War Emergency Power - Modern Times

Modern Times

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 Tumanski R-25 engine, which retained the standard 42 / 65 kN normal and forsazh power settings of earlier R-13 powerplants, but added a new super-afterburning system. Use of this "diamond regime" provided a massive 97.4 kN 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 254 meters/second, 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 1 minute, to spare on the engines' 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 MiG-21bis's R-25 engine produced a huge 5 meter 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.