Sept. 10 (Bloomberg) -- Mitsubishi Heavy Industries Ltd., building an aircraft to rival Bombardier Inc. and Empresa Brasileira de Aeronautica SA in the regional market, scrapped plans for carbon-fiber wings and will use aluminum instead.

The aircraft maker also plans to offer a third variant of the plane with 100 seats, beyond the 78- and 92-seater models already planned, the company said in its September newsletter.

Mitsubishi, which builds the carbon-fiber wings for Boeing Co.’s 787 Dreamliner, said design work showed composites wouldn’t offer the anticipated weight reduction because more material would be needed to strengthen the structures.

Boeing and Airbus SAS have turned to light-weight composites for their latest models, the 787 and the A350, to help airlines save on fuel. The 787, a widebody plane that will also have a composite fuselage, will be 2 1/2 years late when it enters service in 2010, partly because of difficulties with design and manufacturing. The latest delay was to allow engineers to reinforce sections along the wing where the composite layers had separated in ground stress tests.

Mitsubishi’s “updated design will feature an aluminum wing box, which will make it easier to manufacture the optimal wing structure,” the company said in the newsletter. Wing boxes are the sections under the fuselage that hold the wings together.

Mitsubishi is switching to aluminum because it discovered that the weight savings in using composites on wide-body planes aren’t matched on smaller models, spokesman Mick Corliss said in an e-mail responding to questions. Parts of the wing would have to be reinforced if composites were used, adding weight, he said.

Aluminum Advantages

Using aluminum for the wing box will also allow the company to “optimize” that component on its entire family of regional jets more easily, the Corliss said.

Mitsubishi Aircraft President Hideo Egawa said at a news conference yesterday that the plane’s delivery date has now been pushed back by several months to early 2014 from 2013.

Boeing and Airbus, which are both considering building new narrow-body models, currently offer planes starting at about 110 seats.

To contact the reporters responsible for this story: Andrea Rothman in Toulouse, France at aerothman@bloomberg.net; Susanna Ray in Seattle at sray7@bloomberg.net.

Last Updated: September 10, 2009 16:59 EDT