A Germantown resident was critically injured over the weekend when his ultralight aircraft, a controversial type of motorized glider, crashed in upper Montgomery County.

William Joseph Toland, 33, was in the air less than five minutes Saturday in a borrowed silver Eipper ultralight when it experiencedmechanical trouble and crashed at 5:30 p.m. behind the Germantown campus of Montgomery College, county police said.

Toland was flown by helicopter to Suburban Hospital, where he was in critical condition yesterday after losing a considerable amount of blood.

Toland's family declined to speak about his experience with ultralights, but the planes -- which usually are assembled before each flight -- have become the focus of heated debates over their safety.

Ultralights are the fastest growing segment of the aircraft industry and, while there are no official figures, enthusiasts estimate there are 15,000 of the aircraft in this country.

Responding to the rapid growth of ultralights and to safety complaints about them, the Federal Aviation Administration enacted regulations last week outlining where the aircraft could be flown and the weight limits beyond which they are may not be designated as ultralight.

The new rules require that anyone who flies a plane that weighs more than 254 pounds or has more than one seat must have a pilot's license. No license is needed for aircraft weighing less than 254 pounds.