Accident Narrative
On May 2, 2013, at 1127 mountain daylight time, a Cessna 182T, registration N2012Y, experienced a loss of propeller control during cruise flight. The pilot executed a forced landing on a highway after the airplane lost the ability to maintain altitude. During the forced landing near Delta, Colorado, the airplane impacted power lines and terrain, resulting in substantial damage to the fuselage. The private pilot was uninjured. The airplane was registered to Janair LLC and operated by Colorado Flight Center under 14 CFR Part 91 as a personal flight. Visual meteorological conditions prevailed, and no flight plan was filed for the local flight, which originated from Grand Junction Regional Airport (GJT) at 1045 and was returning to GJT.
Pilot Report
The pilot stated that after performing touch-and-go landings at Montrose Regional Airport, he was returning to GJT. During the return, he reduced manifold pressure to 19 inches of mercury and began reducing propeller speed from 2400 rpm to 2250 rpm after leveling at 8000 feet mean sea level. While adjusting the propeller speed control knob, the propeller speed dropped abruptly to about 2100 rpm. Pushing the propeller control knob full in produced no change. He then advanced the throttle to full power; airspeed was about 110 knots indicated airspeed (KIAS) but decreasing. The pilot descended to 7500 feet, where airspeed stabilized at 85 KIAS with manifold pressure at 20.9 inches Hg. After a few miles, propeller speed became erratic, ranging between 2150 and 2040 rpm. Cycling the propeller control did not resolve the issue. Shortly after diverting to Blake Field Airport, Delta, Colorado, the pilot heard a heavy muffled clunking sound from the front of the airplane. The airplane lost all thrust, and the pilot performed a forced landing without flaps, aiming for a highway. He turned to avoid power lines but struck them during the turn. The airplane touched down on the highway and went off the right shoulder after the right main landing gear separated.
Aircraft and Maintenance History
The last annual inspection was on March 8, 2013, at a total airframe tachometer time of 1627.0 hours, with an entry stating the propeller governor was overhauled. On April 17, 2013, an overhauled propeller was installed: a McCauley 83D36C431-C/80VSA-1, serial number 051726, three-blade propeller with 1643.7 hours total time since new and 0 hours since overhaul.
On-Scene Examination
An FAA inspector found that the flaps were retracted, the fuel selector was off, cockpit mixture and throttle controls were at their forward stops, the propeller control was at the aft stop, and the fuel boost pump was off. Propeller control continuity was confirmed before removal of the propeller and governor.
Propeller and Governor Examination
The propeller and governor were removed and sent to McCauley Propeller Systems. On July 19, 2013, testing and examination were conducted under NTSB supervision. All three propeller blades could be rotated by hand within the hub and showed no bending or twisting. The number 1 blade had two leading-edge dings/gouges near the outboard quarter span; number 2 had a ding/tear near the tip; number 3 had a dent/gouge near quarter span. The blades were removed from the hub, and all three pitch change links were fractured, consistent with overstress. No other internal damage was noted. When the piston assembly was removed, a liquid consistent with water, along with oil, was present.
The governor, part number DC290 D1F/T8, serial number 051824, was missing four cap screws. The remaining two screws were finger tight. Oil drained from the governor did not contain water. After installing four cap screws, bench testing showed maximum governor speed of 2350 rpm (spec limit 2275 rpm) and relief valve pressure of 305 psi. Flow testing showed input oil pressure of 50 psi, output 124 psi, flow rate 5.9 quarts/minute (minimum 5.0, no maximum), and internal leakage rate 2 quarts/hour (maximum about 10 quarts/hour).
An NTSB question to the McCauley party coordinator in March 2014 referenced a teardown report stating that rain likely entered the propeller during storage in a truck bed with the mount flange uncovered. The representative noted that shimming was correct and blades rotated freely. Piston seal was undamaged; engine oil and propeller red oil were not intermixed. A pressure check was not performed because actuation links were broken. Pitch stop angle verification was not possible due to link breakage. Governor top cover had been removed, so control arm clocking could not be verified.
Engine Examination
The engine was overhauled after recovery. A pressure differential test across the front nose bearing per Lycoming Service Instruction 1462A showed 18 psi at delivery pressure of 35 psi (limit 6-35 psi). No obstruction was found in the front main bearing oil delivery. The fuel pump and fuel servo (Bendix RSA-5AD1) were tested and found within limits.
The overhaul facility mechanic described the oil system: engine oil travels down the left-hand case half to the propeller governor, which amplifies pressure and sends oil through a passage to the center of the front main bearing, then through a transfer tube in the crankshaft to the propeller hub, a closed system from governor to hub.