N626SF

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 instru...