DEN03MA035

History of flight

On January 24, 2003, at 1720:36 mountain standard time, a Piper PA-31T, N360LL, registered to and operated by Lee Larson Aircraft Sales of Northglenn, Colorado, and a Cessna 172P, N52241, registered to EDB Air, Inc., and doing business as Key Lime Flights of Englewood, Colorado, collided in midair over Denver, Colorado. The commercial pilot-in-command and the commercial certificated pilot-passenger aboard N360LL and the private pilot and two passengers aboard N52241 were fatally injured. The Denver Police Department (DPD) reported that six persons on the ground, including a 15-year old boy and a 2-year old girl, received minor injuries from falling debris. Visual meteorological conditions prevailed, and neither pilot had filed flight plans. Both flights were being operated under Title 14 CFR Part 91. N5224's flight originated at Centennial Airport, Englewood, Colorado, at 1708, and was en route to Cheyenne, Wyoming. N360LL's flight originated at Jeffco Airport, Broomfield, Colorado, at 1716, and was en route to Centennial Airport.

At 1708, the pilot of N52241 was cleared for takeoff from Centennial Airport's runway 17L, and to proceed VFR (visual flight rules) "on course." At 1716, the pilot of N360LL was cleared for takeoff from Jeffco Airport's runway 29R, VFR, with a southbound departure. At 1717:52, the pilot of N360LL contacted Denver Terminal Radar Control (TRACON) and advised "We're just off Jeffco, down to Centennial." [At this point, radar data indicated N52241 was about 10 miles northwest of Centennial, its transponder transmitting a beacon code of 1200 (VFR)]. At 1718:04, the controller assigned the pilot a transponder beacon code of 5250. At 1718:26, he identified the airplane on radar: "Cheyenne Zero Lima Lima, radar contact, four (miles) south of Jeffco. Proceed as requested. [Note: According to NTSB's Operational Factors Division (AS-30), "proceed as requested" does not constitute an ATC clearance, which requires an aircraft to proceed under conditions specified by ATC, nor was one required because the pilot was operating in Class E airspace under visual flight rules.] I'm not getting any mode C on you. You squawking altitude?" The pilot replied, "Ah, yes, sir, we are." [At this point, radar data indicated N360LL was 10.73 miles from N52241]. At 1718:34, the controller asked the pilot for his altitude. He replied he was at 7,800 feet. [Radar data indicated the N360LL's mode C was still inoperative and it remained so throughout the flight. The radar-computed ground speed indicated "23," or 230 knots.]

At 1718:58, the pilot of N52241 contacted Denver Terminal Radar Control (TRACON): "Denver, Cessna Five Two Two Four One is over Denver at seven thousand, three hundred feet, with a request." The controller issued the pilot a transponder beacon code of 5251. The pilot acknowledged the instruction and requested clearance to climb to 8,500 feet, which would place the airplane in Class B airspace. He also advised he was en route to Cheyenne. [At this point, Centennial tower called the controller with a request for another aircraft's IFR departure release. The controller issued the release and assigned a departure heading of 050 degrees, then coordinated the departure with the south sector controller]. At 1720:04, the controller identified the airplane on radar when it was 15 miles southeast of Jeffco Airport, and asked the pilot to repeat his requested altitude. He repeated his request for 8,500 feet. [At this point, separation between N360LL and N52241 had closed to 2.91 miles. N52241's radar-computed ground indicated "11," or 110 knots. At about this time, the controller made a transmission to an aircraft that was on the downwind leg at Centennial Airport. He then vectored another airplane onto the NDB (nondirectional beacon) approach to Centennial Airport. The controller was also monitoring other aircraft that were getting close to a restricted area and the airport traffic area]. At 1720:16, the controller cleared N52241 to enter class B airspace and climb to 8,500 feet. Two seconds later, radar showed target separation as 1.64 miles. At 1720:22, target separation was 1.20 miles. At 1720:27, target separation was 0.80 miles.

At 1720:28, the controller asked the pilot of N360LL to report his altitude. The pilot replied, "(Unintelligible) six." The controller said, "Say again." At 1720:31, target separation had reduced to 0.29 miles. The pilot said, "Seven thousand, six hundred." At 1720:33, the controller issued the pilot a traffic advisory: "Traffic is at twelve o'clock and a mile at seventy seven hundred, a Cessna." The pilot did not acknowledge this transmission. At 1720:36, the two airplanes were 0.06 miles apart. Immediately thereafter, radar data indicated both targets had entered "coast" mode (i.e. computer-generated projection of targets' tracks and positions). At 1720:47, the controller advised N360LL that the previously reported traffic was no longer a factor and issued another advisory for traffic 4 miles away. Receiving no reply from the pilot, the controller attempted several times to contact both airplanes. The controller then contacted a traffic patrol pilot and asked him to fly over the area where radar contact was lost. Shortly thereafter, the traffic patrol pilot reported that it appeared there had been an accident. The TRACON controller initiated search and rescue procedures.

The collision occurred 2 minutes, 43 seconds and 1 minute, 35 seconds after the pilots of N360LL and N52241 made initial contact with Denver TRACON, respectively.

DPD took written statements from 113 witnesses, three of whom were pilots. Of those witnesses, 32 were interviewed and those interviews were videotaped. The majority of the witnesses reported hearing a loud noise, variously described as a bang, pop, or explosion. Looking up into the sky, they saw a wing(s) falling to the ground and a twin engine airplane enter an inverted flat spin and fall straight down. A small, single-engine airplane was seen to nosedive into a house, trailing debris. Five witnesses made note of the light conditions: either the sun was setting or had gone below the horizon. "There was still light out," wrote one witness. There was "no trouble seeing," said another. Seventeen witnesses reported hearing an engine "stalling" or "sputtering." Some described it as "revving up." Three witnesses said the engine restarted. Several witnesses noted that the twin engine airplane was traveling "quite fast." One witness said he saw "white streak in the sky." Another said one airplane was on fire, and 12 other witnesses said one or both airplanes trailed smoke as they plummeted to the ground.

Of the 113 known witnesses, NTSB contacted 17 who actually saw the airplanes prior to or at the time of the collision. One witness saw "both airplanes heading toward each other" at "low altitude." He wrote, "...the two planes were trying to avoid each other, both in a heavy right bank." Then, "the smaller plane hit the left wing of the twin engine, severing it from the fuselage." Through an interpreter, another witness wrote: "I see two planes doing a hard right turn...and they hit." A third witness wrote, "I see the two planes coming together. The plane heading south started to bank turn away when it clip the wing" (sic). Two witnesses reported seeing the Cessna at about 1,000 feet and banking to the right at the last instant. Still another witness said the Piper pulled up and banked to the right just before the collision. One witness said he saw the "two planes veering away from each other and the wings clipped each other...The planes seemed to be coming from the north and south and when they hit, they seemed to hit wing to wing at a 45 degree angle." Two other witnesses who claim to have seen the actual collision said that neither airplane made any evasive maneuver.

Of those witnesses who saw the collision, most did not notice any lights on either

History of flight

On January 24, 2003, at 1720:36 mountain standard time, a Piper PA-31T, N360LL, registered to and operated by Lee Larson Aircraft Sales of Northglenn, Colorado, and a Cessna 172P, N52241, registered to EDB Air, Inc., and doing business as Key Lime Flights of Englewood, Colorado, collided in midair over Denver, Colorado. The commercial pilot-in-command and the commercial certificated pilot-passenger aboard N360LL and the private pilot and two passengers aboard N52241 were fatally injured. The Denver Police Department (DPD) reported that six persons on the ground, including a 15-year old boy and a 2-year old girl, received minor injuries from falling debris. Visual meteorological conditions prevailed, and neither pilot had filed flight plans. Both flights were being operated under Title 14 CFR Part 91. N5224's flight originated at Centennial Airport, Englewood, Colorado, at 1708, and was en route to Cheyenne, Wyoming. N360LL's flight originated at Jeffco Airport, Broomfield, Colorado, at 1716, and was en route to Centennial Airport.

At 1708, the pilot of N52241 was cleared for takeoff from Centennial Airport's runway 17L, and to proceed VFR (visual flight rules) "on course." At 1716, the pilot of N360LL was cleared for takeoff from Jeffco Airport's runway 29R, VFR, with a southbound departure. At 1717:52, the pilot of N360LL contacted Denver Terminal Radar Control (TRACON) and advised "We're just off Jeffco, down to Centennial." [At this point, radar data indicated N52241 was about 10 miles northwest of Centennial, its transponder transmitting a beacon code of 1200 (VFR)]. At 1718:04, the controller assigned the pilot a transponder beacon code of 5250. At 1718:26, he identified the airplane on radar: "Cheyenne Zero Lima Lima, radar contact, four (miles) south of Jeffco. Proceed as requested. [Note: According to NTSB's Operational Factors Division (AS-30), "proceed as requested" does not constitute an ATC clearance, which requires an aircraft to proceed under conditions specified by ATC, nor was one required because the pilot was operating in Class E airspace under visual flight rules.] I'm not getting any mode C on you. You squawking altitude?" The pilot replied, "Ah, yes, sir, we are." [At this point, radar data indicated N360LL was 10.73 miles from N52241]. At 1718:34, the controller asked the pilot for his altitude. He replied he was at 7,800 feet. [Radar data indicated the N360LL's mode C was still inoperative and it remained so throughout the flight. The radar-computed ground speed indicated "23," or 230 knots.]

At 1718:58, the pilot of N52241 contacted Denver Terminal Radar Control (TRACON): "Denver, Cessna Five Two Two Four One is over Denver at seven thousand, three hundred feet, with a request." The controller issued the pilot a transponder beacon code of 5251. The pilot acknowledged the instruction and requested clearance to climb to 8,500 feet, which would place the airplane in Class B airspace. He also advised he was en route to Cheyenne. [At this point, Centennial tower called the controller with a request for another aircraft's IFR departure release. The controller issued the release and assigned a departure heading of 050 degrees, then coordinated the departure with the south sector controller]. At 1720:04, the controller identified the airplane on radar when it was 15 miles southeast of Jeffco Airport, and asked the pilot to repeat his requested altitude. He repeated his request for 8,500 feet. [At this point, separation between N360LL and N52241 had closed to 2.91 miles. N52241's radar-computed ground indicated "11," or 110 knots. At about this time, the controller made a transmission to an aircraft that was on the downwind leg at Centennial Airport. He then vectored another airplane onto the NDB (nondirectional beacon) approach to Centennial Airport. The controller was also monitoring other aircraft that were getting close to a restricted area and the airport traffic area]. At 1720:16, the controller cleared N52241 to enter class B airspace and climb to 8,500 feet. Two seconds later, radar showed target separation as 1.64 miles. At 1720:22, target separation was 1.20 miles. At 1720:27, target separation was 0.80 miles.

At 1720:28, the controller asked the pilot of N360LL to report his altitude. The pilot replied, "(Unintelligible) six." The controller said, "Say again." At 1720:31, target separation had reduced to 0.29 miles. The pilot said, "Seven thousand, six hundred." At 1720:33, the controller issued the pilot a traffic advisory: "Traffic is at twelve o'clock and a mile at seventy seven hundred, a Cessna." The pilot did not acknowledge this transmission. At 1720:36, the two airplanes were 0.06 miles apart. Immediately thereafter, radar data indicated both targets had entered "coast" mode (i.e. computer-generated projection of targets' tracks and positions). At 1720:47, the controller advised N360LL that the previously reported traffic was no longer a factor and issued another advisory for traffic 4 miles away. Receiving no reply from the pilot, the controller attempted several times to contact both airplanes. The controller then contacted a traffic patrol pilot and asked him to fly over the area where radar contact was lost. Shortly thereafter, the traffic patrol pilot reported that it appeared there had been an accident. The TRACON controller initiated search and rescue procedures.

The collision occurred 2 minutes, 43 seconds and 1 minute, 35 seconds after the pilots of N360LL and N52241 made initial contact with Denver TRACON, respectively.

DPD took written statements from 113 witnesses, three of whom were pilots. Of those witnesses, 32 were interviewed and those interviews were videotaped. The majority of the witnesses reported hearing a loud noise, variously described as a bang, pop, or explosion. Looking up into the sky, they saw a wing(s) falling to the ground and a twin engine airplane enter an inverted flat spin and fall straight down. A small, single-engine airplane was seen to nosedive into a house, trailing debris. Five witnesses made note of the light conditions: either the sun was setting or had gone below the horizon. "There was still light out," wrote one witness. There was "no trouble seeing," said another. Seventeen witnesses reported hearing an engine "stalling" or "sputtering." Some described it as "revving up." Three witnesses said the engine restarted. Several witnesses noted that the twin engine airplane was traveling "quite fast." One witness said he saw "white streak in the sky." Another said one airplane was on fire, and 12 other witnesses said one or both airplanes trailed smoke as they plummeted to the ground.

Of the 113 known witnesses, NTSB contacted 17 who actually saw the airplanes prior to or at the time of the collision. One witness saw "both airplanes heading toward each other" at "low altitude." He wrote, "...the two planes were trying to avoid each other, both in a heavy right bank." Then, "the smaller plane hit the left wing of the twin engine, severing it from the fuselage." Through an interpreter, another witness wrote: "I see two planes doing a hard right turn...and they hit." A third witness wrote, "I see the two planes coming together. The plane heading south started to bank turn away when it clip the wing" (sic). Two witnesses reported seeing the Cessna at about 1,000 feet and banking to the right at the last instant. Still another witness said the Piper pulled up and banked to the right just before the collision. One witness said he saw the "two planes veering away from each other and the wings clipped each other...The planes seemed to be coming from the north and south and when they hit, they seemed to hit wing to wing at a 45 degree angle." Two other witnesses who claim to have seen the actual collision said that neither airplane made any evasive maneuver.

Of those witnesses who saw the collision, most did not notice any lights on either