CEN15FA048

The pilot's failure to maintain airspeed while attempting to return to the airport after a reported engine problem, which resulted in an aerodynamic stall/spin.

The commercial pilot was conducting an on-demand cargo charter flight. Shortly after takeoff, the pilot informed the tower controller that he wanted to "come back and land" because he was "having trouble with the left engine." The pilot chose to fly a left traffic pattern and return for landing. No further transmissions were received from the pilot. The accident site was located about 0.50 mile southeast of the runway's displaced threshold. GPS data revealed that, after takeoff, the airplane entered a left turn to a southeasterly course and reached a maximum GPS altitude of 959 ft (about 342 ft above ground level [agl]). The airplane then entered another left turn that appeared to continue until the final data point. The altitude associated with the final data point was 890 ft (about 273 ft agl). The final GPS data point was located about 135 ft northeast of the accident site. Based on GPS data and the prevailing surface winds, the airspeed was about 45 knots during the turn. According to the airplane flight manual, the stall speed in level flight with the wing flaps extended was 59 knots. Postaccident examination and testing of the airframe, engines, and related components did not reveal any preimpact mechanical failures or malfunctions that would have precluded normal operation; therefore, the nature of any issue related to the left engine could not be determined. Based on the evidence, the pilot failed to maintain adequate airspeed while turning the airplane back toward the airport, which resulted in an aerodynamic stall/spin.

MDW is located about 9 miles southwest of the main business district and within the city limits. The airport elevation is 620 ft. It is served by two primary runways: runway 13C-31C is 6,522 ft long by 150 ft wide; runway 4R-22L is 6,445 ft long by 150 ft wide. Both runways are constructed of grooved concrete/asphalt. The airport is also configured with three additional parallel runways. Airport operations are supported by an air traffic control tower. The Chicago Terminal Radar Control facility provides air traffic control services for the surrounding airspace. Computed tomography (CT) scans of the left PG revealed that the flyweights were positioned near the top of the flyweight cavity consistent with the flyweight being dislocated from the driveshaft. The governor bearings appeared to be intact. The scans also revealed a fragment within the flyweight cavity. The scans were otherwise unremarkable. CT scans of the right PG did not reveal any anomalies. The flyweight mechanism was located at the bottom of the flyweight cavity and the driveshaft appeared to be properly seated. The bearings appeared to be intact. Both PGs were bench tested in accordance with the manufacturer's specifications. Before testing, the left governor housing was opened and the flyweight mechanism was reseated onto the driveshaft spline. The fragment identified by the CT scan was not observed. The housing was resealed. No other modifications were made to the component. The right propeller governor was tested as recovered. The left PG tested within specification, except at three data points: 1) the pump capacity was 3.99 quarts per minute, which was below the minimum of 5.0 quarts per minute; 2) the feathering speed was 1,527 rpm, which was below the minimum of 1,555 rpm; and 3) the internal component leakage was 60 quarts per hour, which was above the maximum of 30 quarts per hour. The right PG tested within specification, except at three data points: 1) the relief valve pressure was 256 pounds per square inch (psi), which was below the minimum of 260 psi; 2) the pump capacity was 4.24 quarts per minute, which was below the minimum of 5.0 quarts per minute; and 3) the internal component leakage was 60 quarts per hour, which was above the maximum of 30 quarts per hour. The left fuel servo injector was examined and bench tested in accordance with the manufacturer's specifications. The throttle input shaft was free to rotate. The mixture input shaft was stiff, but rotated through the full range of travel. The shaft and mixture lever were bent consistent with impact forces. The component exceeded the production flow limits established by the manufacturer at each test point. A subsequent teardown examination determined that the mixture control shaft and the idle valve shaft were deformed. Preflight and Flight Information A worksheet recovered from the airplane denoted a total of six flight segments. The segments and estimated departure/arrival times were: Rickenbacker International Airport (LCK) (2120) to Burke Lakefront Airport (BKL) (2230), BKL (2300) to Willow Run Airport (YIP) (2355), and YIP (0015) to MDW (0130), MDW (0140) to Chicago Executive Airport (PWK) (0200), PWK (0230) to OSU (0400), and OSU to LCK as a "deadhead" segment. A load manifest dated November 17, 2014, was recovered from the airplane, and it listed the pilot as the pilot-in-command. The actual departure and arrival times were denoted as LCK (2123) to BKL (2228), BKL (2318) to YIP (0008), and YIP to MDW (0137). Based on the manifest, 58 gallons of fuel were obtained before departing LCK and 40 gallons of fuel were obtained before departing YIP. A representative of the fixed base operator at MDW stated that the pilot requested a ground power unit to assist with starting the engines before departure from MDW. The pilot requested no other services. The airplane was not fueled during the stop at MDW. The pilot reportedly informed FBO personnel that the heater in the airplane was not working properly. He subsequently got the heater working and let it run to warm the cabin. A representative of the operator stated that the pilot was running about 45 minutes behind schedule due to a delay at BKL. As a result, the courier brought the PWK cargo to MDW for loading, eliminating the need for the MDW to PWK segment. Airspeed Information Approximate heading and airspeed information was extracted from the available GPS track and ground speed data. Due to the proximity to the airport, the MDW surface wind at the time of the accident was used. The data indicated that, during the initial climb and turn, the airplane maintained about 73 knots airspeed. The airplane accelerated to 97 knots during the downwind portion of the flight. The airspeed steadily decreased into the final turn. The airspeed between the final data points was approximately 45 knots. According to the airplane flight manual, the stall speed in level flight with the wing flaps extended was 59 knots (68 miles per hour). The Cook County Medical Examiner's Office attributed the pilot's death to multiple blunt force injuries sustained in the accident. The FAA Bioaeronautical Sciences Research Laboratory performed toxicology testing of specimens from the pilot. The results were negative for all substances in the testing profile, including alcohol and carbon monoxide. The airplane impacted and came to rest within a home. The southwest corner of the home was destroyed. The left wing was located outside the home with the wing tip resting on the ground. The right wing remained attached to the fuselage and the outboard portion of the wing extended the roof of the adjacent home. The aft fuselage/empennage came to rest on the roof of the adjacent home. The homes were separated by about 10 ft. The forward fuselage and wings were oriented on magnetic heading of 030°; the aft fuselage and empennage were oriented on magnetic heading of 005°. The fuselage nose section and cockpit area were fragmented. The center fuselage section was deformed consistent with impact forces. The fuselage structure was buckled in-line with the trailing edge of the wings. The fuselage aft of the buckled area and the empennage appeared intact. The elevator and rudder control surfaces remained attached to the horizontal and vertical stabilizers, respectively. Flight control continuity was confirmed from each control surface within the empennage/aft fuselage section. Both wings remained attached to the fuselage. The left wing was deformed from the engine pylon outboard. The inboard portion of the wing between the fuselage and the engine pylon exhibited leading edge impact damage. The forward portion of the engine pylon structure was damaged consistent with impact forces. The engine was separated from the airframe except for the control cables, which retained the engine assembly. The engine was in position relative to the airframe at the accident site. The propeller assembly remained attached to the engine. The left main landing gear was in the extended position. The left aileron and wing flaps remained attached to the wing. The wing flaps were deflected approximately 30°. No anomalies consistent with a preimpact failure or malfunction related to the left aileron or wing flap control continuity were observed. The right wing exhibited leading edge impact damage over the span of the wing. The outboard portion of the wing was displaced downward at the inboard side of the engine pylon. The forward portion of the engine pylon was damaged consistent with impact forces. The right engine had separated from the pylon and the right propeller had separated from the engine; both were located within the home. The right main landing gear was in the extended position. The right aileron and outboard flap section remained attached to the wing. The inboard flap section remained attached at the outboard hinge fitting. No anomalies consistent with a preimpact failure or malf