Kit777 From United Kingdom, joined Oct 2009, 93 posts, RR: 0 Posted (3 years 6 months 3 weeks 4 days 10 hours ago) and read 3462 times:
I was reading about Laker Airways a while back and remember coming across some of their tactics on saving money. One of these being a "reduced thrust" take-off method they developed for their BAC 1-11s.
I was wondering what this method actually involved and if it is being used on newer planes today.
Tb727 From United States of America, joined Jun 2005, 1374 posts, RR: 4 Reply 2, posted (3 years 6 months 3 weeks 4 days 7 hours ago) and read 3395 times:
We do reduced thrust takeoffs any time you have the conditions to do them. It helps reduce wear and tear and keeps maintenance costs down. You have to do a max blast though under certain conditions and at least every 7 days I think it is at our company.
Tdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 81 Reply 4, posted (3 years 6 months 3 weeks 4 days 1 hour ago) and read 3299 times:
Quoting FlyingColours (Reply 1): Reduced thrust is very common now I believe and I think may be related to Flex thrust on the Airbus series, an engineer or pilot would be able to give a much better answer.
Flex is one of the ways of doing it. I'm not sure if it's actuall a derate or an assumed temperature method (or some combination) but all modern jets can do it. There's basically no reason not to, when the runway and conditions allow it.
Dispatchguy From United States of America, joined Jan 2006, 1185 posts, RR: 2 Reply 5, posted (3 years 6 months 3 weeks 3 days 15 hours ago) and read 3211 times:
FLEX temp is an Airbus ATM method. Airbus aircraft cant combine FLEX temps with a set %-age derate (at least in the A320, A330, and A340 ops manuals I have seen).
But yes, all aircraft have the ability, and pilots should (as long as all conditions and restrictions are met) perform a reduced power takeoff each time they are legal.
You actually burn slightly more fuel during a reduced power takeoff, because acceleration is slightly reduced, so it will take slightly more time to achieve a given speed, however, that slight increase in fuel burn is more than offset by the increase in "life" of the hot section of the turbines, and the decrease in the wear and tear in the hot section.
With new aircraft now, like the B737-800, a part of the service agreement between the engine manufacturer and air carrier is that the operator will meet certain targets with respect to use of reduced thrust; we called these "power by the hour" agreements.
Tdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 81 Reply 6, posted (3 years 6 months 3 weeks 3 days 3 hours ago) and read 3073 times:
Quoting Dispatchguy (Reply 5): With new aircraft now, like the B737-800, a part of the service agreement between the engine manufacturer and air carrier is that the operator will meet certain targets with respect to use of reduced thrust; we called these "power by the hour" agreements.
That's sometimes, but not always, true. Power-by-the-hour is between the engine OEM and the airline...the airframe OEM doesn't really care. You can get a 737-800 with or without power-by-the-hour.
Brains From United States of America, joined Nov 2001, 255 posts, RR: 0 Reply 8, posted (3 years 6 months 3 weeks 2 days 1 hour ago) and read 2912 times:
Unless MELs or weight/temp conditions make it not feasable/legal my airlines's crews nearly always use reduced thrust (flex) takeoffs. Reduces wear and tear on the engines...(money saver in the long run).
Jetlagged From United Kingdom, joined Jan 2005, 2452 posts, RR: 17 Reply 9, posted (3 years 6 months 3 weeks 1 day 3 hours ago) and read 2801 times:
Quoting FlyingColours (Reply 1): I think they began to take off with a lower power setting, I don't think the BAC1-11 had the ability to select reduced thrust so the throttle would be adjusted manually to a lower setting.
No automatic derate of course and no auto-throttle or FADEC to help either. Thrust setting was manual whether full or derated. Spey thrust was set by means of a thrust indicator which showed percentage thrust. There was a thrust index setting which was calculated according to ambient conditions. You dialed in the thrust index for the conditions into the thrust indicators, and opened the taps until 100% was indicated, giving you full rated thrust. For a derated thrust you would either need to have a different thrust index table to give you a lower thrust at 100%, or use the full thrust index and set less than 100%. I don't know which method Laker used, but I would guess a derated thrust index table would be a more accurate and consistent way of doing things.
Having said that, some 111s had EPR indicators rather than %Thrust indicators, in which case the problem is no different to setting a derate on a JT8D for example.
[Edited 2009-10-31 17:05:23 by jetlagged]
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