History
On September 23, 2011, at 1615 eastern daylight time, a Cessna P210N, registration N210LE, operated by an individual under 14 CFR Part 91, incurred substantial damage when it impacted trees during a forced landing in South Deerfield, Massachusetts. The pilot and passenger received serious injuries. Instrument meteorological conditions prevailed and an instrument flight rules flight plan was filed. The flight departed Barnes Municipal Airport (BAF), Westfield, Massachusetts, at about 1539, en route to Hancock County-Bar Harbor Airport (BHB), Bar Harbor, Maine.
According to the pilot, after takeoff he raised the landing gear and the gear warning horn remained on continuously. He reported to the tower controller that he might return to land. His passenger looked for the gear warning horn circuit breaker, but about two minutes later the warning horn stopped by itself. The pilot considered the issue resolved and continued to destination. The controller instructed the pilot to contact departure control, and a frequency change was approved.
Immediately after the frequency change, the navigation systems failed, restarted, and failed again. The cabin fan, instrument lights, and cabin lights failed, and the airplane experienced a total electrical system failure. The pilot reported encountering turbulence and heavy rain and elected to climb above the weather. The airplane seemed to receive strong gusts, with an indication of over 2,000 feet per minute descent. The pilot lowered the gear handle and extended flaps to stabilize the airplane, but neither functioned. He arrested the descent and decided to descend below cloud level for a precautionary landing. Seeing a clearing in the clouds, he performed a standard-rate spiral descent. He broke out of clouds at about 2,700 feet mean sea level. He saw an open field and maneuvered for a downwind approach. On approach, about 300 feet above ground level, the airplane porpoised three times; the pilot increased power but the porpoising continued. The nose struck a tree, the airplane hit the ground, and came to rest about 200 feet past the tree.
Personnel Information
The pilot held a private pilot certificate with ratings for airplane single-engine land and instrument airplane. He held a third-class medical certificate issued on June 24, 2010, with a limitation requiring corrective lenses. He reported 1,452 total flight hours, of which 985 were in the accident make and model, and 87 hours were in actual instrument conditions.
Aircraft Information
The airplane was a pressurized, six-place, high-wing Cessna P210N, serial number P21000825, manufactured in 1983 with a standard airworthiness certificate in the normal category. It featured an optional dual alternator electrical system and was powered by a Continental Motors TSIO-520-AF3B 310-horsepower engine with a McCauley controllable-pitch propeller. The most recent annual inspection was performed on August 11, 2011. At the accident time, the airframe had 2,985 total hours; the engine had 350 hours since major overhaul.
The airplane was equipped with electrically operated equipment including a Garmin GMX200 Multi-Functional Display, Garmin 530WAAS, Garmin SL30 #2 NAV/COM, Garmin GTX330 transponder, Garmin GMA340 audio panel, Goodrich WX-500 Stormscope, 6-place stereo intercom with XM interface, Garmin GDL69A, factory weather radar pod, Bendix King KN62A DME, EDM800 engine monitor, Shadin fuel flow, HID lights, and PS Engineering PAV-80 audio/video system.
Meteorological Information
The nearest official weather observation was at Barnes Municipal Airport, 20 miles north of the accident site. At 1609, the automated weather observing system reported wind from 130 degrees at 4 knots; visibility 6 statute miles; light rain and mist; broken clouds at 900 and 1,400 feet; overcast at 2,200 feet; temperature 22°C; dew point 20°C; altimeter 30.04 inches of mercury.
Wreckage and Impact Information
A Federal Aviation Administration inspector reported that the right wing was damaged and folded aft onto the fuselage; the left wing was bent aft. Flight control continuity was confirmed to all controls. The flap actuator indicated about 20 degrees of flaps extended. The propeller separated from the engine, and the propeller bolts were pulled from the crankshaft flange. The engine remained intact and attached. The No. 6 cylinder rocker box cover had a puncture hole; the No. 6 intake valve and stem penetrated the cover, with the valve head resting on top of the cylinder.
Tests and Research
An electronic JPI Engine Data Monitor (700/800 model) was removed and sent to the NTSB Recorders Laboratory. The data showed no engine anomalies but indicated battery voltage dropped rapidly from 21 to 10 volts just before the end of the data, coinciding with electrical power loss.
A postaccident engine run was conducted at the manufacturer's facility. The No. 6 cylinder was replaced, and the engine operated successfully in low, intermediate, and high rpm ranges. The No. 6 intake valve guide, valve, springs, retainer, and keys underwent metallurgical evaluation at Continental Motors, which revealed the valve spring retainer failed in overload.
Engine maintenance records showed the engine was overhauled on July 21, 2009, during which ECI part number 648045 pistons were installed (incorrect pistons). According to ECI service bulletin 99-8-1, AEC631397 cylinder assemblies with part number 648044 pistons should have been installed. The installed pistons produced a higher compression ratio for which the engine was not adjusted.
The No. 1 and No. 2 alternators and control units were examined by Cessna Aircraft Company. Both control units functioned normally in regulation, low voltage annunciation, overvoltage trip, and field current overload tests. The No. 1 alternator malfunctioned about five minutes into dynamic testing; disassembly revealed discolored rotor and slip ring, and one stator phase winding was burned and shorted. The No. 2 alternator could not be dynamically tested due to accident damage; disassembly showed burnt windings in two stator phases.
A postaccident examination of the electrical system revealed that the alternator restart battery pack did not have enough voltage to reenergize the alternator field if an alternator failed. The system required a functional check every 25 hours and batteries needed replacement annually or sooner if alternators could not restart under heavy load. The most recent documented battery change for the restart system was December 15, 2000.
In a postaccident interview, the pilot stated he attempted to regain electrical power by cycling alternator switches and tried to energize the alternator field using the single-alternator emergency procedure from the pilot's operating handbook (POH), rather than the dual-alternator system procedure. The dual-alternator emergency procedure is a POH supplement and instructs to depress the ALT RESTART switch. The pilot said he did not know about that switch.
For the dual alternator system, the BEFORE TAKEOFF checklist in the supplement required a functional check. The checklist present in the cockpit did not include this check or the supplement's emergency procedures. The complete supplement is in the accident docket.
Probable Cause
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