Aviation Accident Summaries

Aviation Accident Summary LAX06LA036

Lincoln, CA, USA

Aircraft #1


Ryan Aeronautical ST3KR


The airplane impacted terrain in a near wings level pitch attitude after experiencing a stall. A witness, who was flying his own airplane above and behind the accident airplane, observed it make a left turn. He observed the accident airplane's left wing bobble and the nose subsequently drop in what appeared to be a stall. The accident pilot recovered, but the left wing bobbled and dropped again in another stall. Prior to impact, the pilot pulled the nose up and the airplane impacted the ground hard in a near wings level attitude. According to the other pilot, he spoke to the accident pilot at the hospital. At that time, the accident pilot reported he was having trouble maintaining airspeed. Following his recovery, the accident pilot could not recall any of the events that led to the accident except for fueling the airplane prior to departure. Post-accident examination of the aircraft revealed no anomalies that could have resulted in a loss of airspeed or loss of aircraft control.

Factual Information

HISTORY OF FLIGHT On November 15, 2005 at 1540 Pacific standard time, a Ryan Aeronautical ST3KR (Ryan PT22) airplane, N56038, impacted terrain following a loss of control while maneuvering near Lincoln, California. The airline transport pilot, who was the owner of the airplane, operated it under the provisions of 14 CFR Part 91 as a personal flight. The pilot, who was the sole occupant, received serious injuries, and the airplane sustained substantial damage. Visual meteorological conditions prevailed and a flight plan was not filed for the local area flight that originated from the Lincoln Regional Airport, Lincoln, California, around 1520. The NTSB investigator-in-charge (IIC) interviewed another pilot who was flying his own PT22 airplane near N56038 when the accident transpired. The other pilot was flying above and behind the accident airplane when he observed the airplane make a left turn. Unsure of the accident pilot's intension, he followed in a left turn and observed the left wing of the accident airplane bobble and the nose subsequently drop in a stall. The accident pilot recovered, but the left wing bobbled and dropped again in what appeared to be another stall. The accident airplane was in a nose low pitch attitude heading toward a rice field, but the pilot pulled out and impacted the field hard in a near wings level attitude. The other PT22 pilot further stated that he spoke to the accident pilot at the hospital. The accident pilot reported he was having trouble maintaining airspeed. According to a written statement provided by the pilot, he could not recall any of the events that led to the accident except for fueling the airplane prior to departure. PERSONNEL INFORMATION The airline transport pilot had a multi-engine airplane rating and was type rated in Boeing 737, 757, and 767 airplanes and the Airbus 320 airplane. He also held a commercial pilot certificate for single-engine land and sea airplanes. The pilot reported accumulating a total of 13,313 hours of flight time, of which 124 hours were accrued in the accident airplane. The pilot was positioned in the rear seat during the accident flight. According to the pilot's most recent first-class medical certificate, dated July 5, 2005, he had no limitations, and weighed 206 pounds at the time of certificate issuance. AIRCRAFT INFORMATION The airplane was manufactured in 1941 for the U.S. Army and was utilized for flight training. The aircraft was equipped with a 160-horsepower Kinner R-56 radial engine and a two-blade wooden propeller. The pilot purchased the airplane in 2001. Review of the maintenance records revealed the aircraft underwent its last annual inspection on June 4, 2005, at a total airframe time of 4,169.3 hours, approximately 2 hours prior to the accident (the last logbook entry for the airframe was dated October 9, 2005, which had a recorded total time of 4,171.2 hours). The engine was last overhauled in 1998, about 218 hours prior to the accident. During the June 4, 2005 overhaul, a mechanic listed the following compression test results for the 5 cylinders: #1 - 78/80, #2 - 74/80, #3 - 70/80, #4 - 66/80, #5 - 79/80 WRECKAGE AND IMPACT INFORMATION According to the Federal Aviation Administration (FAA) inspector who responded to the accident site, the airplane came to rest in a near inverted position in the field. The engine was separated from the engine mount and the two wooden propeller blades were shattered outboard of their roots. The oil cooler, starter, carburetor, parts of the engine mount, and propeller were found between the initial impact point and the airplane's final resting place. The left wing was folded aft, adjacent to the side of the airplane's fuselage. The FAA inspector was able to verify flight control continuity from the flight control surfaces to the cockpit. The wreckage was transported to Plain Parts of Sacramento, California, where it was examined in more detail on December 12, 2005. TESTS AND RESEARCH The airplane's flight control continuity was again confirmed at the retrieval facility. It was noted during the wreckage examination that the shoulder harness the pilot was utilizing was torn from the restraint attach webbing. The stitching that secured the shoulder harness to the restraint attach belt was torn. Examination of the belt revealed it was manufactured on March 19, 1999, by Aero Fabricators of Lyons, Wisconsin. The data tag on the belt indicated that the rated strength of the assembly was 1,500 pounds. The needles on the load meter in the cockpit indicated the airplane sustained a +12-g and -4-g load; however, the validity of those values could not be confirmed. The 5-cylinder radial engine was examined. The carburetor, magnetos and oil pump were separated from the accessory section, and the # 4 cylinder was separated from the crankcase at the barrel base. The #4 connecting rod remained attached to the crankshaft, but was bent aft. The #4 piston remained attached to the connecting rod, but sustained impact damage to its skirt and rings. The #3 and #5 cylinder heads sustained impact damage severe enough to crack the cylinder heads. The #3 cylinder also sustained impact damage in the aft direction resulting in a bulged area, where the cylinder skirt normally meets the crankcase. This bulge prevented the removal of the piston from the cylinder. The #3 and #5 cylinders were removed from the crankcase and the #4 and #3 connecting rods were cut to facilitate crankshaft rotation. Smooth rotation of the crankshaft was obtained with no anomalies noted with the main bearing. Rotation of the crankshaft via the fractured propeller revealed continuity to the accessory gearbox, and to the connecting rods and valves for the #1 and #2 cylinders. Thumb compression was obtained on those two cylinders. The rocker arm-to-valve clearance was checked for the #1 and #2 cylinders. All clearances (two intake and two exhaust) were below the specified minimums of 0.08 inches for the exhaust and 0.06 inches for the intake. Examination of the #3, #4, and #5 intake and exhaust valve faces revealed no anomalies. Removal of the #3 exhaust valve from the valve guide revealed no anomalies with the springs, keepers, or valve shaft. No overheat discoloration or heat distress was observed. The #3, #4, and #5 pistons, piston pins, connecting rods, and cylinder walls were all unremarkable with no pre-impact anomalies noted. Removal of the accessory section case revealed the cam lobes for each valve were in good condition and well lubricated. The cam rollers rotated freely and were well lubricated. The internal valve timing revealed no anomalies. No anomalies were noted with any gears inside the accessory section. Rotation of the oil pump shaft resulted in the flow of oil from the pump housing. No binding or anomalies were noted with the pump. The internal magneto timing was checked. Both magnetos sustained significant impact damage, but were within timing limits. The carburetor's throttle and mixture linkages remained intact and attached; however, they were separated upstream of the primary control arms. Some of the carburetor screws that join the two carburetor halves were loose, but still had the safety wires attached. The safety wires sustained some impact deformation damage. Separation of the carburetor halves revealed the internal carburetor components were intact and in place. The accelerator pump was checked and tested with some fuel. The pump functioned normally. The carburetor inlet filter was clean and free from debris. The metallic float appeared to be intact and in good condition. The float level was about parallel to the carburetor half joint and accepted a 13/64th bit (the carburetor data plate indicated that a maximum setting of 7/16th was acceptable). All of the spark plugs were removed and examined. All plug electrodes displayed normal wear and operational signatures when compared to the Champion AV-27 check-a-plug chart. The fuel selector linkage and valve sustained impact damage. The armature for the valve was in mid-travel, and in a position that did not correlate to a specified selection. Removal of the fuel selector valve's cover revealed that the internal cam was partially opening one of the poppet valves. The wooden propeller blades were splintered and separated near the roots. One blade sustained the most significant splinter damage with some of the splinters being distorted aft and opposite the direction of rotation. Some sections of that blade were separated near the hub. The propeller attach bolts were in place and secure. ADDITIONAL INFORMATION The wreckage was released to the owner's representative on November 1, 2006.

Probable Cause and Findings

The pilot's failure to maintain airspeed, which resulted in an inadvertent stall while maneuvering.


Source: NTSB Aviation Accident Database

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