicopters Inc.(MDHI) MD600N helicopter was conducting heli-slinging operations 25NM northwest of ZamaLake,Alta.(CFT9). The pilot had picked up the fifth and final bag of seismic equipment and was returning to the staging area, approximately 3NM from the pick-up site. While en route, the tail boom separated from the fuselage and the helicopter crashed into a clearing about 1600ft from the pick-up site. The sling load was still attached to the aircraft on a
115-ft longline. The tail boom was found about 240ft from the main wreckage. The accident occurred at approximately 14:00Mountain Standard Time(MST). The pilot, the sole occupant, sustained fatal injuries. There was no post-impact fire.

Findings as to causes and contributing factors

  1. The attach fitting at the upper right attachment point of the tail boom failed in fatigue. The transfer of loads to the adjacent aft ring structure resulted in the cascading failure of the remaining three tail boom attach fittings and separation of the tail boom from the fuselage.
  2. Aircraft control was lost following separation of the tail boom. Safe recovery following this type of structural failure was unlikely.
  3. The 25-hr visual inspections allowed by the alternate method of compliance (AMOC) did not identify damage to the tail boom attachment fittings before structural failure.

Safety action taken
The operator voluntarily grounded its fleet of MD600N helicopters pending the replacement of the attachment fittings as per Part 2 of Service Bulletin SB600N-043.

On April 13, 2006, MDHI issued SB600N-043 requiring a borescope inspection of all four attach fittings. Within 25hr of receipt of the bulletin, the attach fittings were to be replaced. On April 13, 2006, MDHI issued Technical Bulletin TB600N-007R1 regarding modification of the fuselage aft section and tail boom to strengthen the tail boom attach fittings and upper longerons.

On April 27, 2006, the Federal Aviation Administration(FAA) issued Airworthiness Directive(AD) AD2006-08-12. This AD required that additional inspection holes be created in the aft fuselage skin panels, and that the upper and lower tail boom attach fittings, the upper longerons, and angle and nut plates for cracks be inspected. It also required, within a specified time, replacing the aluminum upper right tail boom attach fitting with steel fittings, painting the inspection area, and replacing existing nut plates.



TSB Final Report A06C0062-Loss of Control on Go-Around (Rejected Landing)

On May 14, 2006, a Convair580A was conducting stop-and-go landings on Runway36 at the airport in La Ronge,Sask. On short final approach for the third landing, the aircraft developed a high sink rate, nearly striking the ground short of the runway. As the crew applied power to arrest the descent, the autofeather system feathered the left propeller and shut down the left engine. On touchdown, the aircraft bounced, the landing was rejected, and a go-around was attempted, but the aircraft did not attain the airspeed required to climb or maintain directional control. The aircraft subsequently entered a descending left-hand turn and crashed into a wooded area approximately one mile northwest of the airport. The first officer was killed and two other crew members sustained serious injuries. The aircraft sustained substantial damage. The accident occurred during daylight hours, at 12:45 Central Standard Time(CST).

Findings as to causes and contributing factors

  1. The flight crew attempted a low-energy go-around after briefly touching down on the runway. The aircraft's low-energy state contributed to its inability to accelerate to the airspeed required to accomplish a successful go-around procedure.
  2. The rapid power lever advancement caused an inadvertent shutdown of the left engine, which exacerbated the aircraft's low-energy status and contributed to the eventual loss of control.
  3. The inadvertent activation of the autofeather system contributed to the crew's loss of situational awareness, which adversely influenced the decision to go around at a time when it may have been possible for the aircraft to safely stop and remain on the runway.
  4. The shortage and ambiguity of information available on rejected landings contributed to confusion between the pilots, which resulted in a delayed retraction of the flaps. This departure from procedure prevented the aircraft from accelerating adequately.
  5. Retarding the power levers after the first officer had exceeded maximum power setting resulted in an inadequate power setting on the right engine and contributed to a breakdown of crew coordination. This prevented the crew from effectively identifying and responding to the emergencies they encountered.

Findings as to risk

  1. The design of the autofeather system is such that, when armed, the risk of an inadvertent engine shutdown is increased.
  2. Rapid power movement may increase the risk of inadvertent activation of the negative torque sensing system during critical flight regimes.

Other findings

  1. There were inconsistencies between sections of the Conair aircraft operating manual(AOM), the standard operating procedures(SOPs), and the copied AOM that the operator possessed. These inconsistencies likely created confusion between the training captain and the operator's pilots.
  2. The operator's CV-580A checklists do not contain a specified section for circuit training. The lack of such checklist information likely increased pilot workload.

Safety action taken
On October 30, 2006, the TSB sent a Safety Information Letter (A060037-1) addressing autofeather risks to Transport Canada.

Conair revised its procedures with respect to engine power management to achieve and maintain a stabilized approach.

The operator hired experienced training personnel and is in the process of developing operating procedures specific to their operation.



TSB Final Report A06W0106-Dynamic Rollover

On July 4, 2006, the pilot of a Bell 206B helicopter was conducting water-bucketing operations in support of forest-fire suppression activities approximately 23NM northeast of Wabasca, Alta. At approximately 16:00Mountain Daylight Time(MDT), the helicopter contacted trees adjacent to a shoreline, broke up, and came to rest in an inverted position. The pilot, the sole occupant, was fatally injured.

Findings as to causes and contributing factors

  1. The pilot undertook a water-bucketing mission for which he did not have the required training and experience.
  2. The pilot engaged in flight operations with pronounced allergy symptoms, which probably contributed to reducing his ability to perform complex multi-task missions.
  3. It is probable that the pilot took a quantity of an allergy medication that could have affected his ability to stay alert and be aware of all surrounding mission factors.
  4. The operator had no system in place to ensure that flight crews did not undertake missions or use equipment for which they were not trained.

Safety action taken
The operator put in place several internal and external audit processes to ensure that pilot training meets all requirements on an ongoing basis. The operator developed a competency card listing all aircraft types and other operations that the individual has been trained on and authorized to perform.



TSB Final Report A06Q0181-Flight in Weather Conditions Unfavourable for Visual Flight, and Collision with Terrain

On October 19, 2006, a Cessna U206F floatplane was carrying out a local tourist flight in the area of Grand-Mère,Que. The pilot and the five passengers took off from the floatplane base at Tortue Lake,Que., at 10:20Eastern Daylight Time(EDT) in the direction of Piles Lake,Que. After flying over the Grand-Mère hydroelectric dam, the aircraft entered a valley leading to Piles Lake. The weather conditions worsened, and the floatplane entered a fog bank skirting the hills. The pilot lost all visual reference with the ground and tried to keep the aircraft's wings horizontal while applying full power to initiate a climb. The left float struck a tree, and the aircraft pitched downward and ended up on its back. The pilot and passengers evacuated the aircraft uninjured. The aircraft sustained major damage.

Other factual information
On the morning of the accident, two flights had been cancelled because of adverse weather conditions. At about 09:30EDT, the conditions improved and the chief pilot authorized the flight. The ceiling was estimated at 1100ft above ground level(AGL), and visibility was estimated at six miles. A specification on the operator certificate allowed for VFR flights during the day with visibility of at least one mile when the aircraft was flown at less than 1000ft AGL in uncontrolled airspace.

The tourists reported to the dock and waited for their flight, which had already been included on the day's agenda. Departure took place at 10:20EDT. The pilot established the aircraft at roughly 700ft AGL, that is, roughly 1100ft above sea level (ASL). Visibility was about six miles. However, the weather conditions deteriorated as the flight continued. When the aircraft entered the valley leading to Piles Lake, located about eight miles northwest of Tortue Lake, the pilot communicated by radio with the chief pilot, who was following in another aircraft, and warned him of the presence of fog. He alerted the chief pilot that he was going to do a 180º turn. The aircraft suddenly flew into a thick layer of fog, and the pilot lost visual reference with the ground required for VFR flight. He noticed the trees below the aircraft and applied full power to initiate a climb. At that moment, the left float clipped the top of a tree and the aircraft pitched downward. The aircraft nosed over and flipped onto its back.

Analysis
Since two of the earlier flights had been cancelled because of the weather, it is likely that the pilot was under no pressure from the chief pilot to go ahead with the flight. In consideration of the weather conditions just before departure and the specification on the operator certificate that allowed flying with visibility of at least one mile, the decision to go ahead with the flight can be justified. Yet, although the weather conditions were favourable for visual flight at the time of departure from Tortue Lake, they quickly deteriorated during the approach to Piles Lake. This loss of visibility was consistent with the graphic area forecast (GFA), which had warned that conditions might deteriorate to the point where visibility was reduced to ½ mile with a ceiling at 300ft AGL.

Flying at low altitude in low-visibility conditions is dangerous. Low-altitude flying gives pilots little time to see obstacles and take evasive action. The pilot's decision to turn back was late in coming. The consequence of his failure to act was the loss of visual ground references, and the pilot was unable to avoid striking the mountain right in front of him. Although the pilot did possess the necessary licence and qualifications, it is possible that his lack of experience contributed to his late decision.

Findings as to causes and contributing factors

  1. The pilot delayed turning back when he encountered adverse weather conditions, which resulted in a loss of visual ground references.
  2. On losing his visual ground references, the pilot was unable to avoid striking the mountain right in front of him. The aircraft hit some trees before nosing over and ending up on its back.


TSB Final Report A07C0151-Hard Landing-Fuel Leak and Fire

On August 11, 2007, a FireFly 12B hot air balloon was attempting to land in a field adjacent to Birds Hill Provincial Park near the northern outskirts of Winnipeg,Man. The balloon was operated under a special flight operations certificate issued by Transport Canada. One pilot and 11 passengers were on board, all in the balloon's basket. The flight was a local sightseeing flight originating in the southeast of Winnipeg and terminating in the northeast of Winnipeg.

The flight had been extended beyond Winnipeg as the pilot searched for a suitable landing area in strong winds. The balloon touched down and skipped several times. The basket was dragged on its side for about 700ft, and tipped over far enough for the burners to strike the ground as the balloon came to a stop. A propane fuel leak occurred and an intense uncontrolled fire ensued as the passengers were beginning to exit from under the partially-inverted basket. All occupants escaped; however, the pilot and two passengers suffered serious injuries in the intense fire. Four other passengers suffered minor injuries, some with burns. Two of the propane tanks and a fire extinguisher canister exploded, and the basket of the balloon was destroyed by fire. The accident occurred at about 09:08Central Daylight Time (CDT).

Findings as to causes and contributing factors

  1. The flight continued even though the winds exceeded the maximum demonstrated winds listed in the balloon flight manual, and were at the upper wind limit specified in the company operations manual.
  2. The fuel system was not shut down as recommended in the balloon flight manual procedures for a hard landing, even though a hard landing was likely.
  3. Because the balloon was not deflated quickly, the basket was dragged for some 700ft and the integrity of the burner support structure was lost.
  4. As the basket was dragged across the ground, the fuel-line fittings were pulled out at the burner manifolds and liquid propane was released in the vicinity of the pilot lights, resulting in the fire and subsequent explosion.

Findings as to risk

  1. There was no mandated requirement for passenger restraint or personal protective equipment to reduce injury during a dragged landing.
  2. Balloon air carrier operations do not have the same degree of regulatory oversight as other air carriers. There may not be an equivalent level of safety for balloon air carriers comparable to that of commercial operators.
  3. Exemplar fuel supply hoses manufactured by Sundance Balloons International, one of which was used to connect the inflator tank, did not meet the required airworthiness standard.
  4. The company operations manual maximum wind speed of 15kt was more than twice the wind speed demonstrated in certification testing. This was too high to ensure a short drag distance while deflating the envelope after landing.

Safety action taken
On March 27, 2008, the TSB released two recommendations to Transport Canada as follows:

While some commercial balloon operators in Canada have fare-paying passenger loads equal to those of commuter and air taxi operators, their passengers are not assured of the same level of safety and oversight by regulations and standards. The Board is concerned that, without adequate standards and regulations for balloon operators, balloon passenger safety will be compromised. Therefore, the Board recommends that:

The Department of Transport ensure that passenger-carrying commercial balloon operations provide a level of safety equivalent to that established for other aircraft of equal passenger-carrying capacity. (TSBA08-01)

Transport Canada Response to A08-01
To address the subject of the level of equivalent safety of passenger-carrying commercial balloon operations, Transport Canada is conducting a risk assessment of commercial passenger-carrying balloon operations. This study will address the special flight operations certificate process and commercial passenger-carrying balloon operation oversight. Once the review is complete, should regulatory changes be required, Notices of Proposed Amendment(NPA) will be developed and submitted to the Canadian Aviation Regulation Advisory Council(CARAC) for consultation.

While some commercial balloon operators in Canada have fare-paying passenger loads in the range of those of commuter and air taxi operators, their passengers are not assured of the same level of safety and oversight by regulations and standards. The inability to quickly shut off the fuel supply during landing or in an emergency increases the risk of a fire and/or explosion, compromising balloon passenger safety. Therefore, the Board recommends that:

The Department of Transport ensure that balloons carrying fare-paying passengers have an emergency fuel shut-off. (TSBA08-02)

Transport Canada Response to A08-02
To address the subject of the proposed emergency fuel shut-off for balloons carrying fare-paying passengers, Transport Canada is conducting a risk assessment to determine whether regulatory or non-regulatory solutions would be appropriate to address this issue. Once the review is complete, should regulatory changes be required, NPAs will be developed and submitted to CARAC for consultation.



TSB Final Report A07P0345-Loss of Control-Collision with Terrain

On October 13, 2007, a Cessna 172M floatplane was on a VFR flight from Bamfield,B.C., to Lake Cowichan,B.C., with two pilots and one passenger on board. The aircraft took off from the water aerodrome at Bamfield, completed a climbing turn to the right, and proceeded north along the Trevor Channel at the south end of the Alberni Inlet. An emergency locator transmitter(ELT) signal was later received from an aircraft in the area and the operator reported the aircraft overdue at about 15:50Pacific Daylight Time(PDT). A search and rescue effort was commenced and the wreckage was located approximately 15NM northeast of Bamfield. The accident occurred at about 15:00PDT. The three occupants suffered fatal injuries. There was no fire.

Other factual information
The accident site was at the bottom of a small valley about 3NM from Sarita Lake. There were very few trees damaged at the site. The trees very close to the accident site, almost straight above and adjacent to the wreckage, had some damage. The area was examined from a helicopter and no other trees showed damage consistent with an aircraft strike.

Figure 1: Likely track of aircraft from Sarita Lake

Figure 1: Likely track of aircraft from Sarita Lake

The valley bottom rises gradually between Sarita Lake and the accident site. The accident site is in a smaller valley branching off the Sarita Creek valley, approximately 670ft above Sarita Lake. This valley rises about 150ft from the Sarita Creek valley to the accident site (0.5NM) and a further 300ft in 0.5NM beyond the site. The peak elevation of this valley is about 0.75NM past the accident site. Beyond this point, the terrain drops into another valley. There is an elevation increase of 1100ft in the 4NM between Sarita Lake and the high point in the valley.

Illusions in flight
In some situations, pilots can be subjected to visual illusions when approaching rising terrain. As an aircraft approaches rising terrain, pilots tend to maintain a constant visual angle between the extended cowl of the aircraft and the crest of the terrain ahead. This tendency can result in a gradual increase in aircraft pitch attitude and a concurrent decrease in the aircraft's airspeed as the aircraft approaches the elevated terrain (see Figure2). This often results in a delay to the pilot's realization of inadequate aircraft climb performance ("a" in Figure 2), the aircraft's separation with the terrain decreases and the aircraft gets closer to aerodynamic stall as the angle of attack increases.

Figure 2: Aircraft performance and terrain profile (angles exaggerated for clarity)

Figure 2: Aircraft performance and terrain profile (angles exaggerated for clarity)

Analysis
The wreckage examination revealed no evidence of mechanical control problems. All control surfaces were attached and the physical damage signatures indicated that the aircraft's engine was operating with high power at impact. The weather was not a factor for the proposed flight, so the TSB analysis focused on the operation of the aircraft and human performance.

The attitude of the aircraft at impact is consistent with a stall and spin entry. Because the speed had not increased beyond stall (the slap mark made by the airspeed indicator's pointer at impact was at 40kt) and there was no damage to the trees around the aircraft at the accident site, it is concluded that the aircraft stalled close to the tree tops. That height was not sufficient to recover from stall before impact with terrain. Also, because the aircraft was found pointed downhill and opposite to the expected route of flight, it is likely that the stall occurred when the pilot was reversing course while flying up the valley at low level. The pilot, or pilots, were applying a right roll aileron control, normally the action to recover from a left roll, but not effective during a stall or spin recovery. In the stall, control was lost.

It could not be determined why the aircraft was so close to terrain in the area of the accident. It is possible they were flying low to look at something on the ground. It is also possible they had made a practice landing and takeoff at Sarita Lake, but they should have been able to climb above terrain on their presumed route, unless optical illusions delayed their realization of the rising terrain and they were operating in a cruise configuration until the last moments of the flight.

When an aircraft stalls close to the ground and recovery is not affected, it impacts the terrain at close to right angles, thereby exposing the aircraft and its occupants to high deceleration forces. If control is maintained, that is to say, the wings are not stalled and the aircraft is flown into gradually rising terrain, the deceleration forces are likely to be spread over a longer time and are more survivable. Because most general aviation aircraft are not equipped with linear stall warning devices such as angle of attack indicators, pilots may not always be aware of how close they are to stalling the aircraft.

In this accident, the horn would not likely have sounded early enough to give either pilot time to take action to avoid the stall.

The non-flying pilot was trained in mountain flying techniques, but for unknown reasons, the aircraft was being flown close to terrain. It is possible that both pilots were lulled into a false sense of security due to visual illusions and the lack of a linear stall warning device. Also, the experience level of the flying pilot may have caused the pilot-in-command(PIC) to be less vigilant.

Finding as to causes and contributing factors

  1. The aircraft was operating close to terrain and was reversing course when it stalled and started a spin at an altitude from which there was insufficient height to recover before it collided with terrain.

Findings as to risk

  1. Pilots are not always aware of how close to a stall they are, as few general aviation aircraft are equipped with linear stall warning devices, such as angle of attack indicators.
  2. There are no regulatory standards for mountain flying training in Canada and pilots continue to delay their decisions to turn around until it is too late to safely doso.
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