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37000 Feet | Browse and search NASA's Aviation Safety Reporting System |
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Air carrier X descent to occupied altitude (wrong altitude setting issued) had less less than standard separation from air carrier Y. System error.
| Attributes | |
| ACN | 199771 |
| Time | |
| Date | 199201 |
| Day | Thu |
| Local Time Of Day | 0601 To 1200 |
| Place | |
| Locale Reference | atc facility : iiu |
| State Reference | KY |
| Altitude | msl bound lower : 11000 msl bound upper : 12000 |
| Environment | |
| Flight Conditions | IMC |
| Light | Daylight |
| Aircraft 1 | |
| Operator | common carrier : air carrier |
| Make Model Name | Light Transport, Low Wing, 2 Turboprop Eng |
| Flight Phase | descent other |
| Route In Use | enroute : direct enroute airway : zid |
| Flight Plan | IFR |
| Aircraft 2 | |
| Operator | common carrier : air carrier |
| Make Model Name | Light Transport, Low Wing, 2 Turboprop Eng |
| Flight Phase | cruise other |
| Route In Use | enroute : direct |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | government : faa |
| Function | controller : radar |
| Qualification | controller : radar |
| Experience | controller radar : 21 |
| ASRS Report | 199771 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp |
| Experience | flight time last 90 days : 240 flight time total : 5000 flight time type : 1000 |
| ASRS Report | 200427 |
| Events | |
| Anomaly | altitude deviation : overshoot conflict : airborne less severe non adherence : published procedure non adherence : required legal separation |
| Independent Detector | other controllera |
| Resolutory Action | other |
| Consequence | faa : investigated |
| Miss Distance | horizontal : 15000 vertical : 200 |
| Supplementary | |
| Primary Problem | ATC Human Performance |
| Air Traffic Incident | Operational Error |
Narrative:
Air carrier X cleared to descend to 110. Altimeter incorrectly given as 30.49 (actually 29.49). Air carrier Y cleared to climb to 110 and air carrier X cleared to amend altitude to 120. Air carrier X acknowledged mode C. Air carrier X showed 116. Controller asked air carrier X to verify assigned altitude 120. Air carrier X reported 126 for 120. Air carrier Y level 110 passed 3.5 KM behind air carrier X at 110. At first thought mode C error. But voice tape at center clearly indicated controller gave erroneous altimeter setting. Supplemental information from acn 200427: while descending to an assigned altitude of 15000 ft I checked in on a new frequency with center. I was issued and read back an altimeter setting of 30.46. I was shortly thereafter instructed to descend to 11000 ft which center amended to 12000 ft. As we were about to level at 12000 ft, center asked our altitude I told the controller we were leveling at 12000 ft and he said our altitude indicated 11200 ft. I then transmitted our altitude indicated 12000 ft with an altimeter of 30.46. With no response from center I overheard another aircraft transmit that someone readback a wrong altimeter. Knowing that something was seriously wrong, I attempted to contact center for instructions as I believe there was an aircraft at 11000 ft about 1 mi behind me. I discovered the correct altimeter setting to be 29.47 instead of 30.46 which we set in and initiated a climb back to 12000 ft. At about 11500 center instructed me to descend to 11000.
Original NASA ASRS Text
Title: ACR X DSCNT TO OCCUPIED ALT (WRONG ALT SETTING ISSUED) HAD LESS LTSS FROM ACR Y. SYS ERROR.
Narrative: ACR X CLRED TO DSND TO 110. ALTIMETER INCORRECTLY GIVEN AS 30.49 (ACTUALLY 29.49). ACR Y CLRED TO CLB TO 110 AND ACR X CLRED TO AMEND ALT TO 120. ACR X ACKNOWLEDGED MODE C. ACR X SHOWED 116. CTLR ASKED ACR X TO VERIFY ASSIGNED ALT 120. ACR X RPTED 126 FOR 120. ACR Y LEVEL 110 PASSED 3.5 KM BEHIND ACR X AT 110. AT FIRST THOUGHT MODE C ERROR. BUT VOICE TAPE AT CTR CLRLY INDICATED CTLR GAVE ERRONEOUS ALTIMETER SETTING. SUPPLEMENTAL INFO FROM ACN 200427: WHILE DSNDING TO AN ASSIGNED ALT OF 15000 FT I CHKED IN ON A NEW FREQ WITH CTR. I WAS ISSUED AND READ BACK AN ALTIMETER SETTING OF 30.46. I WAS SHORTLY THEREAFTER INSTRUCTED TO DSND TO 11000 FT WHICH CTR AMENDED TO 12000 FT. AS WE WERE ABOUT TO LEVEL AT 12000 FT, CTR ASKED OUR ALT I TOLD THE CTLR WE WERE LEVELING AT 12000 FT AND HE SAID OUR ALT INDICATED 11200 FT. I THEN XMITTED OUR ALT INDICATED 12000 FT WITH AN ALTIMETER OF 30.46. WITH NO RESPONSE FROM CTR I OVERHEARD ANOTHER ACFT XMIT THAT SOMEONE READBACK A WRONG ALTIMETER. KNOWING THAT SOMETHING WAS SERIOUSLY WRONG, I ATTEMPTED TO CONTACT CTR FOR INSTRUCTIONS AS I BELIEVE THERE WAS AN ACFT AT 11000 FT ABOUT 1 MI BEHIND ME. I DISCOVERED THE CORRECT ALTIMETER SETTING TO BE 29.47 INSTEAD OF 30.46 WHICH WE SET IN AND INITIATED A CLB BACK TO 12000 FT. AT ABOUT 11500 CTR INSTRUCTED ME TO DSND TO 11000.
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.