NTSB Factual Report

HISTORY OF FLIGHT

On May 11, 2004, about 1410 Alaska daylight time, a high skid-equipped Aerospatiale AS-350B2 helicopter, N60618, sustained substantial damage when it ditched in the Taiya Inlet following a loss of engine power, about 6 miles south of Skagway, Alaska. The helicopter was being operated as a visual flight rules (VFR) sightseeing flight under Title 14, CFR Part 135, when the accident occurred. The helicopter was operated by Temsco Helicopters Inc., Skagway. The commercial certificated pilot, and the 4 passengers, were not injured. Visual meteorological conditions prevailed, and VFR company flight following procedures were in effect.

During a telephone conversation with the National Transportation Safety Board (NTSB) investigator-in-charge (IIC), on May 11, at 1540, the office manager for the operator reported the accident helicopter overdue, and indicated that a search was in-progress. The helicopter was one of two helicopters conducting an air tour flight in the area of the Meade Glacier. The helicopter and the occupants were located by a passing vessel in the Taiya Inlet about 1600.

During a telephone conversation with the NTSB IIC on May 12, the pilot reported that the accident helicopter was the second helicopter to depart from the Meade Glacier after his tour passengers walked on the glacier. The pilot said that he was northbound along the west side of the Taiya Inlet and was in a slow descent, returning to Skagway. About 2,200 feet msl, the pilot noticed that the engine oil pressure annunciator light illuminated, indicating low oil pressure. The helicopter did not yaw, or have any unusual vibrations. The pilot also noticed low engine torque, illumination of the low main rotor annunciator, and then the sounding of the low rotor warning horn. The pilot entered an autorotation, and selected an emergency landing area along the shore of the steep fjord-like terrain. During the autorotation, the pilot said he noticed the engine generator annunciator illuminate, and he pulled the manual activation handle to deploy the emergency floats, but the floats did not deploy. The pilot said he did not attempt to use the electrical emergency float deployment switch.

The pilot indicated that the only available emergency landing area was the water, next to a rocky shelf. He said he touched down on the water, next to the shelf, and when he pulled upward on the collective pitch to cushion the landing, no engine power was produced. After touchdown, the passengers jettisoned the helicopter doors on the left side, and exited into about waist-deep water. The pilot exited the helicopter and assisted the passengers onto the rocks. The helicopter remained upright for a short time, but then sank. About an hour after the emergency landing, the pilot and passengers were noticed by a passing vessel.

In a telephone conversation with the NTSB IIC on May 19, the pilot reported that the helicopter was fueled before his departure. He said that the fuel quantity was 50 to 55 percent at takeoff. When he departed the Meade glacier on the accident flight, he said the fuel quantity was 30 to 35 percent. The flight from the glacier to the operator's base at Skagway should have taken about 20 minutes.

The pilot reported that the operator records a total daily use of fuel for its fleet of helicopters. The operator does not maintain individual fuel records for each helicopter.

PERSONNEL INFORMATION

The pilot holds a commercial pilot certificate with a rotorcraft helicopter rating, and a flight instructor certificate with a helicopter rating.

In the Pilot/Operator Aircraft Accident Report (NTSB Form 6120.1) submitted by the pilot, he reported that his total aeronautical experience consisted of 1,159.2 hours, of which 16.9 hours were accrued in the accident helicopter make and model, all in the previous 30 days.

AIRCRAFT INFORMATION

The helicopter had accumulated a total time in service of 5,512.2 hours, 45.4 hours since an annual inspection on October 17, 2003. The engine had accrued a total time in service of 1,601.4 hours, 45.5 hours since the annual inspection.

The helicopter was equipped with emergency, pop-out type floats. The floats may be deployed electrically, or manually. Electrical deployment requires the pilot to remove his hand from the collective pitch control and push a button on the center consol to arm the emergency float system. The pilot would then activate a second switch to activate the emergency floats. Manual deployment requires the pilot to grasp a handle on the instrument panel, and pull the activation cable.

The helicopter's fuel tank is a large plastic tank that incorporates a fuel gauging system inside the tank. The operator had marked fuel quantity level lines on the exterior of the tank depicting fuel level, and percent of fuel at each line. The fuel tank incorporates a vent tube at the top of the tank to allow atmospheric air pressure to enter the tank.

The helicopter manufacturer reported that the fuel level transmitter probe was a Jaeuger, resistor type probe. The probe is mounted vertically in the tank, and is a metal tube with an internal float that travels in a spiral channel along the length of the tube. The fuel level is transmitted via wire to the fuel quantity gauge located on the helicopter instrument panel. The probe has a low fuel position that will illuminate a low fuel annunciator on the instrument panel when the fuel level falls below 60 liters, which the manufacturer indicated equates to about 18 minutes of engine operation.

The helicopter manufacturer reported that the Jaeuger probe was the original installation when the helicopter was delivered February 27, 1992. The manufacturer issued Service Letter 867-28-88 on March 31, 1988, which stated the resistive type fuel gauge was not a defect-free measurement system, and stressed that the pilot "must keep an eye on fuel indication to make sure reading is constant and to detect any possible failure."

On May 12, 1992, the manufacturer published Service Bulletin 28.12, which corresponded to modification AMS 350A07-2484 incorporated into production helicopters beginning February, 1992, onward. Retrofit action was available to operators. The modification was the installation of a capacitor fuel gauging system as a replacement for the resistor gauging system, "To increase reliability of fuel quantity measurement and to render the low level warning independent of this measurement. This modification presents particular interest for all operators required to work with low fuel levels (sling operations for example), by providing operators with perfect information redundancy." Revision 1 of the service bulletin, issued May 26, 1994, classified the service bulletin as "recommended" and specified the affected helicopter models AS 350B, B1, B2, BA, D, and L1.

An FAA inspector, Juneau Flight Standards District Office (FSDO), Juneau, Alaska, reported that his examination of the maintenance records for the accident helicopter did not indicate incorporation of AMS 350A07-2484.

The manufacturer published Service Letter 1190-28-93 on October 12, 1993, which addressed fuel gauge transmitters of all helicopters. The service letter stated, "We have received a number of reports from operators of incorrect operation of the fuel gauging system. We feel, therefore, that is advisable to remind flight crews that they must comply with the aircraft handling rules which cover fuel management. The piloting rules should lead the pilot to check the remaining flying time himself, taking into account factors such as the weight of the fuel load and duration of the current flight. If there is a doubt, the pilot's analysis take precedence over the indications read on instruments."

On July 20, 1994, the helicopter manufacturer published Service Letter 1215-28-94, which stated, in part: "We would like to remind you of the fuel gauging system functional checking procedure given in the Fight Manual, and that these directives must be followed each time the aircraft is refueled. AS350 - AS550: Check, on the fuel gauge, the quantity of fuel remaining in the tanks; Fill the tanks, monitoring the quantity of fuel delivered on the bowser flowmeter; Check that the difference in the aircraft fuel gauge readings corresponds to the quantity of fuel delivered, and determine the corresponding weight."

SURVIVAL ASPECTS

The area of the accident was along the edge of a fjord. Steep mountainous terrain terminates at the edge of the Taiya Inlet. The area of the accident had numerous rocks, but no flat beach area for an emergency landing spot.

The pilot and passengers were wearing personal flotation devices. These were an inflatable design, but none were activated or needed.

SEARCH AND RESCUE

Once the flight was declared overdue, company aircraft began looking for the helicopter. The occupants of the helicopter were spotted by a passing vessel on the Taiya Inlet.

TESTS AND RESEARCH

The helicopter was recovered from the Taiya Inlet on May 13. Prior to the recovery, it was inverted in about 30 feet of water. It was placed upright on its landing gear skids on a barge, and transported to Juneau, Alaska. An FAA inspector from the Juneau FSDO was present during the recovery. The inspector said he did not see a fuel sheen on the water at the accident site. After recovery, the fuel tank contained about 32 percent fluid. The fluid was sea water, except for about 1.5 quarts of fuel. Fuel was found in the airframe fuel filter, and in the fuel line from the filter to the engine fuel control.

The FAA inspector also examined the emergency float activation system. He reported that the manual activation cable rigging was out of tolerance. When the pilot pulled the manual activation handle, the cable mechanism did not travel far enough to activate the firing mechanism.

The fuel probe was removed under the direction of the FAA inspector on May 17. The inspector noted and marked the position of the float assembly within the probe tube. It was found at location that was about the low fuel position. The body of the probe had slight distortion along the vertical axis of the assembly, slight denting at the top of the probe, and a slight bend at the bottom of the probe at the electrical cannon plug assembly. The helicopter's fuel probe, fuel gauge, and the annunciator panel were sent to the NTSB's Materials Laboratory.

A functional test of the fuel probe was conducted on May 19, 2005, at the manufacturer's facility. The test was overseen by an NTSB Senior Air Safety Investigator The functional test was not completed due to the damage received during the accident, corrosion, and an electrical short in the probe's circuitry.

The engine was sent to the engine manufacturer. It was examined on June 17, 2004, during a disassembly that was overseen by an FAA inspector from the FAA's Rotorcraft Directorate, Fort Worth, Texas. The FAA reported that the examination revealed no evidence of preimpact abnormality. The FAA indicated that a significant amount of water was drained from the engine. Manual rotation of the engine via the compressor and turbine section was not possible. No rotational scoring was found on the compressor, impeller, or turbine sections. No evidence of foreign object damage (FOD) was found in the engine. The chip detectors were free of metal debris, although they were covered in mud/sludge.

The fuel control unit, previously removed by the FAA inspector in Juneau, was operationally tested and was found to be within prescribed limits.

ADDITIONAL INFORMATION

The Safety Board retained the engine for examination until its release to the owner's representatives on June 22, 2004. The fuel probe, fuel gauge, and annunciator panel were released on June 2, 2005.

NTSB Probable Cause

A loss of engine power during cruise flight for an undetermined reason, which resulted in a ditching and submersion of the helicopter when the emergency float system did not deploy. Factors contributing to the accident were improper rigging of the mechanical activation mechanism for the emergency floats by company maintenance personnel, and the failure of the pilot to utilize the electrical firing system to activate the emergency floats.