CEN09TA060
CEN09TA060

HISTORY OF FLIGHT

On November 16, 2008, at 0028 Central Standard Time, a Bell OH-58C, N153GF, sustained substantial damage when it landed hard in a field near Quitman, Arkansas. The commercial rated pilot was not injured and the passenger was fatally injured. The helicopter was registered to and operated by the Arkansas Game and Fish Commission. No flight plan was filed and night visual meteorological conditions prevailed for the Public Use flight conducted under 14 Code of Federal Regulations Part 91. The flight originated from the Heber Springs Municipal Airport (HBR), Heber Springs, Arkansas at 1130.

The purpose of the night surveillance flight was to support ground personnel to apprehend "spot-lighters" who were illegally hunting deer at night.

The pilot was wearing night vision goggles (NVGs) while operating over a large open field approximately 150-feet above ground level (agl) on a westerly heading at 10 knots. The pilot stated, "I suddenly noticed a master caution, low rotor lights, a low rotor audio, and a sinking of the aircraft. I initially glanced in and noticed a decaying of the N2/Rotor tach. I immediately lowered the collective and landed straight down."

METEOROLOGICAL CONDITIONS

Weather reported at Adams Field Airport (LIT), Little Rock, Arkansas, at 0053, was reported as wind from 250 degrees at 8 knots, visibility 10 statute miles, clear skies, temperature 01 degrees Celsius, dew point 03 degrees Celsius, and a barometric pressure setting of 30.32 inches of Mercury.

PILOT INFORMATION

The 29 year old pilot held a commercial pilot certificate for airplane single and multi-engine land, and instrument airplane. He also held a commercial pilot certificate for rotorcraft-helicopter and instrument helicopter issued March 31, 2008. His last Federal Aviation Administration (FAA) first class medical with no limitations was issued on January 10, 2008.

The pilot reported a total of 3,602 hours in all aircraft of which 1,727 hours were in helicopters. The pilot had 332 total hours in the OH-58C of which 270 hours were as pilot-in-command. He had flown 159 hours in helicopters in the last 90 days of which 39 hours were in the OH-58C. He had flown 66 hours in helicopters in the last 30 days of which 30 hours were in the OH-58C.

The pilot also reported a total of 1,005 hours at night of which 765 hours were as pilot-in-command, and 96 hours were in the OH-58C. He flew 73 hours at night in the last 90 days and 21 hours in the last 30 days.

According to the FAA, the pilot flew for the Arkansas Air National Guard and had signed a contract with the Arkansas Game and Fish Commission to assist on missions during deer season, which started two weeks prior to the accident. The pilot reported a total of 3,500 hours, of which, 300 hours were in the same make and model as the accident helicopter.

WRECKAGE INFORMATION

Examination of the accident site revealed the helicopter impacted the ground in a nose low, left bank attitude. The helicopter remained upright, the tail boom was deflected down and was partially separated from the airframe forward of the horizontal fins, and the left front side of the cockpit exhibited impact damage from contact with the main rotor blades.

The helicopter was recovered to a salvage facility and examined.

Examination of the airframe and fuel system revealed there were not mechanical deficiencies. Flight control continuity was established for all major flight controls to the cockpit.

The Gas Producer (N1) and Power Turbine (N2) tachometer generators were removed from the accessory gearbox with the electrical leads attached and tested/spun via a hand drill. During the test, movement was noted to both the N1 and N2 tachometers. The rotor tachometer, which was mounted on the rotor transmission, had sustained damage during the impact sequence and could not be tested.

The engine was removed from the airframe and sent to Premier Turbines in Neosho, Missouri, where it was examined/test-run under the supervision of the FAA on December 18, 2008.

According to the Rolls Royce Final Engine Investigation Report, the engine was removed from the shipping container and installed in a turnover stand for a receiving inspection. The magnetic chip detector plugs were clean and a pressurized pneumatic leak check detected no leaks. The primary and secondary orifices of the fuel nozzle were absent of debris and the air shroud contained a normal amount of carbon accumulation. Approximately 250cc of oil was drained from the accessory gearbox and appeared normal in color and consistency. A borescope was used to inspect the first and third stage turbine areas with no impact damage or anomalies noted.

Impact damage was noted on the event compressor, so it was removed from the engine for a disassembly inspection. The engine was prepared to run on a calibrated test stand with a "slave" compressor provided by Premier Turbines. The engine test was conducted using a serviceable slave compressor. Once the engine was running, an oil leak was noted near the #6 and #7 oil sump can. This component exhibited external impact damage incurred during the accident sequence. Due to the oil leak, an abbreviated test run was conducted. During the test, the engine met power requirements for max continuous and take-off (intermediate) power. The specific compressor efficiency of the slave unit was unknown; however, the unit was serviceable and had been used to test overhauled modules for serviceable release to the field.

The event compressor was disassembled and examined. The compressor front support was buckled inward from the 12 o'clock to the 4 o'clock position. The compressor scroll was dented at the left elbow location consistent with an external crushing force. All of the compressor and stator airfoils were intact with some impact damage noted on the first stage rotor blades. Tip rub was noted on the first, second, fifth, and sixth stage vanes with corresponding witness marks on the compressor rotor seals. Rotational witness marks were noted on the compressor impeller blade leading edges and impeller shroud as well as the rear face of the impeller and forward portion of the compressor rear support. These signatures were consistent with the compressor rotating at the time of impact.

The engine examination and limited test-run on a Rolls Royce approved test stand using a slave compressor did not reveal any deficiencies that would have prevented the engine from producing power at the time of the accident.

ADDITIONAL INFORMATION

According to the OH-58 Flight Training Guide, section 9-10, the procedure for ENGINE FAILURE – HOVER is:

1.) Autorotate

Section 4-50 (task 1082), Perform Autorotation, it states:

“A steady-state autorotation means that-
a) Rotor RPM is within limits
b) The aircraft is at the correct speed
c) The aircraft is descending at a normal rate
d) The aircraft is in a position to terminate in the intended landing area.

“At approximately 50 feet agl, the pilot will apply aft cyclic to initiate a smooth, progressive deceleration. The pilot will maintain aircraft alignment with the touchdown area by properly applying the cyclic. The pilot will adjust the collective, as required, to prevent excessive rotor RPM. At approximately 10 feet agl, the pilot will apply sufficient collective to minimize the rate of descent and the ground speed. The amount the collective applied and the rate of the application will depend on the rate of the descent and the ground speed. The pilot will adjust the cyclic to attain a level landing attitude and, before touchdown, apply collective as necessary to cushion the landing. After touchdown, the pilot will slowly lower the collective to the full-down position while maintaining ground track alignment with the pedals. When the aircraft comes to a complete stop, the pilot will neutralize the pedals and the cyclic.”

“NIGHT or NVG CONSIDERATIONS: Attitude control is critical during night autorotations. Reduced visual reference at night limits the aviator’s ability to estimate airspeed, altitude, and alignment with the touchdown area. To compensate for the reduced visual references, the aviator will attain a steady-state autorotation before descending through 200n feet agl. Selecting ground references that provide high visual contrast or that are of a known height in the vicinity of the touchdown area will help in judging the approach. If the searchlight or landing light is used, it should be turned on before descending through 100 feet agl.”

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