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Reduced Versus Full Takeoff Thrust  
User currently offlineaerotech777 From United States of America, joined Aug 2009, 67 posts, RR: 0
Posted (2 years 5 months 3 weeks 5 days 8 hours ago) and read 5467 times:

Hi,

How often (approximate percentage if possible) do you use assumed or derated takeoff thrust versus full takeoff thrust?

Feedback appreciated.

33 replies: All unread, showing first 25:
 
User currently offlinewilco737 From Greenland, joined Jun 2004, 8906 posts, RR: 76
Reply 1, posted (2 years 5 months 3 weeks 5 days 7 hours ago) and read 5450 times:
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Quoting aerotech777 (Thread starter):
How often (approximate percentage if possible) do you use assumed or derated takeoff thrust versus full takeoff thrust?

I am FO on 744 and I did almost 100 flights this year and only ONCE we had to use full take off thrust. Rest was all derated.
Same on the MD11 I flew before. Most of the times reduced, only once in a while full thrust.

wilco737
  



It it's not Boeing, I am not going.
User currently offlineXFSUgimpLB41X From United States of America, joined Aug 2000, 4183 posts, RR: 37
Reply 2, posted (2 years 5 months 3 weeks 5 days 6 hours ago) and read 5417 times:

I would say a good 90-95% of our takeoffs are reduced/FLEX thrust.


Chicks dig winglets.
User currently offlineBoeingGuy From United States of America, joined Dec 2010, 2882 posts, RR: 7
Reply 3, posted (2 years 5 months 3 weeks 5 days 6 hours ago) and read 5411 times:

Quoting XFSUgimpLB41X (Reply 2):
I would say a good 90-95% of our takeoffs are reduced/FLEX thrust.

FYI, just as an aside, Boeing calls it "Assumed Temperature Derate" what Airbus and McDonnell Douglas call/called "Flex Power". Some Boeing airplanes also have a Fixed Derate, which is usually 10% and 20%.

My understanding is also that some sort of takeoff derate is used about 99% of the time, except at certain high altitude or short runway airports like SNA.


User currently offlineKcrwflyer From United States of America, joined May 2004, 3762 posts, RR: 8
Reply 4, posted (2 years 5 months 3 weeks 5 days 6 hours ago) and read 5399 times:

Quoting BoeingGuy (Reply 3):
My understanding is also that some sort of takeoff derate is used about 99% of the time, except at certain high altitude or short runway airports like SNA.

I've heard that most aircraft even get out of SNA with a certain derate, and that PHX requires more thrust.


User currently offlineFlyMKG From United States of America, joined Jan 2005, 182 posts, RR: 1
Reply 5, posted (2 years 5 months 3 weeks 5 days 4 hours ago) and read 5346 times:

We use reduced thrust around 80% of the time on our 727 freighters.

FlyMKG



Essential Power, Operating Generator.
User currently offlineMir From United States of America, joined Jan 2004, 21098 posts, RR: 56
Reply 6, posted (2 years 5 months 3 weeks 5 days 2 hours ago) and read 5305 times:

We never do reduced thrust. Push the thrust levers to the takeoff detent, FADEC takes care of the rest.

-Mir



7 billion, one nation, imagination...it's a beautiful day
User currently offlineboeingfixer From Canada, joined Jul 2005, 525 posts, RR: 0
Reply 7, posted (2 years 5 months 3 weeks 5 days 1 hour ago) and read 5280 times:

Quoting Mir (Reply 6):
We never do reduced thrust. Push the thrust levers to the takeoff detent, FADEC takes care of the rest.

What aircraft might that be?

Cheers,

John



Cheers, John YYC
User currently offlineMir From United States of America, joined Jan 2004, 21098 posts, RR: 56
Reply 8, posted (2 years 5 months 3 weeks 4 days 23 hours ago) and read 5221 times:

Quoting boeingfixer (Reply 7):
What aircraft might that be?

CJ3. The FADEC sets the power so that the takeoff detent corresponds to max rated power (even if the engine is capable of doing more). If it's hot or high, then you might not be able to get max power, but you'll get whatever the engine is capable of (and the published numbers reflect this).

-Mir



7 billion, one nation, imagination...it's a beautiful day
User currently offlinesuprazachair From Northern Mariana Islands, joined Feb 2004, 634 posts, RR: 0
Reply 9, posted (2 years 5 months 3 weeks 4 days 22 hours ago) and read 5203 times:

Assuming the aircraft has no MEL restrictions, every takeoff except first flight of the day and 10kt+ tailwind takeoffs. This is on the Dash-8-Q200/300.

User currently offlineCosmicCruiser From United States of America, joined Feb 2005, 2254 posts, RR: 16
Reply 10, posted (2 years 5 months 3 weeks 4 days 21 hours ago) and read 5195 times:

We always use "flex" if it's available.

User currently offlinepilotpip From United States of America, joined Sep 2003, 3139 posts, RR: 11
Reply 11, posted (2 years 5 months 3 weeks 4 days 21 hours ago) and read 5183 times:

The only time we are required to do a max thrust takeoff is on a contaminated runway with braking action less than good. The only time we really see this is with snow/slush. I like to do them any time there is a windshear advisory or when I'm at HPN. Other than that we do what the ACARS tells us performance wise.

This is in the ERJ-170. I haven't done a max takeoff in weeks and probably do less than 20 a year.



DMI
User currently offlineBoeingGuy From United States of America, joined Dec 2010, 2882 posts, RR: 7
Reply 12, posted (2 years 5 months 3 weeks 4 days 19 hours ago) and read 5155 times:

Quoting suprazachair (Reply 9):
every takeoff except first flight of the day

What is the significant of the first flight of the day in regards to derated takeoffs?


User currently offlineMax Q From United States of America, joined May 2001, 4071 posts, RR: 19
Reply 13, posted (2 years 5 months 3 weeks 4 days 18 hours ago) and read 5128 times:

Quoting Mir (Reply 8):

CJ3. The FADEC sets the power so that the takeoff detent corresponds to max rated power (even if the engine is capable of doing more). If it's hot or high, then you might not be able to get max power, but you'll get whatever the engine is capable of (and the published numbers reflect this).

Seems quite unusual to push the engines that hard every take off and must increase maintenance costs significantly.



Never heard of any jet operator not taking advantage of the ability to routinely do reduced power take off's.



The best contribution to safety is a competent Pilot.
User currently offlinesaab2000 From Switzerland, joined Jun 2001, 1609 posts, RR: 11
Reply 14, posted (2 years 5 months 3 weeks 4 days 16 hours ago) and read 5094 times:

I would guess that we flex at my carrier 95%-98% of the time. I have used full thrust myself only a few times that I can remember in the past few months and both times were full airplanes and short runways. The engines will be up to 100º hotter on a full thrust take-off than on a flex thrust t/o, though 75º is probably more normal.


smrtrthnu
User currently offlinejetpilot From United States of America, joined May 1999, 3130 posts, RR: 29
Reply 15, posted (2 years 5 months 3 weeks 4 days 16 hours ago) and read 5089 times:

We use full thrust whenever,,,,,

Snow/slush/standing water is present on the runway
Anytime there is a tailwind
Crosswind over 12 knots
Anytime wing/engine anti ice is in use
When climb power is higher than reduced power
When there is an unbalanced field length
Anti-skid is INOP
Windshear is reported or suspected
Any EPR gauge INOP


User currently offlineMir From United States of America, joined Jan 2004, 21098 posts, RR: 56
Reply 16, posted (2 years 5 months 3 weeks 4 days 3 hours ago) and read 4912 times:

Quoting Max Q (Reply 13):
Seems quite unusual to push the engines that hard every take off and must increase maintenance costs significantly.

I don't disagree, but I just fly it the way I'm trained to fly it.

-Mir



7 billion, one nation, imagination...it's a beautiful day
User currently onlinetb727 From United States of America, joined Jun 2005, 1548 posts, RR: 8
Reply 17, posted (2 years 5 months 3 weeks 4 days 2 hours ago) and read 4891 times:

Quoting jetpilot (Reply 15):

We use full thrust whenever,,,,,

Snow/slush/standing water is present on the runway
Anytime there is a tailwind
Crosswind over 12 knots
Anytime wing/engine anti ice is in use
When climb power is higher than reduced power
When there is an unbalanced field length
Anti-skid is INOP
Windshear is reported or suspected
Any EPR gauge INOP

We also have to do a max blast in the past 7 days when we look at the logbook. I'd say 75-80% are reduced at my company.



Too lazy to work, too scared to steal!
User currently offlineaerotech777 From United States of America, joined Aug 2009, 67 posts, RR: 0
Reply 18, posted (2 years 5 months 3 weeks 2 days 8 hours ago) and read 4581 times:

Thank you for your feedback.

Do you use wing anti-ice during full takeoff thrust?

A reduced takeoff thrust may increase the airplane-to-ground noise level as result of a lower flight path. If certain airports have some noise restrictions, do you use reduced takeoff thrust or full takeoff thrust?

Feedback appreciated.


User currently onlinetb727 From United States of America, joined Jun 2005, 1548 posts, RR: 8
Reply 19, posted (2 years 5 months 3 weeks 2 days 5 hours ago) and read 4537 times:

Quoting aerotech777 (Reply 18):
Do you use wing anti-ice during full takeoff thrust?

No, in the planes I have flown we always waited until we were in the air, typically after gear retraction and/or when we started bringing up the flaps. Engine anti-ice yes.



Too lazy to work, too scared to steal!
User currently offlineMir From United States of America, joined Jan 2004, 21098 posts, RR: 56
Reply 20, posted (2 years 5 months 3 weeks 1 day 22 hours ago) and read 4474 times:

Quoting aerotech777 (Reply 18):
Do you use wing anti-ice during full takeoff thrust?

Not necessarily. It's entirely possible to do a full thrust takeoff when the weather is nice.

But if the wing anti-ice is on, we will definitely be using full thrust (well, we use it anyway like I said, but even if it were an option, I wouldn't even think about it in that scenario).

-Mir



7 billion, one nation, imagination...it's a beautiful day
User currently offlinesuprazachair From Northern Mariana Islands, joined Feb 2004, 634 posts, RR: 0
Reply 21, posted (2 years 5 months 2 weeks 5 days 1 hour ago) and read 4208 times:

Quoting BoeingGuy (Reply 12):
Quoting suprazachair (Reply 9):
every takeoff except first flight of the day

What is the significant of the first flight of the day in regards to derated takeoffs?

First flight of the day is going to have the highest chance for an engine failure, so you'll want normal takeoff power if that were to happen.


User currently offlineXFSUgimpLB41X From United States of America, joined Aug 2000, 4183 posts, RR: 37
Reply 22, posted (2 years 5 months 2 weeks 5 days 1 hour ago) and read 4201 times:

Quoting suprazachair (Reply 21):
First flight of the day is going to have the highest chance for an engine failure, so you'll want normal takeoff power if that were to happen.

You're increasing the chances of an engine failure by running it even harder first flight of the day...



Chicks dig winglets.
User currently offlineXFSUgimpLB41X From United States of America, joined Aug 2000, 4183 posts, RR: 37
Reply 23, posted (2 years 5 months 2 weeks 5 days 1 hour ago) and read 4200 times:

Quoting BoeingGuy (Reply 3):
FYI, just as an aside, Boeing calls it "Assumed Temperature Derate" what Airbus and McDonnell Douglas call/called "Flex Power". Some Boeing airplanes also have a Fixed Derate, which is usually 10% and 20%.

I was just trying to give a "cover all" term, as I've flown Bombardier, McDonnell Douglas, Boeing, and Airbus airliners.  

The 737NG had the fixed derate as well as assumed temp on top of that... all the other's I've flown had a temperature only derate.



Chicks dig winglets.
User currently offlineDashTrash From United States of America, joined Aug 2006, 1439 posts, RR: 2
Reply 24, posted (2 years 5 months 2 weeks 4 days 13 hours ago) and read 4090 times:

Quoting Max Q (Reply 13):
Seems quite unusual to push the engines that hard every take off and must increase maintenance costs significantly.

It might be a Citation thing. In the X we push it to the takeoff detent each time, which is the highest possible setting in the aircraft. The FADEC takes care of the rest. With us, you're usually in the 83-86% N1 range. I've heard it's due to rudder authority if you lose an engine.

I know the G200 guys do the same thing, but are spooling up close to 100%.


25 foxxray : Same thing on the Citation Mustang and Beech Premier...
26 Rara : One thing I've always wondered: the "assumed temperature derate", or flex thrust, basically means that the aircraft is given a "fake" outside temperat
27 BoeingGuy : Yeah, Fixed Takeoff derate is baseline on the 737, 747, 777 and 787. It's a priced option on the 757 and 767 so most of those models don't have it. A
28 Post contains images Fabo : What is that good for? Seems quite the contrary of what could be actually be beneficial for 777 - more fixed derates - as I understand that in case o
29 Mir : For what it's worth, the Challenger 300 works the same way - thrust levers to the TO detent (except that that's not as high as they go - there's a de
30 tdscanuck : Yes. As outside temperature goes up, all temperatures in the engine go up (all the temperature ratios say the same but the inlet temperature is incre
31 Post contains images Rara : Thanks to you both! Now I get it. I was always under the impression that high temperatures somehow prevented engines from packing the full force into
32 Mir : This isn't wrong - high temperatures (and the resulting thinner air) do make it more difficult for the engine to produce thrust. Thus the requirement
33 BoeingGuy : On Seattle Boeing airplanes, the autothrottle sets the actual thrust lever position lower for TO-1 or TO-2. So you could override it and command full
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