WATERTOWN, WI, USA
N626SF
Bell OH-58C
The Milwaukee County Sheriff's Aviation Department was operating as a public-use operator. The helicopter was on a cross-country flight when it impacted rolling terrain in a sparsely populated area. Witness described fog in the area at the time of the accident. The Milwaukee County Sheriff's Aviation Division's standard operating procedures (SOP's) states under section 3/033.05 Basic VFR Weather Minimums, that 'Basic VFR weather minimums shall conform to those minimums outlined in FAR 91.155 and 91.157.' In addition to these requirements, the night weather minimums for operations outside the local flying area were a ceiling of 1,000 feet and a visibility of 3 miles. The chief pilot reported and also made an entry into the helicopter's discrepancy log indicating that the attitude indicator was inoperative on May 19, 2000. There was no entry regarding corrective action for the attitude indicator. On June 4, 2000 a draft of an MEL, prepared by the chief pilot, stated that the attitude indicator is, 'Not required during daylight. Not required at night when in VMC [visual metrological conditions] conditions'. FAA-H-8083-21, Rotorcraft Flying Handbook, Chapter 12, Attitude Instrument Flying, states under Attitude Indicator: 'The attitude indicator provides a substitute for the natural horizon. It is the only instrument that provides an immediate and direct indication of the helicopter's pitch and bank attitude...'
HISTORY OF FLIGHT On August 17, 2000, at 2141 central daylight time, a Bell OH-58C, N626SF, operated by the Milwaukee County Sheriff's Department, was destroyed on impact with terrain. Instrument meteorological conditions prevailed at the time of the accident. The 14 CFR Part 91 public use flight was not operating on a flight plan. The commercial pilot and observer sustained fatal injuries. The flight departed from Baraboo, Wisconsin en route to Wauwatosa, Wisconsin, at approximately 2115. A witness reported the following: "I could hear a helicopter close by and me and my friend ... were watching it the entire time. I saw it all of a sudden not flying smoothly and start nose diving down at a very fast speed. We heard a boom. The others didn't believe me and so we went out to look for it. We got 2 miles and didn't see any flames..." The witness also stated that weather conditions were foggy. A witness statement taken by the Dodge Country Sheriff stated the following: "...It sounded extremely close and low. He went outside and he could hear the helicopter very clearly. He told me that they have numerous military helicopters that fly over his residence and this one sounded like it was beating air and going nowhere. He told me that he never actually saw the helicopter, but he saw that it was using a powerful like landing light. I asked him if it could possibly have been a search light, and he said it could have been. He said the light was so bright it lit up the entire hillside. he was pointing to the hillside that was directly east of his residence, which would have been approximately a half mile to three-quarters of a mile west of the actual crash site. I asked [the witness] what the weather conditions were like and he said it was dead calm but extremely foggy and the air was very heavy with water. [The witness] added that it was more of a ground fog than it was a real thick fog." A second witness statement taken by the Dodge County Sheriff stated the following: "...[the witness] indicated that the helicopter was flying extremely low and that it appeared the engine seemed to be running very noisily. ...He had no estimate on how high the helicopter was or how fast it was going. [The witness] indicated that it seemed to be on a steady speed throughout the whole incident. The helicopter was flying out of the east. [The witness] indicated that the helicopter was traveling approximately southwest. When the helicopter got in the general area of the woods, the helicopter tipped to the left and the tail section went down. [The witness] stated that at this point the helicopter started to turn to the left and at this point the helicopter was descending. The helicopter made a left turn and started to proceed back in a westerly direction when the helicopter disappeared over the hill and behind the woods. [The witness] stated that the nose of the helicopter was at an approximate 45 degree angle down when disappearing. It was at this point when [the witness] heard a loud bang..." OTHER DAMAGE An area of approximately 62 feet by 10 feet of crops was damaged. PERSONNEL INFORMATION The pilot was 31 years old and was employed by the Milwaukee County Sheriff as a law enforcement officer. He held a commercial pilot certificate with airplane single engine, airplane multiengine land, and rotorcraft ratings with instrument airplane and helicopter ratings. The pilot received a second-class medical certificate on March 3, 2000 with no waivers or limitations. Logbook entries indicate that on September 17, 1998 the pilot flew in a UH-60A and logged a total rotorcraft time of 534.6 hours with 20.7 hours of actual instrument flight time. On March 15, 1999, the pilot attended a 5-day Bell OH-58 Ground and Flight Procedures training at the Bell Helicopter Customer Training Academy. The course was comprised of 20 hours of ground school in OH-58 helicopter systems and 3-5 hours of dual flight instruction in visual flight rules VFR maneuvers. The last written logbook entry on May 29, 2000, indicates that the pilot accumulated a total rotorcraft time of 656 hours and 20.7 hours of actual instrument flight time. The pilot had flown 5 hours in a 24-hour period preceding the accident. AIRCRAFT INFORMATION The helicopter, serial number 6816718 (Military 40032), was inspected on June 30, 2000 at a total airframe time of 3,189.6 hours at the time of a 100/300-hour inspection. The helicopter accumulated a total time of 3,229.7 hours. An Allison 250-C20C (military designation T63-A720) engine, serial number AE-404280 rated at 420 shaft horsepower, powered the helicopter. The engine had a total time of 2,480.7 hours. METEOROLOGICAL INFORMATION N626SF received a VFR (visual flight rules) weather briefing from the Greenbay AFSS on August 17, 2000, from 1047-1101. A certified rerecording of the briefing is included this report. AIRMET Sierra, update 6, for IFR (instrument flight rules) conditions from, valid until 2100 on August 17, 2000, stated, occasional ceilings below 1,000 feet agl, visibility below 3 sm, and scattered precipitation/mist. The AIRMET stated that conditions were continuing beyond 2100 on August 17, 2000 thru 0300 on August 18, 2000. The Watertown, Wisconsin, automated weather observing system (AWOS-3), reported, at 2204, wind from 350 degrees at 6 knots, 7 sm visibility, an overcast ceiling of 900 feet agl, temperature of 17 degrees C, dew point of 17 degrees C, and an altimeter setting of 29.99 inches of mercury. According to Federal Aviation Administration (FAA) Advisory Circular AC 00-6A, Chapter 5, Moisture, Cloud Formation, and Precipitation, Temperature-Dew Point Spread, "The difference between air temperature and dew point temperature is popularly called the "spread". As the spread becomes less, relative humidity increases, and it is 100% when temperature and dew point are the same. Surface temperature-dew point spread is important in anticipating fog but has little bearing on precipitation..." WRECKAGE AND IMPACT INFORMATION The main wreckage was located approximately 6 1/2 nm northeast of Watertown, Wisconsin. Ground scarring and wreckage distribution extended for a length of approximately 133 feet on a magnetic heading of 086 degrees through a bean field and sloping terrain. The western edge of ground scarring contained the nose section of helicopter's left skid side step. Approximately 67 feet from the ground scar's western edge, was a 3-foot section of the main rotor, the left cabin door and a 3-foot section of the left front skid. All wreckage was found within the immediate area of the accident site. Examination of the engine revealed that the N1 and N2 sections could be rotated by hand. A liquid consistent with Jet A was present in the fuel line leading to the fuel nozzle. The upper, lower and freewheeling chip plugs did not display the presence of metallic particles. Vegetation and soil similar to that at the accident site was found in the inlet section of the engine and the outflow valve, which was in the open position. The bladder fuel tank was separated from the airframe and found to contain approximately 50 gallons of liquid consistent with Jet A. Sections of the main rotors were attached to the main rotor shaft. The "red" blade was separated at a point located 3 feet from its root. The "white" blade was delaminated approximately 2 feet from its root. The pitch change links are also attached with separation points located approximately 1 foot below the "white" blade and 6 inches below the "red" blade. Both areas of separation exhibited deformation and a dimpled surface with a 45-degree fracture along the surface's circumference. The pitch change links and cyclic control were connected to the swash plate. The main rotor transmission was rotated 360 degrees by hand. Both transmission chip plugs did not display the presence of metallic particles. The tail boom was 10 feet in length with both horizontal stabilizers attached. The tail boom exhibited crushing at its point of separation. The left horizontal stabilizer was deformed in the upward direction at a point located approximately 1 1/2 feet from its root. Tail rotor drive shaft and control continuity of the tail rotor was confirmed through a torsional fracture located approximately 2 1/2 feet from the tail rotor gearbox. The gearbox contained a red colored fluid. The tail rotor gearbox chip plug did not display the presence of metallic contaminates. One of the two tail rotor blades was deformed outward approximately 80 degrees 10 inches from the blades root. The second blade exhibited outward bending approximately 5 inches from its tip. The tail cone was found along the wreckage path. The three flight control actuators were separated from the airframe and located with the main wreckage. MEDICAL AND PATHOLOGICAL INFORMATION Autopsies of the pilot and observer were conducted by the Milwaukee County Medical Examiner on August 18, 2000. FAA toxicological test results of the pilot were negative for all substances tested. TEST AND RESEARCH Examination of the flight control actuators and freewheeling clutch were performed at Bell Helicopter Textron under the supervision of the National Transportation Safety Board (NTSB). No mechanical anomalies were reported with the actuators. The freewheeling unit was exhibited torsional overload. (The freewheeling unit is defined as, "A component of the transmission or power train that automatically disconnects the main rotor from the engine when the engine stops or slows below the equivalent r.p.m.) The Certified Flight Instructor (CFI) who flew with the accident pilot conducting training for the Milwaukee County Sheriff's Department made a statement regarding the training and operations. A copy of the CFI's statement is an attachment to this factual report. The Milwaukee County Sheriff provided a written response to the certified flight instructor's comments. The written response is attached, in its entirety, to this report. ADDITIONAL INFORMATION The flight department was comprised of a director of operations, a chief pilot, two pilots and one observer. The director of operations stated that he was not a pilot. The chief pilot sets decisions with regards to training requirements. During the meeting, the chief pilot reported that the attitude indicator was inoperative on N626SF and that a draft minimum equipment list was provided to all the pilots prior to the accident. During the meeting, a pilot stated that the turn coordinator, air speed indicator and altimeter were operative. The Milwaukee County Sheriff's Aviation Division's standard operating procedures (SOP's) was provided to the NTSB. The document, which is included in this report, states under section 3/033.05 Basic VFR Weather Minimums, Basic VFR weather minimums shall conform to those minimums outlined in FAR 91.155 and 91.157. In addition to these requirements, the following minimums will apply: Inside Local Flying Area Ceiling Visibility (50 NM Radius of ADF) Day 600 1 Night 800 2 Outside Local Flying Area Ceiling Visibility Day 800 2 Night 1,000 3 A June 4, 2000 draft of an MEL, prepared by the chief pilot, was addressed to "Aviation Division Personnel". The draft MEL stated that the attitude indicator is, "Not required during daylight. Not required at night when in VMC [visual metrological conditions] conditions". The Milwaukee County Sheriff provided a written response regarding : "The Status of the Minimum Equipment List (MEL)". The written response is attached, in its entirety, to this report. On May 19, 2000, the chief pilot made an entry into the "Inspection/Discrepancy Log" for the helicopter. The entry stated, "Attitude indicator does not work". The log did not show any "corrective action". From May 19, 2000 to June 4, 2000, the "Air Crew Mission Briefing Form[s]" indicated that there were day and night flights flown by the pilots and the chief pilot. FAA-H-8083-21, Rotorcraft Flying Handbook, Chapter 12, Attitude Instrument Flying, states under Attitude Indicator: "The attitude indicator provides a substitute for the natural horizon. It is the only instrument that provides an immediate and direct indication of the helicopter's pitch and bank attitude..." FAA-H-8083-21, Rotorcraft Flying Handbook, Chapter 13, Night Operations, states under Night Flight: "The night flying environment and the techniques you use when flying at night, depend on outside conditions. Flying on a bright, clear, moonlit evening when the visibility is good and the wind is calm, is not much different from flying during the day. However, if you are flying on an overcast night over a sparsely populated area, with little or no outside lights from the found, the situation is quite different. Visibility is restricted so you have to be more alert in steering clear of obstructions and low clouds. Your options are also limited in the event of an emergency, as it is more difficult to find a place to land and determine wind direction and speed. At night, you have to rely more heavily on the aircraft systems, such as lights, flight instruments, and navigation equipment. As a precaution, if visibility is limited or outside references are inadequate, you should strongly consider delaying the flight until conditions improve, unless you have received training in instrument flight and your helicopter has the appropriate instrumentation and equipment." FAA-H-8083-21, Chapter 14, Night Operations, states under Assessing Risk: "Examining NTSB reports and other accident research can help you to assess risk more effectively. For example, the accident rate decreases by nearly 50 percent once a pilot obtains 100 hours, and continues to decrease until the 1,000 hour level. The data suggest that for the first 500 hours, pilots flying VFR at night should establish higher personal limitations than are required by the regulations and, if applicable, apply instrument flying skills." The Federal Aviation Administration and Bell Helicopter Textron Incorporated were parties to the investigation. The wreckage was released and retained parts were returned to Associated Aviation Underwriters.
The spatial disorientation by the pilot during continued flight into instrument conditions and the inadequate surveillance by the operator. The inoperative attitude indicator and night conditions were contributing factors.
Source: NTSB Aviation Accident Database
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