History of Flight
On October 2, 2009, about 1240 Pacific daylight time, N1621C, a Cessna 180, lost engine power during flight. The pilot performed a forced landing in rugged terrain near Mitchell, Oregon. The private pilot was operating under Part 91. The pilot sustained minor injuries, one passenger sustained serious injuries, and one passenger was not injured. The airplane was substantially damaged. Visual meteorological conditions prevailed, and the pilot had requested and received flight following. The pilot departed about 1030 from Pistol Creek airstrip, a private airstrip in the Idaho backcountry, destined for Roberts Field Airport, Redmond, Oregon.
An Oregon State Trooper, also a private pilot, responded and interviewed the pilot, who reported that the engine lost power and he force-landed. The trooper noted throttle, mixture, and propeller controls in full forward; flap lever at 0 degrees; fuel selector at "Both"; magneto switch off. Left wing extensively damaged; right wing vertical against a tree. No fuel or fuel odor observed. Witnesses reported hearing a popping noise, seeing the airplane overhead with no power, disappearing behind trees before impact.
Pilot Statements
The pilot submitted multiple statements. In the first statement (October 15), he reported that prior to departure from Redmond, he requested fuel tanks filled to within 1/2-inch of necks, noting 23 gallons pumped. He flew to Pistol Creek using carburetor heat for about 40% of flight. He estimated 10 gallons per hour fuel burn. His calculations showed 58.2 gallons total, 22.5 used, 35.7 remaining after 2.25 hours. At Pistol Creek, he checked for fuel leaks; none found. On departure, he circled a hunting area, then flew direct to Redmond. Carburetor heat usage similar. He used fuel burn rates of 10 gph elapsed and 12.5 gph tachometer. At 4 hours 20 minutes since refueling, his calculations showed slightly under 15 gallons remaining (elapsed) or 8.2 gallons (tachometer). Reserve estimated 5.2 to 11.5 gallons. Both fuel gauges read about 1/8. He entered descent; about 5 minutes later, engine lost power to idle, unresponsive to throttle. He switched fuel selector from left to both (no change), then to right (engine sputtered, then idle), then back to both. He pitched for best glide, saw two clearings, attempted landing but impacted trees near the end. He secured airplane, no fuel seen or smelled. Used SPOT beacon, then climbed hill to call for help. Search airplane located site about 1 hour later.
In an FAA interview (October 16), the pilot stated that upon passing John Day Airport, engine ceased while on left tank. He immediately moved to right tank; engine sputtered but did not continue. He then moved to both. He indicated fuel capacity was 58 gallons due to an STC. He produced STC paperwork. FAA asked about unusable fuel; pilot stated previous owner said all 58 gallons usable. FAA noted actual usable fuel was 51.4 gallons and showed the fuel selector decal placarded with 51.4 gallons. Pilot reported making trip 8-9 times prior; this was first time not refueling in Idaho.
In a letter (October 28), pilot reported contacting previous owner, who burned fuel from one tank after STC installation and determined all fuel usable. Previous owner also unaware of placard. Pilot stated he found no info on usable fuel other than installation instructions referencing Cessna 182; airplane flight manual did not contain STC supplement.
In a November 16 statement, pilot maintained fuel tanks held 56.4 gallons total usable; he and previous owner operated successfully since 1990 using those capacities. He noted fuel may have been less due to fueling errors, tampering, or loss at accident site. He stated he was "positive the prop continued to spin at least until collision...We clearly did not experience the silence of a stopped engine/prop."
Previous Owner Statement
The previous owner stated that after STC installation, he planned on 55 gallons usable fuel, typically 12.5 gph burn, sometimes 13 gph if not leaned. He would not fly longer than 4 hours. He recalled one time putting just over 50 gallons and thought he "cut it too close." He also drained left wing tank by burning fuel over an airport; after refueling, it appeared he burned the entire 28.2 gallons. He could not recall an airplane flight manual supplement for the fuel tank STC; he indicated all paperwork was provided to the new owner.
Airplane History
The four-seat, single-engine airplane (serial 30321) was manufactured in 1953 with 30-gallon bladder fuel tanks per wing. In 1990, 28.2-gallon standard fuel tanks were installed per STC SA 2346CE. FAA Form 337 noted that the airplane flight manual was updated with supplements 1, 2, and 3. The STC allowed standard range 56 or 62-gallon or long range 77-gallon tanks. Installation instructions recovered from maintenance records noted that existing placard data should be removed and a placard "Capacity 28.2 Gal." installed. Usable fuel quantities should be corrected on the fuel selector placard by subtracting unusable fuel from 56.4 gallons. According to the TCDS, unusable fuel quantity is 5 gallons.
Tests and Research
Examination of the airframe showed fuel placards indicating 28.2 gallons capacity per wing, and fuel selector placard showing 51.4 gallons usable (both) and 25.7 gallons per tank. Right fuel cap intact and secured; left cap upper portion separated from lower, but lower portion could be secured. No fuel staining on wings or fuselage. Fuel selector removed and examined; left wing fuel screen free from obstruction; right wing fuel screen not located. Approximately 1 ounce of fuel collected from left tank line to selector; color and smell consistent with 100LL. Left fuel tank breached; right tank intact. Both tanks had Monarch label dated November 13, 1990. Firewall fuel strainer unobstructed but contained no fuel; drain valve closed but free.
The engine (Teledyne Continental Motors O-470-J, serial 41500) was examined. Several impact damage areas noted, including crushing on forward left side and cylinder 1. Upper spark plugs removed and considered worn out-normal per Champion chart. Cylinders borescoped with residual oil and white combustion deposits. Thumb compression obtained on all six cylinders; valves produced similar lift. Mechanical gear continuity from propeller to starter drive, propeller governor drive gear, and accessory case. Carburetor disassembled; no fuel in bowl; floats intact; screen clean. Propeller governor manually rotated; screen clean. Vacuum pump drive coupler intact. No fuel evident at engine. Oberg oil filter contained oil; screen unobstructed.
The McCauley propeller had both blades secured in hub. Blade 1 had aft bending near tip and scuffing along leading edge. Blade 2 had chordwise scratch marks on trailing edge.
Examination of recovered airframe and engine components revealed no evidence of preimpact mechanical malfunction.