Altitude Adjustments

[cmpbellsjc 2,963]

you enjoy going into the needy greedy.

Lol, I think you meant nitty gritty.

 

By I agree, Vernon likes to go above and beyond the most minute detail of flying desk top sims.

[ALF1 15]

Correct, that is my fun say....might as well LOL !!!

[JRBarrett 3,197]

Lol, I think you meant nitty gritty.

 

By I agree, Vernon likes to go above and beyond the most minute detail of flying desk top sims.

Nothing wrong with wanting to understand the nuts and bolts theory underlying how aircraft and their systems fly and operate. Vernon definitely has a passion for detail.

 

There is always the danger of getting in so deep that one can lose sight of the big picture, but being an analytical sort of person, I can empathize with his desire to understand.

[ALF1 15]

That is why I think he would enjoy the course.

[Driver170 42]

Don't know what to say...

 

Respect to those comments! I do however, can get too into too much detail of my topic and get carried away. But as JRBArrett says i do go into detail which i know i'm bad for but if i want to learn something i mean i want to learn it all. Sure a PPL will be great but its alot of money and time! My maths ain't great so i lack at that subject. But my focus now is to build a fully own 737NG with FDS which i have already began and thats enough for me

[Driver170 42]

One more thing - If you see a performance chart and it says ISA + 10c and below. Does that mean ISA at that altitude or ISA DEV?

[ALF1 15]

Vernon, ISA temperature is different at different altitudes. At sealevel it is 15 celcius or 59 Farenheit. Then the lapse rate I think is 2 C per thousand feet, so at 10,000 ft you'd have -5 C as ISA. So that denomination is for ISA deviation most definitely, and would indicate warmer air than standard for any altitude if it is at +10. Less performance than a minus figure.

[Driver170 42]

Yeh thats correct but i was just asking what ISA + 10 and below, was referring to? ISA DEV or ISA at that altitude ie 10000ft is -5C

[ALF1 15]

An altitude. ISA in this instance is 15c+ 10 is 25C, so I believe that would be 5,000 ft and below. Is that all it says ? Are you sure ?

 

Cause that number says 25C at sealevel. The "below" without anything else in the formula still leaves an unknown altitude. What you care about is the 5,000 feet because of the warmer conditions.

[Driver170 42]

It says

 

Long Range Cruise Maximum Operating Altitude Max Cruise Thrust

ISA + 10°C and Below

You'll find it the 737 FCOM PI

[ALF1 15]

Ah ok, then that sounds like a thrust rating for that max altitude. I am not a jet expert. I have read that these engines are pretty much rated for max thrust at ISA+15 which is 30C at sea level. You would probably then be talking about a reduced thrust rating for max long range cruise. Translated into N1 fan speed...... I dont know good question, I would like to see that chart

[Driver170 42]

So ISA + 10c would depend on OAT and altitude? So it seems that it means ISA at that altitude and not ISA DEV.

[ALF1 15]

You got me going here with your "nitty gritty" and I found some good reading for you. Your question is not about performance as you explained, it is about an engine thrust rating for the ngx engines.

 

http://www.b737.org.uk/assumedtemp.htm#Some_Facts_About_Assumed_Temperature_Thrust_Reduction

 

I am not at my sim nor my FCOM only my mobile device and away, but I am sure you will get a lot of answers there. I will read it also.

ISA+10 means 10 degrees celcius warmer than standard at any altitude dont try to make more of it. 10 degrees warmer is like a 5,000 ft altitude penalty on performance. High, Hot, and Humid....the three enemies on performance.

[Driver170 42]

Cheers for looking into but its not actually anything specific but rather what ISA + 10c means!

 

So would that mean its meaning ISA DEV? + 10

[ALF1 15]

Short answer and taking into account the thrust rating thing which could be at any altitude : YES

 

Sea Level: ISA+10= 25C

10,000 ft: ISA+10=5C

30,000 ft: ISA+10= -35C