Primarily for general aviation discussion, but other aviation topics are also welcome.
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By lobstaboy
#1801764
Miscellaneous wrote:Never for a second did I think airliners always used full power. :?


Well then, oh fount of wisdom, why don't they?
(And of course we should be talking about thrust, not power, but never mind)
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By Miscellaneous
#1801766
lobstaboy wrote:
Miscellaneous wrote:Never for a second did I think airliners always used full power. :?


Well then, oh fount of wisdom, why don't they?

Let me treat that with the contempt it deserves and simpy say, I'm surpsied you did. :wink:
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By lobstaboy
#1801770
Miscellaneous wrote:
lobstaboy wrote:
Miscellaneous wrote:Never for a second did I think airliners always used full power. :?


Well then, oh fount of wisdom, why don't they?

Let me treat that with the contempt it deserves and simpy say, I'm surpsied you did. :wink:


Ah. So you don't know then?
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By Paul_Sengupta
#1801779
To answer the question, noise, fuel burn and engine stress/wear.

https://eu.usatoday.com/story/travel/columnist/cox/2013/03/25/ask-the-captain-do-jets-use-full-power-on-takeoff/2012995/
https://www.faa.gov/documentLibrary/media/Advisory_Circular/AC25-13.pdf
https://flightsafety.org/asw-article/when-less-is-more/

I was once on a DC10 coming back from Florida which had no seating plan. The cabin crew seated everyone starting at the front row and working backwards. However the aeroplane was only about 2/5 full, which meant everyone at the front and no one further back. The pilot made an announcement asking if everyone could please spread themselves around the cabin otherwise they'd never get the nose up on take-off!
Last edited by Paul_Sengupta on Sat Oct 10, 2020 10:39 am, edited 1 time in total.
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By Paul_Sengupta
#1801786
The only time I don't use full throttle in t'dog for take-off is as lead in a formation take-off, when you have to back it off a bit to allow leeway for the other aeroplane(s) to be able to keep formation. As non-lead, you're likely to be using less as well in that case!
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By JAFO
#1801806
I was once booked into row 3 on a flight from LCY to IOM. Just before boarding a young lady approached me and asked if I would mind moving to the back. Fine by me.

When we got on board I noticed that my former seat was not empty as I'd expected it to be but had someone sat in it. Why they didn't just say: "Oi, fatty, get to the back or we're never getting off." I don't know. They then offered me a breakfast and looked oddly at me when I pointed out that they weren't helping.
By As I CFIT
#1801807
Nothing to do with noise or fuel savings. In fact, reduced thrust take-offs and climbs actually increase total fuel burn to 'top of climb'.

The only reason this is routinely done is to reduce engine wear and tear, to therefore maximise 'life on wing' (engine longevity).

Minimising wear and tear means the pursuit of increased EGT margins. Essentially, the greater the margin between actual and maximum permissible EGT with take-off thrust set, the more economical the operation from a maintenance perspective. This is especially important, we are told, for the first flight of the day when the EGT margin is typically reduced.
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By matthew_w100
#1801932
I have become an expert on this by watching three YouTube videos. But what I can't understand is why the power reduction is accomplished by lying to the computer that the OAT is something preposterous like 60C, instead of there being a proper "use only 80% power" button you can press. Is there a reason?
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By OhNoCB
#1801934
I suppose it is a bit of a hangover from days gone by whenever it was just becoming a concept and the temperature was a way to achieve it. It also depends on type too.

On the commercial type I fly you can select one of three thrust settings for take off, so pretty close to what you are suggesting. We can however then enter a temperature on top of that for further flexibility.

One other difference again on my type, is that using the fixed de rate method (ie. choosing one of the three power thrust settings) affects VMCG and VMCA, whereas the assumed temperature method does not. This can be important on narrow runways.
By Maxthelion
#1802052
Paul_Sengupta wrote:The only time I don't use full throttle in t'dog for take-off is as lead in a formation take-off, when you have to back it off a bit to allow leeway for the other aeroplane(s) to be able to keep formation. As non-lead, you're likely to be using less as well in that case!


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