Airbus Helicopters (formerly Eurocopter) and China’s Avicopter, partners in thedevelopment of the EC175 and AC352 medium-twin helicopters, signed an agreement last month for the production of 1,000 of the two models. The agreement is valued at $21 billion over 20 years, with each airframer expecting to assemble approximately 500helicopters.

Deliveries of the EC175, which was certified in Europe on January 27, are expected to begin later this year. The AC352, however, has yet to make its first flight and is not expected to earn its certification by China’s civil aviation authority until2017. As previously agreed, Avicopter will sell theAC352 in China, while Airbus Helicopters will sell theEC175 in the rest of the world.

The signing of the production agreement took place at the Elysée Palace in Paris, witnessed by Chinese president Xi Jinping and French president FrançoisHollande.

Airbus Helicopters CEO Guillaume Faury said the agreement would lead to good results for both sides, and “sets the stage for an unprecedented full-scale production framework by both partners and adds a new dimension to the relationship with Avicopter.”

Li Fangyong, executive vice president of the Aviation Industry Corporation of China (Avic), said at the signing, “The production contract’s signature will allow both of us to satisfy the Chinese and worldwide market needs in the medium helicopter segment. This also puts Avicopter’s production resources to work in the aviation industry’s global industrial chain.”

The event was all the more significant because of the prolonged silence by Avic about its work on the AC352 (formerly the Z-15). Both Avic and Avicopter, which is the helicopter business unit of Avic, have reported little about the development of the Chinese version of the EC175 since the original partnership agreement was signed in 2005 with (then) Eurocopter. When asked about the Z-15 over the years, Eurocopter officials typically referred all questions to Avic or Avicopter, which remained unresponsive.

Development work on the design of the EC175/AC352 was shared equally between Airbus Helicopters and Avicopter, capitalizing on the abilities of both companies. In general, Avicopter is in charge of helicopters’ structures, while Airbus manufactures the systems and dynamic parts.

But although the EC175 and AC532 come from a common platform, the two models are reportedly different, although how much different and what the differences are have not been reported. What is known is that Avicopter will assemble the AC352 in China primarily for the Chinese market, and Airbus Helicopters will assemble the EC175 in France for the worldwide market.

Asked about the significance of the announcement last month, an Airbus spokesman toldAINthat the production agreement should be viewed as a “historic ambition” that strengthens the EC175/AC352 program. “The Chinese see this as a way to meet their huge need for helicopters,” he added.