N126GW

HISTORY OF FLIGHTOn August 1, 2012, about 0900 eastern daylight time a Sikorsky S-58JT, N126GW, operated by Aircrane Inc., was substantially damaged when it incurred a failure of a tailrotor blade in Middletown, Delaware. The certificated commercial pilot was not injured. No flight plan had been filed for the local commercial flight conducted under Title14 Code of Federal Regulations (CFR) Part 133.

According to the 'Safety Officer," who was helping with the external load operation, placing air conditioning units on the roof of the warehouse, the helicopter flew in to the site around 0730. After gathering all of the personnel, she gave a safety briefing and gave instructions to them on how they were going to conduct the operation. She then split the personnel up into two 4 man crews and sent one of the crews off the roof to reduce the number of personnel they had in the way of the operation. Once she had done this, she gave the "High Sign" to start the operation. The first two lifts were good but, on the third lift, when the helicopter came up over the roof, it did not sound right, and was swerving with the air conditioning unit swinging below the helicopter. The helicopter than started spinning and she yelled for the people on the roof to move. Then while the helicopter was spinning and the nose dropping, the air conditioning unit landed on to the roof, and rolled upside down while it was still attached to the helicopter by the cable. She continued to yell for everyone to get away as the helicopter continued to spin with the nose dropping even after the air conditioner had fallen onto the roof. The pilot then released the cable, and the helicopter then began moving away from the building. A portion of a tail rotor blade then landed on the roof.

According to the "Guide Man" who was on the roof, after flying to the warehouse, the helicopter landed and was unloaded. The rigging was than attached to the helicopter. About 45 minutes later, He called for the helicopter and advised that they were ready on the roof. The helicopter lifted the first air conditioning unit and it was placed "dead on" to its mounting location. The second unit was then lifted and it also was "dead on." The helicopter then began lifting the third air conditioning unit, did a normal left turn but, he suddenly heard a high rotor rpm sound. The helicopter then turned into the wind and began spinning over the roof with the air conditioning unit about 12 feet off the roof. The air conditioning unit then touched down on the roof, but the helicopter was still spinning. He then began calling over the radio for the pilot to "break it loose". At this point the air conditioning unit was on the roof upside down, the helicopter then moved away from the building and landed.

According to the pilot, He flew the helicopter over from Summit Airport (EVY), Middletown, Delaware, and landed at the job site. They completed the "Safety Brief" for the area and personnel; and the extra people they did not need for the lift operation were moved off the roof.

The lifts consisted of 2,900 pound roof top air conditioning units. The first two lifts were uneventful. However, during the third lift, while over the curb about 12 feet above ground level, the pilot felt vibrations in the pedals for a moment. The vibrations became violent, which activated the emergency locator transmitter and the landing light.

The helicopter started to rotate about its vertical axis, and though he tried, he could not stop the rotation. He reduced power, then moved the aircraft from above the roof and jettisoned the cable. He then flew the helicopter away from the building, and cleared the roof. He then picked up forward speed, turned to the right to line up with a street, and did a roll on landing. PERSONNEL INFORMATIONAccording to Federal Aviation Administration (FAA) records, the pilot held a commercial pilot certificate with ratings for helicopter and instrument-helicopter. He also held type ratings for the S-58 and S-61. His most recent FAA second-class medical certificate was issued on January 3, 2012. He reported that he had accrued 16,500 total hours of flight experience, of which, 7,000 hours were in the accident helicopter make and model. AIRCRAFT INFORMATIONThe commercial version of the S-58 helicopter was certificated by the FAA on August 2, 1956. The S-58 featured a 56 foot diameter, 4 bladed main rotor, and a 4 bladed tail rotor. Both main and tail rotor blades used the symmetrical NACA 0012 airfoil. The fuselage was all metal, and was equipped with conventional landing gear (main wheels in front, tail wheel in back).

According to FAA and maintenance records, the helicopter was manufactured in 1959. It was modified on July 7, 1971 with the removal of its radial engine and installation of a Pratt & Whitney Canada PT6T-3 Twin-Pac Turbine engine. A few years later, it was upgraded to a PT6T-6. Its last continuous airworthiness inspection was completed on July 31, 2012. At the time of the accident the helicopter had accrued 11,064.7 hours of operation. METEOROLOGICAL INFORMATIONThe recorded weather at New Castle Airport (ILG), Wilmington, Delaware, located 10 nautical miles northeast of the accident site, at 0851, included: calm winds, 8 miles visibility, clear skies, temperature 23 degrees C, dew point 22 degrees C, and an altimeter setting of 29.90 inches of mercury. AIRPORT INFORMATIONThe commercial version of the S-58 helicopter was certificated by the FAA on August 2, 1956. The S-58 featured a 56 foot diameter, 4 bladed main rotor, and a 4 bladed tail rotor. Both main and tail rotor blades used the symmetrical NACA 0012 airfoil. The fuselage was all metal, and was equipped with conventional landing gear (main wheels in front, tail wheel in back).

According to FAA and maintenance records, the helicopter was manufactured in 1959. It was modified on July 7, 1971 with the removal of its radial engine and installation of a Pratt & Whitney Canada PT6T-3 Twin-Pac Turbine engine. A few years later, it was upgraded to a PT6T-6. Its last continuous airworthiness inspection was completed on July 31, 2012. At the time of the accident the helicopter had accrued 11,064.7 hours of operation. WRECKAGE AND IMPACT INFORMATIONPost accident examination of the helicopter by a Federal Aviation Administration (FAA) inspector revealed that the entire aft portion of one of the tail rotor blades was missing. Further examination revealed that it had separated at a point just aft of the broken tailrotor blade's spar where a bond line existed.

The separated aft portion of the broken tailrotor blade was later recovered from the roof of the warehouse by the operator. All four tailrotor blades including the seperated aft portion from the broken blade were then retained by the NTSB for further examination.

According to the operator after the accident, the yaw spring was inspected and returned to service on the accident helicopter.

The tail rotor assembly and intermediate gearboxes were scrapped along with the tail rotor drives. The chip detectors were inspected and found to be clean and the main rotor gearbox was inspected, and its chip plugs and screen were also found to be clean. The main rotor gearbox oil was changed, and a gear box penalty run of one hour was performed, the chip plugs and oil screen were then inspected again and were still found to be clean, and it was returned to service.

All of the hanger bearing supports, gearbox mounting flanges, and the pylon fittings then were subjected to a die penetrant inspection for cracking and no defects were noted.

All of the tail rotor drive shafts were scrapped and replaced with overhauled ones.

The pylon was also inspected for structural integrity and loose rivets and all of the inspection panels were opened on the helicopter and inspected with no defects being noted.

The helicopter was returned to service in October of 2012 and at the time of this report had been operating without incident. ADDITIONAL INFORMATIONIn 1970, Sikorsky had set up a production line to remanufacture S-58 helicopters to the S-58T configuration which included replacing the R-1820-84 Radial engine with a Pratt & Whitney Canada PT6T-3 Twin-Pac Turbine engine installation.

FAA approval for the modifications was received in April 1971. Sikorsky also produced kits which allowed S-58 helicopter operators to convert their helicopters to the S-58T Configuration.

An improved version of the S-58T, the S-58T Mark II, added a more powerful engine which improved one engine inoperative capabilities and installed a bifilar vibration absorber which reduced rotor induced vibration. The bifilar provided improved pilot and passenger comfort and reduced aircraft maintenance.

In 1981, Sikorsky sold the manufacturing rights, and support for the S-58/S-58T to California Helicopter International (California Helicopter Airways). This included all tooling, jigs, fixtures, drawings, and spares inventory. Sikorsky however, retained the type certificate and the responsibility for the manufacturing, repair, and overhaul of the main and tail rotor blades. Over the years though, as Sikorsky moved on to manufacture other helicopters; they ceased manufacturing, repair and overhaul of the main and tailrotor blades. As a result to maintain operational safety support, on May 6, 2015, Sikorsky transferred the type certificate for the S-58, as well as the S-55, and S-62 models to California Helicopter Airways. TESTS AND RESEARCHTail Rotor Control System

The tail rotor was controlled through a hydraulically boosted cable system with push-pull rods which connected a rear fuselage bell crank to the rotor. The hydraulic servo operated on the tension difference between the two cables and, as the system was a boosting system with the power piston in series with one of the cables and not a fully powered system, the yaw pedals had a direct mechanical link to the rotor blade pitch change mechanism.

The ...