NTSB Factual Report

On April 30, 2005, at 0930 Pacific daylight time, a Grumman G-164A, N5304, experienced a partial loss of engine power after takeoff and made a forced landing in a dry rice field near Yuba City, California. Twin Cities Aviation, LLC, operated the airplane as an aerial application flight under the provision of 14 CFR Part 137. The airplane sustained substantial damage. The commercial pilot/owner was not injured. Visual meteorological conditions prevailed for the local area crop dusting operation, and no flight plan had been filed. The airplane departed a private dirt strip (Vanderford Ranch Company Airport - CA73).

The National Transportation Safety Board investigator-in-charge (IIC) interviewed the pilot. He reported that he had started work about 0715, and had dropped 24 loads prior to the accident. He last refueled the airplane with 35 gallons of fuel, about 20 minutes prior to the accident. The airplane was loaded with 2,000 pounds of dry fertilizer that he was spraying on a rice field.

After takeoff, about 60-feet above ground level (agl), the pilot heard a "large backfire" and then the engine began to run rough. He stated that the engine was not developing enough power to sustain flight and he elected to make a forced landing on the dry rice field. The airplane landed hard and sheared off the landing gear. The pilot indicated that the airplane then tumbled before coming to rest on its belly.

According to a deputy from the Sutter County Sheriff's Department, the airplane came to rest on its belly on a northeastern heading about 300 feet beyond the initial touchdown spot.

AIRCRAFT INFORMATION

The airplane was a Grumman G-164A, serial number 593. A review of the airplane's logbooks revealed a total airframe time of 9,057.8 hours at the last inspection completed on November 5, 2004. The logbook entry did not indicate what type of inspection had been performed. An annual inspection was completed on May 1, 2004, at a total airframe time of 8,969.9 hours.

The airplane was equipped with a Pratt and Whitney R-1340 radial engine, serial number P-325448. A review of the engine logbooks revealed that a major overhaul was completed on May 12, 1999, at an estimated total time of 5,424.1 hours. A 100-hour inspection was completed on May 1, 2004, at a total engine time of 6,614.2 hours; 1,189.2 hours since major overhaul. During this inspection maintenance personnel recorded the following values for the compression test results:

#1 70 #2 68

#3 68 #4 60

#5 72 #6 62

#7 71 #8 64

#9 70

The last engine inspection was completed on November 5, 2004. The logbook entry did not indicate what type of inspection had been performed.

Review of the airframe and engine logbooks following the examination revealed that none of the entries showed a removal of the number 7 cylinder any time between 1999 and 2005.

TEST AND RESEARCH

The Safety Board IIC examined the wreckage at Plain Parts, Pleasant Grove, California, on May 23, 2005.

Maintenance personnel removed the top spark plugs. The spark plug electrodes were black in color. According to the Champion Aviation Check-A-Plug chart AV-27, the color corresponded to a lead and carbon fouled as well as a severely worn appearance.

Maintenance personnel performed a differential pressure check on all of the cylinders under the auspices of the Safety Board IIC. They obtained compression on all of the cylinders with the exception of the number 7 cylinder. They obtained low compression readings on both the number 2 and 9 cylinders (18/80psi). Investigators removed the numbers 2, 7, and 9 cylinders from the engine. There were no discrepancies noted with the numbers 2 and 9 cylinders. The number 7 cylinder had multiple cracks/breaks in the fin area, as well as at the top and bottom spark plug holes. A visual inspection of the inside of the number 7 cylinder revealed a crack on the inside of the combustion chamber side of the cylinder head from spark plug hole to spark plug hole; in-between the intake and exhaust valves.

NTSB Probable Cause

a partial loss of engine power due to multiple cracks in the number 7 cylinder. The reasons for the cracks were not determined