HISTORY OF FLIGHTOn April 7, 2017, about 1507 central daylight time, a Piper PA-28-180 airplane, N9179J, collided with terrain in Oxford, Iowa, following a loss of control. The flight instructor and the private pilot receiving instruction were fatally injured. The airplane was destroyed. The airplane was registered to Green Castle Aero Club LTD and was being operated by the instructor as a Title 14 Code of Federal Regulations Part 91 training flight. Visual meteorological conditions existed near the accident site at the time of the accident, and a flight plan had not been filed for the local flight. The airplane departed the Green Castle Airport (IA24), Oxford, Iowa, about 1449. There were no communications between air traffic control and the accident airplane. The airport surveillance radar located at the Eastern Iowa Airport (CID), Cedar Rapids, Iowa, showed that the airplane departed IA24 to the north, and shortly after takeoff, the airplane made a turn to the south. The airplane continued flying south about 8.4 miles until it crossed IWV Road SW at which time it turned and appeared to make S-turns along the road as it headed west. The airplane then turned south and continued for about 4 miles as it climbed to an altitude of 3,500 ft mean seal level (msl). The airplane then turned east and flew about 5.5 miles. The airplane then turned north and descended to 3,200 ft msl in the turn. The airplane continued flying north about 6 miles until reaching Interstate 80 at which time the airplane made a left 180° turn back to the south at an altitude of 3,400 ft msl. The airplane continued flying south about 2.7 miles until it entered a left turn and began a rapid descent; between 1507:08 and the last radar return at 1507:12, the airplane descended from 3,400 ft msl to 1,500 ft msl. A witness located about 1 mile east of the accident site stated that his attention was drawn to the airplane when he heard an engine popping and backfiring. The airplane appeared to be heading south-southeast, and it looked like it wasn't moving. The nose of the airplane then dropped, and the airplane entered a "downward spiral." He stated that he did not hear the engine at this point. The airplane made eight or nine spirals before it stopped rotating and continued in a nose-down descent. He lost sight of the airplane behind the hillside and shortly thereafter heard the impact. The witness stated that the airplane was spiraling in a clockwise rotation. PERSONNEL INFORMATIONThe flight instructor held a flight instructor certificate with airplane single-engine land and instrument airplane ratings; the certificate was initially issued on February 19, 2003, and most recently renewed on November 30, 2015. He also held a commercial pilot certificate with airplane single-engine land and instrument airplane ratings. The instructor held a Federal Aviation Administration (FAA) third-class airman medical certificate dated August 13, 2015. The last entry in the instructor's most recent logbook, logbook number 11, was dated April 7, 2017. The logbook showed that he had a total of 6,475.4 hours of flight experience. The pilot receiving instruction held a private pilot certificate with an airplane single-engine land rating, which was issued on October 7, 1986. The pilot held an FAA third-class airman medical certificate dated February 5, 2016. On the application for this medical certificate, the pilot reported that he had accumulated 97 hours of flight experience, none of which were flown in the previous 6 months. According to the pilot's family, he was just beginning to fly again after not having flown in quite a while. The last entry in the instructor's logbook was a 0.6-hour flight in a Cessna 150 on the day of the accident. This flight entry contained a remark, "T&G Ldg, BFR [biennial flight review] & Eval" along with the name of the pilot receiving instruction. The back pages of the logbook contained a list of endorsements the instructor had given. The page contained an entry showing that he had given the pilot receiving instruction his BFR endorsement earlier on the day of the accident. AIRCRAFT INFORMATIONThe airplane, manufactured in 1966, was a four-place, single-engine, low-wing airplane with fixed tricycle landing gear. The airplane was certificated as both a normal and utility category airplane, depending on the operating weight and center of gravity. A review of FAA records revealed that the airplane was purchased by the Green Castle Aero Club LTD on July 15, 2000. A spokesman for the aero club stated that the maintenance logbooks were in the airplane at the time of the accident. The logbooks were not located in the wreckage, which was partially consumed by a postimpact fire. The mechanic who worked on the airplane provided documentation showing that the airplane's last annual inspection was performed on February 6, 2017, at an airframe total time of 7,652.1 hours. The aero club provided an aircraft summary sheet dated March 1, 2017, which showed the airplane had a tachometer time of 7,657 hours. The pilot who flew the airplane before the accident flight reported that he filled the airplane nearly full of fuel before his 1.8-hour flight. The actual gross weight of the airplane at the time of the accident could not be determined as the weight and balance records were destroyed in the accident, and the basic empty weight of the airplane was unknown. Using the licensed empty weight of the airplane when it was manufactured, an estimated fuel load based on when the airplane was last fueled, and the passenger weights, the estimated gross weight of the airplane was about 1,915 lbs at takeoff with a center of gravity of 85.98 inches. The maximum gross weight for utility category operations is 1,950 lbs with center of gravity limits between 85.8 inches and 86.5 inches. Spins, steep turns, lazy eights, and chandelles are permissible in utility category operations. The Procedures Section of the PA-28-180 Airplane Flight Manual states, in part: 3. The PA-28-180 airplane is approved under FAA Regulations CAR 3 which prohibits intentional spins for normal category operation. The following information is noteworthy: a. The stall characteristics of the PA-28-180 are normal with the nose pitching down moderately following the stall, occasionally with a moderate roll which can be corrected by normal use of ailerons and rudder against the roll. b. Prolonged use of full rudder during stall practice may result in a rapid roll followed by a spin and should be avoided. Recovery from an incipient spin may be effected in less than one additional turn by use of opposite rudder followed by full forward control wheel. c. In the event that a fully developed spin is inadvertently experienced, recovery is best made by using full opposite rudder followed by full forward wheel and full opposite aileron. The control positions against the spin should be maintained during the entire recovery, which may require several turns and a substantial loss of altitude if the airplane is loaded heavily with a rearward center of gravity. AIRPORT INFORMATIONThe airplane, manufactured in 1966, was a four-place, single-engine, low-wing airplane with fixed tricycle landing gear. The airplane was certificated as both a normal and utility category airplane, depending on the operating weight and center of gravity. A review of FAA records revealed that the airplane was purchased by the Green Castle Aero Club LTD on July 15, 2000. A spokesman for the aero club stated that the maintenance logbooks were in the airplane at the time of the accident. The logbooks were not located in the wreckage, which was partially consumed by a postimpact fire. The mechanic who worked on the airplane provided documentation showing that the airplane's last annual inspection was performed on February 6, 2017, at an airframe total time of 7,652.1 hours. The aero club provided an aircraft summary sheet dated March 1, 2017, which showed the airplane had a tachometer time of 7,657 hours. The pilot who flew the airplane before the accident flight reported that he filled the airplane nearly full of fuel before his 1.8-hour flight. The actual gross weight of the airplane at the time of the accident could not be determined as the weight and balance records were destroyed in the accident, and the basic empty weight of the airplane was unknown. Using the licensed empty weight of the airplane when it was manufactured, an estimated fuel load based on when the airplane was last fueled, and the passenger weights, the estimated gross weight of the airplane was about 1,915 lbs at takeoff with a center of gravity of 85.98 inches. The maximum gross weight for utility category operations is 1,950 lbs with center of gravity limits between 85.8 inches and 86.5 inches. Spins, steep turns, lazy eights, and chandelles are permissible in utility category operations. The Procedures Section of the PA-28-180 Airplane Flight Manual states, in part: 3. The PA-28-180 airplane is approved under FAA Regulations CAR 3 which prohibits intentional spins for normal category operation. The following information is noteworthy: a. The stall characteristics of the PA-28-180 are normal with the nose pitching down moderately following the stall, occasionally with a moderate roll which can be corrected by normal use of ailerons and rudder against the roll. b. Prolonged use of full rudder during stall practice may result in a rapid roll followed by a spin and should be avoided. Recovery from an incipient spin may be effected in less than one additional turn by use of opposite rudder followed by full forward control wheel. c. In the event that a fully developed spin is inadvertently experienced, recovery is best made by using full opposite rudder followed by full forward wheel and full opposite aileron. The control positions against the spin should be maintained during the entire recovery, which may require several turns and a substantial loss of altitude if the airplane is loaded heavily with a rearward center of gravity. WRECKAGE AND IMPACT INFORMATIONThe airplane came to rest upright in a plowed corn field. The wreckage was upright, and it sustained impact damage and was partially consumed by a postimpact fire. Other than minor debris, the wreckage was contained in one area. The farthest piece of wreckage from the main wreckage was the top engine cowling, which was located about 36 ft away. A burned area surrounded the wreckage, which extended out to a maximum of about 50 ft from the wreckage. The airplane came to rest in a NEAR-60° nose-down attitude, and the front of the engine was partially buried in the soft terrain. The propeller was buried in the ground with the tip of one of the blades visible. Examination of the airframe and engine was conducted on April 8 and 9, 2017, both on scene and in a hangar at the Iowa City Municipal Airport, Iowa City, Iowa. The examination was conducted by the National Transportation Safety Board (NTSB) investigator-in-charge and Federal Aviation Administration (FAA) inspectors, with the assistance of representatives of the engine and airframe manufacturers. Most of the fuselage and cockpit were consumed by the postimpact fire. Both wings were crushed aft and partially consumed by the fire. The empennage was separated from the fuselage. The vertical stabilizer and rudder remained attached to the stabilator. The right side of the vertical stabilizer and rudder and the right side of the stabilator sustained thermal damage. Control continuity was established from the flight controls to the cockpit. The engine sustained impact and thermal damage. All of the accessories, including both magnetos, were destroyed by the fire and could not be tested. A turning tool was inserted into the vacuum pump drive housing, and the engine was rotated by hand. It furnished suction and compression at all cylinders, and the rear accessory gears were observed turning. Valve train and crankshaft continuity were established throughout the engine. Examination of the airplane did not reveal any anomalies consistent with a preimpact failure or malfunction. A detailed summary of the examination is included in the public docket associated with the investigation. MEDICAL AND PATHOLOGICAL INFORMATIONThe UI Diagnostic Laboratories, Iowa City, Iowa, performed autopsies of the both the flight instructor and the pilot receiving instruction, and their deaths were attributed to multiple blunt force injuries. The FAA Bioaeronautical Research Sciences Laboratory, Oklahoma City, Oklahoma, performed toxicology testing for both pilots. Results for the flight instructor were negative for carbon monoxide, cyanide, and ethanol. The testing detected atorvastatin, ranitidine, and triamterene in the liver and cavity blood. Atorvastatin is a prescription medication used to lower cholesterol; ranitidine is a prescription and over-the-counter medication used to treat heart burn; and triamterene is a prescription diuretic used to treat high blood pressure. The pilot reported the use of these medications during his last FAA medical examination, and none of these medications are generally considered to be impairing. Results for the pilot receiving instruction were negative for carbon monoxide, cyanide, ethanol, and all drugs in the testing profile.