Passage: The TB-3 was an all-metal aircraft of steel construction, as one of the designs from Andrei Tupolev's design bureau to be based on the 1918-onward all-metal aircraft design practices and technology pioneered by Hugo Junkers. The frame was composed of V-section beams covered with non-stressed corrugated skin ranging from 0.3 mm (1⁄64 in) to 0.8 mm (1⁄32 in) in thickness. The corrugations were 13 mm (0.51 in) deep and 50 mm (1.97 in) apart. The cantilever wing was supported by four tube-section spars. In 1934, thanks to the development of stronger steel alloys, the wingspan was increased from 39.5 to 41.85 metres (129.6 to 137.3 ft) with a concurrent wing area increase from 230 to 234.5 m2 (2,476 to 2,524 sq ft). Any part of the aircraft could be walked on in soft shoes without damaging the skin, and the leading edges of the wings swung down to form walkways for engine maintenance. Controls were cable-actuated with a variable-incidence tailplane and a trim compensation system in case of engine failures on one side. Fixed main landing gear was not fitted with brakes. The fuel tanks did not have fire or leak protection, although the engines had an internal fire-extinguishing system. The M-17 engines were tuned to provide a maximum theoretical range of 3,250 kilometres (1,750 nmi; 2,020 mi) without spark plug or carburetor fouling. Defensive armament consisted of light machine guns in five turrets — one in the nose, two on top of mid-fuselage, and one retractable "dustbin" under each wing between the engine nacelles. Later variants moved one of the top fuselage turrets aft of the tail fin.

Question: How many sides of the engine fail that made a trim compensation system be built?
one