C-GGBT

HISTORY OF FLIGHT

On December 20, 2008, at 1951 mountain standard time, a twin-engine Hawker Beechcraft 58P airplane, 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 two part cross-country flight had originated earlier that day from the Great Falls International Airport (GTF), Great Falls, Montana, and had concluded at the Pueblo Memorial Airport (PUB), Pueblo, Colorado, for a planned fuel stop. The second leg of the flight originated from PUB at 1915 with the Santa Fe Municipal Airport (SAF), Santa Fe, New Mexico, as the intended destination.

A review of radar information revealed that following departure the airplane climbed to and leveled off at 18,000 feet mean sea level (MSL). (All altitudes listed in this report are MSL unless otherwise noted) Approximately 32 minutes later the airplane was flying on a heading of 207 degrees and was approaching a ridge of mountains that ran in a north south direction. When the airplane was about four and a half miles east of the ridgeline, it began an uncontrolled descent toward an area of rising mountainous terrain. During the last radio transmissions from the pilot, he reported having serious difficulties; however, he was unsure what the problem was. The last known radar position placed the airplane at 12,800 feet and one mile east of Vermejo Peak with a summit of 13,367 feet. A short time later a ground fire was reported by a passing airplane in the vicinity of the accident airplane’s last known coordinates.

The pilot from the passing airplane submitted a written statement about what he observed while circling over the accident airplane. The pilot was flying a pressurized Cessna 210, equipped with an Allison 250 turbo-propeller engine that was capable of producing 450 horse power (HP). While approaching the accident area at 19,000 feet the Cessna pilot spotted a ground fire that he believed was the accident airplane. While circling the wreckage, he realized that his airplane was descending and added engine power thinking it was poor piloting technique. After reporting the fire to air traffic control (ATC), he noticed that his airplane’s attitude was now down to 18,500 feet and the engine was already at full power. The Cessna pilot informed ATC that he was in an area of downdraft and they cleared him for a block altitude of 17,000 to 19,000 feet. During this time his airplane continued an uncontrolled descent at 500 feet per minute (fpm), and the Cessna pilot estimated that the airplane should have been climbing at 1,000 fpm. The Cessna pilot elected to leave the area to the south and the rate of descent began to slow until he was able to maintain altitude. The Cessna pilot 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 was able to approach the accident site and confirm that the occupants had been fatally injured before operations were suspended due to deteriorating weather conditions. Because of snow, search and rescue personnel were unable to recover the bodies of the pilot and passenger 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 of “Glasses Must Be Worn.”

The pilot’s logbook was not recovered during the course of the investigation. An insurance application submitted on February 4, 2008, listed the pilot’s total flight time as 1,634 hours, with 84 flight hours in the previous 12 months, and 21 flight hours in the preceding 90 days. The pilot’s flight hours in this make and model of airplane are unknown; however, the insurance application listed a total of 400 hours in a Beech 95-A55. The date of his last flight review is unknown.

AIRCRAFT INFORMATION

The 1981-model Hawker Beechcraft 58P, serial number TJ-373, was a pressurized, low wing, twin engine airplane, equipped with a retractable landing gear, and was configured for six occupants. The airplane was powered by two, Teledyne Continental Motors (TCM), direct drive, horizontally opposed, fuel injected, air-cooled, turbo-charged, six-cylinder engines. The engines were TSIO-520s, serial numbers 237278-R and 518129, rated at 325 horsepower at 2,700 rpm, and were driving three-bladed constant speed McCauley propellers.

The airplane’s airframe and engine logbooks were not recovered during the course of the investigation; however, partial copies of records were received. According to these records the airplane's most recent annual inspection was completed on June 27, 2008, with an airframe total time of 3,571 hours. At the time of annual inspection the left engine had accumulated an estimated 98 hours since a major overhaul on September 5, 2006, and the right engine had accumulated approximately 473 hours since a major overhaul on July 5, 2007. The McCauley propellers had been installed new on July 5, 2007.

Fuel receipts revealed that the airplane was last fueled on December 20, 2008, at PUB with 109.30 gallons of 100LL aviation fuel.

METEOROLOGICAL INFORMATION

A review of meteorological conditions for Colorado revealed that at 2100 a stationary front stretched from Wyoming to northeastern New Mexico near, but to the east of the Continental Divide. Most stations in the eastern-half of Colorado reported clear skies with light and variable winds at the surface.

At 1952, the automated weather observing system at the San Luis Valley Regional Airport/Bergman Field (ALS), Alamosa, Colorado, located 45 nautical miles northwest from the site of the accident, reported wind from 80 degrees at 6 knots, 10 statute miles visibility, clear of clouds, temperature 16 degrees Fahrenheit, dew point 7 degrees Fahrenheit, and a barometric pressure setting of 30.04 inches of Mercury.

To assess the potential for mountain wave activity and retrieve quantitative data concerning the severity of any mountain waves present, the RAwinsonde OBservation Program (RAOB) was utilized.

Three separate vertical profiles of wind and temperature were acquired: 1) a RAwinsonde weather balloon launch at 1700, from the Albuquerque International Sunport Airport (ABQ), Albuquerque, New Mexico, located 141 nautical miles south-southwest of the accident site, 2) a North American Mesoscale (NAM) model atmosphere for the accident location initialized at 2000, and 3) an atmosphere measured by an aircraft departing the Denver International Airport (DEN), Denver, Colorado, in a southward direction about 2019.

With the ABQ RAwinsonde launch, severe wave activity was found to occur about 16,200 feet, with theoretical downdrafts estimated to be in excess of 4,500 fpm. Additionally, moderate/severe wave activity was found to exist at altitudes greater than 40,000 feet.

When considering the NAM model atmosphere, light wave activity was found to occur about 16,600 feet, with theoretical downdrafts estimated to be approximately 550 fpm. Severe wave activity was found to be centered about 23,000 feet.

The aircraft-measure atmosphere from the DEN departing aircraft revealed light wave activity at altitudes of 16,000 feet and 18,000 feet, with theoretical downdrafts of approximately 300 fpm each. Severe wave activity was found to occur at 22,000 feet, with moderate/severe wave activity at 36,000 feet.

There were numerous pilot reports (PIREPs) of turbulence over the state of Colorado on December 20, 2008. Many of these reports specifically identified encounters with mountain waves and/or severe or extreme turbulence at flight levels close to the upset location for the accident airplane.

COMMUNICATIONS

According to a transcript of air traffic control communications, the accident flight was cleared for takeoff from PUB at 1915. At 1931:05, the accident pilot contacted the Denver air route traffic control center sector 27 radar controller (referred to as “Denver Center”) and reported that the flight was level at its assigned altitude of flight level 180 (18,000 feet pressure altitude), and the controller acknowledged.

At 1947:37, the Denver Center controller asked the pilot to verify the flight’s altitude, and the pilot replied, “uh … we’ve having some problems here sir we’re just trying to rectify it we’re going back up from seventeen to eighteen.” At 1947:48, the controller acknowledged and stated “…when you’re able maintain flight level one eight zero just be advised where you’re at minimum IFR altitude [is] one six thousand if you think you need something different uh let me know.”

At 1948:08, the pilot requested an altitude of 16,000 feet, stated to the controller that he “[didn’t] know what the problem is,” and asked the controller, “what kind of a ground speed readout do you have on us?” The controller then cleared the flight to maintain 16,000 feet, provided the local altimeter information, and advised the pilot that his display showed the airplane with a ground speed of 135 knots. The pilot asked the controller to repeat the ground speed information and then replied to the controller, “one three five knots thank you.”

At 1949:26, the pilot stated, “uh golf bravo tango sir we’re having some serious difficulties here.” The controller responded, “… roger maintain your highest possible altitude a vector away from terrain would be to the right but that would be into the wind what would you like to do sir?” At 1949:43, the pilot replied, “uh.” No...