PPRuNe Forums - View Single Post - Purpose of Semi-Fixed De-rates (TO1, To2)
Old 31st December 2010 | 11:42
  #23 (permalink)  
Denti
 
Joined: Mar 2001
Posts: 4,563
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From: I wouldn't know.
Why even use printed stuff? Performance software does a very good job to test all possible combinations in a few seconds, and boeing gives it out on new planes anyway.

Besides, using a derate has its use during winter operation, and of course it allows less thrust used than using only ATM as ATM is restricted currently, whereas the combination of ATM and derate allows to work around that restriction without any special approval.

We used to have 27/24/22 on the 800s and nowadays use 26/24/22 or 22/20/18.5 on the -800 and -700 respectively. Full thrust is only needed for very few occasion, for example out of LPA with full passenger load, full baggage, a ton of cargo and 16 tons of fuel, which requires the SFP version additionally to full thrust sometimes. Most take offs are done using the lowest thrust setting available and depending on load with up to 60° ATM, usually flaps 1 as well.
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