POPLAR BLUFF, MO, USA
N77MP
Bell OH-58A
The helicopter departed controlled flight while en route to the Poplar Bluff Airport, Poplar Bluff, Missouri. A witness stated that the helicopter appeared to be 450 feet agl. The helicopter was then reported by the witness to have made three to four rotations during its descent. The OH-58A/C lists procedures for the 'COMPLETE LOSS OF TAIL ROTOR THRUST'. Examination of the tail rotor drive shaft revealed a 45-degree torsional fracture. There was rotational scoring near the fracture area on the interior housing for the tail rotor drive shaft. An elastic material with navy blue yarns was found wrapped around the tail rotor. The yarns were consistent with those of a navy blue warm up jacket found along the reported flight path. The helicopter's entry doors were removed for the flight.
HISTORY OF FLIGHT On May 17, 1999, at 1608 central daylight time, a Bell OH-58A, N77MP, operated by the Missouri State Highway Patrol, was destroyed on impact with terrain in the city of Poplar Bluff, Missouri. Visual 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 private pilot and passenger sustained fatal injuries. The local photography flight departed Dexter Municipal Airport, at approximately 1400, and later diverted to Malden Municipal Airport (MAW), Missouri, due to an approaching storm. The flight then departed MAW, at approximately 1545, en route to the Poplar Bluff Municipal Airport (POF), Poplar Bluff, Missouri. A witness reported that, while he was driving, he saw a helicopter flying southbound at an altitude of approximately 350-400 feet above ground level. He stated that he saw what was possibly a large bird hit the rear rotor of the helicopter, after which two objects, approximately the size of grapefruits, fell to the ground. He further stated that the objects were falling slowly as if they were light and not fast like something heavy. A second witness reported, "...I noticed a Black H58 helicopter aloft moving from my left to my right. It appeared to be about 450' [feet] agl, nose slightly below level, when it suddenly pitched up and rotated slightly below level, when it suddenly pitched up and rotated sharply to its left. It seemed to simultaneously pause forward motion for a moment, then began a counterclockwise descent. It made three or four complete rotations before it disappeared behind some trees...". PERSONNEL INFORMATION The 41 year old Missouri State Highway Patrol pilot held a private pilot certificate with airplane single engine land, instrument airplane and helicopter ratings. Federal Aviation Administration (FAA) records indicated no history of aircraft accidents, incidents or enforcement action. Logbook entries showed that the pilot had accumulated a total airplane flight time of 2,850.6 hours as of January 7, 1999 and a total rotorcraft flight time of 580.9 hours as of the last logbook entry on November 19, 1998. He received a second class medical with no restrictions on January 27, 1999. Pilot logbook entries showed that the pilot received 26.9 hours of dual instruction and accumulated 51.7 hours in rotorcraft prior to obtaining a rotorcraft rating on June 5, 1997 which was conducted in the accident aircraft. The Missouri Highway Patrol reported that the pilot had accumulated an airplane flight time of 17 hours and a helicopter flight time of 18.6 hours from January 5, 1999 to May 17, 1999. Training records indicated that the pilot received recurrent airplane training in 1994, 1995, 1997 and 1999. The pilot received 8.0 hours of recurrent training in a airplane simulator from January 6, 1999 to January 7, 1999. A biennial flight review, referencing FAA Regulation 61.56(e), FAA Pilot Proficiency Award Program, was logged in the pilot's logbook on January 7, 1999. There were no logbook entries indicating that the pilot had received helicopter training after obtaining his rotorcraft rating. AIRCRAFT INFORMATION The helicopter was transferred from the United States Army to the Missouri State Highway Patrol through a surplus program under the National Defense Authorization Act on September 6, 1996. The helicopter had a total airframe time of 3,896 hours when it was received by the Missouri State Highway Patrol which then operated it as a public-use aircraft. A 100/200-hour inspections of the engine and airframe were completed on November 30, 1998 at a total engine time of 1,980.9 hours and a total airframe time of 4,412.9 hours. On May 16, 1999, the helicopter had accumulated an approximate total engine time of 2,011 hours and an approximate total airframe flight time of 4,443 hours. The engine had accumulated a approximately 959 hours since overhaul. The helicopter was equipped with two cockpit and two cabin entry doors. The aircraft had been operated on previous flights with the doors removed during missions involving search, rescue, marijuana eradication, and photo flights. The cockpit entry doors were removed for the accident flight for the purposes of photography. AIRPORT INFORMATION MAW was approximately 23 nmi on a magnetic heading of 116 degrees from the accident site. POF was approximately 5 nmi on a magnetic heading of 091 degrees from the accident site. WRECKAGE AND IMPACT INFORMATION A search by the parties to the investigation found a navy blue warm-up jacket along the flight path of the helicopter which was reported by witnesses. The navy blue warm-up jacket was approximately 1,579 feet on a magnetic heading of 040 degrees from the helicopter. The jacket was found lying on a tree stump located at the edge of a grass field belonging to a school. The jacket was muddy and torn in several areas, and did not have an attached hood or waistband. The helicopter was found in an upright position between a one-story brick office building and an embankment. The embankment was approximately 10 feet in height on top of which were trees and a residential neighborhood. The helicopter was in an upright position and orientated on a magnetic heading of 143 degrees which was approximately parallel to the wall of the office building. The main rotor and tail rotor were intact with their respective control linkages. The tail rotor blade did not have any scoring or gouging in the rotational direction. There was a 45-degree fracture of the tail rotor drive shaft. The fracture was located between two hanger bearings which were inline with the leading and trailing edges of the horizontal stabilizers. The surface of the tail cone and tail rotor drive shaft housing exhibited scoring, in the lateral direction, in an area around the fracture. There was a white elastic cloth material, estimated to be 24 inches by 1/2 inches in dimension, wrapped and stretched around the tail rotor shaft, pitch change links and blades. There were surface imprints similar to the fiber pattern of the elastic material on both tail rotor blades and on the surface of the left horizontal stabilizer. Flight control and engine control continuity was established. Continuity of the transmission and tail rotor gear box was established. Both transmission chip detectors and tail rotor chip detector did not contain metallic contaminants. Both engine igniters did not contain contaminants. The engine stator and rotor blades were intact. Debris similar to the surrounding soil of the accident site was found in the exhaust section of the engine. MEDICAL AND PATHOLOGICAL INFORMATION An autopsy was conducted by the Butler County coroner. FAA toxicological results tested positive for pseudoephedrine, ephedrine, and phenylpropanolamine. Pseudoephedrine is a decongestant, available over-the-counter, often known by the trade name Sudafed. Ephedrine is an asthma medication, available over-the-counter in tablet form, often known by the trade name Primatene. It is also available in many nutritional supplements such as ephedra, also known as Ma Huang. Phenylpropanolamine is a metabolite of ephedrine, also available itself as an over-the-counter decongestant. TESTS AND RESEARCH Sections of Advisory Circular 61-91H Pilot Proficiency Award Program states the following: 6. PARTICIPATION IN THE PILOT PROFICIENCY AWARD PROGRAM IN LIEU OF A FLIGHT REVIEW. A pilot need not accomplish the flight review requirements of 14 CFR part 61, 61.56 if, since the beginning of the 24th calendar month before the month in which the pilot acts as pilot in command, he or she has satisfactorily completed one or more phases of an FAA-sponsored Pilot Proficiency Award Program in an aircraft (reference 61.56(f)). 7. TRAINING REQUIREMENTS PHASES I THROUGH XX. Minimum requirements, which include specific subjects and flight maneuvers, have been established for airplanes, seaplanes and amphibians, rotorcraft, gliders, light-than-air aircraft, and ultralights. The required training profiles represent those phases of operation that have been identified by accident reports as phases most likely to produce accidents. These training profiles are established for each category of aircraft. Pilots may select the category and class of aircraft or ultralight in which they wish to receive their flight training. All training must place special emphasis on safety of flight operations. All training requirements for each phase of the program must be completed within 12 months. After completing a phase of the program, pilots must pass between the date of completion of a phase and application for the award for the next phase. a. Airplanes. (1) One hour of flight training to include basic airplane control, stalls, turns, and other maneuvers directed toward mastery of the airplane. (2) One hour of flight training to include approaches, takeoffs, and landings, including crosswind, soft field, and short field techniques. (3) One hour of instrument training in an airplane, FAA-approved aircraft simulator, or training device. NOTE: If the applicant is not qualified and current in accordance with 61.57 for instrument flight, 1 additional hour of basic instrument training with emphasis on partial panel approaches, inadvertent penetration into instrument meteorological conditions (180 degree turn), descent into visual meteorological conditions, and safe operations shall be accomplished in an airplane, seaplane, FAA-approved aircraft simulator, or training device for each odd-numbered award phase (Phase I, III, V, etc.). c. Rotorcraft. (1) One hour of ground training to include the use of the rotorcraft flight manual to determine operating limitations, weight and balance computations, performance data, aircraft servicing, use of optional equipment, and standard emergency procedures. (2) One hour of flight training to include airport and traffic pattern operations, including departures from a hover (helicopter only), normal and crosswind approaches and landings, maximum performance takeoffs, and steep approaches. (3) One hour of flight training to include systems orientation, authoritative descents, power failure at a hover, settling-with-power, pinnacle/rooftop takeoffs and landings, and navigation procedures. The Missouri State Highway Patrol Aircraft Operations Standard Operating Procedure, revision 3-96, states in section VI. Training, paragraph D., Bi-Annual Flight Review, states, "At least every two years each pilot must review the following procedures with a CFI and have their pilot logbook endorsed accordingly. A copy of this log book entry will be forwarded to the Director of the Aircraft Division. This training should include the following for each rating the pilot holds: ..." For rotorcraft rated pilots, the manual describes the training as: a) Normal takeoff and landings. b) Takeoffs and landings from confined area. c) Cross wind takeoffs and landings. d) Left and right pedal turns, climbing turns, steep turns. e) Hovering and maneuvering at minimum speeds. f) Rapid descent and quick stops. g) Simulated emergency procedures (engine failure, fire, structural damage, stuck pedals, etc.) h) Autorotations from hover and altitude (No full-on Autorotations from altitude are allowed during simulated emergencies) i) Training for inadvertent instrument meteorological conditions (IMC) from VFR flight. The operator's manual for the Army Model OH-58A/C states, within a note, under 9-19. COMPLETE LOSS OF TAIL ROTOR THRUST, "Degree of roll and sideslip may be varied by varying throttle and/or collective. (At airspeeds below 40 knots, the sideslip may become uncontrollable, and the helicopter will begin to spin on the vertical axis.)". Section 9-19, Complete Loss of Tail Rotor Thrust, states, "This situation involves a break in the drive system, such as a severed driveshaft, causing the tail rotor to lose power. For powered flight, the emergency procedures listed are: (a) If safe landing area is not immediately available, continue powered flight to suitable landing area at or above minimum rate of descent autorotational airspeed. (b) When landing area is reached, make an autorotative landing. (c) Use airspeed above minimum rate of descent airspeed. (d) If landing area is suitable for run-on landing, touch down above effective transnational lift. (e) If run-on landing is nor possible, start to decelerate from about 75 feet altitude, so that forward ground speed is at a minimum when the helicopter reaches 10 to 20 feet. Execute the touchdown in a level attitude with minimum ground speed. The elastic cloth material along with a sample of the navy blue warm-up jacket flight path was sent to the National Transportation Safety Board's Materials Laboratory for examination. The color, size, and texture of the navy-blue yarns in the elastic material were consistent with those found in the navy blue warm-up jacket. ADDITIONAL INFORMATION The FAA, Bell Helicopter, Rolls-Royce Allison, and the Missouri State Highway Patrol were parties to the investigation.
The tail rotor's impact with the blue warm-up jacket and the subsequent overload of the tail rotor drive shaft. A contributing factor was the absence of the helicopter's entry doors.
Source: NTSB Aviation Accident Database
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