Former senator John G. Tower (R-Tex.) and his daughter were among 23 persons killed yesterday when the twin-engine commuter plane they were aboard crashed while trying to land at an airport in Brunswick, Ga., authorities said.

Astronaut Manley Lanier "Sonny" Carter Jr., who flew on a 1989 space shuttle mission and was in training for a shuttle trip later this year, also died in the crash. No passengers survived.

The crash followed by one day the plane-helicopter collision that took the lives of Sen. John Heinz (R-Pa.) and six other people. The collision over a Philadelphia suburb occurred when the helicopter crew was attempting a second airborne check of the plane's landing gear, despite already verifying that it appeared to be working, investigators said. {Story, Page A8.}

Tower, 65, and his daughter Marian, 35, boarded the 30-passenger, turboprop Embraer 120 in Atlanta and were headed to Sea Island off the south Georgia coast for a party in Tower's honor scheduled for last night and to be hosted by the literary agent who worked with him on his recent book, "Consequences: A Personal and Political Memoir."

Federal officials investigating the crash said they did not know the cause. Flight 2311, an Atlantic Southeast Airlines commuter flight, was descending in clear weather with visibility of about 7 miles, according to authorities, when it went down at 2:47 p.m. in a wooded area about three miles northeast of the runway at the Brunswick/Glynco Jetport, a former Navy base with a 10,000-foot runway.

Witnesses said the plane appeared to have fallen straight down from the sky. "It just went straight down, there was no cropping of trees," said Lt. Jack Hopper of the Glynn County Police Department, quoting witnesses at the scene.

"It started in on its nose, and I knew it was in trouble," James Griner, who lives about a quarter of a mile from the airport, told the Associated Press. "I went to the plane but I couldn't get to it because of the fire. . . . When I got to it, it looked compacted; it was a mess."

A conservative who served as chairman of the Senate Armed Services Committee during the Reagan military buildup, Tower saw his long political career in Washington all but end in 1989 after President Bush nominated him to become defense secretary. The bitter confirmation fight that ensued spawned numerous allegations of questionable drinking and social habits, and the Senate rejected him on a 53 to 47 vote.

Tower's death prompted words of grief and praise among his former colleagues on Capitol Hill, even those instrumental in scrapping his elevation to the Cabinet.

"I'm deeply saddened by the loss of John Tower, a tough, able friend and patriot," said Sen. Lloyd Bentsen (D-Tex.), who broke ranks with most Democrats to support Bush's nomination of the 24-year Senate veteran to the post. "He was intelligent and had independence of judgment."

Senate Armed Services Committee Chairman Sam Nunn (D-Ga.), who led the successful fight against Tower's confirmation, said, "America has lost a patriot. . . . He fought for freedom and worked diligently to make the world more secure."

"It's so sad," Bush said upon learning of Tower's death. "It is a tragic loss."

Donald Day, manager of consumer affairs for the Atlantic Southeast Airlines, said that Tower, his daughter and Carter were aboard the plane. Company officials declined to release the names of the other passengers and three crew members.

Day described the aircraft as "extremely sophisticated and fuel efficient, one of the backbones of our commuter fleet." He said the plane involved in the crash was a new aircraft that had been put in service in December.

The Brazilian-made Embraer 120 is manufactured by Empresa Brasileira de Aeronautica SA and can reach a maximum cruising speed of 320 mph at 22,000 feet.

Last April 10, an Embraer 120 of the same airline was involved in an airborne collision with a smaller plane over Alabama. Two pilots aboard the second plane were killed, but the Atlantic Southeast commuter landed safely at the Gadsden, Ala., airport, with a damaged tail section.

In 1984, an earlier model, the Embraer 110 Bandeirante, crashed in Jacksonville, Fla., killing 13 people. The Federal Aviation Administration subsequently ordered an extensive inspection of all Embraers in the country for possible sheared or worn rivets in the tail sections.

In 1987, an Embraer 120 operated by Air France crashed while preparing to land at an airport at Bordeaux, killing all 16 passengers.

At the crash scene yesterday, Bill Kitchen, a reporter for WMOG radio, said, "Literally all that's left of the plane is the tail and a clump of metal where the cockpit used to be."

Glynn County Police Chief Carl Alexander said the Georgia Forestry Department bulldozed a road into the crash site. A temporary morgue was set up at the site.

Staff writers Barbara Vobejda and Helen Dewar contributed to this report.