Accident Details
On December 31, 2014, about 1330 Pacific standard time, an MD Helicopter Inc. 369FF, registration N530KK, was substantially damaged during an emergency autorotation landing following a sudden loss of engine power. The accident occurred in Las Vegas, Nevada. The two commercial pilots on board sustained serious injuries. The helicopter was registered to and operated by the Las Vegas Metropolitan Police Department as a public aircraft flight. Visual meteorological conditions prevailed, and no flight plan was filed. The local flight originated from North Las Vegas Airport (VGT) at 1322.
The pilot reported that after takeoff with 64 gallons of fuel, while orbiting over a fixed location, he noticed a drop in engine and rotor rpm. After rolling out of the orbit, engine and rotor rpm stabilized momentarily at 97%. While turning west toward North Las Vegas Airport and attempting to increase rpm, the engine and rotor rpm rapidly degraded. The pilot entered an autorotation and executed an emergency landing. The helicopter touched down hard; the tail impacted the ground and separated from the airframe.
Examination Findings
On-scene examination by an FAA inspector revealed that only one side of the engine was visible due to the helicopter's position; no unusual findings were noted. Flight controls were connected. The helicopter was recovered to the Las Vegas Metro Police Department's hangar at North Las Vegas Airport.
On January 7, 2015, two FAA inspectors examined the helicopter and reported impact damage to the engine outer combustion chamber, external fuel line connected to the fuel nozzle, and the fuel nozzle connection. The engine fuel nozzle b-nut was "finger tight."
On January 14, 2015, representatives from MD Helicopters and Rolls-Royce examined the helicopter with FAA oversight. Substantial damage was noted to the lower fuselage structure, aft fuselage section, tailboom, and landing gear. The main structural members of the fuselage and the transmission/static mast support structure were undamaged. The aft cabin was intact. The belly skin and supporting interior structure were damaged, with major damage to the aft landing gear fitting and center beam.
The top aft surface of the composite engine air fairing showed evidence of main rotor blade contact, and the tailboom was severed into two segments. The forward segment remained attached to the upper aft boom fairing. The vertical and horizontal stabilizers were attached to the aft segment; the vertical stabilizer's stinger was broken off, and both stabilizers displayed impact damage. The left and right landing gear struts were broken and splayed outward.
Cyclic and collective control continuity was verified. Tail rotor control damage corresponded with tailboom damage. Tail rotor blades exhibited impact damage with bent spars or tears. Main rotor blade damage varied and included bending, chordwise wrinkling, leading/trailing edge and tip cap damage; one blade was fractured near the root fitting. Drive system continuity was verified. Main rotor hub assembly showed damage consistent with excessive blade flapping and lead-lag excursions from sudden stoppage at low rotor rpm without engine power.
Fuel cells were near full with no reported spillage. A vacuum check from the fuel inlet line to the fuel shut off valve was satisfactory. Fuel cells were drained and appeared undamaged; fuel was visually clean. No contamination or blockage was found in the fuel inlet ports or sump. Fuel line plumbing and fittings showed no damage or discrepancies.
Engine Testing
Visual inspection of the engine and related systems found only minimal external damage, with impact damage to the outer combustor case, fuel nozzle, and fuel line. The fuel nozzle had been cleaned just prior to the accident flight, and the fuel line was reported loose at the accident site but also exhibited impact damage. The engine manufacturer reported that past experience showed b-nuts not fully torqued on the fuel nozzle may not affect normal operation, and properly torqued b-nuts do not come loose under normal conditions.
No obvious evidence of fuel leakage was found in the engine area. Engine mounts showed bent aft legs; left and right side mounts were undamaged. Contact marks on the firewall indicated engine movement during the crash. The engine trim switch was functional. Some pneumatic and fuel line b-nuts had broken or misaligned torque paint. Air, fuel, and oil lines were at least hand tight. Throttle and governor controls showed no discrepancies. The engine was removed for further testing.
On January 20, 2015, examination and functional testing of the engine was conducted at Aeromaritime America Inc. Representative from airframe and engine manufacturers were present with FAA oversight. The damaged outer combustion case, combustion liner, and fuel nozzle were replaced with serviceable items. No other fuel or pneumatic lines were altered except the fuel line to the nozzle and the fuel supply line at the fuel control. The engine ran in the test cell with no operational discrepancies and produced rated power. After the test, a pneumatic leak check revealed a small bubble formation at the Pg accumulator line connection, indicating a leak. The line was tightened with wrenches and the leak stopped. All other lines had torque of 65 inch-pounds or greater.
Two external fuel lines were examined: one with orange fire sleeve from engine to firewall, and a black hose from firewall to fuel shutoff valve. Examination via borescope and sectioning found no anomalies. The fuel filter was clear of debris.
Fuel Analysis
A fuel sample from the line between the firewall and shutoff valve was clear with a petroleum odor and a small amount of white particulate sediment. Analysis by third party using ASTM D2887 showed distillation results consistent with Jet-A. The particulates were tested using ASTM D5185; elements found (sodium 82.8 mg/kg, zinc 4.9 mg/kg, iron 5.4 mg/kg, magnesium 6.7 mg/kg) are commonly occurring, including in soil.
The helicopter's most recent weight and balance (April 3, 2014) showed empty weight 1975.22 pounds. At accident time, gross weight was 2,810 lbs, within published limits. Maintenance records indicated a 100-hour airframe and engine inspection was completed on December 31st but had not been signed off before the pilots took the helicopter.