Flight History
On February 6, 2010, at 1327 mountain standard time, a Cirrus SR20, registration N825BC, and a Piper PA-25-235, registration N8718L, collided in flight near Boulder, Colorado. At the time, the Piper was conducting glider tow operations with a Schweizer SGS 2-32 glider, registration N2472W. The Cirrus and Piper were substantially damaged; the glider was not damaged. The Cirrus was privately owned and piloted. Mile High Gliding, Inc., operated both the Piper and the Schweizer. Visual meteorological conditions prevailed. All flights were conducted under 14 CFR Part 91 without flight plans.
The Cirrus pilot and passenger, and the commercial pilot aboard the Piper, were fatally injured. The commercial pilot and two passengers aboard the Schweizer were not injured.
The Cirrus had departed Erie Municipal Airport (KEIK), Erie, Colorado, at about 1245 for a local flight. The Piper and Schweizer departed Boulder Municipal Airport (KBDU) at about 1320 for a glider tow flight, which was intended as a scenic flight for a birthday party. The tow flight departed runway 8, performed a 360-degree turn for altitude east of the airport, and then continued west/northwest.
Glider Pilot Statement
The Schweizer pilot reported that at 8,000 feet, with the tow rope tight and climbing at 70 mph in smooth air, he observed a Cirrus off the right side of his glider, less than 500 feet away. Concerned that the Cirrus would fly between the tow plane and glider, he reached for the towline release. At that moment, the Cirrus impacted the forward right side of the tow plane at nearly a 90-degree angle. The glider flew through a ball of fire and returned to KBDU. Neither the Schweizer pilot nor one passenger observed any maneuvering by the Cirrus or Piper prior to impact. The Schweizer pilot noted no control movements or turbulence from the tow plane before impact.
Witness Observations
Multiple witnesses heard the collision and observed the post-collision state. The Cirrus descended under its Cirrus Airframe Parachute System (CAPS) while on fire. Debris from both airplanes was scattered over a 1.5-mile area, with Piper components at the northern end and the Cirrus main wreckage at the southern end.
Radar Data
Radar data from Denver Air Route Traffic Control Center (ZDV) showed the Cirrus track from departure at KEIK. Its encoded altitude ranged from 6,800 to 8,800 feet msl. The flight track went north, maneuvered, reversed course south, and just before impact was tracking about 180 degrees. The Piper track showed intermittent altitude data: 5,500 feet at 1320:58 and 6,500 feet at 1322:57. The Piper performed one turn near KBDU and was tracking about 270 degrees just before impact. Within the last minute, the Cirrus was at 8,400 and 8,300 feet. The glider pilot estimated the accident altitude at 8,000 feet. Neither pilot was receiving radar flight following or in voice communication with air traffic control; neither was required.
Personnel Information
The Cirrus pilot, aged 58, held a private pilot certificate with single-engine land rating and a third-class medical certificate dated December 4, 2008, with a limitation requiring corrective lenses. His flight logbook showed at least 640 hours total time, with 359 hours in the accident airplane make and model. He completed a flight review on May 15, 2009.
The Piper pilot, aged 25, held a commercial pilot certificate with single- and multi-engine land and instrument ratings, and a flight instructor certificate. He held a first-class medical certificate dated February 12, 2009, with no limitations. Mile High Gliding reported he had 1,110 hours total time, with 260 hours in the accident airplane make and model, and completed a flight review on October 24, 2009.
The Schweizer pilot, aged 39, held a commercial pilot certificate with glider, single-engine land, and instrument ratings, and a flight instructor certificate. He held a third-class medical certificate dated March 15, 2006, with no limitations. He had 2,044 hours total time, with 3 hours in the glider make and model, and completed a flight review on June 7, 2009.
Aircraft Information
The Cirrus SR20 (serial number 20-1655) was a low-wing airplane manufactured in May 2006, with a standard airworthiness certificate. It was powered by a Teledyne Continental Motors IO-360-ES(6) engine rated at 210 hp, equipped with a three-blade Hartzell propeller. It was maintained under an annual inspection program. A traffic collision avoidance system was not installed. The Cirrus had navigation and anti-collision strobe lights.
The Piper PA-25-235 (serial number 25-5173) was a low-wing airplane manufactured in 1969, with a special airworthiness certificate in the restricted category for glider towing. It was powered by a Lycoming O-540-B2C5 engine rated at 235 hp, equipped with a four-blade Hoffman propeller. It was maintained under an annual inspection program. The Piper was not equipped with position or anti-collision lights; nor was it required.
The Schweizer SGS 2-32 (serial number 47) was a glider manufactured in 1967, with a standard airworthiness certificate. It was maintained under a 100-hour inspection program. It was not equipped with a transponder or position/anti-collision lights, as not required.
Meteorological Information
The closest weather observation station, Rocky Mountain Metropolitan Airport (KBJC), 14 nm southeast, reported at 1247: winds calm, visibility 8 miles, scattered clouds at 8,000 feet, overcast at 12,000 feet, temperature 4°C, dew point -6°C, altimeter 29.89 inches. At 1353: winds calm, visibility 10 miles, few clouds at 9,000 feet, overcast at 12,000 feet, temperature 5°C, dew point -7°C, altimeter 29.86 inches.
Aerodrome Information
Boulder Municipal Airport (KBDU) was a public, uncontrolled airport (Class G) 3 miles northeast of Boulder at an estimated elevation of 5,288 feet. Class E airspace was located east and north, and Class D airspace for KBJC to the south. KBDU is within the Mode C 30 nm veil. The airport website provided a depiction of glider and tow plane traffic patterns. Sectional charts and the Denver VFR Terminal Area Chart depicted glider activity with a "G" symbol near KBDU. The Airport Facility Directory stated runway 08-26 G was for glider use only and that powered aircraft on approach should yield right of way to gliders on final; it did not discuss glider tow operations.
Wreckage and Impact Information
Debris from both airplanes was scattered over 1.5 miles at a field elevation of about 5,500 feet msl over rolling hills and rocky terrain.
The Cirrus main wreckage consisted of the fuselage, empennage, and both wing assemblies, oriented on a heading of 250 degrees on a 10-degree slope. The engine separated 25 feet north. The CAPS remained attached. The forward fuselage and cabin were charred and partially consumed by fire. The empennage remained attached with heat and fire damage. Flight control cables were continuous. The right wing was partially attached; the left wing outboard portion separated. The engine assembly and propeller separated. It could not be determined if anti-collision lights were on.
The Piper's largest identifiable components were the engine/propeller assembly, left wing, empennage, and two fuselage segments. The right wing and other parts were fragmented. The fuselage was crushed from right to left. The right wing leading edge had blue paint transfer (46 inches by 10 inches) and grey paint transfer on the right wing strut. The left wing separated; the strut was bent. The empennage separated. Flight control cables were continuous where traceable. The engine and four-blade propeller assembly separated; blades showed scoring, breaking, and heat damage.
Medical and Pathological Information
Autopsies performed by the Boulder County Coroner’s Office on both pilots concluded the cause of death was multiple traumatic injuries sustained in a mid-air airplane collision and subsequent ground impact. Toxicological tests by the FAA’s Civil Aerospace Medical Institute were negative for all tested substances.
Tests and Research
Examination of the Piper revealed the fuselage crushed from right to left. The throttle quadrant was full forward. The right wing had blue paint transfer on the inboard leading edge. The left wing strut had two bends. The engine and propeller exhibited impact and heat damage.
Additional Information
Radar data showed the Cirrus at 1246:54 near KEIK, tracking north, then south toward Boulder. The Piper first appeared at 1320:58 north of KBDU. The distance between the aircraft reduced over time, with the Cirrus 0.76 miles south southeast of the Piper at 1326:58. The Cirrus broadcast a continuous 1200 transponder code.
Cockpit visibility from the Cirrus left seat was evaluated using an exemplar. Forward visibility (12 o’clock) was unrestricted in all seat positions. Side visibility (9 o’clock) was unrestricted.