Accident Overview
On July 9, 2008, at approximately 1646 Pacific daylight time, a Cessna 172RG, registration N9627B, experienced a partial loss of engine power while maneuvering about 3 miles east-southeast of Moorpark, California. The aircraft was operated by American Flyers of Santa Monica, California, under 14 CFR Part 91 as a local instructional flight. The flight had departed from Santa Monica Municipal Airport at about 1515. Visual meteorological conditions prevailed, and no flight plan was filed.
Flight and Loss of Power
The certified flight instructor (CFI) was accompanied by a private pilot who was undergoing the final flight phase check for a commercial pilot certificate under the FAA-approved school's Part 141 examination authority. The CFI directed the student to perform a ground reference maneuver (eights on pylons) over a field. The student descended to 1,000 feet above ground level and attempted to increase throttle to level out, but the engine power did not increase. The CFI verified the problem and decided to execute an emergency landing.
Emergency Landing
The CFI set the transponder to squawk 7700 and attempted to declare an emergency to nearby air traffic control. Due to low altitude, the transmission was not heard by ATC, but another aircraft's pilot relayed the distress call. As the airplane descended toward the chosen forced landing site, the CFI executed a 180-degree turn with full flaps and landing gear extended, and entered a full slip. The engine continued to develop idle power. The airplane touched down on upsloping terrain and impacted a rocky berm, nosing over. Both pilots sustained minor injuries, and the aircraft was substantially damaged.
Investigation Findings
Post-accident examination revealed that the throttle control cable was disconnected at its carburetor rod end attachment fitting. The cable's threaded bolt end showed no evidence of thread deformation, nor did the carburetor's rod end attachment fitting. The jam nuts on the control cable were tight against each other but were not positioned close enough to the rod end to secure the cable to the carburetor. Additional assembly discrepancies were noted with the throttle cable attachment. Chordwise scratches were observed on both propeller blades, but no evidence of pre-impact oil leakage was found. All flight control surfaces were accounted for, and neither pilot reported preimpact flight control malfunction.
Maintenance Discrepancies
Investigators examined the operator's fleet of airplanes based in Santa Monica. The operator employed two full-time mechanics, including a maintenance director with inspection authorization. The accident airplane's last 100-hour inspection was performed on July 3, 2008, six days before the accident. Examination of six other Santa Monica-based airplanes revealed maintenance anomalies with each, including jam nuts on throttle control cables not properly positioned. In one instance, turning the cockpit throttle control knob counterclockwise 20 full rotations caused the control cable to disconnect from the rod end housing at the carburetor. The operator, after participation in the investigation, took action to address the airworthiness issues, reinforced squawk reporting procedures, and enhanced management oversight of flight and maintenance departments across its nationwide operations.