On August 14, 1993, at 1650 CDT, a Weatherly Model 620 owned by Hendrickson Flying Service of Rochelle, Illinois, struck electrical transmission lines during an aerial application operation and fell to the ground near Mendota, Illinois. VFR flight conditions prevailed and no flight plan was filed. The aircraft was destroyed and the pilot received serious injuries. The flight originated at Grandpa's Farm (0C7), Mendota, Illinois, about 1630 CDT.


Approximately one acre of corn was damaged by the aircraft as it skidded to a stop.


The pilot, Robert F. Hess, age 44, holds commercial pilot certificate No. 480627809 issued on January 31, 1989, with airplane ratings for single and multiengine land aircraft. The most recent second class medical certificate was issued to the pilot on February 2, 1993, and contained the limitation that correcting lenses be worn while exercising the privileges of his airman's certificate.


Fueling records at Hendrickson Flying Service established that the aircraft was last fueled on August 14, 1993, with the addition of approximately 25 gallons of 100 octane aviation fuel.

The maintenance records revealed no unresolved maintenance discrepancies against the aircraft prior to departure.


The accident site is a triangular shaped level farm field of approximately 58 acres bordered by electrical transmission lines on the east and south sides. The pilot had made two passes from east to west, flying under the power lines, applying chemicals. As the pilot began making his third pass, the aircraft's propeller and vertical stabilizer struck the 34,000 volt transmission line on the east side of the field. The transmission line remained intact, however some of the insulation was torn off. The aircraft's vertical stabilizer separated from the empennage after contacting the transmission line and fell to the ground approximately 15 yards west of the power lines. Measurements taken by the power line repair crew placed the height of the wire at 42 feet above ground level. The lone witness reported the aircraft's nose pitched down after striking the wire. Crop damage and ground scars began approximately 50 yards west of the power lines. Impact marks in the ground indicate the aircraft crashed in a slight nose low attitude at a high vertical sink rate. Both main landing gear broke off the aircraft and the spray booms which were suspended under the trailing edge of the wings separated from their attach points. The propeller and engine struck the ground with sufficient force to break the engine mounts and destroy the chemical hopper which was located between the engine and cockpit. The fuselage came to rest approximately 120 yards west of the power lines on a southerly heading, which was about right angles to the path of flight. Both wings and the fuselage area forward of the cockpit were destroyed by impact forces. The cockpit area aft to the tail section remained relatively intact.


The cockpit area of the aircraft remained intact. The seat supports and restraint system suffered damage from the crash impact. The steel tubular seat supports showed some forward distortion and one support was broken at a weld joint. The shoulder harness attach point failed in a forward direction, allowing the pilot to be thrown against the aircraft instrument panel. The aircraft instrument panel was caved in with approximately the same radius that the shoulder harness attach point was bowed forward. Rescue personnel found it necessary to cut one seat support to facilitate removal of the pilot from the wreckage.

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