History of Flight
On April 4, 2019, at about 1416 eastern daylight time, a Robinson R44 II helicopter, registration N4046J, was substantially damaged during a forced landing to a roadway near Tampa, Florida. The pilot and the passenger were not injured. A passenger in a nearby vehicle was fatally injured, and the driver of the vehicle sustained serious injuries. Visual meteorological conditions prevailed, and no flight plan was filed for the positioning flight, which was destined for Sarasota/Bradenton International Airport (SRQ), Sarasota, Florida. The flight was conducted under Part 91 of Title 14 Code of Federal Regulations.
Five days before the accident, the helicopter owner reported an engine total power loss while flying at 1,000 ft mean sea level. He performed an autorotation to a field with no damage. After restarting, the engine lost power again when collective was applied. The owner contacted the helicopter manufacturer.
On the morning of the accident, an FAA inspector observed two mechanics from Florida Suncoast Helicopters performing maintenance. They cleaned the fuel screen and checked for contamination. A pilot employed by Florida Suncoast Helicopters started the engine, and when collective was applied, the engine lost total power. After consulting the manufacturer, the mechanics replaced the fuel servo unit. A test run and hover for several minutes showed no issues. The pilot and one mechanic departed the field about 1401 to reposition the helicopter to SRQ. About 15 minutes later, the engine lost total power, and the pilot performed an autorotation to a roadway.
After touchdown, the helicopter slid on the pavement due to forward momentum, then slid sideways. The main rotor blades contacted a telephone pole, and a 2.5-ft-long piece of a main rotor blade separated and struck the windshield of a passing truck.
Aircraft and Wreckage Information
The helicopter was a four-seat Robinson R44 II, manufactured in 2019, powered by a Lycoming IO-540-AE1A5, 260-horsepower engine. Total airframe and engine time was 81.34 hours. The helicopter came to rest on a heading of 180 next to a telephone pole that had been cut in half. Both main rotor blades were fractured at the tips with cable cuts. The skids were damaged consistent with a hard landing, and the rear cross-tube was fractured. The tailcone was buckled on the top at the second bay. One pitch link was fractured and separated. The vertical firewall was wrinkled at the lower right corner.
Examination of the engine revealed a partially collapsed induction air inlet duct. The inner rubberized fabric liner had partially delaminated and separated from the outer layer, obstructing the duct interior. The wire stiffener between the layers was displaced in two locations near the center of the duct. No other discrepancies were found.
The duct was sent to the NTSB Materials Laboratory. Dissection revealed a liquid residue, which was analyzed as several oxidized vegetable oils, including castor oil used by the duct manufacturer, along with a water-based release agent.
Additional Information
The induction air inlet duct was constructed with an inner layer of fiberglass cloth impregnated with silicone rubber, a helical steel wire, and an outer layer of rubberized silicone cloth. Two fiberglass cords were wrapped outside. The duct was cured in an oven.
As a result of this accident, Robinson Helicopter issued Service Bulletin (SB)-97 on April 11, 2019, requiring inspection of air induction hoses with part No. A785-31 on specific R44 II helicopters. The bulletin advised owners, operators, and maintenance personnel to visually inspect inside the hose for separation between outer and inner layers and to flex the hose listening for a crinkling sound. Any hose with indication of separation was to be replaced before further flight.
Robinson Helicopter also issued SB-100 on July 3, 2019, expanding inspections to other R44 II helicopters and spare A785-31 hoses shipped through March 2019. The FAA issued Airworthiness Directive 2019-12-18, effective July 5, 2019, requiring inspection of the air induction hose within 10 hours time in service on specific R44 II helicopters, including those with an A785-31 hose installed after April 30, 2018. The directive stated that if any separation or crinkling sound was found, the hose must be replaced before further flight; otherwise, it could be replaced within 50 hours time in service.