Prescott, AZ, USA
N561ER
American Champion (ACAC) 8KCAB
N562ER
American Champion (ACAC) 8KCAB
Two identically painted American Champion 8KCAB airplanes (N561ER and N562ER) collided in flight while performing a formation aerobatic hammerhead maneuver. The airport was hosting an airshow where the accident pilots were going to perform a formation aerobatic routine. Witnesses observed the two airplanes practicing the routine on several different occasions during the previous months, and had become familiar with it. They said that when the accident happened, a vertical climb was initiated with both airplanes side-by-side, and at the apex of the maneuver, one or both of the airplanes moved out of their normal positions, and they became stacked one on top of the other. After the airplanes initial contact, witnesses observed several additional contacts as the airplanes fell to the ground. Color transfers, damage patterns, and witness marks found that the propeller of N561ER made multiple contacts to the engine compartment and cockpit of N562ER, while contact between the left lift strut of N562ER and the empennage of N561ER damaged and separated the vertical and horizontal stabilizers of N561ER. An airframe and engine examination of both airplanes revealed no mechanical discrepancies that would have precluded normal operation and control.
HISTORY OF FLIGHT On August 28, 2004, at 0831 mountain standard time, two American Champion Aircraft 8KCAB, N561ER (Riddle 61) and N562ER (Riddle 62), collided in midair while performing formation aerobatics 7 miles east of Ernest A. Love Field (PRC), Prescott, Arizona. Both airplanes were owned and operated by Embry-Riddle Aeronautical University (ERAU) under the provisions of 14 CFR Part 91. Both airplanes were destroyed. The commercial certificated pilot of Riddle 61, the sole occupant, and the airline transport certificated pilot of Riddle 62, the sole occupant, were both fatally injured. The personal flights departed PRC at 0818, with the intent of practicing for an upcoming aerobatic performance. Day visual meteorological conditions prevailed, and no flight plans had been filed for the local area flight. Both pilots were faculty members at ERAU. The pilot of Riddle 61 was the program Chair for the Aeronautical Science Department. The pilot of Riddle 62 was the school's Chief Flight Instructor. Both were experienced aerobatic pilots, and instructed and mentored the school's aerobatic club. The pilots were practicing an aerobatic routine at the time of the accident that was to be the highlight of the ERAU sponsored Prescott Air Fair scheduled for October 2, 2004. The National Transportation Safety Board investigator-in-charge (IIC) interviewed several witnesses who were hunting in the area at the time of the accident. They had observed the accident airplanes perform several times in the past months, were accustomed to the airplanes, and familiar with the routine. The airplanes had completed the routine once, and were setup for the second pass. The witnesses reported that the airplanes completed one maneuver and pulled out low to the ground. While in formation, they maneuvered into a nose up to a vertical attitude. They saw one airplane overtake the other, and a collision ensued. Both airplanes appeared as if they were out of control as they fell to the ground. Immediately after the collision several pieces of both airplanes began to fall to the ground, though the witnesses could not distinguish what parts they were. The Safety Board IIC, along with an ERAU representative, ascertained from witness interviews that Riddle 61 was in the high and to the right position relative to Riddle 62 during the vertical climb. At the apex of the maneuver one or both of the airplanes traveled out of position in the formation flight and became stacked one on top of the other; Riddle 61 on top, Riddle 62 on the bottom. The airplane's contacted each other, with numerous additional contact made during the descent, until the airplane's separated prior to ground impact. A flight instructor at ERAU saw both pilots the morning of the accident and said they were both in good humor. He observed the airplanes taxi off the ERAU flight line about 0810. The Safety Board IIC reviewed the planned routine program located in Riddle 62. According to the ERAU party representative, maneuver 3 was a hammerhead maneuver in formation. PERSONNEL INFORMATION Riddle 61 The operator reported that the pilot of Riddle 61 held a commercial pilot certificate with ratings for airplane single engine land and sea, multiengine land, and instrument airplane. He held a certified flight instructor (CFI) certificate with ratings for airplane single engine land and instrument airplane. The pilot held a second-class medical certificate issued on October 6, 2003. It had the limitation that the pilot must wear corrective lenses. The operator reported that the pilot had a total flight time of 4,901.9 hours. He logged 22.5 hours in the last 90 days, and 4.3 hours in the last 30 days, all in the accident make and model. He had an estimated 371.6 hours in accident make and model. He completed a flight review in September 2003. Riddle 62 The operator reported that the pilot of Riddle 62 held an airline transport pilot certificate with ratings for airplane single engine land, multiengine land, and instrument airplane. He held a certified flight instructor (CFI) certificate with ratings for airplane single engine land, multiengine land, and instrument airplane. The pilot held a second-class medical certificate issued on December 10, 2003. It had the limitation that the pilot must possess corrective glasses for near vision. The operator reported that the pilot had a total flight time of 6,707.1 hours. He logged 32.2 hours in the last 90 days, and 17.6 in the last 30 days, of which 10.4 were in the accident make and model. He had an estimated 129.8 hours in this make and model. He completed a flight review in April 2003. AIRCRAFT INFORMATION Riddle 61 The airplane was an American Champion Aircraft 8KCAB, serial number 934-2003. The operator reported that the airplane had a total airframe time of 286.5 hours at the last 100-hour inspection dated July 16, 2004. A Lycoming AEIO-360-H1B engine, serial number L-31198-51A, was installed on the airplane. Total time recorded on the engine at the last 100-hour inspection dated July 16, 2004, was 286.5 hours. Examination of the maintenance and flight department records revealed no unresolved maintenance discrepancies against the airplane prior to departure. Riddle 62 The airplane was an American Champion Aircraft 8KCAB, serial number 935-2003. The operator reported that the airplane had a total airframe time of 264.9 hours at the last 100-hour inspection dated August 6, 2004. A Lycoming AEIO-360-H1B engine, serial number L-31196-51A, was installed on the airplane. Total time recorded on the engine at the last 100-hour inspection dated August 6, 2004, was 264.9 hours. Examination of the maintenance and flight department records revealed no unresolved maintenance discrepancies against the airplane prior to departure. METEOROLOGICAL INFORMATION The closest official weather observation station was PRC, located 7 nautical miles (nm) west of the accident site. The elevation of the weather observation station was 5,000 feet mean sea level (msl). An aviation routine weather report (METAR) for PRC at 0853 reported calm winds; visibility 10 statute miles and clear skies; temperature 23 degrees Celsius; dew point 03 degrees Celsius; altimeter 30.20 inHg. WRECKAGE AND IMPACT INFORMATION The Safety Board IIC examined both airplanes at the accident site on August 29, 2004. Both airplanes were predominantly blue and white in the ERAU paint scheme. The tops of the wings, tail, and fuselage were blue. The bottoms of the wings were white. There was a gold spiraling strip from the nose to the tail of both airplanes. The propellers of both airplanes were made of wood and composite material. The tips of the propellers contained a chordwise red stripe. Riddle 62 came to rest about 400 feet north of Riddle 61. The surrounding area was flat desert terrain. Riddle 61 The main wreckage was found at 5,080 feet msl, at the approximate global positioning system (GPS) coordinates of 34 degrees 37.591 minutes north latitude and 112 degrees 14.672 minutes west longitude. The airplane impacted the ground in a nose down attitude. The fuselage was lying adjacent to the left wing. The tail section separated from the airplane. The horizontal stabilizer, portions of the tail and tail cone, elevator trim tab, elevator, vertical stabilizer, and rudder separated from the airplane and were distributed in the debris field about 500 feet northeast of the main wreckage. One propeller blade remained attached at the propeller hub. Impact forces destroyed the other propeller blade; however, parts of it were buried beneath the propeller hub in its relative normal position. Both wings were oriented with the leading edge down in an almost vertical attitude, and exhibited extensive spanwise crush damage from the leading edge to the trailing edge. The right wing aft area had a semicircular indentation as well as blue paint transfer signatures. Riddle 62 The main wreckage was found at 5,071 feet msl, at the approximate GPS coordinates of 34 degrees 37.534 minutes north latitude and 112 degrees 14.598 minutes west longitude. The airplane impacted the ground in a slight nose down attitude. The wings and tail sections remained attached to the fuselage and in their relative normal positions. Flight control continuity from the cockpit to the rudder with movement of the associated rudder cables was established. Flight control continuity could not be established to the elevator. Both wings had leading edge crush damage; however, the damage started at the lower portion of the leading edge and pushed both wings up and aft to the trailing edge. Both propeller blades splintered and separated from the propeller hub. The Safety Board IIC noted wood chips and wood debris consistent with propeller blade material located in a debris field about 400 feet east of the main wreckage. MEDICAL AND PATHOLOGICAL INFORMATION Riddle 61 The Yavapai County Coroner completed an autopsy on August 31, 2004. The cause of death was determined to be multiple blunt force trauma injuries as a result of an airplane accident. The Federal Aviation Administration (FAA) Bioaeronautical Sciences Research Laboratory, Oklahoma City, Oklahoma, performed toxicological testing of specimens of the pilot. The results of the analysis of the specimens were negative for carbon monoxide, cyanide, volatiles, and tested drugs. Riddle 62 The Yavapai County Coroner completed an autopsy on August 31, 2004. The cause of death was determined to be multiple blunt force trauma injuries as a result of an airplane accident. The Federal Aviation Administration (FAA) Bioaeronautical Sciences Research Laboratory, Oklahoma City, performed toxicological testing from specimens of the pilot. The results of the analysis of the specimens were negative for carbon monoxide, cyanide, volatiles, and tested drugs. The pilot's headset was recovered during the post examination of the wreckage. The right ear cushion had a 45-degree cut consistent with propeller blade contact. The headset cord was found wrapped around the overhead lateral crossbeam. The left ear cushion was untouched. TESTS AND RESEARCH The Safety Board investigator examined the wreckage of both airplanes at Air Transport, Phoenix, Arizona, on November 6, 2004. There were no mechanical anomalies noted with either airplane that would have precluded normal operation. Riddle 61 The spark plugs for the number 2 and 4 cylinders were removed with no abnormalities observed. The remaining sparks plugs sustained impact damage and could not be removed for inspection. Manual rotation of the propeller hub produced thumb compression in the numbers 1 and 3 cylinders. Thumb compression was not obtained in the numbers 2 and 4 cylinders due to impact damage. Both magnetos separated from their respective mounting pads and were destroyed in the impact sequence precluding any additional functional tests. Red markings consistent with the paint stripe on the tips of both airplanes' propellers were found on the leading edge of the right wing. The wing had separated along the rivet line and red paint transfers consistent with propeller tip color was found inside the leading edge wing skin. The vertical stabilizer displayed impact damage that was similar in dimension to the left lift strut of Riddle 62. There was a crush impression at the top of the leading edge of the vertical stabilizer. The right horizontal stabilizer failed in an upward direction. The left horizontal stabilizer strut brace displayed signatures of overload failure. The right main landing gear exhibited signs of lateral blue paint transfer. Riddle 62 The spark plugs for all cylinders were removed and no abnormalities were noted. The engine rotated normally and thumb compression was attained on all cylinders. The top of the right wing root displayed rubber transfer and damage consistent with a tire impression. The headliner, intercom box, and windscreen displayed damage patterns and red paint transfer consistent with propeller contact. The rear of the left wing struts displayed multiple blue paint transfer marks. The left main landing gear strut displayed multiple scuffs and paint transfer that was matched to the right horizontal stabilizer of Riddle 61. ADDITIONAL INFORMATION The Safety Board investigator released both airplanes to the owner's representative on November 6, 2004.
The failure of both pilots to maintain adequate clearance from each other while performing formation aerobatic maneuvers.
Source: NTSB Aviation Accident Database
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