A series of engine failures in the new-model Piper Tomahawk airplane has prompted the Federal Aviation Administration to ground the aircraft until repairs can be made.

The Tomahawk is a two-seater trainer plane manufactured by Piper Aircraft Corp., Lock Haven, Pa., a unit of Bangor Punta Corp. About 700 of the small planes, introduced last October, are being flown.

An FAA spokesman said there have been two accidents, and possibly, a third, resulting from a failure of the aircraft's power system. One of the accidents involved a fatality, according to the spokesman. Another 40 incidents, the FAA said, have been linked to engine malfunction.

According to the FAA, the cause of the malfunctions has been faulty magnetoes - the small electric generators that provide the spark for engine ignition. Small aircraft generally have two magnetoes in the event one fails, but if both fail an engine will shut off.

A spokesman for Piper said that it was the company that had advised the FAA of the problem and had voluntarily suspended aircraft deliveries. He said that Piper and the suppliers of the affected equipment are thoroughly investigating the exact cause of the magneto failures.

"We are confident of a prompt resolution of the problem and as additional information toward the lifting of the suspension becomes available, we will advise Tomahawk owners, operators, distributors and dealers," said Max E. Bleck, executive vice president of Piper.