WASHINGTON - Rep. John Conyers called for further investigation by the Defense Department of McDonnell Douglas' $40 billion C-17 transport plane program, after the failure of one of the company's redesigned wings in a stress test.

Conyers, D-Mich., chairman of the House Government Operations Committee and a critic of the C-17, called the test failure "a profoundly serious event" and said he has asked the department's inspector general to investigate the failure.

The congressman also said he intends to schedule a hearing of the House national security subcommittee about the test failure.

Late yesterday, the Air Force said that the C-17's wing failed to pass a crucial ground test last Friday, after earlier saying the wing appeared to have passed the test.

The Air Force now believes that the left wing failed at a load of about 145 percent of maximum-load limit, below the mandated 150 percent level.

The wings must be capable of withstanding that strain if the plane is to meet Air Force contract requirements and eventually go into full production.

Conyers called the test failure a "powerful and compelling indicator" that the public doesn't know all it should about the plane.

After the failure, the Air Force said it would launch a new monthlong investigation of the C-17's wing design. Left unclear is whether the test failure might lead the Pentagon to walk away from the troubled cargo-jet program or further reduce the order level for C-17s.

Friday's test failure followed a $100 million redesign of the wing, after it failed at 128 percent of maximum load in a test last October.

McDonnell Douglas issued a statement yesterday saying: "We know it was close. We will be unable to claim success until completion of a thorough analysis of test data."

"Prior to the first failure, when we questioned the wing strength, the Air Force sent a general to the committee who informed us repeatedly that `the integrity of the wing is not in question,"' said Conyers. "Well, the integrity of the wing is in question."