Buff From Australia, joined Mar 2007, 0 posts, RR: 1
Reply 1, posted (14 years 7 months 1 week 2 days 5 hours ago) and read 993 times:
I believe the FAR's/CAR's/CAA etc specify minimum derates. Our company 757's (RB211) use data supplied by Jeppesen and for the most part, the highest assumed temperature allowed is in the 60-62C range. The maximum assumed tends to decrease with ambient temperatures lower than 20C.
CX flyboy From Hong Kong, joined Dec 1999, 6693 posts, RR: 55
Reply 2, posted (14 years 7 months 1 week 2 days ago) and read 963 times:
We can use 60 degrees as well in Cathay on the 747-400.
The Hong Kong Civil Aviation Department restricts derates to not more than 25% of fully rated thrust. This is why airlines, including ours quite often has engines derated in the certification process (Done by altering the computer programming in the aircraft), so that we can have a bigger derate, and in the long run save money.