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37000 Feet | Browse and search NASA's Aviation Safety Reporting System |
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The flight crew of a B747-400 flying over the north pacific notice an aircraft flying below them on their TCASII display at FL310. The lower aircraft starts to climb and the flight crew assumes they are going to FL330, however, the lower aircraft climbs through FL330 and starts into FL350. Reporter takes evasive action, but never receives a TCASII RA. As the other aircraft approachs FL350, he evidently sees reporter's aircraft and descends to FL330 immediately.
| Attributes | |
| ACN | 373144 |
| Time | |
| Date | 199706 |
| Day | Sat |
| Local Time Of Day | 1201 To 1800 |
| Place | |
| Locale Reference | atc facility : rjtg |
| State Reference | FO |
| Altitude | msl bound lower : 35000 msl bound upper : 35600 |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | artcc : rjtg |
| Operator | common carrier : air carrier |
| Make Model Name | B747-400 |
| Operating Under FAR Part | Part 121 |
| Navigation In Use | Other Other |
| Flight Phase | cruise other |
| Route In Use | enroute : pacific |
| Flight Plan | IFR |
| Aircraft 2 | |
| Operator | common carrier : air carrier |
| Make Model Name | B747 Undifferentiated or Other Model |
| Operating Under FAR Part | Part 121 |
| Flight Phase | climbout : intermediate altitude cruise other |
| Route In Use | enroute : pacific |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : atp |
| Experience | flight time last 90 days : 120 flight time total : 9000 flight time type : 1400 |
| ASRS Report | 373144 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp |
| Events | |
| Anomaly | altitude deviation : overshoot conflict : airborne less severe non adherence : clearance other anomaly other |
| Independent Detector | aircraft equipment other aircraft equipment : unspecified other flight crewa |
| Resolutory Action | flight crew : took evasive action |
| Consequence | Other |
| Miss Distance | horizontal : 600 vertical : 400 |
| Supplementary | |
| Primary Problem | ATC Human Performance |
| Air Traffic Incident | Pilot Deviation Operational Error |
Narrative:
En route with tokyo radio at FL350, aircraft below us was cleared to FL330 (we did not hear the clearance). We noted his initial climb on TCASII. We received a TA showing 400 ft separation and an 'up arrow' indication. At that point I disconnected the autoplt and went into a climbing left turn. The aircraft was visible below us on the left, descending. We reached an altitude of FL356 and began a descent to FL350. Much as I maligned the original TCASII software, I think it may have saved a midair in this case. Apparently, in my estimation, the other crew misset their intended altitude in the control panel and were in fact climbing to our altitude (which we had been at since nates). This form has been in my bag for 15 yrs, but I think this is an important incident. It shows the danger of missetting the intended altitude en route (since I assume they never received any warnings until the TA) and possibly the need for TA and RA training in simulator sessions (as I made what was, by our company manuals, a wrong decision and maneuvered away in a 2000 ft airspace separation situation without an RA). There were no other conflicts. Callback conversation with reporter revealed the following information: reporter states that they saw the aircraft on their TCASII leave FL310 and assumed it would level at FL330. When it kept on climbing up into reporter's altitude, he turned the aircraft to maintain a visual contact with it. The other aircraft made visual contact with reporter's aircraft and made an immediate descent to lower altitude. Reporter assumes the altitude limiter was never set in the conflicting aircraft cockpit. There never was any radio communication between the 2 aircraft. Even tokyo radio never said anything so tokyo ARTCC was never aware of any possible conflict. Reporter gives credit to TCASII for preventing a midair collision. They were navigating by GPS which is highly accurate. Because more air carrier's are using GPS for navigation, reporter believes an altitude deviation is more detrimental as an aircraft ascending into another aircraft will have no lateral separation. Any vertical movement will always be directly into another aircraft if there is no in trail separation. The other aircraft was a B747 from a foreign flag.
Original NASA ASRS Text
Title: THE FLC OF A B747-400 FLYING OVER THE NORTH PACIFIC NOTICE AN ACFT FLYING BELOW THEM ON THEIR TCASII DISPLAY AT FL310. THE LOWER ACFT STARTS TO CLB AND THE FLC ASSUMES THEY ARE GOING TO FL330, HOWEVER, THE LOWER ACFT CLBS THROUGH FL330 AND STARTS INTO FL350. RPTR TAKES EVASIVE ACTION, BUT NEVER RECEIVES A TCASII RA. AS THE OTHER ACFT APCHS FL350, HE EVIDENTLY SEES RPTR'S ACFT AND DSNDS TO FL330 IMMEDIATELY.
Narrative: ENRTE WITH TOKYO RADIO AT FL350, ACFT BELOW US WAS CLRED TO FL330 (WE DID NOT HEAR THE CLRNC). WE NOTED HIS INITIAL CLB ON TCASII. WE RECEIVED A TA SHOWING 400 FT SEPARATION AND AN 'UP ARROW' INDICATION. AT THAT POINT I DISCONNECTED THE AUTOPLT AND WENT INTO A CLBING L TURN. THE ACFT WAS VISIBLE BELOW US ON THE L, DSNDING. WE REACHED AN ALT OF FL356 AND BEGAN A DSCNT TO FL350. MUCH AS I MALIGNED THE ORIGINAL TCASII SOFTWARE, I THINK IT MAY HAVE SAVED A MIDAIR IN THIS CASE. APPARENTLY, IN MY ESTIMATION, THE OTHER CREW MISSET THEIR INTENDED ALT IN THE CTL PANEL AND WERE IN FACT CLBING TO OUR ALT (WHICH WE HAD BEEN AT SINCE NATES). THIS FORM HAS BEEN IN MY BAG FOR 15 YRS, BUT I THINK THIS IS AN IMPORTANT INCIDENT. IT SHOWS THE DANGER OF MISSETTING THE INTENDED ALT ENRTE (SINCE I ASSUME THEY NEVER RECEIVED ANY WARNINGS UNTIL THE TA) AND POSSIBLY THE NEED FOR TA AND RA TRAINING IN SIMULATOR SESSIONS (AS I MADE WHAT WAS, BY OUR COMPANY MANUALS, A WRONG DECISION AND MANEUVERED AWAY IN A 2000 FT AIRSPACE SEPARATION SIT WITHOUT AN RA). THERE WERE NO OTHER CONFLICTS. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATES THAT THEY SAW THE ACFT ON THEIR TCASII LEAVE FL310 AND ASSUMED IT WOULD LEVEL AT FL330. WHEN IT KEPT ON CLBING UP INTO RPTR'S ALT, HE TURNED THE ACFT TO MAINTAIN A VISUAL CONTACT WITH IT. THE OTHER ACFT MADE VISUAL CONTACT WITH RPTR'S ACFT AND MADE AN IMMEDIATE DSCNT TO LOWER ALT. RPTR ASSUMES THE ALT LIMITER WAS NEVER SET IN THE CONFLICTING ACFT COCKPIT. THERE NEVER WAS ANY RADIO COM BTWN THE 2 ACFT. EVEN TOKYO RADIO NEVER SAID ANYTHING SO TOKYO ARTCC WAS NEVER AWARE OF ANY POSSIBLE CONFLICT. RPTR GIVES CREDIT TO TCASII FOR PREVENTING A MIDAIR COLLISION. THEY WERE NAVING BY GPS WHICH IS HIGHLY ACCURATE. BECAUSE MORE ACR'S ARE USING GPS FOR NAV, RPTR BELIEVES AN ALTDEV IS MORE DETRIMENTAL AS AN ACFT ASCENDING INTO ANOTHER ACFT WILL HAVE NO LATERAL SEPARATION. ANY VERT MOVEMENT WILL ALWAYS BE DIRECTLY INTO ANOTHER ACFT IF THERE IS NO IN TRAIL SEPARATION. THE OTHER ACFT WAS A B747 FROM A FOREIGN FLAG.
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.