The Transportation Safety Board of Canada (TSB) has released an investigation report on the CL-415 water-scooping air tanker that was involved in an accident on Moosehead Lake in Newfoundland and Labrador July 3, 2013, which we first covered HERE. Fortunately the two pilots were not injured and climbed out of the partially submerged aircraft, used a cell phone to call their headquarters, and waited on the wing for 30 minutes until they were rescued.
The previous day the flight crew had completed 53 water-drop flights at a fire northeast of Wabush, Newfoundland and Labrador, with each flight taking about 3 minutes. The accident occurred on the first flight of the next day while they were working on a wildfire, scooping water from Moosehead Lake in Newfoundland and Labrador.
The scooping system on their CL-415 had a feature that when activated by an Auto/Manual switch would automatically retract the water-scooping probes that while skimming the surface of a lake inject water into the tank. The system, when on Auto, allows a predetermined amount of water into the tank. The water drop control panel computer uses the aircraft’s zero-fuel weight and the weight of the onboard fuel and chemical foam to calculate the maximum amount of water that can be scooped without exceeding the aircraft’s maximum take-off weight of 47,000 pounds.
The Auto/Manual switch was in the Manual position on the first flight that day and the probes did not retract while scooping, resulting in a 3,000-pound overweight condition. The probes being down for an extended period of time combined with the too-heavy aircraft meant that it was on the lake surface for a much longer distance than on the previous days flights, 3,490 feet versus 1,200 feet after touchdown. As land approached, the pilot turned the aircraft to use more of the lake surface. The initiation of the left turn resulted in the left float contacting the water while the hull became airborne. This created a downward force on the left float, which acted as a pivot point around which the aircraft rotated, causing the hull to impact the water.
The forward force of 1.1 g was not sufficient to activate the emergency locator transmitter which requires 2.0 g, and it was not manually activated by the flight crew. One of the pilots was able to escape with a life vest, but the other vest floated away out of reach. Neither could gain access to the life raft located in the rear of the fuselage. The pilot contacted company personnel by cellular telephone and advised them of the situation. Within about 30 minutes, Department of Natural Resources employees arrived by boat and transported the flight crew to shore.
The aircraft floated partially submerged for at least four days, eventually settling on the lake bottom about 225 feet from the southern shore of the lake. There was substantial damage to the aircraft. The report described it as “destroyed”.
On August 14, 2014 another water-scooping air tanker was involved in an accident in Canada. A single-engine Air Tractor 802 Fireboss crashed and and sank while scooping water on Chantslar Lake in British Columbia, Canada about 30 kilometers west of Puntzi Mountain.
Below are some excerpts from the report on last year’s CL-415 accident:
Because the PROBES AUTO/MANUAL switch locks in the MANUAL position, an inadvertent movement of the switch from the MANUAL selection would be unlikely. However, the switch can be easily moved from the AUTO to MANUAL selection by simply pulling the centre pedestal cover rearward during removal.
At the end of the previous day, the aircraft was shut down and the switch was left in the AUTO position. The centre pedestal cover was installed and remained there until the following day, when it was removed by the Pilot Flying (PF). Neither of the pilots purposely repositioned the switch during the occurrence flight. Therefore, it is likely that the PROBES AUTO/MANUAL switch was inadvertently moved from the AUTO to MANUAL position when the centre pedestal cover was removed.
An inadvertent movement from the AUTO to the MANUAL selection can lead to the aircraft being in an overweight situation if the flight crew does not monitor the water quantity. When a flight crew is operating with the switch in the AUTO selection, there is an expectation that the probes will always automatically retract at the predetermined water quantity, as was the case on the 53 flights of the previous day. When the flight crew expects the system to work properly, it is likely that less priority is given to the importance of monitoring the water quantity.
The aircraft flight manual (AFM) instructs flight crews to monitor the water quantity even when the PROBES AUTO/MANUAL switch is in the AUTO selection. At the time of the occurrence, the flight crew was occupied during the scooping run with other flight activities, and did not notice that the water quantity exceeded the predetermined limit until after the tanks had filled to capacity. This situation resulted in the aircraft being over the maximum take-off weight.
2.7 Firefighting training
Aerial firefighting is a specialized operation that not only requires the flight crew to be competent in their aircraft operation skills but also to be familiar with the specialized techniques associated with using the aircraft to fight fires. This familiarity allows crews to better adapt to difficult flying situations under intense workload. The Newfoundland and Labrador Government Air Services (NGAS) did not provide any specific ground training syllabus for aerial firefighting.
Thanks and a hat tip go out to Chris.