N314BFCirrus Design SR20 · 2000

On August 13, 2016, about 1001 central daylight time, a Cirrus Design Corporation SR20 airplane, N314BF, had 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 descended into power lines and terrain. The airplane was subsequently destroyed by a postimpact fire. The pilot and 2 passengers sustained minor injuries. An additional passenger was not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight.

The pilot reported that he did not observe any airframe or engine anomalies during his preflight inspection. He also noted that the fuel tanks were completely full, and that he did not observe any contamination in the fuel samples that he obtained during his preflight inspection. The pilot reported that the engine started without hesitation and idled normally before taxi, and that he did not observe any anomalies during his before takeoff engine run-up.

A normal takeoff was made on runway 31 from the taxiway Romeo intersection with the wing flaps set at 50%, the electric fuel pump selected to boost, and the mixture-control set to full rich. The pilot reported that the engine instrumentation indicated normal readings during the takeoff run and that liftoff was achieved at 70 knots indicated airspeed (KIAS). After liftoff, the pilot reduced airplane pitch and accelerated to 90-95 KIAS before he retracted the wing flaps. The pilot reported that during the initial climb, about 500 ft above ground level (agl), he heard and felt a sudden reduction in engine power. He told the tower controller that he had engine trouble and requested an immediate landing. The tower controller cleared the pilot to enter a right downwind for landing on runway 31. The pilot reported that he was unable to maintain altitude and, as a result, he deployed the CAPS. After a successful parachute deployment, the airplane contacted power lines shortly before it impacted the ground at the intersection of Park Avenue and SW 56th Street. The pilot remarked that the airplane had landed "remarkably soft" in a nose level attitude. After landing, a fire erupted from under the left wing and the pilot told his passengers to evacuate from the right cabin door. The airplane was subsequently destroyed by the postimpact fire.

The airplane was a four-place single engine low-wing airplane of primarily composite construction. The airplane was powered by a 6-cylinder, 200 horsepower, Continental Motors IO-360-ES16B engine, serial number 1000059, which drove a two-blade Hartzell model BHC-J2YF-1BF/F7694 constant speed propeller. According to airplane logbook entries, the most recent annual inspection was completed on May 19, 2016, at 1,565.6 hours total airframe time. As of the annual inspection, the engine had accumulated 555.1 hours since it was rebuilt at the factory on March 20, 2009. A review the engine logbook only revealed one maintenance entry, dated February 10, 2012, at 181.5 hours total engine time, in which the induction system was specifically mentioned as having been inspected. However, further review the engine logbook was inconclusive if the induction system tubes had been removed for maintenance in the 7.4 years since the engine had been rebuilt. According to the pilot, the airplane had accumulated about 66.5 flight hours since the last annual inspection.

The engine and propeller were not damaged by the postimpact fire. The engine remained attached to the firewall and the propeller remained attached to the crankshaft flange. The propeller exhibited torsional twisting, S-shaped spanwise bends, leading edge damage, and burnishing of the blade face and back. Internal engine and valve train continuity was confirmed as the engine crankshaft was rotated. Compression and suction were observed on all cylinders in conjunction with crankshaft rotation, and both magnetos provided spark at all leads. The sparkplugs for cylinder Nos. 4 and 5 exhibited excessive black soot, consistent with an over-rich fuel/air mixture. The remaining sparkplugs exhibited features consistent with normal engine operation. A borescope inspection of each cylinder did not reveal any anomalies. Additionally, no anomalies were observed with the fuel servo, mechanical fuel pump, fuel flow divider, or fuel injectors. A disassembly of the oil filter did not reveal any metal debris. The induction tube coupler closest to the No. 1 cylinder, part number (p/n) 654439-16, was observed partially disconnected from its associated induction tube. Although both coupler clamps were tight, the clamp, p/n AN737TW74, closest to the No. 1 cylinder did not overlap its associated induction tube. Additionally, the cylinder No. 3 induction tube, p/n 655224-1, was fractured at the cylinder mounting flange.

The fractured No. 3 induction tube, p/n 655224-1, was submitted to the National Transportation Safety Board (NTSB) Materials Laboratory for additional examination. A visual examination confirmed that the mounting flange of the induction tube had fractured from the main body of the tube. An additional attachment flange that had been installed between the induction tube flange and the engine cylinder did not exhibit any discernible damage. Several measurements of the induction tube revealed it was deformed in multiple directions such that the measurements at various locations produced inconsistent data. The tube inner diameter measured 1.624 inches, and the outer diameter measured between 1.742 and 1.767 inches. The tube thickness ranged between 0.705 and 0.735 inches. The manufacturer drawing dimension AB measured 2.822 inches, and the AC line measured about 2.6 inches. The fracture between the flange and the remaining tube was circumferential in orientation and perpendicular to the tube direction. The flange had also fractured in two additional locations longitudinally, creating two flange fragments. In general, the mating fracture surfaces exhibited a flat orientation, with some other areas exhibiting a 45° fracture orientation. The fracture surfaces exhibited smearing and rub marks, consistent with post-fracture damage. Examination of the flange-side fracture surface with a scanning electron microscope revealed fatigue striations, consistent with fatigue crack propagation. The character and spacing of the striations were consistent with high-cycle fatigue. The likely initiation sites of the fatigue had been destroyed by the post-fracture smearing. The chemical composition of the fractured induction tube flange was determined by energy dispersive x-ray spectroscopy (EDS) and was consistent with an AA 6061-series aluminum alloy. The results of material electrical conductivity and hardness testing were consistent with those typical of the 6061-O aluminum alloy in the annealed condition. The chemical composition, electrical conductivity, and hardness values were consistent with the engine manufacturer's part specification.