Narrative:

Nov/89 the flight was to depart bikf en route to cyqx along a random track route. Upon request of the clearance, I was asked by bikf if I could cross uniform at FL350 and be level at FL39O and .74 mach by 63N 30W. I stated that I was unable to comply with both altitude and mach requirements. Shortly thereafter, bikf issued a reroute: FL280 mach .74. Expect higher altitude to follow FL390. I accepted this routing knowing I could comply with both the flight level and mach .74 at that level. This new route was also north of my original track. Since the new route was north of the original track and the flight level above the nat structure, ie, FL390, I felt I could comply. Climb to altitude was better than expected due to headwinds. I saw that I would be able to reach FL390 before 60N 40W and requested and received further climb to FL390. No level off was made at FL280. Upon reaching FL390 I began the acceleration to cruise speed. The temperature at FL390 was -30C which is somewhat higher than normal. The best I was able to do was mach .65 initially and .68 later and by the exit point, .72 mach. During the time of cruise portion of the flight the ETA's were exact according to the computer flight plan. Upon contact with gander center I was asked if I had maintained the assigned mach .74 and what my current mach was. I responded with .70 mach. I now realize that the revised clearance route also meant to maintain .74 mach as well at the cruise altitude of FL390. I did not report the lower mach number because I assumed .74 mach applied to the lower FL280 and flight plan speeds were to be used at cruise height. I also assumed that my initial refusal of the original route and mach assignment was adequate notification of inability to comply with the mach requirement. I am fully aware of the requirement to report a change in speed etc while operating in the north atlantic airspace. The report was not given in this case because I thought ATC was aware of the limitations stated earlier and that the flight was in fact progressing along according to the position reports given at the reporting points on the route. I shall make no assumptions as to whether ATC has the proper information with regard to any aspects of the performance of the aircraft, or the ability to comply with an assigned clearance.

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Original NASA ASRS Text

Title: ATX LTT ACCEPTED CLRNC TO FL390 BUT WAS UNABLE TO MAINTAIN THE FLT PLANNED MACH.

Narrative: NOV/89 THE FLT WAS TO DEPART BIKF ENRTE TO CYQX ALONG A RANDOM TRACK ROUTE. UPON REQUEST OF THE CLRNC, I WAS ASKED BY BIKF IF I COULD CROSS UNIFORM AT FL350 AND BE LEVEL AT FL39O AND .74 MACH BY 63N 30W. I STATED THAT I WAS UNABLE TO COMPLY WITH BOTH ALT AND MACH REQUIREMENTS. SHORTLY THEREAFTER, BIKF ISSUED A REROUTE: FL280 MACH .74. EXPECT HIGHER ALT TO FOLLOW FL390. I ACCEPTED THIS ROUTING KNOWING I COULD COMPLY WITH BOTH THE FLT LEVEL AND MACH .74 AT THAT LEVEL. THIS NEW ROUTE WAS ALSO N OF MY ORIGINAL TRACK. SINCE THE NEW ROUTE WAS N OF THE ORIGINAL TRACK AND THE FLT LEVEL ABOVE THE NAT STRUCTURE, IE, FL390, I FELT I COULD COMPLY. CLIMB TO ALT WAS BETTER THAN EXPECTED DUE TO HEADWINDS. I SAW THAT I WOULD BE ABLE TO REACH FL390 BEFORE 60N 40W AND REQUESTED AND RECEIVED FURTHER CLIMB TO FL390. NO LEVEL OFF WAS MADE AT FL280. UPON REACHING FL390 I BEGAN THE ACCELERATION TO CRUISE SPEED. THE TEMPERATURE AT FL390 WAS -30C WHICH IS SOMEWHAT HIGHER THAN NORMAL. THE BEST I WAS ABLE TO DO WAS MACH .65 INITIALLY AND .68 LATER AND BY THE EXIT POINT, .72 MACH. DURING THE TIME OF CRUISE PORTION OF THE FLT THE ETA'S WERE EXACT ACCORDING TO THE COMPUTER FLT PLAN. UPON CONTACT WITH GANDER CENTER I WAS ASKED IF I HAD MAINTAINED THE ASSIGNED MACH .74 AND WHAT MY CURRENT MACH WAS. I RESPONDED WITH .70 MACH. I NOW REALIZE THAT THE REVISED CLRNC ROUTE ALSO MEANT TO MAINTAIN .74 MACH AS WELL AT THE CRUISE ALT OF FL390. I DID NOT REPORT THE LOWER MACH NUMBER BECAUSE I ASSUMED .74 MACH APPLIED TO THE LOWER FL280 AND FLT PLAN SPEEDS WERE TO BE USED AT CRUISE HEIGHT. I ALSO ASSUMED THAT MY INITIAL REFUSAL OF THE ORIGINAL ROUTE AND MACH ASSIGNMENT WAS ADEQUATE NOTIFICATION OF INABILITY TO COMPLY WITH THE MACH REQUIREMENT. I AM FULLY AWARE OF THE REQUIREMENT TO REPORT A CHANGE IN SPEED ETC WHILE OPERATING IN THE NORTH ATLANTIC AIRSPACE. THE REPORT WAS NOT GIVEN IN THIS CASE BECAUSE I THOUGHT ATC WAS AWARE OF THE LIMITATIONS STATED EARLIER AND THAT THE FLT WAS IN FACT PROGRESSING ALONG ACCORDING TO THE POSITION REPORTS GIVEN AT THE REPORTING POINTS ON THE ROUTE. I SHALL MAKE NO ASSUMPTIONS AS TO WHETHER ATC HAS THE PROPER INFO WITH REGARD TO ANY ASPECTS OF THE PERFORMANCE OF THE ACFT, OR THE ABILITY TO COMPLY WITH AN ASSIGNED CLRNC.

Data retrieved from NASA's ASRS site as of August 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.