N91770

HISTORY OF FLIGHTOn November 9, 2018, about 1715 central standard time, a Piper PA28-236, N91770, was substantially damaged when it was involved in an accident near Guthrie Center, Iowa. The private pilot and three passengers were fatally injured. The airplane was operated as a Title 14 Code of Federal Regulations (CFR) Part 91 personal flight.

The pilot was flying the three passengers, one of whom was a student pilot and co-owner of the airplane, from Le Mars Municipal Airport (LRJ), Le Mars, Iowa, to Osceola Municipal Airport (I75), Osceola, Iowa, for a hunting trip.

Two witnesses reported observing the initial engine start. Both stated that the pilot made multiple attempts to start the engine, which resulted in loud popping and "backfire" sounds, but the engine would either not start or would not maintain idle power and would sputter to a stop. The restart attempts continued for about 1 minute, and on the final attempt, the engine started and rapidly accelerated to a speed so high that one witness was concerned that it could damage the cold engine. Both stated that the pilot then taxied the airplane to the fuel island at what they considered to be a high engine idle speed. After fueling, the passengers boarded. One witness stated that the takeoff and departure were uneventful, but he did notice before the airplane began its taxi that the insides of the windows were covered in mist.

According to air traffic control radar and voice communication information provided by the Federal Aviation Administration (FAA), about 1700 a controller observed a radar target squawking the 7700 emergency transponder beacon code, about 40 miles west of Des Moines International Airport (DSM), close to the town of Guthrie Center. Controllers established contact with the pilot of an airplane using a call sign of "Dakota 770" on the Guthrie County Regional Airport (GCT) common traffic advisory frequency. The pilot reported that he was a student, and that he was diverting to Perry Municipal Airport (PRO; about 20 miles east of the airplane's location) because the pilot who was flying the airplane was having a heart attack. No other communication from that airplane was received directly by the controllers; however, the pilots of two other aircraft on the frequency advised the controllers that they were able to communicate with the pilot, who reported that he was instead going to attempt to land at GCT.

By 1730, the airplane had not landed at either GCT or PRO, and an FAA Alert Notice (ALNOT) was issued.

The wreckage was located the following morning in an area of rolling hills and pastures at an elevation of 1,200 ft mean sea level (msl) 6 miles southwest of GCT.

Review of flight track data recorded by an onboard GPS receiver indicated that after departing LRJ, the airplane followed an almost direct southeast track for about 40 minutes at an altitude of about 4,000 ft msl, before reaching the Guthrie Center area. At 1701, the airplane made a 90° left turn towards the general direction of GCT, followed by a counter-clockwise (left-turning) 3-mile-wide orbit around GCT at an altitude of about 3,500 ft msl (1,300 ft agl). The airplane then proceeded to fly southwest towards the town of Guthrie Center, and after passing east of the town, it initiated a descending right turn, reaching an altitude of 1,513 ft (400 ft agl), about 2 miles to the south of town. It then proceeded to fly north and make a right turning orbit around the town climbing, descending, and then climbing again until it reached 2,800 ft at 1713. The airplane then turned to a southwest track and descended to the last recorded location. That location was at an altitude of 2,560 ft, about 2 1/2 miles northeast of the accident site (Figure 1). Ground speeds during the maneuvers over Guthrie Center ranged between 83 and 174 knots.

Figure 1 – GPS ground track and final stages of flight (inset). Projected flight track in red (North up).

AIRCRAFT INFORMATIONThe student pilot had purchased the airplane in June 2018. According to the other co-owner, the airplane had accumulated about 100 hours total flight time during the period between purchase and the accident, and the student had flown the airplane solo on multiple occasions.

Maintenance and Muffler History

According to the airplane's maintenance records, a new logbook was created on August 27, 1991, because the previous logbooks were lost. At the time the logbook was created, the airframe had accrued a reported 1,922.58 hours time in service (TIS).

A logbook entry indicated that two of the three mufflers were replaced on August 12, 2002, at 2,203.64 hours airframe TIS (752 flight hours before the accident), but the positions of those two replaced mufflers were not specified. Subsequent entries noted that the forward muffler was replaced on January 23, 2008, at 2,689 airframe hours TIS, and the middle muffler was replaced on March 1, 2012, at 2,752 airframe hours TIS. Therefore, at least one of the mufflers installed in 2002 was replaced at less than 549 hours TIS.

None of the maintenance log entries in the 1,033 hours since 1991 specifically mentioned replacement of the aft muffler. The forward muffler was the only one that displayed a part and serial number. Each of the mufflers were constructed slightly differently, suggesting that they were likely from different manufacturers.

The airplane's most recent annual inspection was completed on November 3, 2018, at an airframe time of 2,955 hours. The mechanic who performed the most recent annual inspection stated that he spent about 22 hours inspecting and servicing the airplane. He provided a copy of the Piper maintenance manual that he used to perform the inspection, which included a section devoted to exhaust system examination. He specifically recalled disassembling the heat exchanger assembly and exhaust mufflers and stated that the accident pilot helped him remove the heat exchanger shroud. He stated that he checked the mufflers and shroud for cracks, deformation, and discoloration, and found none.

Based on statements provided by the airport manager and the mechanic, the accident flight was likely the first since the inspection.

The airplane was not equipped with any type of CO detector, nor was it required to be. The last time the cabin heat was likely used was on October 12, 2018. The pilot who flew it that day reported that he did not notice the smell of exhaust fumes during the flight or experience any symptoms of what he considered to be CO poisoning, such as headaches or dizziness.

METEOROLOGICAL INFORMATIONAccording to the National Oceanic and Atmospheric Administration, sunset in Guthrie Center occurred at 1703.

Temperatures for area airports around the time of the accident were about –7°C, with clear skies, broken cloud conditions, and visibilities of 10 miles or greater.

AIRPORT INFORMATIONThe student pilot had purchased the airplane in June 2018. According to the other co-owner, the airplane had accumulated about 100 hours total flight time during the period between purchase and the accident, and the student had flown the airplane solo on multiple occasions.

Maintenance and Muffler History

According to the airplane's maintenance records, a new logbook was created on August 27, 1991, because the previous logbooks were lost. At the time the logbook was created, the airframe had accrued a reported 1,922.58 hours time in service (TIS).

A logbook entry indicated that two of the three mufflers were replaced on August 12, 2002, at 2,203.64 hours airframe TIS (752 flight hours before the accident), but the positions of those two replaced mufflers were not specified. Subsequent entries noted that the forward muffler was replaced on January 23, 2008, at 2,689 airframe hours TIS, and the middle muffler was replaced on March 1, 2012, at 2,752 airframe hours TIS. Therefore, at least one of the mufflers installed in 2002 was replaced at less than 549 hours TIS.

None of the maintenance log entries in the 1,033 hours since 1991 specifically mentioned replacement of the aft muffler. The forward muffler was the only one that displayed a part and serial number. Each of the mufflers were constructed slightly differently, suggesting that they were likely from different manufacturers.

The airplane's most recent annual inspection was completed on November 3, 2018, at an airframe time of 2,955 hours. The mechanic who performed the most recent annual inspection stated that he spent about 22 hours inspecting and servicing the airplane. He provided a copy of the Piper maintenance manual that he used to perform the inspection, which included a section devoted to exhaust system examination. He specifically recalled disassembling the heat exchanger assembly and exhaust mufflers and stated that the accident pilot helped him remove the heat exchanger shroud. He stated that he checked the mufflers and shroud for cracks, deformation, and discoloration, and found none.

Based on statements provided by the airport manager and the mechanic, the accident flight was likely the first since the inspection.

The airplane was not equipped with any type of CO detector, nor was it required to be. The last time the cabin heat was likely used was on October 12, 2018. The pilot who flew it that day reported that he did not notice the smell of exhaust fumes during the flight or experience any symptoms of what he considered to be CO poisoning, such as headaches or dizziness.

WRECKAGE AND IMPACT INFORMATIONThe main wreckage, which included the cabin, both wings and the empennage, came to rest facing uphill on a heading of about 270° magnetic. The first identified point of impact was located about 25 ft southeast of the main wreckage and comprised three 18-inch-long by 8-inch-wide divots, the relative positions of which matched the main landing and nose gear. A crater several feet away displayed two matching linear impact marks extending from either side, the total length of which corres...