NTSB Factual Report

On October 11, 1998, at 1408 hours Pacific daylight time, a Stearman E75, N770WM, sustained substantial damage following collision with the end of a tractor-trailer truck while trying to return to the Oakland, California, airport following a loss of power after takeoff. The Aerial Advertising Company was operating the banner tow flight under the provisions of 14 CFR Part 91. The commercial pilot sustained minor injuries. The truck driver was not injured; however, a passenger in the truck was transported to a hospital for observation and was subsequently determined to have sustained minor injuries. Visual meteorological conditions prevailed and no flight plan was filed.

The pilot stated he successfully completed three flights in the airplane on the day of the accident. He refueled between the second and third flights, which were both banner tows. The third flight, over the Oakland Coliseum, was only 15 minutes in duration. The pilot returned to base, shut the airplane down, and elected to remain in it while waiting for an aerial demonstration team to complete two passes over the tow area. Once the area was clear the pilot restarted, taxied to runway 33 at intersection L, and completed a modified run-up. He normally checked controls, instruments, gas, trim, radios, and seat belts; then he would run the engine up to check the magnetos, carburetor heat, and cycle the propeller. Since he had flown several flights with no problems, he only did the magneto check. He set the engine at 1,500 rpm, and checked the magnetos. He stated they were smooth, operational, and within limits. The pilot said the engine ran perfect during takeoff and he flew the routine approved pattern. He started a climb of 30 degrees with the power set at approximately 30 inches of manifold pressure, mixture full rich, propeller full forward, then back a little. At 400 feet, he initiated a right 270-degree turn and leveled off. During the level off, power was reduced to 24 inches of manifold pressure. During the turn the pilot heard a pop and the engine stopped producing power. He immediately lowered the nose and headed for the only open area he could see, a concrete pad in a construction area. He pumped the throttle several times and verified that the gas was on.

A road along the airport perimeter ran perpendicular to his flight path. A tractor-trailer truck was moving from the pilot's left to right. The pilot thought the truck would clear before his arrival, but the truck stopped in his path. The pilot was unable to maneuver and the right wing struck the trailer. The airplane pivoted and the engine and propeller struck the back corner of the trailer. The engine separated and the airplane came to rest on a fence.

In a telephone interview the pilot stated he had about 700 hours in Stearman airplanes. During aerobatics, he had heard the engine sputter, but it always came back. Although he thought this accident was a fuel problem, it was not like his previous experiences.

A witness on the ground said he heard the engine running, then heard the sound change to a "dunt dunt dunt dunt" (not a coughing or sputtering sound) noise for 2 or 3 seconds before the engine sounds ceased completely. This witness observed the airplane strike a fence prior to hitting the truck and noted the engine was still quiet and the propeller was not turning.

The operator observed the takeoff and was interviewed by a Federal Aviation Administration (FAA) inspector several days after the accident. He stated the engine quit, then he heard several "blurps" and assumed the pilot was moving the throttle to get the engine to restart. In a subsequent statement, the operator stated he observed fuel coming out of the center section vent line when the nose was lowered for the level off and opined that the pilot may have momentarily entered a negative "g" condition.

The FAA inspector, acting as the accident coordinator, observed fuel in the tanks and lines leading to the carburetor. The fuel filter, oil filter, and fuel shutoff valve were checked and no discrepancies were noted. A functional test of one magneto was satisfactory; the other magneto was damaged and could not be tested. The carburetor was disassembled and no discrepancies were noted. The Safety Board observed a teardown of the engine at Aero-Engines, Inc., in Los Angeles, California, and no discrepancies were found.

NTSB Probable Cause

A loss of engine power due to the pilot's inadvertent entry into a negative 'g' condition, which induced a temporary interruption of the fuel supply.