N891JCAyres S2R-T34 · 1999

On June 18, 2014, about 1930 eastern daylight time, a Grumman Aircraft G-164B, N891JC, impacted the ground during a forced landing shortly after takeoff near Chorman Airport (D74), Farmington, Delaware. The airplane was owned and operated by Chorman Spraying, LLC as an aerial application flight. The commercial pilot received minor injuries and the airplane sustained substantial damage to the fuselage and empennage. Visual meteorological conditions prevailed and no flight plan had been filed for the local flight, which was operated under the provisions of Title 14 Code of Federal Regulations Part 137. The flight was originating at the time of the accident.

According to the pilot, he flew the airplane in the morning and returned to the airport about 1900, to load the hopper tank with insecticide and water, for a flight to a nearby watermelon farm. After loading the product and fueling the airplane, he taxied out, performed the required pre-takeoff checklist items, and departed to the north. After departure, he maneuvered the airplane in order to climb out to the right of the runway's extended centerline to avoid overflying a residence. He further reported that he reduced the manifold pressure back to 32 inches and the propeller speed to about 2,000 rpm. Approximately 150 feet above ground level, he commanded a slight left bank towards the west and immediately the airplane started to "settle." The pilot leveled the wings; however, the airplane started an uncommanded right bank "similar to entering a stall." He attempted to pull the product "dump" handle, but inadvertently activated the "spray" handle. He then attempted to pull the dump handle again, but was unable to do so due to the airplane's close proximity to the ground. The airplane subsequently impacted a field, nosed over, and came to rest inverted.

According to the pilot and Federal Aviation Administration (FAA) records, the pilot held a commercial pilot certificate with a rating for airplane single-engine land, multiengine land, and instrument airplane. He also held a flight instructor certificate for airplane single and multiengine land, and instrument airplane. The pilot's most recent second-class medical certificate was issued on October 24, 2013. According to the pilot, he had accumulated 2,306 hours of total flight time and 573 hours of flight time in the accident airplane make and model.

According to the pilot and the operator's records, the single-engine, tailwheel-equipped biplane was manufactured in 1977. It was powered by a Pratt and Whitney radial engine with 10,125 hours of time in service and 553.53 hours since major overhaul. The most recent annual inspection was recorded on May 8, 2014.

The 1854 recorded weather observation at Sussex County Airport (GED), Georgetown, Delaware, located 15 miles to the southeast of the accident location, included wind from 210 degrees at 8 knots, visibility 10 miles, clear skies, temperature 33 degrees C, dew point 20 degrees C; barometric altimeter 29.96 inches of mercury. The density altitude was about 2,100 feet.

The airport was a privately owned airport and at the time of the accident did not have a control tower. It was equipped with a single runway designated 16/34. The runway was 3,588 feet long and 37 feet wide and the runway surface was considered "in poor condition." The airport elevation was 66 feet above mean sea level.

Examination of the airplane by a FAA inspector, following the airplane's recovery from the field, revealed that the airplane's fuselage, vertical stabilizer, and rudder were substantially damaged. Rotation of the engine, by hand, was accomplished utilizing the propeller hub, which revealed continuity through the engine and thumb compression on some of the cylinders. However, there was no rotation through the supercharger and the impeller was not rotating.

The engine was examined, under the supervision of the NTSB Investigator-in-Charge, and during the examination the engine was noted as exhibiting minimal damage. When the engine was rotated by hand, utilizing a crankshaft turning bar, some internal binding was noted and the impeller did not rotate. Thumb compression was observed on all cylinders. Due to the internal binding, an engine run was not possible and the engine was disassembled. During the disassembly it was noted that the intermediate gear had three teeth that were impact sheared, and further examination of the gear revealed no other damage. Examination of the engine revealed no evidence of preimpact anomalies that would have precluded normal operation. For a detailed report on the engine examination refer to the public docket for this accident.

According to the pilot and operator, the airplane was fueled with 80 gallons of fuel and had 250 gallons of product in the forward hopper tank, just prior to departure. The airplane weight at the time of the accident was about 6,934 pounds, and the maximum gross weight for the airplane was 7,564 pounds.

Density Altitude

Pilot's Handbook of Aeronautical Knowledge (FAA-H-8083-25A) noted that density altitude represents pressure altitude corrected for nonstandard temperature. A decrease in air density corresponds with an increase in density altitude and a decrease in airplane performance. Density altitude is used in calculating airplane performance.

FAA Pamphlet FAA-P-8740-2 (2008), "Density Altitude," defines density altitude as "pressure altitude corrected for non-standard temperature variations." Density altitude can affect aircraft performance. As density altitude increases, air density decreases, which results in decreased aircraft performance. According to the Koch chart on page 3 of the pamphlet, and based on the conditions at the time of the accident, 91 degrees F and pressure altitude of about sea level, the airplane's climb rate would have been reduced by about 20 percent.