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First officer of a gulfstream 4 overshot descent intermediate altitude after vacating cruise altitude due to clearance interpretation dispute.
| Attributes | |
| ACN | 429201 |
| Time | |
| Date | 199902 |
| Day | Sat |
| Local Time Of Day | 1201 To 1800 |
| Place | |
| Locale Reference | navaid : bdf.vortac |
| State Reference | IL |
| Altitude | msl bound lower : 40400 msl bound upper : 41000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | artcc : zau.artcc |
| Operator | general aviation : corporate |
| Make Model Name | Gulfstream IV |
| Flight Phase | cruise : enroute altitude change descent : intermediate altitude descent : vacating altitude |
| Flight Plan | IFR |
| Aircraft 2 | |
| Controlling Facilities | artcc : zau.artcc |
| Make Model Name | Any Unknown or Unlisted Aircraft Manufacturer |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : corporate |
| Function | flight crew : first officer |
| Qualification | pilot : atp |
| Experience | fss specialist : 40 flight time last 90 days : 748 flight time total : 4000 flight time type : 340 |
| ASRS Report | 429201 |
| Person 2 | |
| Affiliation | company : corporate |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp |
| Experience | flight time last 90 days : 60 flight time total : 12000 flight time type : 15000 |
| ASRS Report | 429200 |
| Events | |
| Anomaly | altitude deviation : overshoot non adherence : clearance |
| Independent Detector | aircraft equipment : tcas other controllera |
| Resolutory Action | controller : issued alert flight crew : returned to original clearance |
| Miss Distance | horizontal : 18000 vertical : 1600 |
| Supplementary | |
| Problem Areas | ATC Human Performance Flight Crew Human Performance |
| Primary Problem | Flight Crew Human Performance |
| Air Traffic Incident | Pilot Deviation |
Narrative:
En route from iah to atw at FL450, the captain (PNF) went to use the restroom. Shortly thereafter, I received clearance to descend to FL310. I read back FL310 (I assume) and dialed '310' into the altitude preselector or alerter, programmed the vertical navigation, and began the descent. At about FL404, ZAU radioed 'aircraft X, maintain FL410.' I then leveled and climbed back up to FL410. As the captain climbed back into the cockpit he noticed a 'TA' on the TCASII display, but I did not notice this display during the maneuver. I then reset the altitude alerter to FL410 and continued the flight. I heard ZAU call our position to our local traffic, stating our horizontal distance as 3 mi. No safety alerts were issued and I assume there was no conflict. I cannot say with 100% surety that I read back 'FL310' to the controller, but I do know without a doubt that I put '310' into the altitude alerter, and why would I do this if I was not totally certain that was my clearance? It takes a lot of effort to crank the altitude alerter/preselector down from 450 to 310. Explanations: controller mistakenly cleared me to 'FL310.' controller cleared me to 'FL410' and I read back 'FL310.' controller cleared me to 'FL410,' I read back 'FL410' and dialed in 'FL310.' if I was in error by programming 'FL310' for the next target altitude, I think this event was the result of unfortunate timing since 2 pilots listening to ATC result in fewer communication errors, and extra vigilance is needed when someone leaves the flight deck.
Original NASA ASRS Text
Title: FO OF A GULFSTREAM 4 OVERSHOT DSCNT INTERMEDIATE ALT AFTER VACATING CRUISE ALT DUE TO CLRNC INTERP DISPUTE.
Narrative: ENRTE FROM IAH TO ATW AT FL450, THE CAPT (PNF) WENT TO USE THE RESTROOM. SHORTLY THEREAFTER, I RECEIVED CLRNC TO DSND TO FL310. I READ BACK FL310 (I ASSUME) AND DIALED '310' INTO THE ALT PRESELECTOR OR ALERTER, PROGRAMMED THE VERT NAV, AND BEGAN THE DSCNT. AT ABOUT FL404, ZAU RADIOED 'ACFT X, MAINTAIN FL410.' I THEN LEVELED AND CLBED BACK UP TO FL410. AS THE CAPT CLBED BACK INTO THE COCKPIT HE NOTICED A 'TA' ON THE TCASII DISPLAY, BUT I DID NOT NOTICE THIS DISPLAY DURING THE MANEUVER. I THEN RESET THE ALT ALERTER TO FL410 AND CONTINUED THE FLT. I HEARD ZAU CALL OUR POS TO OUR LCL TFC, STATING OUR HORIZ DISTANCE AS 3 MI. NO SAFETY ALERTS WERE ISSUED AND I ASSUME THERE WAS NO CONFLICT. I CANNOT SAY WITH 100% SURETY THAT I READ BACK 'FL310' TO THE CTLR, BUT I DO KNOW WITHOUT A DOUBT THAT I PUT '310' INTO THE ALT ALERTER, AND WHY WOULD I DO THIS IF I WAS NOT TOTALLY CERTAIN THAT WAS MY CLRNC? IT TAKES A LOT OF EFFORT TO CRANK THE ALT ALERTER/PRESELECTOR DOWN FROM 450 TO 310. EXPLANATIONS: CTLR MISTAKENLY CLRED ME TO 'FL310.' CTLR CLRED ME TO 'FL410' AND I READ BACK 'FL310.' CTLR CLRED ME TO 'FL410,' I READ BACK 'FL410' AND DIALED IN 'FL310.' IF I WAS IN ERROR BY PROGRAMMING 'FL310' FOR THE NEXT TARGET ALT, I THINK THIS EVENT WAS THE RESULT OF UNFORTUNATE TIMING SINCE 2 PLTS LISTENING TO ATC RESULT IN FEWER COM ERRORS, AND EXTRA VIGILANCE IS NEEDED WHEN SOMEONE LEAVES THE FLT DECK.
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.