Boulder, CO, USA
N8718L
PIPER PA-25-235
N825BC
CIRRUS DESIGN CORP SR20
N2472W
SCHWEIZER SGS 2-32
While conducting glider-tow operations, the right wing of a Piper PA-25 was struck at a 90 degree angle by a Cirrus SR20. Analysis of the radar information, the flight condition of both airplanes, and the pilots' visibility in their respective cockpit configurations, suggests that until just prior to the impact, the Piper would have been located below the horizon and against the background of the surrounding terrain and city, between the 10 and 11 o’clock position of the Cirrus pilot. The Piper remained in this same relative position in the windscreen of the Cirrus pilot for the entire duration of its 7 minute flight. The Cirrus would have been above the horizon, against the white overcast sky, in about the 1 to 2 o’clock position of the Piper pilot. The Cirrus would have only appeared in this position after the Piper pilot completed the last turn and was headed to the west, which would have been (at most) the last 3 minutes of the flight. Visual meteorological conditions existed at the time of the accident with an overcast layer and visibility of 8 miles. The overcast sky conditions likely made it difficult for the Piper pilot to detect the primarily white-colored Cirrus. The lack of maneuvering, as observed by the glider pilot prior to the accident, suggests that neither the pilot of the Cirrus nor the pilot of the Piper observed the other airplane prior to the accident. If the Piper pilot had observed the Cirrus prior to the impact, his ability to maneuver to avoid an impact would have been severely limited due to the glider in tow. A postaccident examination of the engine and flight control systems on both airplanes revealed no mechanical anomalies that would have prevented either pilot from maneuvering to avoid an impact. Medical and pathological examination of both pilots revealed no medical or toxicological issues that would have precluded either pilot from operating their airplane in a safe manner prior to the accident.
HISTORY OF FLIGHT On February 6, 2010, at 1327 mountain standard time, a Cirrus SR20 airplane, N825BC, collided with a Piper PA-25-235 airplane, N8718L, while the Piper was conducting glider tow operations with a Schweizer SGS 2-32 glider, N2472W, near Boulder, Colorado. Both the Cirrus and the Piper were substantially damaged. The Schweizer was not damaged. The Cirrus was owned and piloted by a private individual. Mile High Gliding, Inc., operated both the Piper and the Schweizer. Visual meteorological conditions prevailed at the time of the accident. All three flights were being conducted under the provisions of 14 Code of Federal Regulations Part 91 without flight plans. The commercial pilot aboard the Piper and the private pilot and passenger aboard the Cirrus were all fatally injured. The commercial pilot and two passengers aboard the Schweizer were not injured. The Cirrus departed Erie Municipal Airport (KEIK), Erie, Colorado, as a local flight approximately 1245. The Piper and Schweizer departed Boulder Municipal Airport (KBDU), Boulder, Colorado, as a glider tow flight approximately 1320. According to a statement taken from the pilot of the Schweizer, the purpose of the flight was a scenic glider flight for a birthday party. The tow flight departed runway 8, performed a 360-degree turn for altitude on the east end of the airport, and then continued to a west/northwest heading. He stated that during this portion of the flight he was pointing out various landmarks in Boulder, and other aircraft in the vicinity, to the two passengers. The pilot of the Schweizer remarked that at 8,000 feet the tow rope was tight, they were climbing at 70 miles per hour, and that the air was smooth. At this approximate time and altitude, he observed a Cirrus airplane off the right side of his glider, less than 500 feet away. He was immediately concerned that the Cirrus was going to fly between the tow plane and the glider, and impact the tow line. He reached for the towline release, at which time the Cirrus impacted the forward right side of the tow plane at nearly a 90 degree angle. The Schweizer flew through a ball of fire and was able to return to KBDU shortly thereafter. The pilot of the Schweizer and one passenger on board the glider stated that they did not observe either the Piper or the Cirrus maneuver prior to the collision. The pilot of the Schweizer stated that prior to the impact there were no control movements or turbulence induced by control movements of the tow plane. He commented that the flight was extremely smooth and that normally he can feel control movements or inputs from the tow plane. He elaborated that he felt that the tow pilot would have tried to correct or make an evasive maneuver had he seen the Cirrus airplane prior to the impact. Multiple witnesses heard the collision between the two airplanes and observed the post collision state of both airplanes. The Cirrus was observed to descend under the canopy of the Cirrus Airframe Parachute System (CAPS) while on fire. Debris from both airplanes was spread over a 1.5-mile area with components of the Piper at the northern most end of the debris field, and the main wreckage of the Cirrus at the southern most end of the debris field. Radar data, provided by Denver Air Route Traffic Control Center (ZDV) in National Track Analysis Program (NTAP) format, identified and depicted the Cirrus flight from the time of departure from KEIK to the time of the accident. The encoded altitude of the Cirrus ranged from 6,800 feet to 8,800 feet mean sea level (msl). The flight track proceeded north from KEIK, maneuvered, and then reversed course back toward the south. Just prior to the accident the Cirrus was tracking an approximate course of 180 degrees. Radar data, provided by ZDV in NTAP format, identified and depicted the Piper flight from the time of departure from KBDU to the time of the accident. The altitude of the Piper was intermittent with only two altitudes recorded during the accident flight. The first was reported at 1320:58 at an encoded altitude of 5,500 feet. The second was recorded at 1322:57 at an encoded altitude of 6,500 feet. The Piper performed one turn in the vicinity of KBDU. Just prior to the accident the Piper was tracking an approximate course of 270 degrees. The radar data for the Cirrus depicted the airplane at a consistent altitude of 8,400 and 8,300 feet within the last minute of flight. There was no continuous altitude information associated with the radar data for the Piper tow flight; however, according to a statement from the glider pilot, they were climbing from the time of departure until the collision. He estimated the altitude at the time of the accident to be 8,000 feet. Neither the Cirrus pilot or the Piper pilot were receiving radar flight following services, nor were they in voice communications with air route traffic control. There was no requirement for them to be in voice communications with air route traffic control. PERSONNEL INFORMATION Cirrus Pilot The pilot of the Cirrus, age 58, held a private pilot certificate with an airplane single engine land rating. He was issued a third class airman medical certificate on December 4, 2008. The certificate contained the limitation “must wear corrective lenses.” The charred remains of the Cirrus pilot’s flight logbook was located with the wreckage of the Cirrus airplane. The pilot of the Cirrus had logged no less than 640 hours of total time; 359 hours of which were logged in the accident airplane make and model. He had completed the requirements for a flight review on May 15, 2009, and had received an endorsement to operate high performance airplanes on October 10, 2003. Piper Pilot The pilot of the Piper, age 25, held a commercial pilot certificate with airplane single and multiengine land, and instrument ratings. In addition, he held a certified flight instructor certificate with airplane single and multiengine ratings. He was issued a first class airman medical certificate, with no limitations, on February 12, 2009. Mile High Gliding submitted a completed Pilot/Operator Aircraft Accident/Incident Report form. On this form they reported that the pilot of the Piper had completed the requirements for a flight review on October 24, 2009. He had logged 1,110 hours total time; 260 hours of which were in the accident airplane make and model. Schweizer Pilot The pilot of the Schweizer, age 39, held a commercial pilot certificate with a glider rating, and an airplane single engine land, and instrument rating. In addition, he held a certified flight instructor certificate with airplane single engine, and instrument ratings. He was issued a third class airman medical certificate, with no limitations, on March 15, 2006. The pilot of the Schweizer submitted a completed Pilot/Operator Aircraft Accident/Incident Report form. On this form he reported that he had completed the requirements for a flight review on June 7, 2009. The pilot had logged 2,044 hours total time; 3 hours of which were in the make and model of the glider. AIRCRAFT INFORMATION Cirrus The Cirrus Design Corporation SR20 (serial number 20-1655) low wing airplane, predominately white in color with blue striping, was manufactured in May of 2006. It was registered with the Federal Aviation Administration (FAA) on a standard airworthiness certificate for normal operations. A Teledyne Continental Motors engine, IO-360-ES(6), rated at 210 horsepower at 2,700 rpm, powered the airplane. The engine was equipped with a three-blade, constant speed, Hartzell propeller. The Cirrus was registered to and operated by the Cirrus pilot, and was maintained under an annual inspection program. A review of the maintenance records indicated that Vector Air – Aircraft Inspection & Repair, Erie, Colorado, had completed an annual inspection on April 8, 2009, at a Hobbs hour reading of 319.0 hours. The engine oil was drained and the oil filter was inspected on December 11, 2009, at a Hobbs hour reading of 388.1 hours. Front Range Transponder Services of Bailey, Colorado, tested and inspected the Cirrus's altimeter system and altitude reporting equipment on May 28, 2008. The system was tested to 20,000 feet with no "leakage" noted. A traffic collision avoidance system was not installed on the accident Cirrus. The Cirrus was equipped with pilot controlled exterior navigation and anti-collision strobe lights. The navigation lights and strobe lights were co-located on the wing tips; the navigation lights were red on the left side and green on the right side, and the anti-collision strobe lights were white. Piper The Piper PA-25-235 (serial number 25-5173) low wing airplane was manufactured in 1969. It was registered with the FAA on a special airworthiness certificate, in the restricted category for glider towing operations. A Lycoming O-540-B2C5 engine rated at 235 horsepower at 2,575 rpm powered the Piper. The engine was equipped with a four-blade, wooden composite Hoffman propeller. The Piper was registered to and operated by Mile High Gliding Inc., and was maintained under an annual inspection program. A review of the maintenance records indicated that an annual inspection had been completed on December 7, 2009, at an airframe total time of 9,883 hours, and a recorded tachometer time of 3,346 hours. The Piper had flown 53.6 hours between the last inspection and the accident, and had a total airframe time of 9,936 hours. Front Range Transponder Services of Bailey, Colorado, tested and inspected the Piper’s altimeter system and altitude reporting equipment on June 18, 2008. The system was tested to 18,000 feet with no "leakage" noted. The Piper was not equipped with position or anti-collision lights; nor was it required to be equipped. Schweizer The Schweizer SGS 2-32 (serial number 47) glider, metallic color with yellow and red stripes, was manufactured in 1967. It was registered with the FAA on a standard airworthiness certificate for glider operations. The glider was registered to and operated by Mile High Gliding, Inc., and was maintained under a 100-hour inspection program. A review of the maintenance records indicated that a 100-hour inspection had been completed on February 1, 2010, at an airframe total time of 6,201 hours. The annual inspection had been completed on August 24, 2009, at an airframe total time of 6,104.3 hours. The glider was not equipped with a transponder. The Schweizer was not equipped with position or anti-collision lights; nor was it required to be equipped. METEOROLOGICAL INFORMATION The closest official weather observation station was Rocky Mountain Metropolitan Airport (KBJC), Denver, Colorado, located 14 nautical miles (nm) southeast of the accident site. The elevation of the weather observation station was 5,673 feet msl. The routine aviation weather report (METAR) for KBJC, issued at 1247, reported winds calm, visibility 8 miles, sky condition scattered clouds at 8,000 feet, overcast at 12,000 feet, temperature 4 degrees Celsius (C), dew point minus 6 degrees C, altimeter 29.89 inches. The METAR for KBJC issued at 1353 reported winds calm, visibility 10 miles, sky condition few clouds at 9,000 feet, overcast at 12,000 feet, temperature 5 degrees C, dew point minus 7 degrees C, altimeter 29.86 inches. AERODROME INFORMATION Boulder Municipal Airport (KBDU) was a public, uncontrolled airport (Class G) located 3 miles northeast of Boulder, Colorado, at 40 degrees, 2 minutes, 21 seconds north latitude, and 105 degrees, 13 minutes, 32 seconds west longitude, at an estimated elevation of 5,288 feet. Class E airspace was located just to the east and north of KBDU and Class D airspace for KBJC was located to the south of KBDU. KBDU is located within the Mode C, 30 nm veil, by 3/4 miles. The Boulder Municipal Airport website provided a depiction of the glider and tow plane traffic pattern at the airport. The flight track included a traffic pattern to the north and to the south of the airport with departures from the traffic pattern to the northwest and to the south. This map which depicted the flight track was also available at the airport. In addition to this information provided by the airport, the FAA Cheyenne and Denver Sectional Aeronautical Charts and the Denver VFR Terminal Area Chart depicted glider activity, with a symbol of a glider and the letter “G,” in the vicinity of KBDU. The Airport Facility Directory (AFD) published and maintained by the FAA stated that runway 08-26 G at KBDU was for glider use only. Further it stated that powered aircraft on approach to runway 08-26 should initiate a go around or yield right of way to gliders on final. There was no discussion of glider tow operations at the airport or in the vicinity of the airport. WRECKAGE AND IMPACT INFORMATION Wreckage debris from the Piper and the Cirrus were scattered over a 1.5 mile area. Measured field elevation was approximately 5,500 feet msl. The terrain where both wreckages came to rest was best characterized as rolling hills and rocky terrain, vegetated with wild grass, sagebrush, and yucca. Cirrus The largest identifiable portion of the Cirrus was categorized as the main wreckage and consisted of the fuselage, empennage, and both wing assemblies. The engine separated and was located 25 feet to the north of the main wreckage. The main wreckage was oriented on an approximate heading of 250 degrees and was positioned on a slope of approximately 10 degrees. The CAPS remained attached to the main wreckage, and came to rest downhill from the forward portion of the fuselage. Portions of the engine cowling, forward right fuselage, and personal effects were fragmented and scattered. The forward portion of the fuselage, to include the cabin seats and the instrument panel, extending aft to the empennage, was charred, melted, and partially consumed by fire. The ceiling of the airplane was destroyed. The multifunction display exhibited exposure to heat and fire. The damage precluded the recovery of any information. The primary flight display was not present with the main wreckage and the remains, including the memory card, were not recovered. The empennage, to include the horizontal stabilizer, elevator, vertical stabilizer, and rudder, remained attached to the fuselage and exhibited heat and fire damage. The upper portion of the vertical stabilizer was destroyed by fire. The surfaces were otherwise unremarkable. The flight control cables/tubes were continuous from the rudder and elevator control surfaces, forward, to the flight controls in the cabin. The CAPS remained attached to the main wreckage through the Kevlar straps at their respective mounted locations. The right wing remained partially attached and came to rest under the main wreckage. The right aileron was located on the left side of the airplane, adjacent to the remains of the outboard portion of the right wing. The right wing flap was located on the right side of the airplane. The right wing, aileron, and flaps exhibited extensive heat and fire damage. The outboard portion of the left wing, including the left aileron, separated from the airplane and was found adjacent the airplane. The left wing exhibited exposure to heat and fire. The inboard portion of the left wing, including the left flap was destroyed by fire. The flight control cables were continuous from aileron control surfaces, inboard, to the flight controls in the cabin. The engine assembly, to include the propeller, separated from the fuselage and came to rest approximately 25 feet north of the main wreckage. The engine cowling was fragmented and destroyed. It could not be determined if the anti-collision lights were on or operating at the time of the accident. Piper The largest identifiable components of the Piper were the engine and propeller assembly, the left wing assembly, the empennage, and two large segments of the fuselage. The right wing, portions of the fuselage, the body fabric, instrument panel, and personal effects were fragmented and scattered. The engine and propeller assembly was located to the north of the main scatter of wreckage. The left wing was located to the east of the main scatter of wreckage.
The failure of both pilots to see and avoid the other resulting in a midair collision. Contributing to the accident was the lack of perceived visual relative motion of the Piper and the Cirrus to the pilot of each airplane, the terrain background, and the overcast weather conditions making it difficult for either pilot to visually acquire the other aircraft.
Source: NTSB Aviation Accident Database
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