History of Flight
On March 30, 2015, at about 1436 central daylight time, a Bell 206 L-1 helicopter, registration N50KH, operated by T & M Aviation under contract with the US Forest Service, impacted terrain near Saucier, Mississippi, during an aerial ignition mission for a prescribed burn. The helicopter was destroyed by the subsequent controlled burn fire. The commercial pilot and front left seat crew member suffered fatal injuries; the rear seat crew member sustained serious injuries. Visual meteorological conditions prevailed, and no flight plan was filed for the Part 137 aerial application flight, which departed Dean Griffin Memorial Airport (M24) in Wiggins, Mississippi, at about 1334.
A witness on a road south of the burn area observed the helicopter turn and return. About seven seconds later, he heard a sound similar to an air hose being unplugged from a high-pressure air tank, followed by impact about three seconds later. The witness reported no unusual helicopter behavior except the sound. The helicopter's last radio transmission to ground personnel occurred approximately seven minutes before the accident.
Several Forest Service personnel were conducting ground operations for the controlled burn. None witnessed the crash or heard a distress call. Witnesses reported small smoke plumes drifting east due to westerly winds. One witness stated a crew member inquired about smoke levels and decided to continue after deeming them safe. No witness observed the helicopter contacting smoke.
Satellite tracking data from the Automated Flight Following (AFF) system showed the helicopter operated at low altitude over the burn area for about 56 minutes, following a northwest-to-southeast grid pattern. The last recorded position at 1433 indicated an altitude of 354 feet mean sea level (132 feet above ground level), heading 150 degrees true, and groundspeed 43 knots. A reconnaissance flight was conducted earlier that morning and lasted approximately 72 minutes.
Personnel Information
The 40-year-old commercial pilot held a rotorcraft-helicopter rating and a mechanic certificate with airframe and powerplant ratings. His most recent FAA second-class medical certificate was issued February 23, 2015, with a restriction to wear corrective lenses. He began as an aircraft technician with T&M Aviation in 1998, received flight instruction from a company owner, and obtained his commercial pilot certificate in 2005. His flight experience included agricultural spraying, external load operations, low-level reconnaissance, and prescribed burn operations. He also served as director of maintenance from 2010 to 2013. His most recent FAR Part 135 proficiency check was completed on February 3, 2015, in a Bell 206 L-3, including emergency simulations. He was approved for aerial ignition operations through April 30, 2015, after an interagency evaluation. According to his logbooks, he had accumulated 6,471 total flight hours, with approximately 6,300 hours in the accident helicopter make and model. The owner estimated 22 additional hours in the preceding 90 days.
Aircraft Information
The helicopter was manufactured in 1980 and originally equipped with an Allison 250-C28 engine. In 1993, an Allison 250-C30P engine was installed via supplemental type certificate, and further modified in 2001. At the time of the accident, the helicopter had about 11,602 flight hours. Maintenance records were largely destroyed by the fire, but archived records showed the most recent 100-hour inspection was completed on March 11, 2015, at 11,597 hours. Life-limited components (gearbox, compressor, turbine) were within their respective overhaul intervals. A scheduled Forest Service inspection on November 20, 2014, found no discrepancies. A turbine engine power check on February 28, 2015, recorded a trend value of +19 under conditions of 2°C and 10,000 feet pressure altitude, within operating limits.
A load calculation form was completed for the morning reconnaissance flight. The form indicated a total combined weight of 3,952 lbs, which was 198 lbs below the helicopter's published gross weight and 118 lbs below the Forest Service's reduced gross weight. An additional payload was calculated for a potential long-line mission, but the bucket and line were not used. At the time of the accident, the helicopter had burned about 196 lbs of fuel. Density altitude was 1,489 feet, with temperature 27°C and revised weight 3,756 lbs. The helicopter was operating within Area A of the out-of-ground-effect performance chart.
Fueling records were not available, but the helicopter was serviced with approximately 600 lbs of fuel before the morning flight. Fuel performance calculations indicated the helicopter landed at 1050 with about 133 minutes of fuel remaining, and was refueled before the accident flight. A post-accident fuel sample was clear and free of contaminants.
Meteorological Information
An NTSB weather study reported ceilings greater than 3,000 feet AGL, no visibility restrictions, and variable wind. At the accident time, wind at GPT was south/southwest at 10-20 knots; at BXA, west/northwest at 5-15 knots. Witnesses reported variable winds from northwest and south at about 5 mph. The atmosphere was unstable from the surface to 8,000 feet msl, with low-level wind shear between the surface and 1,000 feet msl, and layers of clear air turbulence. Radar reflectivity showed multiple targets likely from smoke and particulates. Smoke was present in the area, but little smoke at the accident site at impact.
Wreckage and Impact Information
The accident site was in a wooded area about one quarter mile north of a road at the southern end of the burn area. An initial impact point (IIP) was marked by several 80-foot-tall broken trees about 70 feet south of the main wreckage. The tail rotor marked the start of the debris path about 30 feet beyond the IIP on a northerly heading. The main wreckage, oriented northwesterly at about 180 feet msl, consisted of the cockpit, fuselage, engine, main rotor assembly, and blades. The high landing skid was aft of the main wreckage. The upper deck (main rotor, transmission, hydraulic servos) was attached and fire-damaged. The cockpit and cabin were destroyed by fire, except the center window frame and portions of the instrument panel. Both main rotor blades were fire-damaged: Blade A was slightly bent opposite rotation; Blade B had two 45-degree chordwise bends, with its tip separated due to overload. The tail rotor and tailboom were fire-damaged and located near a tree 20 feet south of the main wreckage.
Engine Examination
The engine was recovered and disassembled under NTSB supervision. Several accessories (accessory gearbox, fuel control unit, fuel pump) were consumed by fire. Air discharge tubes had impact damage but were properly seated. The compressor was intact without impact damage. The combustion section outer case was undamaged; the left side tube was dented with melted weld material. The combustion liner had no unusual burn patterns. N1 shafting and coupling were properly seated with heat damage. Power turbine shafts were in position. The fuel pump and lines were fire-damaged. The fuel nozzle showed no abnormalities despite thermal damage. Gears from the accessory gearbox showed fire exposure but no mechanical deformation. The turbine section had light rotational scoring on the stage four nozzle blade track.
Rotor Blade Examination
Photographs reviewed by an NTSB helicopter engineer confirmed both main rotor blades remained attached to the hub. One blade had two chordwise bends and a fractured, separated tip. Leading edges showed no evidence of high rotational energy damage; trailing edges and afterbodies exhibited multiple wrinkles along the span.