The GM-17 Viper project is in serious jeopardy following several recent developments. The GM-17 is a modified Piper P Navajo on which the two wing-mounted 425-hp piston engines are replaced by a single 750-shp Walter M601E turboprop placed in the redesigned forward fuselage.

The Tekhnoavia design house and Smolensk aircraft production plant, both based in Russia, have sent Russia’s Rosaviacosmos state agency a letter informing the authorities about their decision to withdraw from the project and appealing for the grounding of the two prototypes because of flight-safety concerns.

The move follows the companies’ dispute with Intracom General Machinery of Switzerland–which launched the program in 1998–over payment issues spelled out in the initial contract signed by the three entities in March 2002. The Russian firms said they fulfilled the terms of the contract but did not get paid by Intracom as agreed, while the customer demanded they carry on with the work and achieve Russian certification of the GM-17.

Tekhnoavia general director Slava Kondratiev, the acting GM-17 chief designer, told AIN that the contractual terms did not call for certification. At any rate, certification cannot be achieved using the two experimental aircraft, he said. The two prototoypes were produced in Smolensk under Tekhnoavia supervision from PA-31P airframes supplied by Intracom.

Kondratiev said FAR Part 23 and Russian AP-23 certification would be impossible because the Piper P Navajo is an old design that does not meet current certification standards; Piper did not support the project, so no documentation is available; and the available tools to assess the airframe without Piper’s participation weren’t used.
The motive for Tekhnoavia to join the Viper project was purely financial, Kondratiev said, while “I never had illusions over [the design’s] future.” He said the use of two old PA-31P airframes seemed reasonable for the purpose of assessing the modified aircraft’s performance before making a decision on a full-scale redesign of the original airframe in Russia and setting up the Viper production line in Smolensk. Under earlier plans, Viper deliveries were expected to begin next year.

Assessment of the two P Navajo airframes, both of which were constructed more than 25 years ago, showed heavy corrosion in both the structure and skin, along with several cracks and high wear-and-tear. “It is impossible to guarantee flight safety under these circumstances, so I grounded the aircraft after a short flight-test program,” Kondratiev said.

The two experimental Vipers have an operating empty weight of 5,094 pounds, 804 pounds lighter than an unmodified PA-31P, and an mtow of 8,847 pounds. The Viper’s pressurized cabin accommodates six passengers at altitudes up to 20,000 feet, at which the aircraft, with a 40-minute fuel reserve, has an estimated range of 972 nm with a 1,287-pound payload at 216 knots.