Pilot Debrief

CESSNA 182C near Boulder, CO — 2011-08-09

Final reportCEN11FA559
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Date
2011-08-09
Location
Boulder, CO, USA
Aircraft
CESSNA 182C
Registration
N8717T
Category
Airplane
Highest injury
Minor
Fatalities
0
Phase of flight
Descent

Probable cause

The malfunction of the throttle linkage to the induction air box, which resulted in a loss of engine power and subsequent forced landing.

NTSB narrative

After two parachutists jumped from the airplane, the pilot began a descent and applied carburetor heat. The pilot reduced power for a straight-in approach while the airplane was passing through 9,000 feet mean sea level and about 3 miles from the destination airport. She then attempted to add power to adjust the descent rate, but the engine did not respond. The pilot then fully reduced the engine power then tried to advance the throttle with no response. After performing the power loss checklist, she continued toward the runway but, after encountering a downdraft, she chose to conduct a forced landing to an open field. Upon touchdown, the airplane collided with trees at the edge of the field. The propeller assembly was found attached to the engine hub, and both blades were straight with little damage consistent with them not being powered at the time of impact. About 5 gallons of fuel were drained from the left fuel tank and about 0.5 gallon was drained from the right fuel tank. The fuel selector was found in the "both" position. Because of the fuel leakage due to impact damage, it was not possible to determine exactly how much fuel was onboard at the time of the accident; however, enough fuel was present in the lines to determine that fuel starvation did not occur. No evidence of debris, obstructions, or water contamination was identified in the fuel gascolator. About 8.5 quarts of oil were found in the engine. Some oil residue was found on the belly skin of the airplane and was identified to have originated from an aftermarket oil drain installation. The front underside of the airframe was damaged and pushed upward underneath the engine compartment near the air induction box. When moved by hand, the throttle linkage to the air induction box did not move smoothly and was stiff. The throttle linkage to the induction box was adjusted, and the engine was test run while still in the airframe mounts. It started normally and ran at various power settings with no anomalies noted. Throughout the engine test run, the engine accelerated normally. A magneto rpm drop check was normal. The damage underneath the engine compartment near the box precluded a determination of whether the throttle linkage anomaly was present before impact. However, given that the engine ran normally after the throttle linkage adjustment, it is likely that the throttle linkage anomaly did occur before impact and contributed to the loss of engine power.

Analysis

Primary failure mode
Engine power loss
First missed decision gate
Pilot could have aborted the approach after initial power loss.

NTSB coding

Evidence available

  • Photos
  • 10 docket documents
View NTSB final reportView NTSB docket

Docket documents10

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