Julian, CA, USA
N304PA
Piper PA-44-180
The twin engine airplane collided with rising mountainous terrain while in cruise flight on an IFR clearance. The airplane, N304PA, was on a night IFR flight and was number four in a trail of five company airplanes flying the same route. The time separation between each airplane was about 5 to 10 minutes. The airplane directly ahead of N304PA was N434PA. After being handed off from Los Angeles Center, the flight crew of N304PA contacted the TRACON sector controller at 2043:48 PDT, reporting level at 8,000. The TRACON sector controller instructed the pilot to fly heading 260 after the Julian VOR and intercept the localizer. At 2045:47, the TRACON sector controller told the pilot of N434PA to descend to 6,000 feet. The pilot of N434PA acknowledged the clearance. At 2047:55, the sector controller transmitted, "Seminole four papa alpha descend and maintain five thousand two hundred." The pilot of N304PA responded, "Down to five thousand two hundred for three zero four papa alpha." According to information provided by the TRACON sector controller, this clearance was intended for N434PA. The controller did not recognize that the clearance had been acknowledged by N304PA rather than N434PA. At 2049:55, the pilot of N304PA reported that he had ATIS information Zulu and the sector controller responded, "Seminole three zero four papa alpha thank you very much." At that time the data block on the TRACON controller's display was showing N304PA descending through about 6,600 feet. The Minimum Enroute Altitude for the airway segment being flown was 7,700 feet. At 2050:27, the sector controller again cleared N434PA to descend and maintain 5,200 feet. A Minimum Safe Altitude Warning (MSAW) alert on N304PA was presented to the Center controller at 2049:03. The aircraft's data block remained on the Center controllers display until the radar controller forced it off at 2050:07. The Center controller did not notify the TRACON sector controller that he was receiving a MSAW alert as required by FAA directives. The TRACON's MSAW system generated two predicted altitude alerts on the accident airplane at 2050:46 and 2050:51. According to FAA MSAW documentation, two consecutive predicted alerts will initiate an MSAW warning to the controller working the affected aircraft. Collectively, these alerts would have caused a 5 second aural alert to the sector controller beginning at 2050:51, along with a flashing red "LA" in N304PA's data block from 2050:51 until about 2051:06. The aircraft then descended below radar coverage, the track went into coast status, and the alert terminated. The wreckage of N304PA was located on a ridgeline 200 yards south of the Julian VOR at 5,537 feet msl. No preimpact airplane mechanical anomalies were identified.
1.1 HISTORY OF FLIGHT On May 10, 2004, about 2051, Pacific daylight time, a Piper PA-44-180, N304PA, collided with mountainous terrain at Julian, California. The airplane was operated by Pan Am International Flight Academy under the provisions of 14 CFR Part 91. Both private pilots were fatally injured and the airplane was destroyed. Visual meteorological conditions prevailed and an instrument flight plan had been filed. The flight originated at Deer Valley, Arizona. The airplane was on an IFR flight from Phoenix Deer Valley Airport, Phoenix, Arizona, to McClellan-Palomar Airport, Carlsbad, California. The airplane took off from Deer Valley at 1932 Pdt and the cleared route of flight was; Gila Bend, V66, Imperial, V458, Julian, then direct to Palomar. N304PA was number four in a train of five company airplanes flying the same route. The time separation between each airplane was about 5 to 10 minutes. The airplane directly ahead of N304PA was N434PA. Review of Air Traffic Control communications and radar data shows that the flight crew of N304PA contacted the San Diego North Radar (SDNR) controller at 2043:48 Pdt, reporting level at 8,000. The SDNR controller instructed the pilot to fly heading 260 after Julian and intercept the (Palomar) localizer. The pilot read back the clearance. At 2045:47, the SDNR controller told the pilot of N434PA, another Piper Seminole ahead of N304PA and flying the same route, to descend to 6,000 feet. The pilot of N434PA acknowledged the clearance. At 2047:55, the SDNR controller transmitted, "Seminole four papa alpha descend and maintain five thousand two hundred." The pilot of N304PA responded, "Down to five thousand two hundred for three zero four papa alpha." According to information provided by the approach controller, this clearance was intended for N434PA. The controller did not recognize that the clearance had been acknowledged by N304PA rather than N434PA. At 2048:19, the pilot of N434PA transmitted, "…for four three four papa alpha?" (The beginning of the transmission was blocked by another transmission from the SDNR controller to an uninvolved aircraft.) The SDNR controller replied, "No. Duke six romeo tango heading one nine zero maintain eight thousand." At 2049:55, the pilot of N304PA reported that he had ATIS information Zulu at Palomar, and the SDNR controller responded, "Seminole three zero four papa alpha thank you very much." According to radar data, at that time N304PA was descending through about 6,600 feet. At 2050:27, the SDNR controller again cleared N434PA to descend and maintain 5,200 feet. The pilot read back the clearance, and the SDNR controller then transmitted, "Seminole four three four papa alpha is five miles from escon. Cross escon three thousand five hundred or above cleared ILS 24 at Palomar." The pilot of N434PA acknowledged. At 2052, the controller-in-charge (CIC) of the area including the SDNR sector received a call from San Diego automated flight service station (AFSS) reporting that they were receiving a strong emergency locater transmitter (ELT) signal in the area of the Julian VOR. The AFSS specialist asked the CIC to have controllers check with aircraft in the area in order to begin localizing the source. The CIC contacted the controllers at both the San Diego West and North sectors to attempt to locate the ELT signal. At 2053:23, the SDNR controller transmitted, "Seminole four papa alpha can you uh come up on one two one point five and check for an ELT please?" There was no response. The SDNR controller then made two more attempts to contact N304PA without success. He then transmitted, "Seminole four three four papa alpha how do you hear?" The pilot of N434PA replied, "four three four papa alpha five by five." The SDNR controller then instructed the pilot of N434PA to contact Palomar tower, and the pilot acknowledged. Between 2054:21 and 2055:36, the SDNR controller made five more unsuccessful attempts to contact N304PA. At 2058:34, the pilot of N6ZP asked, "SoCal six zulu papa just for my own heart did you get a hold of that Seminole?" The SDNR controller responded, "No uh we're checking right now uh I don't uh we don't know where it is right now uh last we saw of him he was just five southeast of Julian same route that you were four papa alpha." There was no further contact with N304PA. 1.5 PERSONNEL INFORMATION 1.5.1 Flightcrew The occupants consisted of two private pilots, both with recently acquired instrument and multi-engine ratings. The intension of the flight was to build flight experience. The normal practice at the academy was for one pilot to be pilot-in-command on the outbound leg and the other pilot to be the pilot-in-command on the return leg of the trip. A review of Federal Aviation Administration (FAA) airman records, Okalahoma City, Okalahoma, revealed the occupant-1 held a private pilot certificate issued on April 12, 2004, with ratings for single-engine land, multi-engine land, and instrument ratings for airplanes. Occupant-1 held a first-class medical certificate issued on July 10, 2003, with the restriction that he must wear corrective lenses. Occupant-2 held a private pilot certificate issued on April 30, 2004, with ratings for single-engine land, multi-engine land, and instrument ratings for airplanes. Occupant-2 held a first class medical certificate issued on November 18, 2003, with the limitation of wearing corrective lenses for distant vision. Occupant-1's flight logbook was not recovered or examined by the Safety Board investigator. Occupant-1's accumulated flight time was calculated from flight and training records provided by Pan Am International Flight Academy, which may not be all inclusive of his flight experience. The Pan Am International Flight Academy records revealed that the pilot had approximately 174.8 total hours of flight time with 21.6 hours of that in multi-engine aircraft. He had approximately 46.8 hours of simulated instrument time in an airplane and 12.2 hours of night flying. Examination of occupant-2's flight logbook revealed he had 239.8 hours of total flight time, 51.3 hours of multi-engine time, 50.4 hours of simulated instrument time in an airplane, and 37.2 hours of night flying. 1.5.2 ATC Controllers The Safety Board ATC Group Chairman conducted detailed controller interviews, which are described in the ATC Group Factual Report section in the Official Docket of this accident. The San Diego North Radar Controller was certified in this position in October 1975. The San Diego Area Controller-in-Charge was certified in this position in March 1992. The San Diego North Radar Handoff Controller was certified in this position in February 1999. The San Diego Area Supervisor West Radar Controller became supervisor in 1999 and is qualified in the North, West, and South Bay sectors. The Los Angeles Sector 9 Radar Controller has been certified in this position since January 2003. Los Angeles Area E Controller-in-Charge has been certified in this position since April 1989. 1.6 AIRCRAFT INFORMATION The airplane was a Piper PA-44-180, serial number 4496123, which was a twin engine, four seat, equipped aircraft. The airplane was powered by two Lycoming O-360 engines with Hartzell propellers. Examination of the engine and airframe maintenance logbooks revealed a total airframe and engine time of 2,467.8 hours when it underwent its last maintenance inspection on May 4, 2004. The airplanes maintenance was conducted under the direction of the Pan Am International Flight Academy's Progressive Inspection Program. The airplanes flight record log revealed that the airplane had accumulated 17 hours of hobbs time since May 4th. The airplanes flight record log that is kept with the airplane has entries for both occupants, with occupant-1 listed first with the "flight hobbs out" field entered as 3129.5, the "flight hobbs in" field blank, and the dispatch block initialed. The last entry, which was occupant-2, had all flight time and dispatch fields blank. The airplane discrepancy sheet in the airplane flight record log listed a discrepancy that was reported by the previous flight crew on 5/6/04 at a recorded "flight hobbs in" as 3129.5. This discrepancy was described as the right main landing gear light inoperative. Corrective maintenance action was recorded in the discrepancy log and flight record log. No other maintenance action or flight crews are listed between the last recorded flight on 5/6/04 and the accident flight entries. 1.7 METEOROLOGICAL INFORMATION The closest weather reporting station to the accident site was Ramona, California, which is located 18 miles to the northwest at an elevation of 1,390 feet. Ramona reported that at 2053 Pdt the winds were out of the south at four knots, visibility was 10 statute miles, the sky was overcast at 2,000 feet agl, the temperature was 15C, dew point 10C, and an altimeter setting of 29.87Hg. A remote Automated Weather Station (RAWS) was located 4 nautical miles south of the accident location. This stations elevation was 4,239 feet, and provided information about winds and relative humidity. The 2110 Pdt observation indicated winds were out of the west-southwest near 14 knots, gusting to 22 knots. The relative humidity was 100% (temperature and dew point were 9C). Astronomical calculations show that sunset occurred at 1942 Pdt. At 2051 the moon was on a true bearing from the accident location of 73.9 degrees and 60.2 degrees below the horizon. A detailed weather description can be found in the Meteorological Factual Report section in the Official Docket for this accident. 1.8 AIDS TO NAVIAGTATION 1.8.1 Information Available to the flight crew The published L-3 IFR En route Low Altitude chart used for instrument navigation depicts airway V458 feeding into the Julian (JLI) VOR on a 295 course (115 radial) and has a minimum en route altitude (MEA) of 7,700 feet. The published ILS RWY 24 instrument approach to McClellan-Palomar (CRQ) depicts the approach feeder radial 258 leaving the Julian (JLI) VOR with a corresponding minimum en route altitude (MEA) of 6,800 feet until the GENTA intersection. GENTA intersection is on the JLI 258 radial and 14.3 DME (distance measuring equipment). The depicted minimum safe altitude (MSA) for aircraft approaching the Oceanside VOR (OCN) from the east within a 25 nautical mile radius is 6,800 feet. The published RNAV (GPS) RWY 24 approach to McClellan-Palomar (CRQ) depicts a minimum safe altitude (MSA) of 7,400 feet for all quadrants around the airport. 1.8.2 ATC and Radar Information Until about 2043, N304PA was receiving IFR ATC service from ZLA sector 9, which controls all airspace above 7,000 feet southeast of Julian (JLI) along V458. The aircraft was therefore still in Los Angeles Center (ZLA) airspace when the descent from 8,000 feet began, although the pilot was in contact with the Southern California TRACON (SCT) San Diego North Radar (SDNR) controller. ZLA's radar data for this area is provided by an ARSR-4 radar system located on top of Mount Laguna, which is 18 miles southeast of the accident site at 6,200 feet elevation and provided excellent coverage of N304PA's flight path. According to recorded ZLA automation data, a Minimum Safe Altitude Warning (MSAW) alert on N304PA was presented to the ZLA sector 9 controller at 2049:03. The aircraft's data block remained on the ZLA sector 9 display until the radar controller forced it off at 2050:07. The Minimum Safe Altitude Warning (MSAW) alert was being presented to the controller throughout that period. The last altitude displayed to the ZLA 9 controller in a full data block was 6,800 feet, although the target would have continued to be displayed as a limited data block (with only a beacon code and altitude) for the remainder of the flight. The ZLA minimum IFR altitude for the area southeast of JLI is 8,000 feet. The San Diego North Radar sector uses an ASR-9 radar system located at MCAS Miramar, which is about 32 miles from the accident site. According to controller statements, it is not uncommon for the system to miss targets at 8,000 feet along the route followed by N304PA. However, recorded data shows that there were no missing targets for the last 5 minutes of the flight before the aircraft descended below 6,100 feet and went out of radar coverage. At the time of the accident, the SDNR radar controller and associate were also responsible for the Miramar and Del Mar sectors. According to controller statements this is a normal configuration for the late evening time period. The two San Diego area controllers characterized their workload as moderate. 1.8.3 Minimum Safe Altitude Warning System Operation (MSAWS) Los Angeles Center (ZLA) and Southern Californian TRACON (SCT) both are equipped with minimum safe altitude warning software designed to alert controllers when an aircraft is in danger of colliding with terrain or defined obstructions. As noted above, the two systems are not identical in performance. The en route and terminal systems use dissimilar terrain databases and different algorithms for predicting when an aircraft may come too close to the ground or to a man-made object such as an antenna. En route MSAW documentation is contained in FAA documents MD-316, "Adaptation," and MD-321, "Automatic Tracking." In the en route system, airspace is divided into three-dimensional polygons with a minimum alerting altitude assigned to each polygon in accordance with IFR terrain clearance requirements. In general, if an aircraft operating under instrument flight rules descends below the minimum altitude established for the polygon, a minimum safe altitude warning will be generated and the controller will be alerted. (There are special cases where alerts are intentionally suppressed, such as when an aircraft is known to be landing.) The ZLA minimum IFR altitude for the area along V458 southeast of JLI is 8,000 feet. When N304PA descended below 7,800 feet, the MSAW system activated and provided a visual alert to the sector 9 controller. The alert continued until N304PA struck the terrain, although recorded automation data shows that the controller dropped the data block from the display when the aircraft descended through 6,800 feet. ARTS IIIE MSAW documentation is contained in FAA documents MD-643, "Site Adaptation," and MD-644, "MSAW and Altitude Tracking." Terrain and obstacle data for ARTS IIIE is held in the form of a matrix consisting of two-nautical-mile square boxes, with a maximum terrain/obstacle elevation assigned to each box. The MSAW software monitors tracked aircraft with valid mode C and produces alerts based on both current and predicted terrain/obstacle clearance. If an aircraft is currently within 500 feet of the alerting altitude for the box it is in, or is predicted through extrapolation of current altitude and rate of descent to be within 300 feet of terrain or obstacles in 30 seconds, an aural and visual alert is generated to all controllers that are displaying the aircraft's full data block. At SCT, this alert consists of a five second beeping alert tone at the affected sector as well as a flashing red "LA" above the aircraft's data block that continues until the alert terminates. Alerts terminate when the aircraft's terrain clearance increases beyond MSAW alert parameters, no valid mode C altitude data is available from the aircraft, or when radar contact is lost. The minimum aural alarm volume level is restricted, and cannot be silenced by using the volume control. The SCT MSAW system generated two predicted alerts at 2050:46 and 2050:51. According to FAA MSAW documentation, two consecutive predicted alerts will initiate an MSAW warning to the controller working the affected aircraft. Collectively, these alerts would have caused a 5 second aural alert to the SDNR sector beginning at 2050:51, along with a flashing red "LA" in N304PA's data block from 2050:51 until about 2051:06. The aircraft then descended below radar coverage, the track went into coast status, and the alert terminated. More detail concerning the ATC Facility, Radar, and the MSAW system is located in the ATC Group Factual Report
The incorrect use of an abbreviated callsign by the TRACON sector radar controller to issue a descent clearance to N434PA and the sector controllers failure to detect that the clearance had been read back with the full callsign by the pilot of N304PA. Also causal was the pilots failure to question a clearance that descended them below the published Minimum En route Altitude (MEA). Contributing to the accident was the failure of both the Center and TRACON controllers to properly respond to the aural and visual Minimum Safe Altitude Warning System (MSAW) alert.
Source: NTSB Aviation Accident Database
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