JayS wrote:^ I may be totally wrong but, My understanding is LM bought data from Yak such as expt, real life performance data etc. Thats definitely worth hundreds of millions if the quality of data was good, we will never know. That must have reduced a lot of work for LM, if so. Having an idea, a concept or a patent of something mean zilch, what matters is actually designing it, making it and deploying it in real life successfully.
Lockheed's work with YAK was about taking the nozzle and seeing if they could fund a quick but substantial flight test program on YAK so they could go to the selection committee and provide them with real hard data on performance and reliability since the although the nozzle design dates back to Pratt's work from the 1960s their competitor (s) were proposing much simpler and tested Thrust Vectoring solutions. Boeing's approach actually was similar to what Lockheed did on the F-22A when it came to rear nozzle thrust vectoring.
One oft ignored element of Lockheed's design was the amount of risk they were taking with an end goal of providing a clearly superior STOVL configuration. The lift fan approach and the clutch was totally untested in prior DARPA or service run programs and the nozzle, although bench tested had never been put into a flying prototype or technology demonstrator in the US. MCD for example stuck to what had been designed, bench tested and studied before i.e. the Convair/YAK approach of sticking a lift engine up front and an engine int he rear that vectored to assist in generating additional lift. That Lockheed executed the STOVL portion of the flight testing of the X-35 near flawlessly including the Hatrick was remarkable from a design risk standpoint.
Quite a contrast from Boeing's challenges that involved actually removing physical hardware from he aircraft to demonstrate a vertical landing, and of course their fudging up in the design phase where they concluded the X plane program with a different wing to what they proposed in their final submission (which although technically allowed but wasn't a sign of confidence or design maturity). Even Boeing recognized Lockheed's lift fan appraoch as being a key factor in their victory. Quite unusual to come out and attribute and recognize something ..
As the CodeOne article mentioned, the design similarity between the two is in regards to the nozzle in the back. A nozzle that Pratt&Whitney designed, tested and patented in the late 1960s, something the Russians flew on the YAK-141 and something that Lockheed operationalized with the F-35B.
IF you are interested, and have time here is a video lecture from the guy who led the effort on the patented lift appraoch -
@ Negi, you may want to watch from here as a comparison to the YAK and what MCD proposed (and how it differs from Lockheed's approach) - https://youtu.be/u-cfy-k_8ew?t=3071
Realize when the Lockheed lift concept originated and when they reached out to YAK. The SST was years earlier, and so was the CALF design which brought forward the propulsion concept designed earlier on the SSF. Lockheed pitched the propulsion concept to DARPA and was selected in 1993. SST was prior to this. Lockheed reached out YAK only a few years later once their basic design concept on propulsion had been sealed.
Lockheed started working on and proposed this lift fan concept in 1987. and had a mature concept that they presented to DARPA and the USMC based on which they were given additional funding for the CALF and later JAST. Had Lockheed wanted to copy YAK, they would have, upon being given access to YAK in 1995, simply ditched their own STOVL approach, stuck a pair of engines in the front and a big thrust vectoring engine in the rear. This was what YAK did. But no, there wasn't a single design element that Lockheed changed from the concept it began working on in the 1980s to when the flew the X-35 . The aircraft around the propulsion concept morphed to meet the requirements laid out by the operator, but the propulsion concept was never really substantially altered.