Story ID: DP 12_6 SLON
SLON Strategic Airlifter Enters Tunnel Testing
By: Vladimir Karnozov
Caption: Russia’s strategic airlifter program is advancing into validation of the advanced wing, while Ukraine is hoping to re-launch production of the An-225.
Word Count: 582
Wind tunnel tests have commenced on a scale model of the SLON strategic airlifter at TsAGI (the local acronym for the Central Aero-hydrodynamics Institute), which is leading the aircraft's development under a contract from Russia’s ministry for industry and trade. The tests are three months behind the original schedule.

The move follows the release in November of photos of the model. In a press statement that accompanies them, TsAGI said that the aluminum and steel model weighs 120 kg (265 pounds), and has a length 1.64 meters (5 ft, 5 in) and a wingspan of 1.75 (5 ft, 9 in), which gives a scale ratio of about 1:50.

Explaining the delays, the institute noted that “the most labor-intensive work” was required to produce “a very sophisticated 3D shape of the wing,” which is meant to ensure high aerodynamic qualities at typical cruise speeds. TsAGI plans to complete initial testing in the T-106 wind tunnel by the year-end, and proceed to the assessment of aerodynamic performance at takeoff and landing in the T-106 and T-102 tunnels during 2020.

In addition to some figures in the aircraft specification released in early 2019, when the aircraft’s concept and main features of its force-bearing structure were determined, TsAGI added that the SLON will be able to operate from 3,000-meter (9,842-ft) runways.

Official sources insist that the SLON is being developed as a replacement for the Antonov An-124 Ruslan, currently the main strategic airlifter type in Russian Air and Space Force (VKS) inventory. However, its maximum payload (180 tonnes versus 120) and its payload-range capabilities appear to match those of the An-225 Mriya, of which just a single example was built in 1985. According to TsAGI, the SLON will be powered by four PD-35 turbofans, jointly producing 140 tonnes (308,642 pounds) of thrust at takeoff. The figure is close to that for the six Ivchenko-Progress D-18Ts of the Mriya.

The difference in fuselage length between the two types is within five feet, and that in wingspan is 20 ft (270 ft for the SLON and 290 ft for the Mriya). A wide application of modern construction materials will make the SLON’s structure some 30 percent lighter, at 214 to 222 tonnes (472,000-490,000 pounds) compared to 285 tonnes (628,000 pounds) for the An-225.

Back in 2016, the Ukrainian Antonov company signed an agreement with the Airspace Industry Corporation of China (AICC) to launch the An-225 into production on Chinese soil. Implementing this plan could be facilitated by the planned acquisition of the D-18T engine manufacturer Motor-Sich by Beijing-based Skyrizon Aviation, which purchased a 41 percent stake in 2017 and is now seeking permission from the Ukrainian authorities for outright ownership. The investor is promising a $250 million cash injection into the modernization of the existing facilities in Zaporozhie. It is part of a larger effort to expand production of Ukraine-designed engines, which also involves establishing an assembly and servicing plant in Chongqing.

While both deals remain in doubt, Moscow appears to be making efforts to offer Beijing an alternative, centering on new aircraft designs powered by the PD-35. Should the engine prove successful, it will serve as the key to future Sino-Russian joint programs in aviation. Apart from the SLON, this next-generation turbofan is being developed by Perm-based Aviadvigatel for the COMAC/UAC CR929 passenger airliner and a twin-engine version of the Ilyushin Il-96. To facilitate service-entry for the new engine and streamline its production, the Kremlin is considering a contract for PD-35-powered Il-96s in VVIP, flying command post, and air tanker versions.