Sikorsky will start certification testing on the S-434 light turbine single in January, thus postponing the target certification date to December next year.
“We have completed more than 50 hours of development flight tests to mitigate risks and develop new systems,” a Sikorsky spokesperson told AIN. Engineers are now conforming two aircraft for certification flight tests, and they anticipate 75 to 100 hours of trials. These will include endurance, flight strain, flight handling qualities, performance, engine installation and noise tests.
One aircraft will be used for developing the new tail rotor, assessing performance and flight handling tests. The second aircraft be used for endurance and flight strain testing. They will be used with FAA approval in mind. Depending on foreign orders, Sikorsky might seek certification from other civil aviation authorities, such as Europe’s EASA.
The S-434 is an improved Schweizer 333. The S-434 has a four-blade main rotor (its predecessor has a three-blade rotor), a new tail rotor-blade design, a structurally enhanced landing gear, a new trim system and an improved Kaflex driveshaft. The four-blade main rotor and improved main rotor transmission come from the unmanned Fire Scout. The S-434 and the S-333 use the same Rolls-Royce 250-C20W turboshaft, which produces 320 shp.
The four-blade main rotor provides the S-434 with substantial performance improvements and handling characteristics over a S-333 at a comparable gross weight, according to Sikorsky. Moreover, it allows a 300-pound increase in the mtow, to 2,850 pounds. This translates into a useful load of more than 1,400 pounds.
The new tail rotor can generate more than 20 percent more thrust than the tail rotor on an S-333, which the company claims improves yaw handling and controllability despite the increased weight. “The increased inertial characteristics of the four-blade rotor system coupled with the new tail rotor, control system and a more rugged landing gear provide an exceptional training platform with a robust design and high student margins,” the spokesperson said.
Sikorsky claims to have orders for three civil S-434s for “personal transportation, patrol and training.” The orders for two of these helicopters come from outside the U.S. The U.S.-based manufacturer has already delivered nine of the new aircraft to the Saudi Ministry of Interior for defense-related missions that do not need civil papers.
Once the S-434 is certified, Sikorsky will have to determine whether it continues production of both the S-333 and its derivative. “The German Army bid is for S-333s because the S-434 will not be certified until December 2011,” the spokesperson said.