Russian Swivel Nozzle Designs
A great deal of misinformation has appeared on the Internet regarding the relationship of the Soviet Yak-41 (later Yak-141), NATO reporting name Freestyle, to the X-35 and the rest of the JSF program. The Pratt & Whitney 3BSD nozzle design predates the Russian work. In fact the 3BSD was tested with a real engine almost twenty years before the first flight of the Yak.
Throughout the 1970s and 1980s, the Soviet Navy wanted a supersonic STOVL fighter to operate from its ski jump equipped carriers. At what point the Yakovlev Design Bureau became aware of the multi-swivel nozzle design is not known, but the Soyuz engine company created its own variant of it. The Yak-41 version of the nozzle, from published pictures, appears to be a three-bearing swivel duct with a significant offset “kink.” The Yak-141 also used two RKBM RD-41 lift engines – an almost identical arrangement to the Convair Model 200 design. The aircraft was also re-labeled as a Yak-141 to imply a production version, but no order for follow-on series came from the Russian Navy.
The Yak-141 was flown at the Paris Airshow in 1991. The flight displays of the Yak were suspended when the heat from the lift engines started to dislodge asphalt from the tarmac. At the 1992 Farnborough show, the Yak was limited to conventional takeoffs and landings with hovers performed 500 feet above the runway to avoid a repeat performance of asphalt damage. But the Yak-141 does deserve credit for being the first jet fighter to fly with a three-bearing swivel nozzle – twenty-five years after it was first designed in the United States.
During the early days of the JAST effort, Lockheed (accompanied by US government officials from the JAST program office) visited the Yakovlev Design Bureau along with several other suppliers of aviation equipment (notably also the Zvezda K-36 ejection seat) to examine the Yakovlev technologies and designs.
Yakovlev was looking for money to keep its VTOL program alive, not having received any orders for a production version of the Yak-141. Lockheed provided a small amount of funding in return for obtaining performance data and limited design data on the Yak-141. US government personnel were allowed to examine the aircraft. However, the 3BSN design was already in place on the X-35 before these visits.
The 3BSD was invented in America in the 1960s, proposed by Convair to the US Navy in the 1970s, first flown by the Russians in the late 1980s, re-engineered from the 1960 Pratt & Whitney design for the X-35 in the 1990s, and put into production for the F-35 in the 2000s. Sometimes a good idea has to wait for the right application and set of circumstances to come along. One moral of this story is not to throw out good work done in the past. It just might be needed later on.
