N62635Piper PA-23-250 · 1976

On October 21, 2009, about 0624 eastern daylight time, a Piper PA-23-250, N62635, was substantially damaged when it impacted trees and terrain immediately after takeoff from the Summerville Airport (DYB), Summerville, South Carolina. Night visual meteorological conditions prevailed, and an instrument flight rules flight plan was filed with a destination of St. Lucie County International Airport (FPR), Ft. Pierce, Florida. The certificated commercial pilot/owner and the three passengers were fatally injured. The personal flight was conducted under the provisions of 14 Code of Federal Regulations Part 91.

The airplane was based at DYB. A few days prior to the accident, the pilot was observed flying the accident airplane in the traffic pattern at night, and several individuals at the airport reported that the pilot did this to ensure that he was current for night operations. Email printouts that were found on the floor of the hangar where the accident airplane was stored contained communications between the four occupants about the weight and balance of the airplane. Their email discussions also included the decision to create a list of what items should be left behind if the original planned load exceeded the airplane limitations. Other paperwork found in the hangar documented the weights, in pounds and ounces, of the planned cargo items. The occupants of the airplane were headed to an amateur radio operator contest in the Bahamas.

A flight plan was filed for a 0545 departure from DYB. Several individuals who lived in houses located southeast and northwest of the airport heard the accident airplane. One witness heard the engines of the airplane start up, and observed the airplane during its takeoff roll from runway 24. However, due to the location of the trees on his property, the witness was unable to see the airplane during the initial climb phase. Another witness reported that around 0615 she heard the airplane when it was "in the place where the airplanes sit before they take off," and that the engine sounds changed pitch twice. Most witnesses reported noticing that the sound of the engines was "loud." A witness reported that the runway lights were not illuminated prior to the accident. Several witnesses reported three or four post-accident explosions.

Post accident activation by both the airport manager and the arriving medical helicopter revealed that all the lights illuminated correctly. About 0627, a Dorchester County Sheriff's patrol unit arrived on scene, and very shortly thereafter, the fire department units also arrived.

The pilot, age 69, held a commercial pilot certificate, with ratings for single-engine land, multiengine land, and instrument airplane. His most recent Federal Aviation Administration (FAA) second-class medical was issued on June 10, 2009. At that time, the pilot reported a total flight time of 4,326 hours of flight experience. According to documentation provided by a local certificated flight instructor, the pilot had accomplished a biennial flight review on January 29, 2008.

The airplane was issued an FAA airworthiness certificate on April 15, 1976, and was registered to the accident pilot on May 16, 1997. It was equipped with two Lycoming IO-540-C4B5 engines. According to one maintenance provider familiar with the accident airplane, at the time of its most recent annual inspection, the hour-recording meter registered 2,260.1 hours, and there were 5,015.1 total hours of service on the airframe. On October 19, 2009 the oil was changed in both engines, and at that time, the hour-meter registered 2,345.4 hours, the left engine had accumulated 1,581.0 total hours in service, and the right engine had accumulated 1,906.4 total hours in service.

The 0615 recorded weather observation at DYB included calm winds; visibility 10 miles, clear skies, temperature 4 degrees C, dew point 3 degrees C; altimeter 30.26 inches of mercury.

The airport was equipped with a single runway oriented northeast to southwest and designated 6/24. The runway was 3700-feet-long and 75-feet-wide, constructed of asphalt, and was equipped with medium intensity runway lights that were pilot activated utilizing the common traffic advisory frequency (CTAF). The airport did not have an air traffic control tower.

The runway lights are set to a timer and automatically turn off as programmed. A post-accident functional test of the airport runway lighting system revealed that all systems operated normally. Communication made over the CTAF and activation of the pilot-controlled lighting did not have recording capabilities and was not recorded.

An on-scene investigation revealed that the airplane impacted the ground in a wooded area 584 feet south of the runway centerline, and approximately 2/3 of the way down runway 24. The first tree that the airplane impacted was 74 feet beyond the boundary of the wooded area. The surrounding trees were approximately 80 feet high. The tree and ground scars indicated a left-wing low attitude as the airplane entered the trees and it came to rest 93 feet from the point of first tree strike. The debris path was oriented on a 102 degree heading, and the wreckage was oriented on a 360 degree heading. The left wing outboard fuel tank was located along the debris path, 45 feet from the initial tree impact. It exhibited extensive impact damage, and was devoid of fuel. The remainder of the airplane exhibited fire and crush damage. The forward cargo compartment baggage door exhibited a gouge forward of the door locking handle and approximately 15 inches forward of the trailing edge and exhibited no thermal damage. The baggage door was found approximately 13 feet forward of the aircraft wreckage and the lock was void of a key. The instrument panel and instruments were destroyed by post impact fire. The two front seat and center seats were separated from their tracks and exhibited impact damage and post impact fire damage. The main cabin door was separated and exhibited impact damage and post impact fire damage; however, it was in the locked position. Several restraint system buckles were located and found to be latched; however, all were void of webbing due to the post impact fire. The main spar, aft spar, and cabin tubular frame were fractured with molten metal present from the post impact fire. Control cable continuity for the ailerons and elevator, from the cockpit floor area where the control column was located, to all respective control surface attach points, was confirmed. The aileron cables exhibited a tensile overload condition. The landing gear and flaps were in their retracted positions. The fuel lines and fuel valve position could not be determined due to the post impact fire. However, all fuel caps were accounted for and appeared to be in the locked position. Approximately 7 feet of aft fuselage remained; however, it had considerable thermal damage. There was approximately 3 feet of vertical stabilizer spar attached to the aft fuselage section, and the rudder trim drum was attached to the remaining spar and was found in the neutral tab position. The rudder stops were found and no marks were noted. The left wing was separated from the fuselage at the attach fittings and exhibited impact damage and post impact fire damage.

The two engines were located adjacent to one another, the right engine came to rest upright, the left engine came to rest inverted, and all propeller blades remained attached to their respective propeller hubs. Both engines exhibited thermal damage throughout. Spark plugs were removed and exhibited thermal damage. Fuel ignition spider, fuel screen, and oil filter exhibited thermal damage.

A follow-on examination was conducted on November 10, 2009 at a storage facility in Griffin, Georgia.

Left Engine

The left engine could not be rotated at the propeller flange due to thermal damage. A borescope examination was conducted and no preimpact mechanical anomalies were noted. The engine was partially disassembled and all six cylinders were removed, no preimpact mechanical anomalies were observed. Both magnetos from the left engine were fire damaged and could not be tested. Examination of the top and bottom spark plugs revealed fire damage; however, the electrodes were intact. The crankshaft and camshaft were examined and no preimpact mechanical malfunctions were observed; however, the engine, crankshaft, and internal components were thermally damaged. The No. 1 piston was thermally damaged and a portion of the piston head appeared to have been melted. The fuel pump sustained thermal damage and could not be tested. All fluid carrying hoses exhibited thermal damage. The fuel injector servo was thermally damaged.

Right Engine

The engine could not be rotated at the propeller flange due to thermal damage. A borescope examination was conducted on the right engine; no preimpact mechanical anomalies were noted. The engine was partially disassembled, all six cylinders were removed, no preimpact anomalies were observed, and continuity was confirmed for both the crankshaft and camshaft. Both magnetos from the right engine were fire damaged and could not be tested. Examination of the top and bottom spark plugs revealed fire damage; however, the electrodes were intact. The rear gear accessory drive was intact; however, it was thermally damaged. The accessory drive gears remained intact. Thermal damage was present on cylinders No. 1 and 2. The fuel pump sustained thermal damage and could not be tested. All fluid carrying hoses were thermally damaged. The fuel injector servo was thermally damaged.

Hartzell Propeller

The airplane engines were equipped with a two blade, aluminum construction, single-acting, hydraulically operated, constant speed propellers with feathering capability. It utilizes oil pressure from the propeller governor to move the propeller blades to a low pitch position. A spring and an air charge move the blades to the high pitch (feather direction) in the absence of governor oil pressure. It also incorporates a start lock mechanism that holds the blades in a low angle during engine start.

The left engine propeller remained attached to the engine and exhibited fire and thermal damage; both blades were loose and could be manually turned in the hub. One blade was bent forward at mid-blade and the other blade was bent aft about one-fourth of the radius from the hub. The components of the propeller assembly were intact, except for the fork assembly in which the cadmium plating was thermally damaged, and the pitch change rod which was fractured on both sides of the fork. The aft approximate one-half of the hub assembly was damaged internally consistent with the fracture of the pitch change rod.

The right engine propeller remained attached to the engine and exhibited fire and thermal damage. One propeller blade was bent aft approximately at the one-forth radius position and had leading edge damage and rotational scoring on the camber side near the blade tip. The other blade had slight S-bending on the outer one-half of the blade and the blade tip was curled aft and twisted toward the low pitch position. The cylinder was separated from the hub and had to be cut in order to remove the piston for examination. The position of the piston and fractured pitch change rod was consistent with a low pitch position. The fork was intact; however, the cadmium plating was thermally damaged and one pitch change block was partially fractured.

According to the Newberry Pathology Associates, the cause of death was "...multiple blunt force injuries..."

The FAA's Civil Aerospace Medical Institute performed forensic toxicology on specimens from the pilot and no drugs of abuse were detected.

Review of the pilot's FAA medical records indicated that he had a history of high blood pressure, gastroesophageal reflux disease, benign prostatic hypertrophy, and elevated cholesterol, all controlled on medication and noted in his most recent application for airman medical certificate, dated June 10, 2009. The pilot also had a history noted in the FAA medical records of a pituitary tumor surgically removed in 2001 with no evidence of changes on repeated MRIs of the brain since that time, and a history of melanoma surgically removed in 1985 with no evidence of recurrence on routine skin exams since that time. He was noted to have "excellent exercise tolerance" on a physician's note in the FAA medical records dated May 6, 2009. The autopsy report on the pilot noted that the "coronary arteries are difficult to see but there appears to be 95% occlusion by atherosclerosis" in two of the coronary arteries.

Forward Baggage Door

According to documentation provided by the airplane manufacturer the right propeller blade at its closest point was 9.25 inches from the trailing edge of the baggage door. The baggage door was hinged on the top and would open in an upward direction. The baggage door had a positive locking mechanism required on Service Bulletin 1194A. The locking mechanism would require the door to be shut and then locked utilizing a key that could only be removed once the door was locked. According to airframe maintenance log entry dated January 12, 2009, this had been complied with. The door also was equipped with a pressure switch that when activated would cause a light in the cockpit to illuminate. Due to the extensive thermal damage it could not be determined if the light had been illuminated prior to the accident.

FAA Advisory Circular 60-4A

"The attitude of an aircraft is generally determined by reference to the natural horizon or other visual reference with the surface. If neither horizon nor surface references exist, the attitude of an aircraft must be determined by artificial means from the flight instruments. Sight, supported by other senses, allows the pilot to maintain orientation. However, during periods of low visibility, the supporting senses sometimes conflict with what is seen. When this happens, a pilot is particularly vulnerable to disorientation. The degree of orientation may vary considerably with individual pilots. Spatial disorientation to a pilot means simply the inability to tell which way is 'up.'...Surface references and the natural horizon may at times become obscured, although visibility may be above flight rule minimums. Lack of natural horizon or such reference is common on over water flights, at night, and especially at night in extremely sparsely populated areas, or in low visibility conditions.... The disoriented pilot may place the aircraft in a dangerous attitude... therefore, the use of flight instruments is essential to maintain proper attitude when encountering any of the elements which may result in spatial disorientation."

According to the FAA Airplane Instrument Flying Handbook FAA-H-8083-15A, the definition of somatogravic illusion is "The misperception of being in a nose-up or nose-down attitude, caused by a rapid acceleration or deceleration while in flight situations that lack visual reference." It is further stated in Chapter 1 that "... [accelerating] stimulates the otolith organs in the same way as tilting the head backwards. This action creates the somatogravic illusion of being in a nose-up attitude, especially in situations without good visual references. The disoriented pilot may push the aircraft into a nose-low or dive attitude."

The Aeronautical Information Manual "Illusions In Flight" defines Somatogravic illusion as "A rapid acceleration during takeoff can create the illusion of being in a nose up attitude. The disoriented pilot will push the aircraft into a nose low, or dive attitude. A rapid deceleration by a quick reduction of the throttles can have the opposite effect, with the disoriented pilot pulling the aircraft into a nose up, or stall attitude."

"Principles and Practice of Aviation Psychology," states in part "G-Excess Tilt Illusions: When a pilot makes a real head tilt during a coordinated turn, the excess gravito-inertial force acting on the otolith organs produces a sensation of a greater head movement... Whether the G-excess effect in a turn causes the airplane bank illusion to be underbank or overbank depends on the direction of the pilot's head movement...a pilot whose head is turned toward the inside of the turn and is then elevated perceives a greater than actual tilt up of the head. The excess tilt is attributed to an underbank of the airplane and may cause the pilot to tighten the turn."

According to Spatial Orientation in Fundamentals of Aerospace Medicine, Third Edition, "G-induced excessive movement of the pilot's otolithic membranes causes the pilot to feel an extra amount of head and body tilt, which is interpreted as an underbank of the aircraft when the pilot looks up to the inside of the turn. Correcting for the illusion, the pilot overbanks the aircraft and it descends."