December 23, 201312 yr Commercial Member Last night I was operating ACA15 to Hong Kong from Toronto. As I was prepping the FMC, I used my usual reduced thrust setting (TO-1) and proceeded to enter the CG and such so the FMC can calculate the v-speeds for me. Weird thing happened, it didn't! So after 5 minutes of fiddling, I went back and changed the thrust setting to TO, and the FMC was able to calculate the v-speed just fine. Can anyone explain the mechanics here? Is there a specific condition under which the FMC doesn't allow a reduced thrust takeoff/can't calculate the v-speed? It was a CYYZ takeoff with ASN, so the visibility was about 2-4 miles, and the wind was calm. Precipitation in the form of rain was present. AC was a few (~5000?) kgs short of MTOW I believe. (Will check the PFPX doc again). Thanks! Aamir Thacker
December 23, 201312 yr Generally this happens if the selected derate will not provide a safe takeoff. Try a lesser derate. Or, you had another issue in the perf section. Wes Meyer
December 23, 201312 yr Generally this happens if the selected derate will not provide a safe takeoff. Try a lesser derate. Or, you had another issue in the perf section. I would agree with that statement. This may be a dumb addition or it might not but always make sure you have your departure runway selected somewhere... I've had my fair share of headaches over that error! Regards, Jeremy Chesney
December 23, 201312 yr Yup Jeremy, that's a prerequisite for calculating a safe departure!!! ha ha! Wes Meyer
December 23, 201312 yr Author Commercial Member This may be a dumb addition or it might not but always make sure you have your departure runway selected somewhere... I've had my fair share of headaches over that error! Haha, that would seem like a fairly important addition It was selected this time around though, I think Wes is right, seeing as changing the derate from TO-1 to TO fixed it. Thanks! Aamir Thacker
December 23, 201312 yr You can do a search, this was discussed already. Bryan Richards "People depend so much on automation that they forget how to get the automation to work." B.W.
December 24, 201312 yr Author Commercial Member You can do a search, this was discussed already. The problem was already solved, but thank you for your constructive contribution! Aamir Thacker
December 24, 201312 yr The problem was already solved, but thank you for your constructive contribution! You're most welcomed Bryan Richards "People depend so much on automation that they forget how to get the automation to work." B.W.
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