Narrative:

We were operating an large transport aircraft from ont to ord. Our takeoff weight was at 93% of maximum. We received a clearance to depart on the pom 4 departure with a dag transition. Ont clearance delivery asked us if we could make the 14000' restriction at dowst intersection. We had received a NOTAM reminding us of the restriction. Evidently recent aircraft had not been able to make it up to 14000' by dowst. Our company does not provide us with 'time/distance to climb' charts, but we calculated that we would be able to make the restriction. This was based on climbing at best angle climb speed (230 KTS was as close as we could get to vx 220 at our weight) and a rate of climb of 1800 FPM. We answered ATC that 'yes, we can make it.' we took off using maximum takeoff power and at 1000' AGL began our climb out at 230 KTS and climb power set on the engines. We crossed pom above the minimum restr altitude, crossing it at 4200'. We were maintaining approximately 2200 FPM rate of climb, so it looked good at this point. Approaching 9000' we must have ran into an inversion layer. (The temperature was close to the ont surface temperature) and the rate of climb began to deteriorate. Soon afterward we applied maximum continuous thrust, but with 3 or so mi to dowst it became evident that we weren't going to make it.. The controller came on and asked us if we had been asked previously about making dowst. We replied that we had and answered in the affirmative. We then crossed dowst at 12800'. There are several reasons for this occurrence. First of all, our decreased rate of climb in the last 8 mi to dowst because of temperature. Secondly, the restriction at dowst is too high for warm days/heavy type pwred aircraft. Also contributing is the lack of climb performance charts provided to us.

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Original NASA ASRS Text

Title: ACR X FAILED TO COMPLY WITH ATC CLRNC. UNDERSHOT ALT CROSSING RESTRICTION. PLT DEVIATION. SITUATION: LGT TYPE ACFT UNABLE TO COMPLY WITH DOWST CROSSING RESTRICTION DURING HOT WX.

Narrative: WE WERE OPERATING AN LGT ACFT FROM ONT TO ORD. OUR TKOF WT WAS AT 93% OF MAX. WE RECEIVED A CLRNC TO DEPART ON THE POM 4 DEP WITH A DAG TRANSITION. ONT CLRNC DELIVERY ASKED US IF WE COULD MAKE THE 14000' RESTRICTION AT DOWST INTXN. WE HAD RECEIVED A NOTAM REMINDING US OF THE RESTRICTION. EVIDENTLY RECENT ACFT HAD NOT BEEN ABLE TO MAKE IT UP TO 14000' BY DOWST. OUR COMPANY DOES NOT PROVIDE US WITH 'TIME/DISTANCE TO CLB' CHARTS, BUT WE CALCULATED THAT WE WOULD BE ABLE TO MAKE THE RESTRICTION. THIS WAS BASED ON CLBING AT BEST ANGLE CLB SPD (230 KTS WAS AS CLOSE AS WE COULD GET TO VX 220 AT OUR WT) AND A RATE OF CLB OF 1800 FPM. WE ANSWERED ATC THAT 'YES, WE CAN MAKE IT.' WE TOOK OFF USING MAX TKOF PWR AND AT 1000' AGL BEGAN OUR CLBOUT AT 230 KTS AND CLB PWR SET ON THE ENGS. WE CROSSED POM ABOVE THE MINIMUM RESTR ALT, XING IT AT 4200'. WE WERE MAINTAINING APPROX 2200 FPM RATE OF CLB, SO IT LOOKED GOOD AT THIS POINT. APCHING 9000' WE MUST HAVE RAN INTO AN INVERSION LAYER. (THE TEMP WAS CLOSE TO THE ONT SURFACE TEMP) AND THE RATE OF CLB BEGAN TO DETERIORATE. SOON AFTERWARD WE APPLIED MAX CONTINUOUS THRUST, BUT WITH 3 OR SO MI TO DOWST IT BECAME EVIDENT THAT WE WEREN'T GOING TO MAKE IT.. THE CTLR CAME ON AND ASKED US IF WE HAD BEEN ASKED PREVIOUSLY ABOUT MAKING DOWST. WE REPLIED THAT WE HAD AND ANSWERED IN THE AFFIRMATIVE. WE THEN CROSSED DOWST AT 12800'. THERE ARE SEVERAL REASONS FOR THIS OCCURRENCE. FIRST OF ALL, OUR DECREASED RATE OF CLB IN THE LAST 8 MI TO DOWST BECAUSE OF TEMP. SECONDLY, THE RESTRICTION AT DOWST IS TOO HIGH FOR WARM DAYS/HVY TYPE PWRED ACFT. ALSO CONTRIBUTING IS THE LACK OF CLB PERFORMANCE CHARTS PROVIDED TO US.

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.