The pilot and copilot of Northwest Flight 255, which crashed last August less than 30 seconds after taking off, apparently skipped an entire preflight checklist that contained a reminder to set the plane's flaps.

A transcript of the pilots' cockpit conversation, released yesterday by the National Transportation Safety Board, shows that none of the items on the "taxi" checklist was called out. The taxi checklist ordinarily would have been completed while the plane taxied out to the end of the runway.

Investigators have said the plane took off with its flaps improperly set, which prevented the plane from gaining proper lift. The plane began stalling eight seconds after leaving the runway and was airborne for only 22 seconds before it crashed.

The Aug. 16 accident at Detroit Metropolitan Airport, which killed 156 people, was the second worst in U.S. aviation history.

In addition to the analysis of the cockpit voice recorder, other tests conducted by the NTSB confirmed that a computer voice warning that the flaps were improperly set did not sound. If the alarm had been working, the voice would have loudly said, "Flaps. Flaps."

The test results, released by the NTSB without comment, reinforced speculation that a circuit breaker to the alarm system had been pulled on an earlier flight.

Immediately after the crash, investigators speculated that the crew completed part of the preflight checklists but had become distracted by reports of windshear in the area and directions by air traffic controllers to a new runway.

The McDonnell Douglas MD-80 has several short preflight checklists of procedures and equipment switches to be set. The transcript shows the crew completed at least two of the lists. While the plane was at the gate, the crew performed the "before start" checklist (such items as ignition, electrical power, air conditioning and brakes). The crew also performed the "before take-off" checklist (altitude indicators, ignition) when they arrived at the end of the runway.

But in the intervening nine minutes, while the plane was taxiing to the end of the runway, no "taxi" checklist items were called out.

Instead, Capt. John Maus carried on a brief conversation with a flight attendant about the number of passengers on board. Then, Maus and copilot David Dodds talked about the bad weather, which had delayed their flight, and other planes in the area.

The flaps should have been set at 11 degrees during the taxi checklist, according to investigators. The plane's flight data recorder showed the flaps were retracted to zero.

Once the plane was rolling down the runway, Maus noticed the thrust computer indicator (TCI), an instrument that sets the automatic throttle, was not set. That instrument should have been set while the crew performed the taxi checklist, according to sources close to the investigation.

The transcript shows that Maus attempted to push the throttle forward, but that it would not stay in place:

"It won't stay on," Maus said.

"Won't come on?" Dodds replied.

"But they won't stay on."

"Okay, power's normal."

(Sound of two clicks.)

"TCI was unset," Maus said.

"Yeah. Can you get 'em now -- there you go. They're on now. Clamp. Hundred knots."

(Sound of laughter.)

Five seconds later, the stall warning begins to sound.

There is no indication that Maus or Dodds knew what the problem was before the crash, and there is no mention of the flaps in the transcript.

John Mazor, a spokesman for the Airline Pilots Association, cautioned that the transcript does not tell the full story of the accident.

"It is entirely possible that those things were checked, but nothing was vocalized," he said. "I'm not saying it did happen. The absence of hearing the call out on the tapes does not mean that the item was not checked."

Northwest has been declining comment on aspects of the crash while the investigation continues.

The stall warning sounded four times before the plane hit. It appeared that one of the crew members recognized the plane was in trouble and tried to change the pitch of the airplane. According to the transcript, the final moments of the flight included:

(Sound of stall warning.)

"Right up to the vee bar," said one of the crew.

(Sound of stall warning.)

"Ah, {expletive}," said one of the crew.

(Sound of stall warning.)

Four seconds later, the plane hit the ground.

The last sounds picked up by the cockpit's microphone indicate that the plane hit seven times before breaking up on a highway.