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Safety Recommendation Details

Safety Recommendation A-87-098
Details
Synopsis: THE NATIONAL TRANSPORTATION SAFETY BOARD HAS COMPLETED ITS INVESTIGATION AND REPORT OF THE MIDAIR COLLISION BETWEEN AERONAVES DE MEXICO (AEROMEXICO) FLIGHT 498, A DC-9-32, AND A GENERAL AVIATION PIPER PA-28-181, WHICH OCCURRED OVER CERRITOS, CALIFORNIA, ON AUGUST 31, 1986. AEROMEXICO FLIGHT 498 WAS OPERATING UNDER INSTRUMENT FLIGHT RULES (IFR) DESTINED FOR THE LOS ANGELES INTERNATIONAL AIRPORT ON A SCHEDULED PASSENGER FLIGHT FROM TIJUANA, MEXICO. THE PA-28 WAS CLIMBING UNDER VISUAL FLIGHT RULES (VFR) AFTER DEPARTURE FROM TORRANCE, CALIFORNIA. THE COLLISION OCCURRED ABOUT 8 MILES BEYOND THE POINT AT WHICH FLIGHT 498 CROSSED THE BOUNDARY OF THE LOS ANGELES TERMINAL CONTROL AREA (TCA) NEAR 6,500 FEET MEAN SEA LEVEL. BOTH AIRPLANES FELL TO THE GROUND WITHIN THE CITY LIMITS OF CERRITOS. FIVE HOUSES WERE DESTROYED AND SEVEN OTHER HOUSES WERE DAMAGED BY AIRPLANE WRECKAGE AND POSTIMPACT FIRE. FIFTY-EIGHT PASSENGERS AND 6 CREWMEMBERS ON THE DC-9, THE PILOT AND 2 PASSENGERS ON THE PA-28, AND 15 PEOPLE ON THE GROUND WERE KILLED IN THE ACCIDENT.
Recommendation: THE NTSB RECOMMENDS THAT THE FEDERAL AVIATION ADMINISTRATION: TAKE EXPEDITED ACTION TO ADD VISUAL FLIGHT RULES CONFLICT ALERT (MODE C INTRUDER) LOGIC TO AUTOMATED RADAR TERMINAL SYSTEM (ARTS) COMPUTERS AS AN INTERIM MEASURE TO THE ULTIMATE IMPLEMENTATION OF THE ADVANCED AUTOMATION SYSTEM (AAS).
Original recommendation transmittal letter: PDF
Overall Status: Closed - Acceptable Alternate Action
Mode: Aviation
Location: CERRITOS, CA, United States
Is Reiterated: No
Is Hazmat: No
Is NPRM: No
Accident #: DCA86AA041AB
Accident Reports: Collision of Aeronaves De Mexico, S.A. McDonnell Douglas DC-9-32, XA-JED and Piper PA-28-181, N4891F
Report #: AAR-87-07
Accident Date: 8/31/1986
Issue Date: 7/27/1987
Date Closed: 9/14/2000
Addressee(s) and Addressee Status: FAA (Closed - Acceptable Alternate Action)
Keyword(s):

Safety Recommendation History
From: NTSB
To: FAA
Date: 9/14/2000
Response: THE SAFETY BOARD NOTES THAT ALTHOUGH RECOMMENDATION A-87-98 ASKED THE FAA TO TAKE EXPEDITED ACTION, THE COMPLEXITY OF THIS TOPIC, COUPLED WITH OTHER COMPLEX AIR TRAFFIC CONTROL IMPROVEMENTS, MADE EXPEDITED ACTION IMPRACTICAL. THE BOARD ALSO NOTES THAT ALTHOUGH AN INTERIM MEASURE WAS RECOMMENDED, THE ARTS IIIA AND ARTS IIE SYSTEMS ARE FINISHED PRODUCTS. THE ALTERNATIVES THAT THE FAA HAS COMPLETED FULLY SATISFY THIS RECOMMENDATION. ACCORDINGLY, A-87-98 IS CLASSIFIED "CLOSED--ACCEPTABLE ALTERNATE ACTION."

From: FAA
To: NTSB
Date: 7/21/2000
Response: Letter Mail Controlled 07/26/2000 3:02:42 PM MC# 2000953 AS PREVIOUSLY STATED, ALL 62 AUTOMATED RADAR TERMINAL SYSTEM (ARTS) IIIA FACILITIES ARE OPERATIONAL WITH MODE C INTRUDER LOGIC IN THE SOFTWARE. THE FAA CONSIDERED ITS ACTION TO BE COMPLETED WITH THE INSTALLATION OF THIS SOFTWARE. HOWEVER, ON 10/27/98, THE BOARD CLASSIFIED THIS SAFETY RECOMMENDATION IN AN "OPEN ACCEPTABLE ALTERNATE" STATUS PENDING COMPLETION OF THE ARTS IIE SYSTEM. THIS LETTER INFORMS THE BOARD THAT ALL 134 ARTS IIE SITES ARE NOW OPERATIONAL WITH MODE C INTRUDER LOGIC. THE FINAL SITE, HUNTINGTON, WV, BECAME OPERATIONAL ON 5/22/00. I BELIEVE THAT THE FAA HAS ADDRESSED THE FULL INTENT OF THIS SAFETY RECOMMENDATION, AND I CONSIDER THE FAA'S ACTION TO BE COMPLETED.

From: NTSB
To: FAA
Date: 10/27/1998
Response: A-87-98 ASKED THE FAA TO TAKE EXPEDITED ACTION TO ADD VISUAL FLIGHT RULES CONFLICT ALERT (MODE C INTRUDER) LOGIC TO AUTOMATED RADAR TERMINAL SYSTEM (ARTS) COMPUTERS AS AN INTERIM MEASURE TO THE ULTIMATE IMPLEMENTATION OF THE ADVANCED AUTOMATION SYSTEM (AAS). PENDING COMPLETION OF THE ARTS IIE SYSTEM IN THE YEAR 2000, A-87-98 IS CLASSIFIED "OPEN--ACCEPTABLE ALTERNATE RESPONSE."

From: FAA
To: NTSB
Date: 5/6/1998
Response: (Letter Mail Controlled 5/11/98 3:12:35 PM MC# 980604) ALL 62 AUTOMATED RADAR TERMINAL SYSTEM (ARTS) IIIA FACILITIES ARE OPERATIONAL WITH MODE C INTRUDER LOGIC IN THE SOFTWARE. THE FAA DETERMINED THAT THE ARTS IIA SITES REQUIRED ADDITIONAL HARDWARE, & SOFTWARE, TO PROCESS MODE C INTRUDER LOGIC. THIS IS BEING ACCOMPLISHED THROUGH IMPLEMENTATION OF THE COMMON ARTS SYSTEM (ARTS IIE) WHICH WILL HAVE THE MEMORY CAPABILITY & HARDWARE IMPROVEMENTS REQUIRED TO IMPLEMENT MODE C INTRUDER LOGIC AT THE 132 ARTS II FACILITIES. IMPLEMENTATION OF THE ARTS IIE PROGRAM FOR MODE C INTRUDER BEGAN 4/17/98, AT ROSWELL, NEW MEXICO. IT IS ANTICIPATED THAT ALL ARTS IIE SITES WILL OPERATIONAL BY 2000.

From: FAA
To: NTSB
Date: 4/30/1997
Response: All 62 Automated Radar Terminal System (ARTS) IIIA facilities are using Mode C Intruder logic in the software (version A3.06). The last ARTS IIIA facility (Tampa, Florida) became operational on February 24, 1997. During the program design and review phases, the Federal Aviation Administration (FAA) determined that the ARTS IIA sites required additional hardware and software to process Mode C Intruder logic. This is being accomplished through implementation of the common ARTS system (ARTS IIE) which will have the memory capability and hardware improvements required to implement Mode C Intruder logic at the 132 ARTS II facilities. The ARTS II program for Mode C Intruder (version A2.09) is scheduled for key site testing in June 1997, with implementation beginning in September 1997. However, I must emphasize that these dates are the FAA's target dates and may change as a result of budget or resource priorities. The FAA will review the ARTS IIE Mode C Intruder implementation plan after key site testing to determine what steps can be taken to expedite the installation schedule.

From: NTSB
To: FAA
Date: 3/6/1997
Response: AT ITS DECEMBER 1995 MEETING WITH THE FAA CONCERNING THIS & SAFETY ISSUES, THE BOARD ACKNOWLEDGED THE FAA'S PROGRESS IN THE ARTS-IIIA PORTION OF THE MODE C INTRUDER PROGRAM & THE FACT THAT VIRTUALLY ALL SUCH SITES ARE NOW OPERATIONAL. HOWEVER, THE DIALOGUE ON THIS RECOMMENDATION HAS BEEN ONGOING SINCE 1987. PROGRAM TRAGET DATES HAVE SLIPPED &, AS IS EVIDENCED BY YOUR MOST RECENT LETTER, MAY CONTINUE TO DO SO IN THE FUTURE. THE MODE C INTRUDER PROGRAM INVOLVES 194 ARTS FACILITIES, OF WHICH 62 ARE NOW OPERATIONAL. THEREFORE, ABOUT 31 PERCENT OF THE TOTAL PROGRAM HAS BEEN ACHIEVED OVER A 10-YEAR PERIOD. THE PROGRESS OF THIS PROGRAM, PARTICULARLY THAT OF THE ARTS IIE UPGRADE PORTION, DOES NOT DEMONSTRATE TO THE BOARD THAT AN APPROPRIATE LEVEL OF URGENCY OR ATTENTION HAS BEEN PROVIDED TO THIS PROGRAM. GIVEN THE CORRESPONDENCE & YEARS THAT IT HAS TAKEN TO REACH THIS POINT, THE BOARD IS CONCERNED THAT THE DELAY OF THIS PROGRAM WILL CONTINUE. AS YOU KNOW, THE BOARD BELIEVES THAT THE IMPLEMENTATION OF THIS RECOMMENDATION WOULD GREATLY IMPROVE TRANSPORTATION SAFETY. IT IS TO THAT END THAT THE MODE C INTRUDER PROGRAM WAS ADDED TO THE BOARD'S "MOST WANTED LIST" WHEN THE LIST WAS ADOPTED BY THE BOARD IN 1990. THE BOARD WILL CONTINUE TO URGE, THROUGH CONGRESSIONAL TESTIMONY, THAT FAA BUDGETARY CONSRAINTS NOT DELAY THE COMPLETION OF THIS PROGRAM. THEREFORE, THE BOARD CONTINUES TO CLASSIFY A-87-98 "OPEN--UNACCEPTABLE ACTION," PENDING A FIRM INDICATION BY THE FAA THAT THIS PROJECT WILL RECEIVE MORE EXPEDITIOUS TREATMENT.

From: FAA
To: NTSB
Date: 11/8/1996
Response: THE FAA NOTES THAT DURING A DECEMBER 1995 MEETING OF THE MOST WANTED SAFETY ISSUES, IT WAS INDICATED THAT THE FAA'S ACTION ON THIS RECOMMENDATION WAS ACCEPTABLE. THEY ARE DISAPPOINTED THAT ON JUNE 24, 1996, THE RECOMMENDATION WAS RECLASSIFIED FROM OPEN ACCEPTABLE TO OPEN UNACCEPTABLE. THEY GO ON TO SAY THAT THEY HAVE 61 OF 62 ARTS IIIA SITES OPERATIONAL (IF TAMPA BECAME OPERATIONAL IN NOVEMBER 1996) ALL SITES ARE OPERATIONAL. HOWEVER, THERE ARE 132 ARTS IIA SITES FOR WHICH KEY SITE TESTING DOES NOT BEGIN UNTIL JUNE 1997, WITH IMPLEMENTATION EXPECTED TO BEGINDURING SEPTEMBER 1997. THEY ADVISE THESE TARGET DATES MAY NOT BE MET AS A RESULT OF BUDGET OR RESOURCE PRIORITIES.

From: NTSB
To: FAA
Date: 6/24/1996
Response: THE BOARD NOTES THAT TO DATE, 56 ARTS IIIA FACILITIES ARE ONLINE & OPERATIONAL WITH THE MODE C INTRUDER PROGRAM (VERSION A3.06). FIVE OF THE REMAINING SIX ARTS IIIA SITES ARE SCHEDULED TO BE OPERATIONAL BY APRIL 1996 & THE LAST SITE BY SEPTEMBER 1996. THE BOARD IS DISAPPOINTED WITH FAA'S RESPONSE TO THIS SAFETY RECOMMENDATION. IN A RESPONSE LETTER DATED 3/3/95, THE FAA STATED THAT 21 ARTS IIIA FACILITIES WERE ONLINE & OPERATIONAL WITH THE MODE C INTRUDER PROGRAM (VERSION A3-06) & THAT THE REMAINING 41 ARTS IIIA SITES WERE SCHEDULED TO BE OPERATIONAL BY THE END OF SEPTEMBER 1995. THE FAA HAD ALSO INFORMED THE BOARD THAT KEY SITE TESTING FOR THE ARTS IIA PROGRAM WOULD BEGIN IN SEPTEMBER 1996 & THAT THE EFFORT WOULD LIKELY BE COMPLETED BY THE END OF MARCH 1997. AS STATED IN OUR LETTER OF 6/23/95, THIS RECOMMENDATION IS ON THE BOARD'S MOST WANTED LIST. THE BOARD WOULD APPRECIATE AN EXPLANATION OF THE DIFFICULTIES THAT ARE BEING ENCOUNTERED WITH THIS IMPORTANT PROGRAM. WE REQUEST INFO EXPLANING THE REASONS FOR THESE DELAYS & THE PRIORITY THAT THIS PROGRAM IS RECEIVING. PENDING RECEIPT OF THIS INFO, THE BOARD CLASSIFIES A-87-98 "OPEN--UNACCEPTABLE RESPONSE."

From: FAA
To: NTSB
Date: 2/21/1996
Response: FAA'S LETTER OF 2/21/96, INDICATES THAT 556 ARTS IIIA FACILITIES ARE ON LINE & OPERATIONAL WITH THE MODE C INTRUDER PROGRAM (VERSION A3.06). FIVE OF THE REMAINING SIX ARTS IIIA SITES ARE SCHEDULED TO BE OPERATIONAL BY APRIL 1996 & THE LAST SITE BY SEPTEMBER 1996. THE ARTS IIA PROGRAM FOR MCI (VERSION A2.09) IS SCHEDULED FOR KEY SITE TESTING IN APRIL 1997 WITH IMPLEMENTATION BEGINNING IN JULY 1997. AFTER KEY SITE TESTING, THE FAA WILL REVIEW THE ARTS IIA MCI IMPLEMENTATION PLAN TO DETERMINE WHAT STEPS CAN BE TAKEN TO EXPEDITE THE INSTALLATION SCHEDULE FOR THE 132 ARTS IIA FACILITIES.

From: NTSB
To: FAA
Date: 6/23/1995
Response: THE BOARD NOTES THAT, TO DATE, 21 ARTS IIIA FACILITIES ARE ON LINE & OPERATIONAL WITH THE MODE C INTRUDER PROGRAM (VERSION A3.6) & THE REMAINING 41 ARTS IIIA SITES ARE SCHEDULED TO BE OPERATIONAL BY THE END OF SEPTEMBER 1995. ALSO, THE FAA STILL HAS THE ARTS IIA PROGRAM UNDER DEVELOPMENT, WITH KEY SITE TESTING SCHEDULED FOR JUNE 1996 & IMPLEMENTATION BEGINNING IN SEPTEMBER 1996. THE FAA ANTICIPATES THAT THIS EFFORT SHOULD BE COMPLETED BY THE END OF MARCH 1997. AS YOU KNOW, THIS RECOMMENDTION IS ON THE BOARD'S "MOST WANTED" LIST, & ALTHOUGH THE FAA IS MAKING PROGRESS TOWARD MEETING THE INTENT OF THIS RECOMMENDATION, THE BOARD EXPECTED ACTION TO BE TAKEN IN A MORE EXPEDITIOUS TIMEFRAME. NONETHELESS, THE BOARD CONTINUES TO HOLD A-87-98 IN AN "OPEN--ACCEPTABLE RESPONSE" STATUS.

From: FAA
To: NTSB
Date: 4/3/1995
Response: To date, 21 Automated Radar Terminal Systems (ARTS) IIIA facilities are on line and operational with the Mode C Intruder program (version A3.06). For the remaining 41 ARTS IIIA sites, 5 are scheduled to be operational by March, 35 by June, and 1 by the end of September 1995. The ARTS IIA program for Mode C Intruder (version A2.09) is still under development and is scheduled for key site testing in June 1996 with implementation beginning in September 1996. It is anticipated that this effort should be completed by the end of March 1997. I will keep the Board apprised of the FAA's progress on this safety recommendation.

From: NTSB
To: FAA
Date: 2/16/1994
Response: THE BOARD NOTES THAT THE FAA SCHEDULED THE ARTS IIIA A3.06 SOFTWARE VERSION, WHICH INCLUDES MODE C INTRUDER FUNCTIONALITY, FOR KEY SITE TESTING IN DECMEBER 1993, WITH DELIVERY TO FIELD SITES COMMENCING IN JANUARY 1994. THE COMPLETION OF INSTALLATION AND COMMISSIONING AT THE 63 ARTS IIIA SITES IS SCHEDULED FOR THE END OF 1995. FURTHERMORE, THE FAA HAS SCHEDULED THE DELIVERY MODE C INTRUDER FOR ARTS IIA SITES FOR NOVEMBER 1995 WITH AN EXPECTED IMPLEMTATION DATE OF LATE 1996. AS YOU KNOW, THIS RECOMMENDATION IS ON THE BOARD'S "MOST WANTED" LIST, AND ALTHOUGH THE FAA IS MAKING PROGRESS TOWARD MEETING THE INTENT OF THIS RECOMMENDATION, THE BOARD EXPECTED ACTION TO BE TAKEN IN A MORE EXPEDIENT TIMEFRAME. NONETHELESS, THE BOARD CONTINUES TO HOLD RECOMMENDATION A-87-98 IN AN "OPEN--ACCEPTABLE RESPONSE" STATUS.

From: FAA
To: NTSB
Date: 12/6/1993
Response: THE FAA IS CONTINUING ITS EFFORTS TO INSTALL THE MODE C INTRUDER CONFLICT ALERT LOGIC. THE NEW YORK TERMINAL SYSTEM (ARTS) IIIE SITE, IS OPERATIONAL WITH MODE C INTRUDER. THE ARTS IIIA A3.06 SOFTWARE VERSION, WHICH INCLUDES MODE C INTRUDER FUNCTIONALITY, IS SCHEDULED FOR KEY SITE TESTING IN DECEMBER 1993 WITH DELIVERY TO FIELD SITES COMMENCING IN JANUARY 1994. THE SCHEDULED COMPLETION ON INSTALLATION AND COMMISSIONING AT THE 63 ARTS IIIA SITES IS THE END OF 1995. DELIVERY OF MODE C INTRUDER FOR ARTS IIA IS SCHEDULED FOR NOVEMBER 1995 WITH AN EXPECTED IMPLEMENTATION DATE OF LATE 1996.

From: NTSB
To: FAA
Date: 3/24/1992
Response: Thank you for your January 6, 1992, letter in further response to the National Transportation Safety Board's Safety Recommendation A-87-98. This recommendation stemmed from our investigation of a midair collision between Aeronaves de Mexico flight 498, a DC-9-32, and a Piper PA-28-181 over Cerritos, California, on August 31, 1986. We asked the FAA to expedite action to add visual flight rules conflict alert (mode C intruder) logic to Automated Radar Terminal System (ARTS) computers as an interim measure to the ultimate implementation of the Advanced Automation System (AAS). We note that the Mode C Intruder conflict alert logic was operational at the New York Terminal Radar Approach Control on July 3, 1991, and the remaining ARTS 111A sites will be operational by late 1995. We appreciate being kept informed of the progress of this safety recommendation, which remains classified as "Open-- Acceptable Response."

From: FAA
To: NTSB
Date: 1/6/1992
Response: THE FAA IS CONTINUING ITS EFFORTS TO INSTALL THE MODE C INTRUDER CONFLICT ALERT LOGIC. THE FIRST OPERATIONAL SITE AT THE NEW YORK TRACON WAS OPERATIONAL 7/3/91. IT IS ANTICIPATED THAT ALL OF THE REMAINING ARTS IIIA SITES WILL BE OPERATIONAL BY LATE 1995.

From: NTSB
To: FAA
Date: 10/21/1988
Response: Thank you for your letter in further response to the National Transportation Safety Board's Safety Recommendation A-87-98 regarding action to add visual flight rules conflict alert (mode C intruder) logic to Automated Radar Terminal System (ARTS) computers as an interim measure to the ultimate implementation of the Advanced Automation System. The Safety Board commends the FAA for its decision to incorporate collision avoidance software in the ARTS IIIA computers. This is a major step forward in the prevention of midair collisions. Safety Recommendation A-87-98 is being maintained in an "Open--Acceptable Action" status pending system installation.

From: FAA
To: NTSB
Date: 8/26/1988
Response: THE FAA HAS COMPLETED ITS STUDY AND HAS DETERMINED TO ADD THE VISUAL FLIGHT RULES CONFLICT ALERT (MODE C INTRUDER) SOFTWARE TO THE AUTOMATED RADAR TERMINAL SYSTEM (ARTS) IIIA COMPUTERS. THE FAA EXPECTS CONTRACT AWARD TO UNISYS IN THE 4TH FISCAL 1989 QUARTER, INCLUDING PURCHASE OF NEW COMPUTER ELEMENTS AND SOFTWARE FOR ALL ARTS IIIA SITES. INSTALLATION IS PLANNED FOR THE FAA TECHNICAL CENTER IN THE 2ND QUARTER OF FY 1991, AND FIRST SITE INSTALLATION IS PLANNED FOR 3RD QUARTER FY 1991 WITH OPERATIONAL READINESS IN THE NEXT QUARTER. ALL ARTS IIIA SITES SHOULD BE OPERATIONAL BY 2ND QUARTER FY 1993. THE PROJECT IS IN THE 1988 NATIONAL AIRSPACE SYSTEM PLAN AS PROJECT 8-22 AND IS ESTIMATED TO COST $91 MILLION. I BELIEVE THAT THIS MEETS THE INTENT OF THIS SAFETY RECOMMENDATION.

From: NTSB
To: FAA
Date: 4/22/1988
Response: In our letter of March 17, 1988, we expressed concern that delays in adding visual flight rules conflict alert Mode C intruder logic to the Automated Radar Terminal System (ARTS) IIIA until the Advanced Automation System (AAS) was implemented could take many years thereby accepting too great a risk. We are, therefore, pleased to learn of the FAA's 30-day study regarding the technical and operational problems that must be overcome in order to add the Mode C intruder software to ARTS IIIA as an intermediate measure to the ultimate implementation of the AAS. Pending receipt of the results of the FAA's study, this recommendation remains classified as "Open-- Acceptable Action."

From: NTSB
To: FAA
Date: 3/17/1988
Response: The facts and circumstances of this accident demonstrated the necessity of providing both controllers and pilots with automated warning systems that can assist them in avoiding midair collisions. These systems should alert a controller of an impending traffic conflict and the pilots' system should alert them to the presence and location of any aircraft that poses a collision threat. We, therefore, believe that waiting to add visual flight rules conflict alert Mode C intruder logic to the Automated Radar Terminal System (ARTS) IIIA until the Advanced Automation System (AAS) is implemented, which may take 10 years or more, is accepting too great a risk. On November 4, 1987, the FAA/NTSB staff met to discuss the resolution of this recommendation. It is our understanding that the FAA will further address this recommendation informing us that they will complete a feasibility study to determine which ARTS IIIA facilities have sufficient computer processing capability to permit implementation of the VFR mode C conflict alert routine. The FAA staff also stated that they would provide details concerning the agency's Interim Support Plan including its purpose, critical issues and problems, and the recommended solutions and schedules for implementation. Based on the information to be further provided by the FAA, this recommendation is classified as "Open--Acceptable Action."

From: FAA
To: NTSB
Date: 3/11/1988
Response: The recent rulemaking activities and procedural changes initiated by the FAA place additional requirements for Mode C transponders within the airspace system. As a result, I have ordered an immediate review of the agency's position with respect to the addition of visual flight rules (VFR) conflict alert (Mode C intruder) logic to Automated Radar Terminal Systems (ARTS) computers. This review includes an intensive 30-day study to determine the technical and operational factors that must be resolved in order to add the Mode C intruder software to ARTS IIIA systems as an intermediate measure to the ultimate implementation of the Advanced Automation System (AAS). The relevant factors to be evaluated in this study include: o Additional computer capacity requirements that would be imposed by adding VFR conflict alert logic to ARTS IIIA sites. o The technical and economic feasibility and time required to start up a production line to obtain additional input-output processors (IOP) that would be needed to increase computer capacity at ARTS IIIA sites. o The additional costs and time for development of Mode C intruder software. o The full cost of development and installation of the complete Mode C intruder packages at ARTS IIIA sites and the time required to implement the program. I will keep the Safety Board apprised of the FAA's progress on this safety recommendation.

From: FAA
To: NTSB
Date: 10/19/1987
Response: VFR CONFLICT ALERT (MODE C INTRUDER) LOGIC CANNOT BE ADDED TO THE AUTOMATED RADAR TERMINAL SYSTEM (ARTS) IIIA UNTIL THE ADVANCED AUTOMATION SYSTEM (AAS) IS IMPLEMENTED. THE ARTS IIIA IS OPERATING AT MAXIMUM TIMING AND CAPACITY AND CANNOT, IN ITS PRESENT CONFIGURATION, ACCOMMODATE ADDITIONAL ENHANCEMENTS WITHOUT STATE-OF-THE-ART EQUIPMENT TO INCREASE BOTH TIMING AND CAPACITY. THEREFORE, ADDITIONAL ENHANCEMENTS CANNOT BE ADDED UNTIL THE IMPLEMENTATION OF THE AAS.

From: NTSB
To: FAA
Date:
Response: At the 1990 Board meeting addressing the NTSB’s Most Wanted List of Transportation Safety Improvements (MWL), the Board voted to place Safety Recommendation A-87-98 on the Federal MWL under the issue category “Mode C Intruder Alerts in Terminal Areas.” On May 5, 1998 at the Board meeting addressing the NTSB's Most Wanted List of Transportation Safety Improvements, the Board voted to remove Safety Recommendation A-87-98 from the MWL. Its category, "Mode C Intruder Alerts in Terminal Areas" was removed from the MWL at that time.