dr_anthony Posted January 6, 2017 Report Share Posted January 6, 2017 Noticed that N1 derated thrust can't be dropped below 84,9 value, not in auto N1 mode, nor in manual n1 bug mode. Noticed it in winter flight, then d-to values really low. We believe FCOM: It means, that -20 OAT we can reduced TO thrust to 25 % - 84,8 - 25 % = 63,6 N1 And it means, that -40 OAT shouldn't be more than 81,4 - 82,1 in UNEE (880 AGL), but we can see this: And -50 OAT not more than 79,6 In high ambient temp and N1 higher 84,8 all works fine. That should be correct. Thanks. 1 Quote Link to comment Share on other sites More sharing options...
Litjan Posted January 6, 2017 Report Share Posted January 6, 2017 No. 25% less thrust is not N1 - 25. Thrust does not relate to N1 in a linear way. Quote Link to comment Share on other sites More sharing options...
dr_anthony Posted January 6, 2017 Author Report Share Posted January 6, 2017 40 minutes ago, Litjan said: No. 25% less thrust is not N1 - 25. Thrust does not relate to N1 in a linear way. Its correct. Thrust depend on OAT and pressure on tkf field (feet AGL). But it shouldn't exceed maximum values of 81,4 at -40 Cel OAT 0 AGL and 79,6 at -50 OAT 0 AGL all the way, isn't it? In IXEG FMC logic derates of TO thrust relate to N1 values linear: 106 N1 max - 25 % - 84,8 N1 min. Or in this conditions - below -40 Cel OAT needs to use manual takeoff thrust set? Quote Link to comment Share on other sites More sharing options...
Litjan Posted January 7, 2017 Report Share Posted January 7, 2017 Thanks for the report - we will look at it! Jan Quote Link to comment Share on other sites More sharing options...
dr_anthony Posted February 12, 2017 Author Report Share Posted February 12, 2017 Noticed also, in high ambient temp (Alice Springs YBAS +39 1800 ASL) full TOGA thrust actuated by AT not more than 84,8. Only recycle N1 limit on N1 page in CDU can fix that. 1 Quote Link to comment Share on other sites More sharing options...
uppcan Posted March 3, 2017 Report Share Posted March 3, 2017 the same problem occured to me. No matter which derated TO thrust i select, the n1 gauge stucks at 84.7% Quote Link to comment Share on other sites More sharing options...
Litjan Posted March 3, 2017 Report Share Posted March 3, 2017 (edited) We may revisit this at a later stage. The problem of A/T not setting correct thrust in some conditions is also on the review list. Thanks, Jan Edited March 3, 2017 by Litjan Quote Link to comment Share on other sites More sharing options...
dr_anthony Posted June 3, 2020 Author Report Share Posted June 3, 2020 Would be correct in 1.3.1? Quote Link to comment Share on other sites More sharing options...
Litjan Posted June 3, 2020 Report Share Posted June 3, 2020 Nope. Quote Link to comment Share on other sites More sharing options...
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