The flight instructor told investigators that he and the commercial-rated pilot receiving instruction were completing a multi-engine training flight, which was their first multi-engine training flight together. The flight instructor had accumulated 115 flight hours in the Tecnam P2006T, all of which were completed while acting as a flight instructor.
During the first portion of the flight, they completed five full-stop, taxi-back landings at Centennial Airport (KAPA) in Englewood, Colorado. After the final landing, they proceeded to the southwest and climbed to 10,800 feet mean sea level (about 4,500 feet above ground level), where they intended to practice training procedures in the North Perry practice area designated for multi-engine training.
They initially completed directional control exercises and multiple simulated engine-out emergencies so the pilot receiving instruction could understand the step-by-step process. Next, they shut down the left engine by turning the left ignition switches to OFF.
With the engine secured and the propeller feathered, the pilot maneuvered the airplane for “a little bit” until they attempted to the restart the engine. They referenced the engine restart checklist and attempted to restart the engine, but were unsuccessful. They waited about five seconds, then engaged the starter buttons again and the engine restarted successfully. They slowly increased the left engine throttle and completed the cruise checklist before proceeding back toward KAPA.
While en route, the CFI noted that the airplane required additional right rudder to maintain control. The pilot took over the controls and confirmed that more right rudder was required. The flight instructor noted that the left engine coolant temperature and RPM had decreased, so he took back the controls and proceeded to Perry Park Airport (CO93) in Larkspur, Colorado, which was about 4 nm south of their location.
After completing a 180° turn to south, he secured the left engine and feathered the propeller. The airplane was difficult to control and was rapidly losing altitude.
When he realized that they could not reach CO93, he set up to land on Interstate 25 (I-25). Just before landing in the southbound lanes of I-25, he pitched up and banked left to avoid hitting southbound vehicles. The airplane climbed over the traffic, then hit a marshy area to the east of I-25.
The airplane came to rest inverted in a swampy area 0.17 nm east of the runway at CO93 and sustained substantial damage. Both the CFI and pilot were seriously injured in the crash.
The pilot receiving instruction reported that he had previously accumulated two hours in the accident airplane make and model, which was his only multi-engine flight experience. He added that when they turned toward CO93 and secured the left engine, they were not sure if the propeller was fully feathered.
Witness videos showed that the airplane descended over I-25 with the right propeller rotating and the left propeller not rotating. The left wing hit a road sign, veered left, and climbed over the oncoming traffic. The end of the accident sequence was not captured in the video.
Post-accident examination of the airplane revealed that the left propeller lever was found retarded but not in the feathered position. The lever sustained damage and was bent right about 90° and the pedestal upper cover was bent to the right in the same area as the lever was bent over. The left throttle lever was found retarded about mid travel. The carburetor heat levers were positioned to OFF.
The left and right engines were examined and prepared for functional test runs. Both engines were run successfully at various power settings. There were no pre-impact mechanical malfunctions or failures found during the examination or engine functional test runs that would have precluded normal operation.
A review of the Carburetor Icing Probability Chart in the FAA’s Special Airworthiness Information Bulletin CE-09-35, Carburetor Icing Prevention, dated June 30, 2009, indicated that the atmospheric conditions in which the airplane was operating were conducive to the formation of serious icing at glide power settings.
The aircraft flight manual, Section 4: Normal procedures (2.2 Single engine training), stated: “The best practice to perform single engine training is to retard one engine to the flight parameters equivalent to a dead engine. A simulated feather condition is obtained with propeller lever full forward and throttle lever set at 13.5 in Hg MAP (manifold pressure) at 70-90 KIAS (knots indicated airspeed) and 2,000-4,000 feet density altitude.”
“In normal operations, shutting down an engine for training shall not become a habit, in particular for safety reasons and in order to optimize training,” it continued, noting engine shutdown “shall be executed only when required by regulations (e.g. during flight check, skill tests, or demonstration as per 14 CFR Part 61 or equivalent rule).”
The manual also notes that “continuous operation of engine securing for training may indeed cause long term damages to the engine itself due to the high load coming from propeller (which is in feathering angle during the engine re-starting).”
Probable Cause: The flight instructor’s failure to apply carburetor heat, which resulted in a loss of left engine power due to carburetor icing.
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This June 2024 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.
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