Singapore Air Show

Fresh power for Indian, Chinese jets

 - November 30, 2006, 10:54 AM

Both China’s J-10 fighter and the Indian air force Bakhadur MiG-27ML fighter bomber are set to be re-engined with two new variations of the Russian Salyut AL-31FN engines–the AL-31FN M1 and the 99-3, respectively.

India is considering the retrofit for the entire Bakhadur fleet. The final decision is expected upon completion of an initial flight-test program on a MiG-27M, which MiG promises to fly early this year. The 99-30S engine is similar to the AL-31FP already powering India’s Su-30MKI twin-engine fighter.

“The R-29-300 engine on the MiG-23 and MiG-27 is outdated. To extend the lifetime of these types and reduce operational costs, we are offering retrofitting with AL-31FN,” explained RSK MiG general director Aleksei Fedorov.

The Chinese are further down the road on the re-engining. In late 2005 China placed a $300 million order for a second batch of AL-31FN engines. The first batch was for 54 basic AL-31FNs. These were supplied in 2001-2002 and since then have flown on development prototypes and initial production J-10s. The new Super-10 version of the fighter, effectively representing a production version of the J-10, will be powered by AL-31FN M1.

To accommodate the new engine and other changes, the J-10 airframe is being reworked with help of RSK MiG consultants. Historically, the aircraft was conceived as a Chinese copy of Israeli Lavi powered by Pratt &  Whitney PW1120 turbofans. The Russian engine is 20 percent heavier and needs 40 percent higher air flow.

Salyut assembled a handful of AL-31FN M1s in late 2005 for bench testing. Salyut general manager Yuri Eliseev told Aviation International News the M1 differs from the initial AL-31FN in its enlarged fan, with inlet diameter of 36.4 inches instead of 35.5 inches. At full afterburner it produces 29,760 pounds of thrust compared to the earlier model’s 12,500 pounds.

Swivel Nozzle

Another innovation of the M1 variant is a swivel nozzle developed jointly with Klimov. It features the “Klimov vectored thrust” (KliVT) design, already tried on the RD-33OVT engine that powers the MiG-29OVT vectored-thrust demonstrator. Unlike the similar NPO Saturn pitch-only nozzle on the Su-30MKI, the new one deflects in pitch and yaw planes. It has been certified for a lifetime of 750 hours before removal, and 1,000 hours of testing are under way.

The enlarged fan and the swivel nozzle were flight tested on Su-27 test beds. These and other test beds are employed in AL-31FM/N state acceptance trials with the Russian defense ministry, including certification for time-between-overhaul (TBO) of 1,000 hours and an assigned lifetime of 2,000 hours.

Salyut is further developing the AL-31FN, and plans to start bench testing on the M2 version early this year. It will have a new HP turbine that sustains higher temperatures.

Then, in late 2006, the M3 will follow with a new combustor and redeveloped LP compressor. This will also have a three-stage “blisk” wide-chord design (the AL-31F has a four-stage LP compressor) with pressure ratio increased from 3.65 to 4.2. The AL-31M3 will produce 31,966 pounds of thrust at full afterburner. If the program succeeds, the Russian engine should match the performance of the GE F110-132 turbofan that powers Lockheed Martin’s F-16 Block 60 Desert Falcon.         –V.K.