History of Flight
On July 28, 2010, at 1342 mountain standard time, an American Eurocopter AS 350 B3, registration N509AM, descended rapidly and collided with terrain in an urban area of Tucson, Arizona. The helicopter was operated by Air Methods Corporation as LifeNet 12 on a repositioning flight under Part 91 of the Federal Aviation Regulations. The commercial pilot and two medical flight crew members sustained fatal injuries. The helicopter was substantially damaged and consumed by a post-impact fire. Visual meteorological conditions prevailed; a company flight plan had been filed. The flight originated at Marana Regional Airport, Tucson, at 1332, with an intended destination of the Air Methods base in Douglas, Arizona.
Witnesses reported observing the helicopter flying steadily southeast when it began to descend rapidly. They heard unusual 'whump, whump' sounds and rapid intermittent popping noises, followed by unusual quietness as the helicopter descended. The flight trajectory became increasingly vertical as it turned and approached the ground. The helicopter struck a 5-foot-high concrete wall and was consumed by fire.
The accident helicopter had been positioned at Marana Regional Airport on July 24 for engine maintenance related to a fuel coking problem. The engine was removed, and the fuel manifold was replaced. This involved disassembling the engine, removing and replacing the fuel manifold, and reassembling. The engine was reinstalled on the evening of July 27, and a post-maintenance check flight of 7.5 minutes was performed by the Marana base pilot and mechanic.
On July 28, at 1132, the Douglas aircrew arrived at Marana in a spare helicopter, N106LN. They transferred medical equipment to the accident helicopter. At 1329, the pilot called Life Com, reporting that LifeNet 12 had departed Marana with three persons, 2 hours 55 minutes of fuel, and an estimated en route time to Douglas of 55 minutes.
Radar data from the FAA recorded the first return of LifeNet 12 at 1334:33, at 2,600 feet mean sea level (msl), southeast of Marana. Terrain elevation in the area is about 2,300 feet msl. The track proceeded on a course of 112 degrees magnetic for 17 miles to the accident location. The helicopter climbed to 3,200 feet by 1339:19 and maintained altitude between 3,000 and 3,200 feet until 1341:23. The final two radar returns were at 1341:28 (2,600 feet msl) and 1341:33 (2,400 feet msl), near the accident site.
LifeNet 12 contacted Tucson TRACON around 1333, reporting they were heading southeast low level through the area back to Douglas VFR. TRACON acknowledged radar contact and provided the altimeter setting. No further communications were recorded. At 1341:38, the controller noticed the helicopter had dropped off the radar display and attempted unsuccessfully to contact it.
Radar data showed ground speed averaged 120-130 knots between the first and last returns. Altitude increased from 250 feet agl to 750 feet agl in the first 3.5 minutes, stabilized between 750 and 850 feet for 2.5 minutes, then decreased at 200 fpm for 10 seconds, leveled off for 10 seconds at 750 feet, then descended rapidly at about 2,300 fpm for the final 10 seconds. Ground speed decreased from 132 knots to about 70 knots over the last 20 seconds. Heading was consistent at 112 degrees for the first 6.6 minutes, then changed to 132 degrees during the final 20 seconds. The helicopter entered its final descent from about 800 feet agl roughly 30 seconds before the last radar return. The final 10 seconds of data are consistent with an autorotative descent. The helicopter traveled about 1.3 miles during the last 30 seconds and about 0.25 miles during the final 10 seconds.
An open roadway intersection free of obstacles was located about 570 feet from the final radar return and about 300 feet from the point of ground impact, in line with the final flight path.
External examination of the engine at the accident site revealed that the fuel inlet union was detached from the boss on the compressor case. The fuel supply line remained attached to the union and the hydro-mechanical unit (HMU) via the adjusted valve. The intermediate gasket was found in the fuselage debris below the union.
Pilot Information
The pilot, aged 61, held a commercial pilot certificate with ratings for airplane single-engine land, rotorcraft-helicopter, and instrument airplane and helicopter, issued November 11, 2008. He held a second-class medical certificate with a corrective lenses limitation, issued January 5, 2010. He had flown for the US Army and US Border Patrol, retiring from the Border Patrol in 2002. He then worked for Rocky Mountain Helicopters and was retained by Air Methods. Total flight time as of June 25, 2008, was 13,900 hours, including 9,465 rotary-wing hours and 4,500 single-engine fixed-wing hours. He accumulated 86.9 hours between January 1 and July 28, 2010, and 7.5 hours in the 30 days prior. He received AS 350 pilot transition training in 1989 and AS 350 B3 training in August 2002. His most recent annual competency/proficiency check was on September 14, 2009, with all areas graded satisfactory. Autorotations were practiced during checks. The pilot had completed 6.9 hours of training flights and 4.4 hours of proficiency checks in the 50 months prior to the accident, totaling 11.3 hours. No training flights with autorotations occurred between his last check and the accident, a span of 317 days.
Helicopter Information
The helicopter was a Eurocopter AS 350 B3, serial number 4698, manufactured in 2009. The airworthiness certificate was issued September 9, 2009. Air Methods acquired it on December 23, 2009. It was configured for medical transport with a gurney on the left side. The crew consisted of a pilot, flight nurse, and paramedic. At the time of the accident, the helicopter had 352 total hours. The most recent maintenance was a 20-hour B61 engine inspection on July 27, 2010.
Weight and balance calculations were performed by the pilot using a spreadsheet. The spreadsheet listed an empty weight of 3,329 pounds, crew weights of 210, 210, and 260 pounds, medical equipment at 310 pounds, and liquid oxygen at 18 pounds. Total weight without fuel was 4,330 pounds. The maximum fuel load was 90% (860 pounds), resulting in a total weight of 5,190 pounds, below the maximum gross weight of 5,225 pounds. The actual weight and balance calculation for the accident flight was not recorded and was presumed destroyed. Fueling records indicated 105 gallons were added, and the lineman recalled the pilot requesting 100 gallons; the fuel load was not 100%. Based on the pilot's reported 2 hours 55 minutes of fuel (90%), the helicopter was within the weight and balance envelope at 5,182 pounds takeoff weight.
Maintenance Review
The helicopter was sent to Marana for maintenance due to an engine coking problem. Fuel coking involves carbon deposits on the injection manifold, which can prevent engine starting but does not affect flight performance. The fuel manifold replacement is a Level 3 maintenance action. Helicopter Services of Nevada (HSN) was contracted to perform the work. Between July 24 and 26, the engine was removed and modules separated. An HSN technician replaced the fuel manifold on the accident engine, including the fuel inlet union. After reassembly, the engine was reinstalled by Air Methods mechanics. The HSN technician inspected his own work. Air Methods mechanics did not specifically inspect his work but inspected the engine after installation.
A post-maintenance check flight was performed on July 27, lasting 7.5 minutes. The pilot performed droop check, rate of climb check, cruise power check, flight limit indicator check, flame out check, and autorotation. No records of the test flight were retained. The flight manual requires checks such as hover flight, maximum continuous power climb, maximum takeoff power check, and maximum continuous power level flight, which typically take 30-45 minutes. The pilot had not received specific training for post-maintenance check flights; any Air Methods pilot qualified in model could perform them.
Maintenance Records Review
Maintenance records showed that on June 21, 2010, the engine cycles exceeded AD 2009-09-03 requirements (due at 600 hours or 500 cycles); at that time, the engine had 308.34 hours and 515.28 cycles. The company identified the oversight and complied. On July 22, the aircraft record noted "Aircraft won't crank." On July 23, the engine was removed for fuel coking repair. The work order indicated replacement of the injection manifold. The HSN work order showed disassembly and replacement of the fuel manifold on engine SN 46268. The turbine was reassembled, and ground runs were performed. On July 26, the engine was reinstalled, and ground run checks were completed, including oil pressure and vibration checks. On July 27, the HMU valve seal was replaced, and the 20-hour engine inspection was completed.
Injection Manifold Replacement
The replacement of the injection manifold followed Turbomeca Maintenance Technical Instruction X292M13032Rev4. The procedure included removing the jet union, discarding seals, and installing new packings. The jet union is visible externally; no torque striping is required. Turbomeca authorizes reuse of hardware per the maintenance manual. According to the Eurocopter Maintenance Manual, when an engine is removed and installed, a checkout ground run per the flight manual is required. Post-maintenance operational check flights are also required, including hover flight, climb, and level flight checks.