FTW02FA048

The twin-turbojet, transport-category airplane was destroyed when it departed controlled flight during descent into its final destination and impacted terrain. The flight was cleared to descend from FL 390 to 10,000 feet, and the flight crew established a 4,000-foot/minute descent. As the airplane descended through FL 219, air traffic control requested the pilot contact approach control. However, the pilot read back an incorrect frequency and spoke an unintelligible word. The controller attempted to correct the pilot; however, no additional communications were received from the flight crew. Located within a pause in the pilot's last transmission, a 1680 Hz frequency could be heard for 0.1 seconds. There are only two systems in the airplane with aural warning systems within that frequency range; the cabin altitude warning, and the overspeed warning (both systems were destroyed during the accident sequence). Shortly after the last transmission from the pilot, radar data depicted the airplane climbing back up to FL 231 before entering a steep and rapid descent. A performance study indicated that just prior to the loss of control, the airplane exceeded its maximum operating airspeed of 300 knots calibrated. However, according to the manufacturer, the airplane had been successfully flown at airspeeds up to 400 knots calibrated without loss of control. The right wing and sections of the right horizontal stabilizer/elevator separated from the airplane just prior to its impact with terrain and were located approximately 200-250 feet from the main impact crater. No anomalies with the airframe or engine were found that would have led to the loss of control. A cockpit voice recorder was installed in the accident airplane; however, it did not record the accident flight.

History of flight

On December 10, 2001, at 1821 mountain standard time, a Gates Learjet 24D transport category, twin turbojet airplane, N997TD, operating as Turbodog 36, was destroyed when it impacted terrain following an uncontrolled descent near Sierra Blanca, Texas. The airplane was registered to and operated by Air Cargo Express Inc., of Fort Wayne, Indiana. The airline transport rated captain and the commercial rated co-pilot sustained fatal injuries. Night visual meteorological conditions prevailed, and an instrument flight rules (IFR) flight plan was filed for the 14 Code of Federal Regulations Part 91 positioning flight. The flight originated from the Harlingen Valley International Airport, Harlingen, Texas, at 1700, and was destined for the El Paso International Airport, El Paso, Texas.

It should be noted that unless otherwise indicated, all times are in mountain standard time (MST). According to radar and communication data obtained from the Albuquerque Air Route Traffic Control Center (ZAB ARTCC), they provided air traffic control service during the descent portion of the flight from a point approximately 115 miles southeast of ELP. At 1809:26, ZAB cleared the pilot to descend "at pilot's discretion" from Flight Level (FL) 390 to 10,000 feet. The pilot acknowledged, stating "we'll take it nice and slow." At 1814:42, ZAB instructed the pilot to turn left ten degrees for separation from ELP departing traffic. The pilot acknowledged. At 1817:28, ZAB asked the pilot to "increase rate of descent if you can." The pilot replied that they would increase the descent by 1,000 feet/minute and asked at what altitude he could expect to turn back direct to ELP. The controller replied "about 25 [thousand]." The pilot replied that "would be no problem, we're coming down about 4,000 feet/minute."

At 1819:10, ZAB cleared the flight direct to ELP, and the pilot acknowledged. At that point, radar data depicted the flight descending through FL266. At 1821:06, ZAB instructed the pilot to contact ELP approach control (the flight's mode C transponder depicted the airplane at FL219). The pilot acknowledged with an incorrect frequency and uttered an unintelligible sound. The controller attempted to correct the readback, but no response was received and the pilot never contacted ELP approach control. During this exchange the transponder's mode C function indicated the airplane climbed to FL225. The airplane continued to climb to FL231 and at 1821:20 no mode C was received from the airplane.

The final radar contact was 37 nautical miles from the El Paso very high frequency omnidirectional range (VOR) navigational facility along the 103-degree radial. The flight crew did not contact ELP TRACON, and no distress calls were received.

A search for the airplane was initiated and, at 2000, local authorities located the accident site on a private ranch.

Personnel information

The captain held an airline transport certificate with type ratings in the Douglas DC-3 and Learjets (both the 23/24 models and the 35 model). He also held a commercial certificate for single-engine airplanes with type ratings for the Lockheed B-34 and the Douglas B-26 (the latter two aircraft are considered vintage airplanes and the pilot was only permitted to fly them in visual flight conditions). According to records provided by Air Cargo Express Inc., the captain was hired on November 3, 2000. At the time the captain was hired, he had accumulated a total of approximately 20,000 hours, of which 10,000 were in multi-engine aircraft, 10,000 hours were in jet-type aircraft. The pilot reported accumulating 10,000 hours during night conditions. On June 8, 2001, the captain underwent his most recent FAR Part 135 airman competency/proficiency. At the time of the accident he had accumulated approximately 20,650 hours. Additionally, he held a first class medical certificate that was issued September 11, 2001. The medical certificate contained the following limitation: "Holder shall wear corrective lenses while exercising the privileges of his/her airman certificate."

According to Air Cargo Express' flight and duty log, the captain did not work on the 8th and 9th of December. Prior to that, the captain logged 8.0 hours of duty time, of which 6.4 hours were flight time on December 7, 2001. On December 6, 2001, the pilot logged 7.3 hours of duty time, of which 6.2 hours were consumed while flying.

On August 1, 2000, the co-pilot was issued a commercial pilot certificate. He held single-engine land, multi-engine land, and instrument airplane ratings. According to records provided by Air Cargo Express Inc., the co-pilot underwent initial second-in-command ground training on June 24, 2001. As of July 11, 2001, he had accumulated a total of 1,400 hours, of which 150 hours were in multi-engine aircraft, 20 hours were in jet-type aircraft, and 100 hours were during night conditions. On July 11, 2001, he underwent his most recent FAR Part 135 airman competency/proficiency check. At the time of the accident he had accumulated approximately 1,715 hours, of which approximately 315 hours were in the Lear 24. Additionally, he was issued a second-class medical certificate on June 26, 2001. The medical certificate contained the following limitation: "Must wear corrective lenses."

According to Air Cargo Express' flight and duty log, the co-pilot did not work during the four days preceding the accident.

Aircraft information

The 1972-model airplane (serial number 247) was powered by two General Electric CJ610-6 turbojet engines (left engine serial number 251-657A, and right engine serial number 251-299A), which were rated at 2,950 pounds of thrust each. Photographs of the airplane taken prior to the accident revealed it was painted navy blue on the bottom 1/3rd of the airplane, encompassing the belly and wings. Three painted stripes; one navy blue, one gold, and another navy blue, topped the solid blue belly paint and were separated by white paint. The remaining top 2/3rds of the airplane was painted white, with the exception of the registration number and company logo. The wing tip tanks displayed a similar paint scheme as the fuselage, but to a smaller scale.

The Learjet 24D's elevator and ailerons are operated mechanically through a system of cables, pulleys, push-pull tubes, and bellcranks. The rudder is operated through a system of cables, pulleys, and bellcranks. The aileron, rudder, and stabilizer trim systems are electrically driven. The flaps are operated utilizing a system of hydraulic pressure, actuating cylinders at each flap, and interconnecting cable that synchronizes the flaps through their range of travel. The spoilers are operated utilizing a system of hydraulic pressure and actuators at each spoiler panel.

The airplane was established on an FAA approved airworthiness inspection program (AAIP). At the time of the accident, the airplane had accumulated approximately 7,970 total flight hours. According to the maintenance records, on December 7, 2001, at an aircraft total time of 7,966.4 hours, the aircraft had its emergency gyro battery deep-cycled, and its left engine replaced. The installed left engine serial number was 251-657A and had a total time of 6,968.0 hours, and a total time since overhaul of 3,954.7 hours. On October 31, 2001, at an airplane total time of 7,860.1 hours, an overhauled yaw servo unit was installed. On October 30, 2001, at an aircraft total time of 7,857.9 hours, maintenance personnel complied with the 2,400-hour replacement of the primary control cables, and conducted a detailed inspection of the flap system.

The airplane underwent its last AAIP inspection on September 10, 2001, at an aircraft total time of 7,763.7 hours, when a 300-hour Phase A1-A6 inspection was completed on both the airframe and the engine. During that inspection the #1 navigational transmitter and captain's direc