Narrative:

The captain was the PF on our B-767 flying north on J-53 from charlotte to pittsburgh at FL290. The aircraft was on the autoplt. ATC issued us a crossing restr to cross 30 mi south of riccs intersection at FL240. If riccs was our next intersection, we could have easily built our crossing restr waypoint as an 'along track waypoint' by entering riccs/-30 and inserting it before riccs. However, since there were several waypoints between our position and riccs, this simple method would not work. Instead, the captain looked at our legs page, and tried to add several waypoints back from riccs to see if he could find a waypoint which was 30 mi south of riccs. Being unsuccessful, he asked me to just put the crossing restr at perri intersection. I backed up the captain's arithmetic computations, and agreed to enter the restr at perri intersection, which I calculated was actually 39 mi south of riccs (the next intersection north of perri would have been too short, being only 16 mi south of riccs). I entered FL240 and entered it in the position next to perri, or so I thought. As I was doing this I glanced at the captain to be sure he was monitoring my entry and I verbally said something similar to 'FL240 at perri.' I saw that the captain was indeed monitoring my entry and nodded an approval. The captain and I verified that 24000 ft was set in our altitude window, and I checked to make sure we were still in VNAV, and noticed a top of descent point not too far ahead of us on our map. I felt confident the aircraft would cross 39 mi south of riccs at FL240. Right after this we had 2 company pilots sitting on our cockpit jumpseats initiate some details of our new proposed pilot paycuts and concessions to our company management. This was new and disturbing information to me, and I felt both the captain and I were somewhat distracted from monitoring the descent of the aircraft by these pilots revealing this information. ATC then called us and wanted to know when we were going to start our descent. I looked at the cruise page and saw and reported we would start down in 4 mi. ATC acknowledged my call and seemed satisfied, and this made me feelthat there was no problem with our descent planning. The aircraft started descending at which we thought was the proper top of descent point. Then ATC called back and asked if we understood our crossing restr. At this time I looked again at the descent page and at our descent GS on the right side of our map and both showed us right on our descent profile. Then my thoughts turned to our departure from charlotte. Immediately after leaving charlotte, ATC questioned us on our altitude, and they determined that our mode C altitude reporting was about 1000 ft off. We switched to our other transponder and ATC responded that our reported altitude was now the same as what was showing on their screen. I thought that we were possibly having more mode C altitude reporting problems, and it still did not occur to me that we were having a crossing restr problem. I lost some precious time here that could have been used to alert ATC of our error a little sooner. I looked at our map and saw that riccs intersection seemed closer to our position than it should have been. At this time I felt that there was something wrong with our crossing restr. I immediately scanned outside again to look for possible conflicting traffic since the WX was good VFR (I saw no aircraft). I quickly looked at our TCASII to see if there was any traffic showing in our area (there was no traffic shown nearby), and I called ATC to report our descending altitude so they would be aware of our situation and could issue vectors or instructions to us or possible conflicting traffic. ATC seemed to be aware of our missed crossing restr, but did not say anything about any conflicting traffic in the area, and issued a frequency change for us without any further discussion. I quickly checked in on the new frequency and reported level at FL240, since we had leveled off by this time. The new controller did not ask anything about our previous crossing restr and seemed satisfied with our altitude and position. I believe my entry of FL240 ended up next to perks intersection instead of my intended entry next to perri intersection. I think that just before I put FL240 next to perri, we passed a waypoint on our route and then the waypoints on our legs page all scrolled up one waypoint so that just 1/2 a second before my entry the waypoint changed from perri to perks, and both the captain and I did not catch this. If these intxns were not so similar in name (both start with per) we may have caught our error. As a pilot, I will be on the lookout for this potential situation to happen again, and will double-check to see if the crossing altitude did in fact end up next to the proper waypoint. I will also put the waypoint on the fix page and monitor it as a backup to verify that we are on a proper descent profile. I would recommend to ATC to give crossing restrs to aircraft equipped with a FMS at a specific waypoint along the route. This would minimize the potential for an error. Also I feel changing similar appearing names such as perri and perks could minimize the potential for error.

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Original NASA ASRS Text

Title: ALT XING RESTR. THE FLC ENTER DATA INCORRECTLY IN THE FMC AND CROSS THE RESTR TOO HIGH.

Narrative: THE CAPT WAS THE PF ON OUR B-767 FLYING N ON J-53 FROM CHARLOTTE TO PITTSBURGH AT FL290. THE ACFT WAS ON THE AUTOPLT. ATC ISSUED US A XING RESTR TO CROSS 30 MI S OF RICCS INTXN AT FL240. IF RICCS WAS OUR NEXT INTXN, WE COULD HAVE EASILY BUILT OUR XING RESTR WAYPOINT AS AN 'ALONG TRACK WAYPOINT' BY ENTERING RICCS/-30 AND INSERTING IT BEFORE RICCS. HOWEVER, SINCE THERE WERE SEVERAL WAYPOINTS BTWN OUR POS AND RICCS, THIS SIMPLE METHOD WOULD NOT WORK. INSTEAD, THE CAPT LOOKED AT OUR LEGS PAGE, AND TRIED TO ADD SEVERAL WAYPOINTS BACK FROM RICCS TO SEE IF HE COULD FIND A WAYPOINT WHICH WAS 30 MI S OF RICCS. BEING UNSUCCESSFUL, HE ASKED ME TO JUST PUT THE XING RESTR AT PERRI INTXN. I BACKED UP THE CAPT'S ARITHMETIC COMPUTATIONS, AND AGREED TO ENTER THE RESTR AT PERRI INTXN, WHICH I CALCULATED WAS ACTUALLY 39 MI S OF RICCS (THE NEXT INTXN N OF PERRI WOULD HAVE BEEN TOO SHORT, BEING ONLY 16 MI S OF RICCS). I ENTERED FL240 AND ENTERED IT IN THE POS NEXT TO PERRI, OR SO I THOUGHT. AS I WAS DOING THIS I GLANCED AT THE CAPT TO BE SURE HE WAS MONITORING MY ENTRY AND I VERBALLY SAID SOMETHING SIMILAR TO 'FL240 AT PERRI.' I SAW THAT THE CAPT WAS INDEED MONITORING MY ENTRY AND NODDED AN APPROVAL. THE CAPT AND I VERIFIED THAT 24000 FT WAS SET IN OUR ALT WINDOW, AND I CHKED TO MAKE SURE WE WERE STILL IN VNAV, AND NOTICED A TOP OF DSCNT POINT NOT TOO FAR AHEAD OF US ON OUR MAP. I FELT CONFIDENT THE ACFT WOULD CROSS 39 MI S OF RICCS AT FL240. RIGHT AFTER THIS WE HAD 2 COMPANY PLTS SITTING ON OUR COCKPIT JUMPSEATS INITIATE SOME DETAILS OF OUR NEW PROPOSED PLT PAYCUTS AND CONCESSIONS TO OUR COMPANY MGMNT. THIS WAS NEW AND DISTURBING INFO TO ME, AND I FELT BOTH THE CAPT AND I WERE SOMEWHAT DISTRACTED FROM MONITORING THE DSCNT OF THE ACFT BY THESE PLTS REVEALING THIS INFO. ATC THEN CALLED US AND WANTED TO KNOW WHEN WE WERE GOING TO START OUR DSCNT. I LOOKED AT THE CRUISE PAGE AND SAW AND RPTED WE WOULD START DOWN IN 4 MI. ATC ACKNOWLEDGED MY CALL AND SEEMED SATISFIED, AND THIS MADE ME FEELTHAT THERE WAS NO PROB WITH OUR DSCNT PLANNING. THE ACFT STARTED DSNDING AT WHICH WE THOUGHT WAS THE PROPER TOP OF DSCNT POINT. THEN ATC CALLED BACK AND ASKED IF WE UNDERSTOOD OUR XING RESTR. AT THIS TIME I LOOKED AGAIN AT THE DSCNT PAGE AND AT OUR DSCNT GS ON THE R SIDE OF OUR MAP AND BOTH SHOWED US RIGHT ON OUR DSCNT PROFILE. THEN MY THOUGHTS TURNED TO OUR DEP FROM CHARLOTTE. IMMEDIATELY AFTER LEAVING CHARLOTTE, ATC QUESTIONED US ON OUR ALT, AND THEY DETERMINED THAT OUR MODE C ALT RPTING WAS ABOUT 1000 FT OFF. WE SWITCHED TO OUR OTHER XPONDER AND ATC RESPONDED THAT OUR RPTED ALT WAS NOW THE SAME AS WHAT WAS SHOWING ON THEIR SCREEN. I THOUGHT THAT WE WERE POSSIBLY HAVING MORE MODE C ALT RPTING PROBS, AND IT STILL DID NOT OCCUR TO ME THAT WE WERE HAVING A XING RESTR PROB. I LOST SOME PRECIOUS TIME HERE THAT COULD HAVE BEEN USED TO ALERT ATC OF OUR ERROR A LITTLE SOONER. I LOOKED AT OUR MAP AND SAW THAT RICCS INTXN SEEMED CLOSER TO OUR POS THAN IT SHOULD HAVE BEEN. AT THIS TIME I FELT THAT THERE WAS SOMETHING WRONG WITH OUR XING RESTR. I IMMEDIATELY SCANNED OUTSIDE AGAIN TO LOOK FOR POSSIBLE CONFLICTING TFC SINCE THE WX WAS GOOD VFR (I SAW NO ACFT). I QUICKLY LOOKED AT OUR TCASII TO SEE IF THERE WAS ANY TFC SHOWING IN OUR AREA (THERE WAS NO TFC SHOWN NEARBY), AND I CALLED ATC TO RPT OUR DSNDING ALT SO THEY WOULD BE AWARE OF OUR SIT AND COULD ISSUE VECTORS OR INSTRUCTIONS TO US OR POSSIBLE CONFLICTING TFC. ATC SEEMED TO BE AWARE OF OUR MISSED XING RESTR, BUT DID NOT SAY ANYTHING ABOUT ANY CONFLICTING TFC IN THE AREA, AND ISSUED A FREQ CHANGE FOR US WITHOUT ANY FURTHER DISCUSSION. I QUICKLY CHKED IN ON THE NEW FREQ AND RPTED LEVEL AT FL240, SINCE WE HAD LEVELED OFF BY THIS TIME. THE NEW CTLR DID NOT ASK ANYTHING ABOUT OUR PREVIOUS XING RESTR AND SEEMED SATISFIED WITH OUR ALT AND POS. I BELIEVE MY ENTRY OF FL240 ENDED UP NEXT TO PERKS INTXN INSTEAD OF MY INTENDED ENTRY NEXT TO PERRI INTXN. I THINK THAT JUST BEFORE I PUT FL240 NEXT TO PERRI, WE PASSED A WAYPOINT ON OUR RTE AND THEN THE WAYPOINTS ON OUR LEGS PAGE ALL SCROLLED UP ONE WAYPOINT SO THAT JUST 1/2 A SECOND BEFORE MY ENTRY THE WAYPOINT CHANGED FROM PERRI TO PERKS, AND BOTH THE CAPT AND I DID NOT CATCH THIS. IF THESE INTXNS WERE NOT SO SIMILAR IN NAME (BOTH START WITH PER) WE MAY HAVE CAUGHT OUR ERROR. AS A PLT, I WILL BE ON THE LOOKOUT FOR THIS POTENTIAL SIT TO HAPPEN AGAIN, AND WILL DOUBLE-CHK TO SEE IF THE XING ALT DID IN FACT END UP NEXT TO THE PROPER WAYPOINT. I WILL ALSO PUT THE WAYPOINT ON THE FIX PAGE AND MONITOR IT AS A BACKUP TO VERIFY THAT WE ARE ON A PROPER DSCNT PROFILE. I WOULD RECOMMEND TO ATC TO GIVE XING RESTRS TO ACFT EQUIPPED WITH A FMS AT A SPECIFIC WAYPOINT ALONG THE RTE. THIS WOULD MINIMIZE THE POTENTIAL FOR AN ERROR. ALSO I FEEL CHANGING SIMILAR APPEARING NAMES SUCH AS PERRI AND PERKS COULD MINIMIZE THE POTENTIAL FOR ERROR.

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.