HISTORY OF ACCIDENT Use your browsers 'back' function to return to synopsisReturn to Query Page
On July 20, 2001, at 1603 central daylight time, a Eurocopter BK117-C1 twin-engine helicopter, N313LS, was substantially damaged when it impacted trees and terrain during an autorotation following a dual loss of engine power while in cruise flight near Decatur, Texas. The helicopter was registered to Debis Financial Services, Inc., of Norwalk, Connecticut, and was operated by Omniflight Helicopters, Inc., of Addison, Texas. The commercial pilot and flight nurse sustained serious injuries, and the flight paramedic received minor injuries. Visual meteorological conditions prevailed and a visual flight rules (VFR) company flight plan was filed for the 14 Code of Federal Regulations Part 91 positioning flight. The flight originated from Dallas, Texas, at 1535, and was destined for Wichita Falls, Texas.
The flight was en route to Wichita Falls to pick up a medical patient. According to the operator, the pilot reported that shortly after flying past Decatur, Texas, the helicopter experienced a loss of engine power on the #2 (right) engine. The pilot stated that he secured the engine and started to divert to the Decatur Municipal Airport. During the diversion, the #1 (left) engine lost power and the pilot attempted to autorotate the helicopter to a field. The helicopter impacted trees adjacent to the field and came to rest on its right side.
A witness, who worked for the U.S. Forest Service and was driving near the accident site, observed the helicopter pass over his automobile. He then observed the helicopter "make a 180-degree turn to the east. There was no smoke and [he] assumed that the aircraft had landed in a field." Shortly after the helicopter disappeared from his view, the witness received a radio call concerning an aircraft accident. Approximately 30 minutes after observing the helicopter, the witness found the accident site; however, no one was there. The operator reported that they had airlifted the pilot and crew out of the accident site prior to the local authorities' arrival.
Review of the operator's dispatch audio tape revealed that the flight had departed Dallas at 1535:33, and the pilot reported having 2 hours and 20 minutes of fuel on board and an estimated time en route of 1 hour and 20 minutes. Between 1552:06 and 1553:09, the dispatcher attempted to obtain a position report from the pilot to no avail. At 1553:25, the pilot gave a position report. At 1555:46, the dispatcher provided a patient update to the pilot and medical crew. At 1603:35, a radio squelch was heard over the tape; however, no voice transmission was recorded. Between 1609:09 and 1610:07, the dispatcher attempted to obtain a position report from the pilot; however, she was unsuccessful. At 1610:42, the dispatcher received a cellular phone call from the flight's paramedic stating that they had been involved in an accident and they were requesting medical assistance. The paramedic reported that the pilot had made a mayday call; however, the dispatcher never heard it.
During an interview conducted by an NTSB investigator, the flight paramedic reported that on the morning of the accident, he arrived at work at 0545. He and the flight nurse performed their preflight checks. Both the paramedic and nurse reported that they had not seen whether or not the pilot conducted a preflight inspection of the helicopter. The medical crew received a call around 1530, notifying them of a patient who was to be picked up in Wichita Falls. The paramedic and flight nurse then conducted a "walk around" prior to departing, and the paramedic performed the fire guard duties for the engine start. The paramedic reported that the pilot started the right engine first. Neither the paramedic nor the nurse noticed whether the pilot was utilizing the checklist during the engine start procedures.
The paramedic was sitting in the front left seat during the flight. He reported that while they were en route, he noticed that the torque indicators were at 40% and 70%. He asked the pilot if that was alright and the pilot then matched the torque indicators. When the flight passed Decatur, at an altitude of 2,000 feet, the audio warning sounded, which the pilot then cleared. The paramedic added that the audio warning sounded again and he noticed a master caution warning light and 3 annunciator lights. He stated that the lights were dim and he could not read them.
The pilot announced to the paramedic that they were flying single-engine and were diverting to Decatur. The pilot requested that the paramedic confirm that they had lost power on the #2 engine, which he did. Subsequently, the pilot secured the #2 engine and asked the paramedic for the emergency procedure checklist; however, the paramedic "interrupted him." The paramedic reported that they were in a turn and descending when he noticed the left engine torque gauge "drop to zero from about 70%." The aircraft was in a "high rate of descent over trees about 100-150 feet agl heading for a clearing," and the pilot made a mayday call. The paramedic added that he did not notice the fuel quantity, did not hear or smell anything unusual, and approximately 40-50 seconds had elapsed between the two loss of power events.
The pilot stated to the NTSB investigator-in-charge (IIC) that he did not see any warning lights immediately prior to, or during the loss of engine power events.
The pilot held a commercial helicopter certificate with an instrument helicopter rating. On May 25, 2001, the pilot was issued a second class medical certificate with a limitation to "possess corrective glasses for near vision." According to company flight records, the pilot underwent initial BK-117 training with Omniflight Helicopters on July 31, 1999, and underwent his last recurrent ground and flight training in the BK-117 on February 19, 2001. According to the Pilot/Operator Aircraft Accident Report, the pilot had accumulated 6,411.8 total hours of rotorcraft flight time, of which 292.8 hours were in the BK-117. Review of the company's airman flight and duty time record revealed that the pilot worked from 0630 to 1900, on the both the 18th and 19th of July. On the morning of the accident, the pilot started his work shift at 0630.
The accident helicopter was configured for the transport of medical patients with two seats in the cockpit, two rear-facing seats aft of the cockpit, one medical bed, and a bench. The helicopter was powered by two Turbomeca ARRIEL 1E2 turboshaft engines. The helicopter's fuel system utilizes four bladder type fuel cells: a forward main tank, an aft main tank, and two center supply tanks. The aft main fuel tank supplies fuel to the forward main fuel tank via a gravity feed system. The fuel is then routed to the left and right fuel supply tanks via two transfer pumps (forward and aft) located in the forward main fuel tank. The left supply tank provides fuel for the left engine, and the right supply tank provides fuel for the right engine. The fuel system has a usable fuel capacity of 1,230.39 pounds (181 gallons) of jet fuel, and a total unusable fuel quantity of 7.7 pounds (1.1 gallons) in the main fuel tanks and 10.143 pounds (1.49 gallons) in the supply fuel tanks. The fuel quantity indicator displays the fuel quantity in the forward main fuel tank and the two supply fuel tanks. Additionally, there is a fuel low sensor installed in each supply tank, which illuminates a FUEL LOW I and/or II caution light on the annunciator panel if the fuel in a supply tank becomes lower than 49.39 pounds (7.26 gallons).
In part, the helicopter's flight manual calls for the following steps during the pre-start checklist:
FUEL PUMP TRANSFER switches - ON (F PUMP XFER caution light off)
FUEL PUMP TRANSFER switches - OFF (F PUMP XFER caution light on)
PRIME PUMPS caution light - Check function in turn:
FUEL PUMP PRIME I (II) switches - ON- check PRIME PUMPS caution lights comes on
FUEL PUMP PRIME I (II) switches - OFF
Both FUEL PUMP PRIME switches - ON- check FUEL PRESS lights off...
FUEL QUANTITY indicator - Check quantity...
ANNUNCIATOR PANEL TEST switch - Push to test annunciator panel lights...
After the engines are started, the flight manual dictates that the pilot turn the fuel transfer pump switches to the on position (which will extinguish the forward and aft F PUMP XFER caution lights), turn off the primer pump switches, and check the annunciator panel to ensure that the PRIME PUMPS caution light is extinguished. The pre-takeoff checklist calls for the pilot to recheck the fuel quantity gauge and to check that all caution and warning lights are off. The takeoff checklist again calls for the pilot to check that all caution and warning lights are off.
The Omniflight Helicopter's Normal Procedures checklist states that "all preflight checklist tasks will be accomplished prior to the first flight of each shift. Items marked with a '*' will be accomplished prior to subsequent flights." Prior to conducting the preflight walk around inspection, the checklist calls for the pilot to check the operation of "all interior lights" and to then turn them off. The interior and pre-start checklist requires that the pilot turn on the prime pumps I & II and check that the fuel pressure caution lights turn off. Then the pilot is to check that the transfer pumps work. In addition, the pilot is to set the instrument lights "as required," and test the annunciator panel for operation. The Omniflight engine start checklist also requires that the pilot make sure that the primer pumps are in the ON position and check that the fuel pressure caution lights are extinguished. Then the pilot is supposed to test the annunciator panel again. After both engines are started, the pilot is to turn both transfer pumps on (both F PUMP XFER lights should then be extinguished indicating that they are operating), and turn off both primer pumps. During the before takeoff check, the pilot is to check that all warning and caution lights are off.
The helicopter flight manual indicates that the pilot and console (PILOT&CSL) variable resistor controls the lighting of the pilot's flight instruments and the console lighting. If the variable resistor is actuated, warning lights on the annunciator panel and master warning light (MASTER) are simultaneously reduced in brightness (for night operations). According to the operator, the helicopter flew the night before the accident, and the accident flight was the first flight of the day.
Review of company maintenance records revealed that on July 8, 2001, the #1 engine (serial number 18025) and its fuel control unit (FCU) had been removed and replaced with a serviceable engine (serial number 18002) and FCU after a pilot reported a discrepancy, noting that the #1 engine would not start. At the time the #1 engine was replaced, the helicopter had accumulated 2,793.2 total flight hours. At the time of the replacement, the #1 engine (serial number 18002) had accumulated a total of 3,740.0 hours, and the #2 engine (serial number 18026) had accumulated a total of 2,428.6 hours. No uncorrected discrepancies were noted in the aircraft flight log, which was dated from June 19, 2001, to the day of the accident. At the time of the accident, the helicopter had accumulated 2,804.3 hours of total flight time.
The FAA inspector, who responded to the accident site, reported finding the helicopter on its right side, on top of broken tree limbs, with fuel spilling from the bottom side of the helicopter. The right side of the helicopter was structurally damaged, the main rotor blades were damaged, and the right horizontal stabilizer was bent up. Review of photographs taken by the FAA inspector and a representative from the helicopter manufacturer revealed that the transfer pumps were found in the ON position, and the primer pumps were found in the OFF position. The pilot and console variable resistor control was found in the on/full bright position. Fuel samples from the helicopter were collected for further examination.
It was noted that the switch on the emergency locator transmitter (ELT) was found in the OFF position; however, its remote activation switch was found in the arm position. The helicopter was transported to Air Salvage of Dallas, Lancaster, Texas, for further examination.
TESTS AND RESEARCH
On July 24, 2001, the NTSB investigator-in-charge (IIC), FAA inspector, and representatives from Omniflight, American Eurocopter, and Turbomeca examined the helicopter. The engine cowlings were opened and the fuel supply lines to the engine bay were disconnected. No fuel was noted in the left and right engine fuel supply lines. The helicopter's electrical system was turned on and it was noted that the fuel quantity indicator displayed 4, 0, and 15 gallons of fuel in the #1 supply, #2 supply, and forward main fuel tanks, respectively. The NTSB IIC found the PILOT&CSL variable resistor control in the ON position and noted that the master caution and annunciator panel lights were not visible (examination took place outside during daylight hours). The NTSB IIC then turned off the PILOT&CSL variable resistor control and noted that the master caution and annunciator panel lights were visible. The transfer pumps were operated by their respective switches in the cockpit, and it was noted that fuel began to flow into the supply tanks. It was also noted that the transfer pumps' respective F PUMP XFER annunciator lights extinguished when the pumps were turned on.
On August 8, 2001, fuel samples from the truck that last fueled the helicopter and fuel samples from the helicopter were tested. The fuel test results were "normal."
On September 4, 2001, the #1 and #2 ARRIEL 1E2 engines were removed and taken to Turbomeca's manufacturing facility in Grand Prairie, Texas, for further examination. On September 5, 2001, the NTSB IIC, FAA Inspector, and representatives from Omniflight, American Eurocopter, and Turbomeca examined both engines. The main inlet fuel filters were removed from both engines, and approximately 100 mL of fuel was collected from each filter bowl and FCU inlet lines. Some debris was noted in each filter bowl; however, the filter elements were relatively clear. The FCU inlet filters were removed from each engine and a nominal amount of debris was noted in each filter element. The filter elements were reinstalled on their respective engines and the chip detectors were then removed and examined. A nominal amount of ferrous metal was noted on the chip detectors. The engines were then taken to the test cell and each engine was run for 40 minutes at 94% N1. The engines were then run at 100% and 85%. It was noted that the bleed valve operation and governor check revealed no anomalies. No anomalies were noted in either engine that would have prevented their operation.
Air traffic control radar data depicted the helicopter flying from 1540:25 to 1602:34.
The accident helicopter and its engines were released to the owner's representative on October 3, 2001.