Lower fuel Consumption at Higher altitudes

People always say fly higher to save fuel but what I noticed is sometimes say on a 13 hrs long haul. If you keep flying at the same altitude instead the fuel flow will get lesser as u cruise along due to weight bring burnt off but as I step climb the fuel flow shoots up again shouldn’t it be lesser instead of more? I do step climbs 4 to 5 hrs into the flight so I don’t think I am climbing too early becuz that’s what a real planes does as well based on what I see on flightaware track log. So my question is, is it there’s some inaccuracy on the fuel flow or something else?


The aircraft starts to loose it’s weight the longer you fly requiring less power which lowers the fuel flow :) Step climbing lowers your speed as well, like if I had myself at M0.84, the higher I climb, the less speed I go requiring less power.

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Yeah the GS does decrease as you go higher due to colder air. But then the fuel flow shooting up instead of going down is something I find really weird becuz IRL it should be going down instead.

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It shoots up because the aircraft requires more power to maintain a certain speed that you have selected for A/P :)

The key thing is: Don’t step climb too frequently, like only do it every few hours or so. It really depends on your weight and the length of your flight. Make it very gradual too, don’t increase altitudes too fast, even doing +1000 fpm is way too high. Make it around 500 at the most so you don’t use too much power during your step climbs.

I usually do it every 4 to 5 hrs so on a 12 hrs flight I’ll probably do 2 step climbs only. I mean not the climb phase but the cruise phase which means say after I’ve step climbed from 360 to 380 and the fuel flow at 380 is noticeably higher.

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With that being said, I wonder isn’t it more efficient to just maintain the same altitude all the way instead of climbing further as the fuel flow will gets lower anyway as u fly further

What is your throttle at usually when you do these? It might get too high leading to more fuel flow. Make sure to put in enough fuel for each long haul too.

Usually around 83 to 85 percent throttle N1

Hmm… Not bad. Maybe it might be your block fuel that’s the problem. How much fuel do you put in before, say… a 12 hour flight?

I put in based on what simbrief gives me so should be alright and I step climb following the altitudes simbrief gave as well. If say a A359 I’ll put in 70k tons of fuel block

Actually at each fuel level, there is an optimal flight level. It is not true that the service ceiling is always optimal, and even less in IF. For example, the A350 is most efficient at FL340 or below (irl you barely ever see one that low).

I guessed so too. IRL planes consume a lot more fuel at the beginning stage of their flight as well for the A350 it’s around 7k to 9k an hour at low altitudes rather than 5k in IF so I can say the fuel flow is inaccurate in IF. Becuz what I discovered is that the fuel tends to land with a lot of extra fuel on board compared to the Estimated given on simbrief whereas in RL its probably extra 1 to 2 ton only in IF I land with 10 tons more fuel

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