Accident Overview
On December 22, 2008, at 1604 eastern standard time, a Bell 407 helicopter, registration N407GB, operated by JBI Helicopter Services, was substantially damaged during a forced landing in Bow, New Hampshire. The certificated commercial pilot sustained serious injuries. Visual meteorological conditions prevailed, and the helicopter was operating on a company visual flight rules flight plan from Danielson Airport (LZD), Danielson, Connecticut, to Brigham Heliport (NH33), Pembroke, New Hampshire, as a positioning flight under 14 CFR Part 91.
Pre-Accident Events
According to the operator, the helicopter departed Pembroke on December 18 around 1200, picked up a passenger in Somerville, Massachusetts, and continued to Old Lyme, Connecticut. Approximately 3 miles from Old Lyme, weather deteriorated with falling snow reducing visibility to about 2 miles. After dropping off the passenger, the pilot began the return but due to weather landed at an en route heliport for the night. The next day, the pilot flew to Danielson but again decided to wait for better weather. The following two days, weather remained questionable and the pilot did not fly.
On the accident day, the director of maintenance and the accident pilot drove to Danielson. Upon arrival, areas of the helicopter where the sun shone were free of snow and ice; other areas were brushed off, and any remaining ice was removed with isopropyl alcohol. Windshield washer fluid was also tried but was less effective. Total ice removal took about 4.5 to 5 hours, including a thorough preflight inspection. After cleaning, the pilot started the helicopter, completed a ground run verifying normal systems, then shut down and performed another preflight. A second start followed, and the helicopter was taxied to fuel. After taking on approximately 60 gallons, the pilot started again and hover-taxied to verify systems.
The Accident Flight
The helicopter departed Danielson at 1518. About 3.5 miles southwest of Pembroke, at 1,400 feet above mean sea level, the Rolls Royce 250-C47B engine experienced an uncommanded shutdown. GPS data indicated the helicopter was over tree-covered terrain, then completed an approximately 180-degree autorotation to a curved, tree-lined street, landing on an estimated heading of 150 degrees magnetic at about 500 feet elevation.
Weather reported at an airport 3 miles north at 1551 included clear skies, visibility 10 statute miles, winds from 280 degrees true at 13 knots gusting to 24 knots, temperature -7°C, dew point -15°C, and altimeter 29.84 inHg. Prior to the shutdown, the pilot observed no caution or warning lights, the FADEC remained in automatic mode, and no unusual noises or yawing were noted.
Post-Accident Examination
FAA inspectors from the Portland Flight Standards District Office examined the helicopter on scene. An insurance company investigator (who also owned a helicopter company) participated and produced a written report. No obvious fuel or oil leaks were found. Total fuel onboard was 439 pounds, with 201 pounds in the auxiliary tank. The fuel shut-off valve was closed, but local fire personnel reported they had shut it off. The main fuel filter had fuel with no contamination and bypass not activated. Fuel pressure was confirmed on both boost pumps. The engine was motorized and fuel reached the nozzle.
The Combined Engine Filter Assembly showed no evidence of bypass. No unburned fuel or fuel droplets were in the soot aft of the exhaust. No obstructions or debris in the particle separator; snow baffles properly placed. The pilot’s throttle was in the FLY position. When powered up, FADEC caution lights indicated “Restart Fault” and “FADEC Degraded,” consistent with engine spooling down with throttle in FLY. The FADEC maintenance section recorded only an “open metering valve warning,” consistent with shutdown or power removal with N1 speed or throttle open.
The operator noted heavy undercarriage damage and the tail boom bent upward, consistent with stinger contact at impact. The helicopter was moved to the insurance investigator’s facility.
Engine and Fuel System Tests
A Rolls Royce representative found three triggers in the Incident Recorder: Engine Flameout Detected, Nr Droop Detected, and Ng Exceedance Low Detected. When flameout occurred, Fuel Enable and Auto Relight became active. ECU memory download showed no FADEC system faults.
On January 21, 2009, a general examination under NTSB oversight confirmed tail rotor and main rotor drive continuity. The electrical system energized via battery indicated 450 pounds of fuel; boost pumps showed pressures in the green band. Throttle rotation from off to idle to full on confirmed proper HMU rigging. Upon reexamination, small particles were found in the main fuel filter canister and filter paper folds; some very small metallic particles (non-magnetic) were captured in a coffee filter.
On March 3, 2009, the engine was test run at Rolls Royce under NTSB oversight. After warm-up, it performed accelerations and decelerations within production standards, then passed a five-point calibration check meeting or exceeding specification power. The engine was shut down normally. It was restarted for ECU overspeed testing; the overspeed switch was engaged and the engine continued running normally. A shutoff solenoid was attached to the fuel line; when activated, the engine shut down. Except for rotor rpm, IR data matched the accident flight.
On March 17, 2009, the helicopter fuel system was examined under FAA oversight. The FAA inspector did not provide results, but Rolls Royce and operator representatives reported main and auxiliary fuel cells clean and debris-free. Forward and rear boost pumps were removed and functionally checked; both operational. The “B” nut securing the pressure line on the forward pump was cracked, but the remaining fuel would have covered it.
A Bell Helicopter representative noted magnetic metallic debris in a check valve found stuck open, but stated neither the debris nor the cracked nut would have caused the shutdown. All fuel lines were examined with no anomalies. The fuel shutoff solenoid was cycled repeatedly with no discrepancies.
On June 11, 2009, the investigative team examined the HMU and ECU at Goodrich Pump and Engine Controls (GPECS). The ECU underwent environmental stress screening (5 minutes vibration, nine thermal cycles) and all testing passed except torque sensor input accuracy during temperature testing. HMU electrical checks were normal; fuel flow schedules in automatic and manual modes were within new-unit limits. A complete acceptance test showed test points within limits. The pump and metering unit were disassembled with no unusual wear, contamination, or anomalies.
Probable Cause
No probable cause was stated in the source.