FTW97FA014
FTW97FA014

HISTORY OF FLIGHT

On October 10, 1996, about 0447 central daylight time, a Mbb BO-105 CBS-4 twin-engine helicopter, N299EH, owned and operated by ERA Aviation Inc., of Lake Charles, Louisiana, was destroyed after impacting brackish coastal marshland near Cameron, Louisiana. The airline transport rated pilot, who was the sole occupant, was fatally injured. Dark night visual meteorological conditions prevailed during the 14 Code of Federal Regulations Part 91 positioning flight. The flight originated from the company's Cameron helicopter base at 0443, and was en route to the company's main base at Lake Charles, Louisiana. At 0446, the pilot filed a company flight plan via radio.

According to company flight following records, the helicopter departed the Cameron field base at 0443 to reposition the aircraft to the Lake Charles base for maintenance (transmission replacement due to chip lights). Company flight following personnel reported that no radio/distress calls were received from the helicopter.

According to the operator, the following was the known chronology of events leading to the accident flight:

1730 (October 9th) The pilot reported for duty at the Lake Charles Base after being off duty for 12 days.

1900 (October 9th) Maintenance inspection performed (transmission) by Cameron Base personnel on N299EH.

2200 (October 9th) The pilot worked on a weight and balance report for N299EH.

2305 (October 9th) The pilot performed a maintenance ground run-up on N298EH.

2315 (October 9th) The pilot and other Lake Charles Base pilots were inside awaiting assignments.

0307 (October 10th) The pilot departed Lake Charles Base in N298EH on a repositioning flight to the Cameron Base to replace N299EH.

0323 The pilot arrived at Cameron Base in N298EH.

0332 The pilot performed a ground run-up on N299EH to leak-check the transmission. The ground run-up was reported "OK."

0343 Cameron Base maintenance personnel performed a final inspection on N299EH.

0443 The pilot departed Cameron Base in N299EH en route to Lake Charles Base.

0446 The pilot called his flight plan in to Lake Charles, reporting "ETA 0505, solo, one-hour fuel."

O505 No radio contact from N299EH. Company initiated a ramp search and commenced company search and rescue plan.

0703 Search aircraft, N167EH, located the wreckage of N299EH in the marsh, approximately 4 nautical miles on a magnetic bearing of 028 degrees from Cameron Base. GPS coordinates: North 29 degrees 50 minutes 33.5 seconds, West 93 degrees 15 minutes 08.2 seconds (bearing 199 degrees from Lake Charles VOR at 19.5 nautical miles).

PERSONNEL INFORMATION

The pilot held a Rotorcraft-Helicopter Airline Transport Pilot Certificate for BH-206, BH-212, and BO-105 type helicopters, with commercial ratings in Single and Multi-Engine Land, Instrument Airplane, and CFI Rotorcraft-Helicopter. His current Class I FAA medical certificate, dated July 1, 1996, had a limitation for eyeglasses to be worn for near vision correction. He was employed with ERA since January 8, 1981. His total accumulated flight time was 11,897 hours, of which 2,053 hours were flown in the BO-105 helicopter. His total accumulated night helicopter time was 316 hours, of which 28 hours were flown in the 90 days prior to the accident. The pilot's total instrument time was 446 hours, of which 142 hours were flown in actual instrument conditions. His total flight time experience in Gulf of Mexico flight operations was over 6,700 hours. Additionally, he had been a FAA designated company check airman since 1984.

According to company records, the pilot's last annual re-qualification in the BO-105 was satisfactorily demonstrated on June 13, 1996.

At the request of the NTSB investigator-in-charge, the operator's Director of Safety collected human factor issues/information that he retrieved from friends, family members, and work associates of the pilot during the course of the investigation. He listed them categorically in a written report. Excepts of the report are listed below:

Fatigue and Circadian Rhythm - The pilot had been on vacation for two weeks from September 26 to October 8, and spent that time with his family and friends in Arizona. During the vacation, the pilot was on a normal day/night sleep cycle and was sleeping about 9-10 hours per night. On the day prior to the accident, the pilot awoke in the morning when his wife went to work. According to his wife, he took a nap for about 2 hours during the day and called her at work when he awoke. The pilot did not sleep during the night prior to the accident, apparently due to the workload in helping base maintenance personnel with aircraft run-ups. According to personnel who worked with the pilot, he normally tried to get some sleep during the night shift. The accident flight was conducted during the 11th and 12th hours of the pilot's 12-hour night shift.

Situational Awareness - The pilot's co-pilot for the Bell 412 standby aircraft stated that the pilot was "very good" at night flying, always followed the checklist and briefed on what he was preparing to do. Another pilot interviewed stated that he had to take the controls from the pilot several years ago because the pilot was descending too low during an approach to an offshore platform. According to the operator, it would be a normal reaction by a helicopter pilot during daylight hours to fly lower than normal altitude if he suspected, or was concerned about a possible mechanical problem. According to the operator, a typical normal altitude for this flight would have been about 1,000-1,500 feet AGL. The pilot may have elected to remain at a lower than normal altitude in the event the transmission (which was recently worked on) developed a problem. This would allow the pilot to get the aircraft on the ground sooner if necessary, but would also allow for less time for the pilot to notice a slow, undetected descent.

Night Visual Effects - The helicopter was parked on a pad near an overhead, high intensity yard light. While waiting for the transmission maintenance to be completed, the pilot was in the base office. Upon the completion of maintenance, the pilot went directly from the lighted office to the lighted parking pad, performed a pre-flight, and departed. The average pilot requires about 30-45 minutes in a reduced light or dark environment for effective "dark adaptation" prior to dark night flying. According to the operator, if the pilot had elected to remain at a lower than normal altitude, he may have had some difficulty in correctly determining his altitude above an area that had little or no ground lights and a vast expanse of swamp and marsh along the flight path from Cameron to Lake Charles. Additionally, altitude and sink rates can be difficult to judge during dark night flights conducted over unlighted terrain when the lights of a city (Lake Charles) are in the distance ("Black Hole Effect"). According to the operator, this is especially true in the BO-105 helicopter, as slow descents and climbs are typically not "felt" by the pilot.

AIRCRAFT INFORMATION

The 1989 model MBB BO-105 CBS-4 helicopter, serial number S-807, had an airframe total time since new (TTSN) of 4,545.8 hours. The helicopter was equipped with two Allison 250-C20B turbo-shaft engines. Engine #1 had 4,254.5 hours total time since new, and 2,164.1 hours since its last major overhaul. Engine #2 had 9,567.5 hours total time since new, and 2,164.1 hours since its last major overhaul. The helicopter did not have a radar altimeter or GPWS installed.

The helicopter was being maintained in accordance with the ERA Approved Aircraft Inspection Program (AAIP). The program contains a Daily Service Check (DSC), a 50-hour Preventative Maintenance Inspection (PMI), a series of 5 separate phase inspections conducted 150 hours apart, a 2,500 hour major airframe inspection, and "additional" maintenance items that are stand alone inspections. The descriptions and details of the inspection program are contained in the ERA maintenance manual, which is FAA approved.

A detailed review of the aircraft's maintenance records indicated that all of the inspections required by the AAIP had been performed. Airworthiness Directive (AD) compliance was verified through maintenance record review and visual inspection of the applicable items on the aircraft (during wreckage examination). Compliance with all pertinent AD's was verified. Further review of the maintenance records did not reveal evidence of any uncorrected defects or anomalies. The following is a chronology of the most recent maintenance performed prior to the accident:

October 10, 1996 - Removal of the left and right transmission input pinions for transmission service and inspection for transmission chip light occurrences.

October 8, 1996 - Scheduled "A" check in accordance with the AAIP. No uncorrected defects found, and returned to service.

July 20, 1996 - Hydraulic unit switch-over check performed in compliance with FAA Airworthiness Directive (AD) 96-08-04. No uncorrected defects found, and returned to service.

METEOROLOGICAL INFORMATION

Lake Charles base, located about 19 miles north of the accident site, reported clear skies, winds from 260 degrees at 3 knots, temperature 55 degrees F, dew point 55 degrees F.

Cameron base, located about 4 miles south of the accident site, reported clear skies, winds from 280 degrees at 3 knots, temperature 64 degrees F, dew point 63 degrees F.

Company personnel at the Cameron base reported that it was a "clear, dark night" at the time the helicopter departed the base.

WRECKAGE AND IMPACT INFORMATION

The accident site was located in coastal marshland with dense vegetation laced with shallow inland canals approximately 4 nautical miles north of the Cameron base. The wreckage was found severely fragmented along a 300-foot long energy path bearing about 003 degrees magnetic. The site had a persistent fuel odor. The initial ground contact was evidenced by shallow angled skid marks that gradually deepened into the soft marsh. The next feature was the two main skid assembly tubes found separated from the fuselage-mounted crosstubes and embedded into the ground at nearly a 90-degree angle. Physical evidence was consistent with the impact being at a relatively flat angle and high speed, as evidenced by well-defined ground impressions along the energy path. Five distinct impressions, corresponding to the main fuselage "tumbling" across the marsh surface after separating from the skid assembly, were found at 41 feet, 61 feet, 86 feet, 107 feet, and 128 feet respectively along the debris path.

The main fuselage and cabin section was found crushed and distorted about 225 feet down the path, resting on its left side, and partially submerged in a canal. Both left and right hinged (crew) and sliding (passenger) doors were separated from the fuselage. The main transmission was completely separated from the fuselage. All four transmission mounts were fractured in overload and the transmission deck was collapsed downward along with the transmission, rotor mast and head, and turbine deck. Main rotor blade pitch link positions indicated a collective position in the range of normal to flat pitch. The tandem hydraulic unit (THU) was intact and found to be in the #1 system (normal) position. Both engines were found on the turbine deck in their normal positions. The throttle was found in the "full" open position The tail boom was found about 81 feet forward of the main fuselage, separated from the tail boom mounting flange. All four main rotor blades were found fractured and separated from the blade roots. The blades were found scattered away from the energy path from 50 feet to 230 feet from the initial impact point.

Due to the adverse terrain (chest deep water and dense vegetation) conditions, the on-site investigation was limited to general examination of the wreckage. All major components of the helicopter to include the main rotor blades, hub assembly, fuselage, tail rotor drive shaft, flight controls, engines, skid assembly, and airframe cowlings/fittings/windscreens were found within the debris area. There was no evidence of an in-flight breakup or an in-flight collision with an object. On October 12th, the wreckage was recovered to the operator's hangar facility in Lake Charles for an airframe layout and further detailed examination of components. During the layout, deformation signatures showed evidence that the aircraft impacted the terrain at a shallow angle with significant forward momentum. The instrument panel and warning light clusters were packaged and shipped to the NTSB Materials Laboratory in Washington, DC, for light bulb analysis. The THU was bench tested at the hangar and then shipped to the manufacturer in Germany for operational validation and load testing. The engines were packaged and shipped to Dallas Airmotive, Dallas, Texas, for teardown inspection. The following facts are presented as they were discovered during the examination of the wreckage at the hangar and during the teardown inspections/tests.

The free wheeling units of the input stages of the main transmission were intact. However, the main transmission could not be rotated so transmission disassembly was required to verify drive train continuity. The transmission housing case (magnesium) showed evidence of corrosion as a result of being submerged in the brackish water. Upon opening the case, all gears were found in-mesh and void of visible damage, with the exception of corrosion. Nothing abnormal was found on both engine to transmission input pinions. The transmission oil pump was found free of debris and the outside of the inlet screen was coated with corrosion by products and a ferrous sliver was found (with a magnet) on the outside. The origin of this small metal sliver could not be detected. The operator's mechanics stated that the sliver might have come from the re-assembly of the input pinions before the accident. However, such a small sliver would not induce a malfunction of the main transmission, since it was captured by the inlet screen. The oil filter screens of the airframe mounted transmission oil filter were free of unusual debris. The bowl was filled with relatively clean oil.

Each of the four main rotor blades (MRBs) were heavily damaged. According to the manufacturer, the MRBs exhibited damage signatures typical of ground or water contact at full rotor RPM.

The tail boom structure was fractured and torn around its circumference just aft of the flange ring attachment point to the fuselage. The skin above and below the fracture showed "up and down" buckling. The lower portions of both vertical stabilizers were displaced to the left and slightly aft. The tail skid was not deformed. The tail rotor drive shaft was separated at the #1 Thomas coupling. The coupling plates were splayed and showed evidence of torsion. The shaft showed bending along its length and was fractured in overload just aft of the #1 bearing, adjacent to the area of the tail boom separation from the fuselage. Continuity was established from the aft portion of the shaft to the intermediate (45 degree) gearbox, through the 90 degree gearbox, and into the tail rotor hub and blade assembly. The tail rotor blades were intact with evidence of grazing strikes on their tips. The 90 degree gearbox was mounted on the fin and freely turned with continuity from the input to output sides, and its chip detector was clean. The intermediate gearbox was undamaged and free to move and continuity was established from input to output sides.

The main and tail rotor flight control rods were separated in several locations between the cockpit controls and the THU. The separations exhibited evidence of overload forces during the impact. The grip of the pilot's cyclic lever was bent to the left and the friction brake setting on the collective lever was "loose" (fully turned counter-clockwise to the stop). The boosted control rods (lateral and longitudinal) from the THU to the mixing lever assembly were fractured in tension. The boosted control rod for the collective was fractured in compression. The rotating swashplate moved freely and the scissors assembly was properly attached and not damaged.

The cyclic trim actuators were found in the following positions (extension of the rod from the flange of the housing to the center of the clevis of the rod end):

Longitudinal - 92mm Lateral - 88mm

According to manufacturer's specifications, the actuator measurements correspond to a cyclic stick position of about 2.7cm forward and 0.5cm to the left of neutral, which corresponds to the trim setting for hover flight.

The THU, serial number 2015-923/960 was found at the accident site in the #1 system position, which is the normal working system. The dual system is designed so that if the #1 system fails, the #2 system picks up the hydraulic load and normal flight can be continued. The two systems are mechanically connected through a selector valve and a connecting link. The connecting link ("black link") was found fitted and attached between the selector valves. Measurements of the link revealed that the bore-to-bore length was 25.05 mm. The manufacturer's specified value is 25.1 mm. The three flight control connecting rods at the front of the unit were essentially undamaged and the actuators and control valves could be moved. All 3 axes were movable, the mechanism of the control sliders functioned properly and the micro-switches clicked when overridden.

A functional bench test of the THU (without load simulation) was accomplished with an external pressure supply from a ground trolley. The return flow was dumped into a waste basket in order to "safe" the trolley, as the fluid was contaminated with water. The THU functioned properly, with the exception of the lateral axis being a bit "jerky." This was traced to a binding bearing of the lower coupling rod end, which was slightly corroded from being submerged in the brackish water. After some movement of the rod and lubrication of the bearing, the system functioned smoothly throughout the entire control range of each axis. Manual switch-over from the #1 to the #2 system functioned without delay. After the bench test the unit was shipped to the manufacturer in Germany for functional load testing. The test took place on November 13, 1996, at Ottobrunn, Germany. The THU functioned normally under normal flight loads and no negative influence of the slightly out-of-tolerance connecting link could be detected during testing.

Examination of the #1 engine (left airframe position), serial number CAE-836258, revealed evidence indicating that both compressor and turbine sections were rotating at the time of impact. Both N1 and N2 drive lines turned freely prior to disassembly. Debris (mud and grass) was found throughout the entire airflow path. All six axial stage compressor stages showed rotational damage with pronounced blade tip bending opposite the direction of rotation. Compressor rotor and vane tips showed rubbing in all stages and the compressor shroud assembly showed rubbing in an axial direction. There was light to moderate blade tip rub along the #4 turbine wheel blade path. The #2 engine, serial number, CAE-835470, showed similar characteristics of rotation with the exception of the compressor section, which had minor FOD damage throughout the six stages. Both engines exhibited characteristics of sudden stoppage, i.e., rotating-to-stationary contact marks within the internal rotating sections.

MEDICAL AND PATHOLOGICAL INFORMATION

An autopsy performed on the pilot indicated that the cause of death was attributed to multiple injuries sustained, with no evidence of pre-impact injuries or natural disease. Toxicology tests revealed low levels (less than .003mg/ml) of Chlorpheniramine (a sedating antihistamine) detected in blood and urine. According to the CAMI pathologist who conducted the toxicology tests, the underlying medical condition for which the antihistamine was taken may have caused a discomfort of distraction in the cockpit.

TESTS AND RESEARCH

The humidity in southern Louisiana can be extremely high during summer and fall, and is compounded during the night hours. According to the operator, the normal procedure to prevent moisture buildup in the aircraft and on the windscreens, was to install a small ceramic heater during the night hours. The accident aircraft did not have the heaters installed during the night. Personnel at the Cameron base reported that on the night of the accident, it was "very wet" and the windscreens had "a lot of condensation" on them while work was being performed on the helicopter. No one could confirm if the windscreens were still that way when the pilot departed Cameron; however, a pilot stationed at the base stated that, after pre-flight "you have to use a rag to dry the windscreens if it is real wet."

Mechanics at the Cameron base remarked that the mosquitoes were so bad that the pilot "spayed the inside of the cockpit with a lot of bug repellant" prior to departure. In a test, the NTSB investigator-in-charge parked his car near the Cameron base during early morning hours. The windows of the car became completely fogged and wetted and the mosquitoes were swarming. After spraying the inside of the car with bug repellant, the windows were wiped with a rag. The result was a smearing effect with the water and bug repellant on the window. Considerable effort and repeated cleaning was required to clear the smears and maintain the windows dry.

Filament analysis of the bulbs in the master caution cluster revealed that no filaments were found stretched.

ADDITIONAL INFORMATION

The wreckage was released to the operator at the conclusion of the field investigation.

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