Denver, CO, USA
N360LL
Piper PA-31T
N52241
Cessna 172P
A Piper PA-31T "Cheyenne" and a Cessna 172P "Skyhawk" collided in midair during cruise flight at dusk and in visual meteorological conditions. The Cheyenne departed under visual flight rules (VFR) from a local airport northwest of Denver, and was proceeding direct at 7,800 feet to another local airport south of Denver. Radar indicated its ground speed was 230 knots. Its altitude encoder was transmitting intermittently. The Skyhawk departed VFR from the south airport and was en route to Cheyenne, Wyoming, at 7,300 feet. The pilot requested and was cleared to climb to 8,500 feet and penetrate class B airspace. Radar indicated its ground speed was 110 knots. The Skyhawk was flying in the suggested "VFR flyway"; the Cheyenne was not. When the controller observed the two airplanes converging, he asked the pilot of the Cheyenne for his altitude. He replied he was at 7,600 feet. The controller immediately issued a traffic advisory, but the pilot did not acknowledge. Both airplanes departed controlled flight: the Skyhawk struck a house, and the Cheyenne fell inverted into the backyard of a residence. Wreckage was scattered over a 24 square block area in west Denver. At the time of the accident, the controller was handling low altitude en route, arrival and departure traffic for both airports. Wreckage examination disclosed four slashes, consistent with propeller strikes, on top of the Cheyenne's right engine nacelle, the cabin above the right wing trailing edge, the empennage at the root of the dorsal fin, and at the tail cone. The Cheyenne was on a similar flight three days before the collision when the pilot was informed by air traffic control that the transponder was operating intermittently. According to recorded radar and voice communications from that flight, the transponder/encoder operated intermittently and the pilot was so advised. Examination of the Cheyenne's altimeter/encoder revealed a cold solder connection on pin 8 of the 15-pin altimeter connector. When the wire was resoldered to the pin, the information from the altimeters, encoder, and altitude serializer was normal.
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 airplane. One witness wrote, "The Cessna 172 Skyhawk did have his or her landing lights on, wing tips, tail." Another witness said she "definitely saw strobe lights" on one of the Cheyenne's wings. OTHER DAMAGE N360LL was found inverted in the backyard of a residence at 3221W. 26th Avenue. Nearby were a toppled utility shed and a section of downed wooden fence. N52241 struck a house at 3421 W. Moncrieff Place in the Highland neighborhood. The impact ruptured a natural gas line and caused an explosion, blowing out the walls and collapsing a portion of the roof. After the wreckage was removed, building engineers determined the house was not safe for occupancy and it was razed. N350LL's horizontal stabilizer struck a parked automobile at 26th Avenue and Julian Street, breaking out its windshield and damaging the hood. N360LL's right engine fell into the front yard of a house at 3126 W. 25th Avenue. PERSONNEL INFORMATION The 57-year-old pilot of N360LL held a commercial pilot certificate with airplane single/multiengine land and instrument ratings, dated December 19, 1982; a flight instructor certificate with airplane single/multiengine and instrument ratings, dated April 14, 2002; and a ground instructor certificate with a basic rating, dated May 8, 1982. His second class airman medical certificate, dated August 20, 2002, contained the restriction, "Holder shall wear lenses that correct for distant vision and possess glasses that correct for near vision while exercising the privileges of his airman certificate." He also held a Statement of Demonstrated Ability, Waiver No. 10D07725, dated October 31, 1977. It required the wearing of corrective lenses due to "defective distant vision 20/200, corrected to 20/15 bilaterally." According to documents submitted by his insurance company, the pilot had satisfactorily completed FlightSafety International's Cheyenne I/IA/II/IIXL pilot recurrent course on May 22, 1998; a flight review and instrument proficiency check on May 24, 2000, and SimCom Training Center's turbine multiengine instrument refresher course on May 9, 2001. A photo static copy of the pilot's logbook VII, containing entries from May 24, 2000, to January 21, 2003, was also provided by the insurance company and revealed the following: Total Time: 9,365.3 Airplane Single-Engine Land: 7,221 Airplane Multiengine Land: 2,018.1 Pilot-in-Command: 9,067.0 Night: 792.3 Cross-Country: 7,768.4 Dual Instruction Received: 179.8 Actual Instruments: 1,210.8 Simulated Instruments: 117.1 The 51-year-old pilot certificated-passenger aboard N360LL held a commercial pilot certificate with airplane single/multiengine land and instrument ratings, dated December 29, 1996, and a mechanic certificate with airframe and powerplant ratings, dated September 12, 1986. He also held a first class airman medical certificate, dated October 1, 2001, with no restrictions or limitations. According to documents submitted by his insurance company, the pilot had satisfactorily completed SimCom Training Center's high altitude ground/flight instruction and a Cheyenne II recurrent course on November 1, 2000; instrument and pilot proficiency checks on June 9, 1999, and November 1, 2000, and In Flight Review's Cheyenne I recurrent ground and flight training on January 21, 2002. Additional endorsements found in his logbook included a satisfactory FAR 61.56(a) flight review taken in a Piper PA-34-200T, dated June 29, 2002. A photostatic copy of the pilot's logbooks 1, 2, and 3, containing entries from March 11, 1979, to September 8, 1992; September 14, 1992, to June 4, 1999; and June 5, 1999, to December 1, 2002, respectively, was also provided by the insurance company, and revealed the following: Total Time: 1,944.2 Airplane Single-Engine Land: 1,094.0 Airplane Multiengine Land: 850.2 Pilot-in-Command: 1,696.6 Night: 57.6 Cross-Country: 1,232.3 Dual Instruction Received: 263.4 Actual Instruments: 103.2 Simulated Instruments: 59.1 The 20-year-old pilot of N52241 held a private pilot certificate with an airplane single-engine land rating, dated June 19, 2002. The private pilot practical test constituted his mandatory flight review [FAR 61.56(c)(d)]. His third class airman medical certificate, dated April 12, 2001, contained the restriction, "Holder shall wear lenses that correct for distant vision and possess glasses that correct for near vision." His logbook, found by Denver police, contained entries from December 21, 1995, to January 19, 2003, and revealed the following: Total Time: 127.5 Airplane Single-Engine Land: 127.5 Pilot-in-Command: 58.5 Cessna 172: 123.7 Piper PA-28: 3.8 Night: 14.6 Cross-Country: 24.0 Dual Instruction Received: 70.0 Simulated Instruments: 4.9 According to FAA records, none of the passengers aboard N52241 were certificated pilots. The SR1 (satellite radar) TRACON controller was hired by the Federal Aviation Administration on February 9, 1990. He transferred to the Denver TRACON on January 3, 1999, after having served in control towers at Vero Beach, Florida; Centennial and Denver International Airports. He was fully rated at the TRACON on November 26, 2000. The controller holds an airline transport pilot certificate with an airplane multiengine rating and a Beech 1900 type rating, and commercial pilot privileges in airplanes single-engine land. His second class airman medical certificate, dated April 30, 2002, contained no restrictions or limitations. At the time of the accident, the SR1 controller's position had been combined with JEFCO Low Altitude radar (LR). In addition to en route traffic at and below 9,000 feet, the controller was responsible for arrival and departure traffic from Jefferson County Airport (BJC) and Centennial Airport (APA). AIRCRAFT INFORMATION N360LL (s/n 31T-7520036), a pressurized model PA-31T, was manufactured by the Piper Aircraft Corporation and issued an airworthiness certificate on June 20, 1975. It was equipped with two Pratt & Whitney PT6A-28A-28 engines (s/n PCE-50375, left; PCE-50393, right), rated at 620 shaft horsepower, and two Hartzell 3-blade, all-metal, constant speed, and full-feathering propellers (m/n HC-B3TN-3B). Its maximum certificated gross weight was 9,000 pounds. The airframe was maintained following the Piper Progressive Inspection 100 Hour Cycle Program. A review of the maintenance records revealed the following: Airframe Total Time: 6,478.2 hours. Last 100-hour Inspection (Events I and II): 6,478.2 hours. On December 10, 2001, maintenance on the engines and propellers were transferred to the M.O.R.E. (Maintenance On Reliable Engines) program, where time and numbers (not dates) determined maintenance events: Left Engine Total Time: 7,093.6 hours Total Cycles: 7,094 Time Since Major Overhaul: 3,809.3 hours Cycles Since Major Overhaul: 3,811 Right Engine Total Time: 8,183.8 hours Total Cycles: 8,184 Time Since Major Overhaul: 3,811.3 hours Cycles Since Major Overhaul: 3,811 Left Propeller Total Time: 6,478.2 hours Major Overhaul: December 10, 2001 Right Propeller Total Time: 6,478.2 hours Major Overhaul: December 10,2001 Avionics Last IFR Certification: June 14, 2001 at 295.8 hrs. N52241 (s/n 17274452), a model 172P, was manufactured by the Cessna Aircraft Company in 1981. Modified by Supplemental Type Certificate SA2196CE, it was equipped with a Lycoming O-360-A4M engine (s/n L-12931-36A), rated at 180 horsepower, and a Sensenich 2-blade, all-metal, fixed pitch propeller (m/n 76EM8SPY-O-60). Its maximum certificated gross weight was increased from 2,400 pounds to 2,550 pounds. A review of the maintenance records revealed the following: Airframe Last 100-Hour Inspection: January 8, 2003 Tachometer: 2,875.6 hrs. Airframe Total Time: 12,872.9 hrs. Last Annual Inspection: July 25, 2002 Engine Last 100-Hour Inspection: January 8, 2003 Tachometer: 2,875.6 hrs. Time Since Major Overhaul: 201.0 hrs. Major Overhaul: July 25, 2002 Engine Total Time: 12,673.2 hrs. Propeller Last 100-Hour Inspection: January 8, 2003 Tachometer: 2,875.6 hrs Propeller Total Time: 6,538.3 hrs. Last Annual Inspection: October 23, 2001 Propeller Total Time: 6,140.4 hrs. Avionics Last IFR Certification: October 16, 2001 Tachometer: 2,675.
Both pilots' inadequate visual lookout. A contributing factor was the Cheyenne pilot operating the airplane with a known transponder deficiency.
Source: NTSB Aviation Accident Database
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