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Old 02-08-2019, 08:34 AM
  #21  
Adlerdriver
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Joined APC: Jul 2007
Position: 767 Captain
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Originally Posted by MysteriousMrX View Post
again, I think I’m overthinking it and confusing myself! But thanks for the responses.
The max weight may indeed be something to do with the runway but it was DFW and all runways are very long.

But on ACARS landing data, surely everyone gets the same info: which includes the unfactored length and the longer 60% factored length.
First, the fact that DFWs runways are "very long" doesn't automatically mean your MTOGW for takeoff on a particular runway, on a particular day is going to be the max certified weight for your aircraft. Factors such as winds, temperature, assumed/flex temps, 10/20 % derated thrust for some aircraft, obstacles, flap settings, etc. may not allow takeoff at max certified weight.

Second, each airline has specific methods they use to compute performance. Mine doesn't use ACARs. We use a program incorporated into our EFB and compute all the data ourselves, both for takeoff and landing. My previous aircraft at the same company used quick reference data in the QRH for landing distance.

Third, information received from whatever source(s) an airline uses may be presented very differently. Assuming we all can decipher the end product you receive and help you with your questions is a big assumption. Along those same lines, your assumption that "everyone" gets the same information when computing landing distance isn't valid. On my a/c, we input landing weight, ATIS information and runway condition, max or idle reverse, MELs/CDLs. The output is landing distance for each autobrake setting and XW/TW components. We don't get unfactored blah blah.... 60% factored whatever and start doing math. It's one number for a particular set of conditions and autobrake setting.

I think the recommendations that you contact your training/standards department are a good start. Having a solid working knowledge of the performance information provided to you by whatever method you use is pretty important when you start getting close to the edges of the envelope dealing with windshear precautions, cluttered takeoffs, runway shortening and obviously landing under less than optimal conditions.
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