Accident Details
On October 26, 2018, about 0730 mountain daylight time, a Piper PA-28, registration N5575U, was substantially damaged when it was involved in an accident near Denver, Colorado. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The commercial pilot and a pilot-rated passenger were not injured.
Pilot's Account
The pilot reported that he completed the preflight inspection, started the engine on the left fuel tank, then switched to the right fuel tank during taxi to the runup area. He conducted a normal engine runup, checking the carburetor heat and magnetos twice. After receiving a weather briefing and opening his flight plan, he was cleared for takeoff from runway 17L. The pilot noted that the takeoff roll was "a little longer than normal," which he attributed to the weight of the airplane’s full fuel tanks and the passenger.
During the initial climb, the airplane achieved 400 to 500 feet per minute. The pilot observed that the climb rate was deteriorating and the stall warning light was flashing intermittently. He pitched down, verified the throttle was at full power and the fuel/air mixture was full rich, then applied carburetor heat and retracted the flaps. After applying carburetor heat, the pilot noticed a decrease in rpm and concluded that carburetor ice was not a factor based on "no engine roughness" before turning on carburetor heat and the atmospheric conditions. He subsequently turned the carburetor heat off. The airplane’s climb performance continued to degrade, and shortly thereafter, the airplane began to descend. The pilot performed a forced landing to a field. During the landing, the engine "seemed to lose power," then briefly surged just before touchdown.
Examination
A Federal Aviation Administration (FAA) inspector reported that the airplane came to rest upright 2 miles and 195° from the departure end of runway 17L. The airplane remained intact; however, the nose and main landing gear were separated from the fuselage, the right wing leading edge was damaged, and the empennage skin was wrinkled. One propeller blade exhibited aft bending and chordwise scratching. Fuel was present in both wing tanks.
The engine crankshaft was rotated by hand, and internal and valvetrain continuity was established. Fuel was present throughout the fuel lines and was absent of any water and debris. The fuel gascolator was dry and the gascolator screen was free of debris and contamination. Power was applied to the electric fuel pump and it functioned normally. The engine-driven fuel pump was actuated by turning the propeller and it functioned normally. Both magnetos produced spark at all towers. There was no evidence of any preimpact mechanical malfunctions or failures that would have precluded normal engine operation.
Weather Conditions
The 0653 weather reported at Centennial Airport (APA) included a temperature of 3°C and a dew point of -3°C. The calculated relative humidity was about 66.8%. According to an FAA Carburetor Icing Probability Chart, the atmospheric conditions at the time of the accident were conducive to serious icing at cruise power settings. FAA Special Airworthiness Information Bulletin (CE-09-35) – Carburetor Icing Prevention, stated that pilots should be aware that carburetor icing can occur at temperatures well above freezing when there is visible moisture or high humidity, and that carburetor ice can be detected by a drop in rpm in fixed pitch propeller airplanes.