Jump to content
Forum Rules and Expectations (UPDATED)

How to calculate the FLEX TEMP? (Tutorial)

Monty43

By Monty43
in General Discussions

 Share

Recommended Posts

  • Popular Post
Monty43 Rookie

Monty43

Posted
  • Popular Post
Posted (edited)

Hello friends, 

First of all thanks to the development team for this  amazing aircraft. My name is Jose Antonio Montiel from Málaga I am 24 years old, I am aircraft mechanic in the real life and I have worked a few in the B717-200, at present I work in the B737. I would like to share my little knowledge with you.

In the B717 there are two types of reduced thrust:

* Limit thrust: is a % lower of thrust for the total thrust in the current OAT or FLEX/Assume Temperature. TO1 -10% TO2 -20% .

*FLEX TEMP: is a temperature that we put in the FMS so that the FADEC misleads the engine to assume more temperature than it actually is and thus obtain a lower thrust.

Ok, how do we calculate our FLEX TEMP for current conditions?

We have:

* T/O Weight 53.000 Kgs

* Airport Elevation 1.000ft

* RWY Lenght 2.200 Meters and dry

* Winds 10 HW

* Slope 0%

* OAT 20ºC

* Flaps configuration 13º

* Type Engine BR700-715C1-30

So that we can know our FLEX TEMP we have to calculate our maximum temperature that we can assume with our take off weight, how? Ok we go to de FCOM performance dispach and choose the table for our conditions:

The first step is RWY Lenght corrections:

Spoiler

1.jpg.c19c07662b585b1c168410d1cb9ceb7a.jpg

Is 2.290 Meters.

And second stet calculate our Max FLEX TEMP with T/O Weight 53.000 kgs

Spoiler

2.thumb.jpg.b557700844507030e9c34dc8780ee933.jpg

FLEX TEMP is 40ºC, 45ºC It could not be because the Maximum take off weight(performance, not structural) is less than we have 51.300 kgs and the same for Climb Limit weight (performance).

 

Regards
 

Edited by Monty43
  • Like 9
  • Thanks 2
Link to comment
Share on other sites
  • 2 weeks later...
Monty43 Rookie

Monty43

Posted
  • Author
Posted
On 29/8/2017 at 10:06 AM, raunzos said:

Thanks for the tutorial!

However, where can one acquire the performance tables illustrated in your post? The TFDi does not seem to include these.

Hello raunzos,

The table are from Flight Crew Operation Manual (Performance chapter) is real documentation. You can get here http://www.mycockpit.org/forums/downloads.php?do=cat&id=6&page=3

Regards.

Link to comment
Share on other sites
  • 7 months later...
  • 1 month later...
  • 2 weeks later...
imemyself Rookie

imemyself

Posted
Posted

I've been using and enjoying that flex calculator since early this year - unfortunately, I now see this message on the 717 one:

This webpage will be terminated shortly. If you need the data in excel format, contact me on the email address at bottom of the page!

Link to comment
Share on other sites
hbrammer New Member

hbrammer

Posted
Posted

the website is not accepting new registrations-a recaptcha issue.Can anyone send me all the pertinant tables as I am unable to access them/I notice runway length stops at 3600 meters-if you have a much longer runway such as KDFW,do the actual tables reflect longer lengths or do you use the 3600 figure for anything over that?thanks

Link to comment
Share on other sites
Monty43 Rookie

Monty43

Posted
  • Author
Posted
On 6/25/2018 at 4:06 AM, hbrammer said:

the website is not accepting new registrations-a recaptcha issue.Can anyone send me all the pertinant tables as I am unable to access them/I notice runway length stops at 3600 meters-if you have a much longer runway such as KDFW,do the actual tables reflect longer lengths or do you use the 3600 figure for anything over that?thanks

Manufacturer's manual has until 3600 meters only because this manuals are generic and the manufacturer considers this minimum distance for maximum reduced thrust and weight of the aircraft, in real life each operator of aircraft has its own tables for each airport that they operate. But if you have 4500 meters of runway you can do the calculations with 3600 meters, is valid.

Regards.

Link to comment
Share on other sites
  • 2 weeks later...
  • 1 month later...
  • 3 months later...
Monty43 Rookie

Monty43

Posted
  • Author
Posted (edited)
On 1/2/2019 at 7:47 PM, Chris Smith said:

Is it possible to combine a flex temp with an engine derate? Or is it to choose one or the other? You explained the flex temp very well - can you also elaborate on the use of derate?

Thanks,

Chris

Hello Chris,

Sorry for the delay, I worked out of my country for a time. I am going to try explain below:

The law dictates that takeoff thrust may only be reduced by a maximum of 25% from nominal maximum thrust. Therefore, if you thrust limit the engine by 10% or 20% upon 100% (nominal thrust) you obtain 90% or 80% as nominal thrust, you can then apply a further 25% reduction upon this thrust limit with an assumed temperature/FLEX TEMP, in others word upon 90% or 80% you can reduce others 25% in total will be a maximun of -35% or -45% thrust reduction. It is a small trap to comply with the law and to extend the life of the engines even more.

How to calculate? simple the aircraft operator chooses the thrust limit in according with the same tables above but calculated for a thrust limit of 10% or 20%. I don't have this tables, I have only the generics and it's 100% thrust.

Regards.

 

Edited by Monty43
Link to comment
Share on other sites
  • 1 year later...
  • 8 months later...
  • 2 weeks later...
  • 1 month later...
Akai Umi New Member

Akai Umi

Posted
Posted

OK, I was dump to not noticed the table is in the "Airtran Airways Aircraft Operations Manual" in TFDi's Download section

The index makes me think it's only PI, but there is PD on the button. it's just poorly bookmarked...

Be noticed there are 8 chapter, both PD and PI for imperia and metric and for 715A1 and 715C1 engine, pick the correct one for you.

 

I might make a data set for QSimplanner, if I have time, although it's wind download is broken, the TO/LD calculator still works fine then.

Link to comment
Share on other sites
  • 2 weeks later...

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
 Share
Go to topic listing
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.

  I accept