Just asking about N1%

N1 is a calculation of the engine’s fan speed which is expressed as a percentage (what we see). Think of it as the RPM you see in piston engines.

I’m not sure if we as pilots can “calculate” N1 as it’s just a number calibrated by the engine manufacturer, we can only interpret it.


You can manually calculate and use charts like this to figure out flex N1 and temperature.
Though practically it’s now integrated into the FMS on modern aircraft, you just put in the numbers and it calculates for you.



btw, i found this website: Performance Calculation for AIRBUS , obviously, i’m not sure is this website is accurate - or even safe to visit as a matter of fact. i reckon tht when opening the site, take precautions.

This in a very interesting question. And I spent some time actually with chatGPT asking maybe as many as ten questions, without getting an answer that I thought was truly insightful.

I finally had to stop with frustration over the following exchange:

My question:
"Doesn’t what you just said violate the principle of conservation of mass?: "In a turbofan engine, the mass flow rate of air in is not equal to the mass flow rate of air out. "

ChatGPT’s last paragraph:
“I apologize for any confusion caused by my previous response, and I appreciate you pointing out the error. The principle of conservation of mass indeed holds in a turbofan engine, with the mass flow rate of air in being equal to the mass flow rate of air out.”

How can one have trust in what one reads after this?

But anyway, I was trying to get a better handle on a simple explanation tying together how N1 relates to the issues of fuel flow efficiency, engine reliability, and engine thrust physics, and the FMS, given changes in operating conditions like temperature and air density.

Not successful, but the complexity facing what the engine manufacturer gives to the end user became more apparent.

1 Like

I wouldn’t be worried about it. You probably just got a message from your browser saying it was http not the newer https. (Difference between http and https)

I tossed the url through virustotal, and it flagged nothing


This 👆

We have graphs and tables, but there isn’t an equation to figure out a specific power setting


The reason N1 settings can’t be reduced to a straightforward calculation is because the setting procedures have to balance considerations for safety margins, engine limitations, and fuel efficiency. A complex mix of factors.

And establishing the procedures is a mix of significant efforts:

"N1 setting procedures result from a combination of rigorous testing, theoretical considerations, regulatory requirements, and operational feedback. "


Is this a general diagram or to a specific aircraft?

It’s for the A320.

… wait, I don’t fly the -200, i fly the -700 🫥🧐

Then how about a generic stab at an answer - are the numbers below reasonable or not?: (chat again)

"Since you’re specifically looking for N1 numerical settings for different flight phases in a recreational flight simulator, I can provide you with some general guidelines that will give you a sense of adhering to the key ideas of setting N1 in a real aircraft. Please keep in mind that these are approximate values and can vary depending on the specific aircraft model. It’s always recommended to consult the aircraft’s documentation for accurate N1 settings.

  1. Startup and Taxi Phase:
  • During startup, set the N1 to idle or a low value (around 20-30%) to ensure the engines are running smoothly without generating excessive thrust.
  • While taxiing, keep the N1 at idle or a slightly higher value (around 40-50%) to provide sufficient power for maneuvering on the ground without accelerating too rapidly.
  1. Takeoff Phase:
  • Before takeoff, advance the thrust levers to the takeoff power setting, commonly referred to as flex or TOGA (Takeoff/Go-around) power. This setting varies depending on factors such as aircraft weight, runway length, and environmental conditions.
  • Typically, N1 values for takeoff power range from 85% to 95%, but again, the exact values can differ between aircraft models.
  1. Climb Phase:
  • Once airborne, reduce the thrust to climb power, which is a lower power setting than takeoff power.
  • The N1 setting for climb power can vary but is generally around 70-85% of maximum N1.
  1. Cruise Phase:
  • In the cruise phase, the N1 setting depends on the desired cruise speed and altitude, as well as aircraft weight and environmental conditions.
  • Generally, N1 values for cruise power range from 70% to 85% of maximum N1.
  1. Descent Phase:
  • During descent, you can reduce the N1 gradually to maintain a controlled descent rate while maintaining airspeed.
  • The N1 setting in the descent phase varies depending on factors such as aircraft configuration, desired rate of descent, and air traffic control instructions.
  1. Approach and Landing Phase:
  • In the approach phase, reduce the N1 to a level that allows for a stable descent while maintaining the desired approach speed.
  • The specific N1 setting for approach varies based on factors such as aircraft configuration, weight, and desired approach speed.

It’s important to note that these values are approximate and can differ between different aircraft models and manufacturers. Moreover, modern commercial aircraft often employ automated systems like autothrottle, which manage N1 settings based on flight phase and desired parameters. For a more realistic experience, consult the documentation or guides specific to the flight simulator software you are using, as they may provide more accurate N1 settings for different aircraft models."

1 Like

Check this out!
All Aircraft Takeoff and Landing Profiles

btw, i had seen this

Perhaps you saw something similar based on agreeing recommendations. But I only generated that just over half an hour ago.

In all honesty, the method I use myself is to interpolate and estimate what seems like reasonable values (unless I’m just doing a carefree flight and therefore using full throttle wherever I’m able).

To accommodate the conditions of weight, altitude, temperature, for different aircraft for both runway length, altitude transition and cruise, while roughly limiting N1 to less than full (for some realism of that aspect), I try to balance (with admittedly some estimation and guess work) tradeoffs in safe “values” for:

ability to adequately accelerate, safe AoA range, ability to maintain altitude and speed, and maybe noting throttle in reserve (when am I maxed out or not).

I look at actual max numbers for specific aircraft occasionally and take rough note of max cruise speeds and N1 settings and incorporate that into the above (as I remember them).

This would not work when employed by an airline irl! But from an engineering background it satisfies the reality police inside me.

btw, i was telling @Duy

1 Like

Oh sorry! That makes more sense. I got the notice that you had replied to my post (I must have mistaken it). Thank you for clarifying. As for my answer then, ever mind:)

Yes, this. Agreed!

btw, as for more background info on realism:

In the “FAA’s Transition to Jet-Powered, Airplanes,”
Airplane Flying Handbook (FAA-H-8083-3B) Chapter 15

There’s a section starting on page 15-3 “Operating the Jet Engine.”

On page 15-4 of that, is “Setting Power,” where it talks about how thrust relates to throttle movement and N1.

1 Like

This topic was automatically closed 90 days after the last reply. New replies are no longer allowed.