Shelbyville, TX, USA
N85BH
Bell 206B-3
While in a slow flight out of ground effect the helicopter lost control and impacted heavily wooded (100-110 foot trees) terrain while on a United Stated Forest Service (USFS) prescribed fire mission. The prescribed fire was supported by the application of aerial ignition spheres utilizing a cabin mounted plastic sphere dispenser (PSD) machine. According to USFS operating procedures, PSD missions are typically flown at 50-300 feet above the top of the highest vegetation at airspeeds from 20-40 knots. While on the mission a radio distress call,"Mayday, Mayday, Mayday, we are going down," was heard on the mission operating frequency. According to USFS personnel, the voice making the distress call appeared to be that of the ignition specialist on board, not the pilot. No further communications were heard from the helicopter. Post accident examinations and testing of the engine, fuel control, and power turbine governor did not reveal conclusive evidence of mechanical failure. Examination of the airframe did not reveal evidence of a control system failure. Fuel calculations determined that the helicopter should have had about 36.9 gallons of usable fuel on board at the time of the accident. Evidence at the accident site showed some rotation signatures of dynamic drive components, although a power level could not be determined. The USFS inspection of the PSD machine did not reveal evidence of a malfunction that could have contributed to the accident. The helicopter was within weight and balance limits for the type of operation. The reason for the loss of control could not be determined.
HISTORY OF FLIGHT On March 10, 2005, approximately 1354 central standard time, a Bell 206B-3 helicopter, N85BH, sustained substantial damage when it impacted heavily wooded terrain in the Sabine National Forest near Shelbyville, Texas. The airline transport rated pilot and two United Stated Department of Agriculture (USDA) Forest Service (USFS) crewmembers sustained fatal injuries. Visual meteorological conditions prevailed, and the flight/mission was being monitored and conducted in accordance with USFS aviation policies for public use aircraft in fire management operations. The flight departed at 1347 from a field helicopter pad (H1), located approximately 7 miles southeast of the accident site. On the morning of the accident, the helicopter was assigned to support a prescribed fire within heavily wooded terrain with 100-120 foot high trees near Shelbyville, TX. The prescribed fire was supported by the application of aerial ignition spheres utilizing a cabin mounted plastic sphere dispenser (PSD) machine. According to USFS operating procedures, PSD missions are typically flown at 50-300 feet above the top of vegetation at airspeeds from 20-40 knots. The helicopter was based at Angelina County Airport, Lufkin, Texas. Approximately 0928, after a mission brief, the helicopter, with pilot and two USFS personnel on board, and the re-fueling truck re-positioned to H1 (coordinates North 31 degrees 42.110 minutes West 93 degrees 52.540 minutes) and were met by support equipment and personnel from the Sabine National Forest to conduct a prescribed fire mission. Approximately 1234 an initial recon of the burn area began, followed by approximately 11 minutes of aerial ignition work on the same flight. Approximately 1300 the PSD machine experienced a sphere jam, and the helicopter returned to H1 to resolve the problem. The helicopter shut down at H1 while the PSD machine problem was resolved. The helicopter then departed H1 at 1347 to resume the mission. According to USFS records from ground personnel on the burn, at 1352, the mission ignition specialist onboard the aircraft reported by radio that the helicopter was commencing firing operations. At 1354, a radio distress call was heard by 7 personnel on the burn. According to USFS personnel, the voice making the distress call appeared to be that of the ignition specialist, not the pilot. The call was, "Mayday, Mayday, Mayday, we are going down." No further communications were heard from the helicopter. At 1417, the helicopter wreckage was found at coordinates North 31 degrees 45.425 minutes West 94 degrees 00.244 minutes. Immediate rescue operations commenced. One USFS employee initially survived the crash and was being transported by ambulance to a local hospital. The passenger died during transport due to extensive injuries sustained in the crash. PERSONNEL INFORMATION A review of Federal Aviation Administration (FAA) airman records revealed that the pilot held an airline transport pilot certificate with ratings for airplane single engine land, airplane multiengine land, and rotorcraft-helicopter, and a certified flight instructor certificate with ratings for single and multiengine land, rotorcraft-helicopter, and airplane and rotorcraft instrument. He was also an FAA certificated advanced and instrument ground instructor. His most recent FAA first class limited medical certificate was issued on September 7, 2004, with the limitation, "must have available glasses for near vision" At this time, he reported a total of 3,000 flight hours. The pilot's personal logbook was obtained. During a review of the logbook, several discrepancies were noted. Rotorcraft time appears to be consistent from the time rotorcraft time is first logged through the page ending February 20, 2004, at which time the pilots logbook shows a total rotorcraft time of 286.1 hours. On the page ending March 2, 2004, in the amount forwarded column, rotorcraft time increases to 1286.1. The page total is 27.3, which was added to time from the previous page for a total time of 1323.4 hours. This was an unaccounted 1,000-hour increase in rotorcraft time from the previous page. The extra 1,000 hours were added to and subtracted from cumulative flight time throughout the remainder of the logbook entries. The last entry in the logbook reflects the pilot's total time in all aircraft to be 2,187.8 hours, 384.4 of that in rotorcraft, and 115.9 hours in make and model. AIRCRAFT INFORMATION The 1980-model Bell 206B-3 helicopter was a single pilot, five place, single engine, light helicopter with a two-blade semi rigid main rotor, and a tail rotor that provided directional control. The helicopter was owned by Brainerd Helicopter Service, Inc, and operated by the United States Forest Service. A review of the aircraft logbooks revealed that the last annual inspection was performed on April 26, 2004, at a tachometer time of 309.27 hours. The tachometer read 2,837.4 at the scene of the accident. The aircraft total time was determined to be 4,565 flight hours at the time of the accident. The helicopter was equipped with a Rolls Royce 250-C20B engine, serial number (S/N) CAE-840516. Historical records for the engine began on April 12, 1991, with 463.1 hours total time. The engine was converted to a Model 250-C20B (same serial number) on March 15, 1993, with a total time of 907.3 hours. Records continued with periodic inspections (100, 300, 600 and Annual) through February 22, 1999. The February 22, 1999, entry indicated that engine, S/N CAE-270208, was removed due to metal on the upper and lower chip detector plugs. There were no previous indications that engine S/N CAE-270208 had been installed. The total time prior to this entry was reflected as 2,653.2 hours on January 1, 1999, and according to the records, should have been for engine S/N CAE-840516. This total time was carried forward to the questionable entry on February 22, 1999, and subsequently crossed out and replaced with an engine total time of 2,296.2. The airframe log showed an entry for engine, S/N CAE 840516 being installed on February 22, 1999, but did not show engine S/N CAE 270208. The entry appeared to be inserted between two previously entered items on a single line and overlapped the A&P mechanics number from the previous entry. History of engine S/N CAE 840516 could not be determined from the records presented. Historical records shows the last entry for engine S/N CAE 840516 was on 16 December 2004. Total time was recorded as 4,142.7 hours. The airframe total time was recorded as 4,499.5 hours total time. The daily log indicated a total time of 4,175.6 hours for the engine and 4,563.1 hours for the airframe. The serial number on the component card (FF357738) differed from the serial number on the Canadian Authorized release Certificate (FF37596) for the Bleed Valve. METEOROLOGICAL INFORMATION The automated weather observing system at the A.L. Mangham Junior Regional Airport, near Nacogdoches, Texas, located approximately 30 miles southwest of the accident site, reported wind from 250 degrees at 5 knots, 10 statute miles visibility, a clear sky, temperature 22 degrees Celsius COMMUNICATIONS The ignition specialist (FS crewmember in left front seat) was communicating with ground personnel on a U.S. Forest Service Tach channel at the time of the accident. He reported that he was resuming fire operations at 1352. At 1354, the ignition specialist made a "Mayday" call on the frequency. There were no further communications from the aircraft. WRECKAGE AND IMPACT INFORMATION The helicopter came to rest on its right side in a heavily wooded area on a heading of 135 degrees at coordinates North 31:45.425 West 94:00.244. The initial point of impact was identified as the tops of 50-foot trees located around the wreckage. Global positioning system (GPS) elevation at the accident site was 386 feet msl. Fuselage - The right skid was fractured just forward of the forward mounting saddle, and the fuselage floor was fractured aft of the forward cross tube. Impact damage was observed on the right rear portion of the fuselage. Approximately 15 pounds of personal gear was found in the aft baggage compartment. Front right and left doors were not installed. The nose of the helicopter exhibited light crushing and all of the Plexiglas chin bubble was broken out. The right forward door post was bent inward and upward. Damage to the left side of the fuselage was unremarkable. No fuel found in the tank; however, an odor consistent with that of jet fuel was present at the accident site. The fuel boost pump access panels were removed, and the rear boost pump valve locking bar was found loose (approximately 0.065 in.). The forward boost pump valve locking bar was found slightly loose (0.035 in). The fuel quantity indicating float access panel was removed, and the forward fuel quantity indicator lead ("C" post) was found in a loose condition. Cockpit - All circuit breakers were in and the battery and generator switches were found in the "ON" position. The Hobbs meter indicated a time of 2,837.4 hours. The directional gyro/attitude indicator switch was "ON". The altimeter was set to a barometric pressure setting of 30.09 inches of Mercury. The directional gyro indicated a 210 degree heading. The artificial horizon displayed a nose-up right-bank attitude. The fuel valve switch was "ON". The right seat pan was crushed downward approximately two inches. Located at the forward most point of the wreckage debris were two Interstate DCS-33 12-volt batteries, which were reportedly removed from the helicopter battery compartment during rescue operations. Controls - Control continuity to all flight controls was established. The collective control lever exhibited overload fracture outboard of the collective attachment control collar. Movement at the collective hydraulic actuator bell crank resulted in corresponding movement at the collective attachment control collar, and pre-impact control continuity was confirmed from the collective up to the main rotor system. The cyclic control stick exhibited an overload fracture at the base of the stick forward of the attachment collar. Movement of the control tubes resulted in the movement from the attachment collar up to the hydraulic actuator. A visual inspection confirmed control continuity from the hydraulic actuator to the main rotor pitch change horns. The anti-torque control tube was fractured at the tail rotor control pedal bellcrank. Removal of the broom closet panel revealed that movement of the tail rotor control tube was prevented due to crushing of the surrounding structure. Movement of control tube above the crushing resulted in corresponding movement of the control tube forward of the fracture at the tailboom. The tailboom section of the anti-torque control tube was separated from the tailboom during the impact sequence, and each end exhibited overload fracture. Movement of the control tube at the forward end of the tail rotor resulted in a corresponding pitch change in the tail rotor blades, confirming pre-impact control continuity in the anti-torque pedal system. Transmission and Main Rotor System - The transmission remained attached to the airframe and the main transmission pylon mounts remained in place and attached to main transmission. The transmission displaced in an aft, downward direction, forcing the K-flex coupling into the isolation mount cover. The forward attachment of the main driveshaft was separated at the K-flex coupling and had multiple overload fractures of the K-flex. Scoring of the roof panel adjacent to the fractured K-flex was observed, and was consistent with circumferential flailing of the drive shaft, indicative that the drive was rotating at impact. There was no notable damage to the main rotor control system, up to the rotating swashplate. One of the two pitch change control tubes, extending from the rotating swashplate to the pitch-change horn, displayed an overload fracture approximately mid-length. One rotor blade, which reportedly came to rest forward of the main wreckage, exhibited trailing edge impact damage that was consistent with the diameter of trees in the immediate vicinity of the impact. The blade fractured just outboard of the doublers. The other blade exhibited trailing edge impact, and chord wise damage. The blade also exhibited chord wise scoring throughout the length of the blade. Both blades displayed damage consistent with a high pitch, slow turning rotor at impact. Tail Rotor - The tailboom fractured just forward of the tail rotor gear box mounting pad. As a result, the tail rotor control tube fractured in overload as described above. Additionally, the tail rotor drive shaft decoupled from the tail rotor gear box and the aft portion of the tailboom, along with the tail rotor gear box assembly was located approximately 15 feet from the main wreckage. The tail rotor assembly remained intact, though the tail rotor blades displayed both impact and fire damage. The tail rotor pitch change assembly moved freely by hand and resulted in corresponding pitch change of the tail rotor blades. As the tail rotor blades were rotated by hand, the gear box rotated freely without any identifiable grinding or binding. The chord wise accordion bending of the tail rotor blades was consistent with low, or no, power at impact. The forward end of the tail rotor drive shaft exhibited torsional shearing. Deformation of spacers was progressively more identifiable forward of the torsional separation in the tail rotor drive. All hanger bearings rotated freely with no evidence of heat distress. The aft end spline of the tail rotor drive shaft was found decoupled. The torsional shearing of the tail rotor drive shaft was consistent with sudden stoppage forward of the drive shaft fracture point. Engine - The left side of the engine compartment appeared normal. The left side engine mounts were intact. The Pc pneumatic air line was intact to the PT Governor "T" fitting. All pneumatic system B-nuts were at least finger tight. The PT Governor pointer indicated a high power application. The linkage was intact in the engine compartment, but was separated on the hydraulic deck and at the collective itself. The right side engine compartment door was uniformly crushed into the right side of the engine. The right side engine mounts were bent. The horizontal fire shield was crushed inward from the right side. The right side compressor air discharge tube was crushed from a right side impact. The forward end was partially separated from the compressor scroll. The right side of the outer combustion case was partially crushed from impact. There were no noted separated pneumatic tubes. Some tubes were crushed and deformed from impact damage. All pneumatic system B-nuts were at least finger tight. The 4th stage power turbine wheel would not rotate with attempts at hand rotation. PSD Machine - The PSD machine was found inside the aircraft still strapped in its installed position. Some slight denting damage was found on the hopper and the plastic lid was broken off from the hopper at the hinges. Plastic spheres had been ejected from the hopper and were strewn within the cabin and outside the cabin around the aircraft. Several nylon fabric bags containing additional plastic spheres were still securely attached to their tether and intact. In each of the two slipper blocks on the same side as the PSD machine controls, slipper blocks 1 and 2, a partially burned plastic sphere was found. That is, one plastic sphere in slipper block 1 and one plastic sphere in slipper block two. The other two slipper blocks, 3 and 4, were empty. Black ash residue was found on the outside of the lower portion of the feed chutes above blocks 1 and 2. The inside feeder control lever was in the up position. This lever in the up position allows the plastic spheres to feed into the two inner slipper blocks; slipper blocks 2 and 3. The outside feeder control lever was in the down position. In the down position, plastic spheres are restricted from entering blocks 1 and 4. The power control toggle switch was found in th
The pilot's failure to maintain altitude and clearance for undetermined reasons.
Source: NTSB Aviation Accident Database
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