Event Summary
On August 13, 2016, about 1001 central daylight time, a Cirrus Design Corporation SR20 airplane, registration N314BF, experienced a partial loss of engine power shortly after takeoff from Des Moines International Airport (DSM), Des Moines, Iowa. The pilot deployed the Cirrus Airframe Parachute System (CAPS), and the airplane descended into power lines and terrain. A postimpact fire destroyed the airplane. The pilot and two passengers sustained minor injuries; another passenger was not injured. The flight was conducted under Title 14 Code of Federal Regulations Part 91 as a personal flight.
Flight and Pilot Actions
The pilot performed a preflight inspection without observing any airframe or engine anomalies. The fuel tanks were full, and fuel samples showed no contamination. The engine started normally and idled before taxi, and the before-takeoff run-up revealed no issues. A normal takeoff was made on runway 31 from the taxiway Romeo intersection with wing flaps at 50%, electric fuel pump on boost, and mixture full rich. After liftoff at 70 knots indicated airspeed (KIAS), the pilot reduced pitch and accelerated to 90-95 KIAS before retracting flaps. During initial climb at about 500 ft above ground level, the pilot heard and felt a sudden reduction in engine power. He informed the tower controller of engine trouble and requested an immediate landing. The controller cleared the pilot for a right downwind to runway 31, but the pilot was unable to maintain altitude and deployed the CAPS. After parachute deployment, the airplane contacted power lines before impacting the ground at the intersection of Park Avenue and SW 56th Street. The pilot described the landing as "remarkably soft" in a nose-level attitude. After landing, a fire erupted from under the left wing, and the pilot evacuated through the right cabin door.
Airplane and Engine Information
The airplane was a four-place, single-engine, low-wing aircraft of primarily composite construction, powered by a 6-cylinder, 200-horsepower Continental Motors IO-360-ES16B engine, serial number 1000059, driving a two-blade Hartzell constant speed propeller (model BHC-J2YF-1BF/F7694). The most recent annual inspection occurred on May 19, 2016, at 1,565.6 total airframe hours. The engine had accumulated 555.1 hours since its factory rebuild on March 20, 2009. The engine logbook showed only one maintenance entry mentioning induction system inspection on February 10, 2012, at 181.5 engine hours; it was inconclusive whether induction system tubes had been removed for maintenance since the rebuild. The airplane had about 66.5 flight hours since the last annual inspection.
Post-Accident Examination
The engine and propeller were not damaged by the postimpact fire. The engine remained attached to the firewall, and the propeller to the crankshaft flange. The propeller exhibited torsional twisting, S-shaped spanwise bends, leading edge damage, and burnishing. Internal continuity was confirmed by rotating the crankshaft; compression and suction were present on all cylinders, and both magnetos sparked at all leads. Sparkplugs for cylinders No. 4 and 5 showed excessive black soot, indicating an over-rich mixture; others appeared normal. Borescope inspection of cylinders revealed no anomalies. No anomalies were found in the fuel servo, mechanical fuel pump, fuel flow divider, or fuel injectors. The oil filter contained no metal debris. The induction tube coupler nearest cylinder No. 1 (part number 654439-16) was partially disconnected; both clamps were tight, but the clamp closest to No. 1 cylinder did not overlap its induction tube. Additionally, the cylinder No. 3 induction tube (part number 655224-1) was fractured at the cylinder mounting flange.
Metallurgical Examination of Induction Tube
The fractured No. 3 induction tube was examined at the NTSB Materials Laboratory. Visual examination confirmed the flange had fractured from the main tube. An additional attachment flange between the induction tube and cylinder showed no damage. The tube was deformed in multiple directions; measurements varied. Tube inner diameter was 1.624 inches, outer diameter between 1.742 and 1.767 inches, thickness between 0.705 and 0.735 inches. Fracture surfaces had flat and 45° orientations, with smearing and rub marks from post-fracture damage. Scanning electron microscopy revealed fatigue striations consistent with high-cycle fatigue crack propagation. Likely initiation sites were destroyed by smearing. Chemical composition (EDS) matched AA 6061-series aluminum alloy; electrical conductivity and hardness were consistent with 6061-O annealed condition. These values met the engine manufacturer's specifications.