NTSB Factual Report

On May 22, 2005, at 1554 Pacific daylight time, a Classic Aircraft Corporation Waco YMF-5, N181AS, lost engine power during the takeoff initial climb and collided with terrain at Santa Barbara, California, while attempting a return to runway maneuver. Santa Barbara Biplane Tours operated the airplane as a local area scenic for-hire flight operating within 25 miles of Santa Barbara under the provisions of 14 CFR Part 91. The airline transport rated pilot and two passengers received minor injuries. The airplane was substantially damaged. Visual meteorological conditions prevailed and a company flight had been filed.

The airplane was departing runway 15L. During the initial climb, about 175 feet above ground level, the pilot declared a "Mayday" and attempted to reverse course back to the runway. The airplane came to rest in a slough next to runway 33L.

On May 31, 2005, a post accident examination of the airplane and engine was conducted by National Transportation Safety Board investigators. The magnetos were examined. The magneto points gap on the right magneto was found to be 0.026 inches and 0.036 inches on the left (the Jacobs R755 A2/B2 Operator's Manual specifies a points gap of 0.010 to 0.014 inches, and preferably 0.012 inches). The right magneto showed signs of points contact burning and of heating due to a lack of periodic oiling. Both magnetos were missing the spring-loaded oil cup at the base of the magneto. Magneto timing to the engine was checked and found to be 36 degrees Before Top Dead Center (BTDC) for the right magneto and 27 degrees BTDC for the left magneto (the operator's manual specifies 31 degrees BTDC for both magnetos). Both magnetos were then removed from the engine and spun by hand on a bench to check for sparking. Both magnetos threw sparks from the rotating cylinder to the housing, but the right magneto sparked excessively (arcing), indicating a possible failed condenser. Review of the engine logbook disclosed that the last oiling of the magnetos occurred at a tach time of 265 hours (about 200 hours prior to the accident), and the last contact points adjustment occurred at the last overhaul (466 hours prior to the accident).

On June 2, 2005, the magnetos were taken to a radial engine shop for a formal magneto bench test run of the magnetos. The left magneto had a strong spark, whereas the right magneto displayed a weak coil, failing as the magneto got warm.

A sampling of cylinder base hold down nut torques was performed. According to the overhaul manual the torque should be 250- to 300-inch pounds. Three of the four nuts were torqued beyond 360-inch pounds. The other front nut was 275-inch pounds. Of the five rear nuts checked, one was below 250-inch pounds, three were between 250- and 300-inch pounds, and one was beyond 360-inch pounds. According to the engine logbook the last retorque of cylinder base nuts was done at 407.38 hours, about 60 hours prior to the accident. The operating manual requires a torque check every 50 hours.

During the removal of the spark plugs, it was found that the number 5 spark plug was only finger tight with evidence of exhaust blow-by at the spark plug gasket area. The number 6 spark plug was torqued to about 50-inch pounds (specified torque is 300- to 360-inch pounds. All other front and rear plugs were properly torqued.

According to logbook information, the most recent documented annual inspection occurred on April 15, 2005, at 407.38 hours SMOH. The tachometer time was noted to be 466.19 hours at the accident examination. The logbook entry noted the retorqing of the propeller, cylinders, and carburetor attach nuts. Additionally, it was noted that the number 5 cylinder was removed, repaired, and reinstalled. On May 13, 2005, at 449.89 hours, an oil change and a propeller retorque was noted in the log.

At the time of the accident, the Santa Barbara air traffic control tower was reporting: wind 140 degrees at 06 knots; visibility 9 statute miles; weather clear; temperature 72 degrees Fahrenheit; dew point 59 degrees Fahrenheit; and the altimeter was 29.79 inHg. According to a Federal Aviation Administration carburetor icing probability chart, at the time of the accident the temperatures were conducive to "Serious Icing at Glide Power." The pilot was on the ground holding for release for about 15 minutes prior to his release for takeoff.

The Safety Board received the form 6120.1/2, Pilot/Operator Accident Report Form on 2/10/06. It has been added to the docket.

NTSB Probable Cause

a loss of engine power due to carburetor ice aggravated by the poor operating condition of the magnetos and the improper magneto-to-engine timing.