Posted by John McHale SAVANNAH, Ga., 22 June 2010. A fourth aircraft is now part of the Gulfstream G650 flight-test program, Gulfstream Aerospace Corp. announced. The newest ultra-large-cabin, ultra-long-range test aircraft has already spent more than five hours in the air. Unlike its three predecessors, the fourth G650 (S/N 6004) is a production aircraft. S/N 6004 will be the first G650 outfitted and tested with a full interior, which will be installed later this summer. The aircraft, which will be used to evaluate the aircraft's cabin systems, is expected to resume flight testing following the installation. The G650 flight-test program involves an estimated 1,800 hours of flight and a specific purpose for each of five aircraft. S/N 6001 is focused on envelope expansion, air data calibration, flutter, in-flight performance, and flight controls. S/N 6002 is used to evaluate the aircraft's systems, while S/N 6003 tests the avionics, in-flight load measurement, and ice protection system. S/N 6005, which has been turned over to the Flight Test department for outfitting, will participate in the reduced vertical separation minimum testing. "We're delighted with the performance we're seeing out of these aircraft," says Pres Henne, senior vice president of programs, engineering and test, Gulfstream. "We're equally thrilled with the streamlined manufacturing process, which involves 50 percent fewer parts, bonded materials and precision build carts, which allow us to easily put aircraft pieces together. Our use of these advanced materials and systems â along with the three-dimensional solid models we utilized in the design process â have provided impressive results. We couldn't be more pleased." The G650 flight-test program officially began on Nov. 25, 2009. Through June 20, the four aircraft currently in the program have completed more than 85 flights and 240 flight-test hours. Ultimate load testing of the aircraft's primary structural components has also begun. In April, the aircraft completed the structural limit load testing required by the Federal Aviation Administration (FAA) and the European Aviation Safety Agency (EASA). The limit load represents the maximum load the aircraft should experience during its life cycle. Ultimate load is 50 percent more than limit load. Ultimate load testing will be performed on the fuselage, wing, vertical, and horizontal stabilizers, nose landing gear and all control surfaces. The G650 has also flown at its maximum takeoff weight of 99,600 pounds and recently reached its maximum operational Mach number of Mach 0.925 at 42,500 feet. The G650 offers the longest range at the fastest speed in its class. Powered by best-in-class Rolls-Royce BR725 engines, the business jet will be capable of traveling 7,000 nautical miles at Mach 0.85, Gulfstream officials say. The G650 program is expected to receive certification from the FAA and EASA in 2011. It is on schedule to enter service in 2012.