History of Flight
On December 20, 2008, at 1951 mountain standard time, a twin-engine Hawker Beechcraft 58P, registration C-GGBT, was destroyed when it impacted terrain following a loss of control near Stonewall, Colorado. The private pilot and the sole passenger sustained fatal injuries. The airplane was registered to and operated by Mauroil International Inc., of Calgary, Alberta, Canada. Night visual meteorological conditions prevailed, and an instrument flight rules (IFR) flight plan was filed for the 14 Code of Federal Regulations Part 91 personal flight. The first leg of the cross-country flight had originated earlier that day from the Great Falls International Airport, Great Falls, Montana, and concluded at Pueblo Memorial Airport (PUB), Pueblo, Colorado, for a planned fuel stop. The second leg departed PUB at 1915 with Santa Fe Municipal Airport, Santa Fe, New Mexico, as the intended destination.
Radar information revealed that after departure, the airplane climbed and leveled off at 18,000 feet mean sea level (MSL). Approximately 32 minutes later, the airplane was flying on a heading of 207 degrees and approaching a ridge of mountains oriented north-south. When the airplane was about four and a half miles east of the ridgeline, it began an uncontrolled descent toward rising mountainous terrain. During the last radio transmissions, the pilot reported having serious difficulties but was unsure of the problem. The last known radar position placed the airplane at 12,800 feet and one mile east of Vermejo Peak, which has a summit of 13,367 feet. Shortly after, a passing airplane reported a ground fire near the last coordinates.
The pilot of the passing airplane, flying a pressurized Cessna 210 equipped with an Allison 250 turbo-propeller engine, observed the ground fire while at 19,000 feet. While circling, he noticed his own airplane descending and added power. He informed air traffic control (ATC) of a downdraft, and ATC cleared him for a block altitude of 17,000 to 19,000 feet. His airplane continued an uncontrolled descent at 500 feet per minute, despite his estimate that it should have climbed at 1,000 fpm. He left the area to the south, and the descent slowed. He characterized the downdraft as an area of “mountain wave.”
The wreckage was located on December 21, 2008, at an elevation of approximately 12,077 feet. A helicopter crew confirmed that the occupants had been fatally injured before operations were suspended due to weather. Because of snow, search and rescue personnel could not recover the bodies until May 8, 2009.
Personnel Information
The pilot, age 67, held a Canadian-issued private pilot certificate with ratings for airplane single-engine land, multi-engine land, and instrument airplane. His last Transport Canada third-class medical was issued on November 26, 2007, with the limitation “Glasses Must Be Worn.” His logbook was not recovered. An insurance application dated February 4, 2008, listed his total flight time as 1,634 hours, with 84 hours in the previous 12 months and 21 hours in the preceding 90 days. His flight hours in the accident make and model were unknown, but the application noted 400 hours in a Beech 95-A55. The date of his last flight review was unknown.
Aircraft Information
The 1981-model Hawker Beechcraft 58P, serial number TJ-373, was a pressurized, low-wing, twin-engine airplane with retractable landing gear, configured for six occupants. It was powered by two Teledyne Continental Motors TSIO-520 engines, each rated at 325 horsepower, driving three-bladed constant-speed McCauley propellers. The airframe and engine logbooks were not recovered, but partial copies of records showed the most recent annual inspection was completed on June 27, 2008, with an airframe total time of 3,571 hours. At that time, the left engine had accumulated an estimated 98 hours since a major overhaul on September 5, 2006, and the right engine about 473 hours since a major overhaul on July 5, 2007. The propellers were installed new on July 5, 2007. Fuel receipts indicated the airplane was last fueled on December 20, 2008, at PUB with 109.30 gallons of 100LL aviation fuel.
Meteorological Information
At 2100, a stationary front stretched from Wyoming to northeastern New Mexico, near but east of the Continental Divide. Most stations in eastern Colorado reported clear skies with light and variable winds. At 1952, the automated weather observing system at San Luis Valley Regional Airport, Alamosa, Colorado, 45 nautical miles northwest of the accident site, reported wind from 80 degrees at 6 knots, 10 statute miles visibility, clear skies, temperature 16°F, dew point 7°F, and barometric pressure 30.04 inHg.
To assess mountain wave activity, three vertical profiles were analyzed: a rawinsonde balloon launch at 1700 from Albuquerque, New Mexico (141 nautical miles south-southwest of the site), a North American Mesoscale (NAM) model atmosphere for the accident location initialized at 2000, and an atmosphere measured by an aircraft departing Denver International Airport southward at about 2019. The Albuquerque rawinsonde indicated severe wave activity at about 16,200 feet with theoretical downdrafts exceeding 4,500 fpm, and moderate/severe activity above 40,000 feet. The NAM model showed light wave activity at about 16,600 feet with downdrafts of about 550 fpm, and severe activity centered at 23,000 feet. The aircraft-measured atmosphere revealed light wave activity at 16,000 and 18,000 feet with downdrafts of about 300 fpm each, severe activity at 22,000 feet, and moderate/severe activity at 36,000 feet. Numerous pilot reports of turbulence over Colorado on December 20 specifically mentioned mountain waves and severe or extreme turbulence at flight levels near the accident location.
Communications
According to ATC transcripts, the accident flight was cleared for takeoff from PUB at 1915. At 1931:05, the pilot contacted Denver Center and reported level at flight level 180 (18,000 feet). At 1947:37, the controller asked for altitude verification, and the pilot replied they were having problems and going back up from 17,000 to 18,000 feet. The controller advised that the minimum IFR altitude was 16,000 feet. At 1948:08, the pilot requested 16,000 feet, stated he didn't know the problem, and asked for ground speed, which was given as 135 knots. At 1949:26, the pilot said they were having serious difficulties. The controller suggested a right turn away from terrain, but no further communications were received from the pilot.
Wreckage and Impact Information
Due to snow, investigators could not reach the accident site until June 16, 2009. The wreckage was located on the north side of Vermejo Peak in steep granite scree at 12,077 feet, about 1,290 feet below the summit. The estimated impact heading was about 130 degrees; the attitude at impact could not be determined. Over the spring, wreckage had moved and pieces slid downhill. After recovery, components were examined at Beegles Aircraft Service Inc. in Greeley, Colorado.
The fuselage was nearly consumed by the post-crash fire. A vacuum-driven artificial horizon showed rotational scoring, suggesting it was operational at impact. Both wings separated and exhibited thermal damage; parts of the right wing were consumed. Ailerons remained attached; left flap separated, portions of right flap attached. Flap actuator measurements corresponded to retracted position. Fuel selectors were in the ON position. The left main landing gear up-lock roller was engaged, indicating gear was retracted. The empennage (horizontal stabilizer, elevators, vertical stabilizer, rudder) remained attached and was downhill. Control cables stretched from fuselage to empennage. Elevator trim tab actuator indicated about 5 to 10 degrees tab up; rudder trim tab indicated 0 to 5 degrees right. Partial control continuity was established for ailerons and elevator; rudder continuity was established.
Both engines, exposed to elements for six months, exhibited rust and corrosion. Crankshafts could not be rotated due to accident damage. Borescope examination of cylinders showed combustion deposits, no scoring in visible ring travel area. Spark plugs showed normal operating signatures. Magnetos had impact/thermal damage and could not be tested. Fuel pumps could not be rotated; disassembly revealed intact vanes and couplings with no debris. Oil filters had no abnormal particles. Left vacuum pump rotor fractured from impact; right vacuum pump unremarkable. Turbochargers were intact with no cracks or exhaust leaks. Propellers separated from flange; all six blades had gouging, S-bending, cordwise scratches, and polishing, consistent with power at impact.
No anomalies were found with the engines or airframe that would have contributed to the loss of control.
Additional Information
A Canadian Civil Aviation Daily Occurrence Reporting System (CADORS) report dated December 18, 2008, stated that the accident airplane had departed Springbank Airport, Calgary, Alberta, on an IFR flight to Casper, Wyoming. About 40 miles southeast of Calgary, the pilot reported incorrect airspeed and altimeter issues and returned to Calgary safely. On December 23, another CADORS report noted that the pilot contracted an approved maintenance organization to troubleshoot the airspeed discrepancies. A pitot static system check and airspeed system test found no fault.
Investigators calculated expected two-engine climb rates for the prevailing conditions using the Beech Baron 58P Pilot’s Operating Handbook: 980 fpm at 18,300 feet, 1,150 fpm at 15,900 feet, and 1,260 fpm at 13,700 feet.