History of Flight
On September 19, 2013, about 1553 mountain daylight time, a Beech C90-A twin-turboprop airplane, N191TP, was substantially damaged when it impacted a field short of runway 20 at Idaho Falls Regional Airport (IDA), Idaho Falls, Idaho, during its final approach. The commercial pilot and one passenger received minor injuries, and one passenger received serious injuries. The airplane was owned and operated by WE FLY LLC of Idaho Falls. The business flight was conducted under Title 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed, and no flight plan was filed.
According to the pilot, the airplane was based at IDA. The day's flight sequence originated at IDA, with flights to Pocatello Regional Airport (PIH) and Boise Air Terminal/Gowen Field (BOI). After a meeting, the pilot and same passengers departed BOI for IDA, with an interim stop at PIH. The leg from PIH to IDA was described as "bumpy" or "turbulent."
During final approach to runway 2, a master warning or caution annunciator light illuminated, which the pilot believed was related to a fuel quantity or distribution issue. He checked the fuel gauges and recalled they indicated fuel remained. He then saw the ground coming up fast and told passengers to hold on.
Personnel Information
FAA records indicated the pilot held a commercial pilot certificate with airplane single- and multi-engine land ratings and an instrument rating. He had about 3,975 total flight hours, including about 2,500 hours in the accident airplane make and model. His most recent flight review and FAA first-class medical certificate were issued in June 2013.
Aircraft Information
The airplane was manufactured in 1989 and equipped with two Pratt & Whitney Canada PT6A turboshaft engines. It had one wing (main) fuel tank and one nacelle tank per side. Usable fuel capacity was 132 gallons per main tank and 60 gallons per nacelle tank, totaling 384 gallons. In normal operation, fuel is supplied from each nacelle tank, with automatic transfer from main tanks via electrically-powered boost pumps. A "NO FUEL XFR" annunciator light indicates when transfer pressure drops, meaning a main tank is empty.
Two fuel quantity gauges displayed either nacelle tank quantity or total fuel per side, selectable by a switch. The operating manual prohibited takeoff if fuel gauges indicated in the yellow arc or less than 265 pounds (about 39.5 gallons) per side.
Meteorological Information
The IDA 1553 automated weather observation reported wind from 210 degrees at 3 knots, visibility 10 miles, clear skies, temperature 17°C, dew point 0°C, and altimeter 30.19 inches of mercury.
Wreckage and Impact Information
The airplane impacted a level plowed field about 1.2 miles short of runway 2, struck an irrigation ditch and berm nearly perpendicular to travel, and came to rest about 60 feet beyond the ditch. Initial ground scars were about 150 feet prior to final rest. The airplane remained upright; landing gear and left propeller separated, right engine partially separated from the wing, and the aft fuselage was buckled and torn. Landing gear damage indicated it was extended at impact.
One nacelle tank was breached; the other three tanks were intact with securely installed filler caps. No fuel was observed in either main tank, and both nacelle tanks were empty. About half a gallon of fuel was recovered; no significant leakage from the breached tank was noted. No pre- or post-impact fire occurred.
Additional Information
Before departing IDA, the pilot determined the nacelle tanks were full (via gauges) and had 30 gallons added to each main tank. After landing at BOI, he again determined nacelle tanks were full (via gauges) and main tanks not empty (since no "NO FUEL XFR" light had illuminated). He then had 40 gallons added to each main tank. The pilot did not report specific fuel quantities in main tanks after refueling, stating only that the wing tanks had about 30 minutes of fuel before the first upload, without providing a basis.
The pilot reported the airplane's fuel consumption averages 70 gallons per hour. He did not provide fuel quantity for the takeoff from PIH on the return leg.
The airplane manufacturer estimated fuel consumption for the routes: IDA-PIH about 28.5 gallons, PIH-BOI about 68.5 gallons, total round trip 194 gallons. With a 30-minute reserve (about 46 gallons), total required fuel would be 240 gallons. Cruise fuel consumption was between 92 and 102 gallons per hour below 12,000 feet.
Derived calculations based on pilot statements indicated about 295 gallons were available for the round trip, exceeding the manufacturer's estimated required quantity. A conservative estimate for the return trip, assuming near-empty main tanks, full nacelle tanks, and 80 gallons uploaded, yielded a minimum of 200 gallons.
Communications
The airport's air traffic control tower was staffed. The pilot contacted IDA when about 18 miles southwest, advising inbound VFR. The controller queried runway preference; the pilot preferred runway 2. The controller cleared the pilot for a straight-in approach to runway 2, confirming twice. When the airplane was on about a 2-mile final, the controller advised to check landing gear extension. The pilot did not acknowledge. The controller then observed the airplane yaw right and descend to the ground more than a mile short of the runway, and alerted crash fire rescue.