Jump to content

Sign in to follow this  
Guest iflyc77

How to set de-rates?

Recommended Posts

Guest iflyc77

Ok, I know "how" to "set" a temperature or 1/2 in the FMC, but how do I know which one to use? Is there some standard convention to go by?I read the manual and all I could get was the circumstances in which I could NOT use a derate.All I know is that if the runway is about 10,000 feet long, use 54 degrees... any thing else and it is all blind, using either no derate or D/1 or D/2 takeoffs.So some insight on what these numbers mean and which ones to use would be much appreciated!

Share this post

Link to post

The temperature depends on a number of things including:Runway lengthAirfield elevationAmbient TemperatureAircraft WeightTakeoff configuration (eg. Flap setting)Basically what it's for is setting a de-rate specific to the conditions for that particular takeoff. Simply put, it's a temperature that will limit the thrust of the engine to a point that is just enough to get the aircraft airborne by a certain point on the runway.ex. Runway length is 10,000ft. You want a 'margin' (amount of runway remaining at lift off) of 2000ft. You can set the engine to give you enough thrust to get you to your VR in 8000ft.I actually use a freeware program called TOPCAT for every B744 flight. http://topcat.ofplan.net/It hasn't been updated in a long while but it's still usable. It will provide several temperatures to choose from giving you different margin's. You can also choose items like what flap setting you'll use, whether you will use anti-ice, and how many packs, if any, you intend to use on takeoff. You will also have flap speeds for both climb out and approach as well as auto-brake stopping distances for landing.There isn't any support for the program. (Don't bother with the forum. It doesn't contain anything related to aviation and anything appropriate for under 18 years old.) There is a manual available but I just learned to use it the same way I usually learn things; see what all the buttons do. (Unless something goes really wrong, then I turn to the manual.) I'd be happy to help with anything I can.As far as I can tell, the site's abandoned. Sad really, this would be so useful on so many other aircraft. Maybe PMDG could include a takeoff calculator like this with future aircraft?Ryan GamurotLucky to live Hawai'ihttp://www.virtualpilots.org/signatures/vpa296.png

Ryan Gamurot

Share this post

Link to post

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this  
  • Tom Allensworth,
    Founder of AVSIM Online

  • Flight Simulation's Premier Resource!

    AVSIM is a free service to the flight simulation community. AVSIM is staffed completely by volunteers and all funds donated to AVSIM go directly back to supporting the community. Your donation here helps to pay our bandwidth costs, emergency funding, and other general costs that crop up from time to time. Thank you for your support!

    Click here for more information and to see all donations year to date.
  • Donation Goals

    AVSIM's 2020 Fundraising Goal

    Donate to our annual general fundraising goal. This donation keeps our doors open and providing you service 24 x 7 x 365. Your donation here helps to pay our bandwidth costs, emergency funding, and other general costs that crop up from time to time. We reset this goal every new year for the following year's goal.

    $640.00 of $25,000.00 Donate Now
  • Create New...