N515MK

**This report was modified on 1/25/2012 and on 4/23/2012. Please see the docket for this accident to view the original report.**

HISTORY OF FLIGHT

On June 2, 2010, at 1400 central daylight time, a Bell 222U, N515MK, registered to and operated by CareFlite, Grand Prairie, Texas, collided with the ground following an in-flight break-up near Midlothian, Texas. The post maintenance flight was operated under the provisions of 14 Code of Federal Regulations Part 91. Visual meteorological conditions (VMC) prevailed and a company flight plan was filed. The airline transport pilot and mechanic were killed. The helicopter sustained substantial damage. The flight departed from Grand Prairie Municipal Airport (GPM) Grand Prairie, Texas, at 1352, about 8 minutes before the accident.

During interviews with the National Transportation Safety Board (NTSB) investigator-in-charge (IIC), several witnesses consistently reported seeing the tail boom, main rotor hub, main rotor blades, and other debris separate from the helicopter. Another witness heard a "loud crack" sound. The helicopter subsequently collided with the ground and exploded into flames.

Review of radar data confirmed N515MK departed GPM at 1352:03. The helicopter proceeded southbound until the last radar target was recorded at 1359:49. The last six radar hits recorded from 1359:26 to 1359:49 indicated an average altitude of 1,300 feet mean sea level (msl), at an average ground speed of 115 knots, and an average ground track of 178 degrees.

PERSONNEL INFORMATION

The certificated airline transport pilot, age 44, held an airline transport pilot certificate, with a rating for rotorcraft-helicopter, issued on November 10, 2004. In addition, he held a commercial pilot certificate, with ratings for airplane single-engine land, airplane multiengine land and instrument airplane, issued on November 10, 2004. The pilot also held a flight instructor certificate, with ratings for rotorcraft-helicopter and instrument-helicopter, issued on July 18, 2009, and a ground instructor certificate, with ratings for advanced and instrument, issued on November 10, 2004.

He was issued a second-class airman medical certificate on January 21, 2010, with no limitations. The pilot's logbook was not recovered for examination. Based on the pilot’s airman medical certification application, company crewmember records and other documents, his total flight experience was estimated at 6,500 hours with at least 5,300 hours in helicopters, and an estimated 346 hours in Bell 222 helicopters. The pilot’s last Part 135 competency check in the Bell 222U was completed on July 29, 2009. He completed a Part 135 competency check and flights review in an Augusta A-109E on April 23, 2010. The pilot had flown 19.6 hours in the last 90 days of which 9.8 hours were in the Bell 222U. He had flown 3.2 hours in the last 30 days.

The mechanic, age 23, held a mechanic certificate with ratings for airframe and powerplant, issued on September 26, 2006. In addition, he held a private pilot certificate, with a rating for rotorcraft-helicopter, issued on April 19, 2006. The mechanic’s pilot logbook was not recovered. The mechanic held a first-class airman medical certificate that was issued April 13, 2007, with no limitations.

AIRCRAFT INFORMATION

The Bell 222U was a 5-place twin engine helicopter, serial number 47515, and was equipped with high skid landing gear. The pilot’s station was located in the right cockpit seat and the co-pilot’s station in the left cockpit seat. Flight controls were not installed in the co-pilot station. A medical interior was installed in the main cabin with seats for three passengers and a stretcher for one patient. Two Honeywell LTS-101-750-1, 680-shaft horsepower engines powered the helicopter.

The helicopter had been previously maintained on the manufacturer’s inspection program was in the process of being added to the operator’s Approved Airworthiness Inspection Program (AAIP). According to the Pilot/Operator Aircraft Accident Report (NTSB Form 6120.1) submitted by the operator, the helicopter had an estimated total time in service of 9,925.1 flight hours. A review of the maintenance logbooks indicated that the last recorded inspection of the engines and airframe was a 600-hour inspection which had been completed on May 27, 2010, at 9,924.0 hours.

Prior to the accident, the swashplate and lever assembly (p/n 222-010-400-127, s/n EA136) was removed from N515MK. The swashplate and lever assembly (p/n 222-010-400-127, s/n EA0052), previously installed on N142CF, was reinstalled on N515MK at 9,925.0 total time air frame hours. As of the accident date, the recently installed assembly had approximately 49.9 hours remaining until overhaul.

The outer ring assembly, (p/n 222-010-403-005, s/n AR-16) had accumulated 4,069.6 hours since new and 2,450.1 hours since overhaul. The drive pins, (p/n 230-010-402-103, s/n A-5 and s/n A-17), were installed in the outer ring assembly during an overhaul on December 23, 1999.

A review of manufacturing records provided by Bell Helicopter Textron show they built 17 drive pins of p/n 230-010-402. Fifteen were non-stepped straight pins (p/n 230-010-402-101) and two were stepped pins (p/n 230-010-402-103), s/n A-5 and A-17. All 17 of the drive pins built were hardened in furnace number 72212-03. The s/n A-5 drive pin was the only part aged in furnace number 72101-15.

The maintenance manual requires an inspection of the drive pins, (p/n 230-010-402-103), every 300 hours. The last inspection was conducted at 2,346.4 hours. The drive pins had accumulated about 5.9 flight hours of operation since that inspection had been completed.

A records review revealed none of the rotor system components had any history of being involved in a previous accident.

METEOROLOGICAL INFORMATION

At 1353, the automated surface observing system (ASOS) at Arlington Municipal Airport (GKY), Arlington, Texas, about 11 miles north northwest of the accident site. reported the wind from 200 degrees at 8 knots, gusting to 14 knots, visibility 10 statute miles, sky clear, temperature 33 degrees Celsius, dew point 19 degrees Celsius, and an altimeter setting of 29.77 inches of Mercury.

At 1350, the ASOS at GPM, about 13 miles north of the accident site, reported the wind from 210 degrees at 10 knots, visibility 10 statute miles, few clouds at 5,000 feet, temperature 34 degrees Celsius, dew point 18 degrees Celsius, and an altimeter setting of 29.79 inches of Mercury.

COMMUNICATIONS

At 1349 N515MK called the FAA contract air traffic control tower at GPM and requested to depart the Care Flite ramp southbound to Joe Pool Lake. The tower approved the departure and issued N515MK the altimeter setting. N515MK acknowledged and departed. There were no further recorded conversations between N515MK and the tower.

WRECKAGE AND IMPACT INFORMATION

The wreckage was located in a field about 13 miles south of GPM at an estimated surface elevation of 650 feet msl. The fuselage was oriented on a 044-degree heading, covered in soot and partially consumed by thermal damage. The other portions of the wreckage did not exhibit fire damage. The separated tail boom was found approximately 550 feet northeast from the main fuselage and 340 feet northeast from the main rotor. The main rotor was found approximately 220 feet northeast from the fuselage. The fractured and separated main rotor mast section was found about 80 feet east of the main fuselage.

Pieces of wreckage found northeast of the main fuselage included fuselage skin from a sponson, a patient backboard, sections of tail boom skin exhibiting tail rotor blade strikes, and push-out window sections. The most distant debris was located about 1,500 feet north-northeast of the main fuselage and included several pieces of main rotor blade skin and small fuselage paint chips.

The main rotor system was found mostly intact. There was no evidence that large pieces departed from the main rotor, although some blade skin and honeycomb had departed the rotor blades. One main rotor blade exhibited trailing edge damage just inboard of the outboard trim tab, consistent with striking a hard object. A severed mesquite tree and bent steel rebar exhibited evidence of contact where the main rotor came to rest. The other main rotor blade exhibited abrasions and gouges on its bottom surface, exhibiting signatures consistent with contact with a hard object. Further examination revealed a separated tail rotor hanger bearing section fit the size and shape of a gouge on the bottom main rotor blade skin surface. For identification and differentiation purposes, the main rotor blades were labeled "A" and "B".

The A side pitch change link had intact connections at both top and bottom but was bent near the center of the link. The B side pitch change link was connected to the walking beam on its bottom end, but the bolt was fractured at the upper connection to the pitch change horn.

The rotating outer ring swashplate was found with the A side drive pin fractured and separated. The separated head of the side A drive pin remained in the interior of the swashplate. The entire shank and attaching hardware from side A were not found. The side B drive pin on the opposite side was found intact and installed in the rotating swashplate.

The separated tail boom assembly was found in an upright orientation and flattened on its bottom surface. It exhibited fractures of the tail boom skin and longerons approximately 4 inches aft of the fuselage attachment structure. The left end plate on the horizontal stabilizer exhibited a main rotor blade strike near its bottom surface. The strike was to the inboard face on the bottom of the end plate in an outboard direction. The tail boom also exhibited strikes to the left side of the aft tail boom area, which matched damage to the tips of both tail rotor blades. The tail rotor hub and blade assembly remained connected to the tail boom assembl...