Narrative:

En route mdw-ind, thrust reverser 'isolation' light illuminated. It was first officer's leg so I had him slow us to 250 KTS to give us time to evaluate the situation (wind at FL210 gave us an 80 KT tailwind component). I got operations book out and researched cause for 'isolation' light. Approximately 70 NM from ind VOR center cleared us to cross 'jacks' at 15000 ft. First officer and I discussed potential causes for the isolation light and I had senior flight attendant come to cockpit to brief her to be especially vigilant on landing at ind and advise the B and C flight attendants of our situation. First officer began descent during our discussion so as to make the restr. I got back in the loop of xchking the restr at FL180 when we set our altimeter and I did the approach descent checklist. At that point we were 3 mi from jakks and unable to make it at 15000 ft. We crossed it at 17500 ft and apologized to ATC. Although first officer had read back jakks in the clearance, he had thought jells in his mind. Jakks is 31 DME from ind. Jells is 13 DME from ind. First officer figured he was way ahead of game for 1500 ft at jells. The malfunction we were evaluating, descending with 80 KT tailwind at 250 KTS, our briefing flight attendant and first officer mentally confusing the clearance, all contributed to the altitude bust. Recommendations: 1) PNF mentioned DME to PF when intxns sound similar and workload in cockpit is above normal. 2) when our cockpit routine and discipline was broken jakks and jells sounded too similar -- especially when the DME's were 31 and 13. 3) I should have caught it earlier, possibly brief flight attendant later in flight when level and not confronted with a crossing restr.

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Original NASA ASRS Text

Title: FLC OF A B737 ACR UNDERSHOT DSCNT XING ALT DUE TO MISINTERPRETING 2 INTXNS WITH SIMILAR SOUNDING NAMES AND A DISTR OF AN ACFT MECHANICAL PROB.

Narrative: ENRTE MDW-IND, THRUST REVERSER 'ISOLATION' LIGHT ILLUMINATED. IT WAS FO'S LEG SO I HAD HIM SLOW US TO 250 KTS TO GIVE US TIME TO EVALUATE THE SIT (WIND AT FL210 GAVE US AN 80 KT TAILWIND COMPONENT). I GOT OPS BOOK OUT AND RESEARCHED CAUSE FOR 'ISOLATION' LIGHT. APPROX 70 NM FROM IND VOR CTR CLRED US TO CROSS 'JACKS' AT 15000 FT. FO AND I DISCUSSED POTENTIAL CAUSES FOR THE ISOLATION LIGHT AND I HAD SENIOR FLT ATTENDANT COME TO COCKPIT TO BRIEF HER TO BE ESPECIALLY VIGILANT ON LNDG AT IND AND ADVISE THE B AND C FLT ATTENDANTS OF OUR SIT. FO BEGAN DSCNT DURING OUR DISCUSSION SO AS TO MAKE THE RESTR. I GOT BACK IN THE LOOP OF XCHKING THE RESTR AT FL180 WHEN WE SET OUR ALTIMETER AND I DID THE APCH DSCNT CHKLIST. AT THAT POINT WE WERE 3 MI FROM JAKKS AND UNABLE TO MAKE IT AT 15000 FT. WE CROSSED IT AT 17500 FT AND APOLOGIZED TO ATC. ALTHOUGH FO HAD READ BACK JAKKS IN THE CLRNC, HE HAD THOUGHT JELLS IN HIS MIND. JAKKS IS 31 DME FROM IND. JELLS IS 13 DME FROM IND. FO FIGURED HE WAS WAY AHEAD OF GAME FOR 1500 FT AT JELLS. THE MALFUNCTION WE WERE EVALUATING, DSNDING WITH 80 KT TAILWIND AT 250 KTS, OUR BRIEFING FLT ATTENDANT AND FO MENTALLY CONFUSING THE CLRNC, ALL CONTRIBUTED TO THE ALT BUST. RECOMMENDATIONS: 1) PNF MENTIONED DME TO PF WHEN INTXNS SOUND SIMILAR AND WORKLOAD IN COCKPIT IS ABOVE NORMAL. 2) WHEN OUR COCKPIT ROUTINE AND DISCIPLINE WAS BROKEN JAKKS AND JELLS SOUNDED TOO SIMILAR -- ESPECIALLY WHEN THE DME'S WERE 31 AND 13. 3) I SHOULD HAVE CAUGHT IT EARLIER, POSSIBLY BRIEF FLT ATTENDANT LATER IN FLT WHEN LEVEL AND NOT CONFRONTED WITH A XING RESTR.

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.