NTSB Factual Report

On March 3, 2003, about 1400 mountain standard time, a homebuilt experimental Towner Kit Fox 4, N95FT, nosed over during an emergency landing at Glendale, Arizona, after losing a portion of its propeller during flight. The pilot/owner was operating the airplane on a local area instructional flight under the provisions of 14 CFR Part 91. Visual meteorological conditions prevailed, and no flight plan had been filed. The private pilot and the certified flight instructor (CFI) were not injured; the airplane sustained substantial damage. The flight departed Glendale Municipal Airport about 1310.

In a written statement submitted by the owner of the airplane, he stated that shortly after calling Glendale tower, they heard a loud "womp" followed by a vibration. The pilot reported that he could see the propeller had split and a piece of it was missing. The pilot and his CFI advised the tower that they would be making an emergency landing. They shut down the engine and made an approach to land in an alfalfa field. During the landing roll out, the airplane impacted a dirt bank and came to rest inverted.

Tennessee Propeller, Inc., Normandy, Tennessee, examined the propeller under the surveillance of a Federal Aviation Administration aviation safety inspector. The propeller had 38 plies of wood veneer that were laminated as a blank prior to machine shaping and sanding. One blade sustained damage; the other blade did not. The damaged blade had evidence of mud on the surface and water in the grain. A large piece of the blade fit into a portion of the propeller that had the damage. However, a large portion of the blade was still missing. The damage appeared to result from bending of the blade to a degree that a large portion failed in a negative direction to that of normal thrust. Because the piece of the propeller that had separated in flight was not recovered, the inspector could not conclude that the propeller failed in flight.

The National Transportation Safety Board investigator-in-charge (IIC) interviewed the pilot by telephone after the propeller examination. The pilot reported that prior to the propeller separation he did not feel any vibrations or observe any nicks on the propeller. After the unusual sound just prior to landing, the CFI noticed a portion of the propeller fall to the ground. After the accident, the pilot noticed a small feather on the propeller and reddish colored material.

The IIC sent the propeller to the Safety Board Materials Laboratory, Washington D.C., for examination. The specialist took samples of the propeller and subjected them to Phenolphthalein presumptive blood tests. Each test responded with positive results. The positive tests suggested that animal tissue was present. The specialist took an additional sample from the root of the blade, immersed it in water, and subjected it to ultrasonic agitation. The specialist filtered the resulting cloudy liquid, and examined the particles using a stereomicroscope. The residue was medium brown colored containing tan colored particles with a gel-like consistency. A singular piece of the residue measured approximately 0.016-inch long and 0.0025-inch diameter. The report (NTSB Report No. 03-803) is contained in the docket for this accident.

NTSB Probable Cause

the propeller's separation in-flight as a result of a bird strike.