Despite crash of prototype, Spectrum forges ahead on VLJ

NBAA Convention News » 2006
November 7, 2006, 4:30 AM

Spectrum Aeronautical (Booth No. 2142) continues to develop its Model 33 VLJ following the fatal crash of its sole prototype on July 25. In recent weeks the company has buttressed its engineering staff with new hires and is proceeding with the design and building of a conformal test article that will fly “in about a year,” according to Austin Blue, Spectrum’s president. Blue also revealed that the company has entered into discussions with several air-taxi companies and will begin taking orders here during the show, where it has a full cabin mock-up with a complete interior on display.

Blue also said that Spectrum had selected Avidyne as its avionics provider. “We’re confident that its system will meet our certification goals and requirements,” he said. “We think it is the best there is in this class of airplane.”

But the crash will delay the program. Blue now estimates aircraft certification and initial customer deliveries, originally planned for 2008, will slip to 2009 with a first-year production rate of 12 aircraft.

The $3.65 million (2005 $) Spectrum will seat eight passengers and two pilots, have an unrefueled range of 1,560 nm and a cruise speed of 415 knots. The airplane’s lightweight FibeX carbon fiber construction uses a proprietary method of grid stiffening, as opposed to honeycomb reinforcement. The company claims the process produces a strong and lightweight fuselage, with the highest power-to-weight ratio in its class. This allows the Spectrum 33 to take off from very short runways and post impressive climb rates. On its first flight on January 6, the Spectrum lifted off in just over 750 feet. On subsequent test flights the aircraft achieved a climb rate “in excess” of 5,000 fpm. Spectrum claims that the Williams FJ33-4 engines that power the aircraft will deliver fuel economy similar to that of the much smaller Eclipse 500 VLJ.

The crash of Spectrum’s proof-of-concept (POC) aircraft, at Utah’s Spanish Fork Airport, killed company test pilots Glenn Maben and Nathan Forrest. An examination of the wreckage by the NTSB confirmed initial reports that the likely cause of the crash was a rigging error in the translation linkage “such that left roll input from the sidesticks would have deflected the ailerons to produce right roll of the airplane” and vice versa. Before the crash, the aircraft had undergone modification. Stiffening of the main landing gear legs necessitated a redesign of the aileron upper torque tube V-bracket. Installing the bracket required the removal and reinstallation of a portion of the translation linkage.

Blue took issue with some early media reports on the crash. “The airplane did not cartwheel and it did not catch fire,” he said. “The wingbox stayed intact. The outboard third of the right wing sheared off and the airplane landed upside down because of the momentum of the roll.”

Blue said that although Maben and Forrest were accomplished aerobatic pilots, they could not have avoided the crash. “They had about two seconds to figure it out and correct it,” he said.

While Blue said the crash was not caused by the aircraft’s design, certain changes are anticipated on the conformal aircraft. Among them, he said, will be “slight aerodynamic changes” that include substituting a trimable horizontal stabilizer rather than the stabilizer on the POC aircraft. “We thought we might have needed the stabilizer for extra rotation power, but that turned out not to be an issue,” Blue said. He also said the control linkage system will be redesigned to eliminate the possibility of future installation errors and that Spectrum was working on minor changes in the layout of various systems and controls.

Blue said Spectrum acquired valuable data that validated many design assumptions from the POC aircraft before the crash over the course of 47 flights and 50 flight hours between January and June. The airplane was flown to 324 knots at 25,000 feet. Blue said the prototype demonstrated good fuel economy and drag “within 4 percent” of design goals. He also noted that c.g. limits were within the predicted range. Rotation speeds were 70 to 75 knots and single-engine yaw was low.

Despite the July crash, Blue reported that interest in the Spectrum 33 remains high. “The good fuel economy and large cabin are going to make a profound operational difference for people who want to operate these on a fleet basis,” he said.

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