Narrative:

We were en route from cmh to lga on the tue of august. We were on with new york center, and we had started our initial gradual descent into the new york area. I was the non flying pilot. Center gave us a descent instruction and a speed restriction. The instructions given were not unusual. What the controller said, what I heard and read back, and what the captain flew I think are three different or two different things. The altitudes involved are either FL250 or FL260 and FL250 knots. In hindsight, the controller wanted us at FL260, but we understood FL250, when in fact '250' was probably the speed restriction. As a result, at about FL255 we received a traffic alert and subsequent RA. At the same time, center called us with 'traffic at 3 O'clock.' we acknowledged the traffic in sight. The traffic proceeded 500 to 1000 ft below us, the TA and RA ceased, and center called us back to verify that we were at FL260. We replied that we understood FL250. We were handed off shortly thereafter with nothing else being discussed on the topic. Contributing factors: 1) misunderstanding of the flight crew of an ATC clearance. I don't know if the controller gave an improper clearance or if we misunderstood the clearance and deviated from the intended clearance. 2) pilot fatigue was definitely a factor. We were on a reduced rest of 8 hours and had less than 6 hours rest the night before due to waiting for the hotel van, eating, showering etc. We flew over 6 hours that day without an APU with temperatures in the high 90's in the passenger cabin due to lack of air conditioning, and waited over 2 hours on the taxiway in lga earlier that day in these conditions.

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Original NASA ASRS Text

Title: A CL-65 RJ FLT CREW DSNDS BELOW THEIR ASSIGNED ALT AND EXPERIENCE A POTENTIAL CONFLICT W OF LGA, NY.

Narrative: WE WERE ENRTE FROM CMH TO LGA ON THE TUE OF AUGUST. WE WERE ON WITH NEW YORK CENTER, AND WE HAD STARTED OUR INITIAL GRADUAL DSCNT INTO THE NEW YORK AREA. I WAS THE NON FLYING PLT. CENTER GAVE US A DSCNT INSTRUCTION AND A SPEED RESTRICTION. THE INSTRUCTIONS GIVEN WERE NOT UNUSUAL. WHAT THE CTLR SAID, WHAT I HEARD AND READ BACK, AND WHAT THE CAPT FLEW I THINK ARE THREE DIFFERENT OR TWO DIFFERENT THINGS. THE ALTITUDES INVOLVED ARE EITHER FL250 OR FL260 AND FL250 KNOTS. IN HINDSIGHT, THE CTLR WANTED US AT FL260, BUT WE UNDERSTOOD FL250, WHEN IN FACT '250' WAS PROBABLY THE SPEED RESTRICTION. AS A RESULT, AT ABOUT FL255 WE RECEIVED A TFC ALERT AND SUBSEQUENT RA. AT THE SAME TIME, CENTER CALLED US WITH 'TFC AT 3 O'CLOCK.' WE ACKNOWLEDGED THE TFC IN SIGHT. THE TFC PROCEEDED 500 TO 1000 FT BELOW US, THE TA AND RA CEASED, AND CENTER CALLED US BACK TO VERIFY THAT WE WERE AT FL260. WE REPLIED THAT WE UNDERSTOOD FL250. WE WERE HANDED OFF SHORTLY THEREAFTER WITH NOTHING ELSE BEING DISCUSSED ON THE TOPIC. CONTRIBUTING FACTORS: 1) MISUNDERSTANDING OF THE FLT CREW OF AN ATC CLRNC. I DON'T KNOW IF THE CTLR GAVE AN IMPROPER CLRNC OR IF WE MISUNDERSTOOD THE CLRNC AND DEVIATED FROM THE INTENDED CLRNC. 2) PLT FATIGUE WAS DEFINITELY A FACTOR. WE WERE ON A REDUCED REST OF 8 HRS AND HAD LESS THAN 6 HRS REST THE NIGHT BEFORE DUE TO WAITING FOR THE HOTEL VAN, EATING, SHOWERING ETC. WE FLEW OVER 6 HRS THAT DAY WITHOUT AN APU WITH TEMPERATURES IN THE HIGH 90'S IN THE PAX CABIN DUE TO LACK OF AIR CONDITIONING, AND WAITED OVER 2 HRS ON THE TXWY IN LGA EARLIER THAT DAY IN THESE CONDITIONS.

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.