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N23428 accident description

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Tail numberN23428
Accident dateJune 03, 2003
Aircraft typeRobinson R-22 Beta
LocationMontpelier, VA
Near 37.787777 N, -77.720278 W
Additional details: None

NTSB description

HISTORY OF FLIGHT

On June 3, 2003, about 1103 eastern daylight time, a Robinson R-22 Beta helicopter, N23428, was substantially damaged when it collided with trees and terrain near Montpelier, Virginia. The commercial pilot and the passenger were fatally injured. No flight plan was filed for the flight that originated at Shannon Airport (EZF), Fredericksburg, Virginia, about 0925. Visual meteorological conditions prevailed for the aerial observation flight conducted under 14 CFR Part 91.

According to the operator, the purpose of the flight was to conduct power line inspections.

According to a witness, she was in her home, with the windows open, between 1000 and 1100, when she heard the helicopter approaching. It flew low over her property, then became "suddenly quiet," which intensified her attention. Immediately afterwards, she heard "two really loud bangs, like a hammer banging on metal," followed again by silence. The witness thought the helicopter had crashed, so she investigated the area around her back yard and peered into the heavily wooded area behind her home. She did not see smoke or any signs of the helicopter.

A second witness was in her yard with her husband, when she first observed the helicopter flying above the power lines. She commented to her husband that it seemed "kind of loud." The helicopter then flew out of her view, and shortly afterwards, she heard a "backfire". The witness and her husband went to the area where they last heard the helicopter, but did not see any smoke. The witness commented that, other than the loudness, nothing seemed unusual about the helicopter's flight.

A hand-held Global Positioning System (GPS) receiver was located near the main wreckage. Information downloaded from the receiver revealed that the entire flight was recorded.

The GPS began recording at 0937:34, and ended at 1102:52. A review of the last 23 seconds of recorded data revealed that the helicopter was headed 088 degrees, then initiated a left turn to a heading of 285 degrees. During that time, the helicopter decelerated from a ground speed of 30.4 knots to 3.6 knots, before the data ended.

The pilot and the passenger were scheduled to return to Shannon Airport around 1630-1700. When the helicopter did not return, the operator contacted search and rescue personnel, and a search was initiated.

The accident occurred during the hours of daylight approximately 37 degrees, 47 minutes north latitude, and 077 degrees, 43 minutes west longitude, which was also the last position recorded by the GPS on-board the helicopter.

PILOT INFORMATION

The pilot held a commercial pilot certificate for rotorcraft-helicopter. He also held a certified flight instructor certificate for rotorcraft-helicopter. The pilot's most recent Federal Aviation Administration (FAA) second-class medical certificate was issued on October 17, 2002.

A review of the pilot's logbook revealed he had a total of 417.6 flight hours, all of which were in helicopters, with 370 hours in R-22 Alpha and Beta models.

The "remarks" section of the pilot's logbook did not indicate any previous experience inspecting power lines.

AIRCRAFT INFORMATION

A weight and balance calculation was performed, using data provided by the medical examiner, and the airframe manufacturer. The maximum gross weight for the helicopter was 1,370 pounds.

At takeoff, the estimated gross weight of the helicopter was 1,485 pounds, with a center of gravity location of 96.78 inches.

At the time of the accident, the estimated gross weight of the helicopter was 1,382 pounds, with a center of gravity location of 95.92 inches.

Interpolation of the Allowable Helicopter Moment versus Gross Weight envelope chart, located in the Robinson R-22 Beta Pilot Operating Handbook (POH), page 6-8.1, indicated that the helicopter exceeded the allowable weight, and had a forward center of gravity at the time of take-off, and at the time of the accident.

METEOROLOGICAL INFORMATION

The weather at Hanover County Airport (OFP), Richmond/Ashland, Virginia, 14 miles southeast of the accident site, at 1054, was reported as variable winds at 6 knots, 10 statute miles visibility, a broken cloud layer at 6,000 feet and a barometric pressure setting of 30.00 inches Hg. The temperature was 68 degrees Fahrenheit, and the dewpoint was 57 degrees Fahrenheit.

WRECKAGE INFORMATION

The helicopter was located approximately 0800 the following day, in a heavily wooded area on private property, about 200 feet north of approximately 75-foot-high power lines.

Examination of the trees surrounding the main wreckage revealed impact scars to the tops of 2 or 3 standing trees. Located near the base of the trees, in the area just south of the main wreckage, were several pieces of angular cut wood (approximately 45-degrees), and they exhibited black transfer marks.

The helicopter wreckage was examined at the accident site on June 4-5, 2003. All major components were accounted for at the scene. The helicopter came to rest on its right side, oriented on a heading of 270 degrees magnetic, at an elevation of 230 feet mean sea level (msl).

The main wreckage, which consisted of the cockpit, engine, transmission, and approximately 5 feet of the tail boom, came to rest at the base of 80- to 100-foot trees.

The tail boom was separated into 5 sections. A 4-foot section of the tail boom (inboard section) was located in the fork of a tree, approximately 10 feet above the ground, and 10 feet east of the main wreckage. The tail rotor assembly was intact, and was located 21 feet east of the main wreckage. The gearbox and pitch links were intact and moved freely. The leading edges of both blades exhibited impact damage, and the tip of one of the blades was located 26 feet west of the main wreckage.

The other three sections of the tail boom were located east of the main wreckage. Examination of the tail boom sections revealed impact marks, consistent with the width of the main rotor blades. These impact marks also exhibited yellow transfer marks.

The tail rotor drive shaft and push/pull tube were fragmented, and scattered around the area east of the main wreckage.

Flight control continuity was established from the cockpit to each flight control surface. The collective was found in the full up position.

The main rotor assembly remained intact and attached to the fuselage. One of the main rotor blades was bent and displaced upward by the weight of the fuselage lying on its side. The blade appeared to be straight, and did not exhibit any leading edge or trailing edge damage.

The second main rotor blade was compressed aft and exhibited buckling along the length of the blade. There was no leading or trailing edge damage. The tip of the blade, which was painted yellow, exhibited red paint transfer.

The engine sustained some impact damage to the right side, but remained secured to its mounts. The spark plugs were removed, and appeared light gray in color except for the # 2 and #4 top plugs, which were oil-covered. Valve train continuity and compression were confirmed to each cylinder by manual rotation of the cooler fan. While the engine was being rotated, spark was produced to each ignition lead, except the #4 top lead, due to the harness being torn. The engine was rotated again, and spark was observed at the tear.

The oil pump suction screen was removed and found absent of debris. Oil on the screen was black in color. The oil pressure screen was not installed.

The starter ring gear was found imbedded 2-inches into the oil cooler .

A review of fueling records revealed that the helicopter was fueled with 15.2 gallons of 100 LL fuel on the morning of the accident, which filled the tanks. According to emergency personnel, the fuel selector was found in the "on" position. The firewall fuel strainer was intact, but was not safety wired. The strainer was disassembled and examined. The examination revealed that there was no fuel inside the strainer bowl, and the filter was absent of debris. The fuel line from the firewall fuel strainer to the carburetor was removed; there was no fuel in the line, and it was absent of debris.

The carburetor mixture control arm was in the full 'rich' position, and the throttle was near the mid-range position. The carburetor was removed and examined. The carburetor halves were then separated, and a small amount of light blue fuel was found in the bowl. The finger screen was absent of debris. No fuel was found in the accelerator pump chamber; however, a ring of rust-colored debris was found midway on the interior wall of the accelerator pump chamber. The accelerator pump plunger seal was covered with rust-colored debris, was worn, and the inner spring was exposed. A splattering of rust-colored material was also found on the mixture shaft and around the floats, which were intact and moved freely.

The carburetor was examined at the manufacturer's facility under the supervision of a Safety Board investigator. The carburetor was visually inspected for damage and none was found. The accident carburetor was installed on the test bench and fuel flow was applied measuring four settings from low idle to full throttle. It was noted that the flows on the two upper limits were lower than the allowable flow limits, indicating lean.

The carburetor was then disassembled and inspected. Evidence of rust and rust particles was noted throughout the system. The pump discharge check valve was found stuck in the open position. An attempt was made to disassemble the valve, however, the setscrew was seized in the body and would not come apart. Evidence of rust was noted. The accelerator pump plunger spring was corroded behind the leather seal. The seal was worn away in one section allowing the spring to wear on the bore. All other components of the carburetor were found within manufacturer specifications.

The main fuel tank was intact, but empty, and the cap was secure. The auxiliary fuel tank was removed and examined. The cap was secure, but the interior side of the tank was ruptured in several locations. Approximately 16 ounces of fuel was found in the bottom of the tank.

When the helicopter was righted back onto its skids, fuel drained from several underside locations. A sample of the fuel revealed that it was dark turquoise in color, and slightly opaque.

Transmission oil and tail rotor gearbox fluid were blue in color. The main rotor hub seeped bright red oil.

MEDICAL AND PATHOLOGICAL INFORMATION

An autopsy was performed on the pilot by the Virginia Medical Examiners Office, Richmond, Virginia.

Toxicological testing was completed by the FAA Toxicology Accident Research Laboratory, Oklahoma City, Oklahoma.

TESTS AND RESEARCH

The Low Rotor rpm annunciator light was examined at the Safety Board's Materials Laboratory, Washington, D.C. The examination revealed that the filament displayed significant stretching and deformation consistent with a hot impact.

ADDITIONAL INFORMATION

The Robinson R-22 Beta Pilot Operating Handbook (POH) Safety Notice #SN-10 stated that a primary cause of fatal accidents in light helicopters is failure to maintain rotor RPM. To avoid this pilots should have reflexes conditioned to be able to handle an emergency situation.

According to the FAA Rotorcraft Flying Handbook Page 11-10, "The danger of low rotor r.p.m. and blade stall is greatest in small helicopters with low blade inertia. When the rotor r.p.m. drops, the blades try to maintain the same amount of lift by increasing pitch. As the pitch increases, drag increases, which requires more power to keep the blades turning at the proper r.p.m., and therefore lift, the helicopter begins to descend. This changes the relative wind and further increases the angle of attack. At some point the blades will stall unless r.p.m. is restored. If all blades stall, it is almost impossible to get smooth air flowing across the blades."

The helicopter wreckage was released to the operator on August 3, 2003.

(c) 2009-2011 Lee C. Baker. For informational purposes only.