UPDATE 1-Boeing says proposed fix would eliminate fire risk on 787

TOKYO, March 15 (Reuters) - Boeing Co said its proposed fix for problems relating to the lithium-ion batteries on its 787 Dreamliner would eliminate the risk of fire, as the company seeks to reassure regulators and the public about the jet's safety and get it flying again.

The aircraft maker said at a briefing in Tokyo on Friday that it would encase the 787 jet's lithium-ion batteries in stainless steel cases, and provide the power pack with extra insulation, spacers and heat-resistant sleeving to prevent overheating.

Boeing also said it has asked Japan's GS Yuasa Corp , which makes the battery for the airplane, and France's Thales SA, which produces the battery system for the aircraft, to improve production standards to eliminate "variation" in battery cell production.

"Because we did not find the single root cause, we looked at everything that could impact a battery and set a broad set of solutions," Mike Sinnett, chief project engineer for the 787 programme, told reporters in Tokyo.

All 50 of the technologically advanced Dreamliners in service have been grounded since January after a battery fire on a Japan Airlines Co Ltd 787 at Logan airport in Boston and a second battery incident on an All Nippon Airways Co Ltd flight in Japan.

Earlier this week, U.S. officials approved Boeing's plan to fix the battery system, starting what could be a rigorous testing regimen. The company also faces U.S. public hearings in April on the safety of its lithium-ion batteries.

Boeing is preparing to start testing a redesigned battery aimed at preventing failures on the Dreamliner.

Boeing has said its proposed changes to the battery and its testing plans are a final fix. Analysts have put the cost of the grounding at about $50 million a week, adding up to $400 million in the past eight weeks.