NTSB Identification: DEN01FA044.
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Accident occurred Wednesday, January 24, 2001 in Watkins, CO
Probable Cause Approval Date: 07/15/2002
Aircraft: Aero Vodochody Aero. Works L-39CT, registration: N602MC
Injuries: 2 Fatal.
NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.
The pilot departed from runway 26 in the military jet trainer and made an immediate steep left hand turn at an estimated 100 to 300 feet above the ground. Approximately 30 seconds later, the back seat canopy transparency failed and separated from the aircraft. The back seat passenger's headset and hat accompanied the transparency fragments to the ground. The airplane began oscillating divergently, pitching up to near vertical, turned right, and impacted the ground longitudinally oriented approximately 60 degrees to the right of the energy track alignment. The airplane's most recent empty weight CG calculations indicate that the airplane was at 34.98% MAC; the factory recommends a 27.7% MAC empty weight CG. The airplane's flight CG (with two occupants and the main fuel tank full) was calculated to be 29.58% MAC. The manufacturer recommends an approximate flight CG of 23 to 25.5% MAC. As the CG moves aft of this envelope, aircraft control becomes progressively more sensitive. The manufacturer reported that their test pilot's have flown the airplane with CGs as high 34% to 35% MAC, and aircraft records indicate that the pilot had previous flight experience with CGs in the 29% to 30% MAC range. Aircraft records also indicate that the pilot had 38.6 hours of flight experience in the airplane in approximately 3 years, and 6.6 hours of experience during the last 18 months. The night before the accident, the pilot had returned from a trip around the world in his Boeing Business Jet, with multiple business stops along the way. Analysis of the rear canopy's transparency indicated that it was embrittled.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: The pilot's failure to maintain aircraft control, and the subsequent inadvertent stall/mush. Factors were the pilot's diverted attention due to the failure of the rear canopy's acrylic transparency and the loss of communication with his back seat passenger, the pilot's lack of recent experience in make/model airplane, the airplane's improper aft weight distribution (center of gravity), and the pilot's fatigue (circadian rhythm).
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