Ponte Vedra Bch, FL, USA
N744SH
Robinson R44 II
The local instructional flight was scheduled for a east departure from the airport and a flight south along the coastline. Several witnesses observed the helicopter approximately 200-500 feet above ground level (agl) in cruise flight along the coastline on a south 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. Examination of the helicopter's 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, pal nut) 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 pal nut was noted. Material analysis of the components revealed that only one of the two nuts for the left and right connections were installed, and then only finger tight. The nut on right servo connection rotated off during flight which allowed the bolt to extract itself and disconnect the servo from the push-pull tube. Prior to the accident flight, an inspection, which required the push-pull tubes to servo connections to be disassembled, was performed on the helicopter, and a 0.5-hour maintenance test flight. The mechanic who preformed the inspection, stated he forgot to properly secure the hardware for the left and right servo connections. The mechanic stated the reasons for the error were the following: 1. He was pulled," in all directions" by company personnel since his arrival at that facility; 2. The "reassembly was not opposite of the disassembly," which was a personal maintenance practice he used to eliminate errors; 3. Two nights prior to the completion of the inspection and the maintenance test flight, the apprentice providing assistance, wanted to stay late to finish with the mechanic a certain section of the inspection. As a result, the mechanic forgot to go back and secure the hardware connecting the two push-pull tube to servo joints; 4. The company was understaffed with maintenance personnel. According to the company's maintenance quality control program, any maintenance completed on a helicopter was to be inspected by another mechanic. A review of the program revealed that the mechanics were not following the program, and the company was not providing oversight and enforcing the program.
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 Center, Oklahoma City, Oklahoma, examined the specimen's taken by the medical examiner. Toxicological tests performed on the flight instructor were negative for carbon monoxide, cyanide, and ethanol. An unspecified amount of ibuprofen was detected in the blood. TESTS AND RESEARCH Servo and Push-Pull Tube Materials Examination The NTSB's Materials Laboratory examined the right main servo with a portion of the push-pull tube, the left main servo with a portion of the push-pull tube, and the rear main servo with a portion of the push-pull tube. The push-pull tube for the right servo was received detached from the servo. The push-pull tubes for the left and rear servos were still attached to their respective servos. The right servo was received with a portion of the cabin bulkhead still attached to it. The servo and the portion of bulkhead displayed soot deposits and areas of re-solidified, rounded metal consistent with being in a fire. However, the piston rod and the clevis located at the upper end of the servo displayed no sooty deposit. Examination of the detached portion of the right servo push-pull tube revealed sooty deposit consistent with being in a fire. The ball in the spherical bearing rod end was found jammed in a position approximately 90 degrees from its normal position. Manipulation of the ball portion of the spherical bearing revealed that it could not be rotated by hand. The left servo was received with the push-pull tube attached to the servo rod clevis with a bolt, two washers, and a nut, with the nut almost unthreaded from the bolt. The components displayed sooty deposits and areas of re-solidified, rounded metal consistent with being in a fire. Manipulation of the nut revealed that it could easily be unscrewed from the bolt. An examination of the exposed bolt threads, between the nut and the clevis, revealed a sooty deposit consistent with being in a fire. The rear servo was received with the push-pull tube attached to the servo end clevis with a bolt, two washers, a nut, and a palnut. The components displayed sooty deposits and areas of re-solidified, rounded metal consistent with being in a fire. The bolt attaching the rod end to the clevis was secured firmly by the nut and a palnut. Mechanic Interview Summary On March 28th, after the examination of the wreckage, the NTSB IIC interviewed the mechanic with company personnel present regarding the maintenance performed on the helicopter prior to the accident flight. The mechanic stated that he obtained his airframe and powerplant (A&P) certificate in March 2003. In May 2005, the mechanic was hired with Silver State Helicopters in Montana as a full-time mechanic. In January 2006, the mechanic attended the Robinson Helicopter Company maintenance course for the Models R22 and R44. Since his employment with Silver State Helicopter, the mechanic had worked at the company facilities in Montana, Nevada, and Florida. The mechanic stated he was a roving mechanic for the company and helped where the company needed temporary assistance. Prior to starting the inspection on the accident helicopter, the mechanic asked several pilots who flew the helicopter on a regular basis whether they had any discrepancies. The pilots reported a "slight hop" with the helicopter during straight and level flight. The mechanic stated he worked on the following items, but not limited to, during the inspections: engine paneling, mast fairing ribs (4 of 6 were cracked), balance rotor, main rotor pitch links, main rotor teeter friction, and mast fairing. During the inspection, the mechanic utilized the Robinson Maintenance Manual 100/300-hour inspection checklist. After the inspection, the mechanic "put everything back together." Prior to installing the mast fairing, the mechanic asked a pilot, who regularly assisted the mechanics with minor maintenance items, to "take a second look" at the work accomplished on the helicopter. The pilot and mechanic conducted a maintenance test flight for 0.5 hours. After the test flight, they put the helicopter back in the hangar and the mechanic "signed off the books." On March 29th, the NTSB IIC conducted a second interview with the mechanic and informed him of the findings from the wreckage examination concerning the missing hardware on the right servo to push-pull tube joint and the "finger tight" hardware noted on the left forward servo to push-pull tube joint. Upon informing the mechanic of the investigation's findings, the mechanic stated, "I can tell you exactly why that happened." The mechanic then proceeded to explain to the NTSB IIC his reasons for the investigation's findings, which included the following: 1. He was pulled in all directions by company personnel since his arrival at that facility; 2. The "reassembly was not opposite of the disassembly," which was a personal maintenance practice he used to eliminate errors; 3. A couple of nights prior to the completion of the inspection and the maintenance test flight, the apprentice wanted to stay late (with the mechanic) and finish a certain section of the inspection which involved the mast fairing area. As a result, the mechanic forgot to go back and secure the hardware connecting the two push-pull tube to servo joints; 4. The company was understaffed with maintenance personnel. Mechanic Statement After the interview, the NTSB IIC requested a statement from the mechanic concerning his duties since arriving at the Jacksonville location. According to the statement, on March 9th, the mechanic arrived at the company's Jacksonville facility to initially assist with a company seminar. After the seminar was over, the mechanic was told to remain at the Jacksonville location to assist with maintenance on two helicopters used for Federal Aviation Regulations Part 135 contracts and also to assist the Jacksonville facility's lead mechanic in maintaining the fleet of Robinson R22 helicopters. The mechanic was typically assigned to assist with the company's Part 135 contracts. On March 19th, the mechanic began work on the 100/300-hour inspection of the accident helicopter. The mechanic reported, "For the next three days, I worked diligently on this inspection, finding several discrepancies, including cracked eng
the mechanic's improper installation of the attachment hardware for the servo to swashplate push-pull tube joint which resulted in a disconnection, subsequent loss of control, and impact with terrain. Contributing factors were the company management's inadequate surveillance and enforcement of maintenance procedures, the excessive maintenance workload due to inadequate staffing of maintenance personnel, and the insufficient management of maintenance tasks.
Source: NTSB Aviation Accident Database
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