Exoderpyish
Topic Author
Posts: 2
Joined: Mon Mar 12, 2018 2:29 pm

### Relationship between Flex. Temp and N1

Hi all,

15 years back, there was a topic created on this subject. Apparently, the formula for calculating N1 based on the Flex Temp is

Reduced N1=Full N1 × square root of (ambient temp/Flex Temp).

*Both temperatures are to be expressed in Kelvin.

Can anyone here explain what "full N1" means? I have a feeling that it isn't simply "100".

Thanks!

whywhyzee
Posts: 686
Joined: Tue Jan 05, 2016 3:12 am

### Re: Relationship between Flex. Temp and N1

Not necessarily 100. When we talk about N2, we talk about the percentage of the ISA rated N1 (fan speed). Given the ambient conditions, that may be more or less than 100%. I am not certain if the baseline 100% N1 value takes into account the bleeds being open/closed. I know on the CRJ 100/200, under normal conditions, it will not hit 100%. Why in specific I don't have the actual answer. I assume it is due to the normal use of 10th stage bleed air for pressurization. Next time I'm in the sim, I'll give it a try unpressurized and 14th stage bleeds closed (wing/cowl anti ice bleed air source).

zeke
Posts: 12594
Joined: Thu Dec 14, 2006 1:42 pm

### Re: Relationship between Flex. Temp and N1

Exoderpyish wrote:
Hi all,

15 years back, there was a topic created on this subject. Apparently, the formula for calculating N1 based on the Flex Temp is

Reduced N1=Full N1 × square root of (ambient temp/Flex Temp).

*Both temperatures are to be expressed in Kelvin.

Can anyone here explain what "full N1" means? I have a feeling that it isn't simply "100".

Thanks!

What aircraft what engine ?
Human rights lawyers are "ambulance chasers of the very worst kind.'" - Sky News

Exoderpyish
Topic Author
Posts: 2
Joined: Mon Mar 12, 2018 2:29 pm

### Re: Relationship between Flex. Temp and N1

What aircraft what engine?

CFM56-5B1-2 on the A321

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