North Star DC3T at Fort Hope on Jun 21st 2019, both engines lost power after departure
Last Update: August 31, 2020 / 21:53:01 GMT/Zulu time
Incident Facts
Date of incident
Jun 21, 2019
Classification
Report
Airline
North Star Air
Departure
Fort Hope, Canada
Destination
Picke Lake, Canada
Aircraft Registration
C-FKGL
Aircraft Type
BASLER BT-67 Turbo 67
ICAO Type Designator
DC3T
On Aug 31st 2020 Canada's TSB released their final report concluding the probable cause of the accident was:
Findings as to causes and contributing factors
These are conditions, acts or safety deficiencies that were found to have caused or contributed to this occurrence.
1. After lifting the landing gear control handle, with his left hand on or near the throttle quadrant, the pilot not flying may have inadvertently moved the fuel condition levers, cutting the fuel to both engines simultaneously.
Findings as to risk
These are conditions, unsafe acts or safety deficiencies that were found not to be a factor in this occurrence but could have adverse consequences in future occurrences.
1. If the propeller automatic feathering system is not armed, there is a risk that, in the event of an engine failure, the aircraft would not be able to maintain the required climb gradient and obstacle clearance would not be guaranteed.
2. If operators do not follow manufacturers’ directions to amend procedures, operators will use incorrect operating procedures, increasing the risk of compromising safety margins.
3. If pilots do not use available shoulder harnesses, there is an increased risk of injury in the event of an accident.
Other findings
These items could enhance safety, resolve an issue of controversy, or provide a data point for future safety studies.
1. Due to insufficient altitude and time available to the crew, none of the 3 engine relight options were available to the flight crew before the aircraft collided with the water surface.
The TSB summarized the sequence of events:
Before departing CYFH on the occurrence flight, the crew conducted the before-takeoff checklist, which requires the propeller automatic feathering system to be armed for takeoff; however, the crew did not arm this system.
At approximately 0140, the aircraft departed CYFH with the first officer acting as the pilot flying (PF), seated in the right seat, and the captain acting as the pilot not flying (PNF), seated in the left seat. Shortly after takeoff, the PF called for the landing gear to be retracted. The PNF then selected the gear up at approximately 200 feet above ground level (AGL). Both engines subsequently lost power simultaneously, and the flight crew executed a forced landing on Eabamet Lake, Ontario, in total darkness.
The aircraft fuselage remained intact and immediately began to fill with water. The flight crew retrieved the survival kit, evacuated the aircraft via the main cabin door, and swam to shore.
Once on shore, the flight crew started a fire to warm up. The fire was noticed by a patrolling officer of the Nishnawbe Aski Police Service, who responded and transported the flight crew to the nursing station at the Eabametoong First Nation Band Office for a medical assessment. Neither flight crew member was injured.
The aircraft sustained substantial damage, but there was no post-impact fire. The aircraft remained floating in the water.
No emergency locator transmitter (ELT) signal was received by the Joint Rescue Coordination Centre in Trenton, Ontario, at the time of the accident. However, the ELT did activate approximately 4 hours after the accident. The investigation did not determine why the ELT activation was delayed.
The TSB analysed:
The investigation determined that there were no signs of an airframe, engine, or system failure during the occurrence flight.
The simultaneous engine shutdown led investigators to consider inadvertent engine control inputs as a possible cause. The analysis will therefore focus on the acoustic signatures from the occurrence flight and the 4 previous flights, the location of the landing gear handles, and the operator’s procedures for updating checklists.
The analysis will also examine the possibility of engine relights, the design and ergonomics of the throttle quadrant, and the use of the propeller automatic feathering system.
...
The cockpit voice recorder (CVR) recorded the 4 flights before the occurrence flight. The sound of a rapid reduction in propeller speeds shortly after takeoff was heard only on the occurrence flight. Propeller speed was reduced at the same time and at the same rate on both engines. A power loss on 2 engines can occur; however, the shutdown is usually staggered in sequence, with 1 engine reducing power before the 2nd engine. Clicks were heard immediately before the reduction in propeller speed, which likely indicated that the fuel condition levers made contact with the control pedestal as they were moved toward the down position (STOP).
The analysis of the acoustic signatures found that the timing of the clicks heard during the normal engine shutdowns corresponded to an immediate reduction in propeller speed. This phenomenon was also observed in a video of a shutdown filmed on another DC3-TP67 operated by North Star Air Ltd. (North Star Air).
During the uneventful departures, the acoustic signatures did not include clicks between when the gear was commanded UP and when the 400-foot call was completed.
On the occurrence flight, acoustic signatures related to the movement of gear handles and the activation of the hydraulic system indicate the gear was selected UP. However, the gear operation was interrupted approximately 1 second after it began due to a loss of hydraulic pressure. This interruption coincided with 2 clicks and a rapid reduction in propeller speed.
The rapid reduction in propeller speeds and the sound of the 2 clicks suggest that the fuel condition levers were likely accidentally moved, cutting the fuel to both engines simultaneously. However, the investigation could not find an acoustic signature to indicate conclusively whether the levers had been returned to the RUN position. There were no power or propeller lever adjustments made before the reduction in engine power.
The location of the landing gear controls on the DC3-TP67 can present ergonomic challenges for some pilots.
In the occurrence aircraft type, the pilot raising the landing gear needs to bend over and/or rotate sideways to reach the mechanical safety latch control and landing gear control handles, and then must lift the landing gear control handle with one hand. Because there is no dedicated position or handle for pilots to place the opposite hand to steady themselves if necessary, such as during the initial climb out, there is an increased likelihood that the pilot will place that hand on the throttle quadrant and will move a control by accident.
...
The acoustic signature analysis indicated the simultaneous loss of power to both engines, suggesting that the fuel condition levers were accidentally moved to the STOP position shortly after the gear selection.
During the climb out, both of the pilot flying’s (PF’s) hands were likely on the yoke, in accordance with standard operating procedures (SOPs). The pilot not flying (PNF) had his right hand on the landing gear control handle, and his left hand and arm may have rotated toward the throttle quadrant. After the PNF raised the landing gear control handle with his right hand, he may have accidentally moved the fuel condition levers while rotating back into position and steadying or bracing himself with his left hand. Therefore, after lifting the landing gear control handle, with his left hand on or near the throttle quadrant, the PNF may have inadvertently moved the fuel condition levers, cutting the fuel to both engines simultaneously.
The design of the levers in the throttle quadrant of the occurrence aircraft is consistent with ergonomic guidelines to prevent accidental movement: the design provides tactile and visual cues, movement resistance, and dual-axis motion, which are safeguards against accidental movement. However, the fuel condition levers are still usable in the case of an emergency when an engine shutdown is necessary.
...
Relighting an engine that has flamed out in flight, due to a momentary disruption of airflow or fuel to the engine, should be automatic when the ignition system switches are in the CONT position. If the ignition system switches are not set to CONT, as was the case in the occurrence flight, the flight crew are required to complete an in-flight engine relighting procedure.
In-flight engine relighting procedures are approved emergency procedures published in the North Star Air SOPs. These procedures (propeller windmilling and starter assisted) require flight crews to follow a checklist.
In the propeller windmilling procedure, a minimum airspeed of 160 knots is required to successfully relight an engine in flight. The SOPs state that the initial climb after takeoff and up to 400 feet above ground level should be conducted at an airspeed of V2 (approximately 90 knots), which is lower than the 160 knots required for the propeller windmilling procedure. The crew would have needed to increase airspeed by descending, but the aircraft had insufficient altitude to attain the required airspeed at the time of the engine power loss. Therefore, the starter-assisted relight procedure was the only option available to restore engine power at this altitude and airspeed.
The SOPs indicate that, when following the starter-assisted relight procedure, the engine should normally relight within 10 seconds from when the fuel condition lever is moved to the RUN position, and that the relighting would be evident from a rise in gas generator speed (Ng). Only 17 seconds elapsed from the time the engines lost power until impact. Therefore, the flight crew did not have enough time to attempt this engine relight procedure before the aircraft collided with the water surface.
Aircraft Registration Data
Aircraft registration data reproduced and distributed with the permission of the Government of Canada.
Incident Facts
Date of incident
Jun 21, 2019
Classification
Report
Airline
North Star Air
Departure
Fort Hope, Canada
Destination
Picke Lake, Canada
Aircraft Registration
C-FKGL
Aircraft Type
BASLER BT-67 Turbo 67
ICAO Type Designator
DC3T
This article is published under license from Avherald.com. © of text by Avherald.com.
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