Narrative:

The challenger was equipped with TCASII and did not have a TA. The MD80 apparently did have a TA. During a flight from oma to iah, the crew made a slight deviation from the runway 26 approach, which with runway 27 has simultaneous ILS approach authority/authorized. There was never a point during the approach that the aircraft exceeded the protected deviation area of the ILS approach. The narrow separation distance between the 2 approachs of 1 mi and the proximity of another aircraft on the runway 27 approach prompted a target alert on the other aircraft. But did not cause a target alert on the challenger. Sequence of events: the crew of the challenger was given a right turn to 260 degrees, cleared for approach and contact tower. The captain acknowledged the clearance as the copilot was engaged in other cockpit duties. The aircraft was on autoplt so the captain turned the heading bug to 260 degrees and engaged the approach mode on the flight director. At that point the captain was concerned because the assigned heading appeared to be too shallow to intercept the ILS course before the OM. The CDI indicator was showing full defection left. The heading would have been fine if the aircraft was on or almost on course. At this point the captain looked at the FMS extended centerline from the OM on the mfd which showed that the aircraft was on course for the ILS runway 26. The captain again checked the CDI and it was still full deflection left. At this time the captain said to the copilot, 'this is not right, the FMS does not agree with the ILS.' the copilot checked the approach chart and said, 'I gave you the frequency for runway 27.' he changed the captain's ILS frequency. The captain immediately turned the heading bug to 280 degrees so the aircraft would intercept the runway 26 localizer. At the same time, the captain saw a white DC9 at about 10 O'clock low and noted that it appeared to be starting a level left turn. The distance looked to be over 1 mi ahead and about 800-1000 ft lower. The challenger's altitude was about 3500 ft at the completion of the turn. The captain also noted that the GS indicator was centered and the CDI was 1/2 deflection to the right so he continued the approach for runway 26. Approach control came on the frequency and asked if we were on frequency. The copilot acknowledged the call. The controller said to level at 3000 ft which the captain did. The captain told the copilot to report seeing the other aircraft and that the airport was in sight. At this time the aircraft appeared to be slightly left of runway 26 centerline and the CDI was less than 1/2 deflection. The copilot acknowledged that the airport was in sight and told approach control which told the crew to contact tower. The copilot told the tower the airport was in sight, at which time the tower cleared the aircraft for a visual approach. Conclusion: the crew of the challenger erred in not putting the correct ILS frequency in the navigation radio, but were able to correct the mistake before they exceeded the limits of the ILS. The simultaneous ILS approach to iah for runway 27 and runway 26 are only 1 mi apart. The protected area of both ILS approachs outside the OM's cross into the other's protected boundary. Because of this, authority/authorized for simultaneous approach operations have special rules. Both aircraft will monitor the same frequency and if the ground controller detects a dangerous situation the order to break or discontinue the pilots of both aircraft are obligated to break off their approach and turn in appropriate direction. The left approach breaks left, the right breaks right. This monitoring should be on both approach frequency and tower. In this case the tower was the only common frequency. It would be prudent for airport controllers to make sure both aircraft are on the same approach frequency as well as the tower frequency. The chance that the 2 aircraft will have premature traffic alerts, as one of these aircraft had, is more likely when the aircraft are heading in opposite directions for a moment during their final turn inbound during the approach. It is much less chance of a false alert or a real conflict once both aircraft are on their inbound course. Another change in procedure would be to have informed both aircraft of the other before the approach begins. In this situation, neither aircraft was informed of the other. If a false traffic alert accrues and the crew can identify and verify the presence of the other visually, the TA can be just a warning and not a deviation. Supplemental information from acn 412031: the captain noticed that the localizer needle deflection and the runway 26 course centerline that was programmed into the sperry FMS did not agree. I immediately checked all the navigation frequencys and FMS set-up confirming the error was with the wrong ILS frequency set in. I had both runway 27 and runway 26 ILS frequencys preprogrammed.

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Original NASA ASRS Text

Title: CL60 HAD AN AIRSPACE INCURSION WITH AN MD80, FLYING PARALLEL SIMULTANEOUS APCHS TO RWY 26 AND RWY 27 AT IAH.

Narrative: THE CHALLENGER WAS EQUIPPED WITH TCASII AND DID NOT HAVE A TA. THE MD80 APPARENTLY DID HAVE A TA. DURING A FLT FROM OMA TO IAH, THE CREW MADE A SLIGHT DEV FROM THE RWY 26 APCH, WHICH WITH RWY 27 HAS SIMULTANEOUS ILS APCH AUTH. THERE WAS NEVER A POINT DURING THE APCH THAT THE ACFT EXCEEDED THE PROTECTED DEV AREA OF THE ILS APCH. THE NARROW SEPARATION DISTANCE BTWN THE 2 APCHS OF 1 MI AND THE PROX OF ANOTHER ACFT ON THE RWY 27 APCH PROMPTED A TARGET ALERT ON THE OTHER ACFT. BUT DID NOT CAUSE A TARGET ALERT ON THE CHALLENGER. SEQUENCE OF EVENTS: THE CREW OF THE CHALLENGER WAS GIVEN A R TURN TO 260 DEGS, CLRED FOR APCH AND CONTACT TWR. THE CAPT ACKNOWLEDGED THE CLRNC AS THE COPLT WAS ENGAGED IN OTHER COCKPIT DUTIES. THE ACFT WAS ON AUTOPLT SO THE CAPT TURNED THE HDG BUG TO 260 DEGS AND ENGAGED THE APCH MODE ON THE FLT DIRECTOR. AT THAT POINT THE CAPT WAS CONCERNED BECAUSE THE ASSIGNED HDG APPEARED TO BE TOO SHALLOW TO INTERCEPT THE ILS COURSE BEFORE THE OM. THE CDI INDICATOR WAS SHOWING FULL DEFECTION L. THE HDG WOULD HAVE BEEN FINE IF THE ACFT WAS ON OR ALMOST ON COURSE. AT THIS POINT THE CAPT LOOKED AT THE FMS EXTENDED CTRLINE FROM THE OM ON THE MFD WHICH SHOWED THAT THE ACFT WAS ON COURSE FOR THE ILS RWY 26. THE CAPT AGAIN CHKED THE CDI AND IT WAS STILL FULL DEFLECTION L. AT THIS TIME THE CAPT SAID TO THE COPLT, 'THIS IS NOT RIGHT, THE FMS DOES NOT AGREE WITH THE ILS.' THE COPLT CHKED THE APCH CHART AND SAID, 'I GAVE YOU THE FREQ FOR RWY 27.' HE CHANGED THE CAPT'S ILS FREQ. THE CAPT IMMEDIATELY TURNED THE HDG BUG TO 280 DEGS SO THE ACFT WOULD INTERCEPT THE RWY 26 LOC. AT THE SAME TIME, THE CAPT SAW A WHITE DC9 AT ABOUT 10 O'CLOCK LOW AND NOTED THAT IT APPEARED TO BE STARTING A LEVEL L TURN. THE DISTANCE LOOKED TO BE OVER 1 MI AHEAD AND ABOUT 800-1000 FT LOWER. THE CHALLENGER'S ALT WAS ABOUT 3500 FT AT THE COMPLETION OF THE TURN. THE CAPT ALSO NOTED THAT THE GS INDICATOR WAS CTRED AND THE CDI WAS 1/2 DEFLECTION TO THE R SO HE CONTINUED THE APCH FOR RWY 26. APCH CTL CAME ON THE FREQ AND ASKED IF WE WERE ON FREQ. THE COPLT ACKNOWLEDGED THE CALL. THE CTLR SAID TO LEVEL AT 3000 FT WHICH THE CAPT DID. THE CAPT TOLD THE COPLT TO RPT SEEING THE OTHER ACFT AND THAT THE ARPT WAS IN SIGHT. AT THIS TIME THE ACFT APPEARED TO BE SLIGHTLY L OF RWY 26 CTRLINE AND THE CDI WAS LESS THAN 1/2 DEFLECTION. THE COPLT ACKNOWLEDGED THAT THE ARPT WAS IN SIGHT AND TOLD APCH CTL WHICH TOLD THE CREW TO CONTACT TWR. THE COPLT TOLD THE TWR THE ARPT WAS IN SIGHT, AT WHICH TIME THE TWR CLRED THE ACFT FOR A VISUAL APCH. CONCLUSION: THE CREW OF THE CHALLENGER ERRED IN NOT PUTTING THE CORRECT ILS FREQ IN THE NAV RADIO, BUT WERE ABLE TO CORRECT THE MISTAKE BEFORE THEY EXCEEDED THE LIMITS OF THE ILS. THE SIMULTANEOUS ILS APCH TO IAH FOR RWY 27 AND RWY 26 ARE ONLY 1 MI APART. THE PROTECTED AREA OF BOTH ILS APCHS OUTSIDE THE OM'S CROSS INTO THE OTHER'S PROTECTED BOUNDARY. BECAUSE OF THIS, AUTH FOR SIMULTANEOUS APCH OPS HAVE SPECIAL RULES. BOTH ACFT WILL MONITOR THE SAME FREQ AND IF THE GND CTLR DETECTS A DANGEROUS SIT THE ORDER TO BREAK OR DISCONTINUE THE PLTS OF BOTH ACFT ARE OBLIGATED TO BREAK OFF THEIR APCH AND TURN IN APPROPRIATE DIRECTION. THE L APCH BREAKS L, THE R BREAKS R. THIS MONITORING SHOULD BE ON BOTH APCH FREQ AND TWR. IN THIS CASE THE TWR WAS THE ONLY COMMON FREQ. IT WOULD BE PRUDENT FOR ARPT CTLRS TO MAKE SURE BOTH ACFT ARE ON THE SAME APCH FREQ AS WELL AS THE TWR FREQ. THE CHANCE THAT THE 2 ACFT WILL HAVE PREMATURE TFC ALERTS, AS ONE OF THESE ACFT HAD, IS MORE LIKELY WHEN THE ACFT ARE HDG IN OPPOSITE DIRECTIONS FOR A MOMENT DURING THEIR FINAL TURN INBOUND DURING THE APCH. IT IS MUCH LESS CHANCE OF A FALSE ALERT OR A REAL CONFLICT ONCE BOTH ACFT ARE ON THEIR INBOUND COURSE. ANOTHER CHANGE IN PROC WOULD BE TO HAVE INFORMED BOTH ACFT OF THE OTHER BEFORE THE APCH BEGINS. IN THIS SIT, NEITHER ACFT WAS INFORMED OF THE OTHER. IF A FALSE TFC ALERT ACCRUES AND THE CREW CAN IDENT AND VERIFY THE PRESENCE OF THE OTHER VISUALLY, THE TA CAN BE JUST A WARNING AND NOT A DEV. SUPPLEMENTAL INFO FROM ACN 412031: THE CAPT NOTICED THAT THE LOC NEEDLE DEFLECTION AND THE RWY 26 COURSE CTRLINE THAT WAS PROGRAMMED INTO THE SPERRY FMS DID NOT AGREE. I IMMEDIATELY CHKED ALL THE NAV FREQS AND FMS SET-UP CONFIRMING THE ERROR WAS WITH THE WRONG ILS FREQ SET IN. I HAD BOTH RWY 27 AND RWY 26 ILS FREQS PREPROGRAMMED.

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.