ERA15FA109

An in-flight loss of control for reasons that could not be determined during postaccident investigation; the loss of control likely occurred during a simulated loss of power in the right engine during an instructional flight.

The flight was the seventh lesson for the multiengine student, which likely included a simulated engine failure of the right engine usually performed over or near the destination airport. After takeoff, the flight proceeded north; radar returns were consistent with airwork. The airplane then turned and began flying toward the destination airport at 3,600 ft mean sea level and 105 mph. A witness heard a "pop" sound, and another witness heard an unusual engine sound; these might be consistent with a quick reduction in power on one engine, and, based on radar data, the airplane began to slow about that time, consistent with reduced power from one engine. The airplane then began a right turn, pitched nose down, descended into a building, and was nearly consumed by a postcrash fire. Although the final descent was captured by a security video, the low-resolution image precluded a determination of the state of the airplane at that time. No structure associated with the aft portion of the fuselage was identified in the wreckage. Examination of sections of the fractured structure revealed no evidence of preimpact failure or malfunction. Examination of the fractured left rudder cable revealed extensive postaccident heat damage to the fracture surface that precluded determination of the fracture mode. Examination of the engines and propellers revealed no evidence of preimpact failures or malfunctions; neither propeller was in the feathered position. The rudder with attached trim tab and a flight bag separated from the airplane during the descent came to rest outside the impact area. The separated rudder exhibited evidence of overtravel in both directions that is consistent with loss of cable tension; the reason for the loss of cable tension could not be determined. It also could not be determined how the flight bag became separated from the wreckage. Discrepancies previously noted by Federal Aviation Administration personnel during a ramp inspection of the accident airplane had been repaired before the accident flight. Further, the pilot who flew the accident airplane the day before reported no discrepancies during that flight. Although the toxicological finding in specimens of the pilot-rated student were positive for ethanol, it is likely that it was the result of postmortem production.

Testing was performed using a Polk County Sheriff's Office helicopter in an effort to determine the altitude an aircraft would first come into view of the same security camera that recorded the end portion of the flight. The testing revealed that an aircraft first came into view of the camera at 145 feet above ground level; the helicopter was over the impacted building. A performance study was performed by NTSB personnel using radar data correlated to the accident airplane. The performance study indicated that for the final 3 minutes of flight, or between 0910 and 0913, which included a right turn, the groundspeed decreased from about 121 mph to 103 mph resulting in a decrease of 5.75 mph per minute. At 0912:25, the airplane began a right turn, and between 0912:25 and 0912:58, the airplane changed heading from 172 to 239 degrees, resulting in a rate of turn of about 2 degrees per second. The final 13 data points (which included the right turn) have no altitude associated with them; therefore, the rate of descent could not be determined. The report also reviewed the video clip that captured the final portion of the descent. The five frames that recorded images of the airplane descending at a steep angle indicated that in the second frame, the fuselage of the airplane was aligned vertically and the wings were on the horizontal axis. The calculated rate of descent (estimate) was approximately 211 mph, but the report indicated that estimate was an approximation because of the distortion of the lens, the blurriness of the aircraft image, and the unknown trajectory of the aircraft. The report also indicated the estimate was higher than the final calculated groundspeed from radar by more than 100 mph. Examination of the tubular structure and fractured left rudder cable was performed by the NTSB Materials Laboratory located in Washington, D.C. According to the NTSB Materials Laboratory Factual Report, metal loss was noted near both fracture surfaces of the tubular structure marked A and B. Areas adjacent to the fracture marked "A" showed deformation of the wall which was folded towards the forward direction, consistent with contact with another object moving forward relative to the cluster. Closer examination of the tubular structure marked "B" revealed the wall was deformed outward at the opposite edge of the area of metal loss. A crack extended from the edge of the metal loss at a location adjacent to and just below the outward deformation. Examination of the left rudder cable revealed the end did not display broomstraw or splaying, though the ends were heavily damaged by the postcrash fire, which precluded determination of the failure mode. At the other end of the cable piece, the fracture through the attachment lug showed rough features consistent with overstress fracture. Several days after the accident, an individual who was reportedly familiar with the operator's business and maintenance practices contacted NTSB and while choosing to remain anonymous provided NTSB a document that outlined possible issues with airplanes operated by the flight school, including the accident airplane. The reported items pertaining to the accident airplane included a bird strike to the right wing root, gear collapse during ground operation, temporary loss of power from both engines during climb-out, material/debris inside the fuel tank, normal maintenance items, and recurring issues with the aircraft's brakes. No maintenance record entries could be found directly attributed to the gear collapse or engine mount; the remaining items contained corrective action in the maintenance records. Postmortem examinations of the flight instructor and pilot-rated student were performed by the District 10 Medical Examiner's Office, located in Winter Haven, Florida. The cause of death for both was listed as multiple blunt force traumatic injuries. Forensic toxicology of available specimens of the flight instructor and pilot-rated student were performed by the FAA Bioaeronautical Sciences Research Laboratory, located in Oklahoma City, Oklahoma, and also by University of Florida Pathology Laboratories located in Gainesville, Florida. The report of analysis of specimens of the pilot-rated student by the FAA was marked "Yes" to the question putrefaction. Testing for carbon monoxide and cyanide was not performed, and the results were negative for the drug screen. Unquantified amounts of N-Butanol and N-Propanol were detected in the muscle specimen, and 112 mg/dL ethanol was detected in the muscle specimen while 17 mg/dL ethanol was detected in the liver specimen. The report by University of Florida indicated the result was positive (32 mg/100g) for ethanol in the liver specimen, while the results were negative for the comprehensive drug screen. The report indicated the liver specimen was unsuitable for Carboxyhemoglobin analysis by co-oximtery, but analysis by microdiffusion indicated normal percent Carboxyhemoglobin. The results of analysis of specimens of the flight instructor by FAA revealed testing for carbon monoxide and cyanide was not performed, and the results were negative for the drug screen. No ethanol was detected in the muscle specimen. The report by University of Florida indicated the results were negative for volatiles and the comprehensive drug screen. The report indicated the muscle specimen was unsuitable for Carboxyhemoglobin analysis by co-oximtery, but analysis by microdiffusion indicated normal percent Carboxyhemoglobin. Examination of the accident site revealed the airplane crashed into a concrete building, and the building and the contents of it were destroyed. The accident site was located approximately 2.4 nautical miles and 326 degrees magnetic from the center of LAL. According to personnel of the Lakeland Police Department, a black colored bag containing a study guide for the accident airplane, a pilot logbook, and over the counter pain relief medication was found near the accident site. The bag was associated with the pilot-rated student, and was removed from the site and secured before NTSB arrival. The bag was located approximately 459 feet and 13 degrees from the crash site. Examination of the bag revealed evidence of wear in several areas, but no evidence of fire was noted on the bag exterior or interior items. Law enforcement personnel also performed aerial and ground searches of the outlying area and no other aircraft parts were identified. Further examination of the area surrounding the accident site revealed a piece of rudder with rudder trim tab attached was located approximately 138 feet and 7 degrees from the accident site. Examination of the part revealed no evidence of fire; evidence of over travel of the upper hinge was noted on both sides of the rudder. The upper hinge remained attached and a portion of the vertical stabilizer aft spar remained attached to the hinge (45 degree shear lips of the fracture surfaces were noted). The leading edge from the upper hinge below was displaced to the left approximately 60 degrees. The full span of the trim tab remained attached, but the piano wire was extended about 1 inch at the bottom and several of the hinges were not secured. The lower portion of the forward spar was torn (45 degree shear lips), and the aft spar was fractured at the lower end of the trim tab (also 45 degree shear lips). The trim tab actuator control rod was pulled from the trim tab. The portion of the instrument panel, and avionics was located inside the building in the southwest corner. Examination of the instrument panel revealed it contained the rudder torque tube, rudder control pedals, control column, left control yoke, electrical wiring, sections of flight control cables, nose landing gear actuator, and throttle quadrant. Examination of the throttle quadrant revealed no cables were attached, and no determination could be made as to the pre-impact positions of the controls. Components located immediately