WEST PALM BEACH, FL, USA
N370WM
Aerospatiale AS 350B
The day before the accident, spot painting was performed to the upper corners of the windshield, and the mechanic failed to remove the roll of masking material from the canopy. During the preflight without using a checklist, the pilot did not notice the roll of masking material. Weight and balance calculations were not performed by the pilot, and postaccident calculations revealed that the helicopter was 76 pounds over gross weight at takeoff. During the initial climb, a portion of the roll of masking material fell from the helicopter, and about 13 feet wrapped around the main rotor mast. Additionally, about 5 feet was partially sucked over and into the engine inlet. The engine experienced a partial loss of power while climbing about 150 feet agl, with a resulting decrease in main rotor rpm. The low rotor warning was heard by the passengers followed by a hard landing. Postcrash the engine was placed in a test cell and found to operate normally. The checklist does not specifically mention to check the oil cooler inlet area or forward of that area during preflight.
HISTORY OF FLIGHT On April 8, 1997, about 0844 eastern daylight time, an Aerospatiale AS 350B, N370WM, registered to and operated by the South Florida Water Management District, crashed during takeoff from the Palm Beach International Airport, West Palm Beach, Florida. Visual meteorological conditions prevailed at the time and no flight plan was filed for the public-use flight. The helicopter was substantially damaged and the commercial-rated pilot and four passengers were seriously injured. The flight was originating at the time of the occurrence. About 0630, on the morning of the accident, a pilot reported that he landed his helicopter on the ramp about 25 feet from near where the accident helicopter was parked. He lifted off about 5 minutes later and during that time, he observed an object fluttering on top of the cabin in about the middle. He thought the object was paper towels that appeared to be dew soaked. He continued the takeoff and did not report his observation until after the accident had occurred. The pilot stated that he performed a preflight of the helicopter which was positioned on a dolly on the ramp without using a checklist. He stated that he verified the fuel load of 70 percent was on board, and in part verified that the engine intake area was free of obstructions. He also stated that while standing on the ground at the arc of the main rotor blades, he looked toward the oil cooler inlet area which is located on the top portion of cabin forward of the main rotor assembly. He did not observe any foreign objects and he did not clean the windshield that morning. He briefed the passengers about the use of seatbelts and door locations then boarded the helicopter. He did not perform weight and balance calculations. He further reported starting the engine without the use of a checklist and after the engine was started, the passengers reported hearing a horn and seeing a "door" light illuminated on the instrument panel. The pilot then exited the helicopter twice to examine the doors and after reentry into the helicopter, the horn and door light extinguished. Shortly after lifting from the dolly, he nodded to another South Florida Water Management pilot who was on the ramp near his helicopter. The pilot further stated that he does not recall the airspeed or altitude during the climb nor does he recall the engine malfunction or what procedures he performed following the engine malfunction. The passengers reported that no horn was heard during the initial liftoff but when at 100-150 feet, the horn sounded again which continued until impact with the ground. During the climb out, a South Florida Water Management District pilot who was on the ramp near where the helicopter departed observed a foreign object fall from the right side of the helicopter and land on a taxiway. He retrieved the object which was a 12-inch wide, partial roll of plastic material with red lettering indicating 3M Hand-Masker Film 48 inch. He then diverted his attention and did not witness the accident. According to a witness who is an FAA certificated airframe and powerplant mechanic and was in a hangar adjacent to the crash site, he first heard a loud bang that he associated with a compressor stall. At that time the helicopter was flying in a slight nose high attitude past his position about 75 feet above ground level. He then began running toward the area and did not witness the accident. Another witness who was flying in another helicopter near the accident site reported seeing the helicopter flying eastbound and observed the helicopter flare about 100 feet or less, then observed the helicopter turn toward the north. The helicopter then rolled to the left with a slight flare before a hard impact with the ground first with the left side. The main rotor blades then contacted the ground and the helicopter then cartwheeled one time. A small grass fire aft of the engine exhaust was noted and the engine was still running when the first rescuers arrived on scene. The engine was shut down by spraying fire extinguisher agent into the engine inlet. The wreckage was partially moved to facilitate the rescue of the pilot. PERSONNEL INFORMATION Information pertaining to the pilot is contained on page 3 of the Factual-Report Aviation. Additionally, review of records revealed he last attended recurrent flight training in the accident make and model on December 11, 1996. During the training flight which lasted 1.3 hours the pilot performed in part five straight in autorotations and six 180-degree autorotations. AIRCRAFT INFORMATION Information pertaining to the helicopter is contained on page 2 of the Factual Report-Aviation. The helicopter was signed off as being assembled in accordance with applicable manufacturer's instructions on September 23, 1991. The basis for certification of the helicopter were FAR 21.29, and FAR 27, effective February 1, 1965, including amendments 27-1 through 27-10 plus FAA special conditions No. 27-79-EU-23, dated August 23, 1977. Review of FAR 27.1413, as of January 1, 1977, revealed the strength of the restraints and their anchorage locations must not be less than the ultimate load as specified in FAR 27.561 (b) which is in part 4.0 Gs downward and 4.0 Gs forward. Review of the aircraft log book revealed that there was no entry to indicate that the right rear seat restraint had been replaced. Review of the flight manual indicates that the bleed valve annunciator light located in the annunciator panel is designed to illuminate when the Ng is below 93 percent. The total fuel capacity is 143 gallons of which .33 gallon is unusable, and the usable fuel on board at the time of takeoff as documented by the pilot was 99.77 gallons. The empty weight and gross weight of the helicopter are 2,832.58 and 4,300 pounds respectively. By design, the horn activates when either the hydraulic pressured drops below 30 bar, when the main rotor rpm drops below 360 rpm, or in normal flight when testing the caption panel. The flight manual indicates that the main rotor speed during stabilized power-on flight is 385 +1/-5 rpm and during autorotation the minimum and maximum main rotor rpm is 320 and 424. The day before the accident an FAA certificated mechanic removed and replaced the front windshields with a one-piece unit in accordance with a Supplemental Type Certificate. The mechanic stated that after the installation he repaired cracks in the canopy at the upper windshield corners. He masked the front windshields and the canopy area aft of the area where he repaired using about 7-8 feet of 3M Hand-Masker Film from a roll he obtained from a cabinet inside the hangar. He then painted the repaired areas and removed the masker film from the windshields and aft of the repaired areas. He reported placing the unused roll of masker film back in the supply cabinet. The helicopter was signed off as being airworthy for return to service by the same mechanic and no other quality control inspections were performed to the helicopter by other maintenance personnel. The Hand-Masker Film used by him for masking was similar to that found by the witness who observed an object fall from the helicopter during the initial climb. Review of the flight manual found in the wreckage revealed current revisions from the manufacturer were not posted. The current flight manual indicates that three inspections for daily helicopter operation are required. These inspections include the check before the first flight of the day (BFF), the check in conjunction with flight, and the check after the last flight of the day (ALF). None of these checks specifically state to check the area near and forward of the oil cooler inlet for obstructions. METEOROLOGICAL INFORMATION Visual meteorological conditions prevailed at the time. Further meteorological information may be obtained on page 4 of the Factual Report-Aviation. COMMUNICATIONS Review of a recording of the voice tape from the West Palm Beach Control Tower revealed in part the pilot of another helicopter flying near the accident flight advised the pilot "just off your nose." The accident pilot responded "roger" and about 2 seconds later, a sound similar to a horn was recorded on the tape. No legible voice transmission was associated with hearing the horn on the frequency. About 5 seconds after the horn sound was recorded, a pilot advised the tower of the accident. No horn was heard when the pilot responded "roger" to the pilot of the other helicopter. Additionally, the pilot did not declare an emergency with the controller. WRECKAGE AND IMPACT Examination of the crash site revealed the helicopter crashed onto grass on the airport property with evidence of tail rotor skid impact first with the ground separating the vertical fins and tail cone aft of the tail rotor gearbox. The flight path was 085 degrees. Tail rotor blade contact with the ground was then noted followed by evidence of contact with the ground by the left skid. The right skid then contacted the ground followed by the bottom of the fuselage. The helicopter came to rest on a heading of 225 degrees 84 feet from the first point of impact. The crash site was located about 2,489 feet from the point of takeoff. The helicopter was observed resting on its right side with the blue marked main rotor blade which was still attached, displaced downward and resting against the tail boom. The right side of the tail boom in that area exhibited two indentations. The yellow marked main rotor blade which was also still attached did not exhibit evidence of coning or downward displacement. The red marked main rotor blade was failed outboard from the blade grip with no evidence of coning. The separated red blade was found within the immediate vicinity of the wreckage. The tail boom, tail rotor, and tail rotor gearbox were still attached and examination of the flight controls revealed no evidence of preimpact failure or malfunction. The collective flight control servo was observed to be in the full "up" position and the cyclic flight control servo was in the "aft" and to the "right position. Both skids were failed and longitudinal members under the cabin floor were observed to be damaged. Examination of the engine intake area revealed a 5-foot section of white plastic with red lettering indicating 3M Hand-Masker Film 48 inch, material partially drawn through the intake screen in several locations. Grease/dirt transfer from the intake screen was noted on the plastic. The plastic type material (about 13 feet) was also observed wrapped loosely around the main rotor mast to include the swash plate assembly. The plastic was also wrapped and tightly twisted around the red and yellow main rotor blades retaining pins safety pins. Postcrash examination of the cockpit revealed the pilot's and left front seats were separated from the airframe and the seats were damaged near the attach points. Additionally, the right rear seat outboard lower portion of the seat was observed to be deformed down and the male portion of the lapbelt was observed to be failed where it enters the female portion of the buckle. The seat belt was retained for metallurgical examination. (See the Tests and Research section). Examination of the engine revealed no evidence of fuel contamination and fuel leakage was noted postcrash; about 20 gallons of fuel were drained from the fuel tank. Examination of the air inlet horn and the air box revealed both were compressed in. No hydraulic fluid was observed in the transmission compartment area and plastic was not noted on any sharp or protruding objects in the transmission deck area. The hydraulic drive belt was observed to be in place and was not cut or failed and the hydraulic fluid reservoir was determined to be adequately serviced. The hydraulic pump and annunciator panel were removed for further tests. (See the Tests and Research section of this report). The engine was removed from the helicopter and sent to the manufacturers facility where it was placed in a test cell and found to operate normally. An engine run report is an attachment to this report. MEDICAL AND PATHOLOGICAL Toxicological testing of specimens of the pilot was performed by the FAA Toxicology and Accident Research Laboratory. The results were positive for lidocaine, and diazepam. The results were negative for ethanol. Carbon monoxide and cyanide testing was not performed due to a lack of a suitable specimen. According to the Palm Beach County EMS Report, the pilot was given lidocaine, valium, and anectine. Review of the Physicians' Desk Reference (PDR) revealed that each ml of Valium injectable contains 5 mg diazepam. TESTS AND RESEARCH Bench testing of the hydraulic pump at normal operating rpm revealed no evidence of preimpact failure or malfunction. Examination of the hydraulic bulbs in the annunciator panel using a 15-power stereo microscope revealed no gross deformation of the bulbs filaments. Examination of the bleed valve bulbs revealed slight deformation of one of the bulbs filaments. None of the other bulbs examined revealed evidence of gross deformation of the bulb filaments. Metallurgical examination of the failed lapbelt revealed that the insertion tongue was failed with no evidence of preexisting fracture areas. Material hardness of the insertion tongue was determined to be 89HRB. Static linear pull testing of the unused rear seat lapbelt assembly was performed to failure which revealed that the insertion tongue failed at the similar location as the accident lapbelt. The failure occurred at 1,821 pounds. According to the lapbelt manufacturer, the alloy of the buckle is similar to the U.S. 7075 standard which has a typical tensile strength of 83 KSI. 1KSA is equal to 6.9MPa. The designed tensile strength of the buckle is greater than or equal to 492 MPa. Calculations to convert KSI to MPa were performed which revealed the MPa of the buckle was 573 MPa. ADDITIONAL INFORMATION Postaccident weight and balance calculations were performed using the current empty weight of the helicopter (2,832.58 lb.), the previously mentioned usable fuel quantity of 99.77 gallons (668.459 lb.), and the self reported weights of the pilot and passengers. The pilot and passenger weights were 210 lb., 185 lb., 155 lb. with 5 lb. of baggage, 148 lb., and finally 172 lb. The calculations revealed that the helicopter was 76 pounds over the maximum gross weight at the time of the takeoff excluding the fuel used for engine start and the climb segment. According to the chief pilot of the operator, the accepted procedure when determining the fuel load vs. gross weight and number of passengers expected was to use a standard weight of 170 and 120 lb. for male and female passengers respectively. A preprinted chart was available to the pilots which determined the fuel load in percentage based on the number of passengers expected. Using that formula and the known amount of usable fuel on board, the current empty weight of the helicopter, and the number of male/female occupants, the calculations revealed that the helicopter would be 4 pounds under the maximum gross weight using that formula. According to the operator's operations manual, the pilot-in-command shall make certain that the aircraft does not exceed the maximum allowable gross takeoff weight considering runway, wind, temperature, and elevation. Review of the airplane flight manual revealed that the procedure to takeoff indicates to lift off to a hover about 5 feet then for transition from hover, "increase speed without increasing the power demand (power required for hover [In Ground Effect] I.G.E.) and without climbing until [Indicated Air Speed] I.A.S. is 65 kt." Review of the Speed Versus Height Envelope chart also found in the airplane flight manual revealed that at the passengers estimate of the height attained during the climb (100-150 feet), the minimum speed to avoid the shaded area at 100 feet is 60 knots. At 150 feet, the minimum speed to avoid the shaded area is 55 knots. The wreckage
Failure of the pilot-in-command to recognize that the main rotor rpm was decreasing and his failure to maintain the main rotor rpm during the autorotative landing resulting in a hard landing. Contributing to the accident was the partial loss of engine power due to partial blockage of the engine air inlet screen. Also contributing was inadequate inspection of the airplane following maintenance by other maintenance personnel for their failure to remove a paint masking roll from the canopy. Additionally, inadequate preflight of the helicopter by the pilot for his failure to observe the roll of paint masking material and weight and balance exceeded.
Source: NTSB Aviation Accident Database
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