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N20SP accident description

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Tail numberN20SP
Accident dateFebruary 22, 1995
Aircraft typeEurocopter AS-350-B
LocationCambridge, MA
Additional details: None

NTSB description

HISTORY OF FLIGHT

On February 22, 1995, about 0937 eastern standard time, a Eurocopter, AS-350-B, helicopter, N20SP, operated by the Massachusetts State Police (MSP), was destroyed when it collided with a boat house during a forced landing near Cambridge, Massachusetts. The two pilots and two passengers were fatally injured. Visual meteorological conditions prevailed, and no flight plan had been filed for the passenger flight conducted under 14 CFR Part 91.

The pilots, Troopers James Mattaliano and Paul Perry, worked from 1500 until 2300, on February 21, 1995. The pilots reported to work the morning of February 22, 1995, about 0700. Their mission that morning was to pick-up two AT&T employees at the Nashua Street Heliport, and transport them to the MSP Headquarters in Framingham, Massachusetts. Trooper Mattaliano was the senior pilot; therefore, he was considered the pilot-in-command.

The MSP rented hangar space from Wiggins Airways, at the Norwood Memorial Airport (OWD), in Norwood, Massachusetts. The hangar was shared with another helicopter operator. At 0750, the pilot/manager of this operator reported that he observed Trooper Perry enter the hanger, and walk around N20SP. He saw Trooper Perry approach the right side of N20SP where the tail joins the main fuselage, touch the helicopter, and then walk aft and visually inspect the tail rotor area. Trooper Perry then opened the hangar doors and moved N20SP outside, where the two troopers boarded N20SP and started the engine. He estimated that the run-up lasted about 10 minutes, and the helicopter departed to the northeast.

According to OWD Air Traffic Control Tower (ATCT) records, N20SP departed OWD, about 0922. Using the call sign of State Police One, N20SP contacted Boston ATCT, at 0924, and requested clearance into the Boston Class B airspace to land at the Nashua Street Heliport. The helicopter was cleared into the airspace and, at 0930, the pilot of N20SP reported landing assured at the heliport. At 0936:16, N20SP contacted Boston ATCT and requested clearance out of the Class B airspace, at 800 feet.

The Boston ATCT granted the request, and the pilot of N20SP stated "thanks," at 0936:29. That was the last transmission received from N20SP.

Boston ATCT Radar plotted N20SP reaching an altitude of 600 feet mean sea level, at 0937:00, before beginning a decent below radar coverage.

Over 20 witness statements were taken from personnel who observed the helicopter after it departed from the Nashua Heliport. The witnesses observed the helicopter flying westbound over the Charles River. A puff of smoke was seen coming from the helicopter in the vicinity of the engine. The helicopter then turned to the right and descended toward the north bank of the river. The witnesses estimated the angle of descent was between 45 and 70 degrees. Most of the witnesses observed smoke trail from the engine exhaust area. Eleven witnesses stated that the main rotor blades were turning slowly, or not at all.

The helicopter struck two metal structures extending from the Harvard Sailing Pavilion and came to rest on the roof.

The accident occurred during the hours of daylight approximately 42 degrees, 22 minutes north latitude, and 71 degrees, 00 minutes west longitude.

PILOT INFORMATION

Trooper James Mattaliano held a Commercial Pilot Certificate with a rating for rotorcraft helicopter, and a Private Pilot Certificate with a rating for airplane single engine land. He was not instrument rated.

His most recent Federal Aviation Administration (FAA) Second Class Medical Certificate was issued on April 6, 1994.

Trooper Mattaliano's total flight time was estimated at 1,150 hours, of which approximately 900 hours were in this make and model.

Trooper Paul Perry held a Private Pilot Certificate with ratings for airplane single engine land, and rotorcraft helicopter. He was not instrument rated.

His most recent Federal Aviation Administration (FAA) Second Class Medical Certificate was issued on January 4, 1995.

Trooper Perry's total flight time was estimated to be about 340 hours, of which approximately 180 hours were in this make and model.

The Safety Board made several requests for Trooper Mattaliano's and Trooper Perry's pilot logbooks. They were not provided to the Safety Board.

Additionally, the Safety Board made requests to the Massachusetts State Police to obtain copies of the remaining Air Wing pilot's log books, to review flight hours and training. The requested information was not provided.

WRECKAGE INFORMATION

An NTSB Investigator examined the helicopter wreckage on February 22, 1995, at the accident scene, and on February 23 and 24, 1995, after the wreckage was moved to a facility in Boston, Massachusetts.

The examination revealed that all major components of the helicopter were accounted for at the scene. The helicopter main fuselage came to rest on a boat house roof, on an approximate magnetic bearing of 360 degrees. The tail boom was separated from the fuselage and submerged in water next to the boat house.

The main fuselage and cabin were destroyed. The pilot's instrument and caption panel were intact. Examination revealed that caption chips for the generator, bleed air valve, and engine oil pressure contained broken or deformed light bulb filaments.

The yellow and blue star arms of the main rotor head were fractured on the leading edge. The fractures continued aft and inboard, at a 45 degree angle, and the star arms were bent opposite the direction of rotation. The red star arm was not fractured.

The pitch change rods, and the main rotor collective and cyclic servos remained connected. Except for the fore and aft cyclic servo, the servo piston rods moved freely and pumped fluid. The fore and aft servo was damaged from impact with the main transmission. The main transmission support rods were separated, and the transmission was shifted forward.

The three main rotor blades (MRB) were attached to their respective star arms of the main rotor head. The three MRBs displayed black marks on the bottom of each blade tip. The roof area under the MRBs was covered with black tar.

The yellow and red blades were intact, and displayed chord wise scratches on the lower leading edges. The red blade also displayed chord wise scratches on the lower skin surface. The blue blade was broken about 3 feet from the root, and the tip cap was peeled upward. Trailing edge debonding was observed on the red and blue blades.

The tail boom was bent in the vicinity of the number two bearing support. The right side tail boom mount was torn, and the left side was separated along the rivet line. The tail rotor drive shaft was uncoupled at the point of separation from the fuselage.

The tail rotor gear box, hub, and blades where intact. These components remained attached to the tail boom and were not damaged. When the tail rotor drive shaft was rotated, the gear box output shaft turned the tail rotor.

Flight control continuity was verified from the mixing unit to the servo controls.

Rotation of the main rotor mast confirmed drive train continuity from the transmission to the engine, and to the tail rotor drive shaft. The free-wheeling capability of the transmission was also confirmed.

Examination of the transmission revealed lubrication through out the transmission, and the gears rotated freely. A bore scope inspection of the upper and lower chip detector areas revealed no internal damaged. The upper and lower chip detectors were absent of debris.

The fuel tank was ruptured and destroyed. The airframe fuel filter was intact and a fuel sample was taken from the filter for further examination.

The power turbine and the freewheel section of the engine rotated freely. The compressor section would not rotate. Examination of the engine chip detector revealed that it was absent of debris. The engine was removed for further examination.

MEDICAL AND PATHOLOGICAL INFORMATION

Autopsies were performed on Troopers James Mattaliano and Paul Perry, on February 23, 1995, by Dr. Richard Evans of the Chief Medical Examiners Office, Cambridge, Massachusetts.

The toxicological testing report, from the FAA toxicology Accident Research Laboratory, Oklahoma City, Oklahoma, was negative for drugs and alcohol for Troopers Mattaliano and Perry.

TESTS AND RESEARCH

Engine Examination

On March 13 and 14, 1995, the engine was examined at the Turbomeca facility, Grand Prairie, Texas, under the supervision of a Safety Board Investigator. Parties to the investigation were also present during the examination.

The examination revealed that the P2 air fitting, which supplied pressurization to the rear bearings, was not secured and was safety-wired backwards.

The axial compressor would not rotate while attached to the gas generator. After Module Two and Three were separated, the axial compressor rotated freely. A rub mark was observed on the compressor cover, and on the turbine nozzle envelope, at the second stage turbine blade path. A build-up of a reddish-brown substance was observed on the fuel injection manifold, labyrinth ring and labyrinth envelope assembly. It was determined that this reddish-brown substance was preventing the axial compressor from rotating. Samples of the substance were removed for further examination.

The fuel control unit (FCU) was placed on a test stand. The FCU filter was replaced, due to the visible debris on the original filter. The FCU was run through all parameters with no discrepancies. The fuel injection manifold (wheel) was placed on a test bench and flow checked. Five of the six manifold ports were clogged, and produced a zero fuel flow. The 6th port delivered 16 liters per hour (LPH) of fuel. Specifications required the 6 ports to deliver 230 to 260 LPH.

During the disassembly, fuel samples were obtained from the engine inlet hose and the fuel control unit. These samples were sent to the Atomus Laboratory, Arlington, Texas, for analysis.

Fuel and Filter Testing

The fuel control unit and several filters were removed from the helicopter for testing. This included the Michigan Filter, which was designed to capture ice particles, and eliminate the requirement for anti-ice additives in the fuel system. Also, fuel samples were taken from the MSP Framingham fuel tank and the Wiggins fuel truck for laboratory analysis.

Samples from the helicopter fuel system were analyzed by the Atomus Laboratory. This analysis revealed that the Michigan Filter contained a two phase fuel sample. The upper portion of the sample was a clear, light colored fuel. The lower sample was a dark heavy substance. The lighter sample contained 90 parts per million of water, and the dark brown sample contained 84 percent water. The laboratory report stated:

...when placed on a microscope slide, it [the dark brown heavy sample] dries to a white/gray solid, with red to red brown inclusions. The deposit contains an iron compound, most probably iron oxide from corrosion of iron in the fuel or the handling system.

The Michigan Filter element also contained white/gray deposits.

Additionally, the report stated:

...Water is present, but evaporates into a heavy brown, brittle, but transparent film. The physical appearance of this film is identical, even to the inclusions of the red to red brown material recovered from the lower phase of the sample..."

The report also stated that an infrared analysis of the fuel deposit film indicated that the material had properties consistent with polyamide polymers.

The red to red brown inclusions were also observed in the airframe fuel filter, the fuel control unit (FCU), FCU filter, and FCU inlet hose.

The analysis of the fuel samples for water revealed the following:

SOURCE WATER IN FUEL PARTS PER MILLION (PPM)

Michigan Fuel Filter..................90.0 FCU Filter............................30.5 Airframe Filter-Fuel Control..........25.4 FCU Inlet Hose #1.....................55.7 FCU Inlet #2................less than 35.0 FCU B040B...................less than 35.0

MSP Framingham Fuel Tank Testing

Fuel samples from the MSP Framingham fuel tank were analyzed by the Atomus Laboratory, and Saybolt Inc., Boston, Massachusetts.

Atomus Laboratory testing reveled that fuel samples from the bottom of the tank contained water and a collection of hydrous iron oxide and rust. No polymer particles were observed in the samples from the tank or the tank pump. The report stated, "The heavy phase, containing the iron oxide is water, 100%."

The analysis of the fuel samples for water revealed the following:

TEST FACILITY SOURCE WATER IN FUEL PPM

Atomus Laboratory.....Tank bottom................... 510.0 Atomus Laboratory.....Tank Pump.......................57.0 Saybolt Inc...........Tank Pump....................7,800.0

According to the Eurocopter Standard Practices Manual, Chapter 20.07.03, page 2, the maximum allowable concentration of water in fuel was 10 ppm. The United States Army Field Manual 10-68, also stated that 10 ppm of water in jet fuel was the maximum acceptable.

Jet Fuel Thermal Oxydation Tests (JFTOT) were conducted by Saybolt Inc., of fuel samples from the MSP Framingham tank, and the Wiggins Airways Jet Fuel truck, that refueled N20SP. The maximum fuel pressure drop allowed for the test was 25 mm/Hg, for a test duration of 150 minutes, at 260 degrees Celsius.

The fuel sample from the Wiggins Airways truck tested with a zero pressure drop. After 30 minutes of testing, the MSP tank sample experienced a pressure drop greater than 25.0 mm. The JFTOT machine shut down at 62.8 minutes into the test of the MSP fuel.

Two samples from the Michigan Filter were sent to the NTSB Materials Laboratory for examination. The Metallurgist's Factual Report stated that both samples were submitted to ARTECH Corporation for analysis.

The ARTECH Corporation report stated:

...The spectrum from the acetone dry film lacks the absorption at 3200 cm which is characteristic of oxygen-hydrogen bonds, indicating that this part of the sample may be due to waters of hydration rather than a bound part of the compound. The remainder of the spectra are characteristic of the cellulose derivative, cellulose acetate. Cellulose acetate is used as a blending compound in thermoplastics. Cellulose pentaacetate is soluble in alcohol. It is thus possible that a thermoplastic was in contact with the fuel in this incident and dissolved due to an alcohol additive in the fuel...

ADDITIONAL INFORMATION

Air Wing Organization

* NOTE: In order to protect the anonymity of the law enforcement officers still performing police functions, names will be substituted with capitol letters.

The Massachusetts State Police (MSP) Air Wing was a "Public Use" organization. The helicopters and airplane assigned to the Air Wing were of civil certification and registry.

The MSP Air Wing had existed for over 20 years. The investigation revealed that the only written document relating to the operation of the Air Wing, was MSP General Order TOP-06. The purpose of the three page General Order (GO) was to establish guidelines for the utilization of MSP Aviation. The GO described the type of missions the Air Wing would support, and how flights were requested. The only specific direction provided to the Air Wing personnel was paragraph 4.1.3, that stated, "There will be a pilot and co-pilot for all night and instrument rated flights."

The last section of the GO referred to Unit Qualification and Training. This section dealt with the selection process for assignment to the Air Wing, and listed the types of associated training that could be involved. Paragraph 4.3.6 stated, "Air Wing officers are req

(c) 2009-2011 Lee C. Baker. For informational purposes only.