N744SH

HISTORY OF FLIGHT

On March 27, 2007, approximately 1030 eastern daylight time, a Robinson R44 II single-engine helicopter, N744SH, was destroyed when it impacted terrain following a loss of control during cruise flight near Ponte Vedra Beach, Florida. The flight instructor and student pilot were fatally injured. The helicopter was registered to and operated by Silver State Helicopters, LLC, North Las Vegas, Nevada. Day visual meteorological conditions prevailed, and a company visual flight rules flight plan was filed for the Title 14 Code of Federal Regulations Part 91 instructional flight. The local flight departed the Craig Municipal Airport (CRG), Jacksonville, Florida, approximately 1010.

According to Silver State personnel, the local instructional flight was scheduled for a time block between the hours of 0900 and 1100. The flight was originally scheduled to be conducted in the Robinson R22 helicopter; however, due to a scheduling conflict, the R22 was not available. Due to the conflict, the Silver State local management then allowed the instructor and student to conduct an orientation and familiarization flight in the R44 helicopter. The route of flight was scheduled for an east departure from CRG, south along the Atlantic Ocean coastline to St. Augustine, then back to CRG.

Several witnesses observed the helicopter approximately 200 to 500 feet above ground level (agl) in cruise flight along the coastline on a southerly heading. One witness, a former pilot and mechanic, reported he observed the helicopter in straight and level flight, then heard a change in "rotor noise, followed by a bang/pop/twang sound." The helicopter then "snap-rolled" to the left and descended into the terrain in a nose low attitude. The helicopter impacted the sand terrain, bounced, and came to rest near the low tide water line. A post-impact fire ensued and extinguished itself a short time thereafter.

PERSONNEL INFORMATION

The instructor, age 38, who was seated in the left seat, held a flight instructor certificate with a helicopter rating, issued August 16, 2006, and a commercial pilot certificate with a helicopter rating, issued February 16, 2006. The instructor's most recent Federal Aviation Administration's (FAA) second-class airman medical certificate was issued on June 27, 2006, with no restrictions or limitations.

According to the company, the instructor had accumulated 462 total helicopter flight hours, 173.5 flight hours as an instructor, and 29 hours in the accident helicopter make and model. The instructor completed her flight training for her flight instructor and commercial certificates with Silver State Helicopters. She began instructing at the company's Jacksonville location on November 24, 2006.

The student, age 24, who was seated in the right seat, held a third-class medical certificate and student pilot certificate, issued October 18, 2006. The medical certificate contained a limitation for corrective lenses. According to the company, the student had accumulated 10 hours of flight training in R22s.

AIRCRAFT INFORMATION

Accident Helicopter Information

The 2005-model helicopter, a Robinson R44 II, serial number 10830, was a four-seat, single main rotor, single-engine helicopter that was constructed primarily of metal and equipped with skid type landing gear. The helicopter was powered by a Lycoming IO-540-AE1A5 engine, serial number, L-30335-48A. The gross weight of the helicopter was 2,500 pounds. The helicopter was issued a standard airworthiness certificate and was registered to the owner on October 5, 2005.

Flight Control System

According to the helicopter's pilot operating handbook (POH), dual controls are standard equipment and all primary controls are actuated through push-pull tubes and bellcranks. The main rotor flight controls are hydraulically boosted to eliminate cyclic and collective feedback forces. The hydraulic system consists of a pump, three servos, a reservoir, and interconnecting lines. Normal operating pressure for the system is 450 to 500 pounds per square inch (psi). The pump is mounted on and driven by the main rotor gearbox to maintain hydraulic pressure in the event of an engine failure. A servo is connected to each of the three push-pull tubes that support the main rotor swashplate. The swashplate push-pull tubes are connected to the swashplate assembly and the upper linkage of the servos. The bottom linkage of each servo is connected to a bellcrank/fork assembly, which then connects to the cyclic and collective thru a series of push-pull tubes and bellcranks.

According to the Robinson Model R44 Illustrated Parts Catalog, Figure 7-63 Push-Pull Tube Assemblies, the rod end of each push-pull tube is connected to the servo clevis with the following hardware: NAS6605-9 bolt, two NAS1149F0532P washers, MS21042L5 nut, and a B330-16 palnut.

The Robinson Model R44 Maintenance Manual, Section 1.300 Fastener Torque Requirements section documents that fasteners should be torqued to standard dry values listed in section 1.320. The dry torque requirement for the bolt is 240 inch-pounds, and 20 to 40 inch-pounds for the palnut. According to the manual, a secondary locking mechanism (palnut) is required on all critical fasteners. The maintenance manual describes a critical fastener as the following, "A critical fastener is one, which, if removed or lost, would jeopardize safe operation of the helicopter. This includes joints in the primary control system, and non-fail-safe structural joints in the airframe, landing gear, and drive system." In addition to the palnut, torque seal (paint) is to be applied to all critical fasteners after palnut installation in a strip across both nuts and exposed bolt threads.

The POH Daily and Preflight Checks for the helicopter do not require inspection of the lower push-pull tube to servo joint in the primary control system. A mast fairing surrounds the servo to push-pull tube joint of the main rotor control system and an access/inspection panel does not exist.

Maintenance Information

The helicopter's most recent inspection, a 100/300-hour inspection, was completed on March 26, 2007. At the time of the inspection, the total aircraft time was 861.6 hours. The airframe and engine were inspected in accordance with their respective manufacturer's maintenance manuals. According to the airframe logbook entry for the inspection, the mast fairing ribs were removed and replaced. A review of the Robinson Maintenance Manual Inspection Checklist used by the mechanic for the 100/300-hour inspection revealed that the mechanic initialed the blocks, "Unairworthy" and "Repaired" for the mast fairing rib inspection item. During the mast fairing rib replacement, the two forward swashplate push/pull tubes were removed from their respective hydraulic servos. Prior to the aircraft being returned to service, the mechanic and a company pilot performed a 0.5-hour maintenance test flight. The accident flight was the first flight performed after the maintenance test flight.

METEOROLOGICAL INFORMATION

At 1053, the CRG automated surface observing system (ASOS) reported the wind from 120 degrees at 6 knots, visibility 10 statute miles, sky broken at 2,800 and 3,900 feet mean sea level (msl), temperature 23 degrees Celsius, dew point 16 degrees Celsius, and an altimeter setting of 30.24 inches of Mercury.

WRECKAGE AND IMPACT INFORMATION

The main wreckage came to rest on the sand beach at 30 degrees 13.54 minutes north latitude and 81 degrees 22.32 minutes west longitude. The initial impact point was a 4-foot crater in the sand terrain located at the high tide waterline. The helicopter wreckage was distributed along a measured magnetic heading of approximately 160 degrees from the initial impact point. The main wreckage came to rest approximately 100 feet from the initial impact point. The main wreckage consisted of the fuselage, main rotor assembly, tailboom, and tail rotor. Several fragmented pieces of the fuselage and skid tubes were located between the initial impact and main wreckage. The engine was separated from the airframe and came to rest adjacent to the main wreckage. In order to prevent further damage due to tide change, the wreckage was recovered under the supervision of a FAA inspector to a secured facility at CRG.

Examination of the helicopter at the CRG facility by the NTSB investigator-in-charge (IIC), FAA inspectors, and representatives from the airframe and engine manufacturers revealed that the fuselage sustained thermal damage, impact damage to the right side, and was fragmented. The forward section of the tailboom, lower mast, and engine cowling sustained thermal damage. The skids were destroyed and fragmented into several sections. The main rotor blades displayed bending and compression wrinkles, and several sections of the honeycomb and skin were separated. Drive system continuity was established from the main transmission to the main rotor and tail rotor. Flight control continuity could not be established.

Examination of the flight control system revealed that the right forward servo to swashplate push-pull tube joint was disconnected and the attach hardware (bolt, lock nut, two washers, palnut) was missing. The left forward servo to swashplate push-pull joint was connected; however, the nut was found partially engaged on the bolt threads, and the torque was "finger tight"; no palnut was noted. The rear servo and push-pull tube joint was secured with the appropriate hardware.

PATHOLOGICAL INFORMATION

Autopsies were performed on both the flight instructor and student pilot by the Office of the Medical Examiner, District 23, St. Augustine, Florida, on March 28, 2007. Specimens for toxicological tests were taken from the flight instructor by the medical examiner. Specimens from the student pilot were not retained.

The FAA's Civil Aeromedical Institute's Forensic and Accident Research...