Narrative:

There have been numerous pltdevs lately at ZLA caused by the software on certain inertial navigation system. Most of the deviations involve airbus aircraft. These aircraft have navigation system that limit the maximum angle of bank the aircraft can achieve during a turn for 'passenger comfort' concerns. On routes that change direction at fixes by amounts approaching 90 degrees, we have seen these aircraft turn as early as 15 mi prior to the fix where the change in direction occurs. This obviously can and has created dangerous separation sits for controllers. A recent example demonstrates that business jets have adopted this problematic software and natca needs to be the catalyst to correct this serious problem. I was assigned to the R20 position. Sector 20 is a small low altitude sector that handles high volumes of lax, ont, sna, lgb and other southern basin arrs, as well as overflts and psp arrs and departures. The sector was at moderate or greater complexity at the time. Aircraft X, a PC12/a was abeam L35 wbound direct pmd at FL200. Aircraft Y, a T/CL60/G departed psp and was climbing to FL210 via V386 to pmd en route to oak. Aircraft Y was climbing slowly and I elected to leave the aircraft on V386 to facilitate the climb above aircraft X. V386 makes a 70 degree left turn to soggi intersection where it then goes to pmd. Approximately 8 mi south of soggi, aircraft Y began a left turn to join V386 west of soggi intersection. This placed the aircraft into conflict with aircraft X. I informed aircraft Y that I needed his aircraft to fly directly over soggi due to traffic. The pilot responded stating that his navigation computer was turning the aircraft to join V386 on the west side of soggi. I turned aircraft Y 30 degrees to the right to avoid aircraft X and then suggested to the pilot that he place his navigation computer into the overflt mode, as I did not authority/authorized an early turn. The pilot complied with the turn and when his aircraft was level at FL210, I cleared aircraft Y direct pmd. There are many routes in ZLA where these types of deviations can create serious problems including a loss of separation. An additional example occurs when traffic management reroutes aircraft en route to lax via J6 hec J64. This involves a 50 degree left turn at hec. If aircraft make an early left turn to join J64 south of hec, they will infringe upon R2501. These types of maneuvers created by this navigation system are not compatible with recent NOTAMS and raise concerns about these system placing aircraft into or in proximity of restr or prohibited airspace. There are also areas of non-radar coverage in ZLA and times where radar outages create a non-radar control environment. FAA order 7110.65M, chapter 6, defines procedures for maintaining longitudinal and lateral separation of en route aircraft in a non-radar environment. These procedures require aircraft to overfly the fixes on their assigned routes. Navigation system that allow aircraft to turn early at fixes or intxns place the aircraft outside of the airspace protected with a non-radar environment and brings into question whether the system can be properly certified for use in NAS. , At the national level, should take immediate action to correct this problem. The software in these navigation system should be modified under an FAA directive to prevent these early turns. Controllers should be made aware of this situation and which aircraft are affected. Until the software is fixed, aircraft with these system should be required under NOTAMS to operate only in the 'overfly' mode. Pilots should be notified that they could be subject to pilot deviation actions if they do no comply with the NOTAM for overflt only mode. As this navigation system migrates into the business community fleet the chances for loss of separation or near midair collision's is going to increase exponentially. Corrective action needs to take place prior to a serious incident.

Google
 

Original NASA ASRS Text

Title: AN AIR TFC CTLR HAS CONCERNS ABOUT FLT MGMNT SYS THAT CALL FOR EARLY TURNS OVER AIRWAY FIXES RESULTING IN LOSS OF TFC SEPARATION AND RESTR AREA INCURSIONS. HE SIGHTS THE AIRBUS AS AN ONGOING OFFENDER AND NOTES BUSINESS JETS ARE ALSO BECOMING A PROB.

Narrative: THERE HAVE BEEN NUMEROUS PLTDEVS LATELY AT ZLA CAUSED BY THE SOFTWARE ON CERTAIN INERTIAL NAV SYS. MOST OF THE DEVS INVOLVE AIRBUS ACFT. THESE ACFT HAVE NAV SYS THAT LIMIT THE MAX ANGLE OF BANK THE ACFT CAN ACHIEVE DURING A TURN FOR 'PAX COMFORT' CONCERNS. ON ROUTES THAT CHANGE DIRECTION AT FIXES BY AMOUNTS APCHING 90 DEGS, WE HAVE SEEN THESE ACFT TURN AS EARLY AS 15 MI PRIOR TO THE FIX WHERE THE CHANGE IN DIRECTION OCCURS. THIS OBVIOUSLY CAN AND HAS CREATED DANGEROUS SEPARATION SITS FOR CTLRS. A RECENT EXAMPLE DEMONSTRATES THAT BUSINESS JETS HAVE ADOPTED THIS PROBLEMATIC SOFTWARE AND NATCA NEEDS TO BE THE CATALYST TO CORRECT THIS SERIOUS PROB. I WAS ASSIGNED TO THE R20 POS. SECTOR 20 IS A SMALL LOW ALT SECTOR THAT HANDLES HIGH VOLUMES OF LAX, ONT, SNA, LGB AND OTHER SOUTHERN BASIN ARRS, AS WELL AS OVERFLTS AND PSP ARRS AND DEPS. THE SECTOR WAS AT MODERATE OR GREATER COMPLEXITY AT THE TIME. ACFT X, A PC12/A WAS ABEAM L35 WBOUND DIRECT PMD AT FL200. ACFT Y, A T/CL60/G DEPARTED PSP AND WAS CLBING TO FL210 VIA V386 TO PMD ENRTE TO OAK. ACFT Y WAS CLBING SLOWLY AND I ELECTED TO LEAVE THE ACFT ON V386 TO FACILITATE THE CLB ABOVE ACFT X. V386 MAKES A 70 DEG L TURN TO SOGGI INTXN WHERE IT THEN GOES TO PMD. APPROX 8 MI S OF SOGGI, ACFT Y BEGAN A L TURN TO JOIN V386 W OF SOGGI INTXN. THIS PLACED THE ACFT INTO CONFLICT WITH ACFT X. I INFORMED ACFT Y THAT I NEEDED HIS ACFT TO FLY DIRECTLY OVER SOGGI DUE TO TFC. THE PLT RESPONDED STATING THAT HIS NAV COMPUTER WAS TURNING THE ACFT TO JOIN V386 ON THE W SIDE OF SOGGI. I TURNED ACFT Y 30 DEGS TO THE R TO AVOID ACFT X AND THEN SUGGESTED TO THE PLT THAT HE PLACE HIS NAV COMPUTER INTO THE OVERFLT MODE, AS I DID NOT AUTH AN EARLY TURN. THE PLT COMPLIED WITH THE TURN AND WHEN HIS ACFT WAS LEVEL AT FL210, I CLRED ACFT Y DIRECT PMD. THERE ARE MANY ROUTES IN ZLA WHERE THESE TYPES OF DEVS CAN CREATE SERIOUS PROBS INCLUDING A LOSS OF SEPARATION. AN ADDITIONAL EXAMPLE OCCURS WHEN TFC MGMNT REROUTES ACFT ENRTE TO LAX VIA J6 HEC J64. THIS INVOLVES A 50 DEG L TURN AT HEC. IF ACFT MAKE AN EARLY L TURN TO JOIN J64 S OF HEC, THEY WILL INFRINGE UPON R2501. THESE TYPES OF MANEUVERS CREATED BY THIS NAV SYS ARE NOT COMPATIBLE WITH RECENT NOTAMS AND RAISE CONCERNS ABOUT THESE SYS PLACING ACFT INTO OR IN PROX OF RESTR OR PROHIBITED AIRSPACE. THERE ARE ALSO AREAS OF NON-RADAR COVERAGE IN ZLA AND TIMES WHERE RADAR OUTAGES CREATE A NON-RADAR CTL ENVIRONMENT. FAA ORDER 7110.65M, CHAPTER 6, DEFINES PROCS FOR MAINTAINING LONGITUDINAL AND LATERAL SEPARATION OF ENRTE ACFT IN A NON-RADAR ENVIRONMENT. THESE PROCS REQUIRE ACFT TO OVERFLY THE FIXES ON THEIR ASSIGNED ROUTES. NAV SYS THAT ALLOW ACFT TO TURN EARLY AT FIXES OR INTXNS PLACE THE ACFT OUTSIDE OF THE AIRSPACE PROTECTED WITH A NON-RADAR ENVIRONMENT AND BRINGS INTO QUESTION WHETHER THE SYS CAN BE PROPERLY CERTIFIED FOR USE IN NAS. , AT THE NATIONAL LEVEL, SHOULD TAKE IMMEDIATE ACTION TO CORRECT THIS PROB. THE SOFTWARE IN THESE NAV SYS SHOULD BE MODIFIED UNDER AN FAA DIRECTIVE TO PREVENT THESE EARLY TURNS. CTLRS SHOULD BE MADE AWARE OF THIS SIT AND WHICH ACFT ARE AFFECTED. UNTIL THE SOFTWARE IS FIXED, ACFT WITH THESE SYS SHOULD BE REQUIRED UNDER NOTAMS TO OPERATE ONLY IN THE 'OVERFLY' MODE. PLTS SHOULD BE NOTIFIED THAT THEY COULD BE SUBJECT TO PLTDEV ACTIONS IF THEY DO NO COMPLY WITH THE NOTAM FOR OVERFLT ONLY MODE. AS THIS NAV SYS MIGRATES INTO THE BUSINESS COMMUNITY FLEET THE CHANCES FOR LOSS OF SEPARATION OR NMAC'S IS GOING TO INCREASE EXPONENTIALLY. CORRECTIVE ACTION NEEDS TO TAKE PLACE PRIOR TO A SERIOUS INCIDENT.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.