TYPE: Technology demonstrator.

PROGRAMME: Flight trials of Tu-155, a Tu-154B modified with the starboard Kuznetsov NK-88 turbofan operating on liquid hydrogen fuel, began on 15 April 1988; aircraft then modified to use liquefied natural gas (LNG), first flight in this form taking place 18 January 1989. Was world's first aircraft to fly using cryogenic fuels, most of which contained in 17.5 m3 (618 cu ft) tank in rear of passenger cabin.
On 23 April 1994, Russian government allocated funding for conversion of three Tu-154s to Tu-156 standard, delivery of 12 NK-89 turbofans and six cryogenic fuel systems; an installation to supply LNG will be established at Samara. Order reduced to one Tu-156; delivery originally scheduled for 1998, but had not taken place by mid-2003; federal funding of Rb7.5 million and Rb17 million was planned for allocation in 2001 and 2002 respectively to cover construction of a ground test rig for the cryogenic fuel system; total cost of development programme estimated at Rb200 million to 2005, to be funded by Rosaviakosmos (70 per cent), with balance shared equally between Tupolev and Kuznetsov. According to March 2003 report, half the required funds had been allocated to the Tu-156 programme by that time, but the completion date had been further extended.

CURRENT VERSIONS: Tu-156S: Initial kerosene/LNG-powered conversion of Tu-154B, carrying 13,000 kg (28,660 lb) of LNG at rear of cabin and 3,800 kg (8,378 lb) in two underfloor tanks, plus 10,200 kg (22,487 lb) of kerosene in wing tanks; payload 14,000 kg (30,865 lb) or 130 passengers; range 1,403 n miles (2,600 km; 1,615 miles).
Tu-156M: Developed version converted from Tu-154M, carrying 135 passengers; fuel load and performance as Tu-156S.
Tu-156M2: Proposal only; converted from Tu-154M2; 20,000 kg (44,092 lb) of LNG only, carried in two tanks above centre-fuselage allowing passenger load increase to 160; two NK-94 engines; range 2,159 n miles (4,000 km; 2,485 miles).

POWER PLANT: Experimental power plant is 103.0 kN (23,150 lb st) Samara NK-89; tanks for cryogenic fuel mounted in rear of cabin and in forward baggage hold of Tu-156S/M. Aircraft will operate on mixed LNG/kerosene, as Tu-155, kerosene being used for flights out of non-LNG aerodromes and for emergencies, when in-flight switch from LNG can be made in 5 seconds. Tu-156M2 would have only two NK-94 engines, wholly LNG powered.