provided extreme power benefits of 25 to 30 percent at high altitude by adding oxidizer gases but required cooling on the ground and, like the MW 50 boost system, added significant weight. One of the few German aircraft that could be equipped with both Notleistung systems, the late war Focke-Wulf Ta 152H high-altitude fighter, could attain a velocity of some with both systems used together. Kurt Tank reportedly once did this, using both boost systems simultaneously when he was flying a Junkers Jumo 213E-powered Ta 152H prototype fitted with both MW 50 and GM-1, to escape a flight of P-51D Mustangs in April 1945. Modern times MiG-21 Perhaps the most dramatic WEP feature was found in the MiG-21bis fighter jet. This late variant of the standard Soviet light fighter plane was built as a stopgap measure to counter the newer and more powerful American F-16 and F/A-18 fighters until the next-generation MiG-29 could be introduced to service. The MiG-21bis received the upgraded Tumansky R-25 engine, which retained the standard normal and forsazh power settings of earlier R-13 powerplants, but added a second fuel pump to supply the new super-afterburning system with jet fuel. Use of this "diamond regime" provided a massive of thrust for no more than 3 minutes in actual wartime use. Use of this temporary power gave the MiG-21bis slightly better than 1:1 thrust-to-weight ratio and a climbing rate of , equalling the F-16's nominal capabilities in close-quarters dogfight. In air combat practice with the MiG-21bis, use of WEP thrust was limited to one minute, to reduce impact on the engine's 800 flight hours lifetime, since every second of super-afterburner use counted as several minutes of regular power run due to extreme thermal stress. When WEP was on, the R-25 engine produced a huge long blowtorch exhaust - the six or seven brightly glowing rhomboid "shock diamonds" visible inside the flames gave the emergency-power setting its "diamond regime" name. F-15C The Vmax switch on the F-15 fighter jet allows the engines to burn 22 degrees hotter and about 2 percent more revolutions per minute. It is safety-wired shut. During combat, pulling the Vmax switch would provide the pilot with a little more thrust. However, the engines would then need to be serviced and rebuilt. WEP in surface vehicles Some modern military surface vehicles also employ WEP features. The US Marine Corps Expeditionary Fighting Vehicle (cancelled in 2011) sported