F-WWAI From Andorra, joined Dec 1999, 131 posts, RR: 0
Reply 2, posted (13 years 2 months 2 weeks 4 days 7 hours ago) and read 977 times:
that's relatively simple.
imagine that your max take off thrust available depends on outside air temperature. it's flat rated (=constant) until a certain temp (e.g. ISA +15C) then decreases linearily with temperature to maintain constant turbine entry temperature.
given this, you may understand that you can take off a certain aircraft gross weight until a certain OAT. got it?
imagine now you are at low OAT but you have a GW which permits take-off at ISA + 40C. then you can tell you thrust control to compute the take-off thrust at the assumed temperature of ISA+40C, and you will obtain the thrust required for the take-off.
JG From United States of America, joined Jun 2005, 0 posts, RR: 1
Reply 3, posted (13 years 2 months 2 weeks 3 days 21 hours ago) and read 972 times:
Additionally, derated thrust and assumed thrust are two different beasts. The CFM powered 737's I used to fly could do both derate and assumed (also called balanced thrust) individually or combined. The 320 series I fly now simply uses assumed temperature. On our 320's that assumed temperature can be as high as ISA + 53C