Russian energy giant Gazprom's internal carrier, Gazpromavia, is to be the first recipient of the long-range Sukhoi Superjet 100LR, which has just started flight tests.
Gazpromavia will take delivery by the end of 2013 and Sukhoi insists it is on track following the maiden flight on 12 February. The aircraft has been ferried to Moscow Zhukovsky for certification trials and a second will fly later this month.
Sukhoi has designed the 100LR to operate over a 2,470nm (4,570km) range, 50% greater than that of the basic airframe.
The LR will have a maximum take-off weight of 49.5t, compared with 45.9t for the basic. It will also have uprated PowerJet SaM146-1S18 engines, generating an additional 5% thrust and better climb performance. It has the same fuel tanks and the landing gear has not needed strengthening, says Sukhoi.
Sukhoi Civil Aircraft chief designer Alexander Dolotovsky says the wing area is unchanged but its structure has been reinforced. "We strengthened the wing without changing construction materials," he says.
Take-off-and-landing tests are due in March-April and noise pattern tests in April-May. Sukhoi expects certification before the 2013 Moscow air show.
Aircraft 95033 will be the first for delivery, and will come off the line with an interior installed, while 95032 - the test airframe - will remain with the manufacturer for a few months. Sukhoi plans to use it for winglets testing.
"This choice is logical since 032 is the first aircraft to have the strengthened wing," says Dolotovsky. "The winglets can be fitted to both the LR and [basic variant] - but the LR will benefit from them more."
Aeroflot is focused on short-haul domestic services while Mexico's Interjet, having considered the LR, has opted against it. "The increase in take-off weight gives little to them," Dolotovsky says. "Interjet operates from hot-and-high airports, from where even a 46t all-up weight is not always possible." However, there are LR benefits for thin routes into Siberia, such as those operated by Gazpromavia.
Sukhoi is countering the increased weight of the LR's structure - largely comprising aluminium - with a long-term reduction programme, intended not only for the airframe but interior equipment.
It is looking at lighter seats, estimating a potential 400kg (880lb) benefit, with one Russian customer having ordered them. The airframer also hopes LR testing will enable it to revise conservative figures previously submitted to quicken certification.
Emboldened by smoother production, and the shifting of Superjets to several customers, Sukhoi ambitiously wants to pitch the LR against the Embraer 190 - newly certificated in Russia.
Sukhoi's promotional team insists the Superjet has advantages over the Brazilian design, claiming a "better-shaped high-speed wing", nearly 10% smaller than the 190's, and a competitive fuel-burn as a result.
The airframer boasts that the Superjet is "more tolerant" to lower cruise altitudes than the E190, and gives the type's block-fuel consumption at 1.75t per hour - although Russia's Transport Clearing House, which specialises in airline revenue settlement, gave an average figure of almost 2.3t for the Superjet fleet in 2011.
Sukhoi says replacing a Boeing 737-500 with a Superjet results in an absolute fuel-burn reduction of 13-15% on revenue flights.
Efforts to reduce the fuel burn have continued, including weight-reduction measures, being introduced in 2015. Sukhoi insists the deliverable SaM146 engines coming off line are meeting specification.
"When an engine comes to us, we subject it to tests," says Dolotovsky. "So far we have had no claims for inadequate thrust or fuel burn - all supplied engines meet the specification."
Sukhoi is to take back 10 Superjets delivered to Aeroflot between May 2011 and September 2012 because they were issued in a light configuration. While their airframes and systems will undergo some improvement work before delivery to a new operator, the airframer says the powerplants do not need upgrading.
"There is no need to do any work on these engines since they are compliant to the specification," Sukhoi explains.
Sukhoi has recently been working to address technical snags on the Aeroflot fleet, with problems relating to slat deployment and landing-gear retraction.
Four Superjets were grounded for a few days in February to deal with the difficulties, but a gear-door problem on an Aeroflot aircraft on 7 March suggests the matter is not entirely settled. Sukhoi attributed the event to "damage of a throttle drive" in the nose-gear door.
Aeroflot is set to take its first full-configuration aircraft in March, which will feature various improvements including a reworked flight-management system and - already fitted to Yakutia's two Superjets - new passenger cabin ventilation equipment.
Sukhoi aims to produce more than 490 Superjets from 2012 to 2020, a target set by Russian vice-premier Dmitry Rogozin.
Despite slow manufacturing rates for the type, Sukhoi claims it will take the annual production rate to 60 in 2014. It has produced the first aircraft for Asian carriers Lao Central Airlines and Sky Aviation, but the order situation with Indonesian operator Kartika Airlines - which had signed for up to 30 - remains uncertain.
Sukhoi has not recently disclosed firm backlog details for the Superjet, nor the breakdown between those ordering the basic and LR versions.
"The split depends on customer choices, and we certainly have some for the LR," it says.
Sukhoi is also aiming longer-range Superjets at the business sector. VIP charter operator Comlux agreed in 2011 to acquire two Sukhoi Business Jets, delivery of which will take place in 2014. The aircraft will feature additional fuel tanks, to take its range to some 4,000nm.