Question about altitude and step climb based on weight

Hello everyone,

I often check FR24, and I’ve noticed that on ultra-long-haul flights, aircraft start at lower altitudes. For example, on KJFK-NZAA flights, I’ve observed that planes typically cruise at 30,000 feet initially. Later, as fuel burns and weight decreases, they climb to higher altitudes.My question is: How do we calculate the appropriate cruising altitude based on the aircraft’s weight? For instance, starting at 30,000 feet, how much weight needs to be reduced, or how much fuel needs to be burned, before climbing to a higher altitude? Is there a specific mathematical formula or method for this?
I’d love to hear insights from experienced pilots or anyone familiar with this topic.
Thanks in advance

I have tested and compiled values for every relevant aircraft in the game.

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Hi,I’ve reviewed the aircraft performance data you shared, and it’s really helpful. The results of your tests are detailed and comprehensive, and I’m sure this will be very useful for flight planning. If you plan to add more data or conduct further tests in the future, it would be great if you could share them as well.Great work and thank you for sharing

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There’s some more in-depth stuff on my profile. I generally take a look at every new plane that comes out.

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use simbrief to generate a flightplan and stepclimbs

I’ve always done step climbs by watching:

  1. that the AoA (angle of attack) stays within reasonable limits (from the pitch angle in level flight; or in a climb, the angle between the FPV and the nose mark).
  2. that I can sustain a minimal reasonable climb rate, with no loss of IAS, for a given climb power setting.

If I can’t satisfy the above, I level off until fuel weight is burned and I can meet those criteria.

This procedure is not absolutely precise for maximizing the last bit of fuel burn, but:

  1. It works for all aircraft.
  2. It’s close enough to get results.
  3. It’s based on the actual theory of the physics of flight that affect flight management systems’ step climb profiling.

This method seems very logical and based on real-world flight physics. Especially considering AoA and a sustainable climb rate makes it more applicable to all aircraft. It might not be fully optimized for maximum fuel efficiency, but it appears to be a very effective and practical solution. That said, I was wondering if there’s any tool or program for iOS that can automate step climbs? Sometimes I fall asleep during the flight and miss the right time to climb.

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A good question. I’ll leave that to other people who have more knowledge of that than me.

For iOS, you can use In-Flight Assistant. But mind this, IF Assistant would make you climb from point A to point B. So, even if the two points are 1000 NM away, you will start climbing at point A at the lowest climb rate, that is, 100 fpm. For every 1000ft difference in altitude, I would set another waypoint A 7.5-10 nm before the climbing-waypoint B so that I will climb at a rate of 800-1000 fpm. Not too steep but not too gentle either. If you’re too steep, there is a possibility that you lose speed in the process. If your climb slope is too gentle, you’d be fine in the simulator but not in real life, since there is a possibility that ice might accumulate in the engine, causing low thrust when it needs to be at high thrust (look at British Airways flight 38).