History of Flight
On May 9, 2008, at 2037 eastern daylight time, a Cessna 208B (registration N893FE) operated by CSA Air, Inc., as a Title 14 CFR Part 135 cargo flight, sustained substantial damage during a forced landing following a loss of engine power. The flight originated from Cherry Capital Airport in Traverse City, Michigan, around 2000, and was on an instrument flight rules flight plan to Gerald R. Ford International Airport in Grand Rapids, Michigan. The pilot was conducting a visual approach to runway 26L when engine power was lost. Visual meteorological conditions prevailed.
Personnel Information
The pilot held a commercial pilot certificate with single-engine land, multi-engine land, and instrument airplane ratings. His most recent flight review was on February 20, 2008, in the same aircraft model. He held a second-class medical certificate issued February 12, 2008. He reported 5,600 total flight hours, including 3,450 hours in the accident make and model.
Aircraft Information
The 1990 Cessna 208B, serial number 208B0223, was a strut-braced high-wing airplane with fixed landing gear, powered by a single Pratt & Whitney PT6-114A turboprop engine rated at 675 horsepower. It was maintained under an approved airworthiness inspection program (AAIP) and had 8,625 hours time in service as of its last inspection on March 18, 2008. The engine had 8,836 total hours, 675 hours since overhaul, and 60 hours since the March 18 inspection.
Meteorological Information
At 1953, weather at GRR included winds from 320 degrees at 9 knots, visibility 10 statute miles, few clouds at 6,000 feet, overcast at 12,000 feet, temperature 15°C, dew point 3°C, altimeter 29.83 inches of mercury.
Communications
The flight, using call sign "iron air 7343," was in contact with GRR tower. It was cleared for a visual approach to runway 26L and instructed to descend to 2,500 feet msl. The pilot later reported loss of engine power and stated there was one person and 800 pounds of fuel onboard. No further transmissions were made.
Wreckage and Impact Information
The airplane touched down in a field of tall grass and struck trees at the field's edge. The left wing separated at the root; the right wing separated mid-span. The nose landing gear collapsed, and propeller blades were bent rearward with little rotation evidence. Grass and dirt debris were found in cowling intakes. Engine control continuity from cockpit to engine was confirmed. Compressor and power turbine blades appeared intact; shafts rotated freely. Fuel was present in lines; fuel samples tested negative for water. No obstructions were found in fuel or vent lines.
The fuel boost pump passed factory acceptance testing. The engine and fuel controls were examined at Pratt & Whitney in Longueuil, Quebec. A crack was observed on the engine scavenge pump housing, but it could not be determined if it existed prior to impact. An engine run was not performed due to the crack. The engine core was disassembled; turbine blades and disc were intact, and unburned grass in the gas generator case and combustor confirmed the engine was not running at the time of grass ingestion.
The fuel control unit (FCU) and fuel pump were tested as a unit. Low-speed testing revealed pressure and fuel flow fluctuations that could not be reliably duplicated. Some test parameters were outside manufacturing tolerances but were attributed to permissible field adjustments and would not have caused a power loss. The FCU minimum pressurizing valve was noted to be potentially sticky; if it slammed closed during deceleration, it could cause a flameout. The valve was disassembled, and axial scoring was found on the plunger and housing, with embedded silicon particles. However, the scoring depth (0.00006 inches) relative to radial clearance (0.0015 to 0.0025 inches) was too small to determine if the valve stuck due to contamination. Testing of other fuel system components revealed no anomalies that would have resulted in a loss of engine power.
Tests and Research
The aircraft was equipped with a Power Analyzer and Recorder (PAR). Data from the PAR confirmed an engine shutdown near the time the pilot reported loss of power, but did not indicate the reason for the power loss.