Forum: X-planes

You've got the F-15 S/MTD and ACTIVE, the F/A-18 HARV, the X-31, and the F-16 VISTA. Why were so many testbeds built to explore thrust-vectoring? Wouldn't a single, modifiable version have been good enough?

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I guess they figured that the more airframes they test it on, the more data they'll know about it. They had money to burn, and this new technology was the fire. Should the money have been spent elsewhere? Sure, but were the different designs able to contribute to further production aircraft down the line? Yep, you better believe it.

Without those testbeds on older aircraft, the Air Force could have had to resort to testing on computers--which may not have worked well enough. Also the air force may not have had enough confidence in the technology to put them in a frontline fighter like the F-22.

Not to mention you have 3 different forms of TVC on those aircraft.

S/MTD used 2D nozzles.
F-18 HARV, X-31 used 3 external paddles.
ACTIVE and VISTA used 3D axisymetric nozzles.

The S/MTD 2D nozzles w/ thrust reversers were PW's precursor for the F119's 2D nozzle. Thrust reversers were dropped early in the program.
Think of this as Gen1 TV.

Like was said, the HARV and X-31 used external paddles, and explored 3D vector but more importantly high-alpha, and post-stall maneuvering.
Think of this as Gen2 TV.
http://www.nasa.gov/centers/dryden/hist ... index.html
http://www.nasa.gov/centers/dryden/hist ... index.html

ACTIVE and MATV/VISTA used 3D nozzles incoporated into the design of the engine's existing nozzle, it was the culmination of all the previous experience with TV.
Think of this as Gen3 TV.

Note both GE (AVEN) and PW (P/YBBN) had engines in the MATV/VISTA program.
http://www.nasa.gov/centers/dryden/hist ... index.html
http://www.flightglobal.com/pdfarchive/ ... 01349.html
http://www.codeonemagazine.com/archives ... 2a_94.html

Keep 'em flyin' Thumb

TEG

ptplauthor wrote:

I guess they figured that the more airframes they test it on, the more data they'll know about it.

For that matter, it wouldn't matter if they all had the same thrust vectoring configurations too- they would all probably perform differently anyhow. Either way, more info is of benefit to the whole program in the long run.

Also, out of all of those aircraft, only one was originally built with a TV engine.

Different aircraft and different engines, will have different flight envelopes, and will produce different test results. Also, those 3 modified fighters were testing different profiles.

Hopefully, Roscoe could chime in on this one, as he would have the best insight.

All aircraft had differents target mission. F-18 HARV was used to evaluate High AOA with padles as a low cost alternative. But three aircraft were in compettion before NASA selected this aircraft. They were F-18,F-14 and F-15 due to the fact that all this three aircraft alraedy get to AOA as High as 90° during operational flight testing. The F-15 Active was chosen because its main goal was to explore high supersonic/high altitude use of TVC were it was easy to him to attain very high speed. The X-31 was an experimental aircraft to explore "Supermaneuverability" from DrHerbst Thesis. Costs have also to be taken into account as the lenght on any such programm to achieve goals. NASA can't afford to use only extremely costly fighters such as the F-15 to do research that don't calls for such a high performance aircraft.

Sorry I forgot F-16 MATV(previously known as VISTA) that's used primarily to emulate other aircrafts charateristics (as was done before by a modified T-33) trough its adaptive filght control system, which is a testimony to the works done by Lockheed engineers.

Sorry big mistake. F-16 VISTA(previously known as MATV)

Forum: X-planes

Why so many TVC testbeds?