History of Flight
On July 9, 2011, about 1740 central daylight time, a Cessna 421C, registration N629TT, operated by a private individual, was substantially damaged when it impacted terrain while on approach to Demopolis Municipal Airport (DYA), Demopolis, Alabama. The certificated private pilot and six passengers were fatally injured. Visual meteorological conditions prevailed, and an instrument flight rules flight plan was filed for the flight that departed Creve Coeur Airport (1H0), St. Louis, Missouri, destined for Destin-Ft. Walton Beach Airport (DTS), Destin, Florida. The personal flight was conducted under Title 14 Code of Federal Regulations Part 91.
The airplane was based at DTS and owned by the pilot through a limited liability company. According to the pilot's father-in-law, the pilot, his wife, and five children flew from DTS to Pickens County Airport (JZP), Jasper, Georgia, on July 3, 2011. On July 5, they flew from JPZ to 1H0 uneventfully to attend a family reunion, where the airplane remained parked until the accident flight. The pilot and his family departed 1H0 about 1520 on the day of the accident.
According to information from the Federal Aviation Administration (FAA), the pilot was in cruise flight at flight level 210 (21,000 feet) and in contact with Atlanta air route traffic control center when he declared an emergency due to a rough running engine, about 1725. He diverted to DYA, located 12 o'clock and about 10 miles from the airplane's position. The pilot was switched to Meridian Approach and reported descending through 17,000 feet mean sea level (msl) at 1727:55, with the airplane positioned about 2.5 miles northeast of the airport. The pilot stated he planned to orbit over Demopolis during descent. At 1728:59, he confirmed a rough running engine; about 10 seconds later, he reported shutting down the right engine. He stated he did not believe he would require assistance after landing. At that time, the airplane was about 6 miles east of DYA at about 14,500 feet msl.
The pilot reported the airport in sight, was cleared for a visual approach, and approved for frequency change to the local common traffic advisory frequency about 1734. The airplane was about 2.5 miles northeast of the airport at about 7,000 feet. No further communications were received. Radar track was consistent with a left traffic pattern approach to runway 22. The airplane was descending from about 2,300 feet msl when abeam the runway threshold on downwind. The last radar target was at 1739 at 700 feet on base leg, about 3 miles from the approach end of runway 22 and about 0.5 miles northwest of the extended centerline. The airplane impacted trees in a wooded area about 0.8 miles north of the runway 22 threshold.
Pilot Information
The pilot, age 42, held a private pilot certificate with ratings for airplane single-engine land, multiengine land, and instrument airplane. He obtained his multiengine rating in November 2006. His most recent FAA third-class medical certificate was issued on July 19, 2007. His logbook was not recovered; at the time of that medical, he reported 642 total flight hours. His flight instructor noted that around the time of airplane purchase (September 2007), the pilot had 670 total hours including 140 hours in multiengine airplanes. As of May 14, 2008, he had 715 total hours including 200 multiengine hours. In July 2010, the instructor noted 870 total hours but did not note multiengine time. The pilot had practiced at least seven single-engine landings in the accident airplane, including at least three from a VFR traffic pattern. He completed Cessna 421 recurrent training on July 29, 2010, which included three practice single-engine landings. Based on airplane operation, total flight time at accident was estimated about 1,000 hours, including about 500 hours multiengine.
Aircraft Information
The eight-seat, low-wing, retractable-gear airplane, serial number 421C0616, was manufactured in 1978 and purchased by the pilot on September 11, 2007. It was powered by two Continental Motors, Inc., GTSIO-520-L, 375-horsepower engines, each equipped with a McCauley propeller assembly. The airplane was for sale at the time of the accident. Maintenance records were obtained from a broker, the pilot's representative, and a fixed-base-operator at DTS. The most recent annual inspection was performed on January 19, 2011, at a total airframe time of 7,799.9 hours and Hobbs time of 286 hours. The airplane had been operated about 305 hours since September 2007 and the annual inspection. The most recent recorded airframe logbook entry was on February 10, 2011, with no change in flight hours since the annual inspection. At that time, the left engine hydraulic filter and right main landing gear strut were replaced.
The left engine was overhauled by RAM Aircraft on August 31, 2007, at 3,780.7 hours total time in service, installed on September 28, 2007. At the annual inspection, it had about 305 hours since overhaul. The right engine was overhauled by Americas Aircraft Engines on August 24, 2004, at 1,595.7 hours total time, installed on September 30, 2004. At the annual inspection, it had about 514.2 hours since overhaul. The most recent right engine logbook entry on February 10, 2011, noted a reset of engine fuel pressures. In July 1994, vortex generators were installed per a supplemental type certificate. An oil analysis of samples collected on January 3, 2011, stated the samples "appeared normal." Both propellers were overhauled on June 1, 2010. At the annual inspection, they had about 172 hours. The airplane had two flight crew seats and five main cabin seats (two aft facing, three forward facing) plus an aft lavatory seat. An Artex ME406 emergency locator transmitter was installed on May 13, 2008, with battery replacement due October 2012. According to a work order for a pre-purchase inspection, as of June 3, 2011, the airplane had flown about 27 hours since the annual inspection.
Meteorological Information
The reported weather at Meridian Naval Air Station (NMM), Meridian, Mississippi, about 35 miles west of the accident site, at 1756 was: wind 270 degrees at 6 knots, visibility 10 statute miles, clear skies, temperature 34 degrees Celsius, dew point 22 degrees Celsius, altimeter 29.87 inches of mercury.
Aerodrome Information
Demopolis Municipal Airport was a public-use airport owned and operated by the City of Demopolis, located about 6 miles southwest of Demopolis, Alabama, at elevation 113 feet. It had one runway, 04-22, asphalt surface measuring 5,002 feet long by 100 feet wide. Meridian Naval Air Station had 8,000-foot runways, a control tower, and ARFF. Key Field (MEI), Meridian, Mississippi, about 40 miles southwest of DYA, had a 10,003-foot runway, control tower, and ARFF.
Wreckage and Impact Information
The airplane came to rest inverted in a wooded area with varied tree heights up to about 80 feet, in a flat attitude, on a course of about 100 degrees. The cockpit, the cabin up through 40 inches forward of the tail cone, and the left wing were consumed by fire. A series of tree strikes were observed about 50 feet above the ground, about 70 feet south of the main wreckage. A navigation antenna was found about 200 feet south-southeast of the main wreckage. The course from the antenna to the main wreckage was about 020 degrees. All major portions were accounted for. There was no longitudinal deformation of the fuselage. The radar dome on the nose was installed and retained its shape. All three landing gear actuators were in the extended position. Portions of the flaps not compromised by fire or impact were extended about 40 degrees. The entire right wing was separated at the root and came to rest against a tree adjacent to the main wreckage.
Aileron control cable continuity was established from cockpit controls to the fuselage aileron bellcrank, which was melted. Cables for the left aileron were observed near the aft aileron bellcrank area and continuous to the aileron bullwheel. Aileron trim cables were continuous from cockpit to trim tab chain. Measurement of the aileron trim actuator jackscrew was about 0.8 inches beyond the full tab-up position. The right aileron control cables were separated consistent with overload in several locations. One cable remained attached to the right bullwheel; the other was pulled out. The right aileron remained attached to the right wing.
Elevator control cables were attached to the aft elevator bellcrank with continuity to the cockpit area. The elevators remained attached to the horizontal stabilizer. The horizontal stabilizer was separated from the aft fuselage and located near the vertical fin. The aft elevator push-pull tube remained attached to the aft elevator bellcrank. The attachment to the elevator control horns was separated. The elevator trim tab remained attached and was extended beyond its up tab travel limit.
Rudder control cable continuity was established from the rudder to the rudder pedals. The top section of the rudder was separated from the vertical stabilizer. The lower section and rudder trim tab remained attached. Measurement of the rudder trim corresponded to about 3 degrees tab left (nose right setting).
The cockpit area was compromised by post-impact fire. All flight instruments were heavily damaged. The cabin door was found closed and locked. The emergency exit was installed. The ELT was destroyed in the fire. Cockpit seats were compromised; lower sections were found with severe fire damage. Five passenger seat frames were found in the cabin area. The aft lavatory seat was completely consumed. Fabric and padding for all seats was consumed. The two cockpit restraints were 3-point systems; the six passenger restraints were 2-point systems. All had lift-latch buckles. One cockpit seat belt was found latched, the other unlatched. Four of six passenger seat belts were found latched.
The left engine and propeller assembly remained attached to the left wing and were fire damaged. The left propeller was in low pitch and displayed signatures consistent with rotation at impact. Examination and teardown of the left engine at Continental Motors, Inc. (CMI), Mobile, Alabama, did not reveal any preaccident mechanical malfunctions or failures.
The right engine and propeller assembly remained attached to the right wing. One propeller blade was separated from the hub. The remaining two blades were at or near the feathered position and did not display evidence of rotation. All cylinders and accessories remained attached. Top spark plugs had intact electrodes with normal operating signatures. The fuel pump coupling was intact, but the camshaft gear exhibited damage to its gear teeth. The right engine was disassembled at CMI under NTSB supervision. Disassembly revealed additional damage and several missing teeth on the cam gear, and intake and exhaust valve contact on all six piston faces. The safety wire securing a cam gear bolt was broken at the head of the bolt, and a corresponding piece of safety wire was found in the oil sump, which contained metallic debris. The No.1 crankshaft main and connecting rod bearings exhibited damage consistent with lubrication distress. Other bearings were intact and did not display lubrication distress. Crankcase halves, camshaft, camshaft gear with separated teeth, cluster gear, crankshaft gear, No.1 main bearing, attachment bolts, safety wire, and oil sump contents were retained for further examination at the NTSB Materials Laboratory.
Teardown of both propeller assemblies at McCauley did not reveal any preaccident mechanical malfunctions or failures.
Medical and Pathological Information
Autopsies were performed on the pilot and passengers by the Alabama Department of Forensic Sciences, Montgomery, Alabama. Toxicological testing on the pilot by the FAA Bioaeronautical Science Research Laboratory showed no anomalies noted.
Tests and Research
Examination of retained components from the right engine was performed by an NTSB materials engineer. According to the Materials Laboratory Factual Report, the camshaft gear had 60 teeth. Forty-five were either fractured or crushed, two were damaged on the tooth flank, and 13 were intact. Fracture features showed uniform matte gray in the middle portion with smeared features near the flank root surfaces. A smooth curving arrest line was observed on one tooth, with radial features emanating from the boundary. Features consistent with fatigue in steel under relatively high stress concentration were present. Adjacent teeth did not contain evidence of fatigue, but another tooth displayed evidence consistent with surface spall.
No evidence of fretting was observed on the camshaft and cluster gear attachment bolts. Fracture features on the broken safety wire were consistent with overstress.
Examination of the crankcase revealed staining and impressions consistent with application of silk thread around the through-bolt holes on each side of the main bearing saddles at every main bearing location and at the bolt holes at all camshaft main saddles.
Teledyne Continental Motors Service Information Letter SIL99-2A, dated August 27, 2002, provided information on sealants, lubricants, and adhesives during maintenance. Page 16 contained a threading diagram for the GTSIO-520, with a warning to apply thread and permatex only as illustrated. Thread application locations were depicted at edges of crankcase and around through-bolt holes in saddle bosses for all camshaft main journals; no thread was called for around through-bolt holes at any crankshaft main bearing saddle bosses.
The right engine crankcase was returned to CMI for measurement of main bearing bores with and without silk thread per SIL99-2A. With silk thread installed, measurements ranged from zero difference to +0.0006 inches, with +0.0004 inches on the No.1 main bearing bore. According to a CMI representative, the main bearing at that location had a 0.006 minimum crush on each half when installed, and silk thread alone would not result in the damage observed or affect engine performance.
Additional Information
According to the airplane information manual, the minimum flight speed for controllability with one engine inoperative and a 5-degree bank towards the inoperative engine (Vmca) was 80 knots. Vortex generator installation reduced Vmca to 73 knots. Procedures for landing with an inoperative engine included approach speed of 111 knots with excessive altitude, landing gear down within gliding distance, and wing flaps down when landing was assured.
A timeline of search and rescue events was compiled using FAA air traffic control transcripts, Marengo County 911 call recordings, Sumter County Sheriff’s Office unit log, Alabama Emergency Management information, and interviews. The timeline showed about 6.5 hours elapsed from the last communication between Meridian Approach and N692TT, and about 6 hours from expected arrival to DYA before the airplane was found. Various local, county, state, and Federal emergency response agencies conducted search operations.