Engine Woes Could Ground China's Stealth Armada

China's newest stealth fighter prototype is made in the People's Republic and could pose a challenge to U.S. air power. But it's got an Achilles' heel: Its engines are Russian imports.

Without reliable, homemade motors, China's planned stealth armada will continue relying on Russian-made engines that aren't always adequate ' and in any event can be withheld by a wary Moscow.

'China's inability to domestically mass-produce modern high-performance jet engines at a consistently high-quality standard is an enduring Achilles' heel of the Chinese military aerospace sector,' wrote Andrew Erickson, a Naval War College analyst. Erickson chalked up the engine gap to a lack of standardization, cooperation and quality control in Chinese industry.

The new J-21, which apparently hasn't flown yet, first appeared over the weekend in photos snapped at the Shenyang Aircraft Corporation's factory airfield in northeast China. One high-res pic clearly featured the twin-tail fighter's two engines. 'A good early guess is that the engines are Klimov RD-93s,' ace aviation reporter Bill Sweetman concluded.

The RD-93, a derivative of the engine fitted to Russia's classic MiG-29 fighter, also powers China's Chengdu JF-17, a light fighter intended for export. China bought at least 100 RD-93s from Russia starting in 2005. It seems at least two wound up with Shenyang for its new stealth fighter prototype.

Problem is, the MiG-29 was always under-powered, compared to Western fighters. It's impossible to say based on surface appearances exactly how much the J-21 weighs, but it's reasonable to assume it's at least in the same weight class as the twin-tail, twin-engine MiG-29. That suggests the J-21 could be under-powered, too. That usually translates into poor combat performance ' and can have safety implications, too.

Moreover, Russia is not the most reliable source of jet engines. In 2010, Moscow rejected a request by Beijing to purchase Russia's latest AL-41 fighter engine. Experts assumed the PLA wanted the AL-41 to power the J-20 stealth fighter that debuted in leaked Internet photos in December 2010. Instead, the two J-20 prototypes ended up, respectively, with older AL-31s purchased earlier from Russia and Chinese copies of the AL-31 known as WS-10s.

In the meantime, China is reportedly spending $1.5 billion developing the homegrown WS-15 engine ' a rough analogue to the F119 fitted to U.S. F-22 stealth fighters ' to power future versions of the J-20, at least. China will probably take a similar approach with the J-21, Sweetman speculated. The new fighter could make do with inadequate Russian engines until a more powerful motor can be invented in China.

But don't hold your breath. Last year Erickson estimated it would be another five to 10 years before China's inefficient aerospace firms could 'consistently mass-produce top-notch turbofan engines' like the F119.

So no matter how much the PLA tests its J-20 and J-21 stealth prototypes ' and no matter how many copies of the new jets Shenyang and Chengdu's factories churn out over roughly the next decade ' these impressive-looking warplanes could be hobbled by inadequate engines.

Bottom line: for now, America has less to fear from China's planned stealth fighter armada than appearances suggest.