Resumption this month of the Ilyushin Il-112 airlifter’s flight test program might help resolve the long-standing problem of poor reliability of the Klimov TV7-117 series engines and thus save another Ilyushin design, the 68-seat Il-114-300 passenger turboprop.
Both airplanes rely on the Klimov TV7-117ST01, which produces 3,600 hp and drives a pair of six-blade Aerosila AV-112 propellers, both controlled by BARK-65SM Fadec system. The combination appears to have led to reliability troubles experienced by prototype aircraft.
The Il-114-300 took to the air for the first time on December 16 with Ilyushin chief test pilot Nikolai Kuimov at the controls. Testing went well until February 5, when Kuimov had to abort a flight test and perform an emergency landing on one engine. The crew shut down the second engine after sensors sounded an alarm for excessive temperature in the oil-air heat exchanger.
That incident marked the second case of a malfunction with the propulsion system. On March 30, 2019, when the Il-112 made a 45-minute inauguration flight, a number of cameramen caught on video the right propeller rotating markedly slower than the left on approach and landing. Klimov and his superiors insisted the aircraft performed well, but later admitted “a failure in automatics” caused the difference in the engines’ RPM.
For almost two years the only Il-112 prototype stayed idle at the VASO plant in Voronezh, where it had been built. On March 19 the aircraft began making ground runs in preparation for a ferry flight to Zhukovsky near Moscow, the location of the Ilyushin test base. The latter also serves as home for the only Il-114-300 prototype, which is a rebuild of the Il-114-100 s/n 91003. Now bearing s/n 54114, the aircraft sports new wing consoles and other airframe parts supplied by RAC MiG’s plant in Lukhovitsy, where the Il-114-300 assembly line is under construction. Previously, about 20 early-version Il-114s underwent assembly at the TAPO factory in Uzbekistan’s capital city of Tashkent, which ceased aircraft production in 2012.
In explaining why the Il-112 remained grounded for almost two years, Ilyushin points to the lengthy repairs of the VASO aerodrome. At the same time, the Russian defense ministry, acting as the main funder and customer for the program, said the prototype’s structure had gone overweight by two tons. Along with engine shortcomings, the conditions could cause prompt the ministry to cease funding.
All this puts Ilyushin in a difficult situation with both turboprop projects. Even though the Il-114-300 development receives funding from a different main source, that being the ministry for industry and trade, the limited budget does not allow for additional funding for resolving the powerplant’s teething problems. Unless the military pays extra for TV7-117ST01 maturation on the Il-112, the engine may appear unsuitable for passenger transportation.
Development of the TV7-117 series began in Soviet times. Early production variants appeared faulty, leading Il-114 launch customer Uzbekistan Airways to switch to the Pratt & Whitney Canada PW127. Klimov tried to reinstate itself in 2002 with the improved TV7-117SM, which powered Vyborg Airlines Il-114s that experienced engine shutdowns before the airline ceased operations in 2010. The TV7-117ST01 represents another effort to improve reliability. The manufacturer calls the TV7-117 “an example of a competitive indigenous engine, with the scientific-technical level exceeding that of foreign analogs.” Compared with the contemporary PW127M, it shows 2.5 percent lower specific fuel consumption and a 3 percent better power-to-weight ratio, Klimov adds.