History of Flight
On September 16, 2010, about 1330 Pacific daylight time, a Robinson Helicopter Company R44 II, N2153S, collided with terrain and rolled over during an emergency landing near Mammoth, California. The pilot was operating under Title 14 Code of Federal Regulations Part 91. The certificated private pilot and passenger sustained serious injuries; the helicopter sustained substantial damage. The cross-country flight departed Eastern Sierra Regional Airport, Bishop, California, about 1300, with a planned destination of Truckee-Tahoe Airport, Truckee, California. Visual meteorological conditions prevailed; no flight plan was filed.
The pilot reported departing Benson, Arizona, at 0600 that day. He had serviced the helicopter with 100 LL aviation gasoline the day prior and filled the tanks that morning. After about 2.5 hours, the low fuel warning indicator illuminated about 5 miles from Lake Havasu. He made a straight-in approach and at 0907 serviced with 45.9 gallons of fuel. The airport manager reported the pilot declared a fuel emergency over UNICOM. The pilot noted higher fuel consumption and elected to stop at Jean, Nevada, where he added 14.86 gallons. At Bishop, they added 26.42 gallons and ate lunch.
About 30 minutes after takeoff at 8,500 feet msl, the pilot experienced stomach cramps and landed at 8,600 feet in a meadow on Glass Mountain. Winds were calm. He applied control friction locks, asked the passenger to monitor controls, and exited with the engine running. After relieving himself, he re-entered and prepared for departure.
He raised into a 2-3 foot hover, rotated left, and initiated a downhill departure. At about 10 knots, the auxiliary fuel pump warning indicator illuminated with a simultaneous reduction in rotor rpm. He lowered the collective and raised the nose for a run-on landing. The skids contacted the ground; the helicopter tipped forward and rolled right in a manner consistent with dynamic rollover. Main rotor blades struck the ground; the cabin became engulfed in fuel and fire. The pilot extricated himself and assisted the passenger; both were partially engulfed in flames. A surge of flames re-ignited them. He extinguished the passenger's flames and secured her upwind.
An ALNOT was issued. A hiker reported fire at 1412; a fire truck dispatched saw no indications. At 1430 the pilot saw a truck on a ridgeline but was not seen. He left the site and after walking 10 miles reached a campsite at 2130 and summoned help.
Pilot Information
The pilot held a private pilot certificate with rotorcraft-helicopter rating. His flight logbooks were destroyed in the fire. He estimated 250 total flight hours. He participated in an RHC safety refresher in December 2008; at that time he reported 80 total hours, 60 in the R44. His evaluation indicated above average performance for simulated engine out, average for low rpm recovery, settling with power, autorotations, overall handling, and knowledge; below average for hovering autorotations.
Aircraft Information
The helicopter was manufactured in November 2002, with its original Lycoming IO-540-AE1A5 engine. Maintenance logs showed an annual inspection on February 11, 2011, at 728.9 flight hours. The last maintenance was an oil and filter change by the pilot at 775 hours on the day prior. Fire damage precluded exact total time. The helicopter had interconnected main and auxiliary fuel tanks with total capacity 50.1 gallons, 48.9 usable.
Meteorological Information
Mammoth Yosemite Airport AWOS-3 at 1329 reported wind 110 degrees at 10 knots, visibility 10 miles, clear skies, temperature 25°C, dew point -8°C, altimeter 30.23 inches. Bishop Airport ASOS at 1256 reported wind 170 degrees at 11 knots gusting to 18, visibility 10 miles, clear, temperature 32°C, dew point -9°C, altimeter 30.00 inches. Density altitude at the accident site calculated between 11,110 and 11,578 feet. Forecast winds aloft at 9,000 feet indicated 150 degrees at 11 knots.
Wreckage and Impact Information
The helicopter rested on its right side in a flat meadow at 8,700 feet msl, on a heading of 350 degrees magnetic. The cabin forward of the firewall was consumed by fire. The tail cone sustained thermal damage but remained largely intact; horizontal stabilizer bent 90 degrees upward, tail rotor blades intact, vertical stabilizer undamaged. Landing gear remained attached; right toe separated at forward strut with upward overload buckling. Main rotor blade fragments strewn 30 feet around. Two ground indentations similar to skids were 150 feet south.
Tests and Research
Airframe: Thermal damage precluded complete examination; no pre-existing failures found. The rotor brake wiring had fused wires consistent with electrical arcing. Fuel system: Extensive thermal damage; fuel filler caps in place; auxiliary fuel tank screen free of obstructions; no breaches in fuel hoses; fuel shutoff valve melted; gascolator free of debris; auxiliary fuel pump partially consumed; no failures found. Engine: Attached at mounts; case intact; internal continuity established; thumb compression attained; engine-driven fuel pump diaphragm consumed; no failures precluding normal operation. Fuel injection system: No anomalies or failures noted.
Additional Information
RHC had published service letter SL-36 and service bulletins SB-68, SB-69, and safety notice SN-40 regarding fuel system modifications and fire-retardant suits. SB-68 (rigid fuel line replacement) and SB-69 (gascolator assembly) had been complied with. SL-36 (bladder fuel tanks) was not complied with; it was upgraded to SB-78 three months after the accident, recommending compliance by December 31, 2014. SN-40 recommended Nomex suits; occupants were not wearing them.
Hot Weather Operation: The auxiliary fuel pump warning indicator activates below 23 psi. RHC issued Safety Alert 44 recommending operations below 40.5°C and noting potential for fuel vapor at high ambient temperatures and altitudes; flickering warning light may indicate vapor.
Performance: According to the POH, IGE hover ceiling at full throttle, zero wind, and 2,235 pounds gross weight is about 12,200 feet pressure altitude. No published fuel consumption figures; RHC estimates average 14-16 gallons per hour.
Emergency Procedures: The POH states the auxiliary fuel pump warning light indicates low pressure; if no other indication, land as soon as practical; if accompanied by erratic engine operation, land immediately. The low fuel warning indicator illuminates at about 3 gallons usable.